A practical equation of state for non‐spherical and asymmetric systems for application at high pressures. Part 2: Extension to mixtures

In part I of this series the pure component PHCT‐DNSK equation of state (EOS) was presented. In this paper the EOS is extended to describe mixtures, particularly asymmetric mixtures containing one or more low molecular weight spherical compound together with one or more high molecular weight chain‐like compound. The EOS utilises theoretically correct mixing rules and is generally able to predict the correct trends quantitatively for binary mixtures, and in most cases outperform other EOSs. With the use of a small, temperature independent, interaction parameter the EOS is able to predict the phase behaviour of the investigated systems qualitatively. The EOS is able to predict the phase behaviour of a multi‐component system containing one or more light components and a range of heavy hydrocarbons with improved accuracy compared to other EOSs at reduced computational times. © 2011 Canadian Society for Chemical Engineering     

Extending the range of COSMO‐SAC to high temperatures and high pressures

The range of the predictive Gibbs energy of solvation model, COSMO‐SAC, is extended to large ranges of density, pressure, and temperature for very nonideal mixtures by combining it with an equation of state (EOS) using the Wong‐Sandler mixing rule. The accuracy of isothermal vapor‐liquid equilibria (VLE) calculations based on using the predictive COSMO‐SAC model and separately the correlative NRTL model is compared, each combined with three different forms of the Peng‐Robinson equation of state. All the models considered require the value of the EOS mixing rule binary parameter k_ij. The NRTL model also requires three other parameters obtained from correlation low pressure VLE data. The PRSV + COSMO‐SAC model is showed, with its one adjustable parameter obtained from low temperature data leads good predictions at much higher temperatures and pressures. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1806–1813, 2018     

Prediction of hydrate formation conditions based on the vdWP‐type models at high pressures

Prediction of phase boundaries of gas hydrates has been done for several decades based on the vdWP (van der Waals and Platteeuw) hydrate equation and the classical thermodynamic equations for describing the water fugacities in water or ice phase. This procedure gives a reasonable prediction at low pressures, but when the pressure increases, above 10⁵ kPa, it shows a significant error. In the conventional vdWP‐type models it has been assumed that the volume difference between the empty hydrate lattice and pure liquid water is independent of the system pressure and temperature. In this work, different approaches for describing the volume dependency of pure liquid water and the empty hydrate lattice on the system pressure have been used to predict the hydrate equilibria based on the vdWP‐type model. Also, an expression is introduced to estimate the volume of methane hydrate lattice as a function of pressure and temperature. Finally, this method is extended to other hydrate formers, that is, ethane, carbon dioxide, xenon, and nitrogen. The predicted values are in good agreement with the experimental data both for L_w–H–V and L_w–H–L_hf phase boundaries.     

Effective particle diameters for simulating fluidization of non‐spherical particles: CFD‐DEM models vs. MRI measurements

Computational fluid dynamics—discrete element method (CFD‐DEM) simulations were conducted and compared with magnetic resonance imaging (MRI) measurements (Boyce, Rice, and Ozel et al., Phys Rev Fluids. 2016;1(7):074201) of gas and particle motion in a three‐dimensional cylindrical bubbling fluidized bed. Experimental particles had a kidney‐bean‐like shape, while particles were simulated as being spherical; to account for non‐sphericity, “effective” diameters were introduced to calculate drag and void fraction, such that the void fraction at minimum fluidization (ε_mf) and the minimum fluidization velocity (U_mf) in the simulations matched experimental values. With the use of effective diameters, similar bubbling patterns were seen in experiments and simulations, and the simulation predictions matched measurements of average gas and particle velocity in bubbling and emulsion regions low in the bed. Simulations which did not employ effective diameters were found to produce vastly different bubbling patterns when different drag laws were used. Both MRI results and CFD‐DEM simulations agreed with classic analytical theory for gas flow and bubble motion in bubbling fluidized beds. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2555–2568, 2017     

Potential application of aqueous two‐phase systems for the fractionation of RNase A and α‐Lactalbumin from their PEGylated conjugates

BACKGROUND: PEGylation reactions often result in a heterogeneous population of conjugated species and unmodified proteins that presents a protein separations challenge. Aqueous two‐phase systems (ATPS) are an attractive alternative for the potential fractionation of native proteins from their PEGylated conjugates. The present study characterizes the partition behaviors of native RNase A and α‐Lac and their mono and di‐PEGylated conjugates on polyethylene glycol (PEG)—potassium phosphate ATPS. RESULTS: A potential strategy to separate unreacted native protein from its PEGylated species was established based upon the partition behavior of the species. The effect of PEG molecular weight (400–8000 g mol^?1), tie‐line length (15–45% w/w) and volume ratio (V_R; 0.33, 1.00 and 3.00) on native and PEGylated proteins partition behavior was studied. The use of ATPS constructed with high PEG molecular weight (8000 g mol^?1), tie‐line lengths of 25 and 35% w/w, and V_R values of 1.0 and 3.0 allowed the selective fractionation of native RNase A and α‐Lactalbumin, respectively, from their PEGylated conjugates on opposite phases. Such conditions resulted in an RNase A bottom phase recovery of 99%, while 98% and 88% of mono and di‐PEGylated conjugates, respectively were recovered at the top phase. For its part, α‐Lac had a bottom phase recovery of 92% while its mono and di‐PEGylated conjugates were recovered at the top phase with yields of 77% and 76%, respectively. CONCLUSIONS: The results reported here demonstrate the potential application of ATPS for the fractionation of PEGylated conjugates from their unreacted precursors. Copyright © 2010 Society of Chemical Industry     

Experimental study of the burning behavior of n‐heptane pool fires at high altitude

The same configured calorimeters were built in Hefei (99.8 kPa) and Lhasa (66.5 kPa), respectively. Four sizes of round pans with diameters of 10, 15, 20, and 25 cm were adopted to study the effect of high altitude on the burning behavior of liquid pool fires. Analysis on the burning rate obtained in this study and in the literature at different altitudes indicates that pressure fire modeling performs better than radiation fire modeling in correlating the burning intensity (burning rate per unit area) with pressure and pool diameter for cases under low ambient pressure. The study also shows that heat release rate and combustion efficiency decrease at higher altitude. For medium pool fires, the burning intensity and heat release rate are proportional to D^5/2, thus the combustion efficiency being independent on pool sizes but decreases at higher altitude by a factor approximate to the pressure ratio. Copyright © 2014 John Wiley & Sons, Ltd.     

Practical application of aqueous two‐phase systems for the development of a prototype process for c‐phycocyanin recovery from Spirulina maxima

A novel process for the recovery of c‐phycocyanin from Spirulina maxima exploiting aqueous two‐phase systems (ATPS), ultrafiltration and precipitation was developed in order to reduce the number of unit operations and benefit from an increased yield of the protein product. The evaluation of system parameters such as PEG molecular mass, concentration of PEG as well as salt, system pH and volume ratio was carried out to determine under which conditions the c‐phycocyanin and contaminants concentrate to opposite phases. PEG1450–phosphate ATPS proved to be suitable for the recovery of c‐phycocyanin because the target protein concentrated in the top phase whilst the cell debris concentrated in the bottom phase. A two‐stage ATPS process with a phase volume ratio (V_r) equal to 0.3, PEG1450 7% (w/w), phosphate 20% (w/w) and system pH of 6.5 allowed c‐phycocyanin recovery with a purity of 2.4 (estimated as the relationship of the 620 nm to 280 nm absorbances). The use of ultrafiltration (with a 30 kDa membrane cut‐off) and precipitation (with ammonium sulfate) resulted in a recovery process that produced a protein purity of 3.8 ± 0.1 and an overall product yield of 29.5% (w/w). The results reported here demonstrated the practical implementation of ATPS for the design of a prototype recovery process as a first step for the commercial purification of c‐phycocyanin produced by Spirulina maxima. © 2001 Society of Chemical Industry     

Conversion of isopropanol and mixed alcohols to hydrocarbons using HZSM‐5 catalyst in the MixAlco™ process. Part 2: Studies at 5000 kPa (abs)

This study employed HZSM‐5 (SiO₂/Al₂O₃ = 280 mol/mol) to produce hydrocarbons from reagent‐grade isopropanol and mixed alcohols made from lignocellulosic biomass (waste office paper and chicken manure) using the MixAlco? process. All studies were performed at P = 5000 kPa (abs). The experiments were conducted in two sets: (1) vary temperature (300–450°C) at weight hourly space velocity (WHSV) = 1.92 h^?1, and (2) vary WHSV (1.92–11.52 h^?1) at T = 370°C. For isopropanol at higher temperatures, the olefins undergo more cracking reactions to produce smaller molecules and more aromatics. At low temperatures, the molecules have less energy so they do not crack and therefore form larger molecules. At T = 300°C, the carbon distribution is bimodal at C9 and C12, which shows trimerization and tetramerization of propene. At 300°C, propene was the only gas produced, cracking did not occur and therefore preserved high‐molecular‐weight molecules. For mixed alcohols, higher temperatures show significant catalyst deactivation; however, isopropanol did not show any catalyst deactivation. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1707–1715, 2016     

Extension of the orientation region of high density polyethylene molded by gas‐assisted injection molding: control of the thermal field

Wider zones with close‐knit orientation crystals in high density polyethylene (HDPE) parts prepared via the gas‐assisted injection molding (GAIM) process were obtained under high cooling gas pressure. In this study, compressed nitrogen, as a cooling medium, was introduced to retain a high cooling rate of the polymer melt. The high gas pressure leads to fast cooling of the polymer melt, which contributes to the stability of more oriented and stretched chains during the cooling stage. Then many more oriented structures are formed. SEM shows that many more oriented structures and interlocking shish‐kebab structures are achieved in parts under highest cooling gas pressure (P3). The P3 parts possess a higher degree of orientation than the corresponding regions of parts under lowest cooling gas pressure (P1). Moreover, tensile testing indicates that, compared with P1 parts, although P3 parts have lower crystallinity, the mechanical properties are improved because of the wider orientation zone and many more interlocking shish‐kebab structures. Combining the HDPE molecular parameters with the characteristics of the GAIM flow field and temperature field, the stability of oriented or stretched chains and the formation of orientation structures in various zones of the parts were analyzed. © 2014 Society of Chemical Industry     

A practical approach to produce Mg‐Al spinel based on the modeling of phase equilibria for NH4Cl‐MgCl2‐AlCl3‐H2O system

Based on chemical modeling of phase equilibria for the NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system, a practical approach to produce Mg‐Al spinel (MgAl₂O₄) (widely used as refractory brick, supports in catalysts, and inert material for oxygen carriers) is proposed and proven feasible. This novel process includes coprecipitation of Mg₄Al₂(OH)₁₄·3H₂O from the NH₃‐MgCl₂‐AlCl₃‐H₂O system; calcination of Mg₄Al₂(OH)₁₄·3H₂O to obtain Mg‐Al spinel and recovery of NH₄Cl from NH₄Cl‐rich solutions by feeding MgCl₂‐AlCl₃. A MSMPR reactor was applied to investigate the effect of temperature, feed concentration, and NH₄Cl addition on coprecipitation of precursor Mg₄Al₂(OH)₁₄·3H₂O from MgCl₂‐AlCl₃ solutions with Mg/Al ratio = 2 through gradual addition of NH₄OH. The phase equilibria of the NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system were determined over the temperature range 283.2 to 363.2 K using dynamic method. The experimental solubilities were regressed to obtain new Bromley‐Zemaitis model parameters. These newly obtained parameters were verified by predicting the quaternary system. A chemical model for the NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system has been established with the OLI platform. All the results generated from this study will provide the theoretical basis for Mg‐Al spinel production. The high quality Mg‐Al spinel was prepared by calcination of precursor from 773.2 to 1273.2 K, and the NH₄Cl was successfully recovered through the common ion effect of MgCl₂‐AlCl₃ addition. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1855–1867, 2013     

High‐resolution solid‐state NMR investigation of the filler–rubber interaction: 2. High‐speed [1H] magic‐angle spinning NMR spectroscopy in carbon‐black‐filled polybutadiene

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer–filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. Three series of samples were compared: pure polymers, raw polymer–filler blends (filler loading ratio: 50 phr) and solvent‐extracted blends (so as to get rid of any polymer which is not under the influence of the solid surface). While differential scanning calorimetry points to the existence of an elastomer fraction which is not detected as undergoing the glass transition, ie is strongly immobilized, [¹H] high‐resolution high‐speed magic‐angle spinning solid‐state NMR provides information on the effect exerted by polymer–filler interactions on the mobility of the various constitutive species of the macromolecular backbone. A systematic study of the evolution of the spectral lines yielded by the samples indicates that 1,2‐polybutadiene moieties have a particular affinity towards the carbon black surface which suggests the occurrence of specific interactions at the elastomer–filler interface. © 2001 Society of Chemical Industry     

Fire losses in selected property classifications of non‐residential,commercial and residential wood buildings. Part 1: hotels/motels and care homes for aged

In an attempt to evaluate the adequacy of building code requirements for selected classifications of non‐residential, commercial and residential wood buildings, researchers at Forintek Canada Corp. have examined Canadian and American fire loss statistics and compared fire losses for the selected classifications of wood buildings with those for similar buildings of non‐combustible construction. They have also examined causal factors associated with fires in those structures, extent of flame and smoke spread, ability of sprinkler systems and building construction to minimize fire losses, and outcomes of fire events. Because of the volume of information that was analysed, the results are being reported through three separate papers. This, the first, presents the ‘big picture’ with respect to fire losses in the selected classifications of non‐residential, commercial and residential structures, and discusses in detail fire losses for hotel/motel properties and care homes for the aged. Copyright © 2006 John Wiley & Sons, Ltd.     

Kinase in Motion: Insights into the Dynamic Nature of p38α by High‐Pressure NMR Spectroscopic Studies

Protein kinases are highly dynamic and complex molecules. Here we present high‐pressure and relaxation studies of the activated p38α mitogen‐activated protein kinase (MAPK). p38α plays a central role in inflammatory diseases such as rheumatoid arthritis and is therefore a highly attractive pharmaceutical target. The combination of high pressure and NMR spectroscopy allowed for a detailed per‐residue based assessment of the structural plasticity of p38α and the accessibility of low‐lying excited‐energy conformations throughout the kinase structure. Such information is uniquely accessible through the combination of liquid‐state NMR and high pressure and is of considerable value for the drug discovery process. The interactions of p38α and DFG‐in and DFG‐out ligands were studied under the application of high pressure, and we demonstrate how we can alter kinase dynamics by pressure in a similar way to what has previously only been observed by ligand binding. Pressure is shown to be a mild and efficient tool for manipulation of intermediate‐timescale dynamics.     

Reaction kinetics of dicyclohexylmethane‐4,4′‐diisocyanate with 1‐ and 2‐butanol: A model study for polyurethane formation

Reactions of dicyclohexylmethane‐4,4′‐diisocyanate (H₁₂MDI) with 1‐ or 2‐butanol in N,N‐dimethylformamide using dibutyltin dilaurate (DBTDL), stannous octoate (SnOct), or triethylamine (TEA) as catalyst were conducted in stirred reactors at 40°C. Reactor contents were circulated through an external loop containing a temperature‐controlled FTIR transmission cell; reaction progress was monitored by observing decrease in height of the isocyanate peak at 2266 cm⁻¹. Catalyzed reactions were second order as indicated by linear 1/[NCO] plots; uncatalyzed reactions yielded nonlinear plots. In all cases, the reaction with a primary alcohol was faster than that with a secondary alcohol. DBTDL dramatically increased the reaction rate with both primary and secondary alcohols. For [DBTDL] = 5.3 × 10⁻⁵ mol/L (300 ppm Sn) the second‐order rate constant, k, was 5.9 × 10⁻⁴ (primary OH) and 1.8 × 10⁻⁴ L/(mol s) (secondary OH); for both alcohols, this represents an increase in initial reaction rate on the order of 2 × 10¹ when compared with the uncatalyzed reactions. The second‐order rate constant was observed to increase linearly with DBTDL concentration in the range 100–700 ppm Sn. SnOct and TEA showed little to no catalytic activity with the primary alcohol and only a slight increase in reaction rate with the secondary alcohol. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A theoretical unsteady‐state model for kL of bubbles based on the framework of wide energy spectrum

An unsteady‐state model for predicting mass‐transfer coefficient k_L of bubbles with mobile surface was developed for turbulent gas‐liquid dispersions. This model was derived from an unsteady‐state convection and diffusion equation through a characteristics method. Unlike the previous work, this model considered the contributions of the amount of fluid structures of different scales (i.e., eddies) existing in the turbulent flows, the frequency of eddies arriving at the surface, the deformation and oscillation of bubbles to mass transfer. This model was based on the framework of wide energy spectrum and can account for the role of eddies of different sizes in mass transfer. Thus the assumption adopted by the previous models that mass transfer was controlled by eddies of certain sizes is no more needed. The overall k_L predicted by the proposed model showed a better agreement with the reported experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1007–1022, 2016     

Enhancement Factor for Gas Absorption in a Finite Liquid Layer. Part 4: Influence of Gas‐Phase Mass Transfer during a Second‐Order Reaction in a Liquid in Laminar Flow

Numerical analysis is presented for gas absorption accompanied by a second‐order reaction into a liquid layer of finite thickness in laminar flow, with the gas‐phase mass transfer resistance and the axial decrease of the gas‐phase solute concentration due to absorption being taken into account. Both cocurrent and countercurrent flow modes are analyzed, where the presence of significant resistance or axial decrease of the solute concentration in the gas phase can lead to substantially lower rates of gas absorption than those found when the influence of gas‐phase mass transfer is not considered. Approximate expressions describing the exact numerical solution to the enhancement factor in the cocurrent flow mode are developed and can be extrapolated for estimating the enhancement factor in a more general case of a (1, n)‐th‐order reaction in which the influence of gas‐phase mass transfer cannot be neglected.     

A Hofmann Rearrangement–Ring Expansion Cascade for the Synthesis of 1‐Pyrrolines: Application to the Synthesis of 2,3‐Dihydro‐1H‐pyrrolo[2,1‐a]isoquinolinium Salts

Treatment of cyclobutanecarboxamide with bis(trifluoroacetoxy)iodobenzene, PhI(OCOCF₃)₂, resulted in the formation of 1‐pyrroline via Hofmann rearrangement of the former followed by in situ ring expansion reaction of the cyclobutylamine intermediate. Further elaboration of this methodology to the synthesis of 2,3‐dihydro‐1H‐pyrrolo[2,1‐a]isoquinolinium salts has also been described.