Role of cerium as a promoter and process optimization studies for dehydration of glycerol to acetol over copper chromite catalyst

Abstract Cerium promoted silica supported copper chromite catalyst was synthesized from acid hydrolysis of sodium silicate by sol-gel method. The catalyst was characterized by Brunauer–Emmett–Teller (BET) method, field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-TPD and Py-Fourier transform infrared spectroscopy (Py-FTIR). Among cerium doped catalysts, 5 wt% of Ce with respect to copper chromite which is 40 wt% of silica support (SiCuCr40-Ce5) shows the highest BET surface area. XRD analysis of the reduced form of the catalyst shows both CeO2/Ce2O3 redox system as well as CuO/Cu2O/Cu redox system. Pyridine adsorbed FTIR shows the maximum number of Lewis acid sites for SiCuCr40-Ce5 than others. Highest acetol selectivity with AR grade (Analytical Reagent) glycerol conversion was observed for SiCuCr40-Ce5 at 200 oC for 3 h in a batch reactor at atmospheric pressure. Cerium promotion has lowered the reaction temperature with enhanced glycerol conversion and increased acetol selectivity. Though the above catalyst showed higher conversion for LR grade (Laboratory Reagent) glycerol but it reduces acetol selectivity. The addition of glucose into the LR grade glycerol further reduces glycerol conversion and decreases the acetol selectivity to zero. This may be due to the presence of iron as impurity in LR grade glycerol. XRD analysis of spent catalyst shows the absence of redox catalytic system and the pore volume reduces identified by BET analysis. Raman analysis of the spent catalyst shows graphite-like carbon deposition in the spent catalyst.