In this paper, glycerol esterification with acetic acid (AA) was studied on several solid acid catalysts: AlO, Al-MCM-41, HPA/SiO, HBEA, Amberlyst 15 and Amberlyst 36 with the aim of determining the reaction conditions and the nature of the surface acid sites required to produce selectively triacetylglycerol (triacetin). The acidity of the catalysts (nature, density and strength of acid sites) was characterized by temperature-programmed desorption of NH and FTIR of adsorbed pyridine. AlO (Lewis acidity) did not show any activity in the reaction. In contrast, highest activity and selectivity to the triacetylated product (triacetin) were obtained on catalysts with Brønsted acidity: Amberlyst 15 and Amberlyst 36. The effect of temperature and molar ratio of AA to glycerol was studied, and the results showed that both parameters have a significant impact on the production of the desired product. Glycerol conversion rate and selectivity to triacetin increased when temperature or AA to glycerol molar ratio were increased, reaching a triacetin yield on Amberlyst 36 of 44% at 393 K and AA to glycerol molar ratio of 6. Deactivation and reusability of Amberlyst 36 were evaluated by performing consecutive catalytic tests. The presence of some irreversible deactivation due to sulfur loss was observed. In addition, the feasibility of using crude glycerol from biodiesel production as reactant was also investigated. Conversion of crude pretreated glycerol yielded values of triacetin and diacetin similar to those obtained with the commercial pure glycerol although at a lower rate.
El uso de la biomasa como materia prima para la síntesis de diversos materiales es una actividad que continúa creciendo y ha permitido el desarrollo de nuevos procesos y productos, como la síntesis de bioplastificantes a base de ácidos orgánicos como el ácido succínico, y materiales carbonáceos a partir de azúcares, polímeros naturales como la celulosa, almidón, entre otros. Aquí hemos desarrollado una serie de catalizadores, entre ellos uno a base de almidón con propiedades ácidas, un material mesoporoso no cristalino como la SBA -15 con ZrO2 incorporado y sulfatada, y carbones impregnados con ácido dodecatungstofosfórico. Estos fueron probados en la reacción de esterificación de ácido succínico con etanol, empleando la resina ácida Amberlyst 36 como catalizador de referencia para comparar los catalizadores y estudiar la influencia de los parámetros de reacción.
Catalytic esterification of succinic acid with ethanol to obtain diethyl succinate (DES), a nontoxic plasticizer, is reported. Three sulfated zirconias supported on SBA‐15 [SZ‐SBA‐15(X)] with Si/Zr molar ratios (X) of 10, 20, and 30 were synthesized and characterized. N2 adsorption/desorption isotherms and X‐ray diffraction patterns evidenced preservation of the ordered mesoporous structure of the catalysts after incorporation of Zr. Yields of DES greater than 85 % were obtained at the final reaction time by using SZ‐SBA‐15(10) and SZ‐SBA‐15(20) catalysts, which were higher than those achieved with Amberlyst 36. Reuse of the SZ‐SBA‐15(20) catalyst showed that, even though the structure of the support was preserved, decreases in sulfur concentration and in the DES yield occurred.
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