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Active phase of calcium oxide used as solid base catalyst for transesterification of soybean oil with refluxing methanol
Abstract
For developing a process of biodiesel production with environmental benignity, much interest has been focused on solid base catalysts such as calcium oxide for transesterification of vegetable oils with methanol. In this paper, the active phase of calcium oxide was investigated by characterizing the catalyst collected after achieving the conversion of edible soybean oil into its methyl ester at reflux of methanol in a glass batch reactor. Calcium oxide combined with the by-produced glycerol, so that calcium diglyceroxide was a major constituent of the collected catalyst. The absence of calcium methoxide was clear from the spectrum of solid-state 13C-NMR. The chemical change of calcium oxide was not observed, when the yield of FAME reached 30%. The collected catalyst was not as active as the fresh one (calcium oxide), but was reused without any deactivation. In order to identify the active phase of the collected catalyst, we prepared calcium diglyceroxide by immersion of calcium oxide with refluxing methanol in the presence of glycerol. Calcium diglyceroxide prepared as the reference sample was as active as the collected catalyst in the transesterification, and was tolerant to air-exposure.
... Moreover, alkaline earth metal oxides especially calcium oxide, CaO have attracted much attention due to their relatively high basic strength, low solubility in methanol and can be synthesized from cheap sources like limestone and calcium hydroxide (Zabeti et al., 2009). Kouzu et al. (2008) reported that CaO obtained from calcinations of pulverized limestone, CaCO3 at 900 °C for 1.5 h in the flow of helium gas exhibited substantial result in transesterification of refined soybean oil. The yield of FAME was 93% after 1 h reaction time at methanol reflux temperature and methanol to oil ratio 12:1. ...
... However, the yield of FAME dropped to 66% when waste cooking oil with FFA content 2.6 wt.% was used under the same reaction condition. It is obvious that the basic sites of CaO were poisoned by strong adsorption of FFAs on the surface of the catalyst (Kouzu et al., 2008). Consequently, a portion of the catalyst changed into calcium soap by reacting with the FFAs adsorbed, resulting in low recovery of catalyst. ...
... Gryglewicz (1999) stated in his paper that calcium oxide slightly dissolves in methanol while transesterification of sunflower oil was conducted with methanol in which a slight amount of calcium oxide was found to dissolve in the reaction product (Granados et al., 2007). Kouzu et al. (2008) further identified the soluble substance as calcium diglyceroxide in which CaO reacted with glycerol during transesterification of soybean oil with methanol. Thus, an extra purification step is needed such as ion-exchange resin to remove the soluble content in the biodiesel. ...
Biodiesel is a renewable, clean-burning, and biodegradable fuel which can be synthesized from readily available domestic and natural sources, such as edible, non-edible and waste cooking oils, which may serve as a substitute to petro-diesel. It is produced by catalytic transesterification of fats and oils. A number of researches has been devoted to discovering a benign catalyst, especially heterogeneous acid catalyst that could convert non-edible and waste cooking oils with high free fatty acid into biodiesel, in an attempt to reduce the cost of production. The cost of production of biodiesel is still far higher than that of conventional petro-diesel, owing to the cost of edible oil currently being used, processes involved, and cost of conventional heterogeneous catalysts employed. This study assessed the role of various catalysts; homogeneous, heterogenous and enzyme-catalyzed transesterification reactions, in terms of their advantages and disadvantages in biodiesel production in order to establish very promising catalysts. Some methods of heterogeneous acid catalysts were also highlighted. Amongst the common heterogeneous catalyst, carbon-based solid acid catalysts were recommended as very promising solid acid catalyst that can utilize the non-edible oils in biodiesel production. The advantages of carbon-based solid acid catalysts include cheap readily available raw materials for their synthesis, easier production processes, relative stability, high reusability and potential for utilizing waste and non-edible oils for biodiesel production. Nnaji, J. C. | Department of Chemistry, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria
... Another common deactivation route is through the formation of Calcium hydroxide and calcium diglyceride. The XRD patterns in Fig. 5e-f(i-vi) illustrate the transformation of CaO into Ca(OH)₂ and eventually Calcium diglyceroxide during transesterification, which leads to catalyst deactivation (Kouzu et al., 2008). Peaks corresponding to Ca(OH)₂ appear in the early stages, but as the reaction progresses, Calcium diglyceroxide becomes the dominant phase, limiting active sites for further biodiesel production. ...
... HRSEM images of the catalyst in (a) fresh, (b) degenerated, and (c) regenerated states after nine biodiesel production cycles. (d) XRD patterns corresponding to (i) fresh, (ii) degenerated, and (iii) regenerated catalyst states(Ajala et al., 2022), (e-f) XRD patterns of the catalyst used for transesterification of soybean oil with methanol (i) Calcium oxide as the fresh catalyst; (ii) catalyst withdrawn in the middle of reaction, 0.25 h of reaction time; (iii) catalyst collected after achieving conversion of soybean oil into FAME, 2.0 h of reaction time; (iv) catalyst reused three times for the transesterification; (v) calcium diglyceroxide prepared by immersion of calcium oxide at reflux of methanol in the presence of glycerol; (vi) calcium methoxide prepared by immersion of calcium oxide with only refluxing methanol(Kouzu et al., 2008). (With permission from Elsevier BV.) ...
This review explores the use of waste-derived calcium oxide (CaO) catalysts in biodiesel production, highlighting their potential as sustainable and cost-effective alternatives to conventional catalysts. Unlike prior studies that broadly address catalysis, this work focuses on enhancing biodiesel yield and quality by identifying optimal strategies for CaO catalyst performance. Key elements addressed include: (i) customizing CaO catalysts for diverse feedstocks to enhance resistance to leaching and deactivation, (ii) mitigating the impact of free fatty acids and water content in feedstocks, which often cause unwanted side reactions, (iii) improving catalyst stability and efficiency through tailored preparation techniques, such as doping and support materials, and (iv) evaluating environmental and economic benefits. CaO catalysts derived from waste materials show promise due to their high basicity, reduced methanol solubility, and accessibility, offering a feasible route to biodiesel production at a lower cost. This review summarizes current advancements and suggests pathways for future development to improve the industrial viability of waste-derived CaO catalysts in biodiesel applications.
... The reduction in carbon emission and pollution is possible by two ways i.e. either reduce the dependence on fossil fuels or replace them with another clean fuel that are nonrenewable sources. Owing to population there are limited chances to reduce the use of fossil fuel [ [1][2][3]. ...
... Biodiesel is a biodegradable, non-toxic, and renewable and has been found to reduce carbon emission, particulates and hydrocarbon as compared to conventional diesel, through having similar properties to petroleum-based diesel. The basic principle behind biodiesel production is the transesterification reaction of vegetable oil or fat reacts in presence of alcohol by using a catalyst [1][2][3][4]. ...
... Lukić et al. [39] reported that CaDG has an effect mostly on the initial period of the reaction because CaDG acts as an emulsifier that enhances the solubility of the immiscible liquid to accelerate the methanolysis rate of sunflower oil. Kouzu et al. [40] also proposed that the formation of CaDG likely acted as a solid base catalyst that can accelerate the transesterification rate corresponding to the FAME yield profile (Fig. 1). However, when methanol was consumed during the reaction, the dilution of methanol with acetone and THF was more pronounced resulting in a limited reaction rate as illustrated in the lower equilibrium compared to using the green methyl myristate solvent. ...
... This result also supported the synergistic effect of the ultrasonic and solvent combination to promote the transesterification rate. Ultrasonic irradiation was found to be suitable for the heterogeneous catalytic system because the small bubbles of methanol and the solvent were produced via the cavitation phenomena and were easily adsorbed on the active site of CaO, possibly promoting a new active species (CaDG) with the enhancement of the transesterification rate [20,40]. The mixed solvent was then used to study the effect of operating parameters in the circulated FUS. ...
A R T I C L E I N F O Keywords: Biodiesel CaO Transesterification Synergistic effect Mixed solvent Solvent addition in presence of ultrasonic A B S T R A C T This work focuses on the improvement of biodiesel production with the addition of solvents (acetone, THF, and methyl myristate) in CaO catalyzed transesterification of palm oil and methanol in an ultrasonic reactor using a methanol to oil molar ratio of 9:1, reaction temperature of 60 • C, and CaO loading of 5 and 10 wt%. The addition of acetone and THF in the presence of ultrasonic irradiation expressed the synergistic effect which can accelerate the initial transesterification rate by increasing the solubility and in-situ generations of microbubble droplets and calcium glyceroxide as a new active species. The addition of methyl myristate enhanced the biodiesel yield by acting as an emulsifier of the reaction mixture and producing microemulsion droplets with the help of ultrasonic irradiation. Moreover, the mixed acetone and methyl myristate with existing ultrasonic irradiation can promote CaO catalyzed transesterification by accelerating the initial rate and achieving a high biodiesel yield (97.3%). The quality of the synthesized biodiesel in terms of physical properties is proven to meet the biodiesel standard.
... Among various heterogeneous catalysts, calcium oxide (CaO), as a common base earth metal oxide, is one of the most promising for biodiesel production [8]. Kouzu et al. [9,10] pointed out that CaO shows activity only at the beginning of the reaction until the FAME content is below 30 %. As the methanolysis reaction proceeds, the synthesized by-product glycerol can react with calcium ions from CaO producing a new highly active catalyst, calcium diglyceroxide (glyceroxide), Ca(C3H7O3)2. ...
