Bifunctional Rh/Al-SBA-15 catalysed cascade hydroformylation and hydroxyalkylation of alkenes to fuel precursors

Abstract

Decarbonisation of hard-to-abate liquid transport fuels, notably used in the aviation and shipping sectors, requires new catalytic routes to valorise waste feedstocks. Here we report a bifunctional Rh/Al-SBA-15 catalyst for the one-pot, two step cascade hydroformylation of 1-alkenes with CO/H₂ to form linear and branched aldehydes, and their subsequent hydroxyalkylation (HAA) with 2-methylfuran to form oxygenated jet fuel precursors. A strong synergy between Rh and Al-SBA-15 is observed for hydroformylation, with the bifunctional catalyst significantly more active than Rh/SBA-15 for the first step of the cascade. Superior yields of desired HAA products are observed over Rh/Al-SBA-15 relative to a physical mixture of Rh/SBA-15 and Al-SBA-15. Under syngas (CO/H₂) at 30 bar and 80 °C, alkenes undergo Rh catalysed hydroformylation to aldehydes, and in a subsequent step under N₂, HAA of aldehydes over the solid acid sites of Al-SBA-15 gives an overall ∼60% yield of fuel range precursors.