Showing papers in "Aiche Journal in 2013"

PVAm–PIP/PS Composite Membrane with High Performance for CO2/N2 Separation

Abstract: Polyvinylamine (PVAm) was modified using a cross-linking agent containing carriers piperazine (PIP). Attenuated total reflectance fourier transform infrared, elemental analyzer, and X-ray diffraction were used to characterize the PIP-modified PVAm. The PVAm–PIP/polysulfone (PS) composite membrane was developed by coating PVAm–PIP mixed solutions with different mass ratios of PIP/PVAm (mPIP/mPVAm) on the PS ultrafiltration membrane. The effects of mPIP/mPVAm (from 0.715 to 2.860) in the coating solutions and wet coating thickness on the gas performance of the PVAm–PIP/PS composite membrane were investigated. The PVAm–PIP/PS composite membrane prepared showed higher performance than other membranes reported in the literature due to the large increase of the introducing carrier concentration and low crystallinity. Moreover, the separation performance stability of the PVAm–PIP/PS composite membrane was investigated and no deterioration in the membrane permselectivity was observed. Finally, the economic evaluation of the membrane with the highest performance prepared was carried out. © 2012 American Institute of Chemical Engineers AIChE J, 59: 215–228, 2013

Quality-relevant and process-relevant fault monitoring with concurrent projection to latent structures

Abstract: This paper proposes a new concurrent projection to latent structures is proposed in this paper for the monitoring of output-relevant faults that affect the quality and input-relevant process faults. The input and output data spaces are concurrently projected to five subspaces, a joint input-output subspace that captures covariations between input and output, an output-principal subspace, an output-residual subspace, an input-principal subspace, and an input-residual subspace. Fault detection indices are developed based on these subspaces for various fault detection alarms. The proposed monitoring method offers complete monitoring of faults that happen in the predictable output subspace and the unpredictable output residual subspace, as well as faults that affect the input spaces only. Numerical simulation examples and the Tennessee Eastman challenge problem are used to illustrate the effectiveness of the proposed method. © 2012 American Institute of Chemical Engineers AIChE J, 59: 496–504, 2013

Filtered two‐fluid models of fluidized gas‐particle flows: New constitutive relations

Abstract: New constitutive relations for filtered two-fluid models (TFM) of gas-particle flows are obtained by systematically filtering results generated through highly resolved simulations of a kinetic theory-based TFM. It was found in our earlier studies that the residual correlations appearing in the filtered TFM equations depended principally on the filter size and filtered particle volume fraction. Closer inspection of a large amount of computational data gathered in this study reveals an additional, systematic dependence of the correction to the drag coefficient on the filtered slip velocity, which serves as a marker for the extent of subfilter-scale inhomogeneity. Furthermore, the residual correlations for the momentum fluxes in the gas and particle phases arising from the subfilter-scale fluctuations are found to be modeled nicely using constitutive relations of the form used in large-eddy simulations of single-phase turbulent flows. V C 2013 American

Enhancement of CO2 Adsorption and CO2/N2 Selectivity on ZIF‐8 via Postsynthetic Modification

Abstract: Imidazolate framework ZIF-8 is modified via postsynthetic method using etheylenediamine to improve its adsorption performance toward CO2. Results show that the BET surface area of the modified ZIF-8 (ED-ZIF-8) increases by 39%, and its adsorption capacity of CO2 per surface area is almost two times of that on ZIF-8 at 298 K and 25 bar. H2O uptake on the ED-ZIF-8 become obviously lower compared to the ZIF-8. The ED-ZIF-8 selectivity for CO2/N2 adsorption gets significantly improved, and is up to 23 and 13.9 separately at 0.1 and 0.5 bar, being almost twice of those of the ZIF-8. The isosteric heat of CO2 adsorption (Qst) on the ED-ZIF-8 becomes higher, while Qst of N2 gets slightly lower compared to those on the ZIF-8 Furthermore, it suggests that the postsynthetic modification of the ZIF-8 not only improves its adsorption capacity of CO2 greatly, but also enhances its adsorption selectivity for CO2/N2/H2O significantly. ©2013 American Institute of Chemical Engineers AIChE J, 59: 2195–2206, 2013

