Dimethoxymethane as a Cleaner Synthetic Fuel: Synthetic Methods, Catalysts, and Reaction Mechanism

Abstract

The increasing concerns regarding exhaust and CO2 emissions from fossil-based transportation fuels have propelled intensive research aimed at finding alternative fuel candidates to realize a clean and renewable fuel system. In this context, dimethoxymethane and its derivatives oxymethylene ethers, a class of oxygenated synthetic fuel, have recently attracted increasing interest because of their fascinating characteristics as a diesel blend compound to significantly reduce soot and nitrogen oxide formation. At present, dimethoxymethane production primarily relies on an established two-step process comprising methanol oxidation and methanol condensation with formaldehyde. Several new synthetic routes based on methanol or CO2/H2 have been proposed by adopting a reaction coupling strategy, which enables the production of dimethoxymethane in one step. A large variety of bi- and multifunctional catalysts have been developed for each synthetic route. This Review comprehensively summarizes the latest advances in synthetic approaches, catalyst systems, structure–activity relationships, and reaction mechanism for the catalytic synthesis of dimethoxymethane. Comparisons regarding the features and limitations of different synthetic approaches as well as the related catalytic materials are also provided in order to indicate possible directions for future research, especially on the rational design of catalysts, a vital factor for the commercial production of dimethoxymethane.