Influence of the Alcohol Molecular Size in the Dehydration Reaction Catalyzed by Carbon-Supported Heteropolyacids

Abstract

The catalytic performance of tungstophosphoric and molybdophosphoric acids supported on two commercial carbons, for dehydration reactions of several alcohols, was studied. The alcohol conversion depended on their molecular size, while selectivity to alkenes was also related to cyclodimer molecular size formed by certain alkenes in acidic medium. Acidity and mean pore diameter of the catalysts showed an influence on the conversion degree of the alcohols into alkenes and also into alkene cyclodimerization.

Solid acid catalyzed biodiesel production by simultaneous esterification and transesterification

“…Literature studies also support this observation; as reactant molecule size was found to exert a marked influence on the heterogeneous reactions catalyzed by heteropolyacids supported on activated carbon. 16 The reaction mechanism of simultaneous esterification and transesterification using Lewis acid is as shown in Scheme 1. The esterification takes place between free fatty acids (RCOOH) and methanol (CH 3 OH) whereas transesterification takes place between monoglyceride (RCOOR9) (taken as representative of triglycerides in this case) and methanol adsorbed on acidic site (L + ) of catalyst surface.…”

Effect of the support on a new metanethole synthesis heterogeneously catalyzed by Keggin heteropolyacids

“…The surface groups differ, since hydroxyl groups are present on the silicas, while in the carbons a variety of surface groups can be present in addition to hydroxyl groups, such as carbonyl, lactonic, aromatic groups, among others. On the other hand, the different textural characteristics can be reflected in the catalytic behavior, as was proved in alcohol dehydration reactions using different carbons [13].…”

“…The FT-IR spectra of the catalysts based on MPA showed bands at 1056, 958, 870, and 791 cm À1 , and those corresponding to TPA presented bands at 1079, 983, 891, and 800 cm À1 , which are characteristic of the molybdophosphate and tungstophosphate anions, respectively [11,13,14]. However, some bands were overlapped with those of the supports.…”

Metal-supported carbon-based materials: opportunities and challenges in the synthesis of valuable products

“…Subsequent studies performed for the dehydration of several alcohols over TPA and molybdophosphoric acid supported on AC catalysts showed that the alcohol conversion depended on their molecular size. 71 Moreover, selectivity to alkenes depended on the cyclodimer molecular size, whose formation decreased with a larger dimer size.…”