Unraveling the structure-activity relationships of Cu/H-BEA bifunctional catalyst for selective synthesis of dimethoxymethane by non-oxidative dehydrogenation of methanol

Abstract

Oxymethylene ethers (OMEs) are synthetic fuels with excellent ability in reducing soot formation and good compatibility for diesel engines. Among OMEs, dimethoxymethane (DMM) is the simplest compound and its conventional production relies on an oxidative route leading to low H2 efficiency. Hence, recently, our group presented a H2 efficient gas-phase DMM synthesis route via nonoxidative dehydrogenation of methanol over Cu/Hβ. Herein, the role of Cu and Hβ are investigated by preparing Cu/Hβ catalysts with tailored properties. Highest DMM selectivity (81.5 %) was obtained over 1% Cu/Hβ-DeAl8 (Si/Al: 520). Besides, both calcined (consisting of Cu+) and reduced (consisting of Cu0) 1% Cu/Hβ-DeAl8 catalysts were active for DMM formation. Initial DMM selectivity reached 49 and 41 % for the calcined and in situ reduced catalysts, respectively, increasing to 75 % (calcined) and 81.5 % (reduced) after 1500 min TOS. The increased DMM selectivity relates to evolution of Cu species and changes with the amount of Lewis acidic sites.