甲苯液相氧化反应过程的动力学研究

在直径Φ48mm 的鼓泡床反应器中对以醋酸钴(CO~(2+))水溶液为催化剂的甲苯液相空气氧化反应动力学进行了研究。结果表明,反应体系的活性时间随催化剂的用量的增大而线性增大,当 Co 含量大于2×10~(-2)%(mass)时,对反应影响较小。甲苯液相空气氧化反应的甲苯消耗动力学分别与甲苯浓度和氧溶解在甲苯中的浓度成一级反应.其宏观动力学活化能约为41 kJ/mol。氧在液相主体消耗的本征动力学活化能为57 kJ/mol,指前因子53.34m~3/(mol·s)。通过 Ha 数和效率因子η对反应动力学控制步骤进行分析,结果表明,Ha 小于0.1,η为0.606～0.728。反应主要发生在液相主体,受动力学控制,但传质仍对反应有影响。     

甲苯液相氧化动力学研究

建立了一套甲苯液相空气氧化的连续反应装置,在工业条件下进行了动力学实验研究。在排除氧气、催化剂质量分数等影响因素下,建立了反应动力学模型,并回归得到模型参数。用该模型计算得到的甲苯转化率和实验结果对比,最大误差4.72%,平均误差2.36%。研究结果表明,甲苯转化率受温度和停留时间的影响较大,尤以温度影响更为明显;主产物选择性受温度和停留时间的影响较小,但停留时间延长,会加剧苯甲醛向苯甲酸转化。     

环己烷富氧氧化制环己酮的研究

研究了环己烷富氧氧化的特征,考察了进气氧浓度的提高对反应速度、选择性、安全性和经济性的影响。通过工业化试验,控制氧气体积分数30%,反应温度160～175℃,压力1.0～1.2MPa,环己烷氧化转化率为3%～4%,能很好实现富氧氧化反应,氧化尾气的氧气体积分数可以安全控制在2%～3%。环己烷富氧氧化可用于环己酮装置的改扩建,较空气氧化经济性好。     

甲苯液相选择性氧化制苯甲醛的工艺研究

甲苯与空气液相选择性氧化是一条制备苯甲醛的绿色化生产路线。建立了一套甲苯液相空气氧化的连续化试验装置,在工业装置操作条件下,通过加入含氮杂环化合物助催化剂,提高了甲苯转化率和苯甲醛选择性。研究结果表明,加入苯并咪唑助催化剂100 mg·kg~(-1)后,甲苯转化率为17.3%,苯甲醛选择性为6.6%。     

甲苯液相空气催化氧化技术研究进展

介绍了甲苯液相催化氧化的反应机理、反应动力学模型和催化剂的研究进展;叙述了近年来在催化剂的研制、利用纯氧或富氧工艺、强化反应等方面的新技术.认为现有的生产技术有待于进一步改进,使用新型或复合催化剂、开发富氧或纯氧氧化工艺是降低成本、提高产品质量和生产能力的发展方向,并可借鉴其它液相氧化研究中出现新技术.     

异长叶烯酮的绿色合成

以富氧空气为氧化剂,催化氧化异长叶烯合成香料异长叶烯酮,系统考察了富氧空气中氧的体积分数、气体通量及反应温度等因素对反应转化率和收率的影响,确定了反应最佳条件:富氧空气中φ(O2)=33.1%,反应温度60℃,气体通量60 mL/m in,反应12 h,转化率达87.5%,收率达78.0%。反应条件温和,过程无有机溶剂参与,分离纯化简单,环境友好,适于工业化生产。     

异长叶烯酮合成条件优化及动力学

以异长叶烯为原料合成香料异长叶烯酮, 选取富氧空气中氧体积分数、气体通量、反应时间、反应温度4个因素, 采用L9(34)正交试验设计优化反应条件。利用Minitab软件分析确定适于工业化生产的最优反应条件为:富氧空气中氧体积分数35%, 气体通量60mL/min, 反应时间8h, 反应温度60℃;反应转化率达61.79%;目标产物收率达55.49%。此外, 考察了反应体系含水量对该反应的影响, 结果显示含水量对反应转化率及产物生成率有较大影响。本实验研究了该氧化反应的动力学过程, 确定该反应为一级不可逆吸热反应, 其反应活化能为64.92kJ/mol, 为该反应过程的工业化生产奠定基础。     

