Article

Reactive Distillation: An Attractive Alternative for the Synthesis of Unsaturated Polyester

Macromolecular Symposia 04/2011; 302(1):46 - 55. DOI: 10.1002/masy.201000048

ABSTRACT Unsaturated polyester is traditionally produced in a batch wise operating reaction vessel connected to a distillation unit. An attractive alternative for the synthesis of unsaturated polyester is a reactive distillation. To value such alternative synthesis route reliable process models need to be developed. In this paper, the strategy is described for the development of the reactive distillation model. Essential parts of the reactive distillation model are kinetic and thermodynamic which are subsequently validated with the experimental data of the traditional batch process such as acid value of the polyester, weight of the distillate and glycol concentration in the distillate. We find that the models predict these important variables reliably. Unsaturated polyester production time is around 12 hours in the traditional batch process. However, the simulation study of the reactive distillation process shows that the total production time of unsaturated polyester in a continuous reactive distillation system is between 1.5 hours to 2 hours for the same product quality as during batch production. The equilibrium conversion is raised by 7% compared to the traditional batch process. The model demonstrated that reactive distillation has the potential to intensify the process by factor of 6 to 8 in comparison to the batch reactor.

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    • "The simulation results of the batch reactor model such as compositions of the liquid and vapor phase, fractions of isomerized and saturated polyester in the end product compositions, the molecular weight number of the polyester were compared with the experimental results of the batch reactor. We concluded in our earlier work (Shah et al., 2011a, 2011b) that the kinetic and thermodynamic models and their parameters describe the process reliably and therefore they can be used for the evaluation of reactive distillation processes. "
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    ABSTRACT: The state of the art equilibrium model and the rate-based models for reactive distillation (RD) are very well known and have been used since a couple of decades. However, these models are not sufficient to accurately represent a slow reaction process that is kinetically controlled. The shortcoming is due to neglecting the effect of liquid back mixing (LBM) on the whole process. This work presents a review of the available modeling approaches for RD, then discusses the applicability of various models and finally, it applies the findings to an industrially relevant case study—polyester synthesis. The main focus is on extending the dynamic rate-based model to take into account the liquid back mixing. We also show how the axial dispersion can be introduced into the RD model, without adopting the axial dispersion model. The comparison of the results of the rate-based model, with and without axial dispersion, clearly demonstrates that the extended model predicts more accurately the kinetically controlled process as compared to the conventional rate-based model.
    Chemical Engineering Science 10/2011; 68(1). DOI:10.1016/j.ces.2011.09.027 · 2.61 Impact Factor
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    • "The simulation results of the batch reactor model such as compositions of the liquid and vapor phase, fractions of isomerized and saturated polyester in the end product compositions, the molecular weight number of the polyester were compared with the experimental results of the batch reactor. We concluded in our earlier work (Shah et al., 2011a, 2011b) that the kinetic and thermodynamic models and their parameters describe the process reliably and therefore they can be used for the evaluation of reactive distillation processes. "
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    ABSTRACT: The state of the art equilibrium model and the rate-based models for reactive distillation (RD) are well known and have been used since a couple of decades. However, these models are not sufficient to represent a slow reaction process that is kinetically controlled. This shortcoming is due to neglecting the effect of liquid back mixing on the whole process. This work starts with reviewing the modeling approach for the RD and then discusses the applicability of various models. The main focus is on the extension of the dynamic rate-based model to take into account the liquid back mixing. We also show how the axial dispersion is introduced into the RD model, without adopting the axial dispersion model. The results of the rate-based model were compared, with and without the axial dispersion. Remarkably, the extended model predicts more accurately the kinetically controlled process, as compared to the conventional rate-based model.
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    ABSTRACT: This study presents a novel design methodology for the feasibility and technical evaluation of reactive distillation (RD), and discusses the applicability of various design methods of RD. The proposed framework for the feasibility evaluation determines the boundary conditions (e.g. relative volatilities, target purities, equilibrium conversion and equipment restriction), checks the integrated process constraints, evaluates the feasibility and provides guidelines to any potential RD process application. Providing that a RD process is indeed feasible, a technical evaluation is performed afterward in order to determine the technical feasibility, the process limitations, working regime and requirements for internals as well as the models needed for RD. This approach is based on dimensionless numbers such as Damkohler and Hatta numbers, as well as the kinetic, thermodynamic and mass transfer limits. The proposed framework for feasibility and technical evaluation of reactive distillation allows a quick and easy feasibility analysis for a wide range of chemical processes. In this work, several industrial relevant case studies – e.g. synthesis of di-methyl carbonate (DMC), methyl acetate hydrolysis, toluene hydro-dealkylation (HDA) process, fatty acid methyl esters (FAME) process and unsaturated polyesters synthesis – clearly illustrate the validity of the proposed framework.
    Chemical Engineering and Processing 10/2012; 60:55-64. DOI:10.1016/j.cep.2012.05.007 · 1.96 Impact Factor