... When quicklime was used as a catalyst, the formation of the CaO-glycerol complex during the reaction happened gradually, and the concentration of glycerol as a by-product still was not at the level to promote the reverse reaction as in the reactions catalyzed by the C-G and C-ChG complexes. The transformation of CaO into Ca-glyceroxide during the methanolysis requires a higher amount of glycerol [9,26]. Thereby, Ca-glyceroxide was formed at the end of the reaction (after 2 h), while at the beginning of the reaction (after 1 h) it could hardly be distinguished because of the low amount of glycerol [26]. ...
Oil methanolysis over modified CaO catalysts was studied to assess the catalytic performance and to define an appropriate kinetic model. CaO was modified by commercial glycerol and a deep eutectic solvent (DES), choline chloride : glycerol (ChCl : Gly), to obtain catalytically active complexes of CaO and glycerol. The main goal was to investigate the effect of the obtained complexes on the reaction rate and fatty acid methyl ester (FAME) content and to describe the variation of the triacylglycerol (TAG) conversion degree during the reaction time. Fourier transform infrared spectroscopy (FTIR) was applied to confirm the formation of CaO complexes with glycerol or the glycerol-based DES. Different catalyst loadings (0.5, 1, and 5 % of oil weight) and methanol-to-oil molar ratios (6 : 1 and 12 : 1) were applied for investigation of the sunflower oil methanolysis at 60 oC. Two kinetic models were employed yielding the kinetic parameters, which depended on the catalyst loading and the methanol-to-oil molar ratio. Both models showed valid applicability for describing the kinetics of the reactions catalyzed by both complexes (the mean relative percent deviation was lower than 10 %).
... Further advantages of CaDG are the low solubility in methanol and high resistance to atmospheric agents such as H 2 O and CO 2 . There is evidence that the use of suitable supporting materials reduces leaching of Ca 2+ ions and this helps the development of a continuous flow reactor [16,[21][22][23][24][25][26]. ...
... No additional intermediate crystalline phases were observed in the PXRD data. Time-resolved PXRD studies of both catalysts are in agreement with previous work, which shows that the activation mechanism consists of two steps [16,[19][20][21][22][23][24][25][26][27]. The first step is catalysed by the basic oxygen of CaO and CaOH. ...
Alternative and sustainable waste sources are receiving increasing attention as they can be used to produce biofuels with a low carbon footprint. Waste fish oil is one such example and can be considered an abundant and sustainable waste source to produce biodiesel. Ultimately this could lead to fishing communities having their own ‘off-grid’ source of fuel for boats and vehicles. At the industrial level, biodiesel is currently produced by homogeneous catalysis because of the high catalyst activity and selectivity. In contrast, heterogeneous catalysis offers several advantages such as improved reusability, reduced waste and lower processing costs. Here we investigate the phase evolution of two heterogeneous catalysts, CaO and a Ca 3 Al 2 O 6 :CaO (‘C3A:CaO’) composite, under in-situ conditions for biodiesel production from fish oil. A new reactor was designed to monitor the evolution of the crystalline catalyst during the reaction using synchrotron powder x-ray diffraction. The amount of calcium diglyceroxide (CaDG) began to increase rapidly after approximately 30 min, for both catalysts. This rapid increase in CaDG could be linked to ex-situ nuclear magnetic resonance studies which showed that the conversion of fish oil to biodiesel rapidly increased after 30 min. The key to the difference in activity of the two catalysts appears to be that the Ca 3 Al 2 O 6 :CaO composite maintains a high rate of CaDG formation for longer than CaO, although the initial formation rates and reaction kinetics are similar. The Ca for the CaDG mainly comes from the CaO phase. In addition, towards the end of the second test utilising the CaO catalyst (after 120 min), there is a rapid decrease in CaDG and a rapid increase in Ca(OH) 2 . This was not observed for the Ca 3 Al 2 O 6 :CaO catalyst and this is due to Ca 3 Al 2 O 6 stabilising the CaO in the composite material. No additional calcium containing intermediate crystalline phases were observed during our in-situ experiment. Overall this specialised in-situ set-up has been shown to be suitable to monitor the phase evolution of heterogeneous crystalline catalysts during the triglycerides transesterification reaction, offering the opportunity to correlate the crystalline phases to activity, deactivation and stability.
... It is assumed that transesterification with heterogeneous alkaline catalysts can overcome the disadvantages of the process with homogeneous catalysts. However, the reaction of the catalyst with glycerin may lead to the formation of side products (126,145). Ca and Mg are most widely used as heterogeneous alkaline catalysts due to their poor solubility in methanol and the strongest catalytic activity among alkaline earth metal oxides (146). The formation of calcium diglyceride during transesterification with CaO is shown in Figure 5. ...
... The reaction mechanism is repeated two or more times until the formation of biodiesel and glycerin (126). It was reported that the surface of CaO strongly adsorbs FFAs, atmospheric carbon dioxide, and water lowering biodiesel yield and inhibiting catalyst regeneration (145). However, these problems can be overcome by loading CaO on carrier or support providing better availability of the catalytically active site and stability of the catalyst (147). ...
Although fossil fuels remain the main source of energy, the volume of renewable sources of energy is constantly increasing. Biodiesel is a promising alternative fuel due to the number of advantages compared to fossil fuel and other types of biofuel. The specific objective of this study was to identify the difference between conventional and novel technologies applied during the whole life cycle of biodiesel production and consumption. The study offers some important insights into the recent advances in the biodiesel industry including biodiesel production from microalgal lipids, advanced homogenous and enzymatic transesterification, non-catalytic supercritical transesterification, application of microwave and ultrasound assisting technologies. Considering all the factors affecting the efficiency and safety of the biodiesel production process, here we reviewed the main principals and recent achievements in the environmental life cycle assessment of biodiesel production and consumption.
... CSTRs are widely used in biodiesel production due to their mechanical mixing systems, which improve mass transfer between immiscible oil and alcohols. Kouzu et al. examined the effect of retention time in a CSTR loaded with CaO, finding that FAME yield was limited to 90 % due to the broad residence time under the mixing system [12]. ...
Conventional homogeneous catalysts exhibit rapid reaction kinetics and affordability but face significant challenges, including the cumbersome separation of catalysts, complexities in product purification, and the generation of wastewater. In this regard, Na-GCN was previously developed as an effective heterogeneous catalyst for transesterification. To advance the industrial application of these catalysts, it is essential to incorporate a continuous production system and high-quality feedstock. Fixed bed reactors offer the advantage of simple operation and have been widely utilized in continuous biodiesel production. In this study, Na-GCN was applied to the transesterification of waste oils in a continuous fixed bed reactor. Various reaction conditions, including temperature, retention time, and the oil-to-methanol ratio, were compared and optimized. The transesterification of waste oil simulant, waste cooking oil, and waste food oil was conducted under the optimized conditions. The FAME content was measured using gas chromatography equipped with a flame ionization detector and HP-INNOWax, following an internal standard method. Notably, FAME yields exceeding 90% were maintained for 100 hours of continuous operation using Na-GCN and waste cooking oil. The reaction system also demonstrated enhanced stability over 100 hours, even when processing waste food oil with high levels of impurities.
... From the observation, it is found that by adding 150 mg of catalyst the biodiesel prepared will have maximum homogeneity and reasonable FAME. Several catalysts have been explored for the transesterification of soybean oil as shown in Table-1 [38][39][40][41][42][43][44]. It can be observed that combined alkali metal oxide and silica in same material i.e. wollastonite has assisted in production of biodiesel (82.6%) in a less time and at a low temperature when compared to these findings. ...
The heterogeneous catalyst plays an important role in the production of biodiesel at industrial level. In present work, the utilization of wollastonite as a heterogeneous catalyst is attempted to explore its non-biomedical application. Wollastonite was synthesized by using the auto combustion method and L-alanine was used as a fuel for combustion. The X-ray diffraction pattern reveals the phase purity of wollastonite. The Fourier transform infrared spectra of the calcined precursor show the presence of characteristics functional groups in wollastonite. To evaluate the catalytic ability of the prepared wollastonite, transesterification reaction of soybean oil with methanol was performed. Following the reaction, the biodiesel, glycerol and the catalyst were separated by centrifugation. Optimization of the percentage of catalyst used in biodiesel production was done by using various quantities of catalyst during the transesterification reaction and subjecting the produced biodiesel to gas chromatography. It can be concluded that combined alkali metal oxide and silica in wollastonite has assisted in production of biodiesel (82.6%) in a less time and at a low temperature.
... The superficial basic sites are generated by the presence of the surface metal ion (M 2+ ) that acts like a Lewis acid and an oxygen ion (O 2− ) that behaves like a Brønsted basic site (Chen et al. 2012;Endalew et al. 2011;Hattori 1995;Meher et al. 2006a, b;Tavizón-Pozos et al. 2021). The CaO has been widely used due to its low price and alkalinity, and it can be obtained from different natural sources (de Sousa et al. 2016;Kouzu et al. 2008;Kouzu and Hidaka 2012). Nonetheless, there are still challenges to overcome by improving the catalytic properties of this material. ...
