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Biocatalyzed Acetins Production under Continuous-Flow Conditions: Valorization of Glycerol Derived from Biodiesel Industry
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.
... 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]. ...
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]. ...
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 ...
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). ...
Highly stable and active CeO2-ZrO2 metal oxide catalyst was synthesized via the combustion method and was further functionalized with sulphate (SO42-) groups. The morphology, surface functionalities, and composition of the metal oxide catalyst were determined by scanning electron microscopy, N2 adsorption and desorption measurement, X-ray diffraction, and Fourier transform infrared spectroscopy. The synthesized catalyst was used for esterification of glycerol with acetic acid. Effects of the process parameters including acetic acid to glycerol molar ratios (3-20), catalyst loadings (1-9 wt.%) and reaction temperatures (70–110°C) on the glycerol conversion and glycerol acetates selectivity were studied. Excellent catalytic activity was observed by using the sulphated metal oxide catalyst resulting in a glycerol conversion as high as 99.12%. The selectivity towards the di and triacetin (fuel additive) formed stood at 57.28% and 21.26% respectively. The reaction rate constants and activation energies were also estimated using a Quasi-Newton algorithm, namely Broyden’s method and Arrhenius equations at 80-110℃. The calculated values were in accordance with the experimental values which confirmed the model. Finally, the developed catalyst could be reused for three consecutive cycle without major loss of its activity. Overall, the findings presented here could be instrumental to drive future research and commercialization efforts directed toward biodiesel glycerol valorisation into fuel additives.
... 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]. ...
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. ...
Balsamic vinegar is a popular food condiment produced from cooked grape must by two successive fermentation (anaerobic and aerobic) processes. Although many studies have been performed to determine the composition of major metabolites, including sugars and aroma compounds, no study has been undertaken yet to characterize the comprehensive metabolite composition of balsamic vinegars. Here, we present the first metabolomics study of commercial balsamic vinegars by gas chromatography coupled to mass spectrometry (GC-MS). The combination of three GC-MS methods allowed us to detect >1500 features in vinegar samples, of which 123 metabolites were accurately identified, including 25 amino acids, 26 carboxylic acids, 13 sugars and sugar alcohols, four fatty acids, one vitamin, one tripeptide and over 47 aroma compounds. Moreover, we identified for the first time in vinegar five volatile metabolites: acetin, 2-methylpyrazine, 2-acetyl-1-pyroline, 4-anisidine and 1,3-diacetoxypropane. Therefore, we demonstrated the capability of metabolomics for detecting and identifying large number of metabolites and some of them could be used to distinguish vinegar samples based on their origin and potentially quality.
The main aim of the present research is to simulate a new thermally coupled micro-reactor which simultaneously produces hydrogen and aniline. It has been suggested that the nitrobenzene hydrogenation process, the heat source, occurs in the tube section, thereby providing the requisite energy for the reactor system. Conversely, the shell section contains the steam reforming of glycerol—coolant for the exothermic reaction. The results are evaluated in the two flow directions, co-current and counter-current. The furnace and cooling system, vital for the conventional steam reforming and aniline production processes, are eliminated, respectively. having meticulously implemented the sensitivity analysis, the optimization of the most effective parameters has been done via the genetic algorithm.
The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C2 to C6 bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.
This review intends to provide the reader with a clear and concise overview of how preparative continuous flow organic chemistry could potentially impact on current important societal challenges. These societal challenges include health/well-being and sustainable development. Continuous flow chemistry has enabled significant advances on continuous flow manufacturing of pharmaceuticals, as well as on biomass valorization toward a biosourced chemical industry. Examples related to pharmaceutical production are herein focused on (a) the implementation of flow chemistry to reduce the occurrence of drug shortages, (b) continuous flow manufacturing of orphan drugs and (c) continuous flow preparation of active pharmaceuticals listed on the WHO list of essential medicines. Examples related to sustainable development are focused on the valorization of biosourced platform molecules. Besides positive impacts on societal challenges, this review also illustrates some of the potentially most threatening perspectives of continuous flow technology within the actual context of terrorism and drug abuse.
