Supported Cu/Al2O3 Catalyst in Combination with HZSM-5-Al2O3 Catalyst for Continuous-Flow Reductive Etherification of Furfural

Alkyl furfuryl ethers are promising additives to motor fuels, which can be produced by reductive etherification of furfural with alkyl alcohol. The Cu/Al2O3 catalyst was prepared using a copper ammonia complex as the precursor of active component. The catalytic behavior of the physical mixture of the Cu/Al2O3 catalyst and ZSM-5-Al2O3 composite was studied in the reductive etherification of furfural in a flow reactor using H2 as a reducing agent. This process involves the sequential hydrogenation of furfural on the Cu0 sites of the Cu/Al2O3 catalyst, followed by the etherification of the resulting furfuryl alcohol on the acid sites of zeolite. The highest yield of 2‑(isopropoxymethyl)furan (IMF) of 85% was achieved over the catalytic system (0.25–0.5 mm) including HZSM-5(Si/Al = 40)-Al2O3 due to the optimal concentration of strong Brønsted acid sites in the composite. A physical mixture of the Cu/Al2O3 catalyst and the 30% ZSM-5(40)-Al2O3 composite, in the form of granules (trilobe extrudates of 2–5 × 1.25 mm), showed an IMF yield of 72.5%.