Article

Biocatalyzed Acetins Production under Continuous-Flow Conditions: Valorization of Glycerol Derived from Biodiesel Industry

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Abstract

The use of glycerol derived from biodiesel industry is an important development to add value to this actual waste. Several products can be obtained from glycerol, but acetins are very interesting molecules with a wide range of applications in pharmaceutical, cosmetics, food, and fuel industry. Herein we report our results on biocatalyzed batch and continuous-flow process for valorization of glycerol derived from biodiesel industry towards acetin production. Excellent results can be obtained with different selectivities depending on the nature of glycerol used and reaction conditions being able to produce monoacetin, diacetin, or triacetin depending on the reaction condition.

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... residence time) selectively provided the corresponding monoacetate with a good selectivity [26]. As compared to chemical catalyzed processes, the biocatalysed production of acetins under continuous flow conditions has also been reported [27]. Starting from ethyl acetate and vinyl acetate as acyl donors, the selectivity toward acetins was found to be dependent on residence time and temperature. ...
... The temperature (RT and 60?C) did not significantly affect mono-, di-and triacetins distribution. As expected, monoacetin yield increased at increasing flow rates, reaching a maximum of 37% (3 mL.min -1 , 0.8 min residence time) [27] . Comparatively , the use of vinyl acetate at RT exclusively provided diacetin as reaction product. ...
... Novozyme 435 and selectivity towards diacetin, irrespective of the employed acyl donor [27]. Importantly, the scope of the reaction was also extended to the valorization of crude glycerol (GlyBio) from a biodiesel company [27]. ...
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Glycerol conversion to valuable products has been a research avenue that attracted a significant interest in recent years due to its large available volumes (as by-product of biodiesel production) and the different possibilities for chemical and biological conversion into high added value chemicals profiting from the unique presence of three hydroxyl groups in its structure. The utilization of continuous flow processes in combination with transformation of platform chemicals (e.g. glycerol) can offer several advantages to batch processes in view of their potential implementation in industry. This minireview has been aimed to highlight most recent key continuous flow systems for glycerol valorization to valuable products using different types of catalysts and processes.
... The acetate donor should not affect the lipase stability and should be able to react at a moderate temperature. A variety of acetate donors are used for the trans-esterification reaction converting glycerol to acetins, including acetic acid, vinyl acetate, ethyl acetate, acetic anhydride, and methyl acetate [21]. Among different acetate donors, methyl acetate is a well-known stable material for lipase activity [106]. ...
... The immobilized lipase from Candida antarctica resulted in the highest efficiency by producing a mixture of fatty acid esters and triacetin with a conversion rate of 80% [104]. The highest conversion rate was achieved with Novozym 435 from Candida antarctica immobilized on acrylic resin [21]. Unlike traditional chemical synthesis, there are several advantages to using lipases for acetins synthesis, such as lower energy requirements, less waste generation, higher quality and purer products, higher stability of catalysts (Novozym 435 can be reused more than 100 times), eco-friendliness, and no hazardous chemicals [104,[116][117][118]. ...
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To utilize excess glycerol produced from the biodiesel industry, researchers are developing innovative methods of transforming glycerol into value-added chemicals. One strategy adopted is the conversion of glycerol into acetins, which are esters of glycerol that have wide applications in cosmetics, pharmaceuticals, food and fuel additives, and plasticizers and serve as precursors for other chemical compounds. Acetins are synthesized either by traditional chemical methods or by biological processes. Although the chemical methods are efficient, productive, and commercialized, they are “non-green”, meaning that they are unsafe for the environment and consumers. On the other hand, the biological process is “green” in the sense that it protects both the environment and consumers. It is, however, less productive and requires further effort to achieve commercialization. Thus, both methodologies have benefits and drawbacks, and this study aims to present and discuss these. In addition, we briefly discuss general strategies for optimizing biological processes that could apply to acetins production on an industrial scale.
