Production Of Ethyl Tert-butyl Ether Research Articles

Design of intensified chemical processes for the production of ethyl tert-butyl ether

Process intensification contributes to the design of processes with better sustainability performance by allowing several tasks to be performed within the same equipment unit, for instance, reaction and separation. This work aims at the design of intensified processes using a phenomena-based methodology. A gradual intensification approach is used, and each structure is evaluated from economic and environmental considerations. A production process of ethyl tert-butyl ether (ETBE) was selected as a base flowsheet to be intensified. The process consists of one reactor and three conventional distillation columns. Three intensified process alternatives are developed, which employ technologies such as reactive distillation column (RDC), dividing wall column (DWC), and reactive dividing wall column (RDWC). The fully intensified structure, based on a RDWC, showed the best economic indicator with a total annual cost reduction of 26.7% with respect to the base case process; the partially intensified structures showed similar improvements of 18%. The energy savings offered by the intensified flowsheets provide direct benefits from environmental considerations.

Process design and mechanism analysis of reactive distillation coupled with extractive distillation to produce an environmentally friendly gasoline additive

Ethyl tert-butyl ether is a high-octane gasoline blending component with excellent performance and has important industrial application value. When ethanol and isobutylene react to form ethyl tertiary butyl ether, there is an azeotrope system of ethyl tertiary butyl ether and ethanol. The efficient production of ethyl tert-butyl ether and the precise separation of the ethyl tert-butyl ether/ethanol azeotrope are the keys to the entire process. In this work, reactive extractive distillation process and reactive extractive dividing-wall process were designed to achieve high-quality production and separation of ethyl tert-butyl ether. By analyzing the relative volatility of the solvents and combining molecular dynamics simulation and quantum chemical calculations, ethylene glycol was selected as the extractant for the separation of ethyl tert-butyl ether/ethanol. Based on the total annual cost as the objective function, three different ethyl tert-butyl ether production and separation processes were optimized and obtained the best process parameters. Finally, the whole process was analyzed from the aspects of economy, environment and exergy loss efficiency. Compared with common process, the total annual cost of reactive extractive dividing-wall process was reduced by 14.56%. The global warming potential, acidification potential and abiotic depletion potential of the reactive extractive dividing-wall process were 28.38%, 29.03%, and 28.36% lower than those of common process respectively. The exergy loss efficiency of reactive extractive dividing-wall process was reduced by 10.9%. The results showed that reactive extractive dividing-wall process has obvious economic advantages and environmental benefits and the actual production of ethyl tert-butyl ether and the separation of ethyl tert-butyl ether/ethanol azeotrope system have certain guiding significance.

Optimal synthesis and design of catalytic distillation columns: A rate-based modeling approach

This work presents the optimal synthesis and design of a rigorous catalytic distillation (CD) column that explicitly considers the multiscale and multiphase nature of this intensification process. A rate-based model that couples micro and macroscale events taking place inside the CD column is explicitly considered. The direct solution of such intensive optimization problems is challenging due to nonlinearities introduced by heterogeneous reactions, transport phenomena, and interactions between discrete and continuous variables. Also, combinatorial complexity involved in the selection of multiple structural decisions complicates the problem, e.g., distribution of reactive stages along the column, location of feed stages, and total number of stages. A discrete-steepest descent-based optimization framework recently developed is used to address the optimal synthesis and design of rate-based CD columns. A case study involving the production of ethyl tert-butyl ether (ETBE) has been considered. The results show that the multiscale events occurring in this process intensification (PI) unit cannot be ignored since they produce process designs different from those obtained with an equilibrium-based CD model. The results also show that neglecting multiscale phenomena may result in infeasible CD designs. The outcomes gained through this study illustrate the critical need to systematically consider multiscale and multiphase events in CD columns for the optimal design of realistic, cost-effective, and attractive process intensification (PI) systems.

Optimal design of superstructures for placing units and streams with multiple and ordered available locations. Part II: Rigorous design of catalytic distillation columns

This work addresses the optimal design of catalytic distillation (CD) columns taking into account discrete design variables, i.e., the number of stages and location of feed stages and reactive stages. This optimization problem is challenging due to the combinatorial complexity introduced by these discrete decisions. In this work, the binary variables of the superstructure are expressed as a function of a reduced variable set: the external variables, which allows the use of a local algorithm that solves a series of master and primal sub-problems introduced in our previous study (Part I). The master problem is constructed from the reduced variable set and solved with a Discrete-Steepest Descent Algorithm (D-SDA). The primal sub-problem is a nonlinear programming problem obtained by fixing the binary terms in accordance with the reduced variable set. This strategy avoids finding multiple local minimizers, thus making this methodology more practical and efficient than existing Mixed-Integer Nonlinear Programming (MINLP) local and global optimization solvers. The proposed approach was evaluated on a catalytic column used for the production of ethyl tert-butyl ether (ETBE). It was found that an alternating distribution pattern of the reactive trays, the optimization of the location of feed stages, and the optimization of the total number of trays results in a more cost-effective CD column.

Simultaneous Design and Control of Catalytic Distillation Columns Using Comprehensive Rigorous Dynamic Models

This work addressed the rigorous modeling of catalytic distillation columns by simultaneously considering relevant phenomena such as pressure drop across the column, tray capacity constraints, non-ideal behavior of both liquid and vapor, and the column’s hydrodynamics, yet to be considered in earlier modeling studies for catalytic distillation. The developed model is applied for the simultaneous optimal design and control of catalytic distillation units, taking into account economic and set-point tracking objective functions balanced though a proposed weighting parameter estimation methodology. Results for a column for the production of ethyl tert-butyl ether show the advantages of a more comprehensive model regarding design and control decisions in comparison with previous studies: design specifications were met during the entire time horizon without sacrificing economic profitability.

Comparative study of conventional, reactive-distillation and pervaporation integrated hybrid process for ethyl tert-butyl ether production

Ethyl tert-butyl ether (ETBE) is widely used as an oxygenate additive to gasoline; however, a drawback in the conventional ETBE manufacture is the energy intensive product recovery process, making ETBE expensive. The purification process of ETBE involves the separation of ETBE, mixed C4 hydrocarbons and unreacted ethanol. The unreacted ethanol forms azeotropic mixtures with ETBE that are difficult to separate by distillation. In this work, a comparative study between the conventional process to produce ETBE and two alternative intensified processes is presented by means of process simulation in Aspen Plus. One of the alternative methods for improving the separation and purification section of ETBE is the use of a hybrid distillation-pervaporation process with alcohol-selective membranes, which allows to reach the target ETBE purity (95.2wt%) with a lower energy consumption and at the same time the permeate stream, with a high ethanol content, is recycled back to the reaction section. Alternatively, the production of ETBE by means of reactive distillation is analyzed for the same basis of calculation. The results show that the reactive distillation allows a significant increase in the conversion of the reactants, but in contrast the energy consumption is higher than in the other processes evaluated.

Economic comparison of a reactive distillation-based process with the conventional process for the production of ethyl tert-butyl ether (ETBE)

•Modelling and design of reactive distillation systems.•Economic evaluation of reactive distillation systems.•Comparison of conventional and RD-based processes for the production of ethyl tert-butyl ether.

Equilibrium conversion, selectivity and yield optimization of the simultaneous liquid-phase etherification of isobutene and isoamylenes with ethanol over Amberlyst™ 35

A prospective study on the product distribution at chemical equilibrium for the simultaneous liquid-phase etherification of isobutene and isoamylenes with ethanol over Amberlyst™ 35 is presented. Experiments were performed isothermally in a 200cm3 stirred tank batch reactor operating at 2.0MPa. Initial molar ratios of alcohol/olefins and isobutene/isoamylenes ranged both from 0.5 to 2, and temperature from 323 to 353K. Reactants equilibrium conversion, selectivities and yields toward products were clearly affected by the experimental conditions. Experimental etherification yields have been modeled using the response surface methodology (RSM), combined with the stepwise regression method to include only the statistically significant variables into the model. The multiobjective optimization (MOO) of etherification yields has been carried out numerically, by means of the desirability function approach, and graphically, by using the overlaid contour plots (OCP). Optimal conditions for the simultaneous production of ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE) have been found to be at low temperatures (323 to 337K) and initial molar ratio alcohol/olefins close to 0.9 and isobutene/isoamylenes close to 0.5.

