激光促进Pb和Bi磷酸盐表面上异丁烷氧化脱氢反应

Laser Stimulated Oxidative Dehydrogenation of Isobutane to Isobutene on the Surface of Pb and Bi Phosphate

采用沉淀法制备了Pb3（PO4）2 和BiPO4 固体材料，用XRD，IR，TPD和LSSR等手段对Pb3（PO4）2和BiPO4的晶体结构、表面构造、化学吸附性能和激光促进异丁烷氧化脱氢反应性能进行了研究．结果表明，固体材料表面由Lewis碱位P=O和P-O-M（Pb或Bi）键中的O2-及Lewis酸位Pb2+或Bi3+构成；异丁烷分子中两个甲基中的H分别吸附在两个相邻的Lewis碱位P=O上，形成双位分子吸附态；在常压和200℃条件下，用一定频率的激光激发固体表面P=O键，发生异丁烷氧化脱氢反应，产物异丁烯的选择性大于95％，在激光促进表面反应体系中，激光能量的利用率主要取决于固体材料的振动结构和对反应物分子的吸附能力，反应产物的选择性主要决定于反应物分子在固体表面上的吸附态．

Abstract Pb3(PO4)2 and BiPO4 were prepared by the precipitation method. The surface composition, structure, chemisorption properties and the behavior of laser stimulated isobutane selective oxidation were investigated by means of the techniques of XRD, IR, TPD and LSSR. The results showed that both Lewis base sites, O2- on the surface P =O or Pb(Bi)桹 bonds, and Lewis acid site, Pb2+ or Bi3+ appear on the surface of Pb3(PO4)2 or BiPO4. Two methyl hydrogens in isobutane molecule can be chemisorbed at the terminal oxygen of neighboring Lewis base sites P = O bonds on the surface of phosphate. Under the conditions of 0. 1 MPa and 200 with the 1 056 cm-1 laser photons exciting the P =O bonds for 1 000 times, the oxidative dehydrogenation reaction of isobutane occurred remarkably with the product selectivity of isobutene over 95%. In the course of LSSR, the conversion of isobutane depends on the vibrational structure of the solid materials and the adsorbing amount of isobutane on the excited P = O bonds, the selectivity of the reaction product depends on the adsorbing state of isobutane on the solid surface.