CaO-supported Li and K catalysts were studied for transesterification reactions. The CaO was obtained from calcined commercial limestone. The catalysts were impregnated with LiNO3 and KNO3, reaching a loading of 3 wt.% of alkali metal. The synthesized catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and Hammett indicators. The catalytic transesterification evaluations of tributyrin, triestearin, and triolein with methanol were carried out with methanol/triglyceride molar ratio of 20:1 and 3 wt.% of catalyst at 60 °C for one hour. It was found that the strength of the alkaline sites increased when alkali metal was added to the support since these metals prevented the formation of Ca(OH)2. The Li/CaO catalyst presented higher basic strength and higher catalytic activity. It was observed that short-chain triglycerides were found to be more reactive than long-chain and unsaturated ones; likewise, saturated chain triglycerides are more reactive than unsaturated ones due to fewer interactions with the active sites. Finally, potassium avoided the lixiviation of the catalysts to the liquid phase.
... A biodiesel yield (above 95%) could be obtained when CaO was used (Calero et al., 2014). However, the use of CaO could raise a common concern involving chemical stability and reusability because H2O and CO2 can be readily absorbed on the surface of pure CaO catalyst upon exposure to air (Boonphayak, Khansumled, & Yatongchai, 2021), resulting in a decrease of the catalytic performance (Kouzu, Yamanaka, Kasuno, Hidaka, & Tajika, 2008). Besides, it was reported that CaO catalyst was partially dissolved during transesterification process, leading to a reduction of reusability (Teo, Rashid, & Taufiq-Yap, 2014). ...
Giant leucaena wood was utilized to prepare heterogeneous catalysts through a fast pyrolysis method and chemical activation for transesterification. The obtained catalysts were investigated using SEM, CHNS/O analyzer, XRF and XRD. The influence of the concentration of KOH (3-9 M), catalyst amount (0.25-2.0 g), methanol to oil ratio (4:1-10:1), and reaction time (30-75 min) on FAME yield was also studied on transesterification reaction carried out at 60ºC under a 750 rpm stirring speed. The experiment results demonstrate that chemical activation was required to improve the porosity of the catalyst. The result showed that a well-developed porous structure was observed, as the concentration of KOH increased activated biochar become more porous. 7M-KOH for chemical activation was the best condition to obtain a porous catalyst. It was found that the main factors affecting the FAME yield were dependent on various parameters including methanol: oil ratio, catalyst loading, reaction time and stirring speed via transesterification process. The highest yield of 94.06% was achieved on 0.5g of the catalyst activated by 7M-KOH, a methanol:oil ratio of 6:1 and a 1-hour reaction. The obtained biodiesel mainly composed of different fatty acid in follow order C18:1 > C16:0 > C18:2 > C18:0. Properties reached the ASTM D6751-12 and EN 14214:2012 standard, indicating that leucaena-derived biochar is potentially utilized in biodiesel production.
... The comparison of these two sources of fuel illustrates that in terms of lubricating properties, cetane number, and flash point, biodiesel is preferable and that in term of heat production in combustion, they are almost the same. 3 Also, a significant reduction in the amount of unburned hydrocarbons and emitted carbon monoxide is another advantage of using biodiesel. Furthermore, an adequate amount of oxygen (about 11% by weight) in the structure of biodiesel leads to complete combustion, and the absence of sulfur compounds in its structure makes it an environmentally friendly fuel. ...
In this study, biodiesel production via transesterification of waste cooking oil as feedstocks and methanol was studied over KOH/Fe3O4@MCM‐41 catalyst. The X‐ray diffraction, BET, FT‐IR, and field‐emission scanning electron microscopy techniques were applied to describe the structural characterization of the catalyst. The effects of the catalyst amount, reaction time, and alcohol to oil molar ratio were investigated using central composite design method and ANOVA analysis. Among the evaluated conditions, 3.32 h reaction time, 8.51% loaded catalyst, and 42.36 alcohols to oil molar ratio can provide an optimal biodiesel production of 93.95%. Moreover, the catalyst revealed high‐reusability over three cycles. Based on the reaction kinetics study, several parameters such as rate constants at three temperatures, activation energy and frequency factors were investigated.
... Two intensive peaks at 63 ppm and 72 ppm were observed on the 13 C NMR spectrum of CaO-G (Fig. 7d), which can be assigned to -OCH 2 and -OCH. These peaks are characteristic of glycerol carbon chains [60]. These results indicate that CaO-G has a polymeric structure possibly via a chain link of -Ca-O-CH 2 -CH(OH)-CH 2 O-. ...
Biomass derivatives are renewable and oxygen-rich organic feedstocks, which can be partially or completely hydrogenated to various value-added molecules with a prerequisite of expensive and tailored metal catalysts. Here, waste chicken eggshell was valorized by calcination and glycerol treatment to prepare basicity- and hydrophobicity-enhanced catalyst (CaO-G), which exhibited high efficiency (apparent activation energy 11.5 kJ mol⁻¹) for selective hydrogenation of bio-based veratraldehyde (VE) to high-value veratryl alcohol (VA) (up to 99.7% yield, TOF: 166.7 h⁻¹) at room temperature in only 10 min. The involved reaction path was explicitly uncovered by in-situ surface-enhanced Raman. Theoretical calculations were adopted to elucidate the remarkably promotional role of CaO-G in the activation of Si–H for the expedited hydrogenation process. The waste-derived catalyst could be recycled at least five times with no evident decline in catalytic activity and was highly selective for reduction of different unsaturated bio-based aldehydes to alcohols (> 90% yields) at room temperature.
Graphical abstract
An eggshell-derived catalyst prepared by facile calcination and treatment with glycerol shows enhanced basicity and hydrophobicity, which is highly selective for hydrogenation of various bio-based aromatic aldehydes to relevant aromatic alcohols (> 90% yields) at room temperature.
... The reference sample, calcium diglyceroxide, was as active as the collected catalyst in the transesterication and was air-tolerant 194 22 ...
Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually. One solution is biodiesel production via the transesterification process, which is environmentally feasible due to its low-emission diesel substitute. Significant issues arising with biodiesel production are the cost of the processes, which has stuck its sustainability and the applicability of different resources. In this article, the common biodiesel feedstock such as edible and non-edible vegetable oils, waste oil and animal fats and their advantages and disadvantages were reviewed according to the Web of Science (WOS) database over the timeframe of 1970-2020. The biodiesel feedstock has water or free fatty acid, but it will produce soap by reacting free fatty acids with an alkali catalyst when they present in high portion. This reaction is unfavourable and decreases the biodiesel product yield. This issue can be solved by designing multiple transesterification stages or by employing acidic catalysts to prevent saponification. The second solution is cheaper than the first one and even more applicable because of the abundant source of catalytic materials from a waste product such as rice husk ash, chicken eggshells, fly ash, red mud, steel slag, and coconut shell and lime mud. The overview of the advantages and disadvantages of different homogeneous and heterogeneous catalysts is summarized, and the catalyst promoters and prospects of biodiesel production are also suggested. This research provides beneficial ideas for catalyst synthesis from waste for the transesterification process economically, environmentally and industrially.
... Eggshell-derived calcium oxide is utilised as a catalyst, and its active ingredients depend on a particular catalytic system (Kouzu et al., 2008;Ebadi Pour et al., 2021). Specifically, when calcium oxide is extracted from eggshells as a catalyst to produce biodiesel, the obtained product contains not only calcium oxide, but other components as well. ...
The synthesis costs of macrolide musks are higher than those of other commercial musks. To make this process less expensive, eggshell waste was calcined at a low temperature to obtain a catalyst for the cyclopentadecanolide production via reactive distillation using a glycerol entrainer. X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses of the original and recovered catalysts revealed that the main catalytic ingredient was calcium glycerolate (CaG) and not calcium diglyceroxide (CaDG). The basic strengths of CaG and CaDG obtained by Hammett indicators were 7.2 < H_≤ 15.0 and 9.8 < H_≤15.0, while the corresponding base amounts were 1.9 and 7.3 mmol/ g, respectively. Because CaG was soluble in glycerine, the catalyst was efficiently reused. The reaction product containing over 95.0% cyclopentadecanolide with a yield of 49.8% was obtained at a temperature of 190°C and catalyst amount of 12 wt% after 7 h of reaction. Thus, eggshell waste may be directly placed into the reaction mixture after calcination at 600°C to synthesise a large amount of cyclopentadecanolide within a relatively short time. The results of this work indicate that eggshell waste can serve as a potential eco-friendly and affordable catalyst source for the production of macrolide musks.
... The natural calcium (Ca) sources from waste are found in crab shells, eggshells, and animal bones [71]. It was observed that the FAME yield was 93%, using CaO which was earlier obtained from limestone (CaCO 3 ) calcinations, under optimal conditions [72]. Moreover, it was found that the FAME yield was 88.81% for the transesterification of ground nut using a CaO catalyst [73]. ...
