Showing papers in "Industrial & Engineering Chemistry Research in 2009"

Methods for Pretreatment of Lignocellulosic Biomass for Efficient Hydrolysis and Biofuel Production

Abstract: Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...

Membrane Gas Separation: A Review/State of the Art

Abstract: In the last years membrane processes for gas separation are gaining a larger acceptance in industry and in the market are competing with consolidated operations such as pressure swing absorption and cryogenic distillation. The key for new applications of membranes in challenging and harsh environments (e.g., petrochemistry) is the development of new tough, high performance materials. The modular nature of membrane operations is intrinsically fit for process intensification, and this versatility might be a decisive factor to impose membrane processes in most gas separation fields, in a similar way as today membranes represent the main technology for water treatment. This review highlights the most promising areas of research in gas separation, by considering the materials for membranes, the industrial applications of membrane gas separations, and finally the opportunities for the integration of membrane gas separation units in hybrid systems for the intensification of processes.

Identification of Sulfate and Hydroxyl Radicals in Thermally Activated Persulfate

Abstract: Thermal activation can induce persulfate (S2O82−) degradation to form sulfate radicals (SO4−•) that can undergo radical interconversion to form hydroxyl radicals (HO•) under alkaline conditions. The radicals SO4−•/HO• can be present either individually or simultaneously in the persulfate oxidation system. To identify the active radical species, a chemical probe method was developed. An excess of probe compounds was added to the system, and differences between the reactivity of the probes and the potential radical species were observed. The usage of various probes, including tert-butyl alcohol, phenol, and nitrobenzene (NB), for simultaneously identifying SO4−•/HO• was investigated. NB can only react with radicals: it cannot react with persulfate. The reaction rate of NB with HO• is 3000−3900 times greater than that of NB with SO4−•, which is a good candidate for use as a probe for differentiating between SO4−•/HO• reactivity. Furthermore, the effects of pH on the formation of SO4−•/HO• were demonstrated b...

Guide to CO2 Separations in Imidazolium-Based Room-Temperature Ionic Liquids

Abstract: Room-temperature ionic liquids (RTILs) are nonvolatile, tunable solvents that have generated significant interest across a wide variety of engineering applications. The use of RTILs as media for CO2 separations appears especially promising, with imidazolium-based salts at the center of this research effort. The solubilities of gases, particularly CO2, N2, and CH4, have been studied in a number of RTILs. Process temperature and the chemical structures of the cation and anion have significant impacts on gas solubility and gas pair selectivity. Models based on regular solution theory and group contributions are useful to predict and explain CO2 solubility and selectivity in imidazolium-based RTILs. In addition to their role as a physical solvent, RTILs might also be used in supported ionic liquid membranes (SILMs) as a highly permeable and selective transport medium. Performance data for SILMs indicates that they exhibit large permeabilities as well as CO2/N2 selectivities that outperform many polymer membra...

Hydrotreatment of Fast Pyrolysis Oil Using Heterogeneous Noble-Metal Catalysts

Abstract: Fast pyrolysis oils from lignocellulosic biomass are promising second-generation biofuels. Unfortunately, the application range for such oils is limited because of the high acidity (pH∼2.5) and the presence of oxygen in a variety of chemical functionalities, and upgrading of the oils is required for most applications. Herein, we report an experimental study on the upgrading of fast pyrolysis oil by catalytic hydrotreatment. A variety of heterogeneous noble-metal catalysts were tested for this purpose (Ru/C, Ru/TiO2, Ru/Al2O3, Pt/C, and Pd/C), and the results were compared to those obtained with typical hydrotreatment catalysts (sulfided NiMo/Al2O3 and CoMo/Al2O3). The reactions were carried out at temperatures of 250 and 350 °C and pressures of 100 and 200 bar. The Ru/C catalyst was found to be superior to the classical hydrotreating catalysts with respect to oil yield (up to 60 wt %) and deoxygenation level (up to 90 wt %). The upgraded products were less acidic and contained less water than the original...

Structure, energy, synergy, time - the fundamentals of Process Intensification

Abstract: Process intensification (PI) is commonly seen as one of the most promising development paths for the chemical process industry and one of the most important progress areas for modern chemical engineering. Often illustrated with spectacular examples, process intensification struggles, however, with its definition and interpretation. Instead of narrowing the scientific discussion down to finding a commonly accepted definition of PI, it is more important to determine its position within chemical engineering and to identify its fundamentals. Accordingly, the paper presents a fundamental vision on process intensification. The vision encompasses four approaches in spatial, thermodynamic, functional, and temporal domains, which are used to realize four generic principles of PI. The approaches refer to all scales existing in chemical processes, from molecular to meso- and macroscale, and are illustrated with relevant examples with special attention given to the molecular scale.

