Mitigating catalyst deactivation in the industrially deployed process of methanol-to-olefins conversion over HSAPO-34 is a critical challenge. Here, we demonstrate that lifetime in methanol-to-olefins catalysis over HSAPO-34 at sub-complete methanol conversion, as determined by the cumulative turnover capacity per Brønsted acid site towards hydrocarbon products in the effluent before complete catalyst deactivation (~15% carbon final conversion), can be enhanced with increasing efficacy (~2.8× to >70×) by co-feeding H2 at increasing partial pressures (400–3,000 kPa) in the influent with methanol compared with co-feeding helium at equivalent pressures. The lifetime improvement in the presence of high-pressure H2 co-feeds is observed to be more prominent at complete methanol conversion than at sub-complete conversion. The improvements in catalyst lifetime by co-feeding H2 are rendered without any deleterious effects on C2–C4 olefins selectivity, which remains ~85% carbon irrespective of the inlet H2 pressure. These observations can be rationalized based on the participation of H2 in hydrogen transfer reactions, and in effect, the interception of pathways that promote the formation of deactivation-inducing polycyclic species.
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We acknowledge: The Dow Chemical Company and National Science Foundation (CBET 1701534) for financial support; the Characterization Facility, University of Minnesota, which receives partial support from the National Science Foundation through the Materials Research Science and Engineering Centers programme, for providing the X-ray diffraction and X-ray photoelectron spectroscopy data; T. Whitmer, The Ohio State University, for providing the NMR data; The Dow Chemical Company, Analytical Science, Midland and Terneuzen for providing the quantitative elemental analysis, scanning electron microscopy and extracts analysis data; D. M. Millar, The Dow Chemical Company, for synthesis of the SSZ-13 sample; and J. F. DeWilde, The Dow Chemical Company, for helpful technical discussions.
© 2018, The Author(s).