The effective transesterification process to produce fatty acid methyl esters (FAME) requires the use of low-cost, less corrosive, environmentally friendly and effective catalysts. Currently, worldwide biodiesel production revolves around the use of alkaline and acidic catalysts employed in heterogeneous and homogeneous phases. Homogeneous catalysts (soluble catalysts) for FAME production have been widespread for a while, but solid catalysts (heterogeneous catalysts) are a newer development for FAME production. The rate of reaction is much increased when homogeneous basic catalysts are used, but the main drawback is the cost of the process which arises due to the separation of catalysts from the reaction media after product formation. A promising field for catalytic biodiesel production is the use of heteropoly acids (HPAs) and polyoxometalate compounds. The flexibility of their structures and super acidic properties can be enhanced by incorporation of polyoxometalate anions into the complex proton acids. This pseudo liquid phase makes it possible for nearly all mobile protons to take part in the catalysis process. Carbonaceous materials which are obtained after sulfonation show promising catalytic activity towards the transesterification process. Another promising heterogeneous acid catalyst used for FAME production is vanadium phosphate. Furthermore, biocatalysts are receiving attention for large-scale FAME production in which lipase is the most common one used successfully This review critically describes the most important homogeneous and heterogeneous catalysts used in the current FAME production, with future directions for their use.
... The analysis of spent calcium oxide showed that the glycerol formed reacted with calcium oxide during the induction period, producing calcium glyceroxide, which is characterised by high catalytic activity in the transesterication. Similar conclusions were made by Kouzu et al., [194][195][196] Gupta et al., 197 and Reyero et al. 198 The authors 197,199 suggested that the transesterication in the presence of calcium glyceroxide proceeds by a heterogeneous catalytic mechanism, and the contribution of homogeneous catalysis is negligible. However, calcium glyceroxide is well soluble in glycerol, methyl alcohol, and reaction medium. ...
Green chemistry provides a broad range of possibilities for researchers to design products and processes that minimise or eliminate the use and generation of hazardous substances in chemical engineering. Theuse of renewable feedstockscoupled withcatalysisis one of the key principles of green chemistry. In this regard, non-edible vegetable oils and fatty acid methyl esters (biodiesel) produced by the transesterification of vegetable oils have a great potential in the chemical industry. Their catalytic conversion allows them to produce a wide range of useful chemicals. At the same time, the use of fatty acid methyl esters has advantages and they are more preferable as compared to vegetable oils due to fewer impurities, lower viscosity,etc.The production of biodiesel is associated with the formation of another important and versatile chemical, glycerol, which is currently produced in the world only through the transesterification of vegetable oils. This critical review highlights the recent achievements in the green and sustainable production of various chemicals from fatty acid methyl esters, including oxidation, amidation, hydrogenation, deoxygenation, ethoxylation, metathesis, and isomerisation reactions. A special focus is given to the applicability of each method in industry. We suppose that this comprehensive review will provide insight into the most significant ways to convert fatty esters into valuable products since they are “rough diamonds” and have a great future in the chemical industry.
... The suitability of microalgal biomass as a biofuel feedstock is closely related to the length and degree of saturation of its fatty acids as specified by the key characters of iodine value, oxidation stability, cetane number, etc. This has been justified apparently through physical properties comprising viscosity, density, heating value, and melting temperature, etc. [79,80]. ...
... In this same review, the authors mention that during the reaction, calcium may transform in different active species. It can react with methanol to produce calcium methoxide and with glycerol to form calcium glyceroxide (Ca[O(OH)2C3H5]2), which is less active than CaO [101]. However, this compound can reversibly react with methanol resulting in Ca organic species (CH3O-Ca-O(OH)2C3H5), which also possess weak basic sites and, thus, are less active than CaO [102]. ...
Biodiesel produced through catalytic transesterification of triglycerides from edible and non-edible oils and alcohol is considered an alternative to traditional petro-diesel. The interest in the use of alkaline earth metal oxides as heterogeneous basic catalysts has increased due to their availability, non-toxicity, the capacity to be reused, low cost, and high concentration of surface basic sites that provide the activity. This work is a compilation of the strategies to understand the effect of the source, synthesis, and thermal treatment of MgO, CaO, SrO, and BaO on the improvement of the surface basic sites density and strength, the morphology of the solid structure, stability during reaction and reusability. These parameters are commonly modified or enhanced by mixing these oxides or with alkaline metals. Also, the improvement of the acid-base properties and to avoid the lixiviation of catalysts can be achieved by supporting the alkaline earth metal oxides on another oxide. Additionally, the effect of the most relevant operation conditions in oil transesterification reactions such as methanol to oil ratio, temperature, agitation method, pressure, and catalysts concentration are reviewed. This review attempts to elucidate the optimum parameters of reaction and their application in different oils.
... Calcium diglyceroxide is a suitable candidate for the transesterification of triglycerides in heterogeneous conditions; even more, some studies showed that CaO needs to be transformed to CaDG during the reaction to be active [10,11]. Some synthesis protocols have been published, but in a batch reactor and with some hours of residence time [12], so an industrial approach has to be developed and the high-throughput reactor is a good candidate to obtain this objective. ...
The development of an innovative and sustainable high-throughput reaction platform allows optimizing a wide range of chemical processes (materials synthesis and catalysis, among others) to tackle the Green Deal. This tool unifies, for the first time, the benefits of mechanical energy, thermal and pressure activation in continuous flow with an induction in situ heating system, facilitating the incorporation of inputs (liquids, solids and gases) with controlled pressure. As a result of the synergistic effect of this simultaneous activation, this technology will: (i) shorten reaction times; (ii) decrease temperature; (iii) improve reactions kinetics as mass transfer limitations are reduced; (iv) minimize the use of solvents; (v) decrease the reaction steps; (vi) increase the volume treated, enabling a real scale-up; and (vii) enhance the yields and/or selectivity. This new high-throughput reactor is used for the synthesis of calcium diglyceroxide (CaDG), minimizing the reaction steps and cost, to obtain a pure CaDG. This heterogeneous catalyst is used for biodiesel production and valorization of the glycerol generated as a by-product. An efficient synthesis protocol of CaDG has been developed, requiring shorter time, without heating, and no need for a solvent. This new process facilitates oil–methanol mixing in the transesterification process, thus minimizing the mass transfer limitations associated with the immiscibility of reactants. In addition, this process has been optimized by using CaDG as a solid catalyst.
... Then upstream product is pumped into a separator tank. When a base or acid used as a catalyst, the upper layer is contains methyl ester, catalyst, and excess alcohol, and the lower level is glycerol (Guan et al., 2004;Kouzu et al., 2008). Biodiesel ...
Conventional homogeneous catalysts exhibit rapid reaction kinetics and affordability but face significant challenges, including the cumbersome separation of catalysts, complexities in product purification, and the generation of wastewater. In this regard, Na–graphitic carbon nitride (GCN) was previously developed as an effective heterogeneous catalyst for transesterification. To advance the industrial application of these catalysts, it is essential to incorporate a continuous production system and high-quality feedstock. Fixed bed reactors offer the advantage of simple operation and have been widely utilized in continuous biodiesel production. In this study, Na–GCN was applied to the transesterification of waste oils in a continuous fixed bed reactor. Various reaction conditions, including temperature, retention time, and the oil-to-methanol ratio, were compared and optimized. The transesterification of waste oil simulant, waste cooking oil, and waste food oil was conducted under the optimized conditions. The fatty acid methyl ester (FAME) content was measured using gas chromatography equipped with a flame ionization detector and HP-INNOWax, following an internal standard method. Notably, FAME yields exceeding 90% were maintained for 100 h of continuous operation using Na–GCN and waste cooking oil. The reaction system also demonstrated enhanced stability over 100 h, even when processing waste food oil with high levels of impurities.
Biodiesel has received tremendous attention as a sustainable energy source. This review presents an overview of various catalysts utilized in biodiesel production and compares their potential for producing biodiesel. Presented here are the excellent features of the various catalysts while highlighting their drawbacks. For instance, production of biodiesel with homogeneous base catalysts is easy but it can only be used with refined oils having low levels of free fatty acid (FFAs). When homogeneous acid is used in esterification, it causes reactor corrosion. Water and FFAs do not affect heterogeneous acid catalysts. Thus, transesterification of triglycerides into biodiesel and converting FFAs into biodiesel through esterification can be catalyzed more efficiently using a heterogeneous acid catalyst. Biocatalysts are also being used to produce biodiesel from oils with high FFAs. However, heterogeneous acid catalysts and biocatalysts are not suitable for industrial application due to serious mass transfer limitations. Biodiesel yield and conversion were compared over various catalysts in this paper. Also presented are the effects of different reaction parameters on biodiesel yield over different catalysts. The correct interplay of factors like reaction temperature, time, alcohol-to-oil molar ratio, and catalyst loading produces optimal process conditions that give the highest biodiesel yield.
The pursuit of environmental sustainability and the harnessing of renewable energy sources pose significant challenges, compelling researchers to explore innovative solutions. Carbon materials have emerged as crucial players in both energy, environmental, and agricultural applications, owing to their exceptional properties. Biomass waste, abundant and often overlooked, has captured attention as a promising precursor for the development of carbon-based products. This is particularly evident in the creation of biochar and hydrochar, whose characteristics are intricately shaped by production methods, source materials, and process conditions. These variables collectively influence their suitability for diverse purposes, ranging from energy storage and conversion to soil and water restoration, making them invaluable tools in sustainable agriculture and environmental conservation, as well as in the capture of greenhouse gases. The versatility of biomass-based activated carbon is further enhanced by the diverse array of feedstocks and activation pathways employed. This adaptability renders it suitable for a multitude of applications, creating a symbiotic relationship between resource abundance and functional efficacy. This comprehensive review aims to evaluate contemporary thermochemical methods for converting organic waste into high-value carbon materials. Moreover, it delves into strategies that augment the functionality of these materials, including activation processes and surface modifications. The review also illuminates recent advancements in the realms of energy, agriculture, and environmental research. It consolidates existing literature on physicochemical characteristics and techno-economic assessments of engineered carbon materials, providing a nuanced understanding of their potential impact. While exploring challenges, prospects, and future research directions, this review outlines the synthesis of carbon compounds from biomass. It emphasises the capacity to produce distinct chars with unique properties through various production methods, tailoring them to the specific requirements of diverse environmental applications.