Clathrate Hydrates: From Laboratory Science to Engineering Practice

Abstract: Clathrate hydrates have steadily emerged as an important field in the areas of flow assurance, energy storage and resource, and environment. To better understand the role of hydrates in all of these areas, knowledge developed in laboratory experiments must be effectively transferred to address the challenges related to hydrate formation, dissociation, agglomeration, and stability. This paper highlights the recent hydrate literature focusing on the thermodynamics, kinetics, structural properties, particle properties, rheological properties, and molecular mechanisms of formation. The foundation for continued understanding and development of hydrates in engineering practice will rely on laboratory measurements utilizing traditional and innovative tools capable of probing time-dependent and time-independent properties.

State-of-the-Art Review of Pinch Analysis Techniques for Water Network Synthesis

Abstract: Water network synthesis has been an active area of research for the past one and a half decades. Many think that the technology reached a mature stage in the late 1990s, especially for the insight-based technique based on pinch analysis. The only review for the field dates back to 2000. However, many new papers published in this century reveal that new research gaps are found and more works were carried out to address the limitations of the “old” techniques. The main objective of this review is to provide a state-of-the-art overview of the insight-based techniques developed in the 21st century, particularly those developed for single impurity network of the fixed flow rate problems. Comparisons were also made between these recent techniques and those developed for the fixed load problems in the past century. Various flow rate targeting techniques developed for water reuse/recycle, regeneration, and wastewater treatment are reviewed in detail, along with the network design techniques that achieve the estab...

Adsorption and Diffusion of Carbon Dioxide on Metal−Organic Framework (MOF-5)

Abstract: Adsorption equilibrium and diffusion of CO2 on microporous metal−organic frameworks (MOF-5, or IRMOF-1) crystals were experimentally studied by the gravimetric method in the pressure range up to 1 atm. The MOF-5 crystal cubes of about 40−60 μm in sizes were synthesized by the solvothermal method. Freundlich adsorption isotherm equation can fit well CO2 adsorption isotherms on MOF-5, with isosteric heat of adsorption of about 34 kJ/mol. Diffusion coefficient of CO2 in the MOF-5 is in the range of 8.1−11.5 × 10−9 cm2/s in 295−331K with activation energy of 7.61 kJ/mol. MOF-5 offers attractive adsorption properties as an adsorbent for separation of CO2 from flue gas.

New Amines for CO2 Capture. I. Mechanisms of Amine Degradation in the Presence of CO2

Abstract: Degradation of 12 different amines with CO2 was evaluated in 100 mL stainless steel batch reactors for 15 days at 140 °C using a 4 mol·kg−1 amine solution and a CO2 pressure of 2 MPa. At the end of the run, most of degradation products were identified by gas chromatography (GC)/mass spectrometry (MS); amounts of starting amine and its degradation products were determined with a quantitative GC method. This work compares the degradation of ethanolamines (including MEA) having one or two hydroxyl groups with the degradation of ethylenediamines. They were chosen to establish relationships between amine structure and stability properties: replacement of one alcohol function by one amine function, effect of amine function nature, impact of steric hindrance and cyclic structure. Significant differences were observed. The main degradation products are described, and some mechanisms are proposed to explain their formation.

Ion-Exchange Resins: A Retrospective from Industrial and Engineering Chemistry Research

Abstract: Ion-exchange resins comprise one of the most important scientific developments of the 20th century. Their applicability to water softening, environmental remediation, wastewater treatment, hydrometallurgy, chromatography, biomolecular separations, and catalysis was recognized in numerous publications. The principle of covalently bonding ligands to cross-linked polymer networks became the basis for the area of polymer-supported reagents. The journal Industrial & Engineering Chemistry Research and its predecessors have published some of the most important papers in this field. In celebration of its 100th anniversary, this review provides a retrospective of ion-exchange resins through publications appearing in this journal.

Progress, Opportunities, and Challenges for Applying Atomically Detailed Modeling to Molecular Adsorption and Transport in Metal−Organic Framework Materials

Abstract: Metal−organic framework (MOF) materials are a class of nanoporous materials that have many potential advantages over traditional nanoporous materials for adsorption and other chemical separation technologies. Because of the large number of different MOFs that exist, efforts to predict the performance of MOFs using molecular modeling can potentially play an important role in selecting materials for specific applications. We review the current state-of-the-art in the molecular modeling and quantum mechanical modeling of MOFs. Quantum mechanical calculations have been used to date to examine structural and electronic properties of MOFs and the calculation of MOF−guest interactions. Molecular modeling calculations using empirical classical potential calculations have been used to study pure and mixed fluid adsorption in MOFs. Similar calculations have recently provided initial information about the diffusive transport of adsorbed fluids in MOFs.

Critical Properties of Ionic Liquids. Revisited

Abstract: The group contribution method proposed by Valderrama and Robles in 2007 and extended by Valderrama et al. in 2008 to estimate the critical properties of ionic liquids is revised and new groups have been included. The method originally proposed has been used by several authors in applications such as high pressure phase equilibrium, density correlations, heat capacity estimations, and consistency tests for mixture data. Therefore, it is important to have a consistent and reliable method so all applications consider the same assumptions and values for the critical properties. The values previously reported by the authors are recalculated, unifying criteria for the names of the ionic liquids, for the assignment of the groups forming the molecules, and for the equivalence of groups. Also, a spreadsheet file that allows any reader to calculate the critical properties of any ionic liquid containing the 44 groups defined by the method is provided as Supporting Information.

Preparation and Characterization of Cellulose Nanofibers from Two Commercial Hardwood and Softwood Pulps

Abstract: The aim of this work was to study the mechanical fibrillation process for the preparation of cellulose nanofibers from two commercial hard- and softwood cellulose pulps. The process consisted of in...

Assessment of Options for Selective 1-Butanol Recovery from Aqueous Solution

Abstract: The microbial production of 1-butanol occurs in aqueous fermentation broth, with up to ∼20 g/L of product. Efficient recovery of butanol from this dilute aqueous phase determines, to a large extent, the efficiency of the production process. Starting from the thermodynamic (phase) properties of butanol and water systems, this paper presents a structured approach to determine the key characteristics of various butanol recovery methods. Analysis of reported separations, combined with fundamental phase properties, has resulted in both the characterization of the selectivity of recovery and estimations of the energy requirement during product recovery for a variety of recovery methods. Energy-efficient systems for the recovery of butanol from aqueous solution are pervaporation- and adsorption-based techniques. The applied method predicts the recovery energy requirement for both techniques to be <4 MJ/kg of butanol, which, on an energy basis, is similar to ∼10% of the internal combustion energy of butanol.

Rate-Based Process Modeling Study of CO2 Capture with Aqueous Monoethanolamine Solution

Abstract: Rate-based process modeling technology has matured and is increasingly gaining acceptance over traditional equilibrium-stage modeling approaches. [Taylor et al. Chem. Eng. Prog. 2003, 99, 28−39] Recently comprehensive pilot plant data for carbon dioxide (CO2) capture with aqueous monoethanolamine (MEA) solution have become available from the University of Texas at Austin. The pilot plant data cover key process variables including CO2 concentration in the gas stream, CO2 loading in lean MEA solution, liquid to gas ratio, and packing type. In this study, we model the pilot plant operation with Aspen RateSep, a second generation rate-based multistage separation unit operation model in Aspen Plus. After a brief review on rate-based modeling, thermodynamic and kinetic models for CO2 absorption with the MEA solution, and transport property models, we show excellent match of the rate-based model predictions against the comprehensive pilot plant data and we validate the superiority of the rate-based models over t...

UNIFAC Model for Ionic Liquids

Abstract: This work focuses on the extension of group parameters of the UNIFAC model to systems with ionic liquids. The new group parameters for ionic liquids were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ionic liquids at different temperatures. The group parameters for 12 main groups and 24 subgroups were added into the current UNIFAC parameter matrix. It was verified that the new group parameters can be used not only for predicting the vapor−liquid equilibria of the systems with ionic liquids at finite concentration, but also for screening the suitable ionic liquids in separation processes. Since there have been only a limited number of functional groups for ionic liquids included in the UNIFAC model, the future development of this predictive model will still require much more accurate experimental data.

Modifier-Adaptation Methodology for Real-Time Optimization

Abstract: The process industries are characterized by a large number of continuously operating plants, for which optimal operation is of economic importance. However, optimal operation is particularly difficult to achieve when the process model used in the optimization is inaccurate or in the presence of process disturbances. In highly automated plants, optimal operation is typically addressed by a decision hierarchy involving several levels that include plant scheduling, real-time optimization (RTO), and process control. At the RTO level, medium-term decisions are made by considering economic objectives explicitly. This step typically relies on an optimizer that determines the optimal steady-state operating point under slowly changing conditions such as catalyst decay or changes in raw material quality. This optimal operating point is characterized by setpoints that are passed to lower-level controllers. Model-based RTO typically involves nonlinear first-principles models that describe the steady-state behavior of the plant. Since accurate models are rarely available in industrial applications, RTO typically proceeds using an iterative two-step approach, namely a parameter estimation step followed by an optimization step. The idea is to repeatedly estimate selected uncertain model parameters and use the updated model to generate new inputs via optimization. This way, the model is expected to yield a better description of the plant at its current operating point. The classical two-step approach works well provided that (i) there is little structural plant-model mismatch, and (ii) the changing operating conditions provide sufficient excitation for estimating the uncertain model parameters. Unfortunately, such conditions are rarely met in practice and, in the presence of plant-model mismatch, the algorithm might not converge to the plant optimum, or worse, to a feasible operating point. As far as feasibility is concerned, the updated model should be able to match the plant constraints. Alternatively, feasibility can be enforced without requiring the solution of a parameter estimation problem by adding plant-model bias terms to the model outputs. These biases are obtained by subtracting the model outputs from the measured plant outputs. A bias-update scheme, where the bias terms are used to modify the constraints in the steady-state optimization problem, has been used in industry. However, the analysis of this scheme has received little attention in the research community. In the context of this thesis, such an RTO scheme is referred to as constraint adaptation. The constraint-adaptation scheme is studied, and its local convergence properties are analyzed. Constraint adaptation guarantees reaching a feasible operating point upon convergence. However, the constraints might be violated during the iterations of the algorithm, even when starting the adaptation from within the feasible region. Constraint violations can be avoided by controlling the constraints in the optimization problem, which is done at the process control level by means of model predictive control (MPC). The approach for integrating constraint adaptation with MPC described in this thesis places high emphasis on how constraints are handled. An alternative constraint-adaptation scheme is proposed, which permits one to move the constraint setpoints gradually in the constraint controller. The constraint-adaptation scheme, with and without the constraint controller, is illustrated in simulation through the real-time optimization of a fuel-cell system. It is desirable for a RTO scheme to achieve both feasibility and optimality. Optimality can be achieved if the underlying process model is able to predict not only the constraint values of the plant, but also the gradients of the cost and constraint functions. In the presence of structural plant-model mismatch, this typically requires the use of experimental plant gradient information. Methods integrating parameter estimation with a modified optimization problem that uses plant gradient information have been studied in the literature. The approach studied in this thesis, denoted modifier adaptation, does not require parameter estimation. In addition to the modifiers used in constraint adaptation, gradient-modifier terms based on the difference between the estimated and predicted gradient values are added to the cost and constraint functions in the optimization problem. With this, a point that satisfies the first-order necessary conditions of optimality for the plant is obtained upon convergence. The modifier-adaptation scheme is analyzed in terms of model adequacy and local convergence conditions. Different filtering strategies are discussed. The constraint-adaptation and modifier-adaptation RTO approaches are illustrated experimentally on a three-tank system. Finite-difference techniques can be used to estimate experimental gradients. The dual modifier-adaptation approach studied in this thesis drives the process towards optimality, while paying attention to the accuracy of the estimated gradients. The gradients are estimated from the successive operating points generated by the optimization algorithm. A novel upper bound on the gradient estimation error is developed, which is used as a constraint for locating the next operating point.

Photocatalytic Degradation of Methylene Blue Dye Using Ultraviolet Light Emitting Diodes

Abstract: This study was focused on the application of ultraviolet light emitting diodes (UV-LED) as an alternate source for the photocatalytic degradation of methylene blue (MB), which was used as a model compound. A simple reactor arrangement was made to carry out the photocatalytic degradation of methylene blue dye. The photocatalytic activity of P-25 Degussa TiO2 was evaluated using UV-LED reactor. The decomposition of MB dye in aqueous solution by TiO2 photocatalytic process with the UV-LED was found to be technically feasible. The effects of various parameters such as catalyst loading, initial dye concentration, pH, and addition of H2O2 on decolorization and degradation have been investigated to find the optimum conditions. The complete mineralization of MB dye (3.12 × 10−5 M) was confirmed by chemical oxygen demand analysis. Results demonstrated that the UV-LED/TiO2 process can effectively degrade methylene blue dye with optimum conditions.

