Selectively converting glucose to fructose using immobilized tertiary amines

•Selective heterogeneous catalyst for isomerization of glucose to fructose.•Systematic experiments into catalyst design that impact catalyst performance.•Optimal catalyst design consists of high organosilane loading of aminomethyl (C1).•Recycle tests determine organosilane leaching, but no amine deactivation for C1.

Glucose isomerization to fructose is an important step in upgrading biomass to higher valued products. Tertiary amines can be highly selective catalysts for this reaction. In this work, tertiary amine analogues were functionalized on a mesoporous silica support to create heterogeneous catalytic materials. Experiments with homogeneous catalysts and silica revealed that silanols reduced the catalytic activity. Through using different strategies to limit amine-silanol interactions, it is determined that tuning parameters such as amine loading and alkyl linker length of the amine tether increases the fructose yield by a factor of four. Among the catalysts tested, the one found to be the best for glucose isomerization has a high amine loading (∼0.95 mmol g−1) with a methyl linker. Catalyst reuse tests demonstrated that organosilane leaching reduced amine content, but the immobilized amines with the methyl linker retained greater catalytic activity than amines with propyl linkers.

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