Showing papers in "Industrial & Engineering Chemistry Research in 2003"

The Art, Science, and Technology of Charcoal Production†

Abstract: In this review, we summarize the knowledge of the production and properties of charcoal that has been accumulated over the past 38 millenia. The manipulation of pressure, moisture content, and gas flow enables biomass carbonization with fixed-carbon yields that approachor attainthe theoretical limit after reaction times of a few tens of minutes. Much of the heat needed to carbonize the feed is released by vigorous, exothermic secondary reactions that reduce the formation of unwanted tars by augmenting the charcoal yield in a well-designed carbonizer. As a renewable fuel, charcoal has many attractive features: it contains virtually no sulfur or mercury and is low in nitrogen and ash; it is highly reactive yet easy to store and handle. Carbonized charcoal can be a good adsorbent with a large surface area and a semimetal with an electrical resistivity comparable to that of graphite. Recent advances in knowledge about the production and properties of charcoal presage its expanded use as a renewable fuel, red...

Reactive Applications of Cyclic Alkylene Carbonates

Abstract: The synthesis and use of cyclic alkylene carbonates as reactive intermediates first appeared in the literature more than 50 years ago. However, the range of their usefulness in industrial applications has only been fully realized in the past decade. In this article, numerous reactive applications of the cyclic alkylene carbonates, specifically the five-membered cyclics, are discussed. In addition, utilization of the chemistry presented in this review for the preparation of industrially useful monomers, polymers, surfactants, plasticizers, cross-linking agents, curing agents, and solvents, to name a few, is also discussed.

Amine-Grafted MCM-48 and Silica Xerogel as Superior Sorbents for Acidic Gas Removal from Natural Gas

Abstract: In an effort to develop selective solid sorbents for acidic gas (CO2 and H2S) removal from natural gas mixtures, we synthesized amine-surface-modified silica xerogel and MCM-48 materials. With large amounts of basic amine groups on the surface, the sorbents are able to selectively bind the acidic gases CO2 and H2S. High adsorption capacities and adsorption rates were obtained for both gases. The adsorption−desorption isotherms of the gases and thermogravimetric analysis of the sorbents showed that these sorbents can be regenerated completely under mild conditions such as those used in pressure swing or temperature swing adsorption processes. We have also investigated the effect of moisture on the adsorption of CO2 and H2S by TPD-MS and infrared spectroscopy. The results indicated that the presence of water vapor doubled the amount of CO2 adsorbed and barely affected the H2S adsorption.

A Review of CO2 Applications in the Processing of Polymers

Abstract: The use of supercritical carbon dioxide as a processing solvent for the physical processing of polymeric materials is reviewed. Fundamental properties of CO2/polymer systems are discussed with an emphasis on available data and measurement techniques, the development of theory or models for a particular property, and an evaluation of the current state of understanding for that property. Applications such as impregnation, particle formation, foaming, blending, and injection molding are described in detail including practical operating information for selected topics. The review concludes with some forward-looking discussion on the future of CO2 in polymer processing.

The state of the cubic equations of state

Abstract: The development of van der Waals cubic equations of state and their application to the correlation and prediction of phase equilibrium properties is presented and analyzed. The discussion starts with a brief account of the contributions to equation of state development during the years before van der Waals. Then, the original equation proposed in the celebrated thesis of van der Waals in 1873 and its tremendous importance in describing fluid behavior are analyzed. A chronological critical walk through the most important contributions during the first part of the 1900s is made, to arrive at the proposal that I consider to be the most outstanding since van der Waals: the equation proposed by Redlich and Kwong in 1949. The contributions after Redlich and Kwong to the modern development of equations of state and the most recent equations proposed in the literature are analyzed. The application of cubic equations of state to mixtures and the development of mixing rules is put in a proper perspective, and the ...

Rigorous graphical targeting for resource conservation via material recycle/reuse networks

Abstract: Material recycle/reuse is one of the key strategies in reducing the consumption of fresh resources in the process industries. Over the past decade, several techniques have been developed to reduce the consumption of specific material utilities such as water and hydrogen. To date, none of the published techniques provides a noniterative, systematic, and graphical technique for identifying a target for minimum usage of the fresh resources ahead of detailed design of the recycle/reuse network. In this paper, we present a rigorous graphical targeting approach to minimize the use of fresh resources by using segregation, mixing, and direct recycle/reuse strategies. First, the problem is formulated mathematically to provide a systematic basis for its solution. Then, dynamic programming techniques are employed to derive the mathematical conditions and characteristics of an optimal solution strategy. These conditions and characteristics are transformed into a graphical form that can be readily used to identify rig...

