异丁烯选择氧化制备甲基丙烯醛催化剂

Catalyst for Selective Oxidation of Isobutylene to Methacrolein

采用共沉淀法制备了掺杂 Sb 的 Mo-Bi-Fe-Co-Cs-Ce-K-O 混合氧化物催化剂,并将该催化剂用于异丁烯(IB)选择氧化制备甲基丙烯醛(MAL);采用 X 射线衍射和 BET 法对催化剂进行了表征,并在固定床反应器中考察了 Sb 添加量、气态空速、V(IB):V(空气)对催化剂性能的影响。实验结果表明,掺杂 Sb 的 Mo-Bi-Fe-Co-Cs-Ce-K-O 催化剂的成分为CoMoO_4,Bi_2Mo_3O_(12),FeMoO_4,Bi_2Mo_2O_9;Sb 的掺杂改变了 Bi_2Mo_3O_(12)的晶体结构,进而影响催化剂的性能,抑制了产物 MAL 的过度氧化,提高了 MAL 的收率。当 n(Sb):n(Mo)=0.03时,催化剂的性能最好,此时催化剂的组成为 Mo_(12)Bi_(1.6)Fe_1Co_8Ce_(0.4)·Cs_(0.4)K_(0.2)Sb_(0.36),在该催化剂用量5 mL、反应温度380℃、气态空速4 500 h^(-1)、V(IB):V(空气)=6:94的最优反应条件下,IB 的转化率为95.3%,MAL 的选择性和收率分别为71.7%,68.3%。

Sb-doped Mo-Bi-Fe-Co-Cs-Ce-K-O composite oxide catalyst was prepared by coprecipitation and was used in selective oxidation of isobutene to methacronlein （MAL）. The composition and microstructure of Mo-Bi-Fe-Co-Cs-Ce-K-Sb-O catalyst was characterized by XRD and BET. Effects of Sb dosage, GHSV and volume ratio of isobutene to air on activity of catalyst were studied in a fixed bed reactor. Constituent of Sb-doped Mo-Bi-Fe-Co-Cs-Ce-K-O composite oxide catalysts are found to be CoMoO4 ,Bi2Mo3O12, FeMoO4 and Bi2Mo2O9. Doping of Sb to the catalyst leads to distortion of Bi2Mo3O12, which affects the catalytic performance and inhibits over-oxidation of product MAL, so higher MAL yield is achieved. Under optimized reaction conditions： catalyst dosage 5 mL, mole ratio of Sb to Mo 0.03 （composition of catalyst is Mo12Bi1.6Fe1Co8Ce0.4Cs0.4K0.2Sb0.36） , reaction temperature 380 ℃, GHSV 4 500 h ^- 1 and volume ratio of isobutene to air 6 ： 94, conversion of isobutylene, selectivity and yield to MAL are 95.3 %, 71.7 %, and 68.3 %, respectively.