... By means of etherification (Scheme 3), on the other hand, it was possible to obtain alkylglycerol ethers which were widely used in the pharmaceutical field for their antiinflammatory [20], antibacterial [21], antifungal [22], anticancer [23], and immune system stimulant properties [24]. Costa explored acetins, mono-, di-, glycerol triacetates used as solvents, gelatinizers for explosives and perfume fixers, obtained by inserting a mixture of glycerol and acyl donor in the presence of appropriate enzymes (Scheme 4) [25]. Depending on the acyl donor, a greater selectivity towards mono-, di-, triacetin occurred. ...
... Hydrogenation of glycerol to 1-and 2-biopropanol in a continuous process Costa used a 50 mL tube equipped with a stirring bar operating throughout the process to obtain the conversion of glycerol into mono-, di-, and triacetin. [25] An Asia Flow Reactor was equipped with an Omnifit column containing a lipase. The conditions of 60 °C and a flow rate of 0.4-3.0 ...
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Glycerol is a valuable by-product in the biodiesel industries. However, the increase in biodiesel production resulted in an excess production of glycerol, with a limited market compared to its availability. Precisely because glycerol became a waste to be disposed of, the costs of biodiesel production have reduced. From an environmental point of view, identifying reactions that can convert glycerol into new products that can be reused in different applications has become a real necessity. According to the unique structural characteristics of glycerol, transformation processes can lead to different chemical functionalities through redox reactions, dehydration, esterification, and etherification, with the formation of products that can be applied both at the finest chemical level and to bulk chemistry.
... They can also be used as an antiknock additive for gasoline. Acetins also find applications as plasticizer, food additive, and solvent in leather tanning industries, as well as in the manufacture of explosives and biodegradable polyesters (Costa et al., 2013). ...
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... The acetylation procedure carried out using acetic acid as the acylating agent leads to the formation of various acetyl esters of glycerol and generally requires higher temperatures and a high acetic acid/glycerol ratio [33]. Acetic acid consumption and product purification has been optimized using several continuous processes based on distillation as reported in many studies [49][50][51][52]. ...
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Crude glycerol is the main by-product of many renewable diesel production platforms. However, the process of refining glycerol from this crude by-product stream is very expensive, and thus does not currently compete with alternative processes. The acetylation of glycerol provides an intriguing strategy to recover value-added products that are employable as fuel additives. In this work, the conversion of glycerol to acetyl derivatives was facilitated by a heterogeneous catalyst generated from the thermal hydrolysis of biosolids obtained from a municipal wastewater treatment facility. The reaction was studied using several conditions including temperature, catalyst loading, acetic acid:glycerol molar ratio, and reaction time. The data demonstrate the potential for using two distinct by-product streams to generate fuel additives that can help improve the process economics of renewable diesel production.
... It is still not clear how these metabolites develop during the production process. For instance, acetin might be a contaminant from the production instruments, as it is widely used as a fuel additive [39]. Similarly, 1,3-diacetoxyporpane (also known as 1,3-propanediol-diacetate) is also used in combustion engines [40]; therefore, it also might be an equipment-derived contaminant. ...
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A series of γ-Al2O3 supported silvercatalysts (Ag/Al2O3) prepared with various Ag loadings and calcination temperatures were used to convert glycerol to 1,2-propanediol. A catalyst with 2 mmol Ag per gram Al2O3 and calcined at 400–500 °C presented the highest activity (glycerol conversion 46 mol%) and selectivity (96 mol%) at 220 °C, glycerol/Ag (molar ratio) = 100/2, 1.5 MPa initial H2 pressure and 10 h. Optimal prereduction, elevated reaction temperature and hydrogen pressure promote the activity, but the selectivity deteriorates at higher reaction temperatures. Excessive water is detrimental to the performance. Catalyst deactivation was observed, mainly due to Agsintering under reducing environment. The spent catalyst could be calcined to fully recover the activity.
