On July 22, Science published online a Perspective article entitled “Improving catalysis by moving water” by Professor Ding Mingyue from the School of Power and Mechanical Engineering and the Institute of Technological Sciences, Wuhan University. The article reviews and discusses the importance of hydrophobic strategies for efficient syngas conversion, recent research progress and future directions.
Low carbon olefins (ethylene, propylene, butylene) are important building blocks in modern chemical industry, and their industrial production mainly depends on petroleum. Coal can be converted into various liquid fuels (gasoline, diesel, aviation fuel) and bulk chemicals (olefins, aromatics, alcohols) by syngas platform (CO and H2), which is a key technology to alleviate the shortage of petroleum resources and realize the clean and efficient utilization of coal in China. The complete process of coal-to-oil has already achieved large-scale industrial application in China. But the direct production of low carbon olefins from coal via syngas is still in the R&D (research and development) stage, the core of which lies in the design of catalysts to efficiently convert syngas into low carbon olefins.
Water is a by-product in syngas conversion reactions and can limit the catalytic efficiency of syngas to low carbon olefins by covering the catalytic active site or inducing side reactions. Recently, a collaboration between the Xiao Fengshou/Wang Liang team from Zhejiang University and the Zheng Anmin team from the Institute of Precision Measurement, CAS (Science2022,377,406-410) reported that the physical mixing of a hydrophobic additive PDVB (polydivinylbenzene) and CoMn catalyst resulted in a significant increase in CO conversion from 32% to 64% in the reaction. CoMn/PDVB has the advantages of mild reaction conditions and good selectivity for low carbon olefins, while PDVB acts as a hydrophobic water channel to accelerate the diffusion of water molecules and weaken the competition between water molecules and CO adsorption on CoMn catalysts, thus exposing more catalytic active sites on CoMn catalysts and improving the conversion efficiency of syngas to low carbon olefins.
Previously, Ding Mingyue’s team reported a “chemically modified” hydrophobic strategy (Science 2021, 371, 610-613): the FeMn catalyst was coated with a layer of silica and further modified by silylation to obtain a hydrophobic FeMn@Si catalyst. It was found that the surface silica hydrophobic layer could protect the activity of iron carbide from the oxidation of water, making it in a good stable state in the reaction phase. At the same time, the hydrophobic layer on the catalyst surface prevented the water from contacting the iron species in the nucleus layer, which in turn inhibited the water gas conversion side reaction (CO + H2O → CO2 + H2), consequently reducing the selectivity for CO2 in the product from about 45% to about 13% on the conventional catalyst and significantly cutting the carbon emission in the syngas-to-olefin process.
Combining the hydrophobic strategies of “physical mixing” and “chemical modification” to develop new high-efficiency catalysts with high CO conversion and low CO2 by-product selectivity will significantly reduce the production costs and carbon emissions in the preparation of various liquid fuels and bulk chemicals from coal via the syngas platform, unlocking the full potential of the process, greatly promoting the development of clean and efficient coal utilization technology in China, and providing new solutions to achieve the goal of “carbon peaking and carbon neutrality”.
This project was supported by the National Natural Science Foundation of China (21978225, U21A20317).
Links to papers: https://www.science.org/doi/10.1126/science.adc9414
Rewritten by Wang Lu
Edited by Zhou Chuangyu, Sylvia, Xi Bingqing
