Conversion of Synthesis Gas to Light Olefins: Impact of Hydrogenation Activity of Methanol Synthesis Catalyst on the Hybrid Process Selectivity over Cr-Zn and Cu-Zn with SAPO-34

Direct conversion of syngas to hydrocarbons occurs over hybrid catalyst mixtures containing methanol synthesis and microporous acid components. In particular, both copper and zinc oxide-based as well as chromium-and zinc-based catalysts are active for methanol synthesis and can be used in the hybrid catalyst process. The choice of methanol synthesis catalyst alters product selectivity and distribution. In particular, reaction products of the Cu-Zn/SAPO-34 system include only saturated hydrocarbons, while the Cr-Zn/SAPO-34 catalyst enables light olefin production directly from syngas. Hydrogenation properties of the methanol synthesis catalyst influence the C-3/C-2 yield ratios in the hydrocarbon products. We analyze the observed differences of selectivity with respect to olefin hydrogenation activities of the methanol synthesis components and their interaction with SAPO-34 for methanol-to-olefins conversion. A simplified kinetic model for the hybrid system is proposed to describe the observed selectivity patterns.