原油注空气氧化反应及其动力学研究进展

注空气采油技术作为一种经济有效的提高原油采收率的方法,受到国内外的广泛关注。原油注空气氧化反应及其动力学研究,一方面可作为该技术在油田应用上的可行性评价,另一方面也是加快耗氧速率和保证生产全过程安全性的关键。本文综述了国内外原油注空气氧化反应模型和动力学的研究进展,指出了各类氧化反应模型的优缺点,认为等转化率法今后将成为原油氧化动力学研究的得力工具,提出了今后应该重点研究建立适合具体油藏的氧化反应模型,以及总压力或者氧分压对原油氧化反应速率的影响,以确定氧气的反应级数。     

邻氯甲苯选择性硝化合成2-氯-5-硝基甲苯

邻氯甲苯硝化合成CLT酸因其转化率低及选择性差而未能实现工业生产。本文对邻氯甲苯硝化反应进行了研究,采用不同的催化剂体系,获得了成本低且选择性好的的合成条件。用酸性皂土和异丁醇为催化剂的硝化方法,转化率可达100%,2-氯-5-硝基甲苯比率提高到70.1%。     

金属卟啉催化空气氧化甲苯制取苯甲醛及苯甲醇的新工艺

在少量简单金属钴卟啉的催化下,无需外加溶剂及反应引发剂,甲苯可由空气直接选择性液相催化成为苯甲醛及苯甲醇。反应结果表明反应时间、反应温度、压力、催化剂用量及空气流量等工艺参数的变化对反应都有影响。在165℃、0．8MPa、3．4ppm及40L／h空气流量的最佳反应条件下,甲苯的转化率可以达到8．7％,同时醛醇选择性可以达到近60％。同传统空气氧化甲苯制取苯甲醛体系相比,此催化体系工艺条件简单、清洁无污染,产品质量好。研究结果表明,金属卟啉存在下的催化空气氧化甲苯制取苯甲醛及苯甲醇的反应经历了一个由金属卟啉引发的自由基反应历程。     

进气氧浓度对PX氧化反应器的影响

以对二甲苯（PX）液相催化氧化反应器的连续鼓泡釜模型，对尾氧浓度保持3．5％时不同进气氧浓度下的反应器进行了模拟。模拟计算发现反应温度随着进气氧浓度的增加而升高，可以通过减少塔顶抽出水量或降低反应压力维持反应釜温度不变。较高的氧浓度进气对反应器操作的影响主要表现在温度效应和浓度效应上，温度效应使得主反应的速率增加，浓度效应却降低主反应的速率。随着进气氧浓度的增加，温度效应和浓度效应共同作用的结果是氧化反应器的生产能力先增大后减小，因此存在一个适宜的进气氧浓度，由计算得到为26.6％。     

Effects of Oxygen Transfer Limitation and Kinetic Control on Biomimetic Catalytic Oxidation of Toluene

Under oxygen transfer limitation and kinetic control, liquid-phase catalytic oxidation of toluene over metalloporphyrin was studied. An improved technique of measuring dissolved oxygen levels for gas-liquid reaction at the elevated temperature and pressure was used to take the sequential data in the oxidation of toluene catalyzed by metalloporphyrin. By this technique the corresponding control step of toluene oxidation could be obtained by varying reaction conditions. When the partial pressure of oxygen in the feed is lower than or equal to 0.070 MPa at 463 K, the oxidation of toluene would be controlled by oxygen transfer, otherwise the reaction would be controlled by kinetics. The effects of both oxygen transfer and kinetic control on the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol in biomimetic catalytic oxidation of toluene were systematically investigated. Three conclusions have been made from the experimental results. Firstly, under the oxygen transfer limitation the toluene conversion is lower than that under kinetic control at the same oxidation conditions. Secondly, under the oxygen transfer limitation the total selectivity of benzaldehyde and benzyl alcohol is lower than that under kinetic control with the same conversion of toluene. Finally, under the kinetics control the oxidation rate of toluene is zero-order with respect to oxygen. The experimental results are identical with the biomimetic catalytic mechanism of toluene oxidation over metalloporphyrins.     

