Professor Wang Ye and Professor Fu Gang from the State Key Laboratory of Physical Chemistry of Solid Surfaces at Xiamen University, along with Professor Jiang Zheng from the University of Science and Technology of China, have developed a highly stable catalyst named In/Rh@S-1, boasting a lifespan of over 5500 hours. This catalyst exhibits high selectivity in catalyzing the direct dehydrogenation of low-carbon alkanes such as propane to produce corresponding olefins under near thermodynamic equilibrium conditions. The research findings were published on March 1st in the journal "Science".
Major Breakthrough: High-Stability Rh Single-Atom Alkane Dehydrogenation Catalyst Constructed via Dynamic Migration. Image provided by the research team.
Low-carbon alkenes serve as fundamental raw materials for the synthesis of numerous bulk chemical products such as synthetic fibers, rubber, and plastics, with a global annual demand exceeding 300 million tons. Direct dehydrogenation of alkanes represents a crucial pathway for industrial alkene production, with current commercial technologies mainly controlled by European and American enterprises. However, due to the necessity for harsh high-temperature conditions during the reaction, commercial alkane dehydrogenation catalysts still face issues such as sintering, carbon deposition, frequent catalyst regeneration, and associated high energy consumption and emissions.
Developing metal catalysts that are stable under high-temperature and harsh reaction conditions, while simultaneously exhibiting high activity and selectivity, is a recognized challenge in the catalysis field. Although significant progress has been made by domestic and international scholars in enhancing the stability of propane dehydrogenation catalysts in recent years, deterioration in performance due to the migration of metal elements at high temperatures makes it difficult to achieve continuous stable operation for over 500 hours under near-industrial conditions. Our team led by Professor Wang Ye has taken a different approach by proposing the concept of "in situ dynamic construction of active sites." Leveraging the oxygen affinity and dynamic migration properties of indium (In), we designed In/Rh@S-1 catalysts with dynamically formed and highly stable active sites under reaction conditions. In these catalysts, single Rh atoms are located within the pores of S-1 (Silicalite-1) molecular sieves, and they spontaneously migrate to the channels of the sieve due to interactions with silicon hydroxyl groups, stabilizing the Rh single atoms via In-Rh bonds to form molecular sieve-constrained RhInx active centers. These active centers are further anchored to the molecular sieve framework via In-O bonds. This approach provides a new direction for the design and synthesis of super-stable and efficient single-atom catalysts.
The significant breakthrough of this work lies in the fact that the novel In/Rh@S-1 catalyst can effectively avoid carbon deposition without the need for additional hydrogen to suppress coking, as required in commercial alkane dehydrogenation processes, nor does it require frequent regeneration via air oxidation, making the process simpler and greener. Using pure propane as the feedstock, this catalyst maintained stable activity and selectivity during continuous testing for 5500 hours under near-industrial reaction conditions at 550°C. Under propane conversion rates exceeding 60% at 600°C, the In/Rh@S-1 catalyst demonstrated continuous stable operation for over 1200 hours. Additionally, the single Rh atoms exhibited outstanding C-H activation performance, with propylene production rates based on unit precious metal mass surpassing those reported for Pt-based catalysts by 1-2 orders of magnitude. This work opens up a new catalyst system for alkane dehydrogenation that does not require frequent regeneration, beyond Pt-based and Cr-based systems, with the potential to develop proprietary clean chemical production technologies and contribute to achieving carbon neutrality goals.
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