Hydrogenation of sunflower oil over platinum supported on silica catalysts: Preparation, characterisation and catalytic activity

The effect of varying the Pt content (0.7 - 4.6 wt %) over a novel mesoporous SiO₂ support was investigated for hydrogenation of sunflower oil. The reaction was carried out in a batch reactor at 170 °C, 400 rpm and 3 bar hydrogen pressure. The activity and selectivity of the different catalysts to trans fatty acid formation were compared. The choice of metal precursor affected the catalyst activity, H₂PtCl₆ showed a moderate increase of the Pt activity compared to Pt(AcAc)₂. The presence of chlorine on a supported catalyst is believed to give rise to improved hydrogen spillover, which in turn may improve the hydrogenation activity. For the catalysts prepared using Pt(AcAc)₂, the activity improved with increased Pt loading up to 1.5%Pt, above which no significant increase in activity was observed with additional Pt loading. Additionally, it was found that the activity per exposed metal was greater at lower Pt loadings. The amount of Pt supported on the silica was shown to influence the selectivity to trans_C18:1. Increasing the Pt loading from 0.7% to 4.6% correspondingly decreased the metal dispersion and increased the metal particle size. The smaller particles on the 0.7%Pt/SiO₂, 1.5%Pt/SiO₂ and the 2.7%Pt/SiO₂ catalysts presented a lower trans content compared to the 4.6%Pt/SiO₂ catalyst that exhibited larger particles.