Polymerization on heating up of bio‐oil: A model compound study

Abstract: Understanding of the condensation reactions in bio-oil is the key for efficient conversion into transportation fuel or value-added chemicals. In this study, the roles of the typical compounds representing the sugars, sugar derivatives, and aromatics found in bio-oil were investigated for their contribution to condensation reactions. Glucose played a key role for the polymer formation due to its decomposition to reactive compounds with multiple hydroxyl groups, carbonyl groups or conjugated π bonds. The sugar derivatives, including furfural, hydroxyl aldehyde and hydroxyl acetone, were also found to be reactive toward polymerization. The carboxylic acids were shown to be the catalysts for polymerization and formic acid was much more efficient to catalyze polymerization than acetic acid. The phenolic compounds also promoted the acid-catalyzed reactions. Vanillin contains reactive a carbonyl group, leading to its high tendency toward polymerization. In methanol, various kinds of methanolysis reactions dominated, which significantly suppressed the decomposition of glucose and the polymerization of other compounds. © 2012 American Institute of Chemical Engineers AIChE J, 59: 888–900, 2013

Membrane‐based ethylene/ethane separation: The upper bound and beyond

Abstract: Ethylene/ethane separation via cryogenic distillation is extremely energy-intensive, and membrane separation may provide an attractive alternative. In this paper, ethylene/ethane separation performance using polymeric membranes is summarized, and an experimental ethylene/ethane polymeric upper bound based on literature data is presented. A theoretical prediction of the ethylene/ethane upper bound is also presented, and shows good agreement with the experimental upper bound. Further, two ways to overcome the ethylene/ethane upper bound, based on increasing the sorption or diffusion selectivity, is also discussed, and a review on advanced membrane types such as facilitated transport membranes, zeolite and metal organic framework based membranes, and carbon molecular sieve membranes is presented. Of these, carbon membranes have shown the potential to surpass the polymeric ethylene/ethane upper bound performance. Furthermore, a convenient, potentially scalable method for tailoring the performance of carbon membranes for ethylene/ethane separation based on tuning the pyrolysis conditions has also been demonstrated. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3475–3489, 2013

Systematic modeling of discrete-continuous optimization models through generalized disjunctive programming

Abstract: Discrete-continuous optimization problems are commonly modeled in algebraic form as mixed-integer linear or nonlinear programming models. Since these models can be formulated in different ways, leading either to solvable or nonsolvable problems, there is a need for a systematic modeling framework that provides a fundamental understanding on the nature of these models. This work presents a modeling framework, generalized disjunctive programming (GDP), which represents problems in terms of Boolean and continuous variables, allowing the representation of constraints as algebraic equations, disjunctions and logic propositions. An overview is provided of major research results that have emerged in this area. Basic concepts are emphasized as well as the major classes of formulations that can be derived. These are illustrated with a number of examples in the area of process systems engineering. As will be shown, GDP provides a structured way for systematically deriving mixed-integer optimization models that exhibit strong continuous relaxations, which often translates into shorter computational times. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3276–3295, 2013

Directed Evolution: Past, Present, and Future

Abstract: Directed evolution, the laboratory process by which biological entities with desired traits are created through iterative rounds of genetic diversification and library screening or selection, has become one of the most useful and widespread tools in basic and applied biology. From its roots in classical strain engineering and adaptive evolution, modern directed evolution came of age 20 years ago with the demonstration of repeated rounds of polymerase chain reaction (PCR)-driven random mutagenesis and activity screening to improve protein properties. Since then, numerous techniques have been developed that have enabled the evolution of virtually any protein, pathway, network, or entire organism of interest. Here, we recount some of the major milestones in the history of directed evolution, highlight the most promising recent developments in the field, and discuss the future challenges and opportunities that lie ahead. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1432–1440, 2013

Carbon dioxide-in-water foams stabilized with nanoparticles and surfactant acting in synergy

