激光促进H_3PW_(12)O_(40)表面甲烷部分氧化反应

Behavior of Laser Stimulated Methane Partial Oxidation on Surface of H_3PW_(12)O_(40)

以H3 PW12 O4 0 (PW12 )作为固体表面材料 ,用IR ,TPD和激光促进表面反应 (LSSR)技术等手段考察了PW12的表面构造、化学吸附性能和激光促进CH4 部分氧化合成CH3 OH的反应规律 .PW12 表面上存在着Lewis碱位 (W=O和W O W键中的氧位 )和Lewis酸位 ( W6+ ) .CH4 在PW12 表面的Lewis碱位上发生化学吸附 ,主要吸附位是W =O键 .采用 980cm-1的激光激发PW12 表面的W =O键 ,在 10 0℃以上和常压下 ,CH4 的部分氧化反应顺利进行 .CH3 OH是CH4 氧化的直接产物 ,HCHO ,CH3 OCH3 和烃类是CH3 OH进一步反应的产物 .H2 O分子在反应中的作用可能为 :通过激光参与下H2 O分子与PW12 表面发生相互作用 ,能产生有利于CH4 吸附和CH3 OH生成的表面活性位W6+ O-,同时产生有利于气相分子氧补充反应消耗晶格氧的表面氧缺位 ,从而提高光能的有效利用并加速CH4 直接氧化反应的进行 .根据实验结果 。

Solid surface materials PW 12 and PW 12 ·6H 2O were prepared. The surface structure of the materials, and chemisorption and laser stimulated surface reaction (LSSR) of methane on the surface of the materials were investigated by IR and TPD MS techniques. There exist Lewis base sites W=O and W O W as well as Lewis acid site W 6+ on the solid surface materials. Methane can be adsorbed on the surface W=O and W O W bonds with the molecular adsorption state, and the adsorption amount on W=O bond is greater when θ ≥100 ℃. With 980 cm -1 laser to excite the surface W=O bond, the partial oxidation of methane occurred obviously at normal pressure and temperature higher than 100 ℃. Methanol is the direct product of methane oxidation, while HCHO, CH 3OCH 3 and hydrocarbons are the products of methanol reacted continuously on the solid surface. With the excitation of laser energy, H 2O molecules can react with the solid surface to form W O - active site and lattice vacancy on the solid surface, which can enhance the adsorption of methane and the formation of methanol. According to the characterization and reaction results,a mechanism for LSSR of CH 4 is given.