TY - JOUR TI - Gas-lift reactors for rapid reactions with appreciable gas consumption AU - Roberts, G. W. AU - Carbonell, R. G. AU - Saez, A. E. T2 - Chemical Engineering & Technology AB - Gas-lift reactors offer important advantages for a number of gas/liquid and gas/liquid/solid reactions. However, the design and operation of these reactors can be complex when there is a substantial change in the molar gas flow rate along the length of the reactor, e.g., when a gaseous reactant is converted into a liquid product. In this situation, there is a strong coupling between reactor hydrodynamics and reaction kinetics, which arises from the fact that the rate of liquid circulation through the reactor and the longitudinal profile of gas holdup in the riser are mutually dependent. Several one-dimensional models have been developed to describe kinetic/hydrodynamic coupling in gas-lift reactors. These models offer useful insights into the parameters that affect reactor performance. The models can also be used to explore different approaches to scale-up. DA - 2000/// PY - 2000/// DO - 10.1002/(sici)1521-4125(200001)23:1<80::aid-ceat80>3.0.co;2-m VL - 23 IS - 1 SP - 80-87 ER - TY - JOUR TI - Fractionation of whey proteins with a hexapeptide ligand affinity resin AU - Gurgel, PV AU - Carbonell, RG AU - Swaisgood, HE T2 - BIOSEPARATION DA - 2000/// PY - 2000/// DO - 10.1023/A:1011191818927 VL - 9 IS - 6 SP - 385-392 SN - 0923-179X KW - alpha-lactalbumin KW - bioselective adsorption KW - peptide ligands KW - whey protein isolate ER - TY - JOUR TI - Interfacial response of a fluorescent dye grafted to glass AU - Lenhart, JL AU - Zanten, JH AU - Dunkers, JP AU - Parnas, RS T2 - LANGMUIR AB - The properties of an epoxy/glass interfacial region are studied by covalently grafting a fluorescent probe to the glass surface. A dimethylaminonitrostilbene fluorophore is tethered to a triethoxysilane-coupling agent, generating a fluorescently labeled silane coupling agent (FLSCA). The glass surface is coated with a silane layer that was doped with small amounts of FLSCA. When the FLSCA-doped, silane-coated glass is immersed in epoxy resin, a 42-nm blue shift in fluorescence occurs during resin cure over the grafted FLSCA layer. When the dye is dissolved in bulk epoxy a 64-nm blue shift occurs during resin cure. The difference in blue shift is attributed to higher polarity and enhanced mobility in the buried interface. DA - 2000/10/17/ PY - 2000/10/17/ DO - 10.1021/la000553n VL - 16 IS - 21 SP - 8145-8152 SN - 0743-7463 ER - TY - JOUR TI - SANS study of polymer-supercritical fluid solutions: Transitions from liquid to supercritical fluid solvent quality AU - DiNoia, TP AU - Kirby, CF AU - Zanten, JH AU - McHugh, MA T2 - MACROMOLECULES AB - Phase behavior and small-angle neutron scattering (SANS) measurements are reported for poly(ethylene-co-1-butene) (PEB) dissolved in pentane, pentane plus ethane, and supercritical ethane to pressures of 2000 bar and temperatures of 130 and 150 °C. The solution microstructure and solvent quality are probed using the high-concentration isotopic labeling technique at the mixture critical concentration to determine the variation of intra- and intermolecular correlations on approach to the phase boundary with isothermal changes in pressure. The SANS results for the three solutions show that the intramolecular radius of gyration remains close to the unperturbed value over the entire pressure range investigated. However, the intermolecular correlation length changes dramatically as the phase boundary is approached and is approximately 3 times larger in ethane as compared to pentane even at 1000 bar from the phase boundary. The intermolecular correlation length data suggest that ethane is a poorer quality solvent than pentane at conditions close to the phase boundary even though both solvents have similar mass densities. DA - 2000/8/22/ PY - 2000/8/22/ DO - 10.1021/ma000240z VL - 33 IS - 17 SP - 6321-6329 SN - 0024-9297 ER - TY - JOUR TI - Removal of solid organic films from rotating disks using emulsion cleaners AU - Kabin, JA AU - Withers, ST AU - Grant, CS AU - Carbonell, RG AU - Saez, AE T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - Measurements have been made of the rate of removal of a solid organic film (phenanthrene) from the surface of a rotating disk using emulsions containing water, the nonionic surfactant Tween 20, and d-limonene as the organic phase. The results show that phenanthrene removal initially occurs by the uptake of phenanthrene into the emulsion drops as small aggregates. Simultaneously, the organic phase penetrates into the phenanthrene film, diminishing the adhesive force between the film and the substrate. After sufficient time, the phenanthrene film detaches from the rotating disk surface as a solid. This detachment mechanism accounts for the vast majority of the phenanthrene removal (∼90%). Initial solubilization rates were analyzed using two solubilization models. Both models assume that phenanthrene removal occurs via a mass transfer limited removal