论文部分内容阅读
用沉淀法制备了Li3PO4、BiPO4 和Li3PO4·BiPO4 三种固体表面材料,并用XRD、IR、TPD和激光促进表面反应(LSSR)等技术研究了这些固体表面上甲醇氧化偶联生成乙二醇的反应规律.实验结果表明:甲醇在固体材料表面的P=O键上产生C -H端的分子态吸附,在表面的Lewis酸位(金属离子)上产生解离态吸附.Li3PO4 和BiPO4 的相互作用可促进甲醇在固体表面上的分子态吸附而抑制解离态吸附.激光表面反应的机理为:用频率为1077cm-1的激光光子激发固体表面P=O键,可使其端氧活化,活化的氧与吸附态的甲醇分子作用使其脱氢,形成表面CH2OH负碳离子,进而在固体表面Lewis酸位上CH2OH负碳离子相互偶联生成乙二醇.反应温度的提高有助于补充激光能量密度的不足,同时促进产物的脱附,但温度升高会诱发热反应而生成副产物.在常压和120℃的反应条件下,用1077cm-1激光激发Li3PO4·BiPO4 表面1000次,甲醇的转化率达16 %,乙二醇的选择性达97.7 %.
Three solid surface materials Li3PO4, BiPO4 and Li3PO4 · BiPO4 were prepared by precipitation method. The reactions of methanol oxidation coupling to ethylene glycol on these solid surfaces were studied by XRD, IR, TPD and laser induced surface reaction (LSSR) The experimental results show that the methanol adsorbed on the P = O bond on the surface of the solid material produces the C-H-terminal molecular adsorption and the dissociative adsorption on the surface Lewis acid sites (metal ions). The interaction between Li3PO4 and BiPO4 Promoting the molecular adsorption of methanol on the solid surface and inhibiting the dissociative adsorption.The mechanism of the laser surface reaction is as follows: activating the activated oxygen at the surface of the solid by using the laser photon with the frequency of 1077cm-1 to activate Oxygen and the adsorption of methanol molecules to dehydrogenation, the formation of surface CH2OH carbanion, and then in the solid surface Lewis acid CH2OH carbanion coupled to generate ethylene glycol.Reaction temperature helps to supplement the laser energy Density, but also promote the desorption of products, but the temperature rise will induce thermal reaction and generate by-products.Under atmospheric pressure and reaction conditions of 120 ℃, 1077cm-1 laser excitation Li3PO4 · BiPO4 surface 1000 times, methanol Conversion rate of 16%, ethylene glycol selectivity of 97.7%.