Showing papers in "Aiche Journal in 2014"
TL;DR: Automated learning of algebraic models for optimization (ALAMO), the computational implementation of the proposed methodology, along with examples and extensive computational comparisons between ALAMO and a variety of machine learning techniques, including Latin hypercube sampling, simple least-squares regression, and the lasso are described.
Abstract: A central problem in modeling, namely that of learning an algebraic model from data obtained from simulations or experiments is addressed. A methodology that uses a small number of simulations or experiments to learn models that are as accurate and as simple as possible is proposed. The approach begins by building a low-complexity surrogate model. The model is built using a best subset technique that leverages an integer programming formulation to allow for the efficient consideration of a large number of possible functional components in the model. The model is then improved systematically through the use of derivative-free optimization solvers to adaptively sample new simulation or experimental points. Automated learning of algebraic models for optimization (ALAMO), the computational implementation of the proposed methodology, along with examples and extensive computational comparisons between ALAMO and a variety of machine learning techniques, including Latin hypercube sampling, simple least-squares regression, and the lasso is described. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2211–2227, 2014
325 citations
307 citations
TL;DR: The literature on drying sessile droplets and deposition of suspended material is reviewed including the simple explanation of the “coffee ring” deposit given by Deegan et al. as discussed by the authors.
Abstract: The literature on drying sessile droplets and deposition of suspended material is reviewed including the simple explanation of the “coffee ring” deposit given by Deegan et al.1 Analytical and numerical solutions for the flow are given, including the effect of Marangoni stresses, pinning or movement of the contact line, and viscous, thermal, gravitational, and other effects. The solution space is explored using dimensionless groups governing mass, momentum, and heat transfer effects in the droplet, external gas, and substrate. The most common types of deposition patterns are summarized, including those produced by pinned contact lines, sticking-and-slipping contact lines, and Marangoni effects. The influence of contact-line deposits is also reviewed, and the effects of colloidal, polymeric, and other depositing materials. Advanced applications from ink-jet printing to disease diagnosis are discussed as well. The review helps readers take stock of what has been learned and what remains incompletely explained. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1538–1571, 2014
306 citations
TL;DR: A comprehensive review on the recent progress made by chemical engineers focusing on the issues of predictive thermodynamic models, structure-property relations, separation mechanisms, and process simulation and optimization is provided in this article.
Abstract: Extractive distillation is commonly used for the separation of azeotropic or close-boiling mixtures in the chemical industry. During the past decade, the use of ionic liquids (ILs) as entrainers has received considerable attention due to their unique advantages when applied in extractive distillation. This work is devoted to providing an easy-to-read and comprehensive review on the recent progress made by chemical engineers, focusing on the issues of predictive thermodynamic models, structure-property relations, separation mechanisms, and process simulation and optimization. This review spans from the molecular level to the industrial scale, to provide a theoretical insight into the molecular interactions between ILs and the components to be separated. Moreover, a comprehensive database on the vapor–liquid equilibria and activity coefficients at infinite dilution concerning ILs is provided as Supporting Information. Concluding remarks are made on the unsolved scientific issues with respect to this promising special distillation technology. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3312–3329, 2014
250 citations
TL;DR: In this article, the accuracy of particle centroid method and analytical approach in predicting the particle-fluid flow characteristics of bubbling fluidized beds was investigated, and it was found that there is a critical cell size (3.82 particle diameters) beyond which the PCM can achieve the same numerical stability and prediction accuracy as those of analytical approach.
Abstract: The correct calculation of cell void fraction is pivotal in accurate simulation of two-phase flows using a computational fluid dynamics-discrete element method (CFD-DEM) approach. Two classical approaches for void fraction calculations (i.e., particle centroid method or PCM and analytical approach) were examined, and the accuracy of these methodologies in predicting the particle-fluid flow characteristics of bubbling fluidized beds was investigated. It was found that there is a critical cell size (3.82 particle diameters) beyond which the PCM can achieve the same numerical stability and prediction accuracy as those of the analytical approach. There is also a critical cell size (1/19.3 domain size) below which meso-scale flow structures are resolved. Moreover, a lower limit of cell size (1.63 particle diameters) was identified to satisfy the assumptions of CFD-DEM governing equations. A reference map for selecting the ideal computational cell size and the suitable approach for void fraction calculation was subsequently developed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2000–2018, 2014
217 citations
TL;DR: In this article, the capture and concentration of CO2 from a dry flue gas by vacuum swing adsorption (VSA) has been experimentally demonstrated in a pilot plant.