of phenanthrene-laden emulsion drops from the phenanthrene film surface into the bulk solution. One model treats the emulsion as homogeneous while the other accounts for the finite size of the emulsion droplets. The latter model was also used to relate the flux of organic phase impacting the phenanthrene film to the detachment times. DA - 2000/8/15/ PY - 2000/8/15/ DO - 10.1006/jcis.2000.6832 VL - 228 IS - 2 SP - 344-358 SN - 0021-9797 KW - emulsion KW - cleaning KW - phenanthrene KW - solubilization KW - rotating disk ER - TY - JOUR TI - Immobilizing a fluorescent dye offers potential to investigate the glass/resin interface AU - Lenhart, JL AU - Zanten, JH AU - Dunkers, JP AU - Zimba, CG AU - James, CA AU - Pollack, SK AU - Parnas, RS T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - Silane coupling agents are commonly applied to glass fibers to promote fiber/resin adhesion and enhance durability in composite parts. In this study, a coupling agent multilayer on glass was doped with trace levels of the dimethylaminonitrostilbene (DMANS) fluorophore. The fluorophore was immobilized on the glass surface by tethering the molecule to a triethoxy silane coupling agent, creating the DMANS/silane coupling agent molecule (DMSCA). DMSCA was then diluted with commonly used coupling agents and grafted to a glass microscope coverslip to create a model composite interface. A 53-nm blue shift in fluorescence from the immobilized DMSCA can be followed during cure of an epoxy resin overlayer, giving this technique potential to monitor the properties of the fiber/resin interface during composite processing. Contact angle measurements on these coupling agent layers were similar in the presence or absence of the DMSCA molecule, suggesting that trace levels of the fluorescent probe did not affect the structure of the layer. The immobilized DMSCA molecule behaved similarly to the DMANS precursor in solution. Both showed longer wavelength fluorescence in more polar environments. Copyright 2000 Academic Press. DA - 2000/1/1/ PY - 2000/1/1/ DO - 10.1006/jcis.1999.6577 VL - 221 IS - 1 SP - 75-86 SN - 0021-9797 KW - fluorescence KW - coupling agent KW - interface KW - sensor KW - dye ER - TY - JOUR TI - Discovery of alpha-1-proteinase inhibitor binding peptides from the screening of a solid phase combinatorial peptide library AU - Bastek, PD AU - Land, JM AU - Baumbach, GA AU - Hammond, DH AU - Carbonell, RG T2 - SEPARATION SCIENCE AND TECHNOLOGY AB - Alpha-1-proteinase inhibitor (A1PI, also known as alpha-1-antitrypsin), a blood plasma protein, was radiolabeled and screened against a portion of a hexameric, solid-phase combinatorial peptide library. The screening of 2% of a library containing 34 million peptides yielded 19 sequences. All 19 sequences bound A1PI when immobilized to a chromatographic support, but with varying avidities. Several of these sequences proved capable of purifyingA1PI from aqueous mixtures with human serum albumin and from Effluent II+III, a process intermediate in the Cohn plasma fractionation process. A single chromatography step was shown to provide high yields with significant purification and no measurable loss in activity. DA - 2000/// PY - 2000/// DO - 10.1081/SS-100102488 VL - 35 IS - 11 SP - 1681-1706 SN - 0149-6395 KW - protein purification KW - alpha-1-proteinase inhibitor KW - combinatorial peptide library KW - affinity chromatography ER - TY - JOUR TI - Chromatographic resolution of tryptophan enantiomers with L-Leu-L-Leu-L-Leu peptide - Effects of mobile phase composition and chromatographic support AU - Kaufman, DB AU - Hayes, T AU - Buettner, J AU - Hammond, DJ AU - Carbonell, RG T2 - JOURNAL OF CHROMATOGRAPHY A AB - Tryptophan enantiomers have been separated by zwitterion pair chromatography using L-leucine-L-leucine-L-leucine peptide as the zwitterion pairing agent. The peptide ligand is adsorbed onto an octadecylsilane support with excess ligand present in bulk solution. This article examines the roles of the hydrophobic matrix and the mobile phase components on tryptophan enantiomer binding and resolution. Capacity factors and enantioselectivites are given for both hydrophobic and hydrophilic matrices using mobile phases containing Leu-Leu-Leu peptide and/or salt. A decrease in selectivity upon the addition of mobile phase salt suggests that quadrupolar ion-pairing contributes to chiral recognition. Results indicate that binding is significantly reduced and separation is not achieved when Leu-Leu-Leu is coupled onto cross-linked or polymerized hydrophilic resins as well as onto macroporous polystyrene resin. However, resin-immobilized Leu-Leu-Asp-Leu-Leu-Leu, Leu-Leu-Glu-Leu-Leu-Leu, and Leu-Leu-Leu-Glu-Leu-Leu peptides, with ion-pairing sites designed to mimic the Leu-Leu-Leu-saturated C18 support, also do not resolve tryptophan enantiomers. This suggests the Leu-Leu-Leu structure is critical for enantiomer resolution. Because D- and L-tryptophan are separated in the absence of bulk Leu-Leu-Leu, chiral discrimination is believed to occur at the surface of the octadecylsilane support. DA - 2000/3/31/ PY - 2000/3/31/ DO - 10.1016/S0021-9673(99)01299-6 VL - 874 IS - 1 SP - 21-26 SN - 0021-9673 KW - enantiomer separation KW - mobile phase composition KW - stationary phases, LC KW - amino acids KW - tryptophan ER - TY - JOUR TI - Recovery of proteins and other biological compounds from food processing wastewaters using fibrous materials and polyelectrolytes AU - Chen, LA AU - Carbonell, RG AU - Serad, GA T2 - WATER RESEARCH AB - A combined system of cellulose-based fibrous materials and polyelectrolytes has been studied for the recovery of proteins and other biological compounds from wastewaters from a typical food processing plant. Carboxymethyl cellulose (CMC) interacts with biomolecules by electrostatic and polymer bridging, while cellulose triacetate fibrets (CTF) facilitate floc growth by adsorption and bridging of primary particles and by entrapment of small aggregates within their highly fibrillated microstructure. Final slurries have good filtration properties, resulting in a dry and easy to handle filter cake, which could be recovered as animal feed. The final filtrate has high water clarity and low protein concentration. This recovery system exhibits high reductions in total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia, oils and greases, biochemical oxygen demand (BOD) and total fecal coliforms. The final levels of TSS, oils and greases and ammonia are below regulatory limits. Reduction of BOD reached 90%, although final concentrations are slightly higher than the regulatory levels. DA - 2000/2// PY - 2000/2// DO - 10.1016/S0043-1354(99)00152-9 VL - 34 IS - 2 SP - 510-518 SN - 0043-1354 KW - food processing KW - wastewaters KW - protein KW - fibrous materials KW - polyelectrolytes KW - adsorption KW - filtration KW - animal feed ER - TY - JOUR TI - Multiphase flow models in packed beds AU - Carbonell, RG T2 - OIL & GAS SCIENCE AND TECHNOLOGY-REVUE D IFP ENERGIES NOUVELLES AB - This paper presents a review of theories for gas and liquid flows in packed beds as applied to chemical reactor design. Significant progress has been made in understanding multiphase flow phenomena in packed beds and the ability to make quantitative predictions of flow behavior. Successful theories use spatially averaged continuity and momentum equations for the gas and liquid phases, coupled with constitutive equations for drag forces between the fluid phases and the particles and for capillary pressure effects in the column. The result is a self-consistent set of equations that are able to model experimental data for liquid holdup and pressure drop under steady-state conditions. These theories have also been used to generate information on the stability of these steady-state flows. Remarkable agreement has been found between the theoretical predictions of the transitions from the low-interaction to the high-interaction regimes and experimental observations. In addition, the same set of equations has been successful in modeling both cocurrent and countercurrent flows of gas and liquid phases in packed beds. This is a robust approach based on fundamental principles of fluid mechanics that can be applied to other reactor configurations. A similar formulation has also led to improvements in understanding of gas lift reactor hydrodynamics, and some of these results will be presented for comparison. A summary of challenges that exist in extending these hydrodynamic models to include the effects of heat transfer, mass transfer and reaction rates will also be presented. DA - 2000/// PY - 2000/// DO - 10.2516/ogst:2000030 VL - 55 IS - 4 SP - 417-425 SN - 1953-8189 KW - drag force KW - permeability KW - pressure drop KW - holdup KW - flow transition KW - hydrodynamic regime ER - TY - JOUR TI - Brownian motion in a single relaxation time Maxwell fluid AU - Zanten, JH AU - Rufener, KP T2 - PHYSICAL REVIEW E AB - A simple model of Brownian motion in a single relaxation time Maxwell fluid is described and compared to diffusing wave spectroscopy measurements of colloidal motion in representative viscoelastic fluids, namely, CTAB/KBr wormlike micelle solutions. The experimentally measured Brownian motion conforms to the model predictions at long times (low frequencies) and is an additional confirmation of the essentially Maxwellian stress relaxation behavior of wormlike micelle solutions at low frequencies. Surprisingly, the Maxwell model predicts a plateau onset time which, while capable of reducing the measured mean-square displacements to a master curve, also grossly underestimates the actual plateau onset time. The predicted rescaling is shown to be essentially that also predicted by the Doi-Edwards tube model for polymer solutions under good solvent (excluded volume) conditions where a more proper accounting of the short-time dynamics is made. This indicates that the success of the predicted Maxwell model plateau onset time rescaling is purely fortuitous. DA - 2000/10// PY - 2000/10// DO - 10.1103/physreve.62.5389 VL - 62 IS - 4 SP - 5389-5396 SN - 1550-2376 ER -