Integrated solvent and process design for continuous crystallization and solvent recycling using PC‐SAFT

Solvent usage is a major source of environmental waste in pharmaceutical industry. The current paradigm shift toward continuous manufacturing in pharmaceutical industry has renewed the interest in continuous crystallization, which offers the prospect of easy solvent recycling. However, the selection of solvents for an integrated crystallization processes is nontrivial due to the likely trade‐off between optimal solvent properties for crystallization and solvent separation and recycling. A systematic approach for the simultaneous optimization of process conditions and solvent selection for continuous crystallization including solvent recycling is presented. A unified perturbed‐chain statistical associating fluid theory model framework is applied to predict thermodynamic properties related to solubility and vapor‐liquid equilibrium, which is integrated with a process model. A continuous mapping procedure is adopted to solve the optimization problem effectively. A case study based on continuous antisolvent crystallization of paracetamol with solvent separation via flash demonstrates the approach. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1205–1216, 2018     

Non‐dispersive absorption for CO2 capture: from the laboratory to industry

Research on capture and recovery of CO₂ has become a critical topic in the development of technological answers to the greenhouse effect. Conventional industrial processes do not fit into the philosophy of process intensification in which a radically new approach should lead to environmentally friendly methods with minimal use of natural resources and production of secondary waste. Conventional processes involve the use of large amounts of toxic organic solvents, such as diethylamine, and large equipment (e.g. absorption columns). Although CO₂ recovery began in industrial operation more than fifty years ago and, in spite of the clear potential for intensified processes demonstrated in the scientific literature, there is no real evidence that new processes for CO₂ recovery will achieve industrial implementation in the short term. In this perspective, the main limitations of membrane systems based on non‐dispersive absorption using porous membranes are outlined, in order to identify the main challenges that still have to be solved to achieve an industrially attractive process for CO₂ recovery. Copyright © 2011 Society of Chemical Industry     

A superstructure‐based mixed‐integer programming approach to optimal design of pipeline network for large‐scale CO2 transport

Pipeline transport is the major means for large‐scale and long‐distance CO₂ transport in a CO₂ capture and sequestration (CCS) project. But optimal design of the pipeline network remains a challenging problem, especially when considering allocation of intermediate sites, like pump stations, and selection of pipeline routes. A superstructure‐based mixed‐integer programming approach for optimal design of the pipeline network, targeting on minimizing the overall cost in a CCS project is presented. A decomposition algorithm to solve the computational difficulty caused by the large size and nonlinear nature of a real‐life design problem is also presented. To illustrate the capability of our models. A real‐life case study in North China, with 45 emissions sources and four storage sinks, is provided. The result shows that our model and decomposition algorithm is a practical and cost‐effective method for pipeline networks design. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2442–2461, 2014     

Determination of kinetics of CO2 absorption in solutions of 2‐amino‐2‐methyl‐1‐propanol using a microfluidic technique

The kinetics for the reactions of carbon dioxide with 2‐amine‐2‐methyl‐1‐propanol (AMP) and carbon dioxide (CO₂) in both aqueous and nonaqueous solutions were measured using a microfluidic method at a temperature range of 298–318 K. The mixtures of AMP‐water and AMP‐ethylene glycol were applied for the working systems. Gas‐liquid bubbly microflows were formed through a microsieve device and used to determine the reaction characteristics by online observation of the volume change of microbubbles at the initial flow stage. In this condition, a mathematical model according to zwitterion mechanism has been developed to predict the reaction kinetics. The predicted kinetics of CO₂ absorption in the AMP aqueous solution verified the reliability of the method by comparing with literatures’ results. Furthermore, the reaction rate parameters for the reaction of CO₂ with AMP in both solutions were determined. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4358–4366, 2015     

A multi‐objective optimization approach to polygeneration energy systems design

Polygeneration, typically involving co‐production of methanol and electricity, is a promising energy conversion technology which provides opportunities for high energy utilization efficiency and low/zero emissions. The optimal design of such a complex, large‐scale and highly nonlinear process system poses significant challenges. In this article, we present a multiobjective optimization model for the optimal design of a methanol/electricity polygeneration plant. Economic and environmental criteria are simultaneously optimized over a superstructure capturing a number of possible combinations of technologies and types of equipment. Aggregated models are considered, including a detailed methanol synthesis step with chemical kinetics and phase equilibrium considerations. The resulting model is formulated as a non‐convex mixed‐integer nonlinear programming problem. Global optimization and parallel computation techniques are employed to generate an optimal Pareto frontier. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

