A continuous-flow process for the acetalization of crude glycerol with acetone on zeolite catalysts

A continuous flow process using heterogeneous catalysts like zeolites (BEA, MFI, FAU) was developed for the conversion of crude glycerol with acetone to solketal (2,2-dimethyl-1,3-dioxolane-4-methanol). It was found that BEA zeolite and the hierarchical zeolite of MFI structure exhibit a high catalytic activity in solketal production for 3 hr on stream. Almost 85% of glycerol conversion and 98% selectivity to solketal was achieved after 1 h of the reaction. The regeneration of spent catalysts by means of calcination with following ionic exchange restored the initial activity of the applied samples. The effect of particular impurities (alkaline cations, water, and MONG (matter organic non glycerol)) present in crude glycerol, on the deactivation process of catalysts, was also explored. Analysis of carbon balance and low-temperature nitrogen adsorption/desorption measurements, as well as FT-IR spectra of applied materials (pure and crude glycerol and spent catalysts) evidenced that the concurrent presence of MONG and alkaline cations reduce the zeolite catalysts activity. Considering the alteration of selectivity toward five and six membered isomers with declining acidity of spent catalyst, some tentative reaction paths of both isomers formation have been proposed.