Development of hydrophobic catalysts for reducing the CO2 emission during the conversion of syngas into chemicals and fuels

Syngas conversion is a key process for the production of chemicals and fuels from non-petroleum resources, such as biomass, coal, and natural gas. Water produced during syngas conversion can not only boost the production of CO₂ by-products via inducing the water-gas shift side reaction, but also inhibit the conversion of CO by occupying the active sites on the catalyst, leading to high CO₂ emission and low carbon utilization efficiency. Reducing CO₂ emission during syngas conversion is a main development direction of the energy chemical industry toward the goal of carbon neutrality. It has been reported that hydrophobic modification can reduce a surface's affinity to water molecules, and many breakthroughs in the development of hydrophobic catalysts for weakening the negative effect of water on syngas conversion have been made recently. A rapidly growing number of studies have demonstrated the versatility of hydrophobic catalysts. In this review, we systematically summarize and discuss the development of hydrophobic catalysts in syngas chemistry since the 2000s. These hydrophobic catalysts can be divided into three categories, i.e., catalysts with hydrophobic surfaces, catalysts with hydrophobic supports, and catalysts physically mixed with hydrophobic promoters. Different categories of hydrophobic catalysts play different roles in syngas conversion. The perspectives and challenges for the future design of hydrophobic catalysts are also discussed.