Preparation of ethyl levulinate from wheat stalk over Zr(SO(4))(2)/SiO(2)

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 temperature-programmed 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(SO(4))(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.