Synthesis of dimethyl carbonate (DMC) by carboxylation reaction using Mg-Al-hydrotalcites catalysts modified with phosphoric acid

摘要

Introduction DMC is a versatile and green reagent. It can be used as precursor for resins and fuel additive. Nowadays, the majority of DMC industrial synthesis is based on phosgene-free technologies by oxidative carbonylation of MeOH. However, the reactant mixture is highly flammable and chemicals used such as CO are toxic. The DMC synthesis based on CO2 is presented like an eco-efficient and economic alternative. The carboxylation reaction using solid-acid-base ZrO2 catalyst presents a complete selectivity towards the DMC instead of the by-product dimethyl ether (DME) but a very low MeOH conversion (<1%) [1]. Modifying ZrO2 by acidic compounds such as phosphoric acid (H3PO4/ZrO2), where P/Zr=0.025-0.1, promotes catalytic activity [2]. The hydrotalcites-like compounds (HT) can be activated by thermal decomposition to obtain a high-surface area and well-dispersed Mg-Al mixed oxide (HTO) with acid-basic properties. In this paper, we synthesized and characterized H3PO4-modified HTO catalysts with different H3PO4 content. These catalysts were tested on the carboxylation of MeOH in a continuous process.