焙烧温度及焙烧时间对异丁烯部分氧化合成甲基丙烯醛催化剂性能的影响

Effect of Calcination Temperature and Time on the Properties of Catalysts for the Partial Oxidation of Isobutylene to Methacrolein

采用沉淀法制备了Mo-B i-Co-Fe-Cs复合氧化物催化剂,并用于异丁烯部分氧化制备甲基丙烯醛反应,结合H2-TPR、XRD、BET和TEM表征,考察了焙烧温度以及焙烧时间对催化剂物理化学性质及催化性能的影响.研究结果表明,随焙烧温度升高,催化剂物相结构没有明显的改变,而催化剂颗粒则逐渐增大,氧化能力降低,且组分之间的协同作用减弱;当焙烧温度提高到540℃时,催化剂局部颗粒已出现烧结.催化剂活性随焙烧温度提高逐渐下降,而甲基丙烯醛选择性则在焙烧温度为520℃时达到最大值,焙烧温度对催化剂性能的影响可能因催化剂表面活性位密度不同所致.合适的焙烧温度为520℃,焙烧时间为5 h,此时异丁烯转化率为98.4%时,MAL选择性可达到87.2%,具有较好的反应效果.

The composite oxides of Mo-Bi-Co-Fe-Cs were synthesized by precipitation method and applied in the partial oxidation of isobutylene to methacrolein. The effect of calcination temperature and time on the physieochemical properties of catalysts were studied by H2-TPR, XRD, BET, and TEM. It was found that, as the calcination temperature increased, the structure of the catalyst changed slightly and the particle size increased gradually and synergy between components weakened. When calcinated at 540 ℃ , the catalyst particles were partially sintered. The catalytic activity decreased gradually with increasing calcination temperature and methacrolein selectivity reached the maximum value at 520℃. The effect of calcination temperature on catalytic performance could be attributed to the different density of surface active site. The proper calcination temperature was suggested at 520℃ and calcination time was 5h. With this method, the isobutylene conversion rate was 98.4% and selectivity to MAL was 87.2%.