Article
At T ≥ 200 °C, in the presence of K2CO3 as a catalyst, an original etherification procedure of non-toxic acetals such as glycerol formal (GlyF) and solketal has been investigated by using dialkyl carbonates as safe alkylating agents. The effects of parameters including the temperature, the reaction time, and the loading of both the catalyst and the dialkyl carbonate have been detailed for the model case of dimethyl carbonate (DMC). Both GlyF and solketal were efficiently alkylated by DMC to produce the corresponding O-methylethers with selectivity up to 99% and excellent yields (86–99%, by GC). The high selectivity could be accounted for by a mechanistic study involving a combined sequence of methylation, carboxymethylation, decarboxylation and hydrolysis processes. The O-methylation of GlyF and solketal could be successfully scaled up for multigram synthesis even operating with a moderate excess (5 molar equiv.) of DMC and in the absence of additional solvent. Notwithstanding the advantageous reduction of the process mass index, scale up experiments provided evidence that prolonged reaction times may induce the decomposition of DMC mainly by the loss of CO2. The K2CO3-catalyzed etherification of solketal with other carbonates such as dibenzyl and diethyl carbonate (DBnC and DEC, respectively), proceeded with the same good selectivity observed for DMC. However, at 220 °C, the solketal conversion did not exceed 81% since both DBnC and DEC were extensively consumed in competitive decarboxylation and hydrolysis reactions.
Article
Commercially available partly acetylated glycerols (mono- and diacetin) are mixtures of glycerol, 1- and 2-acetylglycerol, 1,2- and 1,3-diacetylglycerol, and triacetin. Diacetin and monoacetin are by-products of the biodiesel and triacetin production using glycerol esterification with acetic acid or triglyceride interesterification with methyl acetate. Usually, primary analytical methods involve chromatography (HPLC or GC), spectroscopy (MS or NIR), and wet chemical techniques (potentiometric, iodometric titration) which are often time-consuming due to sample preparation, extended analysis time and/or complicated data analysis. Moreover, these methods require pure mono- and diacetin as standard, which are commercially unavailable. In this work, a complete 31P and 13C chemical shift data for glycerol, mono-, di- and triacetin (including isomers) allows for the identification and quantification of these components in the commercial mixtures. This experimental protocol allows for rapid analysis of mixtures that include these six components. Quantitative 31P NMR and 13C NMR results were validated to those obtained with other analytical methods, such as GC and HPLC-ELSD. 13C NMR is preferred due to allows to measure the content of triacetin, which has no free hydroxyl group, and no signal was detected by 31P NMR.
Article
Dehydration of glycerol was carried out using rubidium and caesium doped silicotungstic acid catalysts. These catalysts were prepared by varying the concentration of the dopant metal cations while keeping the concentration of heteropoly acid unchanged. High acrolein selectivity (94-96 %) was observed with unsupported caesium-doped silicotungstic acid and rubidium-doped silicotungstic acid with a dilute glycerol feed (0.5 wt. % in water). These catalysts were then supported on alpha alumina and an alumina comprising a theta-delta mixture. Caesium-doped silicotungstic acid supported on theta-delta alumina gave a maximum selectivity of ca. 90 % at 100 % glycerol conversion for 90 h time on line, with a 10 wt. % glycerol solution. With a more concentrated glycerol feed (20 wt. %) the this catalyst achieved a space time yield of 210 g(acrolein)kg(cat)-1h-1. The catalyst was investigated further to determine the origin of the long-term stability. The binding strength of the partially doped silicotungstic acid on the alumina was found to be crucial to sustain the supported Keggin structure and hence the acidity of the active sites resulting in a high acrolein yield.
Article
In the last few years, the increasing production of biodiesel has led to an overproduction of glycerol, the main byproduct of this industry. This paper reports on the ketalization of glycerol in supercritical acetone to give solketal (4-hydroxymethyl-2,2-dimethyl-1,3-dioxolane), an oxygenated compound useful as chemical and fuel additive for gasoline, diesel and biodiesel. The application of supercritical fluids (SCFs) in the chemical synthesis was explored to carry out reactions to obtain the above cyclic ketal. The experimental results reveal a drastic change in the reaction behavior when the critical condition of acetone is reached (T=508K). Below 508K the reaction rate of solketal production is very low, but above this temperature a rapid increase in the reaction rate is observed. Finally, the reaction rate is stabilized at 533K and higher temperatures due to the conversion of glycerol to acrolein and polymeric products as side reactions.
