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This work proposes a practical and systematic model-based approach to identify the optimal operating conditions for a simulated moving bed reactor (SMBR). The SMBR operation is applied to an industrial case study for the continuous production of a solvent, propylene glycol methyl ether acetate (DOWANOL™ PMA), which is produced through an acid-catalyzed esterification reaction of 1-methoxy-2-propanol and acetic acid. The model-based approach is demonstrated by lab-scale SMBR experiments. A multi-objective optimization problem was formulated for developing an SMBR process to maximize the production rate of PMA and the conversion of the esterification reaction simultaneously. In this study, this optimization problem is solved using the epsilon-constrained method and a Pareto plot is presented. The solutions that corresponded to three different values of conversion, 70%, 80%, and 85%, are experimentally validated. The SMBR model that was developed from batch kinetic and single column chromatography experiments demonstrates reasonable agreement with the experimental results. Furthermore, the SMBR experimental data was used to correct the parameters in the model. A validation study at a higher conversion of 95% demonstrates improved predictability of the corrected parameters.

In this study, the thermodynamic inhibition effects of choline chloride (ChCl, a hydrogen bond acceptor), urea (a hydrogen bond donor), and their mixture (deep eutectic solvent, DES) on CH4 hydrates were investigated with both experimental and computational approaches. The synthesis of DES from the mixture of ChCl and urea was confirmed by measuring its melting temperature through a high-pressure micro-differential scanning calorimeter. Sigma (σ)-profiles of ChCl, urea, and DES obtained by the COSMO-RS software indicated that these substances have great potential to be used as thermodynamic hydrate inhibitors (THIs). The three-phase (gas hydrate (H) – liquid water (Lw) – vapor (V)) equilibria of CH4 hydrates in the presence of ChCl (1.0, 3.0, and 5.0 mol%), urea (1.0, 3.0, and 5.0 mol%), and DES (3.0 mol%) demonstrated that ChCl, urea, and DES contributed to the significant shift of hydrate equilibrium temperature to inhibition regions at a specified pressure and thus can function as effective THIs. Moreover, quantum theory of atoms in molecules (QTAIM) analysis also demonstrated that the strength of hydrogen bonding between inhibitor molecules and hydrate cages (small 512 and large 51262 cages) of CH4 hydrates was in the order of ChCl > DES > urea, which was consistent with experimental results. The experimental and computational results from this study would be helpful for a better understanding of the inhibition mechanism of ChCl, urea, and DES and for their possible application to flow assurance in oil and gas pipelines.

As an industrial case study, esterification of acetic acid with 1-methoxy-2-propanol using a cation exchange resin has been investigated using a well-stirred batch reactor and chromatographic reactor. Well-stirred batch reactor experiments were conducted over different operating conditions to analyze the reaction equilibrium and kinetics. It was found that the final conversion was limited by equilibrium, and temperature had no significant effect on increasing the final conversion. Parameters in a reaction rate model were obtained at different temperatures (50–90 °C). Since the well-stirred batch experiment alone was not enough to capture the adsorption behavior of the system, pulse injections of each component into the chromatographic column were conducted to obtain the adsorption parameters. The esterification reaction was performed systematically in a lab-scaled chromatographic reactor at different flow rates (0.2–1 ml/min), injection volumes (0.05 ml, 0.5 ml), and temperatures (70–110 °C). A mathematical model for isothermal equilibrium dispersive model was implemented and parameters were determined by fitting the model to the experimental data. It was observed that when the injection volume of single component was too large, two reaction sites were formed inside the column, resulting in a deformed peak shape of the product in the outlet chromatogram. Nearly 100% of conversion, which was infeasible in the well-stirred batch reactor, was achieved when the flow rate was low and the injection volume was small. The results indicate that the chromatographic reactor enhanced the reaction beyond the equilibrium by separating the products from the reaction sites.