Abstract
Recently extensive efforts have been made to obtain drop-in fuel or fuel additives from renewable and sustainable resources. Alkoxymethyl furfurals synthesized from etherification reactions of aliphatic alcohols and 5-(hydroxymethyl)furfural (HMF) have been proposed as a diesel fuel additive and precursor of the drop-in fuel. Among the alkoxymethyl furfurals, 5-(methoxymethyl)furfural (MMF) and especially 5-(ethoxymethyl)furfural (EMF) have received much attention due to their superior prosperities including high energy density, low toxicity, high stability, and proper flow properties. Different acid catalysts have been tested for cost-effective production of EMF and MMF. Besides, broad ranges of feedstock from untreated lignocellulosic biomass and algae to carbohydrates and HMF have been used and their performances have been investigated. Production technologies for these fuel compounds and upgrading some of these compounds have been surveyed in many review papers. Therefore, making a concise overview on the production methodologies of all the relevant furan based fuel compounds, including long chain hydrocarbon alkanes from furfurals such as EMF and MMF is worthy of investigation. The current review summarizes the available technologies to help with further improvements and advancements of the production technologies of EMF and MMF. A special emphasis is placed on the state-of-the-art catalytic processes for EMF and MMF synthesis. Based on the review, the future direction is suggested.