钒钼复合氧化物表面上激光促进异丁烷选择氧化制甲基丙烯酸

Laser Stimulated Selective Oxidation of i-Butane to Methacrylic Acid over Mo 4V 6O 24

用共沉淀法制备了 V和 Mo的复合氧化物 .运用 XRD、IR、TPD和 LSSR技术研究了其晶体结构、表面构造、化学吸附特性和激光促进异丁烷选择氧化反应性能 .结果表明 :V— Mo—O的主体物相为Mo4V6 O2 4,它具有 Mo O3和 V2 O4交替排列的层状结构 ;其表面上存在着 Lewis碱位 Mo O 和 Mo—O—V键中的 O2 -及 Lewis酸位 V4+ ;异丁烷的 2个甲基 H分别吸附在 2个相邻的 Lewis碱位 Mo O 上形成双位分子吸附态 ;在常压和 2 0 0℃条件下 ,用一定频率的激光激发 Mo O 键 1 0 0 0次 ,异丁烷的转化率为 6.5% ,其反应产物是异丁烯、甲基丙烯醛和甲基丙烯酸 ,其中甲基丙烯酸的选择性为 78% .根据实验结果 ,探讨了激光促进异丁烷选择氧化为甲基丙烯酸的表面反应机理 .

A Mo/V complex oxide was prepared from (NH 4) 6Mo 7O 26 ·4H 2O and NH 4VO 3 by a coprecipitation method. The surface composition, structure, chemsorption and behavior of laser stimulated selective oxidation of isobutane have been investigated by XRD, IR, TPD and microreactor. The results showed that the main phase of the complex oxide is Mo 4V 6O 24 , which has a storeyed structure composed of MoO 3 and V 2O 4. There are both Lewis base sites, O 2- in the surface Mo O or Mo—O—V bonds, and Lewis acid site, V 4+ appeared on the surface of complex oxide. Two methyl hydrogens in isobutane molecule can be chemisorbed on the terminal oxygen of the neibouring Mo O bonds on the surface of the complex oxide. Under the conditions of 0 1 MPa, 200 ℃ and 1000 times of laser excitation with 972 cm -1 on the Mo Obonds, about 6 5% isobutane were converted to isobutene, methyl propenal and methacrylic aicd, among them 78% were the latter. A mechanism is proposed for isobutane selective oxidation.