Early stages of fouling biofilm development were studied under turbulent flow conditions in a circular tube. Two separate reactor systems were used to respectively determine (1) an empirical expression describing the rate of early biofilm development and (2) estimates of individual processes contributing to net biofilm accumulation. Both objectives required the development of various detection methods sensitive to the early stages of biofilm development. The first system was a completely mixed reactor with internal recycle. It was used to determine biofilm accumulation rate as a function of three variables: suspended biomass concentration (X), Reynolds Number (Re), and reactor dilution rate (D). The change in biofilm amount with time during the early stages was described using a first order expression that was a function of biofilm amount. The first order rate constant was directly proportional to biomass concentration and dilution rate and inversely proportional to Reynolds Number. The second system consisted of two completely mixed reactors in series, the second containing an internal recycle. Perturbations in the second reactor operating conditions allowed estimates of the individual processes contributing to early biofilm accumulation. Results indicate microorganism deposition, biofilm production, and biofilm detachment to contribute significantly to early biofilm development. The relative magnitude of the contribution of these individual processes changes with prevailing operating conditions. Biofilm detection methods based on chemical analysis of a biofilm constituent (i.e., chemical oxygen demand, biofilm polysaccharide) proved to be practical, rapid, and sensitive to early biofilm development.

Using the finite difference technique, the steady flow of a viscoelastic fluid through a contraction/expansion and a modified Graetz heat transfer problem for power-law fluids between parallel plates are numerically studied. The constitutive model used for the viscoelastic fluid flow extends the Maxwell equation of linear viscoelasticity to the non-linear region by letting both relaxation time and elastic modulus depend upon the existing structure. Based on the calculations for a 3:1/1:3 contraction/expansion geometry with fully developed simple shearing flows at the entrance and exit, there exists a transition range for this fluid model, in terms of the Weissenberg number, beyond which elastic effects appear to become less dominant. The upstream vortex detachment length before the contraction is shown to grow with increasing Weissenberg number, and then reach a maximum value, until no converged solution can be obtained or possibly unsteady flow starts to develop. Heat transfer to polymer melts or solutions flowing in a parallel plate system is of great importance in polymer processing, as for example in extrusion through a large aspect ratio slit die. The present work was undertaken to solve the energy equation for power-law fluids under various circumstances, including a temperature-dependent viscosity, viscous dissipation and heat convection across streamlines induced by the abrupt change of boundary temperature and subsequent velocity field rearrangement. In addition to the numerical solutions given, an analytical approximation method for the Graetz-Nusselt problem is also presented for comparison. This method divides the domain into two sections for which two corresponding solutions, approximated by polynomials, are solved by a thermal boundary layer theory and an integral method respectively. These two approximate solutions are then matched at the intersection to give a continuous and consistent temperature profile. Although the analytical solutions application is limited to the case with a temperature-independent viscosity, this simple analysis is believed to be better than the previous methods available in the literature.

