Selective liquid-phase ketalization of glycerol with acetone to obtain solketal.

DUARTE, HERNÁN ANTONIO; LUGGREN, PABLO JORGE; ZELIN, JUAN

Buenos Aires

Congreso; 11th WORLD CONGRESS OF CHEMICAL ENGINEERING (WCCE11); 2023

World Chemical Engineering Council (WCEC)

In the biodiesel production from the transesterification of vegetable oils, a significant amount of glycerol (the main by-product) is obtained. The chemical transformation of glycerol into high value-added products is a challenge for the chemical industry. The ketalization reaction with acetone is a very attractive option for the valorization of this polyol, since it is possible to obtain solketal (2,2-dimethyl-1,3-dioxolan-4-methanol), a product used as a diesel additive and as a green solvent. In this work, commercial acid resins were used as catalysts to evaluate the liquid-phase ketalization of glycerol with acetone and to determine their catalytic activity, stability, and selectivity to solketal. The objective is to achieve high yields in solketal under moderate reaction conditions, thereby contributing to the development of industrially scalable processes. Glycerol ketalization with acetone was carried out at 313 K during 6 h in a five-necked glass batch reactor with magnetic stirring. Samples were periodically collected and analyzed by gas chromatography (GC). Ethanol was employed as a solvent to homogenize the mixture of starting reagents. Several catalytic experiments were carried out to elucidate the influence of the reaction parameters on solketal production. Three Purolite acid resins (CT275DR, PPC100H and C150SH) were tested at 313 K and a 3:1 molar ratio (acetone:glycerol). Purolite CT275DR showed the highest initial conversion rate (r_gly^0=0,86 〖mol.h〗^(-1).g_cat^(-1)) and achieved after 6 h of reaction the same glycerol conversion and solketal yield of 70%, which corresponds to the equilibrium composition. Additional catalytic tests were carried out with CT275DR varying the molar ratio of reactants (acetone:glycerol, in a 1-20 range) at 313 K. As expected, equilibrium conversion of glycerol grew with the increase in the molar ratio of the reactants, reaching a yield in solketal of 95% for a 20:1 molar ratio. On the other hand, the effect of reaction temperature (258-333 K) for a 3:1 molar ratio was studied. The solketal yield decreased with the increase in the reaction temperature, which indicates the exothermicity of the reaction, the best solketal yield was 90% at 258 K. Moreover, the stability and feasibility of reusing the Purolite CT275DR, which showed the best catalytic performance of the resin series used in this work, was studied at 313 K and for a 3:1 molar ratio. The experiments carried out with CT275DR in five catalytic cycles showed that the glycerol conversions and solketal yields were close to 70% in all cycles. Purolite CT275DR showed the best performance in the ketalization reaction of glycerol with acetone to obtain solketal and it was reused in five catalytic cycles with no activity loss. Thus, solketal production employing this resin appears as a promising technology for glycerol valorization.