Catalytic oxidation of benzene to maleic anhydride in a continuous stirred tank reactor

The kinetics of the vapor phase oxidation of benzene has been studied over an industrial catalyst in a continuous stirred tank reactor in the temperature range from 280 to 430°C and at atmospheric pressure. The products obtained are maleic anhydride, carbon oxides and water. The rate of the overall reaction (disappearance of benzene) is represented by the following expression based upon a steady state adsorption model The rate of formation of maleic anhydride is correlated by the equation which allows for a homogeneous depletion of maleic anhydride. The rate constants k_B, k_O, k_2(g) were found to follow Arrhenius behavior.      

Analysis of a fluidized bed membrane reactor for butane partial oxidation to maleic anhydride: 2D modelling

The partial oxidation of butane to maleic anhydride in a membrane reactor with improved heat transfer through the wall has been studied in this work. The reactor consisted of a catalytic fixed bed with sintered metal membrane wall that allows the gradual feed of air from the external fluidized bed. The influence of the most important design and operation variables (reactor length, gas flow rate, inlet temperature, butane inlet concentration, and air gas flow rate) on butane conversion and maleic anhydride selectivity has been studied by means of computer simulations using an experimentally-validated detailed 2D model. The performance of this reactor was systematically compared to the corresponding conventional fixed bed reactor. The membrane reactor has been found to provide slightly higher selectivity than the fixed bed reactor. Moreover, in the membrane reactor, the mixing of butane and air takes place through the wall directly inside the catalytic bed. Since solid beds avoid flame propagation, the process can be operated with higher butane inlet concentrations under safety conditions. Hence, the fluidized bed membrane reactor represents an interesting alternative for industrial-scale operation.     

Redox kinetics of benzene oxidation to maleic anhydride

Steady state kinetics of the oxidation reaction have been determined with the help of a gradientless semi-differential, fixed-bed reactor. The Mars and van Krevelen phenomenological model satisfactorily correlates the experimental data but a modification of the Langmuir-Hinshelwood model taking into account partial coverage of the catalyst surface with reaction intermediates is preferred. Transient kinetics have been studied with a new automated periodic-pulse reactor, directly connected to a gas chromatograph. The response of a catalyst (essentially V₂O₅–MoO₃) to reduction and oxidation has been investigated. The rate of bulk (lattice) oxygen utilization as well as the degree of carbon coverage are estimated by this technique. Selectivity is dependent on the oxidation state of the catalyst: high partial pressure of either benzene or oxyen and high temperatures are detrimental to selectivity.     

Selective oxidation of n-butane to maleic anhydride in fluid bed reactors: detailed kinetic investigation and reactor modelling

The kinetics of n-butane oxidation to maleic anhydride over a commercial V-P-O catalyst for fluid bed reactors was investigated systematically and modelled according to a scheme of eight reactions, involving also the combustion of both n-butane and maleic anhydride to CO and CO₂, as well as the formation and the combustion of acetic and acrylic acids. A one-dimensional, heterogeneous (two-phase) fluid bed reactor model incorporating the independently derived kinetic scheme was successfully validated on a predictive basis against conversion, selectivity and steam production data collected in a full-scale MA production plant.     

糠醛催化氧化制顺酐及宏观动力学的研究

采用浸渍法制备负载型钼钨磷(MoWP)催化剂,空气为氧化剂,将可再生资源糠醛催化氧化制备顺丁烯二酸酐。以固定床微反应器评价催化剂的性能,研究了催化剂焙烧温度、接触时间、反应温度及糠醛摩尔比对反应的影响,并对糠醛气相氧化制顺酐的反应动力学特性进行了实验研究。结果表明,在催化剂焙烧温度为500℃、空速1 900 h-1、接触时间1.8 s、反应温度370℃、氧气与糠醛蒸气摩尔比为20∶1时,顺丁烯二酸酐收率最高达61.3%。按三角形反应网络建立的动力学模型与得出的动力学方程及参数同实验数据基本吻合。     

Catalytic polymerization of maleic anhydride

This study examined the polymerizations of maleic anhydride in solution and in the bulk phase catalyzed by nanocrystalline titania or sodium acetate. Through IR and ¹H‐NMR, the monomer and polymer were characterized, and the structure of the polymer was confirmed. Moreover, the polymer molecular weight was measured to be 400–800 in solution and 2000–3000 in the bulk phase. The mechanism of the catalytic polymerization was also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2868–2874, 2003     

糠醛气相法催化氧化制顺丁烯二酸酐

利用浸渍法制备负载型V2O5-MoO3-P2O5 /γ-Al2O3催化剂。采用ICP、N2吸附-脱附等温线及XRD表征催化剂的物化性质、结构特征,通过TPR考察催化剂晶格氧的供氧能力。在固定床连续微反应装置上,以来源于可再生生物资源的糠醛为原料,进行催化剂的性能评价。实验结果表明：当催化剂中MoO3和V2O5质量比为0.4、反应混合气体（糠醛体积分数2%的空气混合气体）空速为3000 h-1、反应温度为305 ℃的工艺条件下,测得糠醛转化率为82%,顺酐的收率为50%,说明适当地引入MoO3能够调节催化剂活性中心与载体间的强相互作用,达到促进催化剂晶格氧快速交换的目的,从而进一步提高催化剂的活性和选择性。     

A mathematical model for a biological fluidized bed reactor

A physical model is given in the present report for representing a three-phase biological fluidized bed reaction system which consists of microorganism-coated particles, waste water and air. The system is assumed to be well fluidized. The physical model can be represented by two differential equations describing, respectively, the substrate axial dispersion and diffusion/reaction. Numerical values of the physical parameters are selected from the literature or estimated from semi-empirical equations. The governing system equations are solved by an iterative finite-difference scheme. The theoretical predictions are compared with several experimental measurements and the agreement between them found to be very good, validating the physical model reported here.     

Catalytic oxidation of butane to maleic anhydride enhanced yields in the presence of CO2 in the reactor feed

The addition of CO₂ to the reaction mixture for the oxidation of butane over a VPO catalyst gives rise to significantly improved yields of maleic anhydride.     

Catalytic oxidation of hydrogen chloride in a fluid bed reactor

The Deacon reaction (HCI + 1/4 O₂ ⇋ 1/2 Cl₂ + 1/2 H₂O) was studied in a catalytic fluid bed reactor. Reaction rates found from measurements in differential and integral reactors were represented by the Langmuir-Hinshelwood type rate equation. Considering the effect of catalysts in the dilute phase, it was found that conversions in a fluid bed reactor can be calculated without any modifying parameters. It is pointed out that the wake fraction, which has been necessary to consider for fast reactions in a fluid bed reactor, is attributed to the dilute phase effect.     

Partial oxidation of methane to carbon monoxide and hydrogen in a fluidized bed reactor

A fluidized bed reactor has been used to investigate the partial oxidation of methane to syngas over a NiO/NiAl₂O₄ catalyst. The axial concentration profiles of the different species along the bed have been determined and related to the observed temperature profiles. The amount of carbon deposited on the catalyst under different operating conditions has also been determined. The results show that under suitable conditions, the bubbling fluidization regime gives a stable reactor performance with high conversion and selectivity, and a limited amount of carbon formation.     

助剂Co对苯氧化制顺酐VMoO系催化剂性能的影响

通过采用高温喷涂专利技术制备了一系列含助剂的V-Mo系苯氧化制顺酐催化剂,考察了助剂Co对催化剂性能的影响。并在选择氧化评价装置上进行了顺酐性能评价(盐温350~360℃,空速1 500~2 500 h/r,进料量0~50 g/m3)。结果表明,加入助剂Co对催化剂活性和选择性都有所改善,n(Co)∶n(V)为0.01时最佳。BET、SEM和XRD等分析表明,加入助剂Co,催化剂的微观结构发生了明显的改变,形成了更具活性的晶相,促进催化剂性能的提高。     

苯氧化生产顺酐尾气治理方案评价

介绍了采用催化燃烧法治理苯氧化生产顺酐尾气的燃烧试验及工艺方案,并进行了节能及经济评价.结果表明:催化燃烧法具有高效、节能环保、工艺简单、经济效益明显等优点,对处理顺酐生产废气具有较大优势.     

Catalytic pyrolysis of woody biomass in a fluidized bed reactor: Influence of the zeolite structure

Catalytic pyrolysis of biomass from pine wood was carried out in a fluidized bed reactor at 450 °C. Different structures of acidic zeolite catalysts were used as bed material in the reactor. Proton forms of Beta, Y, ZSM-5, and Mordenite were tested as catalysts in the pyrolysis of pine, while quartz sand was used as a reference material in the non-catalytic pyrolysis experiments. The yield of the pyrolysis product phases was only slightly influenced by the structures, at the same time the chemical composition of the bio-oil was dependent on the structure of acidic zeolite catalysts. Ketones and phenols were the dominating groups of compounds in the bio-oil. The formation of ketones was higher over ZSM-5 and the amount of acids and alcohols lower than over the other bed materials tested. Mordenite and quartz sand produced smaller quantities of polyaromatic hydrocarbons than the other materials tested. It was possible to successfully regenerate the spent zeolites without changing the structure of the zeolite.     

Variable-gas-density fluidized bed reactor model for catalytic processes

A generalized fluidized bed reactor model which covers the three fluidization flow regimes most commonly encountered in industry (bubbling, turbulent and fast fluidization) is proposed. The model is based on probabilistic averaging shown previously (Thompson, Bi, & Grace, Chem. Eng. Sci. 54 (1999) 2175; Grace, Abba, Bi, & Thompson, Can. J. Chem. Eng. 77 (1999) 305) to be applicable over a range of superficial gas velocities. In this paper, we extend the model to cases where the volumetric gas flow changes appreciably due to variations in molar flow, pressure and temperature. For the air-based oxy-chlorination process as a case study, it is shown that the volume change affects both the hydrodynamics and the reactor performance. Because the reactions are rapid, almost complete conversion of ethylene is attained immediately above the distributor resulting in an ∼25% reduction in volumetric flowrate. Using the probabilistic averaging technique, the model tracks the probability of being in the bubbling, turbulent and fast fluidization regimes along the reactor height. The impacts of temperature and pressure variations are also examined. The variable density model gives predictions which compare well with commercial data; ignoring density variations leads to significant underprediction.     

A two-phase compartments model for the selective oxidation of n-butane in a circulating fluidized bed reactor

A phenomenological model for the partial oxidation of n-butane to maleic anhydride (MAN) in a gas–solid riser reactor is proposed. The model captures the main transport–kinetic interactions at both the particle and reactor scale. Two different kinetic models from the literature that either include or neglect the role of solid-state diffusion of oxygen in the catalyst bulk are compared in terms of their impact on overall reactor performance. The use of computational fluid dynamics (CFD) as a means of defining a macroscopic cell-type model for describing the flow patterns in an industrial-scale gas–solids riser is also described. Predictions for the conversion of n-butane and yield of MAN are presented as a function of selected operating variables, and the impact of the variable model parameters on the predictions is briefly assessed. It is shown that the predictions are particularly sensitive to the kinetic model. The relative importance of the interactions between the chemical kinetics and the hydrodynamics is also highlighted.     

Pure hydrogen generation in a fluidized bed membrane reactor: Application of the generalized comprehensive reactor model

A generalized comprehensive model was developed to simulate a wide variety of fluidized-bed catalytic reactors. The model characterizes multiple phases and regions (low-density phase, high-density phase, staged membranes, freeboard region) and allows for a seamless introduction of features and/or simplifications depending on the system of interest. The model is implemented here for a fluidized-bed membrane reactor generating hydrogen. A concomitant experimental program was performed to collect detailed experimental data in a pilot scale prototype reactor operated under steam methane reforming (SMR) and auto-thermal reforming (ATR) conditions, without and with membranes of different areas under diverse operating conditions. The results of this program were published in Mahecha-Botero et al. [2008a. Pure hydrogen generation in a fluidized bed membrane reactor: experimental findings. Chem. Eng. Sci. 63(10), pp. 2752-2762]. The reactor model is tested in this second paper of the series by comparing its simulation predictions against axially distributed concentration in the pilot reactor. This leads to a better understanding of phenomena along the reactor including: mass transfer, distributed selective removal of species, interphase cross-flow, flow regime variations, changes in volumetric flow, feed distribution, and fluidization hydrodynamics. The model does not use any adjustable parameters giving reasonably good predictions for the system of study.