Tandem Reactions over Zeolite-Based Catalysts in Syngas Conversion

Abstract

Syngas conversion can play a vital role in providing energy and chemical supplies while meeting environmental requirements as the world gradually shifts toward a net-zero. While prospects of this process cannot be doubted, there is a lingering challenge in distinct product selectivity over the bulk transitional metal catalysts. To advance research in this respect, composite catalysts comprising traditional metal catalysts and zeolites have been deployed to distinct product selectivity while suppressing side reactions. Zeolites are common but highly efficient materials used in the chemical industry for hydroprocessing. Combining the advantages of zeolites and some transition metal catalysts has promoted the catalytic production of various hydrocarbons (e.g., light olefins, aromatics, and liquid fuels) and oxygenates (e.g., methanol, dimethyl ether, formic acid, and higher alcohols) from syngas. In this outlook, a thorough revelation on recent progress in syngas conversion to various products over metal-zeolite composite catalysts is validated. The strategies adopted to couple the metal species and zeolite material into a composite as well as the consequential morphologies for specific product selectivity are highlighted. The key zeolite descriptors that influence catalytic performance, such as framework topologies, proximity and confinement effects, acidities and cations, pore systems, and particle sizes are discussed to provide a deep understanding of the significance of zeolites in syngas conversion. Finally, an outlook regarding challenges and opportunities for syngas conversion using zeolite-based catalysts to meet emerging energy and environmental demands is also presented.

Construction of HZSM-5 with a Mesoporous Structure and Suitable Acidity: Application in Catalytic Syngas Conversion to Light Aromatics over Na–FeMn/HZSM-5 Zeolite

“…In addition to Fe-based catalysts, the HZSM-5 zeolite is also critical for converting syngas to aromatics. , The HZSM-5 zeolite is responsible for converting lower olefins into aromatics via dehydrogenation, cyclization, aromatization, and alkylation. , The pore structure, morphology, and acidic properties determine the aromatization ability of a zeolite and the distribution of aromatic products. − In recent years, a host of studies have been reported on the HZSM-5 zeolite. Table S1 compares the performances of various catalysts in syngas conversion to aromatics.…”

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

“…To circumvent the limitation of the Fischer− Tropsch technology, bifunctional materials containing both hydrogenation (mixed metal oxide) and acidic functionality (zeotype) were developed to directly convert syngas to olefins. 4 In this process, the mechanism of olefins formation is different than Fischer−Tropsch and involves hydrogenation of CO/CO 2 to oxygenated intermediates with subsequent hydrocarbon-pool formation in the zeotype and olefin generation (via sequential alkylation and cracking of aromatic and olefinic precursors rather than polymerization of CH x species) (Figure S1).…”

“…1−3 Synthesis gas is a key platform for the transformation of nonpetroleum carbon resources into chemicals, as it can be produced from a wide variety of carbon sources, such as natural gas, coal, biomass, or (plastic) waste. 4 Given the large market share of light olefins within the high value chemicals (approximately 255 MT/yr), extensive research has been devoted to the hydrogenation of CO to light olefins. The Fischer−Tropsch process (FT) is an example of a direct route for the conversion of syngas to (light) olefins.…”

“…Fossil feedstock and carbon footprint reduction have directed extensive research efforts into the development of alternative processes and feedstocks to produce chemicals. − Synthesis gas is a key platform for the transformation of nonpetroleum carbon resources into chemicals, as it can be produced from a wide variety of carbon sources, such as natural gas, coal, biomass, or (plastic) waste . Given the large market share of light olefins within the high value chemicals (approximately 255 MT/yr), extensive research has been devoted to the hydrogenation of CO to light olefins.…”

“…According to this theoretical model, the maximum selectivity of C 2 –C 4 hydrocarbons (including olefins and paraffins) is 58% and is achieved with a chain growth probability (alpha value) between 0.4 and 0.5, which also comes with relatively high undesirable high methane selectivity. To circumvent the limitation of the Fischer–Tropsch technology, bifunctional materials containing both hydrogenation (mixed metal oxide) and acidic functionality (zeotype) were developed to directly convert syngas to olefins . In this process, the mechanism of olefins formation is different than Fischer–Tropsch and involves hydrogenation of CO/CO 2 to oxygenated intermediates with subsequent hydrocarbon-pool formation in the zeotype and olefin generation (via sequential alkylation and cracking of aromatic and olefinic precursors rather than polymerization of CH x species) (Figure S1).…”