Designing the right protection

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.

The Oxygenate-Mediated Conversion of COx to Hydrocarbons─On the Role of Zeolites in Tandem Catalysis

Decentralized chemical plants close to circular carbon sources will play an important role in shaping the postfossil society. This scenario calls for carbon technologies which valorize CO2 and CO with renewable H2 and utilize process intensification approaches. The single-reactor tandem reaction approach to convert COx to hydrocarbons via oxygenate intermediates offers clear benefits in terms of improved thermodynamics and energy efficiency. Simultaneously, challenges and complexity in terms of catalyst material and mechanism, reactor, and process gaps have to be addressed. While the separate processes, namely methanol synthesis and methanol to hydrocarbons, are commercialized and extensively discussed, this review focuses on the zeolite/zeotype function in the oxygenate-mediated conversion of COx to hydrocarbons. Use of shape-selective zeolite/zeotype catalysts enables the selective production of fuel components as well as key intermediates for the chemical industry, such as BTX, gasoline, light olefins, and C3+ alkanes. In contrast to the separate processes which use methanol as a platform, this review examines the potential of methanol, dimethyl ether, and ketene as possible oxygenate intermediates in separate chapters. We explore the connection between literature on the individual reactions for converting oxygenates and the tandem reaction, so as to identify transferable knowledge from the individual processes which could drive progress in the intensification of the tandem process. This encompasses a multiscale approach, from molecule (mechanism, oxygenate molecule), to catalyst, to reactor configuration, and finally to process level. Finally, we present our perspectives on related emerging technologies, outstanding challenges, and potential directions for future research.

Fungi-enabled pore channel regulation and defect engineering of a novel micro-reactor for treating complex effluents

Defect engineering has become a significant research area in recent years; however, little has been reported on the biological method for modulating the intrinsic carbon defects of the biochar framework. Herein, a fungi-enabled method for the fabrication of porous carbon/Fe₃O₄/Ag (PC/Fe₃O₄/Ag) composites was developed, and the mechanism underlying the hierarchical structure is elucidated for the first time. By regulating the cultivation process of fungi on water hyacinth biomass, a well-developed interconnected structure and carbon defects acting as potential catalytic active sites were formed. This new material with antibacterial, adsorption and photodegradation properties could be an excellent choice for treating the mixed dyestuff effluents with oils and bacteria, also guiding pore channel regulation and defect engineering in materials science. Numerical simulations were carried out to demonstrate the remarkable catalytic activity.