Selective conversion of syngas to light olefins

TLDR

Although considerable progress has been made in direct synthesis gas conversion to light olefins via Fischer‑Tropsch synthesis, the wide product distribution remains a challenge, with a theoretical limit of only 58 % for C2–C4 hydrocarbons. The study aims to enable use of coal‑ and biomass‑derived syngas with a low H₂/CO ratio through a composite catalyst and process. The process uses a bifunctional catalyst with ZnCrO(x) oxide sites that activate CO and H₂, while zeolite acidic pores control C‑C coupling to steer product distribution. The process achieves up to 80 % C2(=)–C4(=) selectivity and 94 % C2–C4 yield at 17 % CO conversion, with no deactivation observed over 110 hours.

Abstract

Although considerable progress has been made in direct synthesis gas (syngas) conversion to light olefins (C2(=)-C4(=)) via Fischer-Tropsch synthesis (FTS), the wide product distribution remains a challenge, with a theoretical limit of only 58% for C2-C4 hydrocarbons. We present a process that reaches C2(=)-C4(=) selectivity as high as 80% and C2-C4 94% at carbon monoxide (CO) conversion of 17%. This is enabled by a bifunctional catalyst affording two types of active sites with complementary properties. The partially reduced oxide surface (ZnCrO(x)) activates CO and H2, and C-C coupling is subsequently manipulated within the confined acidic pores of zeolites. No obvious deactivation is observed within 110 hours. Furthermore, this composite catalyst and the process may allow use of coal- and biomass-derived syngas with a low H2/CO ratio.