Cu-ZnO-Al_2O_3催化剂上甘油氢解制1,2-丙二醇的反应动力学(英文)

A series of Cu-ZnO-Al2O3 catalysts with various metal compositions of Cu/Zn/Al were prepared by the co-precipitation method,and screened for glycerol hydrogenolysis to propylene glycol.The catalyst with a Cu/Zn/Al molar ratio of 1:1:0.5 exhibited the best performance for glycerol hydrogenolysis,and thus selected for kinetic investigation.Under elimination of external and internal diffusion limitation,kinetic experiments were performed in an isothermal fixed-bed reactor at a hydrogen pressure range of 3.0-5.0 MPa and a temperature range of 493-513 K. Based on a dehydration-hydrogenation two-step hydrogenolysis mechanism,a two-site Langmuir-Hinshelwood kinetic model taking into account competitive adsorption of glycerol,acetol and propylene glycol was proposed and successfully fitted to the experimental data.The average relative errors between observed and predicted outlet concentrations of glycerol and propylene glycol were 6.3%and 7.6%,respectively.The kinetic and adsorption parameters were estimated by using the fourth-order Runge-Kutta method together with the Rosenbrock algorithm.The activation energies for dehydration and hydrogenation reactions were 86.56 and 57.80 kJ·mol-1,respectively.     

基于一种改进的自适应遗传算法估算环已烷自催化氧化反应动力学参数

A modified genetic algorithm of multiple selection strategies, crossover strategies and adaptive operator is constructed, and it is used to estimate the kinetic parameters in autocatalytic oxidation of cyclohexane. The influences of selection strategy, crossover strategy and mutation strategy on algorithm performance are discussed. This algorithm with a specially designed adaptive operator avoids the problem of local optimum usually associated with using standard genetic algorithm and simplex method. The kinetic parameters obtained from the modified genetic algorithm are credible and the calculation results using these parameters agree well with experimental data. Furthermore, a new kinetic model of cyclohexane autocatalytic oxidation is established and the kinetic parameters are estimated by using the modified genetic algorithm.     

Degradation Kinetics of Xylose and Glucose in Hydrolysate Containing Dilute Sulfuric Acid

In preparation of fuel alcohol from biomass as feedstock, hydrolysis with dilute acid as catalyst is one way to produce fermentable saccharide, xylose and glucose. However, the acid is also the catalyst in degradation of xylose and glucose and the yield of sacchride is dependent on the kinetic behaviors of saccharide. The degradation kinetics of xylose and glucose in the hydrolysate was investigated under the conventional process conditions of hydrogen ion concentration from 0.05 to 0.2 mol/L and temperature from 150 to 200℃. With a numerical calculation method, the kinetic parameters were estimated, and the activation energy of xylose and glucose in the degradation reaction was obtained. The kinetic equations correlating the effect of hydrogen ion concentration on the rate constants of degradation reaction were established. Comparison between the calculated results from the equations and experimental ones proved that the established kinetic model could satisfactorily predict the degradation behavior of xylose and glucose in the acidic hydrolysate.     

甲苯歧化与C9芳烃烷基转移反应动力学模型和模拟分析

A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity（WHSV）into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giving the guidance to select suitable operating conditions.     

基于Ni/Al2O3催化的异丁烯二聚反应精馏过程的动力学研究（英文）

Isooctane is a promising gasoline additive that could be produced by dimerization of isobutene (IB) with subse-quent hydrogenation. In this work, the dimerization of IB has been carried out in a batch reactor over a temper-ature range of 338–383 K in the presence of laboratory prepared Ni/Al2O3 as a catalyst and n-pentane as solvent. The influence of various parameters such as temperature, catalyst loading and initial concentration of IB was examined. A Langmuir–Hinshelwood kinetic model of IB dimerization was established and the parameters were estimated on the basis of the measured data. The feasibility of oligomerization of IB based on the reactive distil ation was simulated in ASPEN PLUS using the kinetics developed. The simulation results showed that the catalyst of Ni/Al2O3 had higher selectivity to diisobutene (DIB) and slightly lower conversion of IB than ion exchange resin in the absence of polar substances.     

溶液自发结晶过程动力学参数研究

The batch cooling crystallization initiated from spontaneous nucleation for aqueous solution of potas- sium nitrate was studied.The concentration and transmittance data were acquired on line throughout the operation. Based on solute mass transfer in both liquid and solid phases,a kinetic model was deduced by assuming that the late period of primary nucleation resembles the initial period of the secondary nucleation.Nucleation and crystal growth stages were identified.Kinetic parameters were estimated piecewise from online experimental data and compared with those in literature.The estimated kinetic parameters for stages without apparent primary nucleation agreed well with those in literature.Further,a simulated concentration curve was also drawn from the estimated kinetic parameters and it matched well with that in experiment.     

MATHEMATICAL MODELING OF NON-CATALYTIC LIQUID-SOLID REACTION AND ITS SOLUTION BY ORTHOGONAL COLLOCATION

The mathematical model of non-catalytic liquid-solid diffusion reactions discussed in this paper can be applied to quite different cases. The models in the literature such as unreacted shrinking core model, two stage model and homogeneous model can be considered as special cases of the above model which has been derived for leaching vanadium from steel slag with sodium carbonate and]or sodium bicarbonate solution reacting with two components in the slag simultaneously. The vanadium leaching reaction is inhibited by the solid product formed during the reaction. The power law equation can be used to represent the kinetic experimental data of leaching reaction. The model equations have been solved by orthogonal collocation and semi-implicit Runge-Kutta method. The parameters of the model have been estimated by the complex method. The calculated results based on this model is in good agreement with experimental data.     

ZL50活性炭吸附脱除二氧化硫的吸附动力学模型(英文)

A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO2 in flue gas by carbon adsorbents for flue gas purification. The change in adsorption capacity and adsorption rate with time at different water vapor concentrations and different SO2 concentrations was studied. The model was in good agreement with experimental data. The surface reaction was probably the rate controlling step in the early stage for SO2 adsorption by ZL50 activated carbon. The parameters m and n in the nth order adsorption kinetic model were related to the magnitude of the time compensation and adsorption driving force, respectively. The change of parameter n with water vapor concentrations and sulfur dioxide concentrations was studied and some physical implications were given. The sum of square errors was less than 1.0 and the average absolute percentage deviations ranged from 0.5 to 3.2. The kinetic model was compared with other models in the literature.     

Catalytic kinetics of dimethyl ether one-step synthesis over CeO_2–CaO–Pd/HZSM-5 catalyst in sulfur-containing syngas process

CeO_2–CaO–Pd/HZSM-5 catalyst was prepared for the dimethyl ether(DME) one-step synthesis in a continuous fixed-bed micro-reactor from the sulfur-containing syngas. The catalytic stability over hybrid catalyst of CeO_2–CaO–Pd/HZSM-5 was investigated to ensure that the kinetics experimental results were not significantly influenced by induction period and catalytic deactivation. A large number of kinetic data points(40 sets) were obtained over a range of temperature(240–300 °C), pressure(3–4 MPa), gas hourly space velocity(GHSV)(2000–3000 L·kg~(-1)·h~(-1)) and H_2/CO mole ratio(2–3). Kinetic model for the methanol synthesis reaction and the dehydration of methanol were obtained separately according to reaction mechanism and Langmuir–Hinshelwood mechanism. Regression parameters were investigated by the method combining the simplex method and Runge–Kutta method. The model calculations were in appropriate accordance with the experimental data.     