A generalized appartus was designed and developed to measure high temperature-high pressure vapor-liquid-equilibrium (VLE), gas solubility, and pressure-volume-temperature (PVT) data for compounds and mixtures which are of interest in coal liquefaction processes. The heart of the apparatus was a novel variable volume equilibrium cell which consisted of a precision positive displacement pump in which the pump's cylinder itself was utilized as the equilibrium cell. V-L-E data on H(,2)-Tetralin systems were measured at 150(DEGREES), 189.6(DEGREES), and 268.7(DEGREES)C. The pressure range was 19.5 to 321.43 atm. The solubility of H(,2) in 2-ethylanthraquinone was measured at 150(DEGREES), 200(DEGREES), and 250(DEGREES)C and for pressures up to 247.69 atm. Molar volumes of saturated liquid tetralin were measured from 93.79(DEGREES) to 224.64(DEGREES)C. Compressibility factors were measured for benzene at 158.56(DEGREES), 181.68(DEGREES), and 202.64(DEGREES)C. The saturated molar volumes at each temperature were obtained from the intersection of each isotherm with the respective vapor pressure. These values were used along with a literature vapor pressure correlation('64) to calculate the enthalpy of vaporization, (DELTA)H(,(V)), of benzene at the three temperatures. The values of (DELTA)H(,(V)) were 137.4, 127.3, and 120.8 Btu/1bm at 158.56(DEGREES), 181.68(DEGREES), and 202.64(DEGREES)C, respectively. The corresponding values calculated by Organic('54) were 139, 130, and 120 Btu/1bm. Vapor pressures of the following six compounds were measured on another apparatus designed by Dr. S. C. Hwang of this laboratory: Tetralin, from 82.29(DEGREES) to 267.20(DEGREES)C; m-cresol, from 114.98(DEGREES) to 322.48(DEGREES)C; Naphthalene, from 91.44(DEGREES) to 295.01(DEGREES)C; 2-methylnaphthalene, from 130.22(DEGREES) to 325.34(DEGREES)C; Biphenyl, from 71.43(DEGREES) to 327.54(DEGREES)C; and Quinoline, from 64.96(DEGREES) to 328.14(DEGREES)C. A zone purification apparatus was designed and fabricated to purify the compounds used in VLE, PVT, solubility and vapor pressure measurements. The Grayson-Streed('31) (GS) and the Modified Regular Solution Theory (MRST)('30) were used to predict the VLE data for H(,2)-Tetralin systems. The predictions from the two correlations were compared with the data obtained in this work. The predictions from Riedel, Frost-Kalkwarf-Thodos and Nieto-Thodos vapor pressure correlations were compared with the experimental data obtained in this work. In general, if the temperature is not close to the triple or the critical points, all these correlations predict vapor pressures within (+OR-)5% of the experimental data.

The effects of sulfur poisoning on a nickel catalyst have been investigated using CH(,4)-D(,2) exchange reactions to monitor changes in the catalyst activity and selectivity. Mechanisms of the CH(,4)-D(,2) exchange reactions were also examined. The techniques employed include kinetic modeling, poisoning by pulse and flow methods, temperature programmed desorption (TPD), the thermogravimetric analysis (TGA). The catalyst used in the study contains 13% Ni (by weight) supported on a MgAl(,2)O(,4) carrier and has a BET surface area of 1.0 m('2)/g. Substantial increases in the catalyst activity were observed when the samples underwent a standard pretreatment in O(,2) at 475(DEGREES)C for 16 hours followed by a reduction in H(,2) at 525(DEGREES)C for 2 hours. The catalyst activation is believed to result from redispersion of nickel crystallites during oxidation. Two primary products, CD(,4) and CH(,3)D, were observed from the CH(,4)-D(,2) exchange reactions. The independent reactions responsible for the above products are multiple exchange and simple exchange. The multiple exchange is thought to occur via dissociative adsorption of CH(,4) on 7 nickel sites followed by rapid isotopic exchange of adsorbed H atoms with the gas phase deuterium. A kinetic expression based on the above model describes the experimental data quite well. It is proposed that CH(,3)D is the product of a reaction between the gas phase CH(,4), an adsorbed D atom, and an adjacent vacant Ni site. This model is supported by good agreement between the observed rates and the rates predicted by the developed kinetic expression. Sulfur poisoning by both pulse and flow methods (using H(,2)S as the poisoning compound) resulted in a linear decrease in the catalyst activity. However, no variations in either the selectivity (for CD(,4) and CH(,3)D) or activation energies of the exchange reactions were observed. Results from the poisoning experiments and H(,2)S absorption isotherms showed evidence of diffusion control for H(,2)S adsorption. A pore mouth poisoning model adequately describes the catalyst deactivation. The sulfur capacity of the nickel surface has been estimated as 8 x 10('14) S atoms/cm('2) Ni. The poisoned catalyst was partially regenerated by treatment in O(,2) at 475(DEGREES)C for an hour and reduction in H(,2) at 480(DEGREES)C for 2 hours. It was determined from the TPD experiments that, during this treatment, sulfur is removed in the form of SO(,2).

