Use of biobased crude glycerol, obtained biocatalytically, to obtain biofuel additives by catalytic acetalization of furfural using SAPO catalysts

Identifier:  imarina:9247335

Handle: https://hdl.handle.net/20.500.11797/imarina9247335

Authors:  Guerrero-Ruíz, F; Yara-Varón, E; González, MD; Torres, M; Salagre, P; Canela-Garayoa, R; Cesteros, Y

Abstract:
High-pure crude glycerol, obtained from the transesterification of coconut oil with ethanol using lipase enzyme-type as biocatalyst, has been used for the acetalization of furfural with several SAPO 5 and SAPO 34 catalysts. SAPOs were prepared using microwaves and conventional heating for comparison, and were characterized by X-ray diffraction, nitrogen physisorption, elemental analysis, thermogravimetry of adsorbed cyclohexylamine and scanning electron microscopy techniques. The use of microwaves allowed us the incorporation of slightly higher amounts of silicon into the aluminophosphate structure, and the preparation of the materials in much shorter preparation times, with the subsequent energy saving. Additionally, the SAPOs prepared with microwaves showed lower crystallinity but higher surface area than those prepared by conventional heating. Comparable catalytic results were obtained when these catalysts were tested for the acetalization of furfural with commercial or with the crude glycerol obtained by biocatalytic transesterification of coconut oil, leading to very high selectivity values to the desired mixture dioxane + dioxolane (93–100 %), which can be used as biofuel additives, for conversion values between 60 and 73 %, as determined by gas chromatography. This confirmed the high purity of the glycerol obtained by the biocatalytical process, as previously observed by 1H NMR. SAPO 34 catalysts showed higher conversion than SAPO 5 catalysts due to their higher amount of more accessible Brønsted acid sites, related to their structure. Interestingly, catalysts prepared with microwaves resulted in slightly higher conversion values than those prepared by conventional heating. This can be explained by the incorporation of higher amounts of silicon in the framework, probably due to the higher homogeneity of the microwaves heating, which results in a higher amount of protons, as confirmed by TGA of adsorbed cyclohexylamine, responsible for the catalysis.