A novel tandem route to renewable isoprene over Mo-Fe oxide and mesoporous Cu/MgO composite catalysts

The preparation of renewable isoprene from biomass-derivable feedstocks is extremely desirable for the sustainable rubber/latex/pharmaceutical industries. We report here a novel tandem route to efficiently produce isoprene via bio-sourced methanol and isobutene over Mo-Fe-O+meso-Cu/MgO composite catalysts. High isoprene selectivity of 85 % was achieved at methanol conversion of 91 % under optimal conditions. Adding Cu into mesoporous MgO finely tunes the basicity and acidity balance, thereby promoting isoprene selectivity. It shows good recycle capability, with isoprene selectivity remaining 85 % after five successive regeneration cycles. In-situ DRIFTS of methanol and isobutene adsorption suggest the possible reaction pathways involve methanol oxidation to formaldehyde on Mo-Fe oxide, followed by Prins condensation between formaldehyde and isobutene to isoprenol, and final conversion to isoprene on meso-Cu/MgO. This work not only represents a great advance in industrial large-scale producing isoprene, but provides an efficient strategy for developing methanol as in-situ precursor of formaldehyde to participate in many reactions.