(610b) Tandem Hydroformylation-Hydrogenation of Olefins to Alcohols Using Supported Catalysts

Alcohols are important class of products that find application as intermediates in organic synthesis for agrochemicals, detergents, pharmaceuticals, or as oxygen containing compounds blended into fuels. In most of the cases, these valuable materials are produced in two separate steps from terminal alkenes, namely by a hydroformylation reaction followed by hydrogenation of the resulting aldehyde. Recently, it has been shown that homogenous Rh/Ru based molecular catalysts can perform the tandem conversion of olefins to alcohols with greater than 90% selectivity to alcohols [1]; however, heterogeneous or heterogenized catalysts are more advantageous in an economical and ecological point of view.

We synthesized heterogenized Rh-sulfoxantphos (SX) containing-supported ionic liquid phase (SILP) catalyst for the alkene hydroformylation and Shvo’s catalyst supported on silica (Shvo/SiO₂) for the conversion of propene to butanols. Characterization results suggest that active Rh-SX centers are not present as homogeneous complexes dissolved in an ionic liquid film, but instead are present as HRh(CO)₂SX complexes bound to the support by interactions of the sulfonate groups of SX with silanol groups of the support [2]. The activity and stability of Rh-SX SILP catalysts are strongly influenced by ligand and ionic liquid composition, ligand-to-rhodium ratio, and the surface density of silanol groups on the silica support. For example, the hydroformylation of propene at 393 K and 2 atm pressure using Rh-sulfoxantphos (SX/Rh=10) in [bmim][OctSO₄] ionic liquid exhibits a turnover frequency of 100 h^-1 and a regioselectivity (n/iso) ratio of 14.

It is known that hydrogenation promoted by Shvo’s catalyst operates through an outer sphere mechanism [3]. Hence selective hydrogenation of the polar double bond of aldehyde (C=O) occurs over the co-existing olefins (C=C) during tandem process. Results from our experiments indicate that a combination of Rh-SX SILP catalyst and Shvo/SiO₂ can perform the tandem conversion of propene to butanols with 15% propene conversion and greater than 90% selectivity to butanols at 413 K and a total pressure of 3 atm. The insights learned from this study provide important contributions to the production of butanols from light olefins since butanols can preform as a clean gasoline additive.

[1] K. Takahashi, M. Yamashita, T. Ichihara, K. Nakano, K. Nozaki, Angew. Chem. Int. Ed. 49 (2010) 4488-4490

[2] S. Shylesh, D. Hanna, S. Werner, A. T. Bell, ACS Catal. 2 (2012) 487-493

[3] Y. Shvo, D. Czarkie, Y. Rahamim, D. F. Chodosh, J. Am. Chem. Soc. 108 (1986) 7400-7403.