【Frontiers in HaiChuan Chemical Technology】Anhui University of Technology develops a new type of \"metal oxide-molecular sieve\" composite catalyst and proposes a new process for the synthesis of p-xylene

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Recently, the team led by Professor Zeng Jie from Anhui University of Technology, in collaboration with the team led by Fanli Chun from Toyama University in Japan, developed a new type of \"metal oxide-molecular sieve\" composite catalyst. By utilizing a multi-step catalytic process, they succeeded in directly synthesizing p-xylene from carbon dioxide and hydrogen, achieving a world record for space-time yield per reaction step. On June 10th, Beijing time, this research finding was published in the international academic journal Journal of the American Chemical Society. p-Xylene is a key raw material for producing chemical products such as polyester fibers. Currently, the common method for industrially synthesizing p-xylene is based on the catalytic reforming of heavy oil; approximately 4 tons of oil are consumed per ton of p-xylene produced, with around 3 tons of carbon dioxide being emitted in the process. Using renewable energy to electrolyze water to produce hydrogen, which is then reacted with carbon dioxide to directly manufacture p-xylene, holds promise for enabling the sustainable utilization of greenhouse gas carbon dioxide, while offering an alternative to traditional production processes that are highly energy-intensive and emit large amounts of pollutants. It is understood that the composite catalyst developed by the research team consists mainly of two modules. Among them, the metal oxide module is responsible for catalyzing the hydrogenation of carbon dioxide to produce short-chain alkenes, while the molecular sieve module facilitates the polymerization, cyclization, and aromatization of these short-chain alkenes, ultimately yielding p-xylene. To improve the selectivity for p-xylene, the research team carried out a meticulous design to \"encapsulate\" the molecular sieve modules. Its internal hollow structure can effectively promote the mass transfer of intermediates. At the same time, the pore size of the molecular sieve matches that of p-xylene molecules, allowing it to specifically promote the diffusion of p-xylene products from the inside outward. Furthermore, the research team also passivated the outer surface of the \"capsules\" to prevent further side reactions such as isomerization and alkylation of the produced p-xylene. Thanks to this unique design, the research team has raised the one-way space-time yield of p-xylene to a new level; 1000.8 grams of p-xylene can be obtained by using 1000 grams of the composite catalyst for one day of operation, which far exceeds the performance levels reported in existing scientific literature. The researchers say that the composite catalyst design they proposed could also be applied to other carbon dioxide hydrogenation reaction systems, thereby enabling the \"tailored\" adjustment of the carbon chain length and molecular size of high-value-added products.