The development of efficient and sustainable catalytic processes is a key challenge in modern chemical engineering. As global demand for chemical building blocks such as propylene continues to grow, new technologies are needed to optimize their production. One promising method to produce propylene is the direct dehydrogenation of propane (PDH). However conventional heterogeneous platinum-based catalysts used in industrial scale PDH suffer from rapid deactivation due to coke formation, necessitating frequent regeneration and reducing overall process and cost efficiency.
One approach to improving general resistance of the dehydrogenation catalyst against coking and therefore reducing overall propylene productions costs lies in the use of Supported Catalytically Active Liquid Metal Solutions (SCALMS). These materials combine the benefits of homogeneous and heterogeneous catalysis, allowing for high-temperature operation and providing a dynamic reaction interface that enhances catalytic activity. Unlike conventional solid catalysts, SCALMS consist of liquid alloy droplets typically comprised of a catalytically active metal e.g. platinum (Pt) in an excess of low melting point metal e.g. gallium (Ga) dispersed on a solid support. The materials liquid nature at reaction conditions allows for atomic mobility inside the matrix, facilitating continuous interface renewal, subsequently reducing the likelihood of deactivation through coke deposition. Importantly, previous simulations suggest that SCALMS allow for single-atom catalysis, where individual active metal atoms temporarily migrate to the surface to facilitate C-H bond breakage and are then reabsorbed. Thereby side reactions such as cracking of propane, which require two catalytically active sites, could be suppressed, improving overall selectivity in comparison to traditional PDH catalyst.
In order to investigate the activity and coking behavior of GaPt-SCALMS catalysts during propane dehydrogenation (PDH) our group conducted two complementary in-situ studies. High-resolution thermogravimetric analysis coupled with a Hiden HPR‑20 EPIC mass spectrometer was used to monitor coke formation and gas-phase composition in real time. In this setup, GaPt/SCALMS catalysts supported on either SiO₂ or Al₂O₃ were employed for PDH, revealing significantly higher coke formation on Al₂O₃-supported catalysts, indicated by early and sustained weight increases and elevated H₂ and CO₂ signals. These findings point to the critical role of the support’s acidity in accelerating carbon deposition.
Simultaneously, a compact profile reactor (CPR) enabled spatially resolved kinetic measurements along the catalyst bed at temperatures from 450 °C to 550 °C. Results showed that propane conversion increased along the bed but declined over time due to catalyst deactivation. Notably, a deactivation front was observed moving from the bed outlet toward the inlet, likely caused by local coke accumulation. Despite this, the SiO₂-supported catalyst maintained high selectivity and exhibited only moderate coking, demonstrating the potential of SCALMS for stable high-temperature PDH applications.
Project Summary by: Christian Schweiger, Dr. Patrick Schühle and Prof. Dr. Marco Haumann. Friedrich Alexander Universität, Erlangen, Germany.
Paper Reference: Wolf, M.; Raman, N.; Taccardi, N.; Horn, R.; Haumann, M.; Wasserscheid, P. Capturing Spatially Resolved Kinetic Data and Coking of Ga–Pt Supported Catalytically Active Liquid Metal Solutions during Propane Dehydrogenation in Situ. Faraday Discuss 2021, 229 (0), 359–377. https://doi.org/10.1039/D0FD00010H.
Product: HPR-20 EPIC