Glycerol, a byproduct of biodiesel process, further adds more bioderived feedstocks to the scenario. Catalytic approach becomes interested in glycerol conversion to modify its rate, thermodynamic, and time scale reaction. Many examples of catalytic applications of metal, metal oxide, bimetallic, acid, base, ionic liquid, and the enzyme are documented, but development of the field has been hampered by the lack of a conceptual approach and understanding of the real conversion mechanism. The main core of this paper is to highlight catalytic reactivity on different kinds of catalysis in oxidation, dehydration, acetylation, etherification, esterification, acetalization, ammoxidation, and enzymatic process of glycerol conversion. The productions of different types of chemical value-added of citric acid, lactic acid, 1,3-dihydroxyacetone, 1,3- propanediol, dichloro-2-propanol, acrolein, hydrogen, and ethanol are consequently demonstrated. The key aspect, characterization, and synthesis mechanism of each glycerol conversion is highlighted, which consequently demonstrate the synthesis strategy on controlling of product selectivity and yield.
This chapter demonstrates with a wide range of examples the high potential of continuous-flow techniques for stereoselective biotransformations catalyzed by enzymes, especially hydrolases. Benefits of the various reactor setups are discussed, for example, the continuous flow packed bed reactors can enhance the productivity of enzyme-catalyzed processes or miniaturized continuous flow systems allow fast high-throughput screenings. Continuous flow microreactor systems enabled integration of enzyme-catalysis with chemical steps (e.g., in dynamic kinetic resolutions) or with continuous extraction or performing multienzyme-catalyzed multistep biotransformations. Thus, the potential of continuous-flow microreactor systems with immobilized biocatalysts is demonstrated as process development tool for stereoselective biotransformations.
In this work, a three-step chemo enzymatic cascade reaction is reported for 1-monoacylglycerols from glycerol derived from biodiesel industry under continuous-flow conditions. Glycerol protection was performed using H 2 SO 4 /SiO 2 (2.5 %w/v) solid catalyst and acetone, generating 87 % of solketal under 55 °C at 0.1 mL/min with glycerol–acetone ratio of 1.5:1. Coupled esterification between the formed solketal and stearic acid catalyzed by Rhizomucor miehei enzyme (RM IM) was able to maintain 90 % of conversion until 1.5 M of substrate concentration at 0.1 mL/min flow rate and could be recycled up to 18 times. Final ketal cleavage was performed with the same H 2 SO 4 /SiO 2 solid catalyst and the amount of water generated in the esterification reaction, whereas a flow rate of 0.2 mL/min was the best condition where the formation of 1-monoacylglycerol was maximized and byproducts were not detected.
Consequence of an important increase in world biodiesel production, in the last decade the level of glycerol offered on the market exceeded the consumption rate. Beside its classical utilizations, particularly in pharmaceutical and food industries, glycerol emerges as an important renewable chemical that can be transformed into medium tonnage chemical products, replacing petroleum based intermediates. An important category of processes for glycerol conversion into value added chemicals are based on heterogeneous catalysis. This paper reviews the main research works investigating the glycerol transformation into two chemical products of industrial importance: propanediols and acrolein. Even if, on short term, these researches do not have an obvious economical impact, they certainly present an important potential for the future, when new feedstocks and processes will have to replace actual petroleum based products and technologies.
A cerium-doped FePO4 catalyst dehydrates glycerol to acrolein in the gas phase but carbon accumulation reduces the reaction rate with time. Reaction rates may be maintained for longer times by co-feeding low concentrations of oxygen together with the glycerol, but the acrolein yield drops proportionally to the oxygen concentration. The catalyst is easily regenerated by air and the reaction rate is proportional to both the oxygen concentration and quantity of carbon. The carbonaceous deposits may be due to both glycerol and acrolein: when either is fed to the catalyst, the CO2/CO ratio is close to 1; during the regeneration step, the CO2/CO ratio is near 4. A kinetic model of first order in both oxygen concentration and adsorbed sites characterizes the transient data very well.
A new catalytic route with potential practical interest to sustainable production of bio-additives from glycerol is described. Ethyl acetate was transesterified with glycerol, in the ratio glycerol:EtOAc 1:10, at 25 or 90 ºC using 0.1 equiv. of H2SO4 or TsOH, as homogeneous catalysts. H2SO4 led to the total glycerol consumption in 2 h. In the equilibrium, attained in 9 h, 100% yield of a diacetin:triacetin (55:45) mixture was formed. Using AmberlystTM 15 dry and AmberlystTM 16 wet in 1:30 glycerol:EtOAc ratio and reflux at 90 ºC the total glycerol consumption was achieved in 2 and 10h, respectively. The lower reactivity of Amberlyst-16 wet was explained in terms of deactivation of acid sites and decrease in glycerol diffusion to the inner resin pores, both factors caused by adsorbed water. The kinetics of glycerol transformation and product distribution in the equilibrium in relation to the H2SO4, Amberlyst-15 (dry) and Amberlyst-16 (wet) catalyzed reactions were measured.
Glycerol is electro-converted to glycolate with 85% selectivity on carbon nanotube supported Au catalyst (Au/CNT) in alkaline electrolyte at 1.6 V (vs. SHE) under mild reaction conditions (room temperature, atmosphere pressure, water as solvent).
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.
The acetalization of acetone with glycerol to yield 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) was successfully catalyzed by mesoporous substituted silicates including the novel Hf-TUD-1 material. This reaction offers an attractive path for the conversion of glycerol, which is the main side-product in the synthesis of biodiesel, to a valuable compound with potential for industrial applications. The most promising among the heterogeneous catalysts employed in this work, Zr- and Hf-TUD-1 and Sn-MCM-41, display mainly Lewis acid properties as demonstrated by characterization with FT-IR analysis of pyridine adsorption, and achieve superior results compared to a reference solid acid catalyst such as Ultrastable zeolite Y. Especially the newly synthesized Hf-TUD-1, showing the highest conversion and turnover among the screened materials, is a promising catalyst for the acetalization of acetone with glycerol in a sustainable process. The excellent performance of these mesoporous catalysts is ascribed to their combination of acidity, wide pores, large specific surface area and relatively hydrophobic surface.
The present Letter details our findings on the lipase-catalyzed Michael reactions between primary or secondary amines and acrylonitrile. Several lipases were evaluated, and good results were obtained leading to the formation of Michael adducts in shorter reaction times than the uncatalyzed reactions.
The present paper describes a protocol for production of diacylglycerol by the partial hydrolysis of soybean oil catalyzed by lipase under ultrasound irradiation. Better yields and shorter reaction times were obtained under sonication as compared to the thermal process.
The selective and continuous production of monoacetin using an expanded-bed column reactor, in which the reactive fluid flows vertically upward and the catalyst is hydrodynamically floated, was studied. Acetic acid and glycerol were used as the substrates and the proton-type cation-exchange resin Amberlyst 16 was used as the catalyst. Batch reaction experiments under various conditions were first conducted to investigate the details of the heterogeneous catalytic reaction mechanism. The esterification of acetic acid with glycerol to produce the target product monoacetin was proved to proceed predominantly over the undesired consecutive esterification reactions to diacetin and triacetin. The intraparticle and extraparticle mass-transfer resistances for the catalytic resin were negligible. The Eley-Rideal-type catalytic reaction model was successfully applied to the experimental data for the various conditions. Next, the hydrodynamic correlation between the flow rate of the reactive fluid and the corresponding expanded-bed height on the continuous reactor was determined experimentally. Furthermore, the reaction and transport model for a continuous expanded-bed column reactor was constructed based on the kinetic model for the batch system. The numerical calculation simulated the experimental data well, and the optimum operating conditions were successfully determined by the theoretical analysis.
Silica-supported silver exhibited high catalytic activity in the dehydration of glycerol: glycerol was dehydrated into hydroxyacetone with the selectivity higher than 86% at 91% conversion over Ag/SiO2 in H-2 flow at 240 degrees C. Silver metal provides an active site and showed stable catalytic activity for the glycerol dehydration in H-2 atmosphere, while the dehydration activity decreased in N-2 atmosphere. The hydrogenation of hydroxyacetone into 1,2-propanediol and the decomposition to ethylene glycol did not proceed over silver.
Supported heteropoly acid catalysts are frequently used in the dehydration of glycerol into acrolein because of their high activity. However, they are easily deactivated by coke that can become deposited on the catalyst surface. Herein, we report a technique that significantly decreases coke formation by capturing coke precursors in a Pd lattice. The Pd-added H3PW12O40/C catalyst (Pd-PWC) showed stable catalytic activity and the amount of deposited coke formed was decreased to about 40 % of that without Pd addition. The catalysts were characterized by XRD, HR-TEM, XPS, NH3-TPD, and TGA methods. These results showed that the palladium lattice on the carbon support was easily loosened and that coking precursors were incorporated into the Pd lattice of the catalyst under the reaction conditions used. Consequently, the amount of coke that was deposited onto the active sites of the catalysts was significantly decreased.
Iridium pincer complex (POCOP)IrH2 (1; POCOP = κ3-C6H3-1,3-[OP(tBu)2]2) catalyzes hydrogenolysis of 1,2-propanediol to n-propanol in good yield under mild conditions (acidic aqueous dioxane, 50–125 °C, 100–600 psi H2). Studies of catalyst speciation revealed that the catalyst reservoir species is (POCOP)Ir(CO) (2), formed by decarbonylation of the substrate. Complex 2 is a superior catalyst precursor, since it is air-stable and readily prepared by treating complex 1 with CO.
