矿物均相酸催化剂催化甲醇和乙酸酯化反应动力学(英文)

In this work, esterification of acetic acid and methanol to synthesize methyl acetate in a batch stirred reactor is studied in the temperature range of 305.15–333.15 K. Sulfuric acid is used as the homogeneous catalyst with concentrations ranging from 0.0633 mol·L?1 to 0.3268 mol·L?1. The feed molar ratio of acetic acid to methanol is varied from 1:1 to 1:4. The influences of temperature, catalyst concentration and reactant concentration on the reaction rate are investigated. A second order kinetic rate equation is used to correlate the experimental data. The forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot. The developed kinetic model is compared with the models in literature. The developed kinetic equation is useful for the simulation of reactive distillation column for the synthesis of methyl acetate.     

用离子液体作催化剂和夹带剂时在反应萃取精馏塔中乙酸甲酯和正丁醇酯交换反应的模拟

A new reactive and extractive distillation process with ionic liquids as entrainer and catalyst (RED-IL) was proposed to produce methanol and n-butyl acetate by transesterification reaction of methyl acetate with n-butanol. The RED-IL process was simulated via a rigorous model, and high purity products of methanol and n-butyl acetate can be obtained in such a process. The effects of reflux ratio, feed mode, holdup, feed location, entrainer ratio and catalyst concentration on RED-IL process were investigated. The conversion of methyl acetate and purities of products increase with the holdup in column, entrainer ratio and catalyst content. An optimal reflux ratio exists in RED-IL process. Comparing to the mixed-feed mode, the segregated-feed mode is more effective, in which the optimal feed locations of reactants exist.     

垂直管式反应器中超临界甲醇连续制备生物柴油I:相含率及反应中间产物的轴向分布(英文)

Production of biodiesel with supercritical methanol is a green synthesis process.A study was carried out in a vertical tubular reactor with a length of 3700 mm and a diameter of 20 mm at 275-375°C,15 MPa,and molar ratio of methanol to soybean oil of 40︰1.The phase holdup,intermediate product,yield and axial distribution of methyl ester(ME) were investigated.Methanol and oil were mixed non-uniformly due to the formation of biodiesel and difference in their densities,even when the reaction system was in the supercritical state.From top to bottom,the phase holdup of methanol increased and that of oil decreased.As temperature increased,the concentrations of monoglyceride and diglyceride decreased gradually and the ME yield increased.When the temperature reached 300°C,the critical temperature of the system,the ME yield was 50%.Further increase in temperature led to a sharp in-crease of ME yield.However,at 375°C after 1200 s of reaction time,the decomposition rate of ME was greater than its formation rate,reducing the ME yield.     

Estimation of Time to Maximum Rate Under Adiabatic Conditions（TMRad） Using Kinetic Parameters Derived From DSC-Investigation of Thermal Behavior of 3-Methyl-4-Nitrophenol

Kinetic parameters of the decomposition of hazardous chemicals can be applied for the estimation of their thermal behavior under any temperature profile.Presented paper describes the application of the advanced kinetic approach for the determination of the thermal behavior also under adiabatic conditions occurring e.g.in batch reactors in case of cooling failure.The kinetics of the decomposition of different samples(different manufacturers and batches) of 3-methyl-4-nitrophenol were investigated by conventional DSC in non-isothermal(few heating rates varying from 0.25 to 8.0K/min) and isothermal(range of 200~260℃) modes.The kinetic parameters obtained with AKTS-Thermokinetics Software were applied for calculating reaction rate and progress under different heating rates and temperatures and verified by comparing simulated and experimental signals.After application of the heat balance to compare the amount of heat generated during reaction and its removal from the system,the knowledge of reaction rate at any temperature profiles allowed the determination of the temperature increase due to the self-heating in adiabatic and pseudo-adiabatic conditions.Applied advanced kinetic approach allowed simulation the course of the Heat-Wait-Search(HWS) mode of operation of adiabatic calorimeters.The thermal safety diagram depicting dependence of Time to Maximum Rate(TMR) on the initial temperature was calculated and compared with the results of HWS experiments carried out in the system with Ф-factor amounting to 3.2.The influence of the Ф-factor and reaction progress reached at the end of the HWS monitoring on the TMR is discussed.Presented calculations clearly indicate that even very minor reaction progress reduces the TMRad of 24h characteristic for a sample with initial reaction progress amounting to zero.Described estimation method can be verified by just one HWS-ARC,or by one correctly chosen ISO-ARC run of reasonable duration by knowing in advance the dependence of the TMR on the initial temperature for any Ф-factor.Proposed procedure results in significant shortening of the measuring time compared to a safety hazard approach based on series of ARC experiments carried out at the beginning of a process safety evaluation.     

Reaction kinetics and internal diffusion of Zhundong char gasification with CO2

Mass transfer usually affects the rate of chemical reactions in coal.The effect of internal diffusion on char gasification with CO₂ in the temperature range from 1123 K to 1273 K was investigated via thermo-gravimetric analysis and assessment of char morphology features.The results revealed that the effect of internal diffusion on the initial reaction rate was more significant with an increase of particle size,due to the concentration gradient of the gasification agent within the solid particles.In the early stage of gasification,the generation of new micropores and the opening of closed pores led to an increase in specific surface area.As the reaction proceeded,the openings were gradually expanded and the specific surface area continued to increase.However,with further reaction,disappearance of edge pores,melting and collapse of the pore structure led to a decrease in specific surface area.The intrinsic activation energy and reaction order based on the nth-order model were 157.67 kJ?mol^?1 and 0.36,respectively.Thus,temperature zones corresponding to chemical reaction and diffusion control were identified.Moreover,the calculated effectiveness factor provided a quantitative estimation of internal diffusion in the initial stage.     

对苯二甲酸-丁二醇催化单酯化反应动力学(英文)

The chemical kinetics of the monoesterification between terephthalic acid (TPA) and 1,4-butanediol (BDO) catalyzed by a metallo-organic compound was studied using the initial rate method. The experiments were carried out in the temperature range of 463-483 K, and butylhydroxyoxo-stannane (BuSnOOH) and tetrabutyl titanate [Ti(OBu)4] were used as catalyst respectively. The initial rates of the reaction catalyzed by BuSnOOH or Ti(OBu)4 were measured at a series of initial concentrations of BDO (or TPA) with the concentration of TPA (or BDO) kept constant. The reaction orders of reagents were determined by the initial rate method. The results indicate that the reaction order for TPA is related with the species of catalyst and it is 2 and 0.7 for BuSnOOH and Ti(OBu)4 respectively. However, the order for BDO is the same 0.9 for the two catalysts. Furthermore, the effects of temperature and catalyst concentration are investigated, and the activation energies and the reaction rate constants for the two catalysts were deter-mined.     

硫酸-糖蜜酒精废液浸出软锰矿的动力学(英文)

The kinetics of reductive leaching of manganese from low grade pyrolusite in dilute sulfuric acid in the presence of molasses alcohol wastewater was investigated. The shrinking core model was applied to quantify the effects of reaction parameters on leaching rate. The leaching rate increases with reaction temperature, concentrations of H 2 SO 4 and organic matter in molasses alcohol wastewater increase and ore particle size decreases. The leaching process follows the kinetics of a shrinking core model and the apparent activation energy is 57.5 kJ·mol –1 . The experimental results indicate a reaction order of 0.52 for H2SO4 concentration and 0.90 for chemical oxygen demand (COD) of molasses alcohol wastewater. It is concluded that the reductive leaching of pyrolusite with molasses alcohol wastewater is controlled by the diffusion through the ash/inert layer composed of the associated minerals.     

Catalytic ozonation of volatile organic compounds (ethyl acetate) at normal temperature

Catalytic treatments of VOCs at normal temperature can greatly reduce the cost and temperature of processing, and improve the safety factor in line with the requirements of green chemistry. Activated carbon fiber(ACF) was pretreated with 10% H_2SO_4 by single factor optimization to increase specific surface area and pore volume obviously. The catalytic ozonation performance of ACF loaded with Au, Ag, Pt and Pd noble metals on ethyl acetate was investigated and Pd/ACF was selected as the optimal catalyst which had certain stability. Pd is uniformly distributed on the surface of ACF, and Palladium mainly exists in the form of Pd~0 with a amount of Pd~(+2). The specific surface area of the catalysts gradually decreases as the loading increases. The activation energy of ethyl acetate calculated by Arrhenius equation is 113 kJ·mol~(-1). With 1% Pd loading and the concentration ratio of ozone to ethyl acetate is 3:1, catalytic ozonation performance is maximized and the conversion rate of ethyl acetate reached to 60% in 30–50 ℃ at 15,000–30,000 h~(-1).     

