The direct production of liquid fuels from CO2 hydrogenation has attracted enormous interest for its significant roles in mitigating CO2 emissions and reducing dependence on petrochemicals. Here we report a highly efficient, stable and multifunctional Na-Fe3O4/HZSM-5 catalyst, which can directly convert CO2 to gasoline-range (C5-C11) hydrocarbons with selectivity up to 78% of all hydrocarbons while only 4% methane at a CO2 conversion of 22% under industrial relevant conditions. It is achieved by a multifunctional catalyst providing three types of active sites (Fe3O4, Fe5C2 and acid sites), which cooperatively catalyse a tandem reaction. More significantly, the appropriate proximity of three types of active sites plays a crucial role in the successive and synergetic catalytic conversion of CO2 to gasoline. The multifunctional catalyst, exhibiting a remarkable stability for 1,000 h on stream, definitely has the potential to be a promising industrial catalyst for CO2 utilization to liquid fuels.

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Directly converting CO 2 into a gasoline fuel

Catalytic transformations of syngas (a mixture of H2 and CO), which is one of the most important C1-chemistry platforms, and CO2, a greenhouse gas released from human industrial activities but also a candidate of abundant carbon feedstock, into chemicals and fuels have attracted much attention in recent years. Fischer-Tropsch (FT) synthesis is a classic route of syngas chemistry, but the product selectivity of FT synthesis is limited by the Anderson-Schulz-Flory (ASF) distribution. The hydrogenation of CO2 into C2+ hydrocarbons involving C-C bond formation encounters similar selectivity limitation. The present article focuses on recent advances in breaking the selectivity limitation by using a reaction coupling strategy for hydrogenation of both CO and CO2 into C2+ hydrocarbons, which include key building-block chemicals, such as lower (C2-C4) olefins and aromatics, and liquid fuels, such as gasoline (C5-C11 hydrocarbons), jet fuel (C8-C16 hydrocarbons) and diesel fuel (C10-C20 hydrocarbons). The design and development of novel bifunctional or multifunctional catalysts, which are composed of metal, metal carbide or metal oxide nanoparticles and zeolites, for hydrogenation of CO and CO2 to C2+ hydrocarbons beyond FT synthesis will be reviewed. The key factors in controlling catalytic performances, such as the catalyst component, the acidity and mesoporosity of the zeolite and the proximity between the metal/metal carbide/metal oxide and zeolite, will be analysed to provide insights for designing efficient bifunctional or multifunctional catalysts. The reaction mechanism, in particular the activation of CO and CO2, the reaction pathway and the reaction intermediate, will be discussed to provide a deep understanding of the chemistry of the new C1 chemistry routes beyond FT synthesis.

New horizon in C1 chemistry: breaking the selectivity limitation in transformation of syngas and hydrogenation of CO2 into hydrocarbon chemicals and fuels

Conversion of CO2 to value-added chemicals has been a long-standing objective, and direct hydrogenation of CO2 to lower olefins is highly desirable but still challenging. Herein, we report a selective conversion of CO2 to lower olefins through CO2 hydrogenation over a ZnZrO/SAPO tandem catalyst fabricated with a ZnO-ZrO2 solid solution and a Zn-modified SAPO-34 zeolite, which can achieve a selectivity for lower olefins as high as 80–90% among hydrocarbon products. This is realized on the basis of the dual functions of the tandem catalyst: hydrogenation of CO2 on the ZnO-ZrO2 solid solution and lower olefins production on the SAPO zeolite. The thermodynamic and kinetic coupling between the tandem reactions enable the highly efficient conversion of CO2 to lower olefins. Furthermore, this catalyst is stable toward the thermal and sulfur treatments, showing the potential industrial application.

Highly Selective Conversion of Carbon Dioxide to Lower Olefins

The discovery of improved chemical processes for CO and CO2 hydrogenation to valuable hydrocarbon fuels and alcohols is of paramount importance for the chemical industry. Such technologies have the potential to reduce anthropogenic CO2 emissions by adding value to a waste stream, whilst also reducing our consumption of fossil fuels. Current thermal catalytic technologies available for CO and CO2 hydrogenation are demanding in terms of energy input. Various alternative technologies are now being developed for COx hydrogenation, with solar-driven processes over two-dimensional (2D) and 2D-related composite materials being particularly attractive due to the abundance of solar energy on Earth and also the high selectivity of defect-engineered 2D materials towards specific valuable products under very mild reaction conditions. This review showcases recent advances in the solar-driven COx reduction to hydrocarbons over 2D-based materials. Optimization of 2D catalyst performance demands interdisciplinary research that embraces catalyst electronic structure manipulation and morphology control, surface/interface engineering, reactor engineering and density functional theory modelling studies. Through improved understanding of the structure–performance relationships in 2D-related catalysts which is achievable through the application of modern in situ characterization techniques, practical photo/photothermal/photoelectrochemical technologies for CO and CO2 reduction to high-valuable products such as olefins could be realized in the not-too-distant future.

Two-dimensional-related catalytic materials for solar-driven conversion of COx into valuable chemical feedstocks.

Catalytic C1 chemistry based on the activation/conversion of synthesis gas (CO+H2 ), methane, carbon dioxide, and methanol offers great potential for the sustainable development of hydrocarbon fuels to replace oil, coal, and natural gas. Traditional thermal catalytic processes used for C1 transformations require high temperatures and pressures, thereby carrying a significant carbon footprint. In comparison, solar-driven C1 catalysis offers a greener and more sustainable pathway for manufacturing fuels and other commodity chemicals, although conversion efficiencies are currently too low to justify industry investment. In this Review, we highlight recent advances and milestones in light-driven C1 chemistry, including solar Fischer-Tropsch synthesis, the water-gas-shift reaction, CO2 hydrogenation, as well as methane and methanol conversion reactions. Particular emphasis is placed on the rational design of catalysts, structure-reactivity relationships, as well as reaction mechanisms. Strategies for scaling up solar-driven C1 processes are also discussed.

From Solar Energy to Fuels: Recent Advances in Light-Driven C1 Chemistry.

Zn- and Na-modulated Fe catalysts were fabricated by a simple coprecipitation/washing method. Zn greatly changed the size of iron species, serving as the structural promoter, while the existence of Na on the surface of the Fe catalyst alters the electronic structure, making the catalyst very active for CO activation. Most importantly, the electronic structure of the catalyst surface suppresses the hydrogenation of double bonds and promotes desorption of products, which renders the catalyst unexpectedly reactive toward alkenes-especially C5+ alkenes (with more than 50% selectivity in hydrocarbons)-while lowering the selectivity for undesired products. This study enriches C1 chemistry and the design of highly selective new catalysts for high-value chemicals.

Cong Xu

Papers

Highly Tunable Selectivity for Syngas-Derived Alkenes over Zinc and Sodium-Modulated Fe5 C2 Catalyst.