Abstract: Synergistic interactions at the interface of nanoparticles (bare colloidal silica) and surfactant (caprylamidopropyl betaine) led to the generation of viscous and stable CO2-in-water (C/W) foams with fine texture at 19.4 MPa and 50°C. Interestingly, neither species generated C/W foams alone. The surfactant became cationic in the presence of CO2 and adsorbed on the hydrophilic silica nanoparticle surfaces resulting in an increase in the carbon dioxide/water/nanoparticle contact angle. The surfactant also adsorbed at the CO2–water interface, reducing interfacial tension to allow formation of finer bubbles. The foams were generated in a beadpack and characterized by apparent viscosity measurements both in the beadpack and in a capillary tube viscometer. In addition, the macroscopic foam stability was observed visually. The foam texture and viscosity were tunable by controlling the aqueous phase composition. Foam stability is discussed in terms of lamella drainage, disjoining pressure, interfacial viscosity, and hole formation. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3490–3501, 2013

Thermodynamic validation of 1‐alkyl‐3‐methylimidazolium carboxylates as task‐specific ionic liquids for H2S absorption

Abstract: Solubilities of H2S in five 1-alkyl-3-methylimidazolium carboxylates ionic liquids (ILs) have been measured at temperatures from 293.15 to 333.15 K and pressures up to 350 kPa. It is shown that these ILs have significantly larger absorption capacities for H2S than those common ILs reported in the literature. The solubility is found to increase dramatically with the increasing alkalinity of the anions and slightly with the increasing length of the alkyl chains on the cations. It is further demonstrated that the absorption isotherms are typically nonideal. With the assumption of complex formation between H2S and ILs, a reaction equilibrium thermodynamic model is developed to correlate the experimental solubilities. The model favors a reaction mechanism of AB2 type that two IL molecules interact with one H2S molecule. Thermodynamic parameters such as Henry’s law constants, reaction equilibrium constants, and heat of complex formation are also calculated to evaluate the absorption process of H2S in these ILs. V C 2012 American Institute of Chemical Engineers AIChE J, 59: 2227–

Analysis of CO2 sorption/desorption kinetic behaviors and reaction mechanisms on Li4SiO4

Abstract: The CO2 sorption/desorption kinetic behaviors on Li4SiO4 were analyzed. The theoretical compositions of the sorption/desorption reactions were calculated using FactSage. The sorption/desorption process on Li4SiO4 was investigated by comparing the shrinking core, double exponential, and Avrami–Erofeev models. The Avrami–Erofeev model fits the kinetic thermogravimetric experimental data well and, together with the double-shell mechanism, clearly explains the sorption/desorption mechanism. The sorption process is limited by the rate of the formation and growth of the crystals with double-shell structure consisting of Li2CO3 and Li2SiO3. The whole desorption process is found to be controlled by the rate of the formation and growth of the Li4SiO4 crystals. Furthermore, the influence of steam on the CO2 sorption process was analyzed. It has been observed that the presence of steam enhance the mobility of Li+ and, therefore, the rate of diffusion control stage. © 2012 American Institute of Chemical Engineers AIChE J, 59: 901–911, 2013

A novel method to extract vanadium and chromium from vanadium slag using molten NaOH-NaNO3 binary system

Abstract: A new method using NaOH-NaNO3 binary melts to treat vanadium slag is proposed. Vanadium and chromium can be simultaneously extracted in the leaching processes. Under the optimum reaction conditions, the recovery of vanadium and chromium can reach 93.7% and 88.2% in 6 h, respectively. The kinetics investigation indicates that the decomposition of vanadium slag is controlled by mass transfer in product layer. During the reaction, NaOH is believed to provide basic media and facilitate the dissolution of acidic oxides. NaNO3 decomposes to produce a large amount of active oxygen species, such as O, O-2(2-),and O2-. NaOH intensifies the decomposition of NaNO3 to NaNO2, but inhibits further decomposition of NaNO2. NaNO3 can be regenerated by oxidation of NaNO2 using oxygen at high temperature. The apparent activation energy of NaNO2 oxidation in the temperature ranging from 350 to 450 degrees C is 105.5 kJ/mol. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 541-552, 2013

Visualizing multiphase flow and trapped fluid configurations in a model three-dimensional porous medium

Abstract: We report an approach to fully visualize the flow of two immiscible fluids through a model three-dimensional (3-D) porous medium at pore-scale resolution. Using confocal microscopy, we directly image the drainage of the medium by the nonwetting oil and subsequent imbibition by the wetting fluid. During imbibition, the wetting fluid pinches off threads of oil in the narrow crevices of the medium, forming disconnected oil ganglia. Some of these ganglia remain trapped within the medium. By resolving the full 3-D structure of the trapped ganglia, we show that the typical ganglion size, as well as the total amount of residual oil, decreases as the capillary number Ca increases; this behavior reflects the competition between the viscous pressure in the wetting fluid and the capillary pressure required to force oil through the pores of the medium. This work thus shows how pore-scale fluid dynamics influence the trapped fluid configurations in multiphase flow through 3-D porous media. © 2013 American Institute of Chemical Engineers AIChE J, 59:1022-1029, 2013

Beyond shape selective catalysis with zeolites: Hydrophobic void spaces in zeolites enable catalysis in liquid water

Abstract: Zeolites confine active sites within void spaces of molecular dimension. The size and shape of these voids can be tuned by changing framework topology, which can influence catalytic reactivity and selectivity via coupled reaction-transport phenomena that exploit differences in transport properties among reactants and/or products that differ in size and shape. The polarity and solvating properties of intrazeolite void environments can be tuned by changing chemical composition and structure, ranging from hydrophobic defect-free pure-silica surfaces to silica surfaces containing hydrophilic defect sites and/or heteroatoms. Here, we discuss how the polarity of zeolite voids influences catalytic reactivity and selectivity via the partitioning of reactant, product, and solvent molecules between intrazeolitic locations and external fluid phases. These findings provide a conceptual basis for developing selective catalytic processes in aqueous media using hydrophobic zeolites that are able to adsorb organic reactants while excluding liquid water from internal void spaces.

A novel dynamic bayesian network‐based networked process monitoring approach for fault detection, propagation identification, and root cause diagnosis

Abstract: A novel networked process monitoring, fault propagation identification, and root cause diagnosis approach is developed in this study. First, process network structure is determined from prior process knowledge and analysis. The network model parameters including the conditional probability density functions of different nodes are then estimated from process operating data to characterize the causal relationships among the monitored variables. Subsequently, the Bayesian inference-based abnormality likelihood index is proposed to detect abnormal events in chemical processes. After the process fault is detected, the novel dynamic Bayesian probability and contribution indices are further developed from the transitional probabilities of monitored variables to identify the major faulty effect variables with significant upsets. With the dynamic Bayesian contribution index, the statistical inference rules are, thus, designed to search for the fault propagation pathways from the downstream backwards to the upstream process. In this way, the ending nodes in the identified propagation pathways can be captured as the root cause variables of process faults. Meanwhile, the identified fault propagation sequence provides an in-depth understanding as to the interactive effects of faults throughout the processes. The proposed approach is demonstrated using the illustrative continuous stirred tank reactor system and the Tennessee Eastman chemical process with the fault propagation identification results compared against those of the transfer entropy-based monitoring method. The results show that the novel networked process monitoring and diagnosis approach can accurately detect abnormal events, identify the fault propagation pathways, and diagnose the root cause variables. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2348–2365, 2013

Physical mechanism of sono‐Fenton process

Abstract: Hybrid advanced oxidation processes (AOPs), where two or more AOPs are applied simultaneously, are known to give effective degradation of recalcitrant organic pollutants. This article attempts to discern the physical mechanism of the hybrid sono-Fenton process with identification of links between individual mechanism of the sonolysis and Fenton process. An approach of coupling experimental results with simulations of cavitation bubble dynamics has been adopted for two textile dyes as model pollutants. Fenton process is revealed to have greater contribution than sonolysis in the overall decolorization of both dyes. H2O2 added to the liquid medium as a Fenton reagent scavenges •OH radicals produced by cavitation bubbles. Addition of only H2O2 to the medium during sonolysis does not yield marked difference in decolorization. Elimination of transient cavitation with application of elevated static pressure to the medium does not alter the extent of decolorization. The synergy between sonolysis and Fenton process is, thus, revealed to be negative. The dissolved oxygen in the medium is found to play an important role in decolorization through conservation of oxidizing radicals. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4303–4313, 2013

