Glucose-derived bio-fuel additive via ethanolysis catalyzed by zinc modified sulfonated carbon

Abstract

The transformation of biomass derivative components such as glucose to levulinate esters via direct conversion in alcohol with acid catalyst has attracted great attention. In this study, the sulfonate urea-furfural carbon cryogel doped with zinc (UFCS-Zn) has been applied as an acid catalyst for the glucose ethanolysis reaction. Initially, the carbon cryogel was prepared via a mixing process of urea and furfural in an acidic medium followed by freeze-drying and calcination steps. Then, the urea-furfural carbon cryogel (UFC) was sulfonated before modification with zinc via impregnation of zinc (II) nitrate to provide the Bronsted and Lewis acid catalyst which is required for reaction conversion. The effects of reaction parameters on the ethanolysis of glucose have been conducted to determine the selected condition in obtaining high ethyl levulinate yield. The parameters studied include the glucose feed (0.2 to 0.5 g), catalyst loading (0.15 to 1.2 g), and reaction temperature (140 to 190 °C). The catalyst was characterized using TGA-DTG, FTIR, and SEM-EDX techniques to study the surface chemistry and thermal stability. The glucose ethanolysis reaction with UFCS-Zn catalyst has provided maximum ethyl levulinate yield of 27.4 mol% at selected condition of 180 °C, 6 h, 0.8 g (1:2) of catalyst and 0.4 g of glucose. Based on characterization of UFCS-Zn, the presence of sulfonate group and Zn element on the catalyst through the sulfonation and impregnation steps have been verified. This result has been confirmed through the detection of SO3H functional group and Zn-O bonding from the FTIR, and elements of S, O, and Zn from the EDX. High thermal stability of the UFCS-Zn (via TGA-DTG curves) allows the catalyst to assist the reaction at setting temperature without degradation in mass during the reaction. The UFCS-Zn catalyst has drafted its potential as catalyst for further conversion of biomass components.