制备方法对Cr/Si-2催化剂在CO_2氧化乙烷脱氢制乙烯反应中的催化性能的影响

Effect of Preparation Methods on the Performance of Cr/Si-2 Catalysts during the Dehydrogenation of Ethane to Ethylene with CO_2

采用直接水热合成法和浸渍法制备了相同Cr含量的Cr/Si-2催化剂,并在常压固定床微反应器上,考察了它们在CO2或者N2气氛下的乙烷脱氢制乙烯反应中的催化性能及稳定性.由于存在逆水煤气反应和Boudouard反应,CO2能显著促进乙烷的脱氢反应.不论是在CO2还是在N2气氛下,直接水热法制备的催化剂均比浸渍法制备的催化剂显示出更好的催化性能.高价态的Cr物种被认为是催化剂具有高活性的关键.在CO2气氛下的乙烷脱氢制乙烯反应中,浸渍法制备的催化剂比水热法制备的催化剂失活更快,催化剂失活速率的差异可能与它们的氧化还原性质有关.然而在N2气氛下的乙烷脱氢制乙烯反应中,这两种方法制备的催化剂失活速率差异不大.

Dehydrogenation of ethane in the presence or absence of CO2 over Cr/Si-2 catalysts prepared by different methods was investigated. The dehydrogenation of ethane was enhanced by CO2 because of the existence of the reverse water gas shift reaction and the Boudouard reaction. Cr/Si-2DHT catalysts prepared by direct hydrothermal synthesis showed higher catalytic activity compared to Cr/Si-2IMP by impregnation in both the presence and absence of CO2. Chromium species with high oxidation state was considered the key of higher catalytic activity. The different deactivation rate between Cr/Si-2IMP and Cr/Si-2DHT catalysts during the reaction could be correlated with their different redox properties.