Scientists create new materials for high-efficiency propane dehydrogenation catalysis

Recently, the team of Professor Wu Peng of the School of Chemistry and Molecular Engineering of East China Normal University has made important progress in the field of efficient catalytic propane dehydrogenation of molecular sieve pore confinement metal catalysts. Facing the actual demand for high-activity, high-selectivity and high-stability precious metal catalysts for propane dehydrogenation to propylene, an important industrial reaction, the research group created an ultra-large microporous silicon germanium zeolite confined-anchored platinum (Pt) cluster catalyst, which used the strong interaction between zeolite skeleton metal and Pt to realize the long-term operation of propane dehydrogenation and highly selective propylene production reaction. On June 12, the study was published online in Nature Catalysis.

Sub-nanometer Pt clusters in the pore channel. Photo courtesy of East China Normal University

Propylene is one of the most important olefins in the chemical industry, used in the production of a variety of bulk chemicals, including polypropylene, acrylonitrile, acrylic acid, acetone and propylene oxide. Platinum-based catalysts, which are widely used in propane dehydrogenation to propylene, face many problems such as high manufacturing cost, easy agglomeration and sintering, and rapid inactivation of catalytic performance at high temperature. Therefore, the development of new catalysts with ideal catalytic activity, high selectivity and long-term durability has important academic and application value. Wu Peng’s team developed a UTL-type silicon-germanium zeolite pore limited Pt sub-nanometer cluster metal catalyst, cleverly used a special germanium-rich biquaternary ring structure (d4r) in a silicon-germanium zeolite (UTL) to induce anchoring guest Pt, and used sub-nanometer Pt cluster to construct a host-guest bimetallic structure catalyst, which greatly improved the catalytic performance of propane dehydrogenation, and had high activity, high propylene selectivity and high durability, which was very promising for industrial applications.

The catalyst achieves a stable conversion of more than 54% propane and more than 99% propylene selectivity at a reaction temperature of 500 oC. In the experiment, the catalyst continued to be stable for 4200 hours under different propane partial pressure, airspeed and reaction temperature. In order to meet the needs of industrial applications, the research group also evaluated the long-term dehydrogenation performance of pure propane feed and 580 oC/600 oC high temperature conditions, and the results showed that the catalyst had industrial application prospects.

The research group used integral differential phase contrast imaging scanning transmission electron microscopy to confirm that sub-nanoscale Pt clusters were specifically located in the 14-membered ring pores of the UTL, indicating that Pt occupied a specific position in the UTL pores, which was related to the large pore size of the 14-membered ring pores and the local enrichment of the skeleton Ge (germanium) in the bi-quaternary ring structural units.

The results showed that the catalyst had an almost negligible contribution to the scattering path of the Pt-Pt bond, indicating that the size of the Pt in samples with high Ge content was extremely small (the coordination number of Pt-Pt bonds was approximately 3). This proves that Pt is anchored to Ge-UTL zeolite by a special form of chemical bonding. In addition, no scattering path signal of the Ge-Ge bond was observed, indicating that the skeleton Ge was not reduced and remained an atomically dispersed skeleton Ge site. Further studies determined that directional anchoring and placement of Pt is achieved through chemical interaction with the skeleton Ge in the biquad ring structure. It was demonstrated that a completely new active site can efficiently catalyze the dehydrogenation of propane to propylene. (Source: China Science News, Zhang Shuanghu, Huang Xin)

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