Abstract: The capture and concentration of CO2 from a dry flue gas by vacuum swing adsorption (VSA) has been experimentally demonstrated in a pilot plant. The pilot plant has the provision for using two coupled columns that are each packed with approximately 41 kg of Zeochem zeolite 13X. Breakthrough experiments were first carried out by perturbing a N2 saturated bed with 15% CO2 and 85% N2 feed, which is representative of a dry flue gas from coal-fired power plants. The breakthrough results showed long plateaus in temperature profiles confirming a near adiabatic behavior. In the process study, a basic four-step vacuum swing adsorption (VSA) cycle comprising the following steps: pressurization with feed, adsorption, forward blowdown, and reverse evacuation was investigated first. In the absence of any coupling among the steps, a single bed was used. With this cycle configuration, CO2 was concentrated to 95.9 ± 1% with a recovery of 86.4 ± 5.6%. To improve the process performance, a four-step cycle with light product pressurization (LPP) using two beds was investigated. This cycle was able to achieve 94.8 ± 1% purity and 89.7 ± 5.6% recovery. The Department of Energy requirements are 95% purity and 90% recovery. The proposed underlying physics of performance improvement of the four-step cycle with LPP has also been experimentally validated. The pilot plant results were then used for detailed validation of a one-dimensional, nonisothermal, and nonisobaric model. Both transient profiles of various measured variables and cyclic steady state performance results were compared with the model predictions, and they were in good agreement. The energy consumptions in the pilot plant experiments were 339–583 ± 36.7 kWh tonne−1 CO2 captured and they were significantly different from the theoretical power consumptions obtained from isentropic compression calculations. The productivities were 0.87–1.4 ± 0.07 tonne CO2 m−3 adsorbent day−1. The results from our pilot plant were also compared with available results from other pilot plant studies on CO2 capture from flue gas. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1830–1842, 2014
191 citations
153 citations
TL;DR: In this article, a multobjective mixed-integer nonlinear programming (MINLP) model is developed to simultaneously optimize the unit cost and the unit global warming potential (GWP) in a large-scale algae processing network.
Abstract: Global optimization for sustainable design and synthesis of a large-scale algae processing network under economic and environmental criteria is addressed. An algae processing network superstructure including 7800 processing routes is proposed. Based on the superstructure, a multiobjective mixed-integer nonlinear programming (MINLP) model is developed to simultaneously optimize the unit cost and the unit global warming potential (GWP). To efficiently solve the nonconvex MINLP model with separable concave terms and mixed-integer fractional terms in the objective functions, a global optimization strategy that integrates a branch-and-refine algorithm based on successive piecewise linear approximations is proposed and an exact parametric algorithm based on Newton’s method. Two Pareto-optimal curves are obtained for biofuel production and biological carbon sequestration, respectively. The unit annual biofuel production cost ranges from $7.02/gasoline gallon equivalent (GGE) to $9.71/GGE, corresponding to unit GWP’s of 26.491 to 16.52 kg CO2-eq/GGE, respectively. V C 2014 American Institute of Chemical Engineers AIChE J, 60: 3195–3210, 2014
139 citations
TL;DR: In this paper, two different approaches to constitutive relations for filtered two-fluid models (TFM) of gas-solid flows are deduced, based on the assumption of the formation of subgrid heterogeneities inside the suspension phase of fluidized beds.
Abstract: Two different approaches to constitutive relations for filtered two-fluid models (TFM) of gas–solid flows are deduced. The first model (Model A) is derived using systematically filtered results obtained from a highly resolved simulation of a bubbling fluidized bed. The second model (Model B) stems from the assumption of the formation of subgrid heterogeneities inside the suspension phase of fluidized beds. These approaches for the unresolved terms appearing in the filtered TFM are, then, substantiated by the corresponding filtered data. Furthermore, the presented models are verified in the case of the bubbling fluidized bed used to generate the fine grid data. The numerical results obtained on coarse grids demonstrate that the computed bed hydrodynamics is in fairly good agreement with the highly resolved simulation. The results further show that the contribution from the unresolved frictional stresses is required to correctly predict the bubble rise velocity using coarse grids. © 2013 American Institute of Chemical Engineers AIChE J, 60: 839–854, 2014
132 citations
TL;DR: Cafaro et al. as discussed by the authors presented a model for the extraction of the Quimica in the context of the Nacional de Investigaciones Cientificas y Tecnicas.
Abstract: Fil: Cafaro, Diego Carlos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica (i); Argentina
130 citations
TL;DR: In this article, a two-stage stochastic mixed-integer linear programming model for hydraulic fracturing is proposed to minimize expected transportation, treatment, storage, and disposal cost while accounting for the revenue from gas production.
Abstract: There are four key aspects for water use in hydraulic fracturing, including source water acquisition, wastewater production, reuse and recycle, and subsequent transportation, storage, and disposal. Water use life cycle is optimized for wellpads through a discrete-time two-stage stochastic mixed-integer linear programming model under uncertain availability of water. The objective is to minimize expected transportation, treatment, storage, and disposal cost while accounting for the revenue from gas production. Assuming freshwater sources, river withdrawal data, location of wellpads, and treatment facilities are given, the goal is to determine an optimal fracturing schedule in coordination with water transportation, and its treatment and reuse. The proposed models consider a long-time horizon and multiple scenarios from historical data. Two examples representative of the Marcellus Shale play are presented to illustrate the effectiveness of the formulation, and to identify optimization opportunities that can improve both the environmental impact and economical use of water. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3490–3501, 2014
TL;DR: In this paper, a novel cross-linked polyimide substrate, consisting of a thin skin layer with minimum solvent transport resistance and a sponge-like sublayer structure that could withstand membrane compaction under high pressure was first fabricated.
Abstract: The development of high flux and solvent-stable thin-film composite (TFC) organic solvent nanofiltration (OSN) membranes was reported. A novel cross-linked polyimide substrate, consisting of a thin skin layer with minimum solvent transport resistance and a sponge-like sublayer structure that could withstand membrane compaction under high-pressure was first fabricated. Then the solvent flux was significantly enhanced without compromising the solute rejection by the coupling effects of (1) the addition of triethylamine/camphorsulfonic acid into the monomer solution, and (2) the combined post-treatments of glycerol/sodium dodecyl sulphate immersion and dimethyl sulfoxide (DMSO) filtration. Finally, the long-term stability of the TFC membrane in aprotic solvents such as DMSO was improved by post-crosslink thermal annealing. The novel TFC OSN membrane developed was found to have superior rejection to tetracycline (MW: 444 g/mol) but was very permeable to alcohols such as methanol (5.12 lm−2h−1bar−1) and aprotic solvents such as dimethylformamide (3.92 lm−2h−1bar−1) and DMSO (3.34 lm−2h−1bar−1). © 2014 American Institute of Chemical Engineers AIChE J, 60: 3623–3633, 2014
TL;DR: ZIF-8/6FDA-DAM, a proven mixed-matrix material that demonstrated remarkably enhanced C3H6/C3H8 selectivity in dense film geometry, was extended to scalable hollow fiber geometry in the current work as mentioned in this paper.