Equilibrium and kinetics analysis of carbon dioxide capture using immobilized amine on a mesoporous silica

Abstract: Thermogravimetric analysis is used to study the adsorption kinetics, equilibrium, and thermodynamics of CO2 on immobilized polyethylenimine sorbent impregnated on a mesoporous silica over the range of 300–390 K and 5–100% CO2 concentration. Adsorption isotherm models were fitted to the experimental data indicating that a change in adsorption mechanism occurred near 70°C. Below this temperature, the adsorption data followed the heterogeneous isotherms, while data taken at higher-temperatures followed isotherms for homogeneous surfaces. Heat of sorption was estimated to be 130 kJ/mole for the low-temperature regime, but this decreased to 48 kJ/mole above 70°C. The rate of CO2 fractional uptake decreased as temperature increased. A phenomenological kinetic model was derived from the Weibull distribution function using a nucleation growth theory to describe the two-step process. The kinetic model was used to predict the uptake at different operating conditions and resulted in good agreement with experimental data. Published 2012 American Institute of Chemical Engineers AIChE J, 2013

Cycle synthesis and optimization of a VSA process for postcombustion CO2 capture

Abstract: A systematic analysis of several vacuum swing adsorption (VSA) cycles with Zeochem zeolite 13X as the adsorbent to capture CO2 from dry, flue gas containing 15% CO2 in N2 is reported. Full optimization of the analyzed VSA cycles using genetic algorithm has been performed to obtain purity-recovery and energy-productivity Pareto fronts. These cycles are assessed for their ability to produce high-purity CO2 at high recovery. Configurations satisfying 90% purity-recovery constraints are ranked according to their energy-productivity Pareto fronts. It is shown that a 4-step VSA cycle with light product pressurization gives the minimum energy penalty of 131 kWh/tonne CO2 captured at a productivity of 0.57 mol CO2/m3 adsorbent/s. The minimum energy consumption required to achieve 95 and 97% purities, both at 90% recoveries, are 154 and 186 kWh/tonne CO2 captured, respectively. For the proposed cycle, it is shown that significant increase in productivity can be achieved with a marginal increase in energy consumption. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4735–4748, 2013

Comparative analysis of subgrid drag modifications for dense gas‐particle flows in bubbling fluidized beds

Abstract: Many subgrid drag modifications have been put forth to account for the effect of small unresolved scales on the resolved mesoscales in dense gas-particle flows. These subgrid drag modifications significantly differ in terms of their dependencies on the void fraction and the particle slip velocity. We, therefore, compare the hydrodynamics of a three-dimensional bubbling fluidized bed computed on a coarse grid using the drag correlations of the groups of (i) EMMS, (ii) Kuipers, (iii) Sundaresan, (iv) Simonin, and the homogenous drag law of (v) Wen and Yu with fine grid simulations for two different superficial gas velocities. Furthermore, we present an (vi) alternative approach, which distinguishes between resolved and unresolved particle clusters revealing a grid and slip velocity dependent heterogeneity index. Numerical results are analyzed with respect to the time-averaged solids volume fraction and its standard deviation, gas and solid flow patterns, bubble size, number density, and rise velocities. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4077–4099, 2013

