Effect of Nb doping in WO3/ZrO2 catalysts for gas phase dehydration of glycerol to form acrolein

• Main Authors: Ku-Hsiang Sung, 宋古翔
• Other Authors: Soofin Cheng
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/29077695251854324711

碩士 === 國立臺灣大學 === 化學研究所 === 101 === Biodiesels are fatty acid alkyl esters synthesized by transesterification of triglycerides with excess amounts of short chain alcohols, such as methanol, ethanol and propanol. The increasing production of biodiesels has resulted in over production of glycerol. The cost of biodiesels will be lowered down if glycerol can be used as a feedstock to produce high valued chemicals. Among different processes, the gas-phase dehydration of glycerol to form acrolein is considered to have great economical value. Tungstated zirconia has been found to be efficient catalysts for dehydration of glycerol to form acrolein. However, severe catalyst deactivation over tungstated zirconia was observed due to coke deposition. The aim of this study is to modify the WO3/ZrO2 catalysts by doping small amounts of Nb to decrease the catalytic decay. The acidic strengths of the catalysts measured by NH3-TPD were in the range of weak to moderate. The results of CO2-TPD measurements indicated the doping WO3/ZrO2 with small amounts of Nb can reduce the basic amount by coverd the basic sites of ZrO2 and further increase the stability. The optimal glycerol conversion of 81% and acrolein selectivity of 70% were obtained after 24 h time-on-stream over NbWOx/ZrO2 catalyst with Nb2O5/(WO3 + ZrO2) weight ratios of 3%. The spent catalysts could be easily regenerate by calcination and the catalytic activities were well retained.