Article
High dependence on fossil fuel has caused increase of carbon dioxide concentration in the atmosphere. The actual political trends are towards an increased use of renewable fuels from agricultural origin. One of the main products of the European biorefineries is biodiesel. The main reaction involved in biodiesel synthesis produces a large amount of glycerol as by-product. Two aspects are arising in this respect: the glycerol obtained as residue and the food conversion to fuel. This paper deals with the revalorization of the residual glycerol stream to obtain triacetin (glyceryl triacetate), the lightest comestible oil. The application of glycerol as raw material to produce triacetin is not new. The goal of this paper is to check the feasibility of this transformation in an efficient integrated continuous process which is suitable for processing high quantities of glycerol. A kinetic model was determined experimentally for the production of triacetin from glycerol and acetic acid in the absence of catalyst. The results showed that by process integration of the reaction and distillation in the same unit (reactive distillation), a more sustainable process can be developed. The proposed configuration output is checked by rigorous simulation.
Article
In this study, the hydrolysis of triacetin by Candida cylindracea Lipase was investigated in a recirculating column reactor containing polyethylene particles. Lipase is known to show a high activity at the oil-water interface, but its activity in a homogeneous phase such as in the soluble triacetin-water system is very low. For this reason, non-porous polyethylene particles were used as an adsorbent packing material in a column reactor to create an interface for soluble concentrations of triacetin. Triacetin is adsorbed from the aqueous solution on the surface of the polyethylene particles and then hydrolyzed by lipase. The variation in the hydrolysis reaction rates with triacetin concentration in both water soluble and insoluble regions was investigated. This was done with and without polyethylene particles that were 128 μm, 200 μm and 378 μm in size. The comparison of the results shows that the inert polyethylene particles provide an increase of between 88–431% in the hydrolysis rate of triacetin for the different soluble concentrations. Another important result obtained in this study was that all apparent Michaelis constants for the cases with particles were smaller than that of a reference state without particles.
Article
The acetalisation of glycerol was studied using heteropolyacids, immobilized in silica, as catalysts, at 70°C. The main product of glycerol acetalisation was solketal. The tungstophosphoric (PW), molybdophosphoric (PMo), tungstosilisic (SiW) and molybdosilisic (SiMo) acids were immobilized in silica by sol–gel method.It was observed that the catalytic activity decreases in the series: PW_S>SiW_S>PMo_S>SiMo_S. All catalysts exhibited good values of selectivity to solketal (about 98% near complete conversion). The effect of different parameters, such as catalyst loading, molar ratio of glycerol to acetone and temperature on the glycerol acetalisation, over PW_S catalyst, was studied. Catalytic stability of the PW_S, SiW_S, PMo_S and SiMo_S catalysts was evaluated by performing consecutive batch runs with the same catalyst sample. After the third batch, it was observed a stabilisation of the initial activity.
Article
Converting renewable carbon to chemicals and fuels is experiencing a huge increase in both research and commercial interest. The biorefinery is now a recognized approach for transforming renewable raw materials into separate biobased process streams, and ultimately, marketplace chemicals and fuels. Successful biorefinery operation will fulfill two strategic goals: displacing nonrenewable raw materials (an energy goal, met by production of biofuels) and providing economic incentive to support a robust biorefining industry (an economic goal, met by the production of high value chemicals). These goals are met simultaneously by integrating chemical and fuel production within a single operation. However, a primary barrier to biorefinery development is the relative lack of technology available for the conversion of renewable carbon sources into useful marketplace chemicals and materials. Developing broad based technologies capable of producing families of high value chemicals will provide a significant opportunity for the biorefinery. This introductory paper briefly overviews the biorefinery concept and describes several features of biorefinery operation and technology needs for the production of chemicals from renewable raw materials.
