【作者】 陈飞；

【导师】 陈丰秋； 詹晓力；

【作者基本信息】 浙江大学 ， 工业催化， 2006， 硕士

【摘要】 烃类的选择（氨）氧化是重要的工业反应,在这类反应中,目的产物往往是（氨）氧化中间产物,过多的副反应将不利于产物在后序处理中的分离和精制,特别是热力学上最有利的深度氧化反应,既加重了环境的污染,又浪费了原料,因此研究此反应体系具有重要的工业意义和经济效益。原位漫反射红外是近年来发展起来的研究催化剂表面反应作用机理的实验技术,本论文利用此实验技术对丙烯氧化和丙烯氨氧化这一复杂体系的反应规律进行了研究。 首先在确定自建的原位漫反射红外实验装置的分辨率、扫描次数、催化剂粒径和气速等参数的较佳操作值的基础上,动态考察了丙烯氧化的催化剂表面反应和气相反应行为。结果表明:催化剂表面的选择氧化能够有效抑制深度产物CO₂、CO的生成量,选择氧化的活性中心是催化剂表面的晶格氧。催化剂表面的丙烯氧化反应有多种反应路径,实验中检测到的中间产物主要有:（ⅰ）π-allylic络合物;（ⅱ）丙烯与催化剂表面的Br（?）nsted酸位作用形成的烯丙醇物种;（ⅲ）异丙醇中间物种。 在丙烯氨氧化反应中,氨的吸附主要有三种形式:（1）氢键结构:NH…O^2-,氨与表面的氧负离子或者表面羟基基团形成氢键;（2）N原子与表面羟基形成的氢键;（3）与催化剂表面的阳离子（即表面Lewis位）形成共价结构。另外,也会发生完全的质子转移而形成NH₄⁺或者氨吸附分解生成表面NH₂基团和表面羟基基团。当其他物种与氨共吸附时,会改变化学吸附的氨物种的性质。内烯氨氧化反应的原位漫发射研究的最佳反应温度是400℃,在此温度下最有利于中间产物的检测。研究发现,反应开始阶段即有丙烯醛生成,而丙烯腈随反应温度的升高,出现的时间变早,说明丙烯腈的生成需一定的时间。更多还原

【Abstract】 Selective Oxidation of hydrocarbon is one of the most important reaction in industry. The target product usually is oxidation intermediates in this kind of reaction, and excess side reactions make it difficult to purify and separate the product. Especially, deep oxidation will bring environment pollution and waste raw materials. So there is lots of industrial significance and economy profit in the research of this system. In recent years, more and more investigation focus on the in-situ DRIFT technique to study surface reaction mechanism, and here this technique is applied to probe the mechanism of propylene ammoxidation.At first, some parameters such as the resolution, scanning time, catalyst particle size and gas velocity are fixed at best values, and then it is systemically investigated for the propylene selective oxidation over multi-component bismuth molybdate catalyst, including surface reaction and gas reaction behavior. The selective oxidation of propylene over catalyst surface effectively controls deep oxidation products of propylene such as carbon dioxide and carbon monoxide. The centers of active sites of selective oxidation are surface lattice oxygens. The nature of adsorbed intermediates detected by IR are:（ i ）a π-allylic intermediate;（ii ）an enolic type compound formed in the presence of Bronsted acid sites;（iii）a π-boned propylene species interacting with Lewis acid sites.During propylene ammoxidation, the ammonia molecules can be bound to the oxide surface by either（ i ）a hydrogen-bond, NH …… O^2-, formed by ammonia atom with a surface oxygen anion or with the oxygen of a surface hydroxyl group;（ii ）a hydrogen-bond between the nitrogen atom and a surface hydroxyl atom;（iii）a coordination bond, formed by ammonia atom with a surface cation （Lewis acid site）. Moreover, the complete proton transfer can occur to produce an NH₄⁺ ion, or alternatively ammonia adsorption-decomposition can also take place to form the surface NH₂ and OH groups. The coadsorption of other molecules willchange the nature of ammonia chemisorbed species .The optimum temperature for propylene ammoxidation will be 400 °C that favors the detection of the intermediates. The results show that acrolein appears at the beginning of the reaction, but acrylonitrile appears earlier when the temperature is higher which indicates that the formation of acrylonitrile takes some time.更多还原