Modeling of the Residence Time Distribution and Application of the Continuous Two Impinging Streams Reactor in Liquid‐Liquid Reactions

The two‐phase monosulfonation of toluene, as an example of liquid‐liquid reactions, has been conducted in a continuous two impinging stream reactor (TISR). The extent of reaction under different operating conditions has been determined. A comparison has been made between the performance capability of the TISR and that of continuous stirred tank reactors (CSTR). Under identical conditions, including mean residence time, temperature, feed compositions and phase ratio, the impinging stream reactor has shown a higher efficiency. Finally, a stochastic model, based on Markov chain processes has been developed for the TISR, which describes the flow pattern and the residence time distribution (RTD) within the reaction system. The RTD model, combined with the kinetic expression, has been applied to calculate the conversion of toluene in the reactor. The predicted values for toluene conversion have been compared with those determined experimentally.     

Mathematical modeling and simulation for gas–liquid reactors

Gas–liquid reactors are widely used in many industrial processes such as oxidation, hydroformylation, chlorination, etc. The paper develops comprehensive model for reactors using the mixing cell approach. It incorporates heat and mass transfer effects in the film and uses a boundary element method to solve the film model equations. The fluxes obtained at the interface are then directly used as the link to the reactor model. Simple isothermal and non-isothermal reactions were numerically tested. Application to two industrially important case studies, chlorination of butanoic acid and oxidation of cyclohexane are briefly illustrated. For the autocatalytic chlorination of butanoic acid, the yield of desired product, monochlorobutanoic acid, is favored by the high degree of mixing in the liquid phase. Therefore, this reaction should be carried out in a CSTR. A series of five bubble tanks with parallel gas reactant feed for cyclohexane oxidation was also simulated. It was found that the cyclohexane conversion is low while the oxygen conversion is relatively high and almost constant in each tank. Due to the complex multistep nature of this reaction scheme, oxygen is consumed in many steps of oxidation and selectivity of main products (which are intermediate products in the reaction scheme) depends on the critical control of over-oxidation in the kinetic mechanism.     

Kinetic Modeling of Liquid Phase Oxidation of Cyclohexane

A kinetic model for the liquid phase oxidation (LPO) of cyclohexane has been derived using a reaction network based on a consistent free radical mechanism. It was demonstrated that on embedding this rate model within the overall model of a semi‐batch gas‐liquid reactor (SBR) one can predict the time variation of the dissolved oxygen concentration and the rate of oxygen absorption which compare fairly closely with some well regarded published experimental data. The model is distinguished by easy extendibility and modularity whereby it could be tailored to predict, in the context of a SBR, cyclohexane conversion and ketone‐alcohol (K‐A) product selectivity levels as observed in commercial plants and in the published data on pilot plant experimentation. The model is expected to be of use in the design and scale‐up of LPO reactors.     

甲苯液相空气氧化过程中[Co2+]/[Co3+]的测定及其对反应的影响

Liquid phase oxidation of toluene is an environmental benign route for the production of benzoic acid. In a mm bubble column reactor, the commercial process of toluene liquid phase oxidation was conducted with Co(CH3COO)2&#8226;4H2O as catalyst. The Co2+ concentration [Co2+] was determined by extraction spectrophotometry and hereby the Co3+ concentration [Co3+] was obtained by mass balance. The results showed that [Co3+] reached the maximum at about 25-30 min. [Co3+] increased with increasing Co catalyst amount at total Co concentration <150 mg&#8226;L－1 of toluene. The conversion of toluene, yield and selectivity of benzoic acid increased with the increasing [Co3+/Co2+]max. A high [Co3+] and a high [Co3+]/[Co2+] ratio are beneficial to the reaction.     

