Design Of Reactive Distillation Processes Research Articles

Kinetic study on hydrolysis of isoamyl DL‐lactate catalyzed by NKC‐9

AbstractThe kinetics for hydrolysis of isoamyl DL‐lactate over cation‐exchange resin NKC‐9 was investigated in this paper, which was the prerequisite for a proper design of reactive distillation processes. The effects of mass transfer resistance, temperature, catalyst dosage, and the molar ratio of water to isoamyl DL‐lactate on conversion of isoamyl DL‐lactate were evaluated. The pseudo‐homogeneous (PH), Eley‐Rideal (ER), and Langmuir‐Hinshelwood (LH) models were then utilized to correlate the data obtained from experiments. Activities were used in the kinetics instead of the mole fractions because the reactants and products were not ideal. The activity coefficients were estimated by UNIFAC. It was demonstrated that the PH model was the best one to describe the hydrolysis of isoamyl DL‐lactate. The standard enthalpy was 5.46 kJ · mol−1 and the activation energy was 59.71 kJ · mol−1. Finally, the thermal stability and reusability of NKC‐9 were also tested.

Effect of boiling point rankings and feed locations on the applicability of reactive distillation to quaternary systems

Reactive distillation (RD) offers major benefits such as costs reduction and energy saving, but the understanding and design of RD processes usually demand complex tasks that include extensive studies and rigorous simulations. To reduce this complexity and the time required, this study applies a novel mapping method to quickly provide insights into the RD applicability to reversible quaternary systems (A + B ⇌ C + D). Generic cases are used to produce applicability graphs (i.e. plots of reflux ratio vs number of theoretical stages) and multiple RD column configurations. The systems are assumed to have ideal properties and fixed key parameters (i.e. relative volatilities and chemical equilibrium constants). This study focuses on quaternary reactions considering different boiling point rankings and feed locations. Using the mapping method, quick results are achievable regarding the preliminary economic ranking of RD processes and the optimal feed locations with reduced energy requirement (i.e. lower reflux ratio). Ultimately, this study provides a much better understanding of the effect of boiling point orders and feed locations on the RD applicability and conceptual design, being a valuable tool in early techno-economic evaluations.

Design of reactive distillation processes for the production of butyl acrylate: Impact of bio-based raw materials

The chemical industry is nowadays predominantly using fossil raw materials, but the alternative use of bio-based resources is investigated to account for the foreseeable scarcity of fossil feedstocks. A main challenge of using bio-based feedstocks is the complexity of the impurity profile. For an economic production of bio-based chemicals, the use of intensified processes is inevitable and approaches are needed for the various process intensification techniques to identify their applicability to be used for the production of bio-based components. In the presented study, an approach is shown for the reactive distillation (RD) technology to identify the most critical bio-based impurities and their impact on the reactive distillation process. The investigated case-study is the production of n-butyl acrylate from acrylic acid and n-butanol. Among all initially identified impurities, the key impurities, having the biggest impact on the product purity in the reactive distillation process, are found. These impurities are then studied in more detail and an operating window depending on the impurity concentration is identified for the reactive distillation column. Furthermore, an integrated design of upstream and downstream processes is facilitated, as the presented results can be used in the development of the fermentation processes for the production of the bio-based reactants by decreasing the concentration of the critical impurities.

Phase equilibria and excess properties for binary systems in reactive distillation processes. Part II. Ethyl acetate synthesis

In this investigation isothermal vapor–liquid equilibrium data (VLE) and excess enthalpy (HE) data were measured for the binary systems required for the design of reactive distillation processes for the ethyl acetate production. The isothermal P–x data was measured with a static apparatus, the heat of mixing measurements were performed with a commercial isothermal flow calorimeter. To the experimental data from this work and mixture data from other authors temperature dependent UNIQUAC parameters were fitted.

A Framework for Application of Genetic Algorithm to Model-Based Design of Reactive Distillation Process

A Framework for Application of Genetic Algorithm to Model-Based Design of Reactive Distillation Process

Modelling of homogeneously catalysed reactive distillation processes in packed columns: Experimental model validation

The design of reactive distillation processes requires reliable and accurate models to significantly decrease the expensive and time consuming experimental work. Different modelling approaches of varying complexity are available in the open literature. However, only few publications exist in which the question of the optimal modelling depth is discussed for homogeneously catalysed processes. Unlike these publications, we used experimental data in the present study to compare them with simulation results using different modelling depths for homogeneous reactive distillation processes. The nonequilibrium-stage model using the Maxwell–Stefan equations, the nonequilibrium-stage model using effective diffusion coefficients, the equilibrium-stage model including reaction kinetics, and the equilibrium-stage model assuming chemical equilibrium were investigated. The homogeneously catalysed transesterification of dimethyl carbonate with ethanol, for which pilot-scale experimental data were available, was used as a test system.

Feasibility analysis, synthesis, and design of reactive distillation processes: A focus on double‐feed processes

AbstractA new approach for the feasibility analysis of reactive distillation processes based on the reactive extractive curve maps (rExCM) concept is introduced. A method dedicated to reactive distillation feasibility analysis, and design has been developed in our team since 1999. From minimal information concerning the physicochemical properties of the system, three steps lead to the design of the unit and the specification of its operating conditions. Currently, the procedure permits the conceptual design of hybrid reactive column configuration with one or two feed plates, for any number of equilibrium reactions (provided that the degree of freedom of the system is equal to 2) occurring in liquid or vapor phase. This contribution focuses on the most recent developments: the generalization of the feasibility analysis step to double‐feed processes thanks to the introduction of the rExCM concept. This methodology is illustrated through two examples: the emblematic methyl acetate example and the production of dimethyl methyl glutarate. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2346–2356, 2012

New design of reactive distillation processes

A technological design of reactive distillation processes (catalytic distillation) is discussed that applies liquid-flooded catalytic zones with a cocurrent-cross flow of the liquid, into each of which only a portion of the vapor stream is passed from the zone located below. This allows the cross section of the catalytic zones to be multiply reduced and the local excessive heating in them to be completely eliminated.