Article
Continuous esterification of glycerol with acetic acid was investigated in supercritical carbon dioxide (scCO2) using Amberlyst 15® as a heterogeneous catalyst. The effect of pressure at (65–300) bar on the substrate conversion and the reaction yield and selectivity was studied. With increasing pressure, the percent of total yield and conversion remain almost unaffected and the selectivity of monoacetin synthesis increases while the selectivity for triacetin stays relatively unchanged. The effect of temperature on the yield, conversion, and the selectivity at (100–150) °C was also investigated. With increasing temperature from 100 to 140 °C, the selectivity for monoacetin decreases while for tri- and diacetin slightly increases. In contrast, with further increase in temperature, from 140 °C to 150 °C, the selectivity of monoacetin synthesis increases while that of diacetin decreases. By increasing the molar ratio of acetic acid to glycerol to 24, a selectivity of 100% was achieved for 2 h while the yield was 41% for the continuous triacetin synthesis in scCO2. When neat scCO2 as solvent with no catalyst was used, only monoacetin with 29% conversion was synthesized. The catalyst durability was also studied by monitoring the reaction for 25 h. The results show that the catalyst retains its activity even for 25 h but the selectivity for triacetin synthesis declines from 100% to about 60%.
Article
Sulfonic acid-functionalized mesostructured silicas have demonstrated excellent catalytic behaviour in the acetalisation of glycerol with acetone to yield 2,2-dimethyl-1,3-dioxolane-4-methanol, also known as solketal. This molecule constitutes an excellent compound for the formulation of gasoline, diesel and biodiesel fuels. The activity achieved with arenesulfonic acid-functionalized silica is comparable to that displayed by Amberlyst-15. Optimal production of solketal over arenesulfonic acid mesostructured silica has been established for a reaction system consisting of three consecutive 2-step batches (30 min under reflux and an evaporation step under vacuum), and using a 6/1 acetone/glycerol molar ratio. The use of lower grades of glycerol, such as technical (purity of 91.6 wt%) and crude (85.8 wt%) glycerol, has also provided high conversions of glycerol over sulfonic acid-modified heterogeneous catalysts (84% and 81%, respectively). For refined and technical glycerol the catalysts have been reused, without any regeneration treatment, up to three times, keeping the high initial activity. However, the high sodium content in crude glycerol deactivates the sulfonic acid sites by cation exchange. This deactivation is readily reversed by simple acidification of the catalyst after reaction.
Article
a b s t r a c t Recognition that trans and saturated fats have negative health effects drive researchers to develop alternative systems that can structure liquid oils into semi-solid plastic pastes for food applications. Monoacylglicerols (MAG) can be used as a promising molecule to achieve this structuring so we have optimized a biocatalytic batch process to the esterification reaction between 1,2-O-isopropylidene glyc-erol and stearic acid, catalyzed by Lipozyme RM IM, using response surface methodology (RSM) in a laboratory setting with 95% of conversion after 4 h.
Article
Silica immobilized lipases have been prepared and utilized in the valorization of fatty acid-derived food waste streams under continuous flow conditions. Findings demonstrate that better conversions could be obtained when compared with commercially available immobilized enzymes.
Article
Free fatty acids are used in many cases for the production of soaps, candles and assist processing of rubber products, but we believe that new process technology should be developed to produce products with higher added value. Monoacylglycerols (MAGs) are nonionic surfactant, highly hydrophobic and has been used as controlled release systems for drugs. The results presented here for the lipase-catalyzed MAG production show that both batch and continuous flow conditions can lead to the desired product in short reaction time and high yield (70–95%) but the use of packed bed reactors (PBR) shows higher efficiency when compared to batch reactors.
Article
Diacylglycerols (DAG) are commonly used in different purity levels for food, medicine and cosmetic industries. Several approaches are found over the literature on DAG production under lipase-catalyzed reactions among which are highlighted: glycerol sterification, vegetable oils’ glycerolysis and selective hydrolysis. Results obtained palm oil partial hydrolysis catalyzed by PS Amano IM under microwave irradiation show that DAG can be produced through short-term reactions and moderated yields (5min, 30%). The DAG production using packed bed reactors under conventional heating and continuous flow conditions is more efficient allowing us to produce 128g in 24h with flow rate as a key feature.
Article
Biodegradable, biocompatible and nontoxic nonionic surfactants are widely used in food, pharmaceutical and industrial applications being commonly produced based on alkaline-catalyzed chemical glycerolysis of natural oil and fats at high temperatures and elevated pressure under nitrogen atmosphere. In this work we have optimized a biocatalytic continuous flow process with packed bed reactor for the esterification reaction between (R,S)-1,2-isopropylidene glycerol and stearic acid using response surface methodology (RSM) leading to the desired product in excellent conversion (95%) and short reaction time (40 s of residence time).