Graphical Abstract
Various catalysts are being used in fuel production from biomass and polymeric waste for the obtention of an alternative energy source with both environmental friendliness and economic viability. Biochar, red mud bentonite, and calcium oxide have been shown to play a pertinent role as catalysts in waste-to-fuel conversion processes, such as transesterification and pyrolysis. In this line of thought, this paper has provided a compendium of the fabrication and modification technologies of bentonite, red mud calcium oxide, and biochar, together with their various performances in their application in the waste-to-fuel processes. Additionally, an overview of the structural and chemical attributes of these components is discussed regarding their efficiency. Ultimately, research trends and future points of focus are evaluated, and it is observed that techno-economic optimization of catalyst synthetic routes and investigation of new catalytic formulations, such as biochar and red mud-based nanocatalysts, are potential prospects. This report also offers future research directions that are anticipated to contribute to the development of sustainable green fuel generation systems.
Calcium glycerolates were synthesized as monoglycerolates, and diglycerolates with different main basal plane orientations (111) or (200) and used in the methanolysis of soybean oil. All the solids presented catalytic actives with a conversion rate of up to 60% for monoglycerolates and up to 98% for the diglycerolates. The reuse tests indicated that the diglycerolate-111 was the most efficient, with 96% of conversion in the first three reactions and almost 82% after the fourth use. It lost effectiveness after the fifth reuse reaction because of segregation in a non-catalytic mixture of CaO and CaCO3 phases.Graphical Abstract
Calcined waste scallop shell (Patinopecten yessoensis) was used as a basic heterogeneous solid catalyst for the transesterification of tripalmitin as a model triglyceride for assuming biodiesel production. The scallop shell was pulverized and calcined at 900 and 1000°C for 4 h. Calcined reagent calcium carbonate was also used as a control catalyst. The transesterification experiments were carried out at 30°C with varying catalyst dosage and calcination conditions. In the most experimental condition, the yield reached ~90% within 8–10 h. The overall reaction rate constant, k, was determined by simple first‐order reaction kinetics. The calcined catalyst was characterized using SEM, EDS, and XRD analysis. The number of basic active sites on the surface was determined by titration with benzoic acid. A linear relationship between k and the number of the basic active sites was obtained. The time course of the concentration of the products could be estimated using this relationship.
Currently, biodiesel is pointed out worldwide as the main alternative in the complementation and substitution of petrochemical diesel. However, the current industrial route of synthesis of this biofuel depends on the cost of raw materials (which are also destined for food purposes) and the expense of the production process. Aiming to remedy this obstacle, the use of solid, sustainable, low‐cost, efficient, and reusable catalysts in residual raw materials, such as waste cooking oils, has been highlighted as a promising alternative. This work focused on studying the influence of the glycerin content used in the preparation by wet impregnation of catalyst calcium diglyceroxide in the efficiency of transesterification of waste cooking oil. The catalyst was synthesized from Cao from chicken eggshell, raw glycerin coproduct from biodiesel and methanol. The transesterification reactions were performed using 120 g of frying residual oil, methanol:oil molar rate of 6:1, constant shaking, and reaction temperature of 63 ± 1 °C for 180 minutes. The catalyst material synthesized with residual glycerin was active for four reactions (without reactivation of its sites) with high percentage of efficiency 96.13; 96.85; 95.93; 91.65, respectively. It was noted that the glycerol purity correlated with changes in the structural morphology of the final compound, as well as changes in the leaching rate, acidity index, water content, and ester content of the blends. It was found that adding 15% water to the lipid material correlated with increase in ester content (99%) in the synthesized biodiesel. This article is protected by copyright. All rights reserved.
A new fluorescent sensor based on rhodamine B derivative appended with
octanoic acid (R2) was synthesized and proposed for copper (II) ion determination via ring
opening reaction of spirolactam based rhodamine B in acetonitrile. Upon the addition of Cu2+, the fluorescence enhancement was observed and the color was changed from colorless to orange. In the case of other metal cations, the emission band and the color of solution remained unchanges. The sensing mechanism was investigated by fluorescence technique and the result exhibits a binding mode of R2 and Cu2+ of 1:1 ratio. In addition, the detection limit of R2 toward Cu2+ was 5 nM. This sensor highlights the promising sensitivity and selectivity for Cu2+ sensing.
Biodiesel has comparable properties to diesel fuel; hence, it becomes a promising substitute to diesel fuel. The development of exceedingly effective biocatalyst is a key prerequisite for the production of biofuels, most especially biodiesel. Heterogeneous catalysts are regarded to be very prospective for transesterification process in biodiesel production owing to their numerous advantages, which include separation of catalyst from reaction mixture with ease, separation from reaction mixture with ease, regeneration, decreased corrosion, decreased cost and environmental friendliness. Heterogeneous catalysts can substitute homogeneous catalysts in situations that limit their efficiency. Hence, synthesized sustainable catalysts are required for increasing process performance, reduction in energy cost and production of cleaner products like ultralow sulphur biodiesel. Here, we gave a brief review on the advancement in sustainable heterogeneous catalysts for biodiesel production.KeywordsBiodieselBiocatalystNanotechnologySustainable catalystsHeterogeneous catalystsHomogeneous catalysts
The consumption of primary energy gets enhanced on a daily basis with the increase of population and modern industries. In 2015, it was reported that the energy consumption was over 150,000,000 Gigawatt hour (GWh) and it is predicted that by the year 2050 the consumption will increase by 57%. Fortunately, the emergence of biofuels has proved a potential substitute to the current growing demand in energy market and reduces the threat to the environment. Among the wide array of biofuels, biodiesel has received a great amount of focus due to being an environmentally friendly biofuel as it is bio-degradable and renewable having less emissions as compared to petro-diesel. From another point of view, regarding the catalysis of biodiesel production, there is great interest recently to use heterogeneous catalysts, specially those derived from wastes, instead of homogeneous ones. This chapter provides an overview on the attempts which were done over the last years to utilize inorganic wastes to produce catalysts active for biodiesel synthesis. It covers the catalyst preparation conditions besides the optimum conditions of biodiesel synthesis using various catalysts and feedstocks.
Biodiesel has gained prominence a substitute for diesel in recent years, with many countries having policies to blend it with petroleum diesel. One of the raw materials to produce biodiesel is the catalyst used for its manufacture. The most used catalyst is sodium hydroxide (NaOH). However, the use of this catalyst requires some treatment of the oil before the reaction, which makes the use of certain oils to produce biodiesel difficult. Therefore, replacing sodium hydroxide with other catalysts has been the subject of much research among researchers. CaO is a catalyst that is a good substitute for NaOH, and this catalyst can be obtained from renewable sources and being a heterogeneous catalyst, it can be used in several batches to obtain biodiesel. This chapter deals with several renewable sources, mainly material husk residues, obtaining and using CaO as a catalyst in the synthesis of biodiesel.
Biodiesel is produced commonly by alcoholysis of lipid feedstock using homogeneous catalysts (e.g. KOH) soluble in an alcohol phase. Unfortunately, this process involves multiple purification steps of biodiesel and glycerol due to catalyst existence in both phases that hinder process viability. Besides, contents of free fatty acids FFAs > 2 wt%, and the presence of moisture limit the application of homogeneously catalyzed transesterification. Accordingly, heterogeneous catalysis is preferred owing to the ease of catalyst separation as well as its reusability. Within the field of heterogeneous catalysis, there is an ongoing trend to produce highly active solid catalysts based on chicken, animal and fish wastes as a way of waste management. This chapter introduces a review on the use of different fish and animal wastes, including their bones and fish scales, to produce active catalysts for biodiesel synthesis from various feedstocks, e.g. edible and non-edible oils. Besides, kinetic studies will be summarized as an essential aspect for the scale-up of the production process. Moreover, it will mention some of the techno-economic aspects related to the utilization of these wastes in the catalysis of biodiesel production and their impact on process feasibility.
Glycerol carbonate (GC) was synthesized by transesterification of glycerol with dimethyl carbonate (DMC) using calcium oxide (CaO) derived from eggshell as a catalyst. The best results of 96% glycerol conversion and 94% GC yield were achieved under the following reaction conditions: 0.08 mole ratio of CaO to glycerol, 1:2.5 mole ratio of glycerol to DMC, 60°C reaction temperature, and 3 hours reaction time. As expected, CaO showed deteriorated catalytic performance when recycling as observed by a rapid decrease in GC yield. This research showed that the active CaO phase first was converted to calcium methoxide (Ca[OCH3]2) and calcium diglyceroxide (Ca[C3H7O3]2) and finally to carbonate phase (CaCO3) which can be confirmed by XRD patterns. According to the phase transformation, the basicity decreased from 0.482 mmol/g to 0.023 mmol/g, and basic strength altered from strong basic strength (15.0 < H_ < 18.4) to weak basic strength (7.2 < H_ < 9.8), resulting in the lower catalytic activity of the consecutive runs. Despite the fact that the GC selectivity was almost 100%, the reaction products (methanol and GC) were not obtained in their stoichiometric ratio and their extents corresponded with that of the catalyst phase transformation to CaCO3. The mechanism of CaO catalyzed transesterification based on the condensation reaction of glycerol and catalyst was proposed, and in situ formation of water-derivative species was hypothesized as a cause of CaO transformation. CaO could react with DMC and water, generating methanol and CaCO3. This enabled unconventional monitoring of catalyst deactivation by checking if the mole ratio of methanol to GC was higher than 2:1 of its reaction stoichiometric ratio. It was also demonstrated that calcination of post-run catalyst at 900°C to CaO exhibited almost constant catalytic activity, and the mole ratio of methanol to GC was constant at its reaction stoichiometry (2:1) for at least 4 times use.
