Solvent-free selective epoxidation of soybean oil catalyzed by peroxophosphotungstate supported on palygorskite

• The modified palygorskite was used as support of catalysts.
• The catalysts was used for the epoxidation of soybean oil with hydrogen peroxide.
• Mechanical combined ultrasonic agitation was effective to improve catalytic activity.
• The catalyst can be reused for twice with enough catalytic activity.

The acid-activated palygorskite (Pal) and those functionalized with 3-aminopropyltriethoxysilane (PalKH550) were used as supports to immobilize peroxophosphotungstate. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), and the catalytic activity was tested for the epoxidation of soybean oil with hydrogen peroxide. The effect of some factors, such as reaction time, reaction temperature, agitation way and ratio of hydrogen peroxide to soybean oil, was investigated. The results showed that the silylation of Pal during preparation of the catalysts is very effective in improving catalytic activity and mechanical agitation combined with ultrasonic agitation is the best agitation method. Under the optimum condition, the relative percentage conversion to oxirane, the epoxide yield and the epoxide selectivity were 90.69%, 79.34% and 87.48%, respectively.