离子交换树脂催化乳酸与异丁醇及正丁醇酯化反应的动力学研究

The esterification reactions of lactic acid with isobutanol and n-butanol have been studied in the presence of acid ion-exchange resin Weblyst D009. The influences of catalyst loading, stirrer speed, catalyst particle size, initial reactant molar ratio and temperature on the reaction rate have been examined. Experimental kinetic data were correlated by using the Pseudo-homogeneous, Langmuir-Hinshelwood and Eley-Rideal models. Nonideality of the liquid phase was taken into account by using activities instead of molar fractions. The activity coefficients were calculated according to the group contribution method UNIFAC. Provided that the nonideality of the liquid is taken into account, the esterification kinetics of lactic acid with isobutanol and n-butanol catalyzed by the acid ion-exchange resin can be described using all three models with reasonable errors.     

Optimal operation of a catalytic tubular reactor with fouling catalyst by coke deposition

The dehydrogenation of isopentane over chromia-alumina catalyst has been carried out at three isothermal levels. The catalyst fouling and the deposited coke profiles were observed in a catalytic tubular reactor. A kinetic model is proposed and the kinetic parameters have been estimated by non linear regression methods.For the dehydrogenation with catalyst fouling, the problem of finding the isothermal optimal control was formulated by a distributed maximum principle and a computational algorithm using a quasi-steady state assumption was presented. The dehydrogenation of isopentane was carried out experimentally at the evaluated isothermal optimal temperature. The observed conversion, yields and coke content profiles agreed with the evaluated ones fairly well, which suggests that the kinetic model may be useful for optimal controls.     

Kinetic study of olefin polymerization with a supported metallocene catalyst. I. Ethylene/propylene copolymerization in gas phase

A kinetic study of ethylene homopolymerization and copolymerization is conducted with a supported metallocene catalyst in a gas‐phase reactor. An experimental procedure is developed that minimizes the effect of impurities in the reactor and simultaneously yields consistent and reproducible reaction‐rate data. The effects of operational parameters such as reaction temperature, pressure, and comonomer concentration on the kinetics of both homopolymerization and copolymerization are investigated. Online perturbation techniques are implemented to determine key kinetic parameters such as the activation energies for ethylene propagation and catalyst deactivation. A reaction‐rate order close to 2 is obtained for ethylene homopolymerization from pressure perturbations, while near to first‐order dependency is observed in the presence of propylene. To quantify the effects of the operational parameters, a one‐site kinetic model for homopolymerization and a two‐site kinetic model for copolymerization are proposed. The necessary kinetic parameters in the model are estimated using the POLYRED™ package. The resulting kinetic model represents the kinetic data over a wide range of conditions for this supported metallocene catalyst. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 81–114, 2001     

Modeling residue hydrotreating

In this paper a kinetic model for the residue hydrotreating is presented. The model considers kinetics, adsorption and diffusion inside the hydrodemetallization catalyst pellets. The diffusion is described by the Stefan–Maxwell equations extended for starkly different sized molecules, due to molecular size of residue molecules large distribution. Effective diffusion coefficients vary with porosity and tortuosity evolution due to volume constraints in the catalyst pellets. The model's kinetic and thermodynamic parameters were estimated from a set of experiments carried out in a batch reactor with a Middle East vacuum residue. A comparison between experimental and simulated metal profiles inside the catalyst exhibit the slow diffusion, validating the importance of adding mass transfer phenomena and considering volume constraints even in a macroporous demetallization catalyst.The model was validated by other tests performed in the same reactor using the same vacuum residue, but with different catalysts. The differences in the catalyst pore size allowed to predict all the hydrotreatment yields, showing diffusion is a crucial factor.     

环氧乙烷非均相催化水合动力学及均温反应器热稳定性分析

采用碳纳米管增强复合材料催化剂,在等温积分反应器中获得环氧乙烷非均相催化水合宏观反应动力学实验数据,建立了幂函数型宏观反应动力学方程,采用Levenberg-Marquardt法对动力学模型参数进行估算,并以该动力学模型为基础,分析了均温反应器的热稳定性。结果表明,生成乙二醇主反应的表观活化能为71.7 k J/mol,与两个典型的串联副反应的活化能接近。模型参数统计检验结果表明,该宏观动力学方程参数是适定的,可用于工业反应器的设计。给出的反应器关键参数的计算方法,可为乙二醇合成反应器的模拟计算和设计开发提供必要的依据。     

