Efficient Ni2P/WO3-ZrO2 bifunctional catalysts for the hydrodeoxygenation and hydroisomerization of stearic acid

In this paper, novel Ni2P/WO3-ZrO2 bifunctional catalysts are prepared by an isovolume impregnation method. A series of characterizations (e.g., Py-IR, TEM, and XPS) demonstrated that the introduction of WO3 resulted in the acidity of the carrier and the formation of a well-dispersed Ni2P crystalline phase. The hydrodeoxygenation and hydroisomerization properties were evaluated by single-factor experiments using stearic acid as a model compound. Under the same conditions (solvent-free and relatively mild), the product obtained with a low amount of catalyst (stearic acid:catalyst = 40:1 wt.%) has a high deoxygenation rate (> 96%). The addition of an acidic carrier also gave the catalyst excellent hydroisomerization properties, which were excellent for increasing the low-temperature fluidity of the biodiesel. In addition, the effects of catalyst dosage, H2 pressure, reaction temperature, and reaction time on the hydroisomerization of stearic acid were investigated using the response surface method. In the response surface experiments, the deoxygenation rate of all experimental products is above 98%. The increase in catalyst dosage, reaction temperature, and decrease in H2 pressure favored the increase in isoparaffin content, and the reaction time had the least effect. The isoparaffin content varied significantly in response surface experiments, with molar ratios in the product ranging from 3 to 30%. There are interactions between the independent variables and a high coefficient of determination of the regression model (R2 = 0.9729), indicating that the experimental results were in good agreement with the model predictions.