Preparation of ethyl levulinate from wheat stalk over $Zr(SO_4)_2/SiO_2$

Abstract

A series of $Zr(SO_4)_2/SiO_2$ solid acid catalysts with different $Zr(SO_4 )_2$ loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of $N_2$ , and temperatureprogrammed desorption of $NH_3$ . The results showed that the active component $Zr(SO_4 )_2$ was successfully adhered to the mesoporous $SiO_2$ , and the acid amount of $Zr(SO_4)_2/SiO_2$ increased with the increasing of the $Zr(SO_4 )_2$ loadings. Finally, the wheat stalk was used as raw material and depolymerized over $Zr(SO_4)_2/SiO_2$ to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% $Zr(SO_4)_2/SiO_2$ exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO4 )2 loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation.