【作者】 王亚辉；

【导师】 陈晓春；

【作者基本信息】 北京化工大学 ， 化学工程， 2007， 硕士

【摘要】 丙烯氨氧化催化剂MB-98用于生产丙烯腈，由于催化剂在贫氧区导致的晶格氧的失去，引起催化剂活性降低，为了恢复催化剂活性延长催化剂使用周期，必须多次再生。因此，开展催化剂再生动力学研究，对提高催化剂再生效果，延长使用周期，具有重要意义。首先设计了一套实验装置使催化剂的还原和氧化再生过程分开进行。在微型固定床反应器中通入氢气与MB-98催化剂反应，通过控制反应时间，能够制得部分失活的还原态催化剂。将此催化剂和热空气接触，在反应天平上发生氧化再生反应，测量其质量的变化，可以得到催化剂再生过程的TG曲线。以此来考察其补氧过程的瞬变行为，并进一步研究得到了反映反应动力学特性的再生机理模型。通过分析不同还原程度的催化剂的TG-DTG的基本特征，解析了TG曲线中两个增重区间的不同意义。研究表明，氧化过程存在两种化合反应。反应之一是Fe²⁺被氧化，反应之二是钼的低价氧化物被氧化。并由此确定在还原程度不大的工业条件下，催化剂补氧再生时发生的主要反应是Fe²⁺被氧化的过程。通过考查不同升温速率的影响，得到了补氧量和氧化温度随升温速率变化的规律，解释了补氧速率变化的原因。模拟工业条件制取部分失活的催化剂样品，用近似外推法求得升温速率无穷小时补氧的起始氧化温度和终止氧化温度，并得到了最佳的补氧升温速率10K．min^-1。采用几种不同的热分析方法处理实验数据，最终得到MB-98催化剂氧化再生时的反应机理，即相边界控制的收缩核模型。其活化能E=110kJ．mol^-1，指前因子A=1.79*10⁷min-1，并由此得到了动力学方程为dot/dt=Aexp（-E/RT）*3（1-α）^2/3。更多还原

【Abstract】 Abstract: Ammoxidation catalyst MB-98 is used to produce Acrylonitrile. The activity would decrease when the catalyst is in the low oxygen zone because of the loss of lattice oxygen. The partial reduced catalyst needs to be regenerated continually in order to keep its activity. Therefore, to investigate the re-oxidation kinetics is significative for the improvement of the regeneration efficiency.firstly, An experimental set-up was built for splitting up of the overall reaction to two steps, selective reduction and re-oxidation of deoxidized catalyst . Partial reduced catalyst can be prepared in a fixed bed reactor. The as-prepared catalyst was then put into a thermo-analyzer with an air flow. The thermal re-oxidation behavior of the catalyst can be studied by measuring the mass variety under different heating rates. The reaction kinetics was investigated according to the thermal analysis data and a most suitable reaction mechanism model was obtained.The experimental results showed that there are two stages in the oxidation process. The first stage is about the Fe being oxidized and the second one is relative to the oxidation of some molybdenum oxides in a lower valent. According to the industrial conditions we know that the first stage is the main process which should be paid more attention to.The reaction rate increases as the heating rate increases and the total oxidation mass increase of the catalyst turn to be the highest value when the heating rate is 10 K.min. The reaction temperature with no heating rate influence is obtained using approximate extrapolate method.Several methods for estimating the kinetic parameters and identifying the mechanism of the reaction were used to treat the non-isothermal kinetic data. The results obtained suggest that the re-oxidation process of the catalyst obeys the contracted core model controlled by the Phase border. The reaction rate equation can be expressed as dα/dt =Aexp(-E/RT)*3(1-α), where the activation energy E=110 kJ/mol, the frequency factor A=1．79*10min更多还原