Synthesis of tertiary amyl methyl ether (TAME): Influence of internal and external mass transfer resistance

An experimental set-up is presented for the measurement of reaction rates in the liquid phase synthesis of tertiary amyl methyl ether (TAME) from methanol and a mixture of 2-methyl-1-butene and 2-methyl-2-butene using an acidic ion exchange resin (Lewatit SPC 118) as catalyst. The reaction was performed in a continuous-flow recycle reactor at a temperature of 333.15 K and a pressure of 1.6 MPa. Determination of the age distribution (Fcurve) of the reactor showed that mixed flow is approached at a recycle ratio of R = 10. Experiments were performed to reveal the limits of operating conditions where the various resistances do not affect the rate. In agreement with estimation of Reynolds numbers, hindrance by external mass transfer can be excluded at a volumetric flow rate of 10 ml/min and a recycle ratio of R = 10. The maximum temperature increase of the whole particle resulting from limitation of external heat transfer was estimated to be about 3 K. Variation of the size of resin particles revealed the existence of a critical methanol concentration, above which reaction rates can be determined without influence of internal mass transport phenomena. The maximum temperature increase in the particle was estimated to be 0.3 K.     

Skeletal isomerization kinetics of 1-pentene over an HZSM-22 catalyst

Synthesis of the oxygenate fuel additive TAME (tertiary amyl methyl ether) is based on the reaction between reactive isopentene compounds (2-methyl-1-butene and 2-methyl-2-butene) and methanol. Skeletal isomerization of n-pentenes is an important reaction route in production of the raw material for TAME synthesis. In this work the kinetics of skeletal isomerization of 1-pentene was studied using HZSM-22 as a catalyst, and the effect of temperature (523–598 K) and WHSV (weight hourly space velocity) on product composition were investigated. The observed main reaction products were cis- and trans-2-pentenes, 2-methyl-2-butene, 2-methyl-1-butene and 3-methyl-1-butene. Minor products found in the output stream were C₂, C₃, C₄, C₆, C₇, C₈ and C₁₀ – alkenes and – alkanes. Only traces of methane and C₉ compounds were detected. Two different reaction mechanisms have been proposed in literature for skeletal isomerization of n-pentenes and their side reactions (dimerization and fragmentation); the monomolecular and the bimolecular skeletal isomerization mechanisms. In the current work a pseudohomogeneous reaction model for both mechanisms is fitted to experimental data. The fitting results show that both reaction mechanisms explain the skeletal isomerization of 1-pentene to isopentenes well. However, the monomolecular reaction mechanism explained the formation of dimerization and fragmentation products slightly better. The reliability of the estimated Arrhenius parameters was analyzed using Bayesian inference and Markov chain Monte Carlo methods (MCMC) which are rarely used in chemical engineering.     

Equilibrium of the simultaneous etherification of isobutene and isoamylenes with ethanol in liquid-phase

The simultaneous etherification of isobutene and isoamylenes with ethanol has been studied using macroreticular acid ion-exchange resins as catalyst. Most of the experiments were carried out over Amberlyst-35. In addition, Amberlyst-15 and Purolite CT-275 were also tested. Chemical equilibrium of four chemical reactions was studied: ethyl tert-butyl ether formation, tert-amyl ethyl ether formation from isoamylenes (2-methyl-1-butene and 2-methyl-2-butene) and isomerization reaction between both isoamylenes. Equilibrium data were obtained in a batchwise stirred tank reactor operated at 2.0 MPa and within the temperature range from 323 to 353 K. Experimental molar standard enthalpy and entropy changes of reaction were determined for each reaction. From these data, the molar enthalpy change of formation of ethyl tert-butyl ether and tert-amyl ethyl ether were estimated. Besides, the chemical equilibrium between both diisobutene dimers, 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, was evaluated. A good agreement between thermodynamic results for the simultaneous etherification carried out in this work and those obtained for the isolated ethyl tert-butyl ether and tert-amyl ethyl ether systems was obtained.     

