GAS PHASE DEHYDRATION OF GLYCEROL CATALYZED BY Γ-AL₂O₃SUPPORTED HETEROPOLYACID

In order to improve the catalytic performance of catalysts on glycerol dehydration,the active components were selected and the support was modified in the present study.The influence of reaction conditions on the conversion rate of glycerol and the selectivity rate of acrolein was also studied.The catalysts were prepared by the initial wetness impregnation method,with γ-Al₂O₃as support,and H₃PO₄,H₄SiW₁₂O₄₀,H₃PW₁₂O₄₀and H₃PMo₁₂O₄₀as the active components.The catalytic performance of the prepared catalysts on the gas phase dehydration of glycerol to acrolein under atmospheric pressure was examined.The results showed that γ-Al₂O₃supported H₄SiW₁₂O₄₀had excellent catalytic performance on the dehydration of glycerol to acrolein.The conversion rate of glycerol and the selectivity rate of acrolein were 89.19% and 83.61% at 310℃,respectively,when 20% glycerol aqueous solution was fed at a rate of 0.1 mL/min.The γ-Al₂O₃modified by B₂O₃or ZrO₂could improve the catalytic performance of γ-Al₂O₃supported H₄SiW₁₂O₄₀catalyst.The conversion rate of glycerol was reached to 100% and the selectivity rate of acrolein was up to 85.32% at 310℃ with B₂O₃modified γ-Al₂O₃supported H₄SiW₁₂O₄₀as catalyst.Furthermore,the effect of the load amount of H₄SiW₁₂O₄₀,the concentration of glycerol aqueous solution and liquid hourly space velocity on the catalytic performance of prepared catalysts was also investigated.The optimal conditions were as follows:the concentration of glycerol aqueous solution 35%,20% HSiW10% B₂O₃/γ-Al₂O₃as catalyst and the liquid hourly space velocity 2.0 h^-1,under which the glycerol in feed was almost completely converting to products and the selectivity rate of acrolein was higher than 90%.