Article
A conductimetric method has been applied to measure lipase activity. When using triacetin as a substrate, a linear relationship between initial rate and enzyme concentration is demonstrated up to 600 U in the cell (4 ml). Kinetic parameters of triacetin hydrolysis have been derived from conductimetric data, in the concentration range of solubility of the substrate. The limiting parameters (temperature, choice of buffer, substrate) are discussed in the last part.
Article
Expected increasing biodiesel production during the next few years will lead to an overproduction of glycerol, which is the main byproduct. The use of glycerol-based additives to improve petrol fuel properties is one of the possibilities currently being explored to utilize this renewable feedstock. In this context, sulfonic acid functionalized mesostructured materials have demonstrated an excellent catalytic behavior in the esterification of glycerol with acetic acid to yield acetylated derivates. Diacetylglycerol (DAG) and triacetylglycerol (TAG, also called triacetin) have been shown to be valuable petrol fuel additives leading to either enhanced cold and viscosity properties when blended with diesel fuel or antiknocking properties when added to gasoline. The activities and selectivities achieved using sulfonic acid functionalized mesostructured materials as catalysts are comparable or even superior to those displayed by conventional acid catalysts, providing values up to 90% of glycerol conversion and over 80% of combined selectivity toward DAG and TAG after 4 h of reaction. The acid strength of the sulfonic acid site has also been found to be an important factor affecting the catalytic performance of these materials. Moreover, these sulfonated mesostructured materials have been reused in repeated catalytic runs after a mild solvent-washing regeneration step yielding similar catalytic performance to that of the fresh catalyst.
Article
The synthesis of novel poly(butylene dodecanoate)s containing different percentages of glycerol was successfully carried out. The polyesters are characterized by branched or cross-linked molecular structures, according to the glycerol content. The modification of the linear backbone of the poly(butylene dodecanoate) increases the rigidity and induces significant changes in the polymer behavior toward photodegradation with respect to UV irradiation. Such a result could be very significant for specific outdoor applications of the novel polyesters.
Article
Interesterification in isooctane with triacetin as an acyl donor was found to be a new and effective method of racemic resolution of d,l-menthol, when using the free and immobilized lipase of Candida cylindracea. No water was produced by this highly stereoselective type of reaction in contrast to ester synthesis with acetic acid as an acyl donor. Even with diacetin no possible back reaction occurred and the enzyme was easily separated from the reaction solution as opposed to ester hydrolysis in aqueous systems. Inhibition of interesterification was caused by increasing concentrations of the acyl donor triacetin by more than 10 mmoll-1 on the one hand, and especially by diacetin on the other hand. The reaction product menthyl acetate had no influence. By adding water the interesterification activity of the lipase was reduced significantly. An alteration of the acyl donor triacetin to longerchained triglycerides caused changes in higher specific activities but poor enantioselectivities of the products, as in the case of ester synthesis starting from longer-chained organic acids.
Article
Characterization of crude glycerol is very important to its value-added conversion. In this study, the physical and chemical properties of five biodiesel-derived crude glycerol samples were determined. Three methods, including iodometric-periodic acid method, high performance liquid chromatography (HPLC), and gas chromatography (GC), were shown to be suitable for the determination of glycerol content in crude glycerol. The compositional analysis of crude glycerol was successfully achieved by crude glycerol fractionation and characterization of the obtained fractions (aqueous and organic) using titrimetric, HPLC, and GC analyses. The aqueous fraction consisted mainly of glycerol, methanol, and water, while the organic fraction contained fatty acid methyl esters (FAMEs), free fatty acids (FFAs), and glycerides. Despite the wide variations in the proportion of their components, all raw crude glycerol samples were shown to contain glycerol, soap, methanol, FAMEs, water, glycerides, FFAs, and ash.