列管固定床反应器内CO氧化偶联制草酸二甲酯反应模拟及优化

针对列管式固定床反应器中的单根反应管,采用在接近工业条件下获得的CO氧化偶联制草酸二甲酯动力学方程,建立了一维、二维拟均相模型,并与单管实验结果进行了对比,结果表明一维拟均相反应器模型更能准确描述单管反应器内的CO偶联反应。进一步利用一维拟均相模型模拟计算了操作参数对床层热点温度、反应转化率、产物选择性及床层压降的影响,分析了反应器热点温度对操作参数的敏感性。计算结果表明：冷却介质温度对反应管热点温度、亚硝酸甲酯转化率有较大影响,是需要严格控制的工艺指标;较低的空速容易引起反应器飞温;反应器进口压力、原料气进料温度和反应物组成在计算范围内对反应器热点温度影响相对较小。为了提高偶联反应器的负荷和强化床层内的传热效果,可以将进料空速提高至4000 h^-1,同时,可以通过将反应器进口压力增大至500 kPa来降低压缩机能耗。研究结果可为现有列管式CO氧化偶联反应器的改进和工艺优化提供参考。     

Comparison of a contactor catalytic membrane reactor with a conventional reactor: example of wet air oxidation

A wet air oxidation reaction was carried out in a gas/liquid catalytic membrane reactor of the contactor type. The oxidation of formic acid was used as a model reaction. The mesoporous top-layer of a ceramic tubular membrane was used as catalyst (Pt) support, and was placed at the interface of the gas (air) and liquid (HCOOH solution) phases.

A similar reaction was carried out in a conventional batch reactor, using a steering rate high enough to avoid gas-diffusion limitations, and exactly identical conditions than for the CMR (amount of catalyst, pressure, etc.). At room temperature, the CMR showed an initial activity three to six times higher than the conventional reactor. This activity increase was attributed to an easier oxygen access to the catalytic sites. Nevertheless, the catalytic membrane gradually deactivated after a few hours of operation. Different deactivation mechanisms are presented.     

Kinetics of cupric oxide catalysed oxidation of propylene in a stirred reactor

The catalytic air oxidation of propylene to acrolein over a supported copper oxide catalyst was investigated in a continuous stirred vessel reactor between 375° and 450°C at atmospheric pressure. The effect of temperature, ratio of oxygen to propylene in feed and total feed rate (or contact time) on the conversion of propylene and the yield of acrolein were determined. It was found that with an increase in temperature, ratio of oxygen to propylene and contact time, the yield drops considerably though conversion increases. A study of the mixing characteristics of the stirred vessel reactor was carried out by following the conversion at various stirrer speeds. The kinetic data obtained were tested to determine the most probable model by the Hougen-Watson method. The model that satisfactorily correlated the data describes the rate-controlling step as the surface reaction occurring between adsorbed propylene, a vacant site and oxygen in the gas phase. The following Hougen-Watson type rate equation has been proposed The constants in the rate equation have been expressed as a function of temperature.     

Effect of gas feed flow and gas composition modulation on activated carbon performance in phenol wet air oxidation

Modulation of gas feed composition (air/N₂ cycling) and gas feed flow (on-off air cycling) was investigated in the catalytic wet air oxidation of phenol over activated carbon (AC). Fifty hours lasting experiments were conducted in a laboratory trickle bed reactor at 140-160 °C, 2 bar of oxygen partial pressure and different splits and periods to determine the set of cycling parameters that optimise the periodic reactor operation. To follow the dynamic behaviour of the phenol oxidation, temperature and conversion were continuously monitored by means of computerised data acquisition and automatic liquid sampling. Several long term tests over 144 h were also run using both periodic operating strategies to compare the activity and stability of AC with those obtained in a steady state operation at otherwise same conditions. The results show that, depending on the selection of split and period, modulation of the gas phase significantly improves the stability of AC compared to steady state operation, thereby performing a superior long term phenol conversion.