The mechanism of catalytic oxidative dehydrogenation of n-butane to n-butenes and butadiene over Ni-Sn and Mn-Li oxide catalysts has been investigated. The techniques used include kinetic modeling, stable isotopic tracers, temperature programmed desorption, x-ray diffraction, electrical conductivity, and alternate reduction-oxidation tests. The more selective catalyst for making the dehydrogenated products was Ni-Sn, an amorphous oxide mixture containing 47% Ni, 10% Sn, 6% P, 1% K, 4% S and 32% oxygen by weight. Its BET surface area is 49 m('2)/g. This catalyst gave only the products n-butenes, 1,3-butadiene, water and CO(,2) at temperatures up to 520(DEGREES)C. Over this catalyst n-butane is first converted to 1-butene which isomerizes to 2-butenes. These n-butenes may either be burned to CO(,2) or be oxidatively reduced to 1,3-butadiene which may further react to CO(,2). Kinetic modeling of this reaction developed a Mars-Van Krevelen type reaction expression for both the oxidative dehydrogenation of 1-butene and deep oxidation of 1-butene and 1,3-butadiene. This model incorporates a Langmuir expression in the rate of dehydrogenation for the competitive adsorption of hydrocarbons. Parity plots indicated that agreement between predicted and measured behavior for the deep oxidation reactions and oxidative dehydrogenation of 1-butene was quite acceptable. However, the five parameter rate expressions did not predict the reaction of n-butane with reasonable accuracy because isomerization to the 2-butenes was not included. Additional information on the rate of isomerization of the n-butenes and the rate of reaction of the 2-butenes would enable this model to be expanded to provide reasonable predictions. The activation energies for deep oxidation of 1,3-butadiene and 1-butene are 23 and 30 kcal/mole. Both the oxidative dehydrogenation of 1-butene and the reoxidation of the catalyst, by gas phase oxygen, exhibit activation energies of 45 kcal/mole. ('18)O tracer studies determined that the oxygen on the Ni-Sn catalyst is easily exchanged by CO(,2) and that the mobile oxygen amounts to 1.9 monolayers at 380(DEGREES)C and 3.5 monolayers at 452(DEGREES)C. A redox cycle is proposed as the mechanism of oxidative dehydrogenation of n-butane over the Ni-Sn catalyst. This involves using lattice oxygen to abstract the hydrogen atoms from the hydrocarbon to form the olefin or diolefin. The metal cation is reduced during the reaction of the hydrocarbon then is reoxidized by gas phase oxygen. This mechanism accounts for a C(,4)H(,9) species observed in the TPD experiments and is also consistent with the hydrogen-deuterium scrambling noted in the butene and butadiene products. The inhibition of the reaction rate by water is explained in this mechanism by adsorption-desorption equilibrium of water which limits the available oxygen sites. Since the Mn-Li catalyst (7/1 molar Mn/Li ratio; 2.5 m('2)/g) is far less selective (its major products are CO(,2) and water) than the Ni-Sn catalyst, this material was not studied extensively. The observed product distribution was sensitive to the reactor design with a shallow broad reactor giving a peculiar selectivity hysteresis that could not be explained.