Optimization study of lignin oxypropylation in view of the preparation of polyurethane rigid foams

Abstract: Contract grant sponsor: Portuguese Foundation for Science and Technology; contract grant number: SFRH/BD/ 18415/2004. Contract grant sponsor: French–Portuguese Scientific Cooperation Programme; contract grant number: F-13/06. Contract grant sponsor: European Commission (through a Marie Curie Intra-European Fellowship to W.T.); contract grant number: MEIF-CT-2005-025125.

New Amines for CO2 Capture. II. Oxidative Degradation Mechanisms

Abstract: This study examines oxidative degradation of 12 ethanolamines and ethylenediamines. They were chosen to establish structure−property relationships: the role of replacement of the alcohol function by one second amine function, amine nature, steric hindrance, and cyclic structure were studied. Degradation of aqueous amine solutions was evaluated at 140 °C under air pressure (2 MPa) in stainless steel reactors for 15 days. At the end of the run, most degradation products were identified by gas chromatography (GC)/mass spectrometry (MS); amounts of remaining amine and its degradation products were determined with the quantitative GC method. Main degradation mechanisms are proposed, and some relationships between structure and chemical stability are given.

Seed-Induced Crystallization of Nanosized Na-ZSM-5 Crystals

Abstract: ZSM-5 nanocrystals were synthesized from organic-template-free gel systems containing 0.1, 1.0, and 3.0 wt % of 80 nm silicalite-1 seeds. The syntheses were performed at 100, 120, 150, and 170 °C for periods of time ranging between 3 and 190 h. Physicochemical characteristics derived from XRD, NMR, TG/DTA, SEM/TEM, DLS, N2 adsorption and chemical analyses of Na-ZSM-5 nanocrystals were compared with those of the nanosized tetrapropylammonium (TPA)-promoted counterpart. Crystalline yield and colloidal stability of ZSM-5 nanosized materials obtained under different conditions (seed content, crystallization temperature, and time) were also studied. Another issue of interest in the framework of this study was the effect of seed pretreatment (drying, calcination) on the characteristics of crystalline product. Thus, factors controlling seeded growth of nanosized zeolite particles were established and the mechanism of formation, including parameters governing the formation of single or aggregated crystals, revealed.

Microstructured Reactors for Multiphase Reactions: State of the Art

Abstract: The manufacture of chemicals in microstructured reactors (MSR) has become recently a new branch of chemical reaction engineering focusing on process intensification and safety. MSR have an equivalent hydraulic diameter up to a few hundreds of micrometers and, therefore, provide high mass- and heat-transfer efficiency increasing the reactor performance drastically, compared to the conventional one. This article provides a comprehensive overview of the state of the art of the MSR applied for multiphase reactions. The reactions are classified based on the number of phases involved: fluid−fluid, fluid−solid, and three phase reactions. In the first part of the review, limitations of conventional reactors are discussed in brief. Furthermore, different types of MSR and their advantages with respect to their conventional counterparts are described. Particular attention is given to the identification of the parameters that control the flow pattern formed in microcapillaries regarding the mass-transfer efficiency. ...

Pretreatment of Miscanthus x giganteus Using the Ethanol Organosolv Process for Ethanol Production

Abstract: A two-step procedure involving a dilute-acid presoaking step and an aqueous-ethanol organosolv treatment has been evaluated and optimized for the conversion of Miscanthus x giganteus (MxG). This process allowed for the efficient fractionation of the raw material into a cellulose-rich residue, an ethanol organosolv lignin fraction, and a water-soluble fraction mainly containing hemicellulose sugars. It was found that the presoaking step not only allowed a better recovery of xylans, but also enhanced the dissolution of lignin in the aqueous ethanol and the digestibility of the remaining cellulose by enzymes. The optimized conditions yielded a solid residue containing about 95% of the initial glucans, from which 98% was recovered after 48 h of enzymatic hydrolysis. In addition, 71% of the lignin was recovered as ethanol organosolv lignin (EOL), and the recovery of the xylans was equivalent to 73% of the xylose present in the raw Miscanthus.