温度和游离氨对絮状和颗粒污泥硝化系统的短期影响(英文)

The short-term effects of temperature and free ammonia (FA) on ammonium oxidization were investigated in this study by operating several batch tests with two different partial nitrification aggregates, formed as either granules or flocs. The results showed that the rate of ammonium oxidation in both cultures increased significantly as temperature increased from 10 to 30 °C. The specific ammonium oxidation rate with the granules was 2-3 times higher than that with flocs at the same temperature. Nitrification at various FA concentrations and temperatures combination exhibited obvious inhibition in ammonium oxidation rate when FA was 90 mg·L 1 and tempera- ture dropped to 10 °C in the two systems. However, the increase in substrate oxidation rate of ammonia at 30 °C was observed. The results suggested that higher reaction temperature was helpful to reduce the toxicity of FA. Granules appeared to be more tolerant to FA attributed to the much fraction of ammonia oxidizing bacteria (AOB) and higher resistance to the transfer of ammonia into the bacterial aggregates, whereas in the floc system, the bacteria distributed throughout the entire aggregate. These results may contribute to the applicability of the nitrifying granules in wastewater treatment operated at high ammonium concentration.     

Coupling non-isothermal trickle-bed reactor with catalyst pellet models to understand the reaction and diffusion in gas oil hydrodesulfurization

In this work, a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction–diffusion behaviors in gas oil hydrodesulfurization(HDS). The non-isothermal reactor model is determined to be reasonable due to non-negligible temperature variation caused by the reaction heat. The reaction rate along the reactor is mainly dominated by the temperature,and the sulfur concentration gradient in the catalyst pellet decreases gradually along the reactor, leading to the increased internal effectiveness factor. For the fixed catalyst bed volume, there exists a compromise between the catalyst reaction rate and effectiveness factor. Under commonly studied catalyst pellet size of 0.8–3 mm and porosity of 0.4–0.8, an optimization of the temperature and catalyst pellet structures is carried out, and the optimized outlet sulfur content decreases to 7.6 wppm better than the commercial level at 0.96 mm of the catalyst pellet size and 0.40 of the catalyst porosity.     

Kinetics of esterification of benzyl alcohol with acetic acid catalysed by cation-exchange resin (Amberlyst-15)

Esterification of benzyl alcohol with acetic acid catalysed by Amberlyst-15 (cation-exchange resin) was carried out in a batch reactor in the liquid phase in the temperature range 328–359 K and at 1 atm. The reaction rate increased with increase in catalyst concentration and reaction temperature. Resin particle size and stirrer speed had virtually no effect on the rate under the experimental conditions. The rate data were correlated with a kinetic model based on homogeneous reaction. The apparent activation energy was found to be 73.3 kJ mol^?1 for the formation of benzyl acetate.     

Kinetics studies of ketazine formation: Effect of temperature and catalyst concentration

Formation of methyl ethyl ketazine is a distinct case of homogeneous catalyzed gas–liquid–liquid reactions. Kinetics studies of methyl ethyl ketazine formation has been carried out in a semi‐batch reactor. The effects of temperature and catalyst concentration on the percentage yield of ketazine have been studied extensively. The yield of ketazine is found to increase with increase in temperature and then levels off. Increase in catalyst concentration favours the formation of ketazine. The conversion of peroxide is found to increase with increase in temperature thus indicating that chemical reaction is rate‐limiting step in the system. The desired temperature for carrying out the reaction is found to be 60°C and the required catalyst to peroxide ratio is 2.5. The activation energy for the reaction is 24.5 kJ/mol.     

001×7（732）阳离子交换树脂催化醋酸甲酯 水解反应过程模拟与优化

在充分搅拌和可忽略粒度影响条件下，测定了间歇搅拌反应釜中001×7（732）阳离子交换树脂催化醋酸甲酯水解反应动力学数据，建立了其拟均相与非均相反应动力学模型，进行了模型筛选和参数估值。结果表明，醋酸甲酯与水均吸附，表面反应为控制步骤的非均相反应动力学模型能较好地拟合实验数据，并满足统计检验。根据优选的反应动力学模型，对醋酸甲酯水解过程进行了模拟计算，考察了反应温度、树脂浓度、水酯摩尔比对水解过程的影响，得到的优化反应条件为：反应温度55℃、树脂浓度260 g·L^-1、水酯摩尔比1.5∶1。此时反应90 min接近醋酸甲酯平衡水解率34.8%。     

Liquid phase synthesis of methyl tert-butyl ether catalyzed by ion exchange resin