Article
Acrolein is an important chemical intermediate for many common industrial chemicals, leading to an array of useful end products. This paper reviews all the synthetic methods, including the former (aldol condensation) and contemporary (partial oxidation of propylene) manufacturing methods, the partial oxidation of propane, and most importantly, the bio-based glycerol-dehydration route. Emphasis is placed on the petroleum-based route from propylene and the bio-based route from glycerol, an abundantly available and relatively inexpensive raw material available from biodiesel production. This review provides technical details and incentives for industrial proyduction that justify a transition toward bio-based acrolein production.
Article
Acetylation of glycerol with acetic acid was investigated over ZrO2, TiO2–ZrO2, WOx/TiO2–ZrO2 and MoOx/ TiO2–ZrO2 solid acid catalysts to synthesize monoacetin, diacetin and triacetin having interesting applications as bio-additives for petroleum fuels. The prepared catalysts were characterized by means of XRD, BET surface area, ammonia-TPD and FT-Raman techniques. The effect of various parameters such as reaction temperature, molar ratio of acetic acid to glycerol, catalyst wt.% and time-on-stream were studied to optimize the reaction conditions. Among various catalysts investigated, the MoOx/TiO2–ZrO2 combination exhibited highest conversion (~100%) with best product selectivity, and a high time-on-stream stability.
Article
The effect of the immobilization protocol and some experimental conditions (pH value and presence of acetonitrile) on the regioselective hydrolysis of triacetin to diacetin catalyzed by lipases has been studied. Lipase B from Candida antarctica (CALB) and lipase from Rhizomucor miehei (RML) were immobilized on Sepabeads (commercial available macroporous acrylic supports) activated with glutaraldehyde (covalent immobilization) or octadecyl groups (adsorption via interfacial activation). All the biocatalysts accumulated diacetin. Covalently immobilized RML was more active towards rac-methyl mandelate than the adsorbed RML. However, this covalent RML preparation presented the lowest activity towards triacetin. For this reason, this preparation was discarded as biocatalyst for this reaction. At pH 7, acyl migration occurred giving a mixture of 1,2 and 1,3 diacetin, but at pH 5.5, only 1,2 diacetin was produced. Yields were improved at acidic pH values and in the presence of 20% acetonitrile (to over 95%). RML immobilized on octadecyl Sepabeads was proposed as optimal preparation, mainly due to its higher specific activity. Each enzyme preparation presented very different properties. Moreover, changes in the reaction conditions affected the various immobilized enzymes in a different way.
Article
A new fuel additive, namely solketal tert-butyl ether (STBE), was developed and optimized under continuous flow conditions using a Corning® Advanced-Flow™ glass reactor. STBE was obtained in two steps from glycerol, a renewable building-block produced in large amount in the processing of biodiesel. The advantages of the highly engineered Corning glass reactor included high mixing and heat-exchange efficiency, chemical resistance under corrosive flow conditions and a small hold-up. A robust, continuous, green and safe industrial-scale process is described.
Article
Utilization of excess glycerol supplies derived from the burgeoning biodiesel industry has recently become very important. Glyceric acid (GA) is one of the most promising glycerol derivatives, and it is abundantly obtained from glycerol by a bioprocess using acetic acid bacteria. In this study, a novel branched-type poly(lactic acid) (PLA) was synthesized by polycondensation of lactide in the presence of GA. The resulting branched PLA had lower crystallinity and glass transition temperatures than the conventional linear PLA, and the peak associated with the melting point of the branched PLA disappeared. Moreover, in a blend of the branched polymer, the crystallization of the linear PLA occurred at a lower temperature. Thus, the branched PLA containing GA synthesized in this study could potentially be used as a novel bio-based modifier for PLA.
Article
Fuels derived from biobased materials are attracting attention for their potential in securing the energy supply and protecting the environment. In this Minireview, we evaluate the use of biobased sources, particularly fatty acids and triglycerides from seed oils and animal fats, as fuels. The physical and chemical properties of these fatty acids and triglycerides are discussed, including the link to their sources and current availability to meet fuel demands. The current technologies, also known as the first-generation ones, for converting triglycerides into fuels are covered, including conventional methods such as transesterification, pyrolysis, cracking, and emulsions. Recent, second-generation technological developments that lead to more commercially viable biofuels based on diesel-like hydrocarbons are also discussed.