Biomass Conversion in Water at 330−410 °C and 30−50 MPa. Identification of Key Compounds for Indicating Different Chemical Reaction Pathways

Abstract: The degradation of biomass is studied in the ranges of 330−410 °C and 30−50 MPa and at 15 min of reaction time. To characterize the chemistry of biomass degradation, key compounds which are interme...

Recent advances in catalysts for methanol synthesis via hydrogenation of CO and CO2

Abstract: Since the start of last century, methanol synthesis has attracted great interests because of its importance in chemical industries and its potential as an environmentally friendly energy carrier. The catalyst for the methanol synthesis has been a key area of research in order to optimize the reaction process. In the literature, the nature of the active site and the effects of the promoter and support have been extensively investigated. In this updated review, the recent progresses in the catalyst innovation, optimization of the reaction conditions, reaction mechanism, and catalyst performance in methanol synthesis are comprehensively discussed. Key issues of catalyst improvement are highlighted, and areas of priority in R&D are identified in the conclusions.

Selective Adsorption for Removing Sulfur from Jet Fuel over Zeolite-Based Adsorbents

Abstract: Adsorbents based on transition metal ion-exchanged Y zeolites (with Cu, Ni, Zn, Pd, and Ce ions) were synthesized and evaluated for the adsorptive desulfurization of a model jet fuel (MJF) and a real jet fuel (JP-8). Among the adsorbents tested, Ce-exchanged Y zeolites exhibited better adsorption capacity of about 10 mg of sulfur/g of adsorbent at 80 °C with a MJF containing 510 ppmw sulfur. The same adsorbent exhibited a sulfur adsorption capacity of about 4.5 mg/g for the real JP-8 jet fuel containing about 750 ppmw sulfur. Desulfurization of MJF under flow conditions at 80 °C showed a breakthrough capacity of about 2.3 mg/g of adsorbent. Ce-exchanged zeolites exhibited higher selectivity for sulfur compounds as compared to the selectivity of aromatics, for which a comparative study indicated that the sulfur compounds are adsorbed over Ce-exchanged Y zeolites via direct sulfur−adsorbent (S−M) interaction rather than via π-complexation. While the selectivity for 2-methyl benzothiophene (2-MBT) was higher...

GC/MS characterization of liquids generated from low-temperature pyrolysis of wood

Abstract: Conventional pyrolysis of beech wood has been carried out for heating temperatures in the range 600−900 K, reproducing conditions of interest in countercurrent fixed-bed gasification. The yields of liquids (water and tars) increase with the heating temperature from about 40 to 55% of dry wood mass, confirming results previously obtained with a laboratory-scale gasifier. Apart from qualitative identification of ∼90 species, GC/MS techniques have been applied to quantify 40−43% of tars (40 species, with major contributions from acetic acid, hydroxypropanone, hydroxyacetaldehyde, levoglucosan, formic acid, syringol, and 2-furaldehyde). Decomposition of holocellulose leads to the formation of furan derivatives and carbohydrates, with a temperature-dominated selectivity toward hydroxyacetaldehyde against levoglucosan. Syringols and guaiacols, originating from primary degradation of lignin, present a maximum for heating temperatures of about 750−800 K whereas, owing to secondary degradation, phenols continuousl...