Abstract: ZIF-8/6FDA-DAM, a proven mixed-matrix material that demonstrated remarkably enhanced C3H6/C3H8 selectivity in dense film geometry, was extended to scalable hollow fiber geometry in the current work. We successfully formed dual-layer ZIF-8/6FDA-DAM mixed-matrix hollow fiber membranes with ZIF-8 nanoparticle loading up to 30 wt % using the conventional dry-jet/wet-quench fiber spinning technique. The mixed-matrix hollow fibers showed significantly enhanced C3H6/C3H8 selectivity that was consistent with mixed-matrix dense films. Critical variables controlling successful formation of mixed-matrix hollow fiber membranes with desirable morphology and attractive transport properties were discussed. Furthermore, the effects of coating materials on selectivity recovery of partially defective fibers were investigated. To our best knowledge, this is the first article reporting successful formation of high-loading mixed-matrix hollow fiber membranes with significantly enhanced selectivity for separation of condensable olefin/paraffin mixtures. Therefore, it represents a major step in the research area of advanced mixed-matrix membranes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2625–2635, 2014
TL;DR: In this paper, the solubilities of H2S and CO2 in four protic ionic liquids (PILs) were determined at 303.2 K and 0-1.2 bar.
Abstract: The solubilities of H2S and CO2 in four protic ionic liquids (PILs)—methyldiethanolammonium acetate, methyldiethanolammonium formate, dimethylethanolammonium acetate, and dimethylethanolammonium formate were determined at 303.2–333.2 K and 0–1.2 bar. It is shown PILs have higher absorption capacity for H2S than normal ionic liquids (ILs) and the Henry’s law constants of H2S in PILs (3.5–11.5 bar at 303.2 K) are much lower than those in normal ILs. In contrast, the solubility of CO2 in PILs is found to be a magnitude lower than that of H2S, implying these PILs have both higher absorption capacity for H2S and higher ideal selectivity of H2S/CO2 (8.9–19.5 at 303.2 K) in comparison with normal ILs. The behavior of H2S and CO2 absorption in PILs is further demonstrated based on thermodynamic analysis. The results illustrate that PILs are a kind of promising absorbents for the selective separation of H2S/CO2 and believed to have potential use in gas sweetening. V C 2014 American Institute of Chemical Engineers AIChE J, 60: 4232–
TL;DR: Sun et al. as mentioned in this paper proposed a method to synthesize sulfur oxides (SO) from SO oxides, which is a type of SO oxide that can be used in the field of chemical engineering.
Abstract: Weizhen SunState-Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai200237, ChinaDept. of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720Key Laboratory of Advanced Control and Optimization for Chemical Processes, East China University of Scienceand Technology, Shanghai 200237, ChinaLi-Chiang LinDept. of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720Xuan PengDept. of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720Dept. of Automation, College of Information Science and Technology, Beijing University of ChemicalTechnology, Beijing 100029, ChinaBerend SmitDept. of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720Dept. of Chemistry, University of California, Berkeley, CA 94720Materials Sciences Div., Lawrence Berkeley National Laboratory, Berkeley, CA 94720DOI 10.1002/aic.14467Published online April 23, 2014 in Wiley Online Library (wileyonlinelibrary.com)Sulfur oxides (SO
TL;DR: In this article, the UNIFAC model was used for predicting the CO2 solubility in pure ionic liquid (IL) and in the binary mixture of ILs both at high and low temperatures.
Abstract: The new group binary interaction parameters of UNIFAC model (anm and amn) between CO2 and 22 ionic liquid (IL) groups were obtained by means of correlating the solubility data of CO2 in pure ILs at different temperatures (>273.2 K). We measured the CO2 solubility at low temperatures down to 243.2 K in pure ILs, i.e., [OMIM]+[BF4]− and [OMIM]+[Tf2N]−, and their equimolar amount of mixture, in order to fill the blank of solubility data at low temperatures and also to justify the applicability of UNIFAC model over a wider temperature range. It was verified that UNIFAC model can be used for predicting the CO2 solubility in pure ILs and in the binary mixture of ILs both at high (>273.2 K) and low temperatures (<273.2 K) effectively, as well as identifying the new structure–property relation. This is the first work to extend the UNIFAC model to IL-CO2 systems. © 2013 American Institute of Chemical Engineers AIChE J 60: 716–729, 2014
TL;DR: In this paper, a combined theoretical and experimental approach is presented that uses a comprehensive mean-field microkinetic model, reaction kinetics experiments, and scanning transmission electron microscopy imaging to unravel the reaction mechanism and provide insights into the nature of active sites for formic acid (HCOOH) decomposition on Au/SiC catalysts.
