铜锌铝催化剂上变换反应动力学的研究 Ⅱ.二维多组分扩散模型及效率因子的数值解

本文研究在铜锌铝催化剂上,一氧化碳变换反应中的气体扩散速率对化学反应速率的影响。建立了各反应气体在柱形催化剂内扩散过程的数学模型;并用正交配置法将模型离散后,以拟牛顿法求得数值解,获得颗粒内的气体浓度分布及催化剂的效率因子,并与其它简化模型作了比较;同时通过实验获得化学反应本征动力学方程及宏观反应速率,从而求得效率因子实验值。二维多组分扩散模型理论计算值与实验值是比较接近的,最高偏差13%,平均偏差为7.5%。而一维模型的偏差比其大2—3%,但能简化计算,节省机时。     

工业Fe-Mn催化剂上基于详细反应机理的F-T合成动力学模型Ⅰ.烯烃再吸附动力学研究

 利用转篮式无梯度反应器,在工业Fe-Mn催化剂上,在较宽的工业操作相关的反应条件下进行了F-T合成反应动力学研究. 首次提出了利用转篮式无梯度反应器反应气氛和反应温度均一的优势,将烃生成反应动力学的估算从传统的对烃生成和水煤气变换这两类发生在不同活性中心的反应同时进行估算的方法中分离出来,简化了烃生成动力学模型的计算. 在基于亚甲基插入的亚烷基机理动力学模型基础上,考虑到乙烯与催化剂表面强的相互作用,将乙烯和乙烷的生成动力学参数单独计算. 动力学模型计算的链增长、烷烃和烯烃生成的活化能均与文献报道值具有较好的一致性. 由F-T合成动力学模型计算的合成气消耗速率、甲烷生成速率和C5+的生成速率较好地与实验值吻合. 通过动力学模型并结合实验结果分析发现,未考虑除化学反应之外的非本征因素的烯烃再吸附动力学模型不能够正确预测烃产物分布偏离ASF规律及烯烷比随碳数增加而下降的现象.     

MFT改质反应ZSM-5分子筛催化剂结焦行为的研究 Ⅰ.结焦动力学与机理

建立了ＭＦＴ合成（ＭｏｄｉｆｉｅｄＦｉｓｃｈｅｒＴｒｏｐｓｃｈＳｙｎｔｈｅｓｉｓ）工艺中ＺＳＭ５分子筛催化剂上转化的结焦动力学模型，获得了合理的模型参数，模型计算值与实验值的相对误差在±１０％以内。利用所建动力学模型可以准确地预测ＭＦＴ工业改质反应器出口附近催化剂上的焦含量。根据获得的动力学模型及模型参数的意义，对结焦机理进行了探讨     

MFT改质反应ZSM—5分子筛催化剂结焦行为的研究：I.结焦动力学？…

建立了ＭＦＴ合成（ＭｏｄｉｆｉｅｄＦｉｓｃｈｅｒ－ＴｒｏｐｓｃｈＳｙｎｔｈｅｓｉｓ）工艺中ＺＳＭ－５分子筛催化剂上转经的结焦动力学模型，获得了合理的模型参数，模型计算值与实验值的上对误差在±１０％以内，利用新建动力学模型可以准确地预测ＭＦＴ工业改质反应器出口附近催化剂上的焦含量，根据获得的动力学模型及模型参数的意义，对结焦机理进行了探讨。     

在Pt/Al2O3催化剂上苯的内扩散对负0.9级动力学的影响

在Pt/Al₂O₃催化剂上用外循环反应器研究了内扩散对苯完全氧化动力学的影响,当用30～40目(即0.45～0.60mm)催化剂时反应在动力学区域进行.若O₂过量时则动力学区域苯的完全氧化可用-0.9级速率方程描述.当催化剂粒径增至φ6×5mm时,反应在内扩散区域进行并变为一0.1级反应.催化剂有效因子η在0.24～0.12之间.在同一温度下,η_实验随苯分压p_苯的增加而增大;而p_苯相近时,η_实验则随温度的升高而减小.动力学区域的反应活化能为55.5kJ/mol,内扩散区域的反应活化能为34.9kJ/mol,其值约为动力学区域的活化能与苯分子扩散活化能的算术平均值.     

