Supercritical ethanolysis of wheat stalk over calcium oxide

Catalysts C600, C700, and C800 prepared from Ca(CH3COO)2 calcination at 600, 700, and 800 °C, respectively, were characterized with an X-ray diffractometer, scanning electron microscope, and specific surface area analyzer. Over the catalysts, bio-oils (BOs) were obtained by the supercritical ethanolysis (SCE) of wheat stalk powder (WSP). Their yields, ultimate analyses, chemical composition and some fuel properties were investigated. WSP and the residues from the SCE of WSP were analyzed with a Fourier transform infrared spectrometer. The results show that C700 has a small particle size and large specific surface area, and can effectively catalyze the SCE of WSP. The BO yields from non-catalytic, C600, C700, and C800-catalyzed SCE of WSP are 30.1, 22.9, 70.7 and 34.4%, respectively. BO700 from C700-catalyzed SCE of WSP has relatively higher H/C and H/O ratios and calorific value but lower acidity, kinematic viscosity, and water content. The relative content of alcohols in the BO obviously increased, while the contents of carboxylic acids, ethyl esters, and anhydrides decreased over C700.