Multiobjective optimization of biorefineries with economic and safety objectives

Abstract: A new approach for the incorporation of safety criteria into the selection, location, and sizing of a biorefinery is introduced. In addition to the techno-economic factors, risk metrics are used in the decision-making process by considering the cumulative risk associated with key stages of the life cycle of a biorefinery that includes biomass storage and transportation, process conversion into biofuels or bioproducts, and product storage. The fixed cost of the process along with the operating costs for transportation and processing as well as the value of the product are included. An optimization formulation is developed based on a superstructure that embeds potential supply chains of interest. The optimization program establishes the tradeoffs between cost and safety issues in the form of Pareto curves. A case study on bio-hydrogen production is solved to illustrate the merits of the proposed approach. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2427–2434, 2013

Quantitative analysis of gas hydrates using Raman spectroscopy

Abstract: A calibration protocol to quantify the compositional information of gas hydrates using Raman spectroscopy is proposed. Structure I pure CH4-, CO2- and C2H6-hydrates in their deuterated and hydrogenated forms with known cage occupancies were investigated by Raman spectroscopy. Raman scattering cross sections of CH4 in the large and small cages were found to be very similar, but not identical. Some C2H6 bands of C2H6-hydrate were tentatively reassigned or newly reported and assigned. Our results show that the relative cross sections of guest vibrational modes in the deuterated hydrate are in agreement with those in the hydrogenated hydrate, whereas they are considerably different from those in fluid phase. Using our Raman quantification factors, the relative cage occupancies can now be determined more reliably in CH4-hydrates. Moreover, with additional assumptions, the absolute cage occupancies, the bulk guest composition and hydration number of pure or mixed gas hydrates become accessible by Raman spectroscopy. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2155–2167, 2013

Optimization‐based framework for computer‐aided molecular design

Abstract: A new framework to automate, augment, and accelerate steps in computer-aided molecular design is presented. The problem is tackled in three stages: (1) composition design, (2) structure determination, and (3) extended design. Composition identification and structure determination are decoupled to achieve computational efficiency. Using approximate group-contribution methods in the first stage, molecular compositions that fit design targets are identified. In the second stage, isomer structures of solution compositions are determined systematically, and structure-based property corrections are used to refine the solution pool. In the final stage, the design is extended beyond the scope of group-contribution methods by using problem-specific property models. At each design stage, novel optimization models and graph theoretic algorithms generate a large and diverse pool of candidates using an assortment of property models. The wide applicability and computational efficiency of the proposed methodology are illustrated through three case studies. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3686–3701, 2013

3‐D full‐loop simulation of an industrial‐scale circulating fluidized‐bed boiler

Abstract: Three-dimensional (3-D) simulations using an Eulerian multiphase model were employed to explore flow behaviors in a full-loop industrial-scale CFB boiler with and without fluidized-bed heat exchanger (FBHE), where three solids phases were employed to roughly represent the polydisperse behavior of particles. First, a simulation of the boiler without FBHE is implemented to evaluate drag models, in terms of pressure profiles, mixing behaviors, radial velocity profiles, etc. Compared to the conventional model, the simulation using the energy-minimization multiscale (EMMS) model successfully predicts the pressure profile of the furnace. Then, such method is used to simulate the boiler with FBHE. The simulation shows that solid inventory in the furnace is underpredicted and reduced with an increase of the valve opening, probably due to the underevaluated drag for FBHE flows. It is suggested to improve EMMS model which is now based on a single set of operating parameters to match with the full-loop system. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1108-1117, 2013

Model‐based design of a plant‐wide control strategy for a continuous pharmaceutical plant

Abstract: The design of an effective plant-wide control strategy is a key challenge for the development of future continuous pharmaceutical processes. This article presents a case study for the design of a plant-wide control structure for a system inspired by an end-to-end continuous pharmaceutical pilot plant. A hierarchical decomposition strategy is used to classify control objectives. A plant-wide dynamic model of the process is used to generate parametric sensitivities, which provide a basis for the synthesis of control loops. Simulations for selected disturbances illustrate that the critical quality attributes (CQAs) of the final product can be kept close to specification in the presence of significant and persistent disturbances. Furthermore, it is illustrated how selected CQAs of the final product can be brought simultaneously to a new setpoint while maintaining the remaining CQAs at a constant value during this transition. The latter result shows flexibility to control CQAs independently of each other.