C302铜基催化剂上甲醇合成的动力学研究 Ⅱ.动力学模型的工业检验

以Ｌｕｒｇｉ型甲醇合成反应器一维非均相数学模型和单颗粒催化剂反应－扩散模型为基础,通过模拟分析及与工业生产数据相对照的方式,对六种具有不同结构的Ｃ３０２催化剂动力学模型进行了工业应用检验,将六种模型用于非等温工业反应器性能分析时,有的模型模拟结果偏离实际情况较远,表明动力学模型结构对反应器模拟结果有较大的影响,有必要对用等温动力学实验数据和方法确立的动力学模型从工业应用角度做进一步检验。基于这一观点,最终确定了三种比较适宜于工业应用的Ｃ３０２催化剂的动力学模型。     

煤焦催化气化活性位扩展模型的研究

针对煤催化气化反应中传统的煤气化动力学模型不再适用或应用范围受到限制的现实，从催化作用机理分析入手，以煤焦CO2催化气化为研究对象，建立了描述气化反应速率与转化率关系的动力学模型——活性位扩展模型。并以KCl催化剂及K-Ni(10%Ni)复合催化剂作用下神府煤焦CO2气化的实验结果对模型进行验证。结果表明，活性位扩展模型很好地体现了煤焦催化气化的动力学规律，即催化剂的添加，有效地增大了反应界面处的活性部位和活性表面积，使气化反应在更温和的条件下快速进行；模拟值与实验值吻合较好，最大偏差10%。由于反应初期的传质阻力不可忽略，实验值与模拟值存在一定误差。     

高浓度杂多酸溶液催化性能的研究Ⅰ.一种新型异丁烷/丁烯烷基化催化剂

在异丁烷/丁烯烷基化反应中研究了一种由杂多酸和醋酸组成的新型液体酸催化剂的催化性能,醋酸作为溶剂对杂多酸具有共协效应,系统研究了形成活性相的条件,杂多酸结晶水含量对活性相的形成和催化活性均有显著影响,这一催化体系具有与硫酸可比的催化活性.     

Ni-Mg复合催化剂催化裂解CH_4制氢动力学研究

基于定温热重实验,建立了甲烷催化裂解反应动力学模型和催化剂表面积炭失活动力学模型。其中,甲烷催化裂解动力学模型将初始产氢速率视为催化剂未积炭条件下的动力学基础数据;催化剂表面积炭失活动力学则基于甲烷催化裂解速率的降低。实验使用Ni-Mg复合催化剂,分别在535、585、635℃,甲烷分压10~4、2×10~4、3×10~4Pa条件下展开甲烷催化裂解动力学特性研究。结果表明,甲烷催化裂解的反应级数为0.5,活化能为82 k J/mol;Ni-Mg复合催化剂反应失活级数为0.5,催化剂失活活化能为118 k J/mol。实验条件下均制得了多壁碳纳米管。     

环己烷催化氧化制取顺酐和醋酸的催化剂研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采取不同的方法制备了系列固体VPO催化剂.借助XRD、FT-IR对催化剂进行了主体晶相确定，用氧化还原滴定方法测定了不同晶相催化剂中钒的平均氧化数.结合催化反应的活性评价，发现催化剂主体晶相、结晶度、活化气氛和催化剂的V4＋/V5＋比均对目标反应的催化活性产生影响，5种催化剂中以(VO)2P2O7晶相催化剂的活性为最高.     

Esterification reaction kinetics of acetic acid and n-pentanol catalyzed by sulfated zirconia

This study reports experimental data and kinetic modeling of acetic acid esterification with n-pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well-mixed batch reactor at different temperatures (50-80°C), n-pentanol to acid molar ratios (1:1-3:1), and catalyst loadings (5-10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo-homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n-pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol⁻¹, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism.     

Kinetics of catalyzed esterification of acetic acid with n-butanol using carbonized agro-waste

The objective of this research work was to investigate the kinetics of esterification of acetic acid with n-butanol through the variation of experimental parameters. The reaction mixture was catalyzed heterogeneously by a sulfonated catalyst in batch mode of operation. The catalyst was prepared from abundantly available agro-waste, Cajanus cajan husk by chemical activation process, which produces a carbon-based solid catalyst with high surface area. The catalyst was characterized by a Brunauer-Emmet-Teller surface analyzer and Fourier transform infrared spectroscopy to know the surface morphology. Process parameters such as contact time, reaction temperature, and catalyst loading, which can influence the extent of conversion of reactants, were studied. Furthermore, the kinetic investigation was also carried out to estimate the kinetic parameters for uncatalyzed and catalyzed reaction using the second-order pseudo-homogeneous (P-H), Eley-Rideal (E-R), and Langmuir-Hinshelwood (LH) kinetic models for this research work. The kinetic parameters such as activation energy, preexponential factor, and the thermodynamic parameters such as enthalpy and entropy were estimated for uncatalyzed and catalyzed reactions using these three models. The process conditions were optimized for catalyzed and uncatalyzed reactions to obtain the maximum product yield by minimizing root mean square error of each experimental data using the MS-excel solver tool. Thus, this study reveals the high potential of an agro-waste, Cajanus cajan husk as raw material for the synthesis of catalyst. The results show that the E-R model is more appropriate for predicting the dynamic data of an esterification reaction, as the forward rate of reaction estimated using the E-R model are more modified than P-H and L-H models.     

Kinetic modeling of liquid-phase esterification of acetic acid with n-butanol using heterogeneous poly(o-methylene p-toluene sulfonic acid) as catalyst

Liquid-phase esterification of acetic acid with n-butanol to n-butyl acetate is studied in the presence of a polymeric catalyst, that is, poly(o-methylene p-toluene sulfonic acid). The performance of the proposed catalyst is compared with the other commercially available homogeneous and heterogeneous catalysts in terms of its activity. Experiments are conducted in an isothermal stirred batch reactor to study the effects of speed of agitation, temperature, and catalyst loading on the rate of reaction. A concentration-based pseudo-homogeneous (PH) kinetic model and activity-based kinetic models such as PH, Eley-Rideal (ER), and Langmuir-Hinselwood-Hougen-Watson (LHHW) models are developed. All the models considered in this study resulted in similar percentage deviation close to 4%. Further, kinetic models are validated through additional experiments, and it is observed that the simple concentration-based PH model is able to predict experimental data with least deviation compared to activity-based PH, ER, and LHHW models. The developed kinetic models are also tested using the Fisher-Snedecor test (F-test) and are found to be acceptable. By incorporating both modeling data and validation data, the overall absolute average deviations of different models are found to be concentration-based PH model 4.354%, activity-based PH model 5.006%, ER I model 5.189%, ER II model 5.403%, ER III model 5.437%, and LHHW model 6.104%, illustrating the superiority of the simple concentration-based PH model.     

Kinetic study on the reaction of lauric acid with ethanol catalyzed by deep eutectic solvent based on cetyl trimethyl ammonium bromide

In this work, a novel type of deep eutectic solvents (DES: CTAB–DES) based on cetyl trimethyl ammonium bromide (CTAB) was successfully synthesized by mixing CTAB with p-toluenesulfonic acid monohydrate and applied as catalysts for the esterification reaction of ethanol and lauric acid. The kinetics of the reaction of ethanol and lauric acid catalyzed by CTAB–DES was investigated in the temperature range of 328.15–348.15 K. The influence of different parameters including agitation speed, temperature, catalyst loading, and the lauric acid to ethanol molar ratio on the conversion of lauric acid was discussed. The kinetic experimental data obtained were correlated by the pseudo-homogeneous model, and the results show that it can predict the reaction process well. Moreover, CTAB–DES can be reused six times without any significant decrease in catalytic activity.     

固体酸催化剂催化酯化反应研究：Ⅰ.催化剂的制备及性能

酯化反应是基本有机化学中的一个重要反应,传统上使用的浓H_2SO_4催化剂常常引起一些严重问题.如:设备腐蚀严重,引起副反应及产生大量难以处理的含酸残液等.近年来,采用各种分子筛,氧化物及超强酸等作为该过程的催化剂的研究工作多见报道,这些工作无疑具有重要意义,但主要问题在于低温催化活性不高.     