Optimal steady-state design of reactive distillation processes using simulated annealing

In this paper, we investigate on a derivative-free optimization approach, simulated annealing (SA), for the optimization of the reactive distillation (RD) column design. Because RD systems exhibit non-monotonic behavior for key design variables, flowsheet optimization using simulator is difficult when derivative-based approach is employed. The SA-based optimization procedure gives an equally good or better design than the optimal flowsheet obtained from the sequential design approach. More importantly, this is achieved with much more efficient computing.

Computer aided design of reactive distillation processes for the treatment of waste waters polluted with acetic acid

A theoretical study of reactive distillation processes to remove acetic acid from its 30 wt% aqueous solution by esterification with n-butanol is presented. Two different column structures were identified rendering theoretically close to 100 percent conversion of acetic acid. A model capable of precisely predicting the potential phase split is used. Total costs for the new processes are estimated and compared with estimated costs of nonreactive separation process. It is shown that more than 56 percent costs can be reduced by using the new processes. The dynamic behavior of both the processes are studied through a series of dynamic simulation runs.

Dynamics of reaction separation processes in the limit of chemical equilibrium

AbstractA new approach for analyzing and understanding the dynamics of combined reaction separation processes with fast chemical reactions was proposed recently. The approach is based on transformed concentration variables which were first introduced by Doherty and co‐workers for the steady‐state design of reactive distillation processes. Application was demonstrated for reactive distillation processes and fixed bed, as well as moving‐bed chromatographic reactors. The focus was on simple reactions of type 2A ⇋ B + C. This approach is further extended and applied to some real—fairly complex—multireaction systems. Applications to be considered are a reactive enantiomeric separation process in a fixed‐bed chromatographic reactor, and an industrial reactive distillation column. Finally, application to membrane reactors is discussed. © 2005 American Institute of Chemical Engineers AIChE J, 2006

Equilibrium theory and nonlinear waves for reactive distillation columns and chromatographic reactors

A general framework for analyzing and understanding the dynamics of reactive separation processes is developed. The theory is based on the assumption of simultaneous phase and reaction equilibrium. It makes use of transformed concentration variables, which were first introduced by Doherty and co-workers for the steady state design of reactive distillation processes (Proc. Roy. Soc. London A 413 (1987a) 459). It is shown that these transformed variables can be directly generalized to the dynamic problem considered here. Further, they can also be applied to other reactive separation processes like fixed bed as well as countercurrent chromatographic reactors, for example. They provide profound insight into the dynamic behavior of these processes and reveal bounds of feasible operation caused by reactive azeotropy. It is shown that reactive azeotropy, which is a well-known phenomenon in reactive distillation (Proc. Roy. Soc. London A 413 (1987b) 443) may also rise under very similar conditions in other reactive separation processes like chromatographic reactors for example.

State-of-the-Art and Future Challenges in Design of Reactive Distillation Processes

State-of-the-Art and Future Challenges in Design of Reactive Distillation Processes

Phase equilibria and excess properties for binary systems in reactive distillation processes: Part I. Methyl acetate synthesis

Isothermal vapor–liquid equilibrium (VLE) and excess enthalpy ( H E) data were measured for binary systems required for the design of reactive distillation processes for the methyl acetate production. The isothermal P– x data were measured with the help of a computer-operated static apparatus. A commercial isothermal flow calorimeter was used for the determination of the heats of mixing. Temperature-dependent interaction parameters for the UNIQUAC model were fitted simultaneously to the experimental data from this work and other authors.

Reaction Kinetics and Reactive Distillation - On the Transfer of Kinetic Data from a Batch Reactor to a Trickle-bed Reactor

The design of reactive distillation processes requires besides the knowledge of phase equilibrium data reliable kinetic data. This paper presents the results of kinetic measurements of acetic acid esterification with methanol together with results for the backward reaction, the hydrolysis of methyl acetate, both catalyzed by the macroreticular, strongly acidic ion-exchange resin Amberlyst 15. Microkinetic parameters are determined from batch experiments in a thermostated stirred tank reactor. The applicability of the derived kinetics is checked against experimental results obtained in a trickle-bed reactor. While the trickle-bed reactor can be modeled qualitatively using the microkinetic parameters, some macrokinetic phenomena occur (likely selective swelling of the polymeric matrix of the catalyst). To improve the applicability of the kinetic model, swelling phenomena are currently being investigated.

Reactive Distillation Processes

Reactive distillation, i.e. the simultaneous implementation of reaction and distillation in a counter currently operated column, ia a promising alternative to the common sequential processes. In a preceding paper the effective phase equilibrium of a reactive distillation has been studied with a special focus on the determination of so-called reactive azeotropes. In this contribution knowledge of these thermodynamic fundamentals is applied to the conceptual design of reactive distillation processes. Furthermore, some process examples of technical importance are presented.

Prozesse der Reaktivdestillation

AbstractReactive Distillation Processes Reactive distillation, i.e. the simultaneous implementation of reaction and distillation in a counter–current column, is a promising alternative to the conventional sequential processes. In a preceding paper the effective phase equilibrium of a reactive distillation was studied with a special focus on the determination of so–called reactive azeotropes. In this contribution, a knowledge of these thermodynamic fundamentals is applied to the conceptual design of reactive distillation processes. Furthermore, some process examples of technically important processes are presented.