Fourth generation synthesis of solketal by glycerol acetalization with acetone: A solar-light photocatalytic approach

Abstract

Background: Biomass is the only renewable alternative to fossil fuels to produce chemicals. In this sense, glycerol is an important biomass-derived platform chemical obtained as a by-product during biodiesel generation. This paper reports for the first time the photocatalytic acetalization of glycerol with acetone to produce cyclic ketals, interesting chemicals with several applications such as solvents or (bio)fuel additives. Methods: Commercial TiO2 (Aeroxide® Evonik P25) was used as the photocatalyst and very mild reaction conditions (30 °C, solar-simulated light) were utilized. The effect of glycerol/acetone ratio and catalyst concentration on both glycerol conversion and five-membered/six-membered ring acetal ratio was studied through factorial design of experiments. P25 concentration was in the 1–3 g/L range whereas acetone/glycerol molar ratio varied between 6 and 20.Findings: All in all, the maximum conversion (89.6%) corresponded to 1.86 g/L and acetone/glycerol ratio of 10.96. Selectivity to the 5-membered ring ketal (solketal) was over 92% in all cases. This procedure would constitute the fourth-generation synthesis of solketal by glycerol acetalization with acetone.