The provided examples of utilization of glycerol and glycerol-containing media are far from completely reflecting the diversity of research works dedicated to this problem. Nevertheless, the presented works provide sufficiently convincing evidence on broad prospects for utilization of excess glycerol for obtainment of practically important products in the course of chemical and biotechnological processes.
Mesoporous tungsten trioxide (m-WO3) was prepared using an evaporation-induced self-assembly method and was used as the support of Pt for hydrogenolysis of glycerol to produce 1,3-propanediol. In comparison with commercial WO3, the m-WO3 presents a much larger surface area and better reducibility, which make the Pt particles highly dispersed on the support. At a reaction condition of 180°C, 5.5 MPa H2, and reaction time of 12 h, the Pt/m-WO3 catalyst afforded 18.0% conversion of glycerol and 39.2% selectivity for 1,3-propanediol, both of which are much higher than those on commercial Pt/WO3 catalyst.摘要以金属酞菁为催化剂, 2,5-二羧酸-3,4-二烷氧基噻吩在水相中脱羧, 以较高的产率和纯度制得 3,4-二烷氧基噻吩, 避免了有机极性溶剂的使用, 催化剂重复使用 8 次仍表现出优异的催化性能. 另外, 通过简易的水蒸气蒸馏法即可分离出产物. 该法具有环境友好、操作简易和反应时间短等优点, 是一种制备 3,4-二烷氧基噻吩的绿色方法.
Catalytic activities of silicotungstic, phosphotungstic, and phosphomolybdic acids in the liquid phase dehydration of glycerol to acrolein were investigated in a semi-batch reactor. The acidities of the heteropolyacid catalysts were evaluated by NH3-TPD. The effect of the acidity of the heteropolyacid catalyst on the conversion of glycerol and the yield of product was discussed. Silicotungstic acid exhibited high catalytic activity in the dehydration of glycerol to acrolein. The maximum acrolein yield of 78.6% was achieved when glycerol was completely converted at the reaction temperature of 300 °C with the mole ratio of silicotungstic acid to glycerol of 1 × 10−4:1. The catalytic activities of the heterpolyacids toward the formation of acrolein were in an order of silicotungstic acid > phosphotungstic acid > phosphomolybdic acid, revealing that the dehydration of glycerol to acrolein was affected by the acidity and the stability of the heteropolyacids. Hydroxyacetone and acetic acid were also detected with the yields of less than 10%, respectively. In the liquid phase dehydration of glycerol to acrolein catalyzed by silicotungstic acid, semi-batch reaction technique is a potentially practical method in viewpoint of high acrolein yield, low catalyst consumption, and energy saving.
Hydrogenolysis of glycerol to 1,3-propanediol in aqueous-phase was investigated over Pt-H4SiW12O40/SiO2 bi-functional catalysts with different H4SiW12O40 (HSiW) loading. Among them, Pt-15HSiW/SiO2 showed superior performance due to the good dispersion of Pt and appropriate acidity. It is found that Brønsted acid sites facilitate to produce 1,3-PDO selectively confirmed by Py-IR. The effects of weight hourly space velocity, reaction temperature and hydrogen pressure were also examined. The optimized Pt-HSiW/SiO2 catalyst showed a 31.4% yield of 1,3-propanediol with glycerol conversion of 81.2% at 200 °C and 6 MPa.
Graphical Abstract
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The feasibility of acetylation of glycerol with acetic acid was investigated employing CeO2–ZrO2, CeO2–Al2O3, SO42−/CeO2–ZrO2, and SO42−/CeO2–Al2O3 solid acid catalysts to synthesize monoacetin, diacetin and triacetin having interesting applications as bioadditives for petroleum fuels. Intensive physicochemical and surface characterization of the prepared catalysts were performed using XRD, BET surface area, ammonia-TPD and Raman spectroscopy techniques. Characterization results revealed that impregnated sulfate ions strongly influence the physicochemical characteristics of the investigated mixed oxide catalysts. Among various catalysts investigated, the SO42−/CeO2–ZrO2 combination catalyst exhibited superior catalytic activity under mild conditions. The effect of various parameters such as reaction temperature, molar ratio of acetic acid to glycerol, catalyst wt% and time-on-stream were studied over the SO42−/CeO2–ZrO2 catalyst to optimize the reaction conditions. Catalyst reusability was also carried out to understand its stability.
