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Abstract: The acetylation of glycerol was carried out over dodecatungstophosphoric acid (PW) supported on activated carbon, being the monoacetin, diacetin and triacetin the reaction products. A series of catalysts, with different heteropolyacid loading (from 3.5 to 6.5wt.%), were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized on the activated carbon, being the PW2_AC (with 4.9wt.%) the most active sample. However, at high loading of heteropolyacid on the activated carbon, a decrease on the catalytic activity was observed, which can be probably explained due to some hindrance in the activated carbon porous system. All catalysts exhibited good values of selectivity to the diacetin. Catalytic stability of the PW2_AC was also studied by performing consecutives batch runs with the same catalyst sample. After the third batch, it was observed that the catalytic activity stabilized. [Copyright &y& Elsevier]

Abstract: The esterification of glycerol with acetic acid was carried out over dodecatungstophosphoric acid (PW) immobilized into a silica matrix. The products of glycerol acetylation were monoacetin, diacetin and triacetin. The immobilization of PW into silica was carried out by two different techniques: sol–gel and impregnation methods. The catalysts prepared by sol–gel method will be denoted as PW-in-S while the catalysts prepared by impregnation will be denoted as PW-on-S. The catalysts were characterized by nitrogen adsorption at 77K, FTIR, XDR and ICP-AES. A series of PW immobilized into silica with different PW loading were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized into silica, either by the sol–gel method or by the impregnation method. High values of selectivity to diacetin were obtained with all catalyst. The effect of various parameters, such as, reaction temperature, catalyst loading, molar ratio of glycerol to acetic acid and reusability of PW-in-S2 were studied to optimize the reaction conditions. The catalytic stability of the PW-in-S2 was evaluated by performing consecutives batch runs with the same catalyst sample. It was observed a stabilization of the catalytic activity. [Copyright &y& Elsevier]

Abstract: The esterification of glycerol with acetic acid was carried out over dodecamolybdophosphoric acid (PMo) encaged in the USY zeolite. The products of glycerol acetylation were monoacetin, diacetin and triacetin. A series of PMo encaged in the NaUSY zeolite with different PMo loading from 0.6 to 5.4wt.% were prepared. It was observed that the catalytic activity increases with the amount of PMo immobilized in the NaUSY zeolite, being the PMo3_NaUSY (with 1.9wt.%) the most active sample. However, at high loading of heteropolyacid encaged in the NaUSY zeolite, a decrease on the catalytic activity was observed, which can be explained, probably, due to the internal diffusion limitations. Good values of selectivity to diacetin were obtained with all the catalyst. Catalytic stability of the PMo3_NaUSY was evaluated by performing consecutives batch runs with the same catalyst sample. After the second batch, it was observed a stabilization of the catalytic activity. [Copyright &y& Elsevier]

Abstract: The esterification of palmitic acid with methanol was studied using tungstophosphoric acid (PW), molibdophosphoric acid (PMo) and tungstosilicic acid (SiW) immobilized by sol–gel technique on silica, at 60°C. It was observed that the catalytic activity decreases in the series: PW-silica>SiW-silica>PMo-silica. A series of PW immobilized on silica with different PW loadings from 2.5wt.% to 8.4wt.% were prepared. It was observed that the PW-silica2 (with 4.2wt.%) shows the highest catalytic activity on esterification of palmitic acid with methanol. Catalytic stability of the PW-silica2 was evaluated by performing consecutive batch runs with the same catalyst sample. After the second batch it was observed a stabilisation of the initial activity. In order to study the heteropolyacid lixiviation, a posterior catalytic experiment was carried out. The PW-silica2 was put in contact with methanol, without palmitic acid, during 72h. After this period, the catalyst was separated from methanol by centrifugation, and the palmitic acid was added to the reaction mixture. It was observed that the reaction only occurs in the heterogeneous phase. The PW-silica2 was also used as catalyst in esterification of others fatty acids: oleic and stearic acid. It was also observed a good catalytic activity of PW-silica2 for the different substrates used in the esterifications. [Copyright &y& Elsevier]

