Furfural production from the lignocellulosic agro-forestry waste by solvolysis method – A technical review

Furfural is one of the most prospective platform chemicals derived from biomass. This review summarises the principal factors governing the yield/selectivity of furfural by solvolysis technique, with a particular attention to the conversion of C6 cellulose feedstock. So far, most studies focused on the C5 sugar-rich feedstock, which requires solely dehydration to convert into furfural. In contrast, the conversion of C6 sugars to furfural is more challenging, requiring dehydration and C–C bond breakage. Depending on the type of biomass and catalyst, the reaction temperature and residence time have an optimum value of ∼160–180 °C and ∼ 30–120 min respectively in traditional heating mode. The low optimum temperature (∼140 °C) for the microwave-assisted technique and that C5 polymers do not necessarily require longer reaction time than their monomers indicate that microwave irradiation is more efficient in depolymerisation reaction of polymers. Additionally, the organic solvent systems containing <10 wt% water were the most promising. For catalysts, sulphates/sulphonated catalysts showed the highest potential for furfural production, and Zn²⁺, Cu²⁺ and Fe³⁺ are the most promising cationic candidates. Finally, the future perspectives were proposed, including development of novel heterogeneous catalysts and microwave-assisted technique, kinetic study and mechanistic study for the conversion of C6 sugars.