以(NH4)6Mo7O24·4H2O、Bi(NO3)3·5H2O、Fe(NO3)3·9H2O、Co(NO3)2·6H2O和KNO3 为前驱体金属盐,通过共沉淀法制备了一系列MoBiFeCoK混合氧化物催化剂,考察了主金属Mo、Bi,助金属Fe、Co和掺杂金属K含量对催化剂催化异丁烯气相氧化反应的影响,通过SEM、EDX、XRD、NH3-TPD对掺杂K前后的催化剂进行了表征,同时对催化异丁烯气相氧化反应条件进行了优化,并测试其100 h的催化稳定性.结果表明,Bi、Fe、Co 和 K 的含量对 MoBiFeCoK 混合氧化物催化剂催化异丁烯气相氧化反应的性能有显著影响,其中,Mo12Bi1.2Fe3Co8K0.4表现出最优催化性能;K的掺杂降低了催化剂酸量(从Mo12Bi1.2Fe3Co8的15.27 μmol/g降至Mo12Bi1.2Fe3Co8K0.4的5.91 μmol/g),并明显提升主产物甲基丙烯醛(MAL)的选择性;异丁烯气相氧化反应的最佳条件为:以0.66 g Mo12Bi1.2Fe3Co8K0.4为催化剂,反应温度320℃,n(O2)∶n(异丁烯)(氧烯比)=10∶1,体积空速(GHSV)=2000 h-1.在该条件下,Mo12Bi1.2Fe3Co8K0.4在100 h的催化异丁烯气相氧化反应中表现稳定,异丁烯转化率保持在98.6%,MAL选择性保持在86.4%.
Mo12Bi1.2Fe3Co8K0.4 for selective oxidation of isobutene to methacrolein
A series of MoBiFeCoK mixed-oxide catalysts were prepared by co-precipitation method using(NH4)6Mo7O24·4H2O,Bi(NO3)3·5H2O,Fe(NO3)3·9H2O,Co(NO3)2·6H2O,and KNO3 as precursor metal salts.The effects of contents of main metals Mo and Bi,co-metals Fe and Co,and doped K on the catalytic performance of the catalysts for gas-phase oxidation reaction of isobutene were investigated.The catalysts before and after doping with K were characterized by SEM,EDX,XRD,and NH3-TPD,while the catalytic conditions for the gas-phase oxidation reaction of isobutene were optimized and the catalytic stability of the catalysts for 100 h were evaluated.The results showed that the contents of Bi,Fe,Co,and K had a significant effect on the catalytic performance of MoBiFeCoK mixed-oxide catalysts for the gas-phase oxidation reaction of isobutene,with Mo12Bi1.2Fe3Co8K0.4 showing the best catalytic performance.The doping of K reduced the amount of catalyst acid center(from 15.27 μmol/g of Mo12Bi1.2Fe3Co8 to 5.91 μmol/g of Mo12Bi1.2Fe3Co8K0.4)and significantly enhanced the selectivity of the main product methacrolein(MAL).Under the optimal reaction conditions of 0.66 g Mo12Bi1.2Fe3Co8K0.4 as catalyst,reaction temperature 320℃,n(O2)∶n(isobutene)(oxygen-alkene ratio)=10∶1,and gaseous hourly space velocity(GHSV)=2000 h-1,the catalytic isobutene gas-phase oxidation reaction of Mo12Bi1.2Fe3Co8K0.4 was stable for 100 h,with the isobutene conversion of 98.6%,and the MAL selectivity of 86.4%.
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