Sustainable utilization of waste glycerol for 1,3-propanediol production over Pt/WOx/Al2O3 catalysts: Effects of catalyst pore sizes and optimization of synthesis conditions

Recycling of waste glycerol derived from biodiesel production to high value-added chemicals is essential for sustainable development of Bio-Circular-Green Economy. This work studied the conversion of glycerol to 1,3-propanediol over Pt/WOx/Al2O3 catalysts, pointing out the impacts of catalyst pore sizes and operating conditions for maximizing the yield of 1,3-propanediol. The results suggested that both pore confinement effect and number of available reactive metals as well as operating conditions determined the glycerol conversion and 1,3-propanediol selectivity. The small-pore 5Pt/WOx/S-Al2O3 catalyst (6.1 nm) gave a higher Pt dispersion (32.0%), a smaller Pt crystallite size (3.5 nm) and a higher number of acidity (0.47 mmol NH3 g(-1)) compared to those of the large-pore 5Pt/WOx/L-Al2O3 catalyst (40.3 nm). However, glycerol conversion and 1,3-propanediol yield over the small-pore 5Pt/WOx/S-Al2O3 catalyst were significantly lower than those of the large-pore Pt/WOx/L-Al2O3 catalyst, suggesting that the diffusional restriction within the small-pore catalyst suppressed transportation of molecules to expose catalytic active sites, favoring the excessive hydrogenolysis of 1,3-propanediol, giving rise to undesirable products. The best 1,3-propanediol yield of 32.8% at 78% glycerol conversion were achieved over the 5Pt/WOx/L-Al2O3 under optimal reaction condition of 220 degrees C, 6 MPa, 5 h reaction time and amount of catalyst to glycerol ratio of 0.25 g mL(-1). However, the 1,3-propanediol yield and glycerol conversion decreased to 19.6% and 51% after the 4th reaction-regeneration which were attributed to the carbonaceous deposition and the agglomeration of Pt particles. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study focused on the conversion of waste glycerol to 1,3-propanediol using Pt/WOx/Al2O3 catalysts, and found that the catalyst pore sizes and operating conditions significantly influenced the process. It was observed that while small-pore catalysts may have advantages in terms of active metal dispersion and acidity, they could also lead to diffusional restrictions and hinder the exposure of catalytic active sites, resulting in lower product yields.