Abstract: A combined theoretical and experimental approach is presented that uses a comprehensive mean-field microkinetic model, reaction kinetics experiments, and scanning transmission electron microscopy imaging to unravel the reaction mechanism and provide insights into the nature of active sites for formic acid (HCOOH) decomposition on Au/SiC catalysts. All input parameters for the microkinetic model are derived from periodic, self-consistent, generalized gradient approximation (GGA-PW91) density functional theory calculations on the Au(111), Au(100), and Au(211) surfaces and are subsequently adjusted to describe the experimental HCOOH decomposition rate and selectivity data. It is shown that the HCOOH decomposition follows the formate (HCOO) mediated path, with 100% selectivity toward the dehydrogenation products (CO2 1H2) under all reaction conditions. An analysis of the kinetic parameters suggests that an Au surface in which the coordination number of surface Au atoms is � 4 may provide a better model for the active site of HCOOH decomposition on these specific supported Au catalysts. V C 2014 American Institute of Chemical Engineers
TL;DR: In this paper, a just-in-time reorganized PCA model that objectively selects the principal components (PCs) online for process monitoring is proposed, and the importance of the PCs is evaluated by kernel density estimation.
Abstract: Although principal component analysis (PCA) is widely used for chemical process monitoring, improvements in the selection of principal components (PCs) are still needed. Given that the determination of complicated and changing fault information is not guaranteed using offline-selected PCs, this study proposes a just-in-time reorganized PCA model that objectively selects the PCs online for process monitoring. The importance of the PCs is evaluated online by kernel density estimation. The PCs indicating more varied information are then selected to reorganize the PCA model. Given that the most useful fault information is concentrated, support vector data description is used to replace traditional statistics, thereby relaxing the Gaussian assumption of the process data. The monitoring performances of the proposed method are evaluated under three cases. Compared with conventional PCA methods, more varied information is captured online, and the monitoring performances are improved. © 2014 American Institute of Chemical Engineers AIChE J, 60: 949–965, 2014
TL;DR: In this article, a mixture form of the semisupervised probabilistic principal component regression model is proposed for soft sensor application, which can efficiently incorporate the unlabeled data information from different operation modes.
Abstract: Traditionally, data-based soft sensors are constructed upon the labeled historical dataset which contains equal numbers of input and output data samples. While it is easy to obtain input variables such as temperature, pressure, and flow rate in the chemical process, the output variables, which correspond to quality/key property variables, are much more difficult to obtain. Therefore, we may only have a small number of output data samples, and have much more input data samples. In this article, a mixture form of the semisupervised probabilistic principal component regression model is proposed for soft sensor application, which can efficiently incorporate the unlabeled data information from different operation modes. Compared to the total supervised method, both modeling efficiency and soft sensing performance are improved with the inclusion of additional unlabeled data samples. Two case studies are provided to evaluate the feasibility and efficiency of the new method. © 2013 American Institute of Chemical Engineers AIChE J 60: 533–545, 2014
TL;DR: In this article, the accuracy of the discrete element method (DEM) for the simulation of solids mixing using non-intrusive Lagrangian radioactive particle tracking data, and explains why it may provide physically sound results even when non-real particle properties are used.
Abstract: This work assesses the accuracy of the discrete element method (DEM) for the simulation of solids mixing using non-intrusive Lagrangian radioactive particle tracking data, and explains why it may provide physically sound results even when non-real particle properties are used. The simulation results concern the size segregation of polydisperse granules in a rotating drum operated in rolling mode. Given that the DEM is sensitive to simulation parameters, the granule properties were measured experimentally or extracted from the literature. Several flow phenomena are investigated numerically and experimentally, including the particle residence time, the radial segregation, and the radial variation of the axial dispersion coefficient. An analysis of the DEM model is then presented, with an emphasis on the Young's modulus and friction coefficients. Finally, dimensionless motion equations and corresponding dimensionless numbers are derived to investigate the effect of simulation parameters on particle dynamics. © 2013 American Institute of Chemical Engineers AIChE J, 60: 60–75, 2014
TL;DR: In this paper, a large database is generated which is used to test expressions describing different micro-macro relationships such as Archie's law, tortuosity, and constrictivity equations.
