- Biobased catalyst in biorefinery processes: Sulphonated hydrothermal carbon for glycerol esterification
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Sulphonated hydrothermal carbon (SHTC), obtained from d-glucose by mild hydrothermal carbonisation and subsequent sulphonation with sulphuric acid, is able to catalyse the esterification of glycerol with different carboxylic acids, namely, acetic, butyric and caprylic acids. Product selectivity can be tuned by simply controlling the reaction conditions. On the one hand, SHTC provides one of the best selectivity towards monoacetins described up to now without the need for an excess of glycerol. On the other hand, excellent selectivity towards triacylglycerides (TAG) can be obtained, beyond those described with other solid catalysts, including well-known sulphonic resins. Recovery of the catalyst showed partial deactivation of the solid. The formation of sulphonate esters on the surface, confirmed by solid state NMR, was the cause of this behaviour. Acid treatment of the used catalyst, with subsequent hydrolysis of the surface sulphonate esters, allows SHTC to recover its activity. The higher selectivity towards mono- and triesters and its renewable origin makes SHTC an attractive catalyst in biorefinery processes.
- De La Calle, Carlos,Fraile, José M.,García-Bordejé, Enrique,Pires, Elísabet,Roldán, Laura
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p. 2897 - 2903
(2015/05/13)
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- Photopolymerizable Synthons from Glycerol Derivatives
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Photopolymerizable monomers based on monoglycerides were prepared by a convenient two-step procedure. The first one consists of the synthesis of highly pure monoglycerides by an organocatalyzed solvent-free route. This process was carried out by condensation of bio-sourced carboxylic acids (i.e. butyric, decanoic, undecylenic or stearic acids) with glycerol carbonate or glycidol in the presence of a quaternary ammonium salt as a catalyst. The obtained bio-based monoglycerides were modified in the second step by reaction with acryloyl and methacryloyl chloride leading to a series of new diacrylated and dimethacrylated monomers. The structures of the monoglycerides, diacrylated and dimethacrylated monomers were fully characterized by spectroscopic methods. Photopolymerization investigations monitored by infrared spectroscopy were achieved under ultraviolet radiation in the presence of a photoinitiator. The resulting cross-linked materials were analyzed by thermal gravimetric analysis, gel content determination and tests of swelling in water, ethanol and methylene chloride. Data relative to the pendulum hardness of these materials are also included.
- Mhanna, Ali,Sadaka, Faten,Boni, Gilles,Brachais, Claire-Helene,Brachais, Laurent,Couvercelle, Jean-Pierre,Plasseraud, Laurent,Lecamp, Laurence
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p. 337 - 348
(2014/03/21)
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- Design of a highly active silver-exchanged phosphotungstic acid catalyst for glycerol esterification with acetic acid
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A series of highly active, selective, and stable silver-exchanged phosphotungstic acid (AgPW) catalysts were prepared, characterized, and evaluated for bio-derived glycerol esterification with acetic acid to produce valuable biofuel additives. The structures, morphologies, acidities, and water tolerance of these samples were determined by FTIR, Raman, XRD, SEM-EDX, FT-IR of pyridine adsorption, and H2O-TPD. Several typical acidic catalysts were also performed for comparison. Among them, partially silver-exchanged phosphotungstic acid (Ag1PW) presented exceptionally high activity, with 96.8% conversion within just 15 min of reaction time and remarkable stability, due to the unique Keggin structure, high acidity as well as outstanding water-tolerance property. A plausible reaction mechanism was also proposed. In addition, this Ag1PW catalyst exhibited universal significance for esterification, holding great potential for a wide range of other acid-catalyzed reactions.
