Solventless synthesis of solketal with commercially available sulfonic acid based ion exchange resins and their catalytic performance

Abstract

Abstract As a means to valorize glycerol, the synthesis of solketal through a ketalization reaction with acetone was performed. Mild solventless conditions were applied to test the activity of different commercially available sulfonic ion exchange resins that had already been used for other applications, namely: Amberlyst 35dry, Amberlyst 36dry, Purolite CT275DR, Purolite CT276 and Lewatit GF101. Thorough characterization of the resins is herein provided and discussed, including acidity, elemental analysis, thermogravimetric, 13C-NMR, surface area and pore size distribution measurements. Lewatit GF101 showed the best performance reaching a yield to solketal of 47% after 6 h of operation at 313 K using a molar excess of acetone to glycerol of 4.5 to 1, owing to a greater availability of active centers as well as the ease of access to them than in the rest of the resins. Additionally, reutilization with and without regeneration was performed in up to five cycles, showing that Purolite CT276 had the lowest relative drop of its maximum activity, despite being the least active in each of the cycles.