Bifunctional Catalysis for the Conversion of Synthesis Gas to Olefins and Aromatics

Abstract

The conversion of synthesis gas (a mixture of hydrogen and carbon monoxide) to value-added chemicals has attracted significant attention in the past few years. Strong emphasis has been placed on enabling a process that allows the production of short olefins from synthesis gas, which can be derived from coal, biomass, or natural gas. Here, we introduce bifunctional catalysis to tailor the selectivity towards aromatics next to olefins by combining an iron-based Fischer–Tropsch to olefins catalyst with the acid function of a zeolite. Olefins were formed from synthesis gas on an iron-based catalyst and partly converted to aromatics on the acid sites of the zeolite. Surprisingly, this aromatization did not follow the pathway of hydrogen transfer, whereby three paraffin molecules are produced for every aromatic molecule formed, which allowed us to obtain carbon selectivity towards chemicals (sum of lower olefins and aromatics) of 70–80 % at 1 bar reaction pressure. Increasing the partial pressure of hydrogen led to substantial hydrogenation of olefins towards paraffins.