Low-Nuclearity Single-Atom and Supported Metal Cluster Catalysts in Ethylene and Propylene Hydroformylation

Abstract

Olefin hydroformylation is one of the most significant examples of homogeneously catalyzed conversion processes. However, developing chemo/regio-selective and stable solid catalysts has remained a persistent challenge in heterogeneous catalysis. Particularly the design of solid catalysts for the hydroformylation of light, gaseous olefins, such as ethylene and propylene, has been extensively researched, given that the products from these processes are key players in the oxo-chemicals market. Additionally, developing selective, continuous gas-solid C2-3 olefin hydroformylation processes prospectively offers a reactive separation alternative to conventional and massively energy-intensive cryogenic distillation separation methods. In this review, we first assess the potential of reductive olefin hydroformylation as a cost-effective alternative to conventional cryogenic distillation processes for recovering value from industrial gas mixtures of ethylene and propylene. Taking a conventional ethylene splitter as a reference case, a reactive separation through ethylene reductive hydroformylation to 1-propanol is predicted to provide significant savings in terms of utility costs. Next, major advances in the design and development of solid catalysts for ethylene and propylene hydroformylation are surveyed, with an emphasis on single-atom catalysts (SACs) and supported metal nanoclusters. These catalysts have recently achieved hydroformylation activity and chemo/regio selectivity comparable to, or even surpassing, those traditionally exclusive to free molecular catalysts in solution. Different catalyst design strategies, including the heterogenization of metal coordination complexes in supported ionic liquid phase (SILP) catalysts and porous organic ligands (POLs), as well as the tuning of oxide-supported catalysts via the adjustment of metal-oxide interfacial effects or through nanoconfinement within zeolitic frameworks, are systematically reviewed and compared. Finally, conclusions are provided, alongside a critical perspective on fundamental and practical aspects that require particular attention to ensure rational and systematic progress toward optimized catalysts and reaction settings, ultimately paving the way for the heterogenization of light olefin hydroformylation processes.