Biodiesel is a renewable fuel with various advantages, such as the reduced emissions of toxic gases (CO2, SO2, CO, and HC) when compared to fossil diesel. It can be produced by esterification or transesterification reactions. In this chapter, the application of nanomaterials as a catalyst in these reactions is investigated through a critical review. Thus the catalytic activity and how the catalyst size can improve it are reported. A trend is also established between this catalytic activity and the main reactional parameters (reaction time, temperature, alcohol/oil or acid molar ratio, and catalyst load) in order to obtain the optimized process. Therefore this chapter is divided into a discussion of the state of the art of biodiesel synthesis and nanomaterials (bio-based catalysts) applied in these reactions, as well as the optimization process to obtain the best reaction conditions. Moreover, the chapter also highlights the main methodologies used in nanocatalyst synthesis and their characterization.
In the activation of a heterogeneous catalyst, manipulating certain variables can affect its morphology, active sites and porosity which determine the efficiency of a heterogeneous catalyst. In this work, a highly efficient heterogeneous catalyst wassynthesized from waste turtle shell which is a novel waste material. Using the experimental design, the influence of three parameters: calcination temperature, calcination time and KOH loading on the catalyst efficiency were studied. The catalyst efficiency was measured by taking the average biodiesel yields in four re-use cycle. among others, a catalyst optimum efficiency of 81.2% was obtained at calcination temperature of 807°C, calcination time of 196mins and KOH loading of 33%(w/w). The obtained catalyst was found to be very efficient since itpossessed high catalytic property, including activity and selectivity even after been used in four transesterification reactions.
Ca-based catalysts are of strong interest for glycerol polymerization reaction due to their high catalytic performances, their wide availability and the absence of any toxicity. In the present study, we investigated the active phase of CaO, Ca(OH)2, CaCO3 and calcium diglyceroxide used as catalysts for this reaction. The solids were analyzed by XRD, solid-state ¹³C-NMR and TGA-DSC. XRD evidenced the presence of calcium glycerolate in the spent catalysts when CaO, Ca(OH)2 and calcium diglyceroxide were used as starting materials. This was corroborated by the TGA-DSC results. Further, the SS NMR results showed that the as-formed calcium glycerolate is a mixture of linear Ca(C3H7O3) and cyclic-branched Ca(C3H6O3). Moreover, the recycled catalyst issued, e.g., from CaO was more efficient that the initial catalyst with a glycerol conversion of 47 % (vs. 22 % initially for CaO) and a 70 % (vs. 55 %) selectivity to polyglycerols higher than tetraglycerol at 245 °C after 4 h in the presence of 3.5 mol.% of catalyst. As the main outcome, we have shown that Ca-glycerolate is the actual solid active phase, which is formed in situ from CaO and Ca(OH)2 playing the role of catalyst precursors. A mechanism involving the dissolution of CaO and Ca(OH)2, the formation of Ca-glycerolate and its precipitation followed by crystallization, supported by characterization studies, is proposed.
The butanolysis of Jatropha oil using glycerol enriched non-calcined calcium oxide as heterogenous catalyst was carried out to investigate the influences of reaction temperature and butanol: oil molar ratio on Jatropha oil conversion (XJOB) and the yield of fatty acid butyl esters (YFABEs). The central composite design involved two factors (reaction temperature and butanol: oil molar ratio) and two levels factorial (2²) was used to determine the impacts of the factors on XJOB and YFABEs and to optimize the reaction process. From the main factors and their interaction, temperature was found to highly affect both the XJOB and YFABEs. As curvatures are statistically significant (p ≤ 0.05), the second order models (quadratic models) were found to be more suitable to optimize the butanolysis process. Based on the regression models and the response surface methodology, the maximum XJOB (98.16%) and YFABEs (95.79%) were predicted to be obtained at the optimum temperatures of 87.35 and 90.48 oC and butanol: oil molar ratios of 9.13:1 and 13.24:1, respectively. The maximum YFABEs of 95.64% was also experimentally obtained at the optimum conditions predicted for the Y FABEs. From the results obtained for the experimental ranges investigated, the present study suggested that glycerol enriched non-calcined calcium oxide can be used as a good alternative catalyst for biodiesel production using butanol. More studies are also suggested for upscaling the reaction process of the current experiments by using more integrated reaction factors.
The production of fatty acid methyl esters (FAME) from waste frying oil (WFO) was studied using fly ash as received as a heterogeneous catalyst. The fly ash used in this research had a high content of both CaO and SO3, two compounds that have been previously proposed as catalysts in FAME production. The study was carried out on the basis of a response surface methodology (RSM). The model generated by RSM predicted as optimal conditions to obtain a 100% FAME yield at a methanol-to-oil molar ratio of 3.1:1, 11.2 (wt.% based on oil weight) fly ash and a temperature of 59 °C with agitation at 245 rpm and 6 h of reaction time. Additional experiments comparing anhydrous with aqueous medium showed that fly ash presented a high catalytic capacity to transform free fatty acids (FFA) into FAME through consecutive hydrolysis and esterification processes (hydroesterification) compared with that associated with the transesterification mechanism. According to the results, the fly ash used in this study would act as a multipurpose or “versatile” catalyst due to its chemical composition with constituents that act as acidic and basic catalysts, therefore, catalyzing the transesterification and hydroesterification reactions simultaneously and increasing the conversion yields of FAME.
Transesterification kinetics of Croton megalocarpus oil to produce fatty acid methyl esters (FAME) was studied using homogeneous NaOH and heterogeneous alkaline earth Nano MgO, MgO, Nano CaO, CaO, Reoxidized CaO, SrO, and BaO catalysts. Characteristic surface, bulk, and chemical properties of the heterogeneous catalysts were obtained which included surface area, pore properties, scanning electron micrography, X-ray diffraction, basic strength, and basicity. The catalyst porosity varied as Nano MgO > Nano CaO > MgO > CaO > CaO-RO > SrO > BaO and basicity as BaO > SrO > Nano CaO > CaO RO > CaO > Nano MgO > MgO. Catalysts NaOH, BaO, SrO, and Nano CaO gave a good FAME yield (>50%), and reaction order and rate constant have been reported for these catalysts, for both conventional heating and microwave irradiation. The overall reaction for NaOH was of 1st order for microwave irradiation with respect to triglyceride and of 2nd order with respect to triglyceride under conventional heating. For the heterogeneous catalysts, the overall reaction was of 3rd order, 2nd order with respect to triglyceride and 1st order with respect to methanol for both heating methods. Reaction rate constants for microwave irradiation were higher than those for conventional heating due to faster reaction rates under such heating. BaO was the most active heterogeneous catalyst, followed by SrO and Nano CaO, which was in accordance with their basicity.
In the present work, synthesis of CaO-SiO2 catalysts using industrial wastes including lime mud and kaolin residue was proposed. The CaO-SiO2 catalysts were synthesized through a simple precipitation followed by calcination at 950 °C. The synthesized catalysts consisted of quartz, CaO and Ca(OH)2 proportion of which depended on CaO:SiO2 ratio. The catalytic activity was also investigated. The FAME yield reached up to 93% when the catalyst with CaO:SiO2 = 2 was used. However, it was found to decrease with numbers of reuse.
The classical method of fatty acids methyl esters (FAME) production is based on triglyceride transesterification to methyl esters. Sodium hydroxide dissolved in methanol is used as a catalyst. The purpose of this work was to examine a heterogeneous catalyst, in particular calcium compounds, to produce methyl esters of rapeseed oil. This research showed that the transesterification of rapeseed oil by methyl alcohol can be catalysed effectively by basic alkaline-earth metal compounds: calcium oxide, calcium methoxide and barium hydroxide. Calcium catalysts, due to their weak solubility in the reaction medium, are less active than sodium hydroxide. However, calcium catalysts are cheaper and lead to decreases in the number of technological stages and the amount of unwanted waste products. It was found that the transesterification reaction rate can be enhanced by ultrasound as well as by introducing an appropriate reagent into a reactor to promote methanol solubility in the rapeseed oil. Tetrahydrofuran was used as additive to accelerate the transesterification process.