Color Removal from Wastewater Using Low-Cost Activated Carbon Derived from Agricultural Waste Material

Abstract: An activated carbon was developed from coconut shell fibers, characterized and used for the removal of methylene blue (basic) and methyl orange (acidic) dyes from wastewater successfully. Adsorption studies were carried out at different temperatures, particle size, pH, and adsorbent doses. The adsorption data are correlated with both Langmuir and Freundlich models. The results indicate that the Freundlich model fits the data better as compared to the Langmuir model in terms of regression coefficients. Isotherms have been used to obtain the thermodynamic parameters such as free energy, enthalpy, and entropy of adsorption. The kinetic studies were also conducted, and the adsorption of methylene blue and methyl orange follow the first-order rate equation. Various kinetic parameters such as the mass-transfer coefficient, effective diffusion coefficient, activation energy, and entropy of activation were evaluated to establish the mechanisms. It was concluded that methylene blue adsorption occurs through a film diffusion mechanism at low as well as at higher concentrations, while methyl orange adsorption occurs through film diffusion at low concentration and particle diffusion at high concentrations. The sorption capacity of the developed carbon is comparable to the other available adsorbents, and costwise it is quite cheaper.

Desulfurization of Liquid Fuels by Adsorption via π Complexation with Cu(I)−Y and Ag−Y Zeolites

Abstract: Fixed-bed adsorption using different π-complexation adsorbents for desulfurization of liquid fuels was investigated. Cu(I)−Y (autoreduced Cu(II)−Y), Ag−Y, H−Y, and Na−Y zeolites were used to separa...

Decolorization of Reactive Dye Solutions by Electrocoagulation Using Aluminum Electrodes

Abstract: The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. This paper deals with the batch removal of the reactive textile dye Remazol Red RB 133 from an aqueous medium by the electrocoagulation method using aluminum electrodes. The effects of wastewater conductivity, initial pH, current density, stirring rate, dye concentration, and treatment time on the decolorization efficiency and energy consumption have been investigated. Aluminum hydroxypolymeric species formed during an earlier stage of the operation efficiently remove dye molecules by precipitation, and in a subsequent stage, Al(OH)3 flocs trap colloidal precipitates and make solid−liquid separation easier during the flotation stage. These stages of electrocoagulation must be optimized to design an economically feasible electrocoagulation process.

The Effect of Flow Rate of Compressed Hot Water on Xylan, Lignin, and Total Mass Removal from Corn Stover

Abstract: Flowing hot water through cellulosic biomass offers many promising features for advanced pretreatment, and a better understanding of the mechanisms responsible for flowthrough behavior could allow us to capitalize on its key attributes while overcoming its limitations. In this study, extensive data were developed to show the effect of flow on the fate of hemicellulose, lignin, and total mass for hot-water pretreatment of corn stover in a small tubular flowthrough reactor at 180, 200, and 220 °C. Solubilization of hemicellulose increased with flow, especially at high temperatures; a result that is inconsistent with traditional first-order kinetic models. The dissolved xylan in the hydrolyzate was mostly oligomers over this temperature range, and the fraction as oligomers increased with flow rate. Also of importance, lignin removal increased from less than about 30% for batch reactors to about 75% at high flow rates and was nearly linearly related to hemicellulose release for the flowthrough reactor. These observations suggest that mass transfer or other physical factors, and not strictly first-order homogeneous chemical kinetics, impact hemicellulose hydrolysis. In addition, lignin appears to be released throughout hydrolysis, but its fate may be governed by subsequent precipitation reactions unless it is removed first.

Key Compounds of the Hydropyrolysis of Glucose in Supercritical Water in the Presence of K2CO3

Abstract: Hydropyrolysis of glucose as a model compound for cellulose in hot compressed water in the presence of K2CO3 at temperatures of 400 and 500 °C and pressures of 30 and 50 MPa in the range of 1.8−16.3 min reaction time is conducted to characterize key compounds of the thermochemical conversion {phenols (phenol and cresols), furfurals [methylfurfural and (hydroxymethyl)furfural], organic acids, aldehydes}. To compare the effect of alkali salts on the pyrolysis of glucose and biomass, the experiments are conducted in the presence of K2CO3, while biomass includes usually alkali salts. Hydrothermolysis of glucose in the presence of K2CO3 increases the hydrogen yield and the amount of phenols under these conditions. The formation and the degradation pathways of phenols and the other compounds that are identified are discussed. A simplified reaction scheme for glucose decomposition is given and used to discuss the role of these compounds. The effect of varying properties of supercritical water such as density, di...

Computational and physical performance of a modified PC-SAFT equation of state for highly asymmetric and associating mixtures

Abstract: Two modifications to perturbed-chain statistical associating fluid theory are proposed which simplify the calculation of phase-equilibrium properties for nonassociating and associating systems, polymers, and simple molecules without loss of accuracy. A simple linear extrapolation scheme is proposed to obtain parameters for linear alkanes up to polyethylene. It is shown that computing times are greatly reduced using these modifications and compare favorably with traditional equations of state for nonassociating and associating systems.

Kinetics of Biomass Pyrolysis: a Reformulated Three-Parallel-Reactions Model

Abstract: The thermal decompositions of sugarcane bagasse and waste-wood samples are studied using thermogravimetric analysis. Assuming the addition of three independent parallel decompositions, these corresponding to three pseudocomponents linked to the hemicellulose, cellulose, and lignin, the weight loss associated with the pyrolysis process is simulated. First, an irreversible first-order reaction model is assumed for each pseudocomponent. Results show that the model-simulated curves do not fit well to the experimental data. Consequently, a further kinetic study is carried out for the pure lignin (Kraft alkali lignin), which demonstrates that the pyrolysis of lignin is better described by a third-order reaction rate law. The reformulation of the lignin kinetic model, and its subsequent implementation in the summative model (for the third pseudocomponent), has allowed one to reach a good agreement between simulated and experimental data.

New general continuous-time state-task network formulation for short-term scheduling of multipurpose batch plants

Abstract: A new continuous-time MILP model for the short-term scheduling of multipurpose batch plants is presented. The proposed model relies on the state-task network (STN) approach and addresses the general problem of batch scheduling, accounting for resource (utility) constraints, variable batch sizes and processing times, various storage policies (UIS, FIS, NIS, ZW), batch mixing/splitting, and sequence-dependent changeover times. The key features of the proposed model are the following: (a) a continuous-time representation is used, common for all units; (b) assignment constraints are expressed using binary variables that are defined only for tasks, not for units; (c) start times of tasks are eliminated, so that time-matching constraints are used only for the finish times of tasks; and (d) a new class of valid inequalities that improves the LP relaxation is added to the MILP formulation. Compared to other general continuous time STN formulations, the proposed model is faster. Compared to event-driven formulations, it is more general, as it accounts for resources other than equipment and gives solutions in comparable computational times. The application of the model is illustrated through four example problems.

Removal of Zinc from Aqueous Solutions Using Bagasse Fly Ash − a Low Cost Adsorbent

Abstract: Bagasse fly ash, a sugar industry waste, has been converted into an inexpensive and efficient adsorbent. The product obtained has been characterized and utilized for the removal of zinc from aqueous solutions over a wide range of initial metal ion concentration (3.06 × 10-4 to 3.06 × 10-3 M), contact time (24 h), adsorbent dose (5−20 g L-1), and pH (1.0−6.0). The removal of Zn2+ is 100% at low concentrations, whereas it is 60−65% at higher concentrations at an optimum pH of 4.0, using 10 g L-1 of adsorbent in 6−8 h of equilibration time. The uptake decreases with a rise in temperature indicating the process to be exothermic in nature. Kinetic studies have been performed to understand the mechanism of adsorption. The removal takes place through film diffusion mechanism at lower concentrations (≤1.84 × 10-3 M) and by particle diffusion at higher concentrations (≥ 3.06 × 10-3 M).

Optimization of a Pressure-Swing Adsorption Process Using Zeolite 13X for CO2 Sequestration

Abstract: A pressure-swing adsorption process, which uses zeolite 13X as an adsorbent to recover and sequester carbon dioxide from mixture gas (nitrogen and carbon dioxide), is investigated through dynamic simulation and optimization. The purpose of this paper is to improve the purity of each component by finding optimal values of decision variables with a given power constraint. Langmuir isotherm parameters are calculated from experimental data of zeolite 13X and a general mathematical model consisting of a set of partial differential and algebraic equations and solved in gPROMS. The method of centered finite differences is adopted for the discretization of the spatial domains, and a reduced space SQP method is used for the optimization. As a result, the optimal conditions at cyclic steady state are obtained.

