Catalytic Conversion of Carbohydrates to Methyl Lactate Using Isolated Tin Sites in SBA-15

A series of Sn-SBA-15 catalysts were synthesized using a post-synthetic metal implantation method for converting carbohydrates to methyl lactate. The tin species were highly dispersed and isolatedly grafted in the framework of SBA-15 under the tin salt concentration between 2 and 25 wt%. They solely provided a large number of Lewis acid sites, which showed robust activity for carbohydrates conversion in contrast to the performance of tin dioxide domains or particles. Over a Sn-SBA-15 catalyst (Si/Sn molar = 150), the Lewis acid density was 45.9 mmol/g, and methyl lactate yield reached a high value of 57.0% from inulin conversion in methanol at 433 K for 20 h, without the formation of methyl levulinate by-product. The Sn-SBA-15 catalysts were rather stable under reaction conditions, and cycled at least for 4 times without deactivation.