苯加氢催化反应动力学研究

文章采用溶胶-凝胶法制备NiO-MoO3/Al2O3-TiO2催化剂,研究基于该催化剂苯加氢生成环己烷的反应。利用实验数据对几种可能的动力学模型进行参数估值,得到该反应的动力学模型。     

低汽/气LB型中温变换催化剂宏观动力学

采用磁力搅拌内循环无梯度反应器,对低汽/气LB型一氧化碳中温变换催化剂的宏观反应特性进行了实验研究?并以Simplex法对实验数据进行非线性参数估值,建立了能良好吻合实验数据的二级反应模式的LB中温变换催化剂加压宏观动力学模型。     

八碳芳烃临氢异构化反应动力学模型

针对某实际工业异构化装置,在已开发的八碳芳烃临氢异构化反应网络的基础上,将系统中的八碳环烷烃和八碳链烷烃作为一个集总组分,提出新的六组分异构化反应网络,由此建立了适用于工业生产的八碳芳烃临氢异构化反应动力学模型.考虑结焦对催化剂活性的影响,提出了一种经验形式的催化剂失活函数,能够合理地描述催化剂失活过程.采用四五阶Runge-Kutta法对模型方程进行数值求解,基于多套稳态平衡数据采用差分变尺度优化算法(BFGS)对动力学参数进行估计,进而在不同操作条件下对模型进行验证.结果表明估计值与工业标定值相当吻合,达到了工业应用的模拟精度要求.     

A simplified model for biomass pyrolysis in a fluidized bed reactor

A reaction scheme of a set of three parallel reactions followed by a set of two parallel reactions has been used to describe the primary and secondary reactions of biomass pyrolysis in a fluidized bed reactor. A simple first-order kinetic approach has been applied to predict the product yields. The pyrolysis model detailed in this paper is actually a sub-model. The effects of operating parameters on biomass pyrolysis product yield were simulated. Results show that reaction temperature plays an important role in the yield of bio-oil. The model is robust and can predict good results in a gasification environment as well. Good agreement between predicted and published results was obtained.     

A new mechanistic model for liquid-liquid phase transfer catalysis: Reaction of benzyl chloride with aqueous ammonium sulfide

A new mechanistic model for reactions involving two liquid phases and a homogeneous phase transfer catalyst (PTC) has been developed based on extraction mechanism considering the equilibrium of catalyst and active catalysts at the interface. The proposed kinetic model considers thermodynamic framework based aqueous phase ionic equilibrium and the separate contributions of non-PTC and PTC-enhanced reactions towards the overall reactions. The developed model was then applied to an industrially important reaction of benzyl chloride with aqueous ammonium sulfide for synthesis of dibenzyl sulfide and benzyl mercaptan. The kinetic parameters of the developed model were estimated at different temperatures using an indigenously developed non-linear regression technique based on modified Levenberg-Marquardt algorithm. Sensitivity analysis was then performed under various experimental conditions using the estimated parameters and the results were compared with experimental observations. A good agreement was observed between experimental and calculated values with proper trends of the results.     

Kinetic studies of the autothermal reforming of tetradecane over Pt/Al2O3 catalyst in a fixed-bed reactor

Kinetics of autothermal reforming (ATR) of tetradecane on Pt-Al₂O₃ catalyst over the temperature range 750-900 °C is investigated. Experimental results obtained from NETL (US-DOE) are used for model parameter estimation and validation. Two Langmuir-Hinshelwood-Hougen-Watson (LHHW) type rate models are developed and subjected to parameter estimation and model discrimination. LHHW model in which hydrocarbon is adsorbed on the catalyst surface as alkyl intermediate species by scission of C-H bond gave physically meaningful parameters. Parameters are estimated by using generalized reduced gradient method in spreadsheet and sequential quadratic programming in Matlab. The estimated parameters for the selected model are thermodynamically consistent. The developed kinetic model could capture the experimental behavior of the process and could predict the outlet composition within 25% error.