Reactive Distillation for Methanol Synthesis: Parametric Studies and Optimization Using a Non-polar Solvent

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ORIGINAL RESEARCH PAPER

Reactive Distillation for Methanol Synthesis: Parametric Studies and Optimization Using a Non-polar Solvent Shashwata Ghosh 1 & Srinivas Seethamraju 1 Received: 16 December 2019 / Revised: 8 May 2020 / Accepted: 28 May 2020 # Springer Nature Singapore Pte Ltd. 2020

Abstract Reactive distillation (RD) for methanol synthesis offers the advantage of process integration by combining reaction and separation in a single equipment and utilization of the reaction exotherm in the separation. The feasibility of RD for methanol synthesis using a polar solvent has already been demonstrated in an earlier work by Ghosh and Seethamraju (Chem Eng Process - Process Intensif, 145:107673, 2019) using a polar solvent. Since reaction and distillation occur simultaneously in the same column, the effect of operating and design parameters of the column is crucial for its performance. In this paper, the effects of different operating and design parameters have been presented using squalane—a non-polar solvent. Performance of RD for methanol synthesis was evaluated in terms of conversion of reactants, productivities of methanol and water, and purities of the product streams. Operating parameters like reflux ratio, solvent flow rate, and feed temperatures, and design parameters like addition of reactive and non-reactive stages were found to affect the column performance significantly. Based on the results from the parametric studies, optimization of the RD column was performed to maximize the methanol production in the liquid distillate. Conversions of CO and H2 were found to increase respectively from 52.9% and 36.8% in the base case to 78.4% (48% increase) and 54% (47% increase) in the optimum cases. Methanol productivity also increased by 47% relative to the base case with enhancement in separation of the produced methanol. Keywords Reactive distillation . Solvent . Methanol synthesis . Squalane . Optimization . Parametric studies

Abbreviations (r-)WGS (Reverse) Water gas shift BP Bottom product DME Dimethyl ether LD Liquid distillate MTBE Methyl tertiary butyl ether RD Reactive distillation RR Refluxed rectifier TEGDME Tetraethylene glycol dimethyl ether VD Vapor distillate VLE Vapor liquid equilibrium

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s41660-020-00122-x) contains supplementary material, which is available to authorized users. * Srinivas Seethamraju [email protected] 1

Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India

Notations Ei Activation energy for reaction “i” F0,S Flow rate of solvent feed stream Fj Fugacity of species “j” Keq,i Equilibrium constant of reaction “i” ki Pre-exponential factor of rate expression for reaction “i” Qk Heat duty of stage “k” R Universal gas constant ri Rate of reaction “i” T Temperature T0,G Temperature of syngas feed stream T0,S Temperature of solvent feed stream Tk Temperature of stage “k” Tref Reference temperature W Total weight of catalyst in the