- Zhu, Shanhui,Gao, Xiaoqing,Dong, Fang,Zhu, Yulei,Zheng, Hongyan,Li, Yongwang
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p. 155 - 163
(2013/09/02)
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- Influence of water on the activity and stability of activated Mg{single bond}Al hydrotalcites for the transesterification of tributyrin with methanol
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Magnesium-aluminum hydrotalcite with a Mg/Al molar ratio of 4 was synthesized by a coprecipitation method. Thermally-decomposed and rehydrated Mg-Al hydrotalcites were used to catalyze the transesterification of tributyrin, a model triglyceride, with methanol (tributyrin:methanol molar ratio 1:30) at 333 K to produce methyl butyrate, monobutyrin, dibutyrin, and glycerol. The pseudo first order rate constants of a three step reaction sequence for tributyrin transesterification were determined by fitting a kinetic model to the experimental data. Although decomposed and rehydrated Mg-Al hydrotalcite was one order of magnitude more active than decomposed Mg-Al hydrotalcite based on surface area measured by N2 adsorption, the activity correlated well to the CO2 adsorption capacity. The most active rehydrated samples also deactivated faster, presumably because butyric acid produced by hydrolysis of ester with adsorbed water reacted with the base sites. The areal rate and CO2 adsorption capacity of decomposed-rehydrated Mg-Al hydrotalcite decreased as the interlayer water was removed by heating.
- Xi, Yuanzhou,Davis, Robert J.
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p. 190 - 197
(2008/09/19)
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- Lipase-mediated desymmetrization of glycerol with aromatic and aliphatic anhydrides
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Chirazyme L-2 (Candida antarctica) catalyzed esterification of glycerol with aromatic and aliphatic anhydrides in 1,4-dioxane is described. All the aromatic monoacylglycerols (MAGs) were produced as (R)-enantiomers, while aliphatic MAGs were obtained either as racemic mixtures or the (S)-enantiomers. The influence of substituted aromatic rings, chain length, and presence of a conjugated double bond in the acyl donor moiety on the enantiotopic selectivity as well as the efficiency of the enzyme was studied.
- Batovska, Daniela I.,Tsubota, Shuichirou,Kato, Yasuo,Asano, Yasuhisa,Ubukata, Makoto
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p. 3551 - 3559
(2007/10/03)
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- Method of manufacture of 1,3-oxathiolane nucleosides
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Processes for the preparation of 1,3-oxathiolane nucleosides are provided that include efficient methods for the preparation of the 1,3-oxathiolane ring and subsequent condensation of the 1,3-oxathiolane with a pyrimidine or purine base. Using the processes described herein, the compounds can be provided as isolated enantiomers.
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- Acyl transfer isomerization of glycerol 1,2-dibutyrate and propane-1,2-diol 1-butyrate
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The speciation of mixed butyrylglycerols (glycerol butyrates) and propanediol butyrate esters in the product mix from lamb pregastric lipase-catalysed hydrolysis of tributyrylglycerol and propane-1,2-diol dibutyrate has been examined by 13C n.m.r. spectroscopy. Samples from the quenched reaction mixture were extracted and allowed to stand in emulsion systems made up in bis tris propane buffer or water, pH 7.0, and in the absence of enzyme. There is clear evidence of uncatalysed conversion of rac-l,2-dibutyrylglycerol into the 1,3-isomer to form an equilibrium mixture containing c. 60-67% 1,3-isomer, and of conversion of propane-l,2-diol 1-butyrate into propane-l,2-diol 2-butyrate to form an equilibrium mixture containing c. 67% 2-monoester. Conversion kinetics to reach equilibrium are first order. Rate constants for acyl transfer of the diacylglycerol are 0.48 h-1 (in water) and 0.68 h-1 (in buffer) at 50°C, while those for acyl transfer of the 1-monoester are 0.72 h-1 (50°C) and 0.35 h-1 (35°C).
- O'Connor, Charmian J.,Barton, Richard H.
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p. 455 - 459
(2007/10/03)
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- Kinetics of acyl migration in monoglycerides and dependence on acyl chainlength
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The chemical rearrangement reaction of β- into α-monoglycerides is described. Four monoglycerides with different fatty acid chainlength have been investigated, and the equilibrium constant and the reaction velocity constants characterizing the reaction of the chemical rearrangement were estimated with a mathematical model. A 1:6.5 mixture of α/β-monoglycerides appeared to rearrange to a mixture of 1:1 α/β-monoglycerides within 24 h. Furthermore, the reaction velocity of the rearrangement reaction of β- to α-monoglycerides depended on the fatty acyl chainlength in the monoglyceride.
- Boswinkel,Derksen,Van't Riet,Cuperus
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p. 707 - 711
(2007/10/03)
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