Abstract: The microstructure influence on conductive transport processes is described in terms of volume fraction e, tortuosity τ, and constrictivity β. Virtual microstructures with different parameter constellations are produced using methods from stochastic geometry. Effective conductivities σeff are obtained from solving the diffusion equation in a finite element model. In this way, a large database is generated which is used to test expressions describing different micro–macro relationships such as Archie's law, tortuosity, and constrictivity equations. It turns out that the constrictivity equation has the highest accuracy indicating that all three parameters (e,τ,β) are necessary to capture the microstructure influence correctly. The predictive capability of the constrictivity equation is improved by introducing modifications of it and using error-minimization, which leads to the following expression: σeff =σ02.03e1.57β0.72/τ2 with intrinsic conductivity σ0. The equation is important for future studies in, for example, batteries, fuel cells, and for transport processes in porous materials. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1983–1999, 2014
TL;DR: In this paper, a dual-site reaction mechanism for steam reforming of toluene is proposed for La 0.8Sr0.2Ni0.8Fe 0.2O3 perovskite catalyst.
Abstract: Reaction mechanism for steam reforming of toluene is proposed for La0.8Sr0.2Ni0.8Fe0.2O3 perovskite catalyst. The proposed mechanism was derived from various characterization results such as temperature-programmed desorption (TPD) and temperature-programmed surface reaction (TPSR) water, TPSR toluene, TPD O2 and in situ DRIFT of toluene decomposition, and steam reforming of toluene. Five kinetic models were developed based on the proposed dual-site reaction mechanism using Langmuir–Hinshelwood approach. Subsequently, the parameters of the kinetic models were estimated by nonlinear least square regression. A good agreement was obtained between experimental and model predicted results for the rate determining step based on reaction between adsorbed aldehyde and adsorbed oxygen. The adsorbed aldehyde species is produced from the reaction between adsorbed C2H2 or CH2 and adsorbed oxygen while the adsorbed oxygen species can come from the oxygen from water activation, lattice oxygen species, and/or the redox property of some metals such as Fe. This shows that the adsorbed oxygen species plays important role in this reaction. © 2014 American Institute of Chemical Engineers AIChE J 60: 4190–4198, 2014
TL;DR: In this paper, a typical and popular type of MOFs, ZIF-8, was synthesized and carbonized directly to produce highly porous carbon without washing or activation, and the resulting carbon was found to be a promising candidate for adsorption desulfurization of DBT.
Abstract: ZIF-8, a typical and popular type of MOFs, was synthesized and carbonized directly to produce highly porous carbon without washing or activation. The resulting carbon was found to be a promising candidate for adsorption desulfurization of DBT with a maximum adsorption capacity of 26.7 mgS/g in the concentration range below 174 ppmS, and the adsorption capacity decreased approximately 17% with the addition of 10% para-xylene. VC 2014 American Institute of Chemical Engineers AIChE J, 60: 2747–2751, 2014
TL;DR: In this article, the effect of bed material (glass, alumina, and low linear density polyethylene (LLDPE), dp ∼1 mm), inlet gas velocity, and initial particle bed height on the bubble behavior was investigated in a cylindrical column of 0.1m diameter.
