Acetalization of glycerol over sulfated UiO-66 under mild condition

Abstract

Sulfated metal–organic framework has attracted much attention as a versatile heterogeneous acid for its strong acid strength, large surface area and regular pore channels. In this work, sulfated UiO-66 (UiO-SO3H-x) was prepared via the direct oxidation of 2-mercaptobenzoic acid substituted UiO-66. The structure and property of the synthesized UiO-SO3H-x were characterized via XRD, FTIR, static water contact angles, XPS, TG-DTA, N2 adsorption–desorption, SEM and TEM in detail. It was found that sulfonic acid groups dispersed homogenously in the framework of UiO-SO3H-x. And UiO-SO3H-0.2 exhibited excellent performance and stability for the synthesis of solketal from surplus glycerol among the tested solid acids (H3PW12O40, Amberlyst-45, HY, HBEA, HZSM-5 and ZrHP). The detected conversion of glycerol reached 70.3% with a 99.8% selectivity toward solketal at 60 °C, and it could maintain its initial activity in five recycles. The highest TOF of each acid site in UiO-SO3H-0.2 reached 676.0 h−1. Moreover, it was versatile for the acetalization of glycerol with other ketones/aldehydes.