Hydrogenolysis of aqueous glycerol was conducted with Ir-ReOx/SiO2 catalyst and solid acid co-catalyst. Considering the reusability and activity, H-ZSM-5 is the most suitable solid co-catalyst. The property of Ir-ReOx/SiO2 + H-ZSM-5 system including kinetics and selectivity trends in various reaction conditions is similar to the case of Ir-ReOx/SiO2 + H2SO4. The catalyst stability, activity, and the maximum yield of 1,3-PrD of Ir-ReOx/SiO2 + H-ZSM-5 were slightly lower than Ir-ReOx/SiO2 + H2SO4. The role of added acid may be to protonate the surface of ReOx cluster to increase the number of hydroxorhenium site, which activates glycerol by the formation of glyceride species.
Metallic Ni (10 wt.%) supported on SBA-15 silica and promoted with cerium loading ranged between 2.5 and 10 wt.%, reduced at 723 K during 1 h, were used as catalysts in the hydrogenolysis of a glycerol aqueous solution (80 wt.%) at 473 K and 2.4 MPa of H2 pressure. Whereas pure Ni catalyst mainly produces volatile products by CC hydrogenolysis reaction, the promoted cerium catalysts lead to the formation of 1,2-propanediol (1,2-PDO) as majority product. After 8 h of reaction the catalyst with 10 wt.% of Ni and 7.5 wt.% of Ce gives the maximum glycerol conversion and selectivity to 1,2-PDO, with yield of this substance of 24.2%/g of catalyst. The presence of cerium species is essential to produce 1,2-PDO. The effect of cerium oxide is to act as strong acid sites (TPD-NH3), improve the metallic Ni dispersion (XRD, H2 chemisorption and XPS) and to make more difficult their reduction (TPR). The stronger acidity suggests that the formation of acetol takes place easier in these catalysts and subsequently this intermediate is reduced by activated hydrogen from the nearby Ni metallic sites.
We have used Cu/γ-Al2O3 catalysts submitted to different activation protocols (calcination, reduction in H2/Ar, and reoxidation in N2O/N2) in order to investigate the role of the different copper surface species and acid properties in glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) under mild reaction conditions (493 K, 2.4 MPa H2). The activated catalysts have been characterized by temperature-programmed reduction (TPR), temperature-programmed desorption of NH3 (TPD-NH3), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (DRIFT-CO). The significant different catalytic performance obtained with the Cu/γ-Al2O3 solids is not integrally related to their acid properties, surface Cu species also participate in the glycerol conversion. Partially reduced copper species (Cu+) promotes glycerol conversion rates. Activated catalysts follow the sequence: reoxidation > reduction > calcination, when glycerol conversion is compared. Moreover, Cu species are mostly responsible for the observed 1,2-PDO selectivity values. It is strongly dependent on the Cu0/Cu+ atomic ratio and on the surface concentration of both Cu0 and Cu+ species. Accordingly, 10CuAl-c-r catalyst showed the best behavior in glycerol hydrogenolysis to 1,2-PDO.
A biocatalytic synthesis of glycerolcarbonate (GlyC), as an added-value product of renewable glycerol, has been developed using a catalytic route in which glycerol (Gly) was reacting with dimethyl carbonate (DMC) in the presence of lipase under solvent-free conditions. The enzyme screening indicated lipase from Aspergillus niger as the most efficient biocatalyst for the GlyC synthesis. After the optimization of the reaction conditions it was established that the best results corresponded to 12% (w/w) Aspergillus niger lipase, to a glycerol:DMC molar ratio of 1:10, to an incubation time of 4 h and to an incubation temperature of 60 °C. Consequently, the glycerol conversion was around 74%, the yield in GlyC of 59.3% and the selectivity to GlyC of 80.3%. Recycling experiments demonstrated that the biocatalyst can be successfully used for several reaction cycles (at least 4 times) and confirmed its very high stability under the reaction conditions.
Conjugate addition reactions are efficiently performed by a very simple electrochemical method using nickel complexes as catalysts. In this paper, we reported a new method for the valorization of glycerol 1,2-carbonate. Firstly, we prepared the activated glycerol 1,2-carbonate derivatives (halogen or pseudo-halide derivatives), and secondly applied these halogen derivatives in coupling reactions by electrochemical methods with organic compounds and environment-friendly solvent (propylene carbonate). To our knowledge, this is the first report of creation of carbon–carbon bonds on the glycerol 1,2-carbonate and of the synthesis of these compounds.
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.
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.
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.
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.
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.
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.
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.
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.
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%.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.