非晶态Fe_(0.5)Al_(0.5)PO_4表面上激光促进甲烷直接氧化合成甲醇的研究

Laser Stimulated Methane Direct Partial Oxidation to Methanol on the Surface of Non-crystal Fe 0.5 Al 0.5 PO 4 *

用溶胶—凝胶法合成了非晶态Fe0 .5Al0 .5PO4 。用XRD和TPR表征了其结构和晶格氧的活性 ;用IR和TPD表征了CH4 在其表面上的吸附行为 ;用LSSR方法考察了CH4 直接氧化合成CH3 OH的反应规律。结果表明 ,Fe0 .5Al0 .5PO4 具有非晶态的结构 ,FePO4 和AlPO4 的微区被均匀地相互隔离 ,导致固体本身不具有长程有序性。非晶态的Fe0 .5Al0 .5PO4 与晶态的Fe0 .5Al0 .5PO4 相比 ,其晶格氧的活性大且活性氧的含量高。CH4 以分子态吸附于固体表面P =O键上 ,非晶态Fe0 .5Al0 .5PO4 表面上CH4 的吸附强度和吸附量都较晶态Fe0 .5Al0 .5PO4 上大。用 10 73cm- 1的激光激发固体表面P =O键 ,在 10 0℃以上CH4 的直接氧化反应顺利进行 ,CH3 OH保持高选择性。在相同的反应条件下 ,非晶态Fe0 .5Al0 .5PO4 能更有效地促进反应的进行 ,表明在激发相同表面化学键的情况下 ,固体表面材料的其它性质如粒度。

Crystal and non-crystal Fe 0.5 Al 0.5 PO 4 were prepared using dipping method and sol-gel method, respectively. The surface structure, lattice oxygen activity, chemisorption to methane and LSSR of the surface materials were investigated by XRD, IR, TPR and laser stimulated surface reaction techniques. The non-crystal Fe 0.5 Al 0.5 PO 4 has the structure of mixed small particles of FePO 4 and AlPO 4, which is different from the continued crystal Fe 0.5 Al 0.5 PO 4 structure. The activity of the lattice oxygen in non-crystal Fe 0.5 Al 0.5 PO 4 is more than that in the crystal Fe 0.5 Al 0.5 PO 4. Methane can be adsorbed on the surface P=O bond with the molecular adsorption state, and the adsorption amount of methane on the non-crystal Fe 0.5 Al 0.5 PO 4 is greater than that on the crystal Fe 0.5 Al 0.5 PO 4 . While the 1083cm -1 laser exciting the surface P=O bond, the reaction of methane partial oxid ation to methanol is occurred obviously at the temperature higher than 100℃with the methanol selectivity higher than 80%. The efficient utilization of laser energy characterized by the methane conversion on non-crystal Fe 0.5 Al 0.5 PO 4 is more than that on the crystal Fe 0.5 Al 0.5 PO 4, indicated that the amount of the laser energy transferring from the excited surface bond into the solid body can be decreased by the microminiaturization of the solid microcrystalline particles of the solid material.