SO42−/ZrO2 supported on γ‐Al2O3 as a catalyst for CO2 desorption from CO2‐loaded monoethanolamine solutions

In this work, the composite catalysts, SO₄²/ZrO₂/γ‐Al₂O₃ (SZA), with different ZrO₂ and γ‐Al₂O₃ mass ratios were prepared and used for the first time for the carbon dioxide (CO₂)‐loaded monoethanolamine (MEA) solvent regeneration process to reduce the heat duty. The regeneration characteristics with five catalysts (three SZA catalysts and two parent catalysts) of a 5 M MEA solution with an initial CO₂ loading of 0.5 mol CO₂/mol amine at 98°C were investigated in terms of CO₂ desorption performance and compared with those of a blank test. All the catalysts were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption experiment, ammonia temperature programmed desorption, and pyridine‐adsorption infrared spectroscopy. The results indicate that the SZA catalysts exhibited superior catalytic activity to the parent catalysts. A possible catalytic mechanism for the CO₂ desorption process over SZA catalyst was proposed. The results reveal that SZA1/1, which possesses the highest joint value of Brφnsted acid sites (BASs) and mesopore surface area (MSA), presented the highest catalytic performance, decreasing the heat duty by 36.9% as compared to the catalyst‐free run. The SZA1/1 catalyst shows the best catalytic performance as compared with the reported catalyst for this purpose. Moreover, the SZA catalyst has advantages of low cost, good cyclic stability, easy regeneration and has no effect on the CO₂ absorption performance of MEA. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3988–4001, 2018     

Simultaneous Adsorption of SO2, NO,and CO2 by K2CO3‐Modified γ‐Alumina

The simultaneous adsorption of SO₂, NO, and CO₂ on K₂CO₃‐modified γ‐alumina under different operating conditions was studied in a fixed‐bed reactor. The experimental results showed that the influence of a temperature increase on the simultaneous adsorption of the three gases was complex and different from the effects seen when both chemical adsorption and competitive adsorption existed. An increase in O₂ concentration and small amounts of water could enhance the adsorption of SO₂ and NO while the adsorption of CO₂ was not influenced. The breakthrough curves of the simultaneous adsorption experiments suggested that the investigated adsorbent may be a good candidate for the simultaneous adsorption of SO₂, NO, and part of the CO₂ while the adsorption capacity for CO₂ still needs to be enhanced.     

Modeling of CO2 equilibrium solubility in a novel 1‐Diethylamino‐2‐Propanol Solvent

In this work, the equilibrium solubility of CO₂ in a 1‐diethylamino‐2‐propanol (1DEA2P) solution was determined as a function of 1DEA2P concentration (over the range of 1–2 M), temperature (in the range of 298–333 K), and CO₂ partial pressure (in the range of 8–101 kPa). These experimental results were used to fit the present correlation for K₂ (Kent‐Eisenberg model, Austgen model, and Li‐Shen model). It was found that all of the models could represent the CO₂ equilibrium solubility in 1DEA2P solution with ADDs for Kent‐Eisenberg model, Austgen model, and Li‐Shen model of 6.3, 7.3, and 12.2%, respectively. A new K₂ correlation model, the Liu‐Helei model, was also developed to predict the CO₂ equilibrium solubility in 1DEA2P solution with an excellent ADD of 3.4%. In addition, the heat of absorption of CO₂ in 1DEA2P solution estimated by using the Gibbs‐Helmholtz equation was found to be ?45.7 ± 3.7 kJ/mol. Information and guidelines about effectively using data for screened solvents is also provided based on the three absorption parameters: CO₂ equilibrium solubility, second order reaction constant (k₂), and CO₂ absorption heat. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4465–4475, 2017     

Kinetics of CO2 absorption into a novel 1‐diethylamino‐2‐propanol solvent using stopped‐flow technique

A stopped‐flow apparatus was used to measure the kinetics of carbon dioxide (CO₂) absorption into aqueous solution of 1‐diethylamino‐2‐propanol (1DEA2P) in terms of observed pseudo‐first‐order rate constant (k_o) and second‐order reaction rate constant (k₂), in this work. The experiments were conducted over a 1DEA2P concentration range of 120–751 mol/m³, and a temperature range of 298–313 K. As 1DEA2P is a tertiary amine, the base‐catalyzed hydration mechanism was, then, applied to correlate the experimental CO₂ absorption rate constants obtained from stopped‐flow apparatus. In addition, the pK_a of 1DEA2P was experimentally measured over a temperature range of 278–333 K. The Brønsted relationship between reaction rate constant (obtained from stopped‐flow apparatus) and pK_a was, then, studied. The results showed that the correlation based on the Brønsted relationship performed very well for predicting the absorption rate constant with an absolute average deviation of 5.2%, which is in an acceptable range of less than 10%. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3502–3510, 2014     

