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Abstract: Acetalisation of glycerol with butanal has been investigated over a range of zeolites with different pore structures and acidity (USY with different Si/Al ratio, BEA and ZSM-5). The products of glycerol acetalisation were (Z+E)-(2-propyl-1,3-dioxolan-4-yl) methanol (five-member ring acetal) and (Z+E)-2-propyl-1,3-dioxan-5-ol (six-member ring acetal). The results showed an optimum in activity for Si/Al ratio in USY zeolite that corresponds to 30. BEA zeolite presented the highest catalytic activity of all zeolites while ZSM-5 zeolite presented the lowest activity. All catalysts exhibited high selectivity to five-member ring acetal product (77–82%). The effects of reaction temperature, catalyst loading and molar ratio of glycerol to butanal on this reaction, over BEA zeolite, have been studied. It was found that the glycerol conversion increased with the catalyst loading, with the temperature and with molar ratio of glycerol to butanal. BEA zeolite was recycled four times with the same catalyst sample. It was observed a stabilization of the catalytic activity (after the fourth use, the zeolite showed 93% of its initial activity). [Copyright &y& Elsevier]

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 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. [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]

• Acetalization of glycerol with pentanal was performed over molybdophosphoric acid (HPMo) encaged in USY zeolite. • High catalytic activity with low amount of HPMo@Y was observed. • High selectivity to (2-butyl-1,3-dioxolan-4-yl) methanol product. • Good catalytic activity after the forth use. Dodecamolydbophosphoric acid (HPMo) immobilized on USY zeolite was used as a catalyst for the acetalization of glycerol with pentanal at 70 °C. Catalysts were prepared with different amounts of heteropolyacid, and the most active sample was the HPMo2@Y catalyst (1.1 wt.%). The products of glycerol acetalization with pentanal were (2-butyl-1,3-dioxolan-4-yl)methanol, a five-member ring compound, and 2-butyl-1,3-dioxan-5-ol, a six-member ring compound. Good values of selectivity for the five-member ring compound (80–85%) were obtained with all materials. The reaction conditions were optimized using HPMo2@Y as a catalyst. The optimal conditions were determined to be 70 °C reaction temperature with 0.3 g catalyst and a 1:2.5 M ratio of glycerol to pentanal. The catalytic stability of HPMo2@Y was studied. The acetalization of glycerol with pentanal was performed using the same sample. High catalytic activity for HPMo2@Y was observed. [ABSTRACT FROM AUTHOR]

• Acetalization of glycerol with cinnamaldehyde was performed using PW immobilized on NaY. • The material NaY-PW4 showed high activity. • Good selectivity to (2-(2-phenyl-1-ethenyl)-1,3-dioxolan-4-yl)methanol product. • After fifth utilizations, the NaY-PW4 material showed good activity. Glycerol was reacted with cinnamaldehyde over phosphotungstic acid (PW) encapsulated on NaY at 100°C. Catalysts containing different PW contents were prepared. The activity increased with an increasing amount of PW encapsulated on NaY, and the use of the NaY-PW4 (0.121 g pw /g NaY) material resulted in a superior conversion compared to those obtained using the other materials. After 5 h, the conversion of glycerol was 89% at 100°C using 0.3 g of catalyst and a glycerol:cinnamaldehyde molar ratio of 1:2.25. Furthermore, NaY-PW4 exhibited a good catalytic stability. [Display omitted] [ABSTRACT FROM AUTHOR]