The mechanisms and selectivities of several hydrogenation, isomerization, and partial oxidation reactions that occur over a zirconia catalyst were investigated. The thermal stability of the catalyst in air and in vacuum were determined. The catalyst was predominately cubic in crystal structure and had a BET surface area of 60 m('2)/mg. During the addition of a deuterium to 1,3-butadiene, the molecular identity of D(,2) is conserved, and all three n-butenes (C(,4)H(,6)D(,2)) are produced directly as primary products. The relative amounts of products formed at 75(DEGREES)C or less are trans>>1-butene>cis. The D(,2) addition is zero order in butadiene and first order in deuterium with an activation energy of 14.1 Kcal/mole. In contrast to this preference for 1,4 addition, the reduction of 2,3-dimethyl-1,3-butadiene produced almost singularly 2,3-dimethyl-1-butene, the 1,2 addition product. The isomerization of n-butenes and of 2,3-dimethyl-1-butene at 75(DEGREES)C or less are first order reactions. During the isomerization of n-butenes, there is no direct cis trans conversion. The presence of butadiene suppresses the isomerization rates. The isomerization occurs with an intramolecular hydrogen transfer and a kinetic isotope effect of about three. The isomerization reactions occur on different sites than those used for butadiene reduction The oxidation of carbon monoxide to carbon dioxide at 300(DEGREES)- 400(DEGREES)C has an activation energy of 17.1 Kcal/mole. This oxidation rate can be described by a Langmuir-Hinshelwood kinetic model with CO(,2) desorbing in a second order manner. Temperature programmed desorption of CO(,2) is also second order with an activation energy of 20.5 Kcal/mole. The CO oxidation is first order in CO and zero order in oxygen. Propylene can be oxidized to CO, CO(,2), and H(,2)O over zirconia. This reaction is zero order in propylene and first order in oxygen with an activation energy of 19.2 Kcal/mole. A constant CO/CO(,2) ratio of 1.07 is obtained in the product. Butane is oxidatively dehydrogenated to 1-butene at 375(DEGREES)- 460(DEGREES)C with an activation energy and 55.9 Kcal/mole. The OXD is first order in butane and zero order in oxygen. A side reaction to produce a constant CO/CO(,2) ratio of 1.41 occurs on separate sites. The deep oxidation is first order in oxygen and zero order in butane. The OXD reaction rate is suppressed by water, whereas the deep oxidation is not affected by the presence of gaseous water. The deep oxidation has an activation energy of 45.0 Kcal/mole. Isotopic oxygen exchange at 400(DEGREES)C indicated that at least 86% of the oxygen in the zirconia can be statistically scrambled with the oxygen in the carbon dioxide. This suggests that CO(,2) is dissociatively chemisorbed. A permanent carbonate equivalent to 2.7 x 10('13) molecules of CO(,2)/cm('2) is retained on the surface. Thermogravimetric experiments showed that a carbonaceous residue is formed on the zirconia by the cracking of butane. The residue can be removed by oxidation with the apparent adsorption of oxygen in two separate steps. This suggests that oxygen reacts directly with the carbonaceous residue. A frontier analysis is used to describe the hydrogenation and isomerization reaction mechanisms. Proposed mechanisms for oxidation and oxidative dehydrogenation are given.