COSMO‐based computer‐aided molecular/mixture design: A focus on reaction solvents

In this article, we investigate reaction solvent design using COSMO‐RS thermodynamics in conjunction with computer‐aided molecular design (CAMD) techniques. CAMD using COSMO‐RS has the distinct advantage of being a method based in quantum chemistry, which allows for the incorporation of quantum‐level information about transition states, reactive intermediates, and other important species directly into CAMD problems. This work encompasses three main additions to our previous framework for solvent design (Austin et al., Chem Eng Sci. 2017;159:93–105): (1) altering the group contribution method to estimate hydrogen‐bonding and non‐hydrogen‐bonding σ‐profiles; (2) ab initio modeling of strong solute/solvent interactions such as H‐bonding or coordinate bonding; and (3) solving mixture design problems limited to common laboratory and industrial solvents. We apply this methodology to three diverse case studies: accelerating the reaction rate of a Menschutkin reaction, controlling the chemoselectivity of a lithiation reaction, and controlling the chemoselectivity of a nucleophilic aromatic substitution reaction. We report improved solvents/mixtures in all cases. © 2017 American Institute of Chemical Engineers AIChE J, 63: 104–122, 2018     

Simultaneous process synthesis and control design under uncertainty: A worst‐case performance approach

A new methodology that includes process synthesis and control structure decisions for the optimal process and control design of dynamic systems under uncertainty is presented. The method integrates dynamic flexibility and dynamic feasibility in a single optimization formulation, thus, reducing the costs to assess the optimal design. A robust stability test is also included in the proposed method to ensure that the optimal design is stable in the presence of magnitude‐bounded perturbations. Since disturbances are treated as stochastic time‐discrete unmeasured inputs, the optimal process synthesis and control design specified by this method remains feasible and stable in the presence of the most critical realizations in the disturbances. The proposed methodology has been applied to simultaneously design and control a system of CSTRs and a ternary distillation column. A study on the computational costs associated with this method is presented and compared to that required by a dynamic optimization‐based scheme. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2497–2514, 2013     

Outer approximation algorithm with physical domain reduction for computer‐aided molecular and separation process design

Integrated approaches to the design of separation systems based on computer‐aided molecular and process design (CAMPD) can yield an optimal solvent structure and process conditions. The underlying design problem, however, is a challenging mixed integer nonlinear problem, prone to convergence failure as a result of the strong and nonlinear interactions between solvent and process. To facilitate the solution of this problem, a modified outer‐approximation (OA) algorithm is proposed. Tests that remove infeasible regions from both the process and molecular domains are embedded within the OA framework. Four tests are developed to remove subdomains where constraints on phase behavior that are implicit in process models or explicit process (design) constraints are violated. The algorithm is applied to three case studies relating to the separation of methane and carbon dioxide at high pressure. The process model is highly nonlinear, and includes mass and energy balances as well as phase equilibrium relations and physical property models based on a group‐contribution version of the statistical associating fluid theory (SAFT‐γ Mie) and on the GC⁺ group contribution method for some pure component properties. A fully automated implementation of the proposed approach is found to converge successfully to a local solution in 30 problem instances. The results highlight the extent to which optimal solvent and process conditions are interrelated and dependent on process specifications and constraints. The robustness of the CAMPD algorithm makes it possible to adopt higher‐fidelity nonlinear models in molecular and process design. © 2016 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 62: 3484–3504, 2016     

