Insight into the reaction route and the effect of Brønsted and Lewis acid for alkylation of 5-Hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) can be upgraded to ether as fuel or fuel additives through conversion of the hydroxyl and aldehyde groups. The two groups are always involved in different catalytic reactions, such as etherification, acetalization, hydrogen transfer reduction, and even ring-opening reactions. This makes the etherification upgrading of HMF with high selectivity to desired product a great challenge. In the present wok, transformation of HMF in isopropanol was systematically investigated over different catalysts with Brønsted acid and Lewis acid sites. The effect of catalytic sites on product distribution and selectivity was studied. Moreover, several products, such as 5-isopropoxymethylfurfural, 5-isopropoxymethylfurfuryl alcohol, 5-isopropoxymethylfurfuryl alcohol, and 2,5-furandimethanol, were obtained with high selectivity, and the conversion pathway of HMF with alcohols on different catalytic sites was revealed under different catalytic conditions. The transformation of HMF to furan triether products over multi-site catalyst was realized for the first time based on the proposed reaction pathway with excellent activity and selectivity.