Review of Major Design and Scale-up Considerations for Solar Photocatalytic Reactors

Abstract: Photocatalytic processes are applicable in wastewater treatment, energy production, chemical synthesis, and greenhouse gas mitigation and thus have the potential to address both the consumption of nonrenewable fossil fuels and global warming, two of the greatest problems facing humankind. The ability to achieve these outcomes using only solar energy as an input is particularly attractive. However, the implementation of most photocatalytic processes at an effective scale requires the use of a photoreactor, a device which brings photons, a photocatalyst and reactants into contact, as well as collecting the reaction products. In this work, we review the state-of-the-art in solar photoreactor design and assess those systems which are most applicable for industrial-scale implementation. Designs for parabolic trough, compound parabolic, inclined plate, double skin sheet, rotating disk, water bell, fiber optic, and fixed/fluidized bed photoreactors are qualitatively discussed and compared. Compound parabolic pho...

Milking Diatoms for Sustainable Energy: Biochemical Engineering versus Gasoline-Secreting Diatom Solar Panels

Abstract: In the face of increasing CO2 emissions from conventional energy (gasoline), and the anticipated scarcity of Crude oil, a worldwide effort is underway for cost-effective renewable alternative energy sources. Here, we review a simple line of reasoning: (a) geologists claim that Much crude oil comes from diatoms; (b) diatoms do indeed make oil; (c) agriculturists Claim that diatoms could make 10-200 times as much oil per hectare as oil seeds; and (d) therefore, sustainable energy could be made from diatoms. In this communication, we propose ways of harvesting oil from diatoms, using biochemical engineering and also a new solar panel approach that utilizes genomically modifiable aspects of diatom biology, offering the prospect of ``milking'' diatoms for Sustainable energy by altering them to actively secrete oil products. Secretion by and milking of diatoms may provide a way around the puzzle of how to make algae that both grow quickly and have a very high oil content.

Effect of Thermodynamic Restriction on Energy Cost Optimization of RO Membrane Water Desalination

Abstract: Advances in highly permeable reverse osmosis (RO) membranes have enabled desalting operations, in which it is practically feasible for the applied pressure to approach the osmotic pressure of the exit brine stream. However, energy cost remains a major contributor to the total cost of water produced by RO membrane desalination. Reduction of the overall cost of water production represents a major challenge and, in the present work, various elements of water production cost are evaluated from the viewpoint of optimization, with respect to various costs (energy, membrane area and permeability, brine management, and pressure drop), as well as the important thermodynamic cross-flow constraint, utilization of energy recovery devices, and operational feed and permeate flow rate constraints. More specifically, in the present study, an approach to the optimization of product water recovery at pressures that approach the osmotic pressure of the exit brine stream is presented via several simple RO process models that...

Hydrolysis and Decomposition of Cellulose in Brönsted Acidic Ionic Liquids Under Mild Conditions

Abstract: Cellulose dissolves in Bronsted acidic ionic liquids 1-(1-propylsulfonic)-3-methylimidazolium chloride and 1-(1-butylsulfonic)-3-methylimidazolium chloride up to 20 g/100 g ionic liquid by gentle m...

Underground Coal Gasification: A Brief Review of Current Status

Abstract: Coal gasification is a promising option for the future use of coal. Similarly to gasification in industrial reactors, underground coal gasification (UCG) produces syngas, which can be used for power generation or for the production of liquid hydrocarbon fuels and other valuable chemical products. As compared with conventional mining and surface gasification, UCG promises lower capital/operating costs and also has other advantages, such as no human labor underground. In addition, UCG has the potential to be linked with carbon capture and sequestration. The increasing demand for energy, depletion of oil and gas resources, and threat of global climate change lead to growing interest in UCG throughout the world. In this article, we review the current status of this technology, focusing on recent developments in various countries.

Controlling Particle Size of a Poorly Water-Soluble Drug Using Ultrasound and Stabilizers in Antisolvent Precipitation

Abstract: The objective of this work was to develop a better understanding of a potentially scalable, liquid antisolvent (LAS) precipitation process, for the preparation of stable aqueous suspensions of ultrafine particles of poorly water-soluble active pharmaceutical ingredients (APIs). A novel combination of jets, ultrasound, polymers, and surfactants was used for the precipitation and stabilization of ultrafine particles of griseofulvin (GF). Use of ultrasound and high stream velocities enhances micromixing, whereas addition of polymers/surfactants inhibits/lowers the particle growth. A combination of ultrasound, high jet velocities, and stabilizers decreased the GF particle size to 1.04 μm (±0.46 μm) from 30.8 μm (±14.2 μm), when none of the treatments were used. A rational understanding was developed for predicting process performance and selecting suitable particle growth inhibitors/stabilizers. Favorable process conditions and combinations of polymer and surfactants were also identified experimentally for th...