Synthesis of methyl tertiary butyl ether (MTBE) from methanol and isobutene was studied using macroporous cation exchange resin, Amberlyst 15 in the hydrogen form, as a catalyst in the temperature range of 313-328 K. The reaction was carried out in a batch reactor at a pressure of one atmosphere in the liquid phase. A high degree of agitation was maintained in order to eliminate film diffusion resistance. The effect of catalyst loading, catalyst particle size and reaction temperature on reaction rate were studied. The reaction rate increased with increase in catalyst concentration and reaction temperature. Resin particle size had virtually no effect on the rate under the experimental conditions. The reaction rate data were analysed using homogeneous kinetics and heterogeneous models based upon Langmuir-Hinshelwood rate expressions. The apparent activation energies using homogeneous and heterogeneous models were determined and found as 79.0 kJ/mol and 76.7 kJ/mol respectively.     

无皂乳液制备PMMA动力学及其模型

以甲基丙烯酸甲酯(MMA)为单体、过硫酸钾(KPS)为引发剂进行无皂乳液聚合反应,考察了单体MMA浓度、引发剂KPS用量及聚合温度对其动力学行为的影响。建立了转化率-时间关系曲线的模型函数———Gamm a积分函数,用它拟合了转化率-时间关系曲线,获得了聚合过程的重要特征参数,如平均成核速率,聚合最大速率和平稳期平均聚合速率及成核结束和聚合进入完成期对应的转化率。同时对聚合速率与以上各聚合参数的关系数据进行了非线性拟合,得到了它们之间的关系式。拟合相关系数非常接近于1,平均拟合误差很小,成核结束时转化率在15%以内,聚合速率随以上参数增大而增大,反应温度在聚合过程中起决定作用。     

Kinetics of the liquid phase esterification of acrylic acid with butanol catalysed by cation exchange resin

Esterification of butyl alcohol with acrylic acid catalysed by Amberlyst-15 cation exchange resin was carried out in a batch reactor in the liquid phase in the temperature range 333 to 364 K and 1 atm. The reaction rate increased with an increase in catalyst concentration and decreased with an increase in water concentration. The rate data were correlated with a kinetic model based on inhibition by water. The apparent activation energy was found to be 59.5 kJ mol^?1 for the formation of butyl acrylate.     

Synthesis of monoterpene esters by alcoholysis reaction with Mucor miehei lipase in a solvent-free system

The syntheses of geranyl acetate and citronellyl acetate by alcoholysis reaction catalyzed by immobilized lipase from Mucor miehei was studied for the first time in a solvent-free system. Reactions were carried out at a terpene alcohol/acyl donor molar ratio of 1:5 with Lipozyme at 10% of the total weight of the reactants in a solvent-free system. Incubations were carried out at 55 to 60°C for ethyl and butyl acetates as acyl donors, whereas for methyl acetate the incubation temperature was 40 to 45°C. Excess concentration of acyl donor increases the percentage of geranyl acetate and citronellyl acetate, while excess of terpene alcohol concentration decreases the same. Yields from 75 to 77% molar conversion (90 to 98% conversion, w/w) were obtained after 8 to 28 h of reaction time.     

强酸性树脂催化合成醋酸甲酯动力学

在釜式反应器中研究了Amberlyst-15强酸性离子交换树脂催化合成醋酸甲酯的反应动力学,考察了搅拌速度、反应温度、催化剂用量等影响因素。结果表明,随着温度的升高,反应速率增大,而反应平衡常数减小;催化剂用量与反应速率常数基本成正比关系。分析并计算得到了酯化反应的动力学参数,建立了反应动力学方程。     

Glycerolysis of Fatty Acid Methyl Esters: 1. Investigations in a Batch Reactor

The present work focused on the glycerolysis of fatty acid methyl esters. The aim was to develop and test a kinetic model that could be used to reliably simulate different process alternatives for this reaction. A prerequisite was the identification and characterization of the factors that affect the reaction kinetics. Experiments were carried out in a batch reactor with and without forced removal of methanol, which is one of the reaction products. Concentrations of all components in the two-phase system were measured. It was found that the methanol concentration has a strong effect on the reaction rate and equilibrium conversion. Near-complete conversions were obtained by stripping methanol with an inert gas. The glycerol concentration in the ester phase was found to increase as the reaction proceeds, which also accelerates the reaction. Effects of mass transfer on the reaction rate were not found to control the reaction rate under well-agitated conditions. A semi-empirical model was used to simulate the reaction. The results from the semi-empirical model show good agreement with experimental results.