Insights into the kinetics of ethyl levulinate production from cellulosic biomass alcoholysis under high solid content

Abstract

Insight into the alcoholysis kinetics of cellulosic biomass under high solid content to high-value-added ethyl levulinate (EL) is of great significance, but remains challenging due to the co-existence of homogeneous and heterogeneous processes. Herein, the alcoholysis of cellulosic biomass to EL in high solid content systems using CuSO₄ as a catalyst was investigated, employing microcrystalline cellulose (MC) as a model compound and xylose residue (XR) as a real cellulosic biomass. Under solid content of 15 %, the yield and concentration of EL from MC reached 29.50 wt% and 35.01 g/L, respectively, and the yield and concentration of EL from XR could reach 22.77 wt% and 27.01 g/L, respectively. A hybrid model consisting of a shrinking-core model and a pseudo-first-order model was established for the first time. The kinetic data analysis revealed that the reaction rate followed the order of 5-ethoxymethylfurfural → EL > glucose → ethyl glucoside > ethyl glucoside → 5-ethoxymethylfurfural > XR → glucose. Meanwhile, there is no significant dependence between the activation energies and the biomass solid content. The activation energies of XR → glucose, a rate-limiting step of the whole alcoholysis, are in the range of 91.30–94.72 kJ/mol under the condition of solid content ranging from 15 % to 25 %. The lower activation energies indicate the potential of XR as a promising raw material for EL preparation.