Structure of the phase diagram of the 2-methyl-1,3-butadiene–2-methyl-2-butene–acetonitrile–water system

The structure of the liquid–liquid–vapor diagram of the industrially important four-component system 2-methyl-1,3-butadiene–2-methyl-2-butene–acetonitrile–water has been determined. A model of the phase equilibrium has been derived from experimental data. The evolution of the three-phase immiscibility region in the concentration simplex has been investigated.     

液相法甲醇合成的平衡收率

对液相法甲醇合成系统进行了热力学分析，建立了求解该系统相平衡和化学平衡问题的非线性方程组。在此基础上，分别对以四甘醇二甲醚和角鲨烷为液相介质的反应热力学平衡进行了计算，结果表明液相介质具有提高甲醇平衡收率的作用。研究了液相介质的性能、用量、温度、压力及原料气组成对甲醇平衡收率的影响。     

尿素醇解法合成氨基甲酸甲酯平衡常数的测定

文章测定了尿素醇解法合成氨基甲酸甲酯的平衡常数。在433.15K时,无催化剂条件下,甲醇和尿素在高压釜内反应生成氨基甲酸甲酯,待反应达到平衡后,通过气相色谱仪和液相色谱仪测定平衡混合物的组成来计算反应的平衡常数。气相可近似认为是氨气和甲醇组成的二元混合物,液相近似认为是尿素、甲醇和氨基甲酸甲酯组成的三元混合物。实验结果表明,实验重现性较好,平衡常数数值是可靠的。     

Comparison of the Various Kinetic Models of TAME Formation by Simulation and Parameter Estimation

Various kinetic models proposed for the synthesis of TAME (tert-amyl methyl ether, 2-methoxy-2-methylbutane) were tested against experimental batch reactor data. The experiments were carried out with methanol/isoamylenes molar ratios varying from 0.2 to 2.0 at temperatures between 333 and 353 K. The range of validity of the various models was evaluated by simulating the experimental conditions and by comparing the adequacy of the models to predict the experimental changes of composition as a function of the catalyst contact time and composition at reaction equilibrium. Activity-based models were found to predict the experimental results better within a wider range of conditions than the concentration-based models. The activity-based models were additionally compared by estimating the values for the model parameters from the experimental data.     

液相法甲醇合成过程中机械搅拌反应器的模拟

本文对C301及C302两种不同催化剂条件下机械搅拌反应器内液相法甲醇过程进行了模拟,模拟中节气液之间的传质过程及催化剂气固相本征反应动力学,主要模拟条件：温度483K－528K,压力2．0MPa-6．0MPa,原料气中CO浓度0．06－0．45。模拟结果表明,在C301与C302催化剂条件,隆成总体速率的模拟计算与实测值相吻合,平均偏差分别为7．98％和11．92％,可以认为,气固相本征动力学模型应用于液相甲醇合成过程的工程设计与过程分析是适用和可靠的。     

生物质气催化合成甲醇的热力学分析

由生物质气合成甲醇是一复杂反应系统,本文计算了其中各个反应的反应热和平衡常数与温度的关系.并以CO 21.5%、CO₂ 22.8%、H₂ 52.5%、N₂ 3.2%的气体模拟生物质气,用平衡常数法计算了在473.15～553.15 K、3～6 MPa下的平衡组成、碳的平衡转化率和所得甲醇的浓度.计算结果表明,这一体系中,主要是CO+H₂生成甲醇.低温和高压有利于提高碳的平衡转化率和甲醇的浓度.并用工业C306催化剂验证了上述规律的正确性.由于反应既受热力学控制,又受动力学控制,在3 MPa时碳的转化率在533.15 K时达到最大,接近平衡转化率.随压力升高,甲醇产率及液相产物中的浓度逐渐升高.     

Selective Synthesis of 1-butene through Positional Isomerisation of 2-butene over Mesoporous Silica MCM-41

A highly selective and active catalyst for the positional isomerisation of 2-butene into 1-butene has been developed by using a mesoporous silica, MCM-41. The yields of 1-butene as well as total conversion decrease when aluminium or lanthanum was added to the MCM-41 even though the amounts of acid sites increase. FT-IR spectra proved that the H site due to the silanol group may act as an active site for the positional isomerisation of 2-butene to 1-butene.     

Liquid phase methanol and dimethyl ether synthesis from syngas

The Liquid Phase Methanol Synthesis (LPMeOH^TM) process has been investigated in our laboratories since 1982The reaction chemistry of liquid phase methanol synthesis over commercial Cu/ZnO/Al₂O₃ catalysts, established for diverse feed gas conditions including H₂-rich, CO-rich, CO₂-rich, and CO-free environments, is predominantly based on the CO₂ hydrogenation reaction and the forward water-gas shift reactionImportant aspects of the liquid phase methanol synthesis investigated in this in-depth study include global kinetic rate expressions, external mass transfer mechanisms and rates, correlation for the overall gas-to-liquid mass transfer rate coefficient, computation of the multicomponent phase equilibrium and prediction of the ultimate and isolated chemical equilibrium compositions, thermal stability analysis of the liquid phase methanol synthesis reactor, investigation of pore diffusion in the methanol catalyst, and elucidation of catalyst deactivation/regenerationThese studies were conducted in a mechanically agitated slurry reactor as well as in a liquid entrained reactorA novel liquid phase process for co-production of dimethyl ether (DME) and methanol has also been developedThe process is based on dual-catalytic synthesis in a single reactor stage, where the methanol synthesis and water gas shift reactions takes place over Cu/ZnO/Al₂O₃ catalysts and the in-situ methanol dehydration reaction takes place over -Al₂O₃ catalystCo-production of DME and methanol can increase the single-stage reactor productivity by as much as 80%. By varying the mass ratios of methanol synthesis catalyst to methanol dehydration catalyst, it is possible to co-produce DME and methanol in any fixed proportion, from 5% DME to 95% DMEAlso, dual catalysts exhibit higher activity, and more importantly these activities are sustained for a longer catalyst on-stream life by alleviating catalyst deactivation.     

绿色有机电致发光材料C545T合成工艺研究

研究了绿色有机电致发光材料C545T的合成工艺。以价格较便宜的1-溴-3-甲基-2-丁烯代替1-氯-3-甲基-2-丁烯,降低了原料价格,提高了产品收率;其次,中间体2-苯并噻唑乙酸乙酯的合成采用微波法代替传统的加热反应法,缩短了反应时间,提高了产品收率;另外,最后一步的Knovenagel反应采用有机碱哌啶作催化剂,也缩短了反应时间,提高了产品收率。该合成工艺生产周期短,反应条件温和,纯化过程简单,合成成本低,六步合成总收率达8.2%,产品纯度达99.9%。     

三相床甲醇合成过程中组分在液体石蜡中溶解度的测定

采采气体物理吸收技术与静态总压蒸汽法分别测定了甲醇合成过程中反应组分Ｈ２、ＣＯ、ＣＯ２及产物甲醇、水在医用液体石蜡中的溶解度。实验结果表明：随温度增加，Ｈ２、ＣＯ的溶解度增加，而其他组分的溶解度均降低，在本文的实验范围内，Ｈ２、ＣＯ、ＣＯ２等组分的溶解特性基本符合亨利定律：甲醇和水不满足亨利定律；随温度增加，甲醇的活度系数降低，由实验数据回归得到了各组分的溶解度与平衡压力及温度的关联式，各关联式的计算值与实验值吻合良好。     

Etherification of C5- and C8-Alkenes with C1- to C4-Alcohols

Etherification of two alkenes, 2-methyl-1-butene and 2,4,4-trimethyl-1-pentene, was studied with seven different C₁- to C₄-alcohols. Although etherification was of primary interest, the isomerisation of the alkenes was the main reaction to occur. For the primary alcohols the etherification and isomerisation rates correlated well with the properties of the alcohols. Both rates increased with decreasing polarity and with increasing carbon number, acidity and Mulliken charge of the oxygen atom of the alcohol. It is difficult to distinguish the effect of each property separately, and probably the differences in the reactivities are not due to any one property alone but rather the synergy of the properties affects the reactivities. The secondary alcohols behaved in a different way than the primary ones: the etherification was almost negligible. The effect of alcohol on the isomerisation of alkenes was notable even though alcohol does not directly react in the reaction, which was concluded to be due to the stronger adsorption of the more polar alcohols which hinders the reactions of other components.     

Etherification of dimethylbutenes in excess methanol

Oxygenated compounds such as ethers produced by the reaction of alcohols and alkenes have good potential for use as performance and environmental enhancing additives for transportation fuels. In this study, the production of the C₇ ether, 2,3-dimethyl-2-methoxybutane (DM2MB), was investigated in a batch reactor from 323–343 K at high methanol concentrations. A macroporous cation exchange resin, Amberlyst 15, was employed as catalyst for the etherification of 2,3-dimethyl-1-butene (DM1B) and 2,3-dimethyl-2-butene (DM2B) with methanol. Kinetic rate constants were correlated by fitting the experimental data to kinetic equations based on a pseudo-homogeneous model. Experimental results were obtained for the effects of temperature on simultaneous etherification and isomerization of DM1B and DM2B and differences in the reactivities of the two alkenes were noted. Kinetic and equilibrium parameters obtained from the Arrhenius and Van't Hoff equations agreed well with values obtained from similar studies in the literature.     

基于四甲基久洛尼定为原料的香豆素衍生物的合成

以间氨基苯酚和溴代异戊烯为起始原料经过亲核取代制备了N,N-二(3-甲基-2-丁烯)-3-羟基苯胺氢溴酸盐,通过亲电取代关环合成了8-羟基-1,1,7,7-四甲基久洛尼定,再经Vilsmeir-Haack反应引入醛基获得了9-甲酰基-8-羟基-1,1,7,7-四甲基久洛尼定,总收率为25.7%。对N,N-二(3-甲基-2-丁烯)-3-羟基苯胺氢溴酸盐的合成进行了工艺探索,结果表明当间氨基苯酚和溴代异戊烯投料比为1:2,CaCO3为缚酸剂时得到的收率较佳。以9-甲酰基-8-羟基-1,1,7,7-四甲基久洛尼定为原料,分别与噻吩乙腈、对溴苯乙腈进行缩合反应制备得到3-芳基香豆素衍生物,对其结构进行了核磁鉴定,并对其紫外光谱进行了测试。     

大豆油与甲醇酯交换反应体系的相平衡研究

生物柴油是一类清洁的可再生液体燃料,精炼植物油与甲醇酯交换是制备生物柴油的重要反应。针对目前难以准确获得酯交换反应体系的多组分相平衡组成等方面存在的问题,研究了间歇反应和连续逆流分离甘油等不同反应方式下大豆油与甲醇酯交换反应体系的多组分相平衡行为,并以三油酸甘油酯与甲醇酯交换为模型反应,采用UNIFAC和Modified UNIFAC模型进行了模拟计算。结果表明,在常压、60^oC反应条件下,在总组成偏离甲醇-甲酯二元组成的区域,UNIFAC和Modified UNIFAC模型准确计算了生物柴油酯交换反应体系的三元和四元相平衡组成。在甘油含量大于2.2%(质量)或转化率小于90%(质量)的酯交换反应中,计算值与实验值的平均偏差约为2%。酯交换反应相平衡的实验值和模型计算值表明,采用连续逆流方式分离甘油可以提高酯相中的甲醇含量,有利于传质和酯交换反应。这些结果为生物柴油工艺过程模拟、设备优化以及新技术开发提供了理论参考。     

Heterogeneous reactive extraction for secondary butyl alcohol liquid phase synthesis: Microkinetics and equilibria

