Mitigation of cation exchange resin deactivation in the one-pot conversion of fructose to methyl levulinate†

Abstract

Cation exchange resins represent an important family of solid acid organic catalysts that have been used to convert different biobased feedstocks. In this context, cation exchange resins have been previously investigated in the synthesis of alkyl levulinates, an important biobased platform chemical, but obtained mainly from sugar-downstream chemicals such as levulinic acid or furfuryl alcohol. So far, their utilization as catalysts for the one-pot conversion of sugars to alkyl levulinates has hardly been investigated, this reaction being dominated by inorganic catalysts. One of the main reasons stems from their irreversible deactivation during the catalytic reaction. Although one previous article demonstrated that gel-type cation exchange resins were more prone to catalyzing this one-pot reaction, much less is known about their deactivation, a scientific obstacle which we study in this report. By assessing the impact of different reaction parameters on more than 13 different cation exchange resins, we discovered conditions for which it was possible to drastically limit the deposition of humins on cation exchange resins. In methanol, and under optimized conditions, we found that Purolite C124 SH exhibited the best catalytic performance, leading to methyl levulinate in 86% yield from fructose, and it can be successfully recycled 10 times without an apparent decrease in its catalytic efficiency.