Degradation of Azo-dye Orange II by a Photoassisted Fenton Reaction Using a Novel Composite of Iron Oxide and Silicate Nanoparticles as a Catalyst

Abstract: A novel nanocomposite of iron oxide and silicate, prepared through a reaction between a solution of iron salt and a dispersion of Laponite clay, was used as a catalyst for the photoassisted Fenton degradation of azo-dye Orange II. This catalyst is much cheaper than the Nafion-based catalysts, and our results illustrate that it can significantly accelerate the degradation of Orange II under the irradiation of UV light (λ = 254 nm). An advantage of the catalyst is its long-term stability that was confirmed through using the catalyst for multiple runs in the degradation of Orange II. The effects of the H2O2 molar concentration, solution pH, wavelength and power of the UV light, catalyst loading, and initial Orange II concentration on the degradation of Orange II were studied in detail. In addition, it was also found that discoloration of Orange II undergoes a faster kinetics than mineralization of Orange II and 75% total organic carbons of 0.1 mM Orange II can be eliminated after 90 min in the presence of 1....

Optimal Selection of Controlled Variables

Abstract: This paper considers the selection of controlled variables for the unconstrained degrees of freedom, such that near-optimal operation is achieved with constant setpoints (“self-optimizing control”). From a second-order Taylor approximation around the optimal point, we derive an exact local method. This may be used to find the optimal linear combination of measurements to use as controlled variables. We also derive the approximate singular value rule, which is very useful for quick screening and elimination of poor candidate variables.

Removal of carbon dioxide by absorption in a rotating packed bed

Abstract: The absorption of carbon dioxide from gases containing 1−10 mol % CO2 in a rotating packed bed was investigated in this study. The aqueous solutions of NaOH, monoethanolamine, and 2-amino-2-methyl-1-propanol were used as the absorbents. The overall volumetric mass-transfer coefficient (KGa) was observed as a function of the rotating speed, gas flow rate, liquid flow rate, absorbent concentration, and CO2 concentration. The obtained results indicated that KGa of a rotating packed bed was comparable to a tower packed with the EX packing, implying a great potential of a rotating packed bed applied to the reduction of the greenhouse gas CO2 from the exhausted gases.

Desulfurization of commercial liquid fuels by selective adsorption via π-complexation with Cu(I)-Y zeolite

Abstract: Desulfurization of commercial gasoline and diesel by a π-complexation adsorbent, Cu(I)−Y zeolite, was studied in a fixed-bed adsorber operated at ambient temperature and pressure. The sulfur contents in the effluents were below (or well below) the detection limit using flame photometric detection (FPD), i.e., below 0.28 ppmw sulfur. Thus, these “sulfur-free” fuels are well suited for fuel cell applications. Furthermore, it is demonstrated that using a thin layer of a guard bed (e.g., activated carbon, AC) could significantly increase the sulfur capacities of the π-complexation sorbent. For a feed gasoline containing 335 ppmw sulfur, Cu(I)−Y produced 14.7 cm3 of sulfur-free gasoline/g of sorbent. When using AC as a guard bed, 19.6 cm3 of sulfur-free gasoline/g of combined sorbent was produced. For the case of diesel fuel, 34.3 cm3 of “sulfur-free” diesel was produced per 1 g of combined sorbent. The π-complexation sorbents have proven to be by far the most sulfur-selective as well as having the highest sul...

Esterification of acetic acid with butanol in the presence of ion-exchange resins as catalysts

Abstract: The esterification of acetic acid with n-butanol was studied in the presence of ion-exchange resin catalysts such as Amberlyst-15 to determine the intrinsic reaction kinetics. The effect of various parameters such as temperature, mole ratio, catalyst loading, and particle size was studied. Kinetic modeling was performed to obtain the parameters related to intrinsic kinetics. Pseudohomogeneous, Eley−Rideal, Langmuir−Hinshelwood−Hougen−Watson (LHHW), and modified LHHW models were developed. The kinetics for the side-reaction etherification was also investigated. The rate expressions would be useful in the simulation studies for reactive distillation. The experimental data generated for the reaction under total reflux were validated successfully using the developed rate equation and estimated values of kinetic parameters.