The reaction kinetics for the liquid phase synthesis of a racemic mixture of the secondary butyl alcohols (SBA) from linear butene isomers (1-butene (1B); cis-2-butene (c2B); trans-2-butene (t2B)) and water (W) using a macroporous sulfonic acid ion exchange resin as catalyst were determined experimentally in a multiphase CSTR in the temperature range 39–433 K at 6–8 MPa. This range of pressures is necessary to dissolve butenes in the aqueous phase and to ensure a liquid state of all components. For temperatures higher than 423 K the reaction kinetics for the used catalyst size are influenced by mass transfer resistances within the catalyst matrix. The reaction takes place in the water swollen gel phase of the catalysts microspheres. Due to the large excess of water in the gel phase the compositions in the gel phase, in the macropore fluid, and in the catalyst surrounding aqueous phase are assumed to be identical. According to the literature the reaction is rather catalyzed by hydrated acid protons (specific catalysis) than by polymer-bonded-SO₃H groups (general catalysis). The experimental results can therefore be described sufficiently by a pseudo-homogeneous 3-parameter rate expression in aqueous phase activities. The forward reaction is first-order in butene. The reverse reaction is first-order in secondary butyl alcohol. The activation energy was determined to be 108 kJ/mol. Practically no pressure dependence could be observed for pressures exceeding 6 MPa. The ever-present isomerization of the linear butenes on acid catalysts was found to be remarkably faster than the hydration of butenes to SBA. Therefore, the isomerization is considered to be always in equilibrium during the olefin hydration. The formation of the possible by-product di-sec-butyl ether (DSBE) was never observed to a measurable extent. Simultaneous chemical and phase equilibria were investigated theoretically using the volume translated Peng–Robinson equation of state (VTPR-EoS) in combination with a g^E-mixing rule. Parameters of the used g^E-model were adjusted to experimental ternary liquid–liquid equilibrium (LLE) data.     

Simulation and process integration for tert-amyl-methyl ether (TAME) synthesis

This paper proposes an extended approach to develop a new sustainable process to produce tert-amyl-methyl ether (TAME) using as feedstock enriched C₅ fraction (LCN – light cracking naphtha) from fluid catalytic cracking (FCC). To the best of our knowledge, up to now, different authors developed the separation section without considering all possible options. The main contribution is to bring together for comparison different separation techniques of the given mixture and to develop new configurations for the separation section of the plant. In this respect, pressure swing is combined with liquid–liquid separation. Existing technologies consider methanol (MeOH) separation from reactor effluent only by water extraction, combined with distillation. Conceptual design based on residual curve maps (RCM) analysis, considered in this paper, reveals new possibilities to use pressure swing, eventually combined with liquid–liquid separation. Thus, compared to other results reported in literature, new separation sequences are proposed for TAME synthesis reactor effluent separation, in the frame of an extended and detailed analysis for the whole process.To underline process characteristics, three case studies, with those different configurations are presented and analysed using Aspen HYSYS^® v8.4. Main details are obtained using process simulation, process integration and environmental impact computer tools. In the first case study, classical MeOH separation using water extraction is considered. The second case study is based only on pressure swing distillation to separate the azeotropes between hydrocarbons and methanol. In the third case study, pressure swing distillation is combined with separation based on hydrocarbon–methanol liquid–liquid phase equilibrium. Using process simulation results, setup with Aspen HYSYS^® v8.4, heat integration analysis, performed with SPRINT^® v2.8, is accomplished to exploit energy savings. Environmental impact calculations are performed using WAR algorithm, considering different fuel types for utilities generation. Results show that the elimination of water in separation section and the use of liquid–liquid phase separation ensure lower energy consumption (overall heat recovery in case study 3 is 9.87 MW, compared to 7.47 MW for case study 2) and better environmental performance. Economic indicators calculated with Aspen Process Economic Analyzer^® allow identification of attractive process changes, for the new proposed process configuration.     

Carbon Isotope Separation by Absorptive Distillation

Abstract

The feasibility of separating carbon isotopes by absorptive distillation has been studied for CO absorption by cryogenic solvents. Phase equilibrium, isotopic separation, and mass transfer data were taken between 77.4 and 114.3 K for the following solvents: propane, propylene, 1:1 propane-propylene, 1-butene, isobutane and nitrogen.

Carbon monoxide solubility followed Henry's Law, with a maximum experimental solubility of 6.5 mole per cent. Isotopic separation between CO in the gas and liquid phases using hydrocarbon solvents was several times that for pure CO vapor-liquid equilibrium. The maximum observed isotopic separation factor was 1.029 at 77.4 K with the propane-propylene solvent mixture. Mass transfer measurements yielded calculated HTU's of 2 to 5 cm for a possible separation system.

An attempt has been made to correlate isotopic separation data using Hildebrand's theory of solutions. The differential absorption of isotopic CO species is expressed as a difference in solubility of the isotopic CO molecules. Data for propane, propylene, and 1-butene show approximately the same behavior at varying temperatures.