A facile and practical approach to randomly methylated β‐cyclodextrin

BACKGROUND: Because of its high demand for use in pharmaceutical products, cosmetics, soil remediation technologies, etc., randomly methylated β‐cyclodextrin (RM‐β‐CD) is one of the most important cyclodextrin (CD) derivatives. The aim of this present work is to use a green and commercially available approach to obtain RM‐β‐CD. Compared with other methylated CDs, RM‐β‐CD with an asymmetric molecular structure has higher water solubility. When the degree of substitution (DS) is about 1.8, the solubility tends to increase with increasing temperature and is suitable for pharmaceutical applications. RESULTS: RM‐β‐CD was synthesized using a green approach with ideal DS equal to 1.79. The one step process of β‐cyclodextrin methylation by CH₃Cl instead of (CH₃)₂SO₄ at mild temperature (80 °C) and pressure (1.60 MPa) with a good yield (78%), is convenient and environmentally friendly. The mixture of RM‐β‐CD obtained contained five compounds with various DS, from which the main compound with a DS equal to 1.8 was separated by column chromatography. The compounds were carefully characterized by infra‐red, NMR and mass spectrometry. CONCLUSIONS: The one‐step process to RM‐β‐CDs with CH₃Cl is more economical, more efficient and less noxious than the usual method using (CH₃)₂SO₄. Moreover, this approach avoids some poisonous residual materials and meets the demand for protecting the environment. Copyright © 2009 Society of Chemical Industry     

Investigation of the effect of magnetic field on mass transfer parameters of CO2 absorption using Fe3O4‐water nanofluid

In this study, the enhancement of physical absorption of carbon dioxide by Fe₃O₄‐water nanofluid under the influence of AC and DC magnetic fields was investigated. Furthermore, a gas‐liquid mass transfer model for single bubble systems was applied to predict mass transfer parameters. The coated Fe₃O₄ nanoparticles were prepared using co‐percipitation method. The results from characterization indicated that the nanoparticles surfaces were covered with hydroxyl groups and nanoparticles diameter were 10–13 nm. The findings showed that the mass transfer rate and solubility of carbon dioxide in magnetic nanofluid increased with an increase in the magnetic field strength. Results indicated that the enhancement of carbon dioxide solubility and average molar flux gas into liquid phase, particularly in the case of AC magnetic field. Moreover, results demonstrated that mass diffusivity of CO₂ in nanofluid and renewal surface factor increased when the intensity of the field increased and consequently diffusion layer thickness decreased. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2176–2186, 2017     

A concise synthesis of single‐enantiomer β‐lactams and β‐amino acids using Rhodococcus globerulus

BACKGROUND: Pharmaceutical companies continue to evaluate β‐amino acids and β‐lactams in a range of drug candidates. The development of a highly efficient and selective bioresolution of cyclic β‐lactam substrates could yield enantiopure lactams and β‐amino acids with medicinal potential. The aim of this work was to discover and develop a biocatalyst capable of selectively hydrolysing β‐lactam substrates. RESULTS: Screening of our in‐house culture collection led to the discovery of a microorganism, Rhodococcus globerulus (NCIMB 41042) with β‐lactamase activity. Whole‐cell bioresolutions of the β‐lactams 1–4 were successfully carried out and in all cases enantiomeric excesses of the residual lactam and amino acid product were found to be greater than 98%. For one example, the bioresolution was optimised to operate at 60 g L^?1 substrate concentration with a 20% wt/wt cell paste loading. CONCLUSION: A microorganism, Rhodococcus globerulus (NCIMB 41042), capable of selectively hydrolysing a range of cyclic β‐lactams, has been discovered. A scalable whole‐cell bioresolution process has been developed, leading to the synthesis of multigram quantities of enantiomerically pure β‐lactams and β‐amino acids. Copyright © 2007 Society of Chemical Industry     

A new model for correlation and prediction of equilibrium CO2 solubility in N‐methyl‐4‐piperidinol solvent

In this work, the equilibrium CO₂ solubility in the aqueous tertiary amine, N‐methyl‐4‐piperidinol (MPDL) was measured over a range of temperatures, CO₂ partial pressures and amine concentrations. The dissociation constant of the MPDL solution was determined as well. A new thermodynamic model was developed to predict the equilibrium CO₂ solubility in the MPDL‐H₂O‐CO₂ system. This model, equipped with the correction factor (C_f), can give reasonable prediction with an average absolute deviation of 2.0%, and performs better than other models (i.e., KE model, Li‐Shen model, and Hu‐Chakma). The second‐order reaction rate constant (k₂) of MPDL and the heat of CO₂ absorption (–ΔH_abs) into aqueous MPDL solutions were evaluated as well. Based on the comparison with some conventional amines, MPDL revealed a high‐equilibrium CO₂ loading, reasonably fast absorption rate when compared with other tertiary amines, and a low energy requirement for regeneration. It may, therefore, be considered to be an alternative solvent for CO₂ capture. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3395–3403, 2017