Evolution of active ingredients and catalytic properties of Pt-Sn/Al2O3 catalysts in the selective deoxygenation reaction of vegetable oils

Abstract

The evolution of the structure of Pt–Sn/Al₂O₃ catalysts and their catalytic properties in the reaction of the reductive deoxygenation of rapeseed oil fatty acid triglycerides (FATGs) have been studied. The catalysts were prepared by deposition from an organic solution of a mixture of platinum and tin compounds, as well as a heterometallic (PPh₄)₃[Pt(SnCl₃)₅] complex, in which platinum and tin atoms are linked by a metal–metal bond. It has been shown that the use of the heterometallic complex as a precursor with a tin to platinum molar ratio of 5 results in the formation of clusters of nanosized tin (2+; 4+) oxides and particles of a metastable PtSn_{3 ± δ} alloy on the surface of the catalyst after reductive activation. In the presence of this catalyst, the exhaustive conversion of the feed FATGs and the selectivity for hydrocarbons above 98% have been achieved. The gaseous products CO, CO₂, and CH₄ are formed in trace quantities. The results show that the deoxygenation occurs not via the known decarboxylation and decarbonylation route, but also through the step of the selective reduction of oxygen and almost complete suppression of cracking of the organic moieties of FATGs.