Optimal design of reactive distillation systems: Application to the production of ethyl tert-butyl ether (ETBE)

This work addresses the design of reactive distillation columns to produce ETBE, based on a detailed first-principles model that considers equilibrium and kinetic information, rigorous physical property data, and catalyst deactivation. An evolutionary algorithm is used to generate a sequence of feasible designs with improved characteristics in a sequential solution/optimisation strategy, by specifying the design variables (both integer and continuous) that characterise a particular column configuration. Two classes of optimisation algorithms are compared: genetic algorithms and particle swarm optimisation. The objective function considered is the gross annual profit.The results demonstrate that both algorithms are adequate to solve this design problem. The effect of catalyst deactivation included in the design stage played a determinant role in the optimal column specification. A post-design sensitivity analysis is developed to assess the quality of the solutions obtained, together with the individual effects of each design variable in the optimal configuration identified.

Model Development and Validation of Ethyl tert-Butyl Ether Production Reactors Using Industrial Plant Data

This work considers the development and validation of a first-principles dynamic model for the production of ethyl tert-butyl ether (ETBE) in the presence of the coproducts diisobutene (DIB) and tert-butyl alcohol (TBA). Desulfonation is assumed to be the main deactivation mechanism of the catalyst used, an acidic ion-exchange resin. Operational data from an industrial ETBE production plant, taken over the period of 1 year, were used to estimate both the deactivation and DIB kinetic constant parameters. A data reconciliation strategy was employed to convert the raw data into a consistent data set, representing the most likely process operation data. The parameters estimated were incorporated in a set of detailed mass and energy balances, together with additional kinetic and physical information from the literature, to originate a distributed parameter model capable of accurately describing the operation of two industrial reactors used for the production of ETBE. Model development and validation were perfo...

Synthesis of ethyl tert-butyl ether from tert-butyl alcohol and ethanol on strong acid cation-exchange resins

The etherification between ethanol (EtOH) and tert-butyl alcohol (TBA) in the liquid phase under atmospheric pressure for the production of ethyl tert-butyl ether was studied. Three kinds of strong acid cation-exchange resins, Amberlyst 15 (A-15), S-54 and D-72 in the H + form, were used as the catalysts. The effects of temperature, water inhibition, catalyst loading and the reactants molar ratio on the reaction were investigated. The kinetic parameters, such as the activation energy and inhibition coefficient of water were also compared for the catalysts used. Among the catalysts tested, D-72 shows the highest activity, and S-54 shows the highest selectivity and the lowest effect of water inhibition for the production of ethyl tert-butyl ether.

Production of Ethylene from Hydrous Ethanol on H-ZSM-5 under Mild Conditions

Due to the dramatic rise in the use of ethers as fuel oxygenates, an alternative process for the production of ethyl tert-butyl ether (ETBE) based solely on biomass-derived ethanol feedstock is proposed. The first step in this process is ethanol dehydration on H-ZSM-5 to produce ethylene. Hydrous ethanol is a particularly attractive feedstock for this step since the production of anhydrous ethanol is very energy/cost intensive. In fact, the presence of water in the ethanol feed enhances the steady-state activity and selectivity of H-ZSM-5 catalysts. Reaction kinetic data were collected in a microreactor at temperatures between 413 and 493 K, at ethanol partial pressures of less than 0.7 atm, and at water feed molar ratios of less than 0.25. A sharp initial decline in catalyst activity observed within a few minutes on stream was attributed to the formation of “low-temperature coke” from ethylene oligomerization. Deactivation occurred at a much slower rate after 100 min on stream, allowing near-steady-state...

Pervaporation with Reactive Distillation for the Production of Ethyl tert-Butyl Ether

The combined process of pervaporation with reactive distillation was studied for the production of ethyl tert-butyl ether (ETBE) from ethanol (EtOH) and tert-butyl alcohol (TBA). on an ion-exchange catalyst. An apparatus consisting of a stirred batch reactor, a distillation column, and a pervaporation membrane was used to test this technique. The permeation flux and selectivity of water in the membrane were investigated in water-alcohols system. The etherification was performed in the liquid phase by using a batch reactor. The reactive distillation was examined with and without pervaporation at the boiling point of the reactant mixture under atmospheric pressure. When pervaporation was not conducted, two layers formed in the top products because of a higher concentration of water. However, these phenomena were not observed when pervaporation was added. It was revealed that pervapovation might be effective for removing water from the bottom and that a higher fraction of ETBE could be obtained as a top product.