Studies of solid base catalysis performed in our group are summarized. Strongly basic sites for most solid base catalysts are generated by removal of water and carbon dioxide by pretreatment at high temperatures from the surfaces. The nature of the surface basic sites varies with the severity of the pretreatment conditions. Rearrangement of surface and bulk atoms occurs, in addition to the removal of water and carbon dioxide, during the pretreatment. The optimum pretreatment temperature varies with the type of reaction. Characterization of basic sites by the indicator method, TPD of CO2, O exchange between adsorbed CO2 and MgO surface, NMR of Cs-133 and F-19 are described. The catalytic behaviors of solid base catalysts are described for the following reactions; (1) double bond migration, (2) hydrogenation, (3) amination, (4) aldol addition, (5) nitroaldol reaction, (6) Michael addition, (7) conjugate addition of alcohol, (8) cyanoethylation, (9) transesterification of ethyl acetate and alcoholysis of propylene oxide, and (10) the Tishchenko reaction. The strength of basic sites relevant to different reactions is discussed based on the activity order among alkaline earth oxides, and the optimum pretreatment temperatures of MgO for different reactions. Reactions with hydrocarbons need strongly basic sites, whereas reactions with compounds containing functional groups proceed even on weakly basic sites. Finally, important issues to be investigated for the development of solid base catalysis are pointed out.
A kinetic study in free catalyst transesterification of rapeseed oil was made in subcritical and supercritical methanol under different reaction conditions of temperatures and reaction times. Runs were made in a bath-type reaction vessel ranging from 200°C in subcritical temperature to 500°C at supercritical state with different molar ratios of methanol to rapeseed oil to determine rate constants by employing a simple method. As a result, the conversion rate of rapeseed oil to its methyl esters was found to increase dramatically in the supercritical state, and reaction temperature of 350°C was considered as the best condition, with the molar ratio of methanol in rapeseed oil being 42.
In an attempt to elucidate fundamental problems for synthetic step, and to improve properties of inorganic composite materials by the interaction between inorganic and organic substances, the hydrate of CaO-H2O-CH3OH system was prepared by immersing CaO and Ca (OH) 2 in methanol, and formation mechanism and characteristics of the hydrate were investigated. Firstly the methoxidation of CaO arid Ca(OH)2 in methanol was compared; Both hydration and methoxidation occurred simultaneously in the former case, and Ca (OH) 2 and Ca (OCH3) 2 formed after reacting for 5 h, but in the latter 4 days was necessary to achieve the same state. However there is not any difference between the two cases to reach almost equilibrium state after reacting for 7 days. The (001) spacing of Ca(OH)2 and Ca (OCH3)2, formed in the early stage of immersion, increased or decreased. This fact suggested that the hydrate was mixed with calcium hydroxide methoxides through mutual substitution of OHCH3O group between the both layer of layer structured Ca (OH) 2 arid Ca (OCH3) 2 of Cdl2 type. From X-ray diffractometric analysis, these phases were expressed as formulae of Ca (OH) U5 (OCH3) 0.5 andCa(OH)0,a(OCH3)u. The hydrate crystal containing Ca-OCH3 bond became thin hexagonal plate-like shape with particle size of 2 jum (specific surface area being 2.1 m²/g) as a result of friction of (001) plane in layer structure by immersing in methanol. Moreover, it was proved that carbonation of the hydrate under humidity at 80% was remarkably controlled by the bonded CH30 group on the crystal surface. Also the group was stable at around 300°C by heating. The hydrate of CaO-H2O-CH3OH system fairly dispersed in several organic solvents and then its surface was changed into lipophilic. The hydrate containing Ca-OCH3 bond could be expected as inorganic filler for plastics, rubber and paper.
Transesterification of soybean oil was carried out with methanol over calcium oxide at methanol refluxing temperature, in order to study the application of heterogeneous catalytic process to biodiesel production. The catalyst samples were prepared by calcination of the precipitated calcium carbonate at 900°C in the prescribed atmosphere, an ambient air or a helium gas flow. Calcium oxide prepared in an ambient air catalyzed the transesterification of soybean oil, but yield of the fatty acid methyl esters was only 10% for 4h. The calcination in a helium gas flow markedly intensified the activity of calcium oxide, as the obtained catalyst sample completed the transesterification for 2h. The obtained oil after completing the transesterification had appropriate properties for diesel fuel oil. The active catalyst prepared in a helium gas flow has a higher base strength (15.0 < H_ < 18.4) than the dull one in an ambient air (9.3 < H_ < 15.0). Additionally, the base quantity was 5times larger for the active catalyst. The dull catalyst could be activated by calcination at 300°C in a helium gas flow. The poisoning species in an ambient air was elucidated through the activity test for a series of the catalyst sample obtained by conditioning the partial pressure of CO 2 and moisture in the calcining atmosphere.
Vegetable oils and animal fats can be transesterified to biodiesel for use as an alternative diesel fuel. Conversion of low cost feedstocks such as used frying oils is complicated if the oils contain large amounts of free fatty acids that will form soaps with alkaline catalysts. The soaps can prevent separation of the biodiesel from the glycerin fraction. Alternative processes are available that use an acid catalyst. The objective of this study was to investigate the effect of process variables on acid-catalyzed transesterification. The molar ratio of alcohol, reaction temperature, catalyst amount, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producing biodiesel. Food grade soybean oil was used to prepare esters using excess methanol and sulfuric acid as a catalyst. To compare the effect of different alcohol types on ester formation, methanol, ethanol, 2-propanol, and n-butanol were compared. The American Oil Chemists' Society Method Ca 14-56 was used to measure the biodiesel's total glycerin amount as an indicator of the completeness of the reaction. It was found that acid catalysis can provide high conversion rates but much longer times are required than for alkaline catalysts. The acid catalyst also requires the concentration of water to be less than 0.5%, which is about the same as is required for alkaline catalysts. Water formed by the esterification of free fatty acids limited their presence in the oil to 5%.
Biodiesel has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. The cost of biodiesel, however, is the main hurdle to commercialization of the product. The used cooking oils are used as raw material, adaption of continuous transesterification process and recovery of high quality glycerol from biodiesel by-product (glycerol) are primary options to be considered to lower the cost of biodiesel. There are four primary ways to make biodiesel, direct use and blending, microemulsions, thermal cracking (pyrolysis) and transesterification. The most commonly used method is transesterification of vegetable oils and animal fats. The transesterification reaction is affected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats. The mechanism and kinetics of the transesterification show how the reaction occurs and progresses. The processes of transesterification and its downstream operations are also addressed.
Methyl ester of fatty acids, derived from vegetable oils or animal fats and known as biodiesel, is a promising alternative diesel fuel regarding the limited resources of fossil fuel and the environmental concerns. In this work, an environmentally benign process for the methanolysis of soybean oil to methyl esters using calcined Mg–Al hydrotalcites as solid base catalysts in a heterogeneous manner was developed. When the reaction was carried out at reflux of methanol, with a molar ratio of soybean oil to methanol of 15:1, a reaction time 9h and a catalyst amount 7.5%, the oil conversion was 67%. The calcined hydrotalcite with an Mg/Al ratio of 3.0 derived from calcination at 773K was found to be the optimum catalyst that can give the highest basicity and the best catalytic activity for this reaction. The catalysts were characterized with SEM, XRD, IR, DTA-TG and Hammett titration method. The activity of the catalysts for the methanolysis reaction was correlated closely with their basicity as determined by the Hammett method.
Optimum conditions for a conductometric determination of free lime in industrial products, using alternating current conductometry are elaborated. The analysis of the variation of the conductivity in dependence on concentration in the temperature (°C) range [25–100] allowed the determination of dissociation parameters of calcium glycolate viz. dissociation constant and equivalent conductivity at infinite dilution, which in turn led to the determination of the calcium glycolate concentration from the measured conductivity. The conductometric determination of free lime is only influenced by the presence of SrO. The water content of the solvent (ETG) must not exceed 0.5%.
Nitroaldol reaction of a nitro compound with a carbonyl compound was carried out over a variety of solid base catalysts to elucidate the activity-determining factors in the nature of the catalysts and in the nature of nitro and carbonyl compounds. Among the catalysts examined, MgO, CaO, Ba(OH)2, KOH/alumina, KF/alumina, Sr(OH)2, hydrotalcite, and MgCO3 exhibited high activity for nitroaldol reaction of nitromethane with propionaldehyde, the activities being in this order. Over these catalysts, the yields exceeded 20% at a reaction temperature of 313K and a reaction time of 1h. Mg(OH)2, γ-alumina, SrO, Ca(OH)2, BaCO3, SrCO3, BaO, and La2O3 exhibited moderate activites; the yield were in the range 20–2%. CaCO3, ZrO2, and ZnO scarcely showed the activity. It is suggested that strongly basic sites are not required for the reaction because the abstraction of a proton from a nitro compound is easy.The reactivities of the nitro compounds were nitroethane > nitromethane > 2-nitropropane, and those of carbonyl compounds were propionaldehyde>isobutyraldehyde>pivalaldehyde>acetone>benzaldehyde>methylpropionate. On the basis of IR study of adsorbed reactants and the reactivities of the reactants, the reaction mechanisms are proposed. The reaction proceeds by the nucleophilic addition of the carbanion formed by the abstraction of a proton from nitro compounds to the cationic species formed by the adsorption of carbonyl compounds on the acidic sites (metal cations).The nitroaldol reaction of nitromethane with propionaldehyde over MgO was scarcely poisoned by carbon dioxide and water; nitromethane is so acidic that it is able to be adsorbed on the catalyst on which carbon dioxide or water was preadsorbed.