Development of kinetic models for acid‐catalyzed methyl acetate formation reaction: Effect of catalyst concentration and water inhibition

The reaction kinetics of reversible liquid‐phase esterification of acetic acid with methanol is investigated in the temperature range 26–50°C using sulfuric acid catalyst. The main goal of this work is to study the effect of catalyst concentration and sensitivity to the presence of water on the rate expression of this industrially important reaction. Experiments are conducted in an isothermal batch reactor and a second‐order kinetic model is used to correlate the experimental data, which are found to fit well with the assumed kinetic model in terms of the concentrations of reactants and products. Furthermore, an activity‐based kinetic model is also developed employing the UNIQUAC (universal quasi‐chemical equation) model to compute the activities. It is observed that the rate constant is influenced by the concentration of catalyst, and the reaction rate increased with an increase in the catalyst concentration. It is also observed that the catalyst activity is slightly inhibited by the water present in the reaction mixture. The performance of the proposed models is compared with that of other models reported in the literature, and it is found that the proposed models outperformed all the other models reported in the literature. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 263–277, 2011     

取代乙酸配体对乙炔二聚反应催化剂性能的影响

研究了取代乙酸配体作为Ｎｉｅｕｌａｎ催化剂对乙炔二聚反应性能的影响。结果表明，不同功能结构数目的影响，结果表明，不同功能结构数目的的氨羧配体均使催化剂的选择性提高。乙炔转化率略有下降，巯基乙酸配体的加入，则改变了乙炔二聚反应的机理，得到以乙醛为主的产物。     

Glycerol acetylation considering competing dimerization

Glycerol acetylation is a very interesting reaction for studies of consecutive kinetics. In this short communication, we present a pseudo-homogeneous model for the synthesis of triacetyl glycerol from the reaction of glycerol and acetic acid over strongly acidic Amberlyst-15 and Amberlyst-70 catalysts, considering a dimerization of diacetyl glycerol (DAG) into diglycerol tetraacetate as a parallel reaction and compare the results with a model without side reactions. The best fits were obtained for apparent zeroth-order dimerization and first-order consecutive reactions in the presence of acetic acid in excess and with removal of water. An adaptation was made for DAG. The proposed model shows that the formation of DAG is faster than the consumption of glycerol, which could be an explanation for the occurrence of DAG dimerization instead of other parallel reactions in acetylation.     

Kinetic studies for the esterification of acetic acid with epichlorohydrin over an anion exchange resin catalyst

The kinetics of the esterification reaction between acetic acid and epichlorohydrin catalysed by Purolite A-520E strong basic anion exchange resin was studied. The effects of certain parameters such as stirring speed, particle diameter, temperature, catalyst amount and molar ratio between reactants were experimentally determined. It was found that the overall reaction rate is intrinsically kinetically controlled. The partial orders of reaction with respect to catalyst, acetic acid and epichlorohydrin were determined. A reaction mechanism is proposed. Based on chromatographic data and taking into account the partial orders of reaction, a more detailed kinetic model is suggested.      

KINETIC STUDY OF CARBONYLATION OF METHANOL TO ACETIC ACID AND ACETIC ANHYDRIDE OVER A NOVEL COPOLYMER-BOUND CIS-DICARBONYLRHODIUM COMPLEX

The kinetic study of carbonylation of methanol-acetic acid mixture to acetic acid and acetic anhydride over a cis-dicarbonylrhodium complex (MVM' Rh) coordinated with the ethylene diacrylate (M') crosslinked copolymer of methyl acrylate (M) and 2-vinylpyddine (V)shows that the rate of reaction is zero order with respect to both reactants methanol and carbon monoxide, but first order in the concentrations of promoter methyl iodide and rhodium in the complex. Polar solvents can accelerate the reaction. Activation parameters were calculated from the experimental results, being comparable to that of the homogeneous system. A mechanism similar to that of soluble rhodium catalyst was proposed.