Abstract: Bubble characteristics in a three-dimension gas-fluidized bed (FB) have been measured using noninvasive ultrafast electron beam X-ray tomography. The measurements are compared with predictions by a two-fluid model (TFM) based on kinetic theory of granular flow. The effect of bed material (glass, alumina, and low linear density polyethylene (LLDPE), dp ∼1 mm), inlet gas velocity, and initial particle bed height on the bubble behavior is investigated in a cylindrical column of 0.1-m diameter. The bubble rise velocity is determined by cross correlation of images from dual horizontal planes. The bubble characteristics depend highly upon the particle collisional properties. The bubble sizes obtained from experiments and simulations show good agreement. The LLDPE particles show high gas hold-up and higher bubble rise velocity than predicted on basis of literature correlations. The bed expansion is relatively high for LLDPE particles. The X-ray tomography and TFM results provide in-depth understanding of bubble behavior in FBs containing different granular material types. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1632–1644, 2014
TL;DR: In this article, a composite ionic liquid showed efficient catalytic performance at a short contact time (10−60 s), and the optimal conditions were: reaction temperature 15°C, contact time 20 s.
Abstract: Alkylate is an important clean blending component of gasoline due to the increased statutory reduction of the content of aromatics and olefins in commercial gasoline. The alkylation of isobutane with 2-butene catalyzed by a composite ionic liquid was investigated. The composite ionic liquid showed efficient catalytic performance at a short contact time (10–60 s). The optimal conditions were: reaction temperature 15°C, contact time 20 s, ionic liquid to hydrocarbon volume ratio 1:1, and isobutane to olefin mole ratio 54:1. Under these optimal reaction conditions, the butene conversion was 100%, the yields of C8 and trimethylpentanes were 88.9 and 82.0%, respectively, the ratio of trimethylpentane to dimethylhexane was 11.9, and the alkylate research octane number (RON) was 97.3. A correlation model is developed to predict the product yields and the alkylate RON. The correlation model shows a low calculation error. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2244–2253, 2014
TL;DR: In this paper, the influence of key variables on the performance of an experimental system for continuous electroreduction of CO2 to formate with a gas diffusion electrode (GDE) loaded with Sn.
Abstract: Electrochemical valorization may be a strategy for mitigating climate change, as the process allows for CO2 to be converted into industrially useful chemicals. The aim of this work is to study the influence of key variables on the performance of an experimental system for continuous electroreduction of CO2 to formate with a gas diffusion electrode (GDE) loaded with Sn. A 23 factorial design of experiments at different levels of current density (j), electrolyte flow rate/electrode area ratio (Q/A ratio) and GDE Sn load was followed. Higher rates and concentrations (i.e., 1.4·10−3 mol m−2 s−1 and 1348 mg L−1 with efficiencies of approximately 70%) were obtained with GDEs than with plate electrodes. The statistical design of experiments demonstrated that the Sn load had the most significant effect on rate and efficiency. However, despite these promising results, further research is required to optimize the process. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3557–3564, 2014
TL;DR: In this paper, an efficient computational screening approach is proposed to select the most cost-effective materials and adsorption process conditions for CH4/CO2 separation, and eight novel zeolites for removing CO2 from natural gas, coalbed methane, shale gas, enhanced oil recovery gas, biogas, and landfill gas sources.
Abstract: An efficient computational screening approach is proposed to select the most cost-effective materials and adsorption process conditions for CH4/CO2 separation. The method identifies eight novel zeolites for removing CO2 from natural gas, coalbed methane, shale gas, enhanced oil recovery gas, biogas, and landfill gas sources. The separation cost is minimized through hierarchical material screening combined with rigorous process modeling and optimization. Minimum purity and recovery constraints of 97 and 95%, respectively, are introduced to meet natural gas pipeline specifications and minimize losses. The top zeolite, WEI, can recover methane as economically as $0.15/MMBTU from natural gas with 5% CO2 to $1.44/MMBTU from natural gas with 50% CO2, showing the potential for developing natural gas reservoirs with higher CO2 content. The necessity of a combined material selection and process optimization approach is demonstrated by the lack of clear correlation between cost and material-centric metrics such as adsorption selectivity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1767–1785, 2014
TL;DR: A system-theoretic, control-inspired view and approach to process safety that aims to improve the quality of human experience in the rapidly changing environment.
Abstract: A system-theoretic, control-inspired view and approach to process safety.\" The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters.