Efficient Solvent-Free Synthesis of Sucrose Esters via Sand-Milling Pretreatment on Solid–Liquid Mixtures

A general and efficient method, involving sand-milling pretreatment and base-catalyzed transesterification of sucrose and fatty acid methyl ester (FAME), was presented for the solvent-free synthesis of sucrose esters. A metastable homogeneous paste with a solid particle size of 13 μm ( D 50 ) was obtained by milling at 1000 rpm for 1 h. This reaction mixture generated a total SE yield of 88.2% with a methyl stearate (MS) conversion of 91.4% using K 2 CO 3 as a catalyst at 135 °C for 3 h at a stirring rate of 500 rpm, while those without milling ( D 50 , 153 μm) yielded a total sucrose fatty acid esters (SE) of 49.3% with a MS conversion of 83.1% under the same reaction conditions. The reaction kinetics revealed that the reaction mixture with milling pretreatment displays a shorter induction time and a faster reaction rate for the formation of SE. The promotion of the solvent-free synthesis of SE in the current study could be attributed to the reduction of solid particle sizes and the increased compatibility of solid–liquid phases. We believe that this strategy could be used as a general way for strengthening other heterogeneous reactions in the organic synthesis.