Benchmarking Cu/BEA and HBEA catalysts for high-octane gasoline synthesis

Abstract

We distinguish rates at which carbon deposition occurs during initiation, rates at which catalytic centers are lost during deactivation, and paraffin-to-olefin ratio during propagation as benchmarks that distinguish 5 wt% Cu/H-BEA and H-BEA (Si/Al = 13.5) catalysts during dimethyl ether (DME) homologation in the presence of hydrogen. Studies that systematically vary initial DME contact time (210, 94, and 45 molH+, initial s (mol C)−1), DME pressure (4 and 22 kPa), and H2 pressure (1, 24, and 48 kPa) reveal that Cu enables lower carbon deposition rates (on a per proton basis) in the induction period, increases the effluent paraffin-to-olefin ratio during propagation, and decreases instantaneous site-loss yields during termination by 1.5–2× (moles of active sites lost per mole of DME) thus augmenting the degree of product saturation and catalyst stability during DME homologation. These results provide mechanistic insights revealing the critical role of Cu in facilitating DME homologation to high value, high-octane gasoline-range hydrocarbons with higher cumulative turnovers than proton form H-BEA.