Production of Levulinic Acid from Glucose by Dual Solid-Acid Catalysts

Levulinic acid (LA) is a versatile specialty chemical usable as a building-block for synthesis of various chemicals. In this study, a series of solid Lewis acid catalysts were prepared and tested for glucose to fructose isomerization. We also tested Amberlyst-15, primarily a Bronsted solid acid with limited-sites of Lewis acid, to investigate conversion of fructose to LA. Among the Lewis solid acid catalysts tested, tin imbedded on large-pore zeolite (Sn-Beta) has shown the highest specific activity in isomerization of glucose to fructose in aqueous media. The concurrent use of the dual-catalysts of Sn-beta and Amberlyst-15 was further investigated. The dual-acid catalyst has improved the yield of LA over that of Amberlyst-15 alone, from 37 to 45% of the theoretical maximum. The improvement was due to enhanced isomerization of glucose to fructose by Sn-Beta. Stability tests have shown that the Sn-beta zeolite catalyst loses 20% of its activity after five consecutive batch-cycles. The activity of this catalyst, however, was fully regenerated by calcination. Ambelyst-15 also suffers from deactivation, which is lower than that of Sn-Beta. The deactivation is primarily due to humin deposit on the surface of the catalyst. (C) 2017 American Institute of Chemical Engineers