Modeling Copolymer Systems Using the Perturbed-Chain SAFT Equation of State

Abstract: The perturbed-chain SAFT equation of state is extended to heterosegmented molecules and is applied to copolymers with a well-defined (alternating) repeat-unit sequence as well as to systems with a statistical sequence of the monomers in the backbone. Copolymers with a statistical sequence of the constituting repeat units usually require an assumption on the sequence of neighboring repeat units within the chain. A simple approach for defining such repeat-unit arrangements is proposed. Systems containing polyolefine copolymers (poly(ethylene-co-propylene) and poly(ethylene-co-1-butene)) covering the complete range of copolymer composition (including both of the appropriate homopolymers) were modeled in a mixture with solvents. Good results were found for mixtures of copolymer/solvent systems using constant interaction parameters. Copolymers comprising both nonpolar and polar repeat units, for example, poly(ethylene-co-vinyl acetate) and poly(ethylene-co-methyl acrylate), require an interaction parameter cor...

Biomass Gasification in Supercritical Water: Influence of the Dry Matter Content and the Formation of Phenols

Abstract: Biomass was gasified in a continuous stirred tank reactor (CSTR) at 500 °C and various pressures (30−50 MPa), reaction times (1.5−10.5 min), and dry matter contents (1.8−5.4 wt %) of the biomass. These results are compared with the results of experiments in a batch reactor, which was heated to 500 °C with two different heating rates (1 and 3 K/min) using two different dry matter contents (5 and 7.5 wt %). Key compounds for different reaction pathways, in particular phenols, were analyzed. The results concerning the dependence of the dry matter content on the gas formation, total organic carbon content, and phenols concentration are very different. In the CSTR the increase of the dry matter content leads to an increased gas yield, in particular of CH4, and the phenols yield increases. This was not found in the batch reactor. The possible reasons are discussed.

Thermal and Hydrolytic Decomposition of Urea for Automotive Selective Catalytic Reduction Systems: Thermochemical and Practical Aspects

Abstract: An energetic analysis of the thermal decomposition of solid urea and urea solutions is presented, and the results are discussed in view of urea selective catalytic reduction (SCR) for automotive DeNOx systems. Various types of decomposition reactors are possible which differ in their effectiveness to produce ammonia from urea. For reasons of simplicity, the decomposition is usually performed by atomizing urea solutions directly into the hot exhaust. However, this technique suffers from short residence times, leading to incomplete decomposition into ammonia and isocyanic acid and causing a significant performance loss of the SCR catalyst. The thermal decomposition out of the main exhaust stream allows much increased residence times for the process of urea decomposition. A reactor utilizing a partial stream of the exhaust seems particularly promising, especially if such a reactor includes a hydrolyzing catalyst, leading to ammonia practically free from isocyanic acid.

Supported bimetallic cluster catalysts

Abstract: We review synthesis, structural characterization, and catalysis by supported bimetallic clusters. Initial steps in the preparations include (a) adsorption of molecular metal clusters with preformed metal−metal bonds; (b) synthesis in zeolite cages; and (c) adsorption of a metal complex on a supported complex or cluster of another metal. Chemisorption capacities of supported oxophilic metal−noble metal clusters for hydrogen and CO are typically less than those of supported clusters of just the noble metal. Catalytic properties distinguishing supported bimetallic clusters from monometallics include high selectivities for oxygenates in CO hydrogenation and different selectivities for CO vs CC bond hydrogenation. Advantages of precise synthesis with organometallic precursors (smallness and uniformity of the supported clusters with bonds between the two metals) are offset by the expensive preparations and difficulty of catalyst regeneration. Applications of supported bimetallic clusters are most likely in spec...

Some Novel Liquid Partitioning Systems: Water−Ionic Liquids and Aqueous Biphasic Systems

Abstract: Partition coefficients, as values of log P, between water and two room-temperature ionic liquids and between water and an aqueous biphasic system have been correlated with Abraham's solute descriptors to yield linear free energy relationships that can be used to predict further values of log P, to ascertain the solute properties that lead to increased or decreased log P values, and to characterize the partition systems It is shown that, in all three of the systems, an increase in solute hydrogen-bond basicity leads to a decrease in log P and an increase in solute volume leads to an increase in log P For the two ionic liquid systems, an increase in solute hydrogen-bond acidity similarly decreases log P, but for the aqueous biphasic system, solute hydrogen-bond acidity has no effect on log P These effects are rather smaller than those observed in traditional water−solvent systems However, the ionic liquids appear to have an increased affinity for polyaromatic hydrocarbons as compared to traditional orga