Shear stress levels of the order of those associated with artifical heart valves and extracorporeal circulatory devices are sufficient to stimulate platelets to aggregate, to release chemicals that potentiate aggregation and blood coagulation, to cause impairment of platelet function, and to induce platelet lysis. There is evidence that certain drugs, called antiplatelet agents, alter platelet behavior in a way that reduces adhesion, aggregation, and secretion while causing no significant adverse effects on hemostasis. The objective of this study was to investigate the effects of antiplatelet agents on the response of platelets subjected to a well-defined shear stress field produced by a rotational viscometer. Antiplatelet agents studied include aspirin (acetysalicylic acid, or ASA), prostaglandin E(,1) (PGE(,1)) in combination with theophylline, and prostaglandin I(,2) (PGI(,2), or prostacyclin) in combination with theophylline. ASA inhibits the formation of thromboxane A(,2), a potent endogenous platelet aggregating agent, by irreversibly acetylating the platelet enzyme cyclo-oxygenase at its active site. PGE(,1) and PGI(,2) stimulate the platelet enzyme adenyl cyclase to convert platelet ATP to cyclic-AMP, which is a potent inhibitor of platelet aggregation. Theophylline inhibits the platelet enzyme phosphodiesterase, which breaks down cyclic-AMP to AMP. Theophylline, in combination with PGE(,1) or PGI(,2), maintains a high level of cyclic-AMP in the platelets and so potentiates the effects of PGE(,1) and PGI(,2). Samples of platelet-rich plasma were exposed to shear stress in a specially-designed rotational viscometer for 5 minutes at 23(DEGREES)C. Platelet response was characterized by the following measurements made before and after exposure to shear stress: (1)the particle count, which is used to indicate shear-induced platelet aggregation and lysis, (2)the level of ('14)C-radiolabelled serotonin in the plasma, which is used to indicate that the platelet release reaction and/or lysis has been induced, (3)the level of the enzyme lactic dehydrogenase in the plasma, which is used to indicate shear-induced platelet lysis, (4)the ability to aggregate in response to ADP, which indicates platelet functional capacity, and (5)the ability to aggregate in response to collagen, which provides additional information on platelet functional capacity. Results of the ASA study indicate that pretreatment of the platelets with 50 (mu)M ASA before exposure to shear stress caused little or no effect on shear-induced platelet aggregation and lysis. These results also indicate that formation of thromboxane A(,2) is not important in shear-induced platelet aggregation. The ASA pretreatment caused a small reduction of shear-induced serotonin release at stress levels equal to or greater than 200 dynes/cm('2), but not at lower stress levels. It was concluded that ASA does not cause a significant suppression of the response of platelets to the effects of shear stress. The results of the PGE(,1)-theophylline study, using final concentrations of 1 (mu)M and 100 (mu)M, respectively, were very similar to those of the PGI(,2)-theophylline study, using final concentrations of 0.01 (mu)M and 500 (mu)M, respectively. Both of these drug combinations caused a large reduction in the platelet aggregation response to a mechanical stimulus (shear stress) and to chemical stimuli (ADP and collagen). Thus, over a wide range of conditions, PGE(,1) (or PGI(,2)) and theophylline were much more effective than ASA in inhibiting platelet aggregation. It was also observed that PGE(,1) (or PGI(,2))-theophylline pretreatment caused an increase in shear induced platelet lysis and serotonin release at stress levels equal to or greater than 150 dynes/cm('2). This indicates that the PGE(,1) (or PGI(,2))-theophylline pretreatment caused increased platelet fragility.

Butene oxidative dehydrogenation (OXD) on a manganese iron oxide catalyst was studied in batch recirculation and microcatalytic pulse reactors at temperatures between 300C and 400C. Mechanistic features of the reaction were examined using ('14)C-labeled butadiene (Neiman method), deuterium labeled butene (isotopic tracer technique), and ('18)O-labeled carbon dioxide (oxygen isotope exchange) experiments. Temperature programmed desorption (TPD) experiments were used to evaluate desorption kinetics. Solid state changes in the catalyst were examined through x-ray diffraction, magnetization, magnetic susceptibility, thermogravimetric analysis, and electrical conductivity measurements. Reaction products consist of 1,3-butadiene, carbon dioxide, water, and butene isomers. Chromatographic analyses of the reaction products indicated negligible production of carbon monoxide during reaction. In addition, the TPD experiments demonstrated that carbon monoxide is readily oxidized over the catalyst. Initial rates of formation of butadiene and carbon dioxide are zero order in both oxygen and butene. The reactions are inhibited by product butadiene, where the low conversion data is modeled adequately by a Langmuir-Hinshelwood type rate expression. The activation energy for butadiene formation is 35.2 Kcal/mole, and that for carbon dioxide production is 37.5 Kcal/mole. Microcatalytic pulse experiments carried out in the absence of gas phase oxygen indicated that the reactions may proceed by consuming lattice oxygen. Perdeuterated butene is less reactive than non-deuterated butene. Comparison of the rates of formation and analysis of isotopic composition of the products revealed significant kinetic isotope effects for both OXD and isomerization (Isotope effect for OXD = 2.1, Isotope effect for cis-2-butene to 1-butene isomerization = 1.7, both at 412C). Therefore, carbon-hydrogen bond cleavage is considered rate limiting. Experimental data are consistent with an oxidation-reduction cycle involving either Fe('3+) or Mn('2+). Butene and oxygen molecules may adsorb into surface anion vacancies associated with either cation. The absence of intermolecular hydrogen-deuterium exchange during isotopic tracer experiments indicates that OXD and isomerization reaction rates are much greater than surface diffusion rates. A deactivation mechanism consistent with solid measurements is proposed. Major crystallographic transitions occur during reaction and pretreatment operations in agreement with the thermodynamic phase relations for the iron-manganese-oxygen system. X-ray diffraction measurements confirmed that the catalyst aging process parallels the shift from a spinel to a hexagonal crystal structure. This change corresponds to the irreversible oxidation of Mn('2+) in the virgin catalyst to Mn('3+) in the aged catalyst.

This research develops a theoretically based corresponding states procedure which predicts mixture properties accurately. This procedure separates any dimensionless residual thermodynamic property into two parts: One part is a contribution from molecular repulsion and the other is a contribution from molecular attraction. This repulsion can be represented by either a mixture of hard spheres or hard convex bodies. The two forms are compared in this work. The attraction contributions contain the symmetrical part from non-polar interactions and another asymmetrical part which comes from permanent dipole moments, quadrapole moments, or other polar effects. Each of these two attraction contributions in a mixture is determined from a pure reference fluid by way of some suitably defined pseudoparameters. The composition dependence of the pseudoparameters is derived from either the hard sphere expansion of the hard convex body expansion method. Temperature and density dependent shape factors are used to multiply the individual critical properties in the pseudocriticals to establish conformality between individual constituents and the reference. A new analytical method of defining optimal values for the hard core dimensions is developed for each pure component from its equation of state. This new conformal solution theory gives good agreement with experiment and always gives better results, especially for K-value calculations, than the results determined from the ordinary equation of state with the usual empirical mixing rules. This work has confirmed that this new theory gives a better description of composition dependence than the empirical combinational rules. The hard convex body expansion method does not give significant improvement over the hard sphere expansion results for a methane-propane mixture at the conditions investigated in this work. A reliable equation of state which describes the behavior of the pure component accurately is essential to the computation. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI

Perturbation chromatography or gas-liquid partition chromatography (GLPC) provides a powerful tool for making physicochemical measurements. In this investigation GLPC was applied to study the vapor-liquid equilibrium behavior of light gases in nonvolatile coal liquid model compound solvents at high temperatures and high pressures. Improvements made in existing GLPC techniques include: the use of a high pressure tandem proportioning pump to give precise control of the carrier gas flow rate and low pressure drops; a high pressure ionization chamber to detect the injection of very dilute radioactive sample gases; and the use of a microcomputer to provide instantaneous integration and very precise retention times of the chromatographic peaks. Infinite dilution K-values for methane, ethane, propane, n-butane, carbon dioxide, and hydrogen sulfide in hydrogen-dibenzofuran systems were obtained at 100 and 125 C and up to 800 psia. Infinite dilution K-values for the same light gases in hydrogen-9-methylanthracene systems were obtained at 100, 125, 150, 175, and 200 C and up to 3000 psia. Henry's constants were determined for the light gases in 9-methylanthracene. Second cross virial coefficients and vapor phase infinite dilution fugacity coefficients were calculated for methane, ethane, propane, and n-butane in hydrogen. These results were combined with the experimental K-value measurements to obtain Henry's constants in hydrogen-9-methylanthracene mixtures of fixed liquid compositions. Infinite dilution heats of solution of the solute gases in the mixtures were calculated.