Distributed model predictive control based on dissipativity

Abstract: A noncooperative approach to plant-wide distributed model predictive control based on dissipativity conditions is developed. The plant-wide process and distributed control system are represented as two interacting process and controller networks, with interaction effects captured by the dissipativity properties of subsystems and network topologies. The plant-wide stability and performance conditions are developed based on global dissipativity conditions, which in turn are translated into the dissipative trajectory conditions that each local model predictive control MPC must satisfy. This approach is enabled by the use of dynamic supply rates in quadratic difference forms, which capture detailed dynamic system information. A case study is presented to illustrate the results. © 2012 American Institute of Chemical Engineers AIChE J, 59: 787–804, 2013

Computer-Aided Design of Tailor-Made Ionic Liquids

Abstract: Ionic liquids (IL), with their negligible vapor pressure, have the potential to replace volatile organic solvents in several processes. They also exhibit other unique characteristics, such as high thermal stability, wide liquid range, and wide electrochemical window, which make them attractive for many important applications. In addition, millions of ILs can be formed through different combination of cations, anions, and other functional groups. Till now, majority of work on IL selection, for a given application, is guided by trial and error experimentation. In this article, we present a computer-aided IL design framework, based on semiempirical structure-property models and optimization methods, which can consider several IL candidates and design optimal structures for a given application. This powerful methodology has great potential to act as a knowledge-based framework to aid synthetic chemists and engineers develop new ILs. VC 2013 American Institute of Chemical Engineers AIChE J, 59: 4627–4640, 2013

A new fragment contribution‐corresponding states method for physicochemical properties prediction of ionic liquids

Abstract: Ying HuangBeijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems,Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences,Beijing 100190, P.R. ChinaCollege of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences,Beijing 100049, P.R. ChinaHaifeng Dong, Xiangping Zhang, Chunshan Li, and Suojiang ZhangBeijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems,Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences,Beijing 100190, P.R. ChinaDOI 10.1002/aic.13910Published online in Wiley Online Library (wileyonlinelibrary.com).A new fragment contribution-corresponding states (FC—CS) method based on the group contribution method and thecorresponding states principle is developed to predict critical properties of ionic liquids (ILs). There are 46 fragmentsspecially classified for ILs considering the ionic features of ILs, and the corresponding fragment increments aredetermined using the experimental density data. The accuracy of the developed method is verified indirectly viapredicting density and surface tension of ILs. The results show that the FC—CS method is reasonable with an averageabsolute relative deviation less than 4%. With the calculated critical properties, corresponding states heat capacity(CSHC) and corresponding states thermal conductivity (CSTC) correlations are proposed to predict heat capacity andthermal conductivity of ILs, respectively. The predicted results agreed well with the experimental data. The proposedFC—CS method and the two corresponding states correlationsare important for design, simulation, and analysis of newionic liquid processes.

Planning and scheduling of flexible process networks under uncertainty with stochastic inventory: MINLP models and algorithm

Abstract: The tactical planning and scheduling of chemical process networks consisting of both dedicated and flexible processes under demand and supply uncertainty is addressed. To integrate the stochastic inventory control decisions with the production planning and scheduling, a mixed-integer nonlinear programming (MINLP) model is proposed that captures the stochastic nature of the demand variations and supply delays using the guaranteed-service approach. The model takes into account multiple tradeoffs and simultaneously determines the optimal selection of production schemes, purchase amounts of raw materials, sales of final products, production levels of processes, detailed cyclic production schedules for flexible processes, and working inventory and safety stock levels of all chemicals involved in the process network. To globally optimize the resulting nonconvex MINLP problems with modest computational times, the model properties are exploited and a tailored branch-and-refine algorithm based on the successive piecewise linear approximation is proposed. To handle the degeneracy of alternative optima in assignment configurations of production scheduling, three symmetry breaking cuts are further developed to accelerate the solution process. The application of the model and the performance of the proposed algorithm are illustrated through three examples with up to 25 chemicals and 16 processes including at most 8 production schemes for each flexible process. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1511–1532, 2013