A promising route for the production of biodiesel (fatty acid methyl esters, FAMES) via transesterification of soybean oil (SBO) and poultry fat with methanol in quantitative conversions at room temperature has been developed using nanocrystalline calcium oxides as catalysts. Under the same conditions, laboratory-grade CaO gave only 2% conversion in the case of SBO, and there was no observable reaction with poultry fat. The soybean oil/methanol ratio in our protocol is 1:27. With our most active catalyst, deactivation was observed after eight cycles with SBO and after three cycles with poultry fat. Deactivation may be associated with one or more of the following factors: the presence of organic impurities or adventitious moisture and enolate formation by the deprotonation of the carbon alpha to the carboxy group in the triglyceride or FAMES. The biodiesel from our protocol meets the ASTM D-874 standard for sulfated ash for both substrates.
Reactions of alcohols with ethyl acetate (transesterification) and propylene oxide were investigated by use of a variety of solid base catalysts to elucidate the activity determining factors of the catalyst in relation with type of alcohol. Solid base catalysts examined were alkaline earth oxides, hydroxides, and carbonates, alumina supported KF and KOH, rare earth oxide, zirconium oxide, etc.Reaction rate of the alcoholysis of ethyl acetate varies with the combination of type of alcohol and basic strength of solid base catalyst. Over strongly basic catalysts such as CaO, SrO, BaO, 2-propanol reacted much faster than methanol. On the other hand, over weakly basic catalysts such as alkaline earth hydroxides, methanol reacted faster than 2-propanol. 2-Methyl-2-propanol reacted only over strongly basic catalysts, and much slower than methanol and 2-propanol.Alcoholysis with propylene oxide was catalyzed only by strongly basic catalysts such as alkaline earth oxides, and KF/alumina, alkaline earth hydroxides scarcely showed activity. γ-Alumina, however, showed a high activity, though the selectivity of products was different from those for alkaline earth oxides. Reactives of alcohols with propylene oxide were in the order, methanol>ethanol>2-propanol>2-methyl-2-propanol, regardless of the type of catalyst.One of the characteristic features observed for both alcoholyses is that the catalysts are tolerant to air exposure, which is caused by strong adsorptivity of alcohol competitive to that of carbon dioxide and water.
Transesterification reaction variables that affect yield and purity of the product esters from cottonseed, peanut, soybean
and sunflower oils include molar ratio of alcohol to vegetable oil, type of catalyst (alkaline vs acidic), temperature and
degree of refinement of the vegetable oil. With alkaline catalysts (either sodium hydroxide or methoxide), temperatures of
60 C or higher, molar ratios of at least 6 to 1 and with fully refined oils, conversion to methyl, ethyl and butyl esters
was essentially complete in 1 hr. At moderate temperatures (32 C), vegetable oils were 99% transesterified in ca. 4 hr with
an alkaline catalyst. Transesterification by acid catalysis was much slower than by alkali catalysis. Although the crude oils
could be transesterified, ester yields were reduced because of gums and extraneous material present in the crude oils.
Transesterification of soybean oil with methanol was carried out at 60, 120, and 150 °C in the presence of a series NaX faujasite zeolite, ETS-10 zeolite, and metal catalysts. The stock zeolites were exchanged with potassium and cesium; NaX containing occluded sodium oxide (NaOx/NaX) and occluded sodium azide (NaOx/NaX*). The catalysts were calcined at 500 °C prior to use in order to increase activity. The ETS-10 catalysts provided higher conversions than the Zeolite-X type catalysts. The increased conversions were attributed to the higher basicity of ETS-10 zeolites and larger pore structures that improved intra-particle diffusion. Methyl ester yield increased with an increase in temperature from 60 to 150 °C. The metal catalysts increased conversion by one to over two orders of magnitude over the homogeneous reaction with several of the zeolite catalysts performing better than the metal catalysts. The catalyst was reused without observed loss of activity. A preliminary design assessment shows that these catalysts are sufficiently active to be commercially viable contingent upon the costs of the catalysts achieving conversions in excess of 90% at temperatures below 125 °C.
Biodiesel fuel, consisting of methyl esters of long chain fatty acids produced by transesterification of vegetable oils or animal fats with methanol, is a promising alternative diesel fuel regarding the limited resources of fossil fuels and the environmental concerns. In this work, an environmentally benign process for the transesterification of soybean oil to methyl esters using alumina loaded with potassium as a solid base catalyst in a heterogeneous manner was developed. The catalyst loaded KNO3 of 35 wt.% on Al2O3, after being calcined at 773 K for 5 h, it was found to be the optimum catalyst, which can give the highest basicity and the best catalytic activity for this reaction. The effects of various reaction variables such as the catalyst loading, oil to methanol ratio, reaction time and temperature on the conversion of soybean oil were investigated. The catalysts were characterized by means of XRD, IR and Hammett titration method. The results indicated that K2O derived from KNO3 at high temperature and that the Al–O–K groups were, probably, the main reasons for the catalytic activity towards the reaction. The catalyst activity was correlated closely with its basicity as determined by the Hammett method.
For biodiesel-fuel production by methanolysis of plant oils, Rhizopus oryzae cells producing a 1,3-positional specificity lipase were cultured with polyurethane foam biomass support particles (BSPs) in a 20 l air-lift bioreactor, and the cells immobilized within BSPs were used as whole-cell biocatalyst in repeated batch-cycle methanolysis reaction of soybean oil. The whole-cell biocatalyst had a higher durability in the methanolysis reaction when obtained from air-lift bioreactor cultivation than from shake-flask cultivation. Following repeated methanolysis reaction using the whole-cell biocatalyst, analysis of the reaction mixture composition indicated that monoglycerides (MGs) decreased and free fatty acids (FFAs) increased with increasing water content in the reaction mixture, and that MGs, diglycerides (DGs), and triglycerides (TGs) increased with increasing number of reaction cycles. The isomers of MGs and DGs generated during the 20th methanolysis reaction cycle consisted of 2-MGs and 1,2(2,3)-DGs, respectively. The hydrolytic activity of the whole-cell biocatalyst, on the other hand, was stable regardless of the number of reaction cycles. It was demonstrated thus that the whole cell biocatalyst promotes acyl migration of partial glycerides, and that the facilitatory effect is increased by increase in the water content of the reaction mixture but it is lost gradually with increasing number of reaction cycles.
Aldol addition of acetone was studied over alkaline earth oxides, La2O3, ZrO2, SiO2Al2O3 and Nb2O5 at 0°C to elucidate the nature of active sites. The activities of catalysts on a unit surface area basis were in the order: BaO > SrO > CaO > MgO > La2O3 > ZrO2 ≫ SiO2Al2O3 > Nb2O5. The reaction is base-catalyzed, and the oxides of stronger basic sites promote the reaction effectively.The effects of preadsorption of water, ammonia, pyridine and carbon dioxide were investigated with MgO and CaO. For MgO, addition of water and ammonia caused marked increase in activity and selectivity to diacetone alcohol, while pyridine had little effect on the catalytic behavior. Preadsorption of carbon dioxide scarcely inhibited the reaction. For CaO, the effects of preadsorption were small compared with those on MgO. Basic OH− ions, which are either retained on the surfaces or formed by dehydration of diacetone alcohol, are proposed as active sites for aldol addition of acetone.
Biodiesel has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. The cost of biodiesel, however, is the main hurdle to commercialization of the product. The used cooking oils are used as raw material, adaption of continuous transesterification process and recovery of high quality glycerol from biodiesel by-product (glycerol) are primary options to be considered to lower the cost of biodiesel. There are four primary ways to make biodiesel, direct use and blending, microemulsions, thermal cracking (pyrolysis) and transesterification. The most commonly used method is transesterification of vegetable oils and animal fats. The transesterification reaction is affected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats. The mechanism and kinetics of the transesterification show how the reaction occurs and progresses. The processes of transesterification and its downstream operations are also addressed.
In this study, transesterification of soybean oil to biodiesel using CaO as a solid base catalyst was studied. The reaction mechanism was proposed and the separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and water content were investigated. The experimental results showed that a 12:1 molar ratio of methanol to oil, addition of 8% CaO catalyst, 65 °C reaction temperature and 2.03% water content in methanol gave the best results, and the biodiesel yield exceeded 95% at 3 h. The catalyst lifetime was longer than that of calcined K2CO3/γ-Al2O3 and KF/γ-Al2O3 catalysts. CaO maintained sustained activity even after being repeatedly used for 20 cycles and the biodiesel yield at 1.5 h was not affected much in the repeated experiments.
Conjugate addition of methanol to 3-buten-2-one to form 4-methoxy-butan-2-one proceeds effectively over the solid base catalysts such as alkaline earth oxides, strontium hydroxide, barium hydroxide, and alumina supported potassium fluoride and hydroxide at a reaction temperature of 273 K. The catalytic activities of magnesium oxide, calcium oxide, and alumina supported KF catalyst were not much affected by exposure of the catalysts to carbon dioxide or air.
The transesterification reactions of triolein with ethanol using various ion-exchange resin catalysts were conducted to produce ethyl oleate as a biodiesel. The anion-exchange resins exhibited much higher catalytic activities than the cation-exchange resin. The anion-exchange resin with a lower cross-linking density and a smaller particle size gave a high reaction rate as well as a high conversion. By combining the three-step regeneration method, the resin could be repeatedly used for the batch transesterification without any loss in the catalytic activity. A continuous transesterification reaction was carried out using an expanded bed reactor packed with the most active resin. The reactor system permitted the continuous production of ethyl oleate with a high conversion.
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