Abstract: PVA supported catalytic membranes have been synthesized by mutual γ-irradiation method using adipic acid (AA) and succinic acid (SA) as crosslinkers and a commercial ion exchange resin as catalyst. These membranes were tested as catalyst under batch conditions in esterification reaction of lauric acid to methyl laurate aiming biodiesel production. The effect of different synthesis parameters such as crosslinker, crosslinker's concentration and absorbed dose on membranes’ physical–chemical properties and catalytic activity was studied. Results demonstrated that PVA supported resin membranes are effective catalysts in the lauric acid esterification reaction. Also showed that PVA-SA membranes exhibit the better catalytic properties and, within the range of conditions studied, an increase in the γ-radiation dose leads to a slight increase of membranes’ catalytic activity. [Copyright &y& Elsevier]

Highlights: [•] Sulfonic acid catalysts supported on chitosan were prepared. [•] Esterification of fatty acids was carried out over chitosan with sulfonic groups. [•] High catalytic activity was observed. [ABSTRACT FROM AUTHOR]

Abstract: Polymeric catalytic membranes bearing sulfonic acid functions have been prepared by mutual gamma irradiation at a 60Co source, of poly(vinyl alcohol) (PVA) membranes and methanesulfonic acid. The effect of various synthesis conditions on membranes'' physical–chemical properties and catalytic activity in the esterification reaction between acetic acid and isoamyl alcohol to obtain isoamyl acetate (banana flavor), was evaluated. The membranes were characterized by ATR-FTIR, TPP, AFM and SEM. Water contact angle determinations were also performed. The obtained results showed that within the range of conditions studied the increase in sulfonic acid groups'' content is accompanied by an enhancement in the membranes catalytic activity, while the increase in absorbed dose leads to a decrease in catalytic activity. [Copyright &y& Elsevier]

Abstract: Tungstophosphoric acid (PW), molybdophosphoric acid (PMo) and tungstosilicic acid (SiW) immobilized on SBA-15 were used, as catalysts, in the esterification of palmitic acid with methanol, at 60°C. Catalysts were characterized by N2 adsorption, FTIR, X-ray diffraction, ICP-AES and TEM. All catalysts exhibited high catalytic activity in palmitic acid esterification with methanol. It was observed that the catalytic activity decreases in the follow series: PW1-SBA-15>SiW-SBA-15>PMo-SBA-15. A series of PW immobilized on SBA-15 with different PW loadings from 2.7wt% to 8.3wt% were prepared. It was observed high catalytic activity with low amount of tungstophosphoric acid immobilized on SBA-15. In order to optimize the reaction conditions, the effect of different parameters, such as catalyst loading, carbon length of the alcohol and temperature, molar ratio of fatty acid to methanol in the presence of PW3-SBA-15 were studied. PW3-SBA-15 catalyst can be separated from reaction system for re-use. It was observed a small leaching of the PW from SBA-15 to liquid phase. PW3-SBA-15 catalyst was also used in the esterification of stearic and oleic acid with methanol. High catalytic activity was observed. [ABSTRACT FROM AUTHOR]

Abstract: The esterification of palmitic acid with methanol was studied using poly(vinyl alcohol) cross-linked with sulfosuccinic acid (SSA) and polystyrene cross-linked with divinylbenzene with sulfonic acid groups, as catalysts, at 60°C. It was observed that the PVA matrixes with sulfonic acid groups were more active than the polystyrene ones. With the most active polymeric matrix (PVA_SSA40), an almost 90% equilibrium conversion was achieved after 2h. Further, the optimisation of reaction parameters, such as, catalyst loading, molar ratio alcohol to fatty acid and type of alcohol was carried out with PVA_SSA40 catalyst. Catalytic stability of the PVA_SSA40 was evaluated by performing consecutive batch runs with the same catalyst sample. After the second batch, a stabilisation of the catalytic activity was observed. The PVA_SSA40 was also used as catalyst in the esterification of oleic and stearic acid with methanol, having been obtained an equilibrium conversion of almost 80%. In order to become the biodiesel totally biogenerated, the esterification of palmitic acid was carried out with ethanol, at 60°C and 80°C. It was observed that the reaction rate is slower when the reaction is carried out with methanol, at 60°C. In a posterior catalytic experiment at 60°C, PVA_SSA40 showed catalytic activity to obtain biodiesel from animal fats (lard), in the presence of methanol. [Copyright &y& Elsevier]