Showing papers in "Industrial & Engineering Chemistry Research in 2010"

Thermophysical Properties of Pure Ionic Liquids: Review of Present Situation

Abstract: The large collection of thermophysical properties data for liquids available in the open literature is analyzed, describing its importance for industrial purposes. Although there has been a boom of thermophysical properties measurements for these fluids in the past decade, the reported analysis shows that studies have been centered on a limited number of fluids, whereas data collection for the new family ionic liquids is lacking. Measurements have been performed for limited temperature ranges, and pressure effects on the properties are extremely scarce in the literature; remarkable differences among data from different literature sources are reported. The need of sample purity quantification is analyzed together with the strong effect of these impurities on thermophysical properties. Available predictive models for the studied properties are analyzed together with the quality of their predictions. The main conclusion of this review is to point out the need of further systematic thermophysical studies, inc...

Model Predictive Control Tuning Methods: A Review

Abstract: This paper provides a review of the available tuning guidelines for model predictive control, from theoretical and practical perspectives. It covers both popular dynamic matrix control and generalized predictive control implementations, along with the more general state-space representation of model predictive control and other more specialized types, such as max-plus-linear model predictive control. Additionally, a section on state estimation and Kalman filtering is included along with auto (self) tuning. Tuning methods covered range from equations derived from simulation/approximation of the process dynamics to bounds on the region of acceptable tuning parameter values.

Highly Water-Soluble Magnetic Nanoparticles as Novel Draw Solutes in Forward Osmosis for Water Reuse

Abstract: Highly hydrophilic magnetic nanoparticles have been molecularly designed. For the first time, the application of highly water-soluble magnetic nanoparticles as novel draw solutes in forward osmosis (FO) was systematically investigated. Magnetic nanoparticles functionalized by various groups were synthesized to explore the correlation between the surface chemistry of magnetic nanoparticles and the achieved osmolality. We verified that magnetic nanoparticles capped with polyacrylic acid can yield the highest driving force and subsequently highest water flux among others. The used magnetic nanoparticles can be captured by the magnetic field and recycled back into the stream as draw solutes in the FO process. In addition, magnetic nanoparticles of different diameters were also synthesized to study the effect of particles size on FO performance. We demonstrate that the engineering of surface hydrophilicity and magnetic nanoparticle size is crucial in the application of nanoparticles as draw solutes in FO. It i...

Double-Skinned Forward Osmosis Membranes for Reducing Internal Concentration Polarization within the Porous Sublayer

Abstract: A scheme to fabricate forward osmosis membranes comprising a highly porous sublayer sandwiched between two selective skin layers via phase inversion was proposed. One severe deficiency of existing composite and asymmetric membranes used in forward osmosis is the presence of unfavorable internal concentration polarization within the porous support layer that hinders both (i) separation (salt flux) and (ii) the performance (water flux). The double skin layers of the tailored membrane may mitigate the internal concentration polarization by preventing the salt and other solutes in the draw solution from penetrating into the membrane porous support. The prototype double-skinned cellulose acetate membrane displayed a water flux of 48.2 L·m−2·h−1 and lower reverse salt transport of 6.5 g·m−2·h−1 using 5.0 M MgCl2 as the draw solution in a forward osmosis process performed at 22 °C. This can be attributed to the effective salt rejection by the double skin layers and the low water transport resistance within the p...

Catalytic and Non-catalytic Supercritical Water Gasification of Microalgae and Glycerol

Abstract: In this study, we present the gasification of microalgae (Chlorella vulgaris) and glycerol in supercritical water (SCW) using batch (quartz capillaries) and continuous flow reactors. Preliminary tests of algae gasification were done with quartz capillaries at varying operating conditions such as temperature (400−700 °C), reaction time (1−15 min), and the addition of catalysts. The dry gas composition of uncatalyzed gasification of algae in SCW mainly comprised of CO2, CO, CH4, H2, and some C2−C3 compounds. Higher temperatures, low algae concentrations, and longer residence times favored the algae gasification efficiency (GE). The addition of catalysts to the capillaries resulted in higher yields of hydrogen and lower CO yields via enhanced water−gas shift activity. The addition of catalysts accelerated the gasification efficiency up to a maximum of 84% at 600 °C and 2 min reaction time with nickel-based catalysts. Complete gasification is achieved at higher temperatures (700 °C) and with excess amounts of (Ru/TiO2) catalyst. To elucidate part of the difficulties related to the SCWG of algae, reforming of a model compound (here glycerol) in SCW was carried out in a continuous flow reactor in the presence of additives like amino acids (l-alanine, glycine, and l-proline) and alkali salt (K2CO3) and combinations thereof. The amino acids l-alanine and glycine have a minor effect on the gasification process of glycerol, and a significant reduction of the gasification efficiency was observed in the presence of l-proline. Coke formation and colorization of the reactor effluent were more noticeable with glycerol−amino acid mixtures. In the absence of amino acids, the glycerol solution gasified without any coke formation and colorization of the reactor effluent. Again this effect was more pronounced in the presence of l-proline. The addition of K2CO3 enhanced the glycerol gasification efficiency and increased the hydrogen yields promoting the water−gas shift reaction.

Ionic Liquids for Aromatics Extraction. Present Status and Future Outlook

Abstract: Ionic liquids (ILs) can be used to replace conventional solvents in liquid−liquid extractions of aromatic hydrocarbons. An IL-based extraction process requires fewer process steps and less energy consumption, provided that the mass-based aromatic distribution coefficient and/or the aromatic/aliphatic selectivity are higher than those of the current state-of-the-art solvents such as sulfolane. Only a small number of ionic liquids are able to combine higher mass-based distribution coefficients with selectivities comparable to or higher than those of sulfolane. The most suitable ILs from our analysis are [bmim]C(CN)3, [3-mebupy]N(CN)2, [3-mebupy]C(CN)3, and [3-mebupy]B(CN)4. The mass-based distribution coefficients with these four ILs for benzene, toluene, and p-xylene are factors of 1.2−2.5 higher than those with sulfolane, and the aromatic/aliphatic selectivities are up to a factor of 1.9 higher than with sulfolane. Based on the performed analysis, it can be concluded that industrial application of ILs for...

Adsorption of CO2-Containing Gas Mixtures over Amine-Bearing Pore-Expanded MCM-41 Silica: Application for Gas Purification

Abstract: Adsorption of CO 2 on triamine-grafted pore-expanded mesoporous silica, TRI-PE-MCM-41, was investigated from very low pressure to 1 bar at four temperatures (298, 308, 318, 328 K) using gravimetric measurements. TRI-PE-MCM-41 exhibited one of the highest equilibrium capacities compared to other typical CO 2 adsorbents such as zeolites, activated carbons, and metal-organic frameworks (MOFs). In contrast, under the same pressure and temperature conditions, TRI-PE-MCM-41 exhibited very small uptakes of N 2 , CH 4 , H 2 , and O 2 . Column-breakthrough measurements of CO 2 in mixtures with other species showed exceedingly high selectivity of CO 2 over N 2 , CH 4 , H 2 , and O 2 even at very low CO 2 concentrations, indicating that TRI-PE-MCM-41 is suitable adsorbent for gas purification applications. Moreover, water vapor was found to have a beneficial effect on CO 2 adsorption capacity even at very low CO 2 partial pressure, e.g. 400 ppm, without adverse effect on CO 2 selectivity.

Gas Permeation Behavior of Pebax-1657 Nanocomposite Membrane Incorporated with Multiwalled Carbon Nanotubes

Abstract: Incorporation of multiwalled carbon nanotubes (MWNT) on the gas permeation properties of H2, CO2, O2, and N2 gases in poly(ether-block-amide) (Pebax-1657) membrane has been investigated. Pebax-1657 was dissolved in the ethanol−water mixture and cast on an ultraporous polyethersulfone substrate followed by complete solvent evaporation. Nanocomposite membranes were prepared by dispersion of MWNT in concentrations of 0−5% of polymer weight in the Pebax solutions with sonication for 2 h to ensure uniformity. Cross-linking was carried out in hexane medium using 2,4-toluylene diisocyanate (TDI). The permeabilities of pure gases were measured at room temperature, and the ideal selectivities were determined at pressures varying from 1−3 MPa using an indigenously built high-pressure gas separation manifold. For neat Pebax membrane, high permeabilities of 55.8 and 32.1 barrers were observed for CO2 and H2 gases, respectively, whereas that of N2 was as low as 1.4 barrers. The selectivity of cross-linked 2% MWNT Peba...

Investigation of Immiscible and Miscible Foam for Enhancing Oil Recovery

Abstract: We report the study of flow of CO2 and N2 foam in natural sandstone cores containing oil with the aid of X-ray computed tomography The study is relevant for enhanced oil recovery (EOR) The cores were partially saturated with oil and brine (half top) and brine only (half bottom) to mimic the water−oil transition occurring in oil reservoirs The CO2 was used either under subcritical conditions (P = 1 bar) or under supercritical (immiscible (P = 90 bar) and miscible (P = 137 bar)) conditions, whereas N2 remained subcritical Prior to gas injection the cores were flooded with several pore volumes of water In a typical foam experiment water flooding was followed by the injection of 1−2 pore volumes of a surfactant solution with alpha olefin sulfonate (AOS) as the foaming agent We visually show how foam propagates in a porous medium containing oil At low-pressure experiments (P = 1 bar) in the case of N2, weak foam could be formed in the oil-saturated part Diffused oil bank is formed ahead of the foam fro

Mechanistic Assessment of Microalgal Lipid Extraction

Abstract: In this paper, we have attempted to make a comparative assessment of the three techniques for extraction of lipids from microalgal biomass, viz. Soxhlet extraction, the Bligh and Dyer method, and sonication. The approach is mechanistic in the sense that we have tried to determine the physical mechanism of extraction of lipids (cell disruption or diffusion across a cell wall) from microalgae using microscopic analysis of extracted biomass. We have also assessed the relative influence of the solvent (or extractant) selectivity and the intensity of convection in the medium on the overall lipid yield. None of the techniques used produced complete disruption of the cells, not even sonication. Thus, the prominent mechanism of lipid extraction was diffusion across a cell wall. Moreover, the selectivity of the solvent was found to be the most dominating factor in overall lipid extraction by diffusion than the intensity of bulk convection in the medium.

Industrial Requirements for Thermodynamics and Transport Properties

Abstract: This work reports the results of an investigation on industrial requirements for thermodynamic and transport properties carried out by the Working Party on Thermodynamic and Transport properties (http://www.wp-ttp.dk/) of the European Federation of Chemical Engineering, EFCE (http://www.efce.info/). A carefully designed questionnaire was sent to a number of key technical people in companies in the oil and gas, chemicals, and pharmaceutical/biotechnology sectors. Twenty-eight companies have provided answers which formed the basis for the analysis presented here. A number of previous reviews, specifically addressed to or written by industrial colleagues, are discussed initially. This provides the context of the survey and material with which the results of the survey can be compared. The results of the survey have been divided into the themes: data, models, systems, properties, education, and collaboration. The main results are as follows. There is (still) an acute need for accurate, reliable, and thermodyn...

CO2 and CH4 Separation by Adsorption Using Cu-BTC Metal−Organic Framework

Abstract: Molecular simulations have shown that the metal−organic framework Cu-BTC (Cu3(BTC)2) is an interesting candidate for the separation of CO2 by adsorption. In this work, the first experimental binary and ternary adsorption data of CO2, CH4, and CO on the Cu-BTC are reported. These data are analyzed and compared with coadsorption models that are built from pure component isotherm data. Cu-BTC has a CO2/CH4 selectivity of ∼8 and a high delta loading (=difference between adsorption capacity under conditions of adsorption and desorption) and therefore appears to be a good compromise between zeolites, with high selectivity for CO2, but low delta loadings, and activated carbons, with high delta loadings, but low selectivity, for pressure swing adsorption applications.

Photobioreactor Design for Commercial Biofuel Production from Microalgae

Abstract: This review paper describes systems used to cultivate microalgae for biofuel production. It addresses general design considerations pertaining to reactors that use natural light and photosynthetic growth mechanisms, with an emphasis on large-scale reactors. Important design aspects include lighting, mixing, water consumption, CO2 consumption, O2 removal, nutrient supply, temperature, and pH. Though open pond reactors are the most affordable option, they provide insufficient control of nearly all growth conditions. In contrast, a variety of closed reactors offer substantial control, but few feature the likelihood for levels of productivity that offset their high cost. One of the greatest challenges of closed photobioreactor design is how to increase reactor size in order to benefit from economy of scale and produce meaningful quantities of biofuel. This paper also highlights the concept of combining open and closed systems and concludes with a discussion regarding a possible optimal reactor configuration.

Carbonation of CaO-Based Sorbents Enhanced by Steam Addition

Abstract: The carbonation reaction has recently been intensively investigated as a means of CO2 capture from gas mixtures such as flue gas produced during fossil fuel combustion. Unfortunately, this gas−solid reaction is limited due to formation of the solid product (CaCO3) at the reacting surface and sintering, all of which reduce the carrying capacity of the sorbent. In this work the enhancement of carbonation conversion by means of steam addition to the carbonating gas was studied. Seven limestones of different origin and composition as well as one synthetic sorbent (calcium aluminate pellets) were tested. A thermogravimetric analyzer (TGA) was employed for the carbonation tests at different temperatures (350−800 °C) in a gas mixture containing typically 20% CO2 and 10 or 20% H2O(g). The samples tested were calcined under an N2 (800 °C) or CO2 (950 °C) atmosphere to explore the influence of different levels of sample sintering, and the results obtained were compared with those seen for carbonation in dry (no ste...

Planning and Scheduling under Uncertainty: A Review Across Multiple Sectors

Abstract: This paper provides an overview of the key contributions within the planning and scheduling communities with specific emphasis on uncertainty analysis. As opposed to focusing in one particular industry, several independent sectors have been reviewed in order to find commonalities and potential avenues for future interdisciplinary collaborations. The objectives and physical constraints present within the planning and scheduling problems may vary greatly from one sector to another; however, all problems share the common attribute of needing to model parameter uncertainty in an explicit manner. It will be demonstrated through the literature review that two-stage stochastic programming, parametric programming, fuzzy programming, chance constraint programming, robust optimization techniques, conditional value-at-risk, and other risk mitigation procedures have found widespread application within all of the analyzed sectors. This review is the first work which attempts to provide a comprehensive description of t...

High-Temperature Pyrolysis of Blended Animal Manures for Producing Renewable Energy and Value-Added Biochar

Abstract: In this study, we used a commercial pilot-scale pyrolysis reactor system to produce combustible gas and biochar at 620 °C from three sources (chicken litter, swine solids, mixture of swine solids with rye grass). Pyrolysis of swine solids produced gas with the greatest higher heating value (HHV) followed by the mixture of swine solids with rye grass and chicken litter. Relatively high S-containing gases were produced; dimethyl sulfide and methyl mercaptan concentrations were higher than the OSHA PEL limits. Biochar yield ranged from 43 to 49% based on dry weight with about 53% of carbon recovery. Whereas the HHV of the chicken litter biochar was slightly below that of low rank coals, swine-based biochars had HHVs between high and low rank coals. Approximately 50% of the feedstock energy was retained in biochar and 25% in produced gases. Manure biochars contained higher concentrations of P and K than that of original manure feedstocks. Consequently, these could be used as a low-grade fertilizer to improve ...

Improved Antifouling Property of PES Ultrafiltration Membranes Using Additive of Silica−PVP Nanocomposite

Abstract: To improve the surface coverage of polyvinylpyrrolidone (PVP) on membrane surfaces and further enhance the antifouling property, a silica−PVP nanocomposite was synthesized and used as a novel hydrophilic additive to modify polyethersulfone (PES) membranes. Transmission electron microscopy (TEM) observation showed that PES membranes, using additives of PVP and silica−PVP nanocomposites, have similar asymmetric structures. X-ray photoelectron spectroscopy (XPS) measurement indicated that the near-surface coverage of PVP for PES membrane with a silica−PVP nanocomposite additive is greater than that with a PVP additive. Protein ultrafiltration experiment also showed that the antifouling ability of PES membrane with a silica-PVP nanocomposite additive is stronger than that with a PVP additive. The hydrophilic modification with a silica−PVP nanocomposite is an appropriate method for improved antifouling property of PES ultrafiltration membranes.

Review of Water Network Design Methods with Literature Annotations

Abstract: The designing of heat exchanger networks (HENs), mass exchanger networks (MENs), and water networks (WNs) is a major topic of process system engineering. The WN problem is most recent, and although the seminal work was published in 1980, the real development should be dated from 1994. Increasing public concern on scarce water resources, together with stringent regulations on wastewater discharge, has caused a great number of publications in recent years. Despite noticeable achievements in the topic, there is still a need for robust flexible approaches that will find wider application in practice. This review provides the reader with literature annotations on the WN problem from the year 1980 and follows the format of an earlier HEN review paper [Furman, K. C.; Sahinidis, N. V. A critical revue and annotated bibliography for heat exchanger network synthesis in the 20th century. Ind. Eng. Chem. Res. 2002, 41, 2335−2370]. An analysis of the WN problem formulation also is given, together with an overview of s...

Mixed-Matrix Membrane Hollow Fibers of Cu3(BTC)2 MOF and Polyimide for Gas Separation and Adsorption

Abstract: Metal−organic framework (MOF) crystals of Cu3(BTC)2 with a high surface area (1396 m2·g−1) were synthesized and mixed with polyimide (PI) to prepare mixed-matrix membranes (MMMs) for gas separations. The PI−Cu3(BTC)2 blend was successfully spun into MMM hollow fiber by the dry/wet-spinning method. SEM images of the fiber cross sections revealed significant plastic deformation of the polymer matrix owing to the strong affinity between Cu3(BTC)2 and PI. The H2 permeance and the selectivity of H2 with respect to other gases such as N2, CO2, O2, and CH4 both increased markedly with increased Cu3(BTC)2 loading. At a loading of 6 wt % Cu3(BTC)2, the permeance of H2 increased by 45%, and the ideal selectivity increased by a factor of 2−3 compared to the corresponding values for pure PI.

Reflections on the Solubility of Cellulose

Abstract: Wood cellulose can be used for producing biofuels and biopolymers, thus offering a solution to global concerns on the excessive use of fossil fuels. This requires a cellulose solvent that also allows the ecofriendly processing of selective wood components. Some ionic liquids (ILs) have shown promising results as cellulose solvents with many advantages over traditional approaches. It is agreed that their ionic nature is responsible for cleaving hydrogen bonds between cellulose chains, resulting in dissolution of the biopolymer. However, it is still necessary to establish a structural relationship between IL cations and anions, which explains why only certain ion combinations show the ability to dissolve cellulose. This work aims to analyze the structural similarities displayed by common cellulose solvents focusing on requirements for ionic liquids to qualify as such. A mutual relationship between IL anions and cations is postulated that offers an explanation for the ability or disability of certain ion com...

Chemical Looping Technology and Its Fossil Energy Conversion Applications

Abstract: The concept of chemical looping reactions has been widely applied in chemical industries, for example, the production of hydrogen peroxide (H2O2) from hydrogen and oxygen using 9,10-anthraquinone as the looping intermediate Fundamental research on chemical looping reactions has also been applied to energy systems, for example, the splitting of water (H2O) to produce oxygen and hydrogen using ZnO as the looping intermediate Fossil fuel chemical looping applications had been used commercially with the steam-iron process for coal from the 1900s to the 1940s and had been demonstrated at a pilot scale with the carbon dioxide acceptor process in the 1960s and 1970s There are presently no chemical looping processes using fossil fuels in commercial operation A key factor that hampered the continued use of these earlier processes for fossil energy operation was the inadequacy of the reactivity and recyclability of the looping particles This factor led to higher costs for product generation using the chemical

Adsorption of CO2 on Hydrotalcite-Derived Mixed Oxides: Sorption Mechanisms and Consequences for Adsorption Irreversibility

Abstract: Magnesium−aluminum double oxides derived from the thermal treatment of layered hydroxides (hydrotalcites) have been tested for CO2 adsorption. The effects of various preparation parameters, such as the incorporated cation (K or Na), the mode of addition of magnesium and aluminum precursors, the presence of sonication, and the calcination temperature, on the adsorption capacity under mild conditions were studied using thermogravimetry and calorimetry. Calorimetric and FTIR data were used to explain the adsorption mechanisms leading to the undesirable irreversible adsorption. This adsorption was related to the formation of unidentate CO2-adsorbent species with the strongest adsorption sites, whereas bidentate and surface bicarbonates lead to highly reversible adsorption. In conclusion, preparation procedures that lead to an increase in the strength of basic sites do not lead to significant increases in the adsorption capacity, but rather lead to more difficult regeneration of the saturated support.

Factors Affecting Wood Dissolution and Regeneration of Ionic Liquids

Abstract: Three wood species, eucalyptus grandis (E. grandis), southern pine (S. pine), and Norway spruce thermomechanical pulp (N. spruce TMP) were pretreated by dissolution in the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). The wood was regenerated from the ionic liquid in high yield and the recycling of the ionic liquid was nearly quantitative. The lignin contents and the efficiencies of cellulase enzymatic hydrolyses of the regenerated wood were examined offering an understanding into the IL pretreatment efficiency. The components that remained within the recycled ILs were qualitatively characterized by 31P NMR spectroscopy. Wood density, pulverization intensity, and the nature of the regeneration nonsolvents were investigated as factors affecting the overall process. An increase in the wood density decreased the efficiency of the pretreatment, whereas extended pulverization periods decreased the yield of the regenerated wood after the IL pretreatment,with more glucose being released duri...

Design and packaging of microreactors for high pressure and high temperature applications

Abstract: The development of chemically compatible microsystems that can operate across expanded process conditions, such as high pressures (HP) and high temperatures (HT), is of great interest for many applications, including high pressure chemistry and hydrothermal and supercritical fluid processes. We present a methodology for the successful design and use of HP/HT microsystems. Key parameters for the fabrication of microreactors and modular fluidic packaging able to withstand severe pressure and temperature conditions (30 MPa, 400 °C) are described. Applications of these HP/HT plug and play microsystems are illustrated with examples, including multiphase flow visualization through the transition of liquid−liquid immiscible hexane−water segmented flow to homogeneous supercritical flow, on chip supercritical water oxidation, and synthesis of iron oxide nanoparticles.

Development and Performance of CaO/La2O3 Sorbents during Calcium Looping Cycles for CO2 Capture

Abstract: The calcium looping cycles method has been identified as an attractive method for CO2 capture during coal combustion and gasification processes. However, it is well-known that the capture capacity of CaO undergoes a rapid decrease after mutiple cycles. In order to improve the stability of CO2 capture capacity in CaO, this paper focuses on the development and performance of the synthetic CaO/La2O3 sorbents for calcium looping cycles.The sorbents were synthesized by three different methods: dry physical mixing, wet chemistry, and sol−gel combustion synthesis (SGCS). Their multicyclic CO2 capture capacity and the effect of the additive La2O3 were investigated in a fixed bed reactor system. The results indicate that the additive of La2O3 plays a positive role in the carbonation/calcination reactions, and the SGCS-made synthetic sorbent is composed of ultrafine well-dispersed hollow structured particles which are beneficial to the gas-phase diffusion on the surface area and can prevent small CaO particles from...

Carbon dioxide capture from flue gases using a cross-flow membrane contactor and the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate

Abstract: Carbon dioxide (CO2) emissions have to be controlled and reduced in order to avoid environmental risks. Membrane processes in combination with the use of ionic liquids are recently under research and development in order to demonstrate a zero solvent emission process for CO2 capture. In this work, the application of a cross-flow membrane contactor is studied for CO2 absorption when the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is used as solvent. A mathematical model considering a parallel flow configuration is applied for a cross-flow system in order to describe the mass transfer rate. At a macroscopic level, Koveralla is calculated considering different mixing models corresponding to plug flow and continuous stirred models and a first order mass transfer rate. A microscopic model based on laminar flow has been applied, obtaining a membrane mass transfer coefficient of km = 3.78 × 10−6 m·s−1, which is about five times higher than that obtained in the macroscopic model. The interfacial area, a...

Behavior of CaTiO3/Nano-CaO as a CO2 Reactive Adsorbent

Abstract: This study focuses on the preparation of a CaTiO3-coated nano-CaO-based CO2 adsorbent (CaTiO3/nano-CaO) for the improvement of sorption properties. The CaTiO3-coated nano-CaO adsorbent was prepared by forming Ti(OH)4 from the hydrolysis of titanium alkoxide in a nano-CaCO3 suspended solution. The resulting Ti(OH)4-coated nano-CaCO3 was then heated and calcined. Test results from transmission electron microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy show that an obvious film of TiO2 was formed on the surface of nano-CaCO3 after heating. X-ray diffraction analysis also showed that the nano-CaTiO3 layer was formed at 750 °C, a calcination temperature that causes the reaction of TiO2 with nano-CaO. The cyclic tests of reactive sorption capacity were conducted in a thermogravimetric analyzer under the following conditions: 0.02 MPa CO2 partial pressure, carbonation temperature of 600 °C, and calcination temperature of 750 °C. Test results showed that CaTiO3 coated onto the ...

Low-Energy Distillation-Membrane Separation Process

Abstract: A low-energy separation process combining distillation and membrane vapor permeation is introduced as an alternative to conventional distillation. The process can be applied to any liquid mixture for which appropriate selective membranes are available. However, in this paper, the discussion is limited to water/organic solvent mixtures using membranes that preferentially permeate water. Such membranes are available. The process is illustrated with two mixtures: ethanol (light component)/water (heavy component) and acetic acid (heavy component)/water (light component) mixtures. In both cases, the combination process reduces the energy consumption of the separation to half that of simple distillation.

Extractive Dividing Wall Column: Design and Optimization

Abstract: This paper proposes a novel extractive dividing wall distillation column, which has been designed using a constrained stochastic multiobjective optimization technique. The approach is based on the use of genetic algorithms to determine the design that minimizes energy consumption and total annualized cost. Several case studies are used to show the feasibility of performing extractive separations in dividing wall distillation columns. The simulation results show the effect of the main variables on the complex extractive distillation process.

Kinetic Evidence of the Maillard Reaction in Hydrothermal Biomass Processing: Glucose−Glycine Interactions in High-Temperature, High-Pressure Water

Abstract: Kinetic and mechanistic evidence is presented of the occurrence of a Maillard-type reaction under conditions of interest to hydrothermal biomass processing. Glucose−glycine mixtures were reacted at 250 °C and 10 MPa in an excess of water; both glucose and glycine were found to strongly influence the destruction kinetics of the other species and to result in quantitative and qualitative changes, such as strong absorbance at 420 nm and the production of a dark brown appearance and nutty odor, which are characteristic of the Maillard reaction. The presence of glucose always resulted in higher glycine destruction; the presence of glycine resulted in increased or decreased glucose destruction, depending on initial concentrations, which is consistent with results reported in the literature for lower temperature Maillard reactions. Surrogate compounds that contain the same chemical functional groups also resulted in similar trends. As a result of this reaction, the presence of proteins and amino acids in biomass...