Brian Hanley

Production of oxygen enriched air by rapid pressure swing adsorption

A novel rapid pressure swing adsorption (RPSA) process is described for production of 25–50% oxygen enriched air. The embodiment consists of one or more pairs of adsorbent layers contained in a single adsorption vessel. The layers undergo simultaneous pressurization-adsorption and simultaneous depressurization-purge steps. A total cycle time of 6–20 seconds is used. The process yields a very large specific oxygen production rate and a reasonable oxygen recovery for production of 20–50 mole% oxygen enriched gas.It is demonstrated by a simple mathematical model of isothermal single adsorbate pressure swing ad(de)sorption concept on a single adsorbent particle that the specific production rate of a PSA process cannot be indefinitely increased by reducing the cycle time of operation when adsorbate mass transfer resistances are finite.

Fractionated Vacuum Swing Adsorption Process for Air Separation

Abstract A novel adsorptive process for air separation using a zeolitic adsorbent is described. The process essentially consists of three simple cyclic steps, and it can be used for simultaneous production of an 80—90% oxygen-enriched gas and a 98 + % nitrogen-enriched gas from ambient air. Successful operation of the process requires the use of a zeolite which exhibits high nitrogen adsorption capacity and selectivity from air. The role of nitrogen adsorption selectivity of the zeolite in the vacuum desorption process is examined, and experimental performance data for the air separation process are reported.

The Behavior of the Tracer Diffusion Coefficient of Polystyrene in Isorefractive "Solvents" Composed of Poly(Vinyl Methyl Ether) and o-Fluorotoluene

SummaryIn this paper, we describe and use a relatively new technique — dynamic light scattering from refractive index-matched ternary solutions-to study a quantity very closely related to the self-diffusion coefficient in binary systems. We refer to this quantity as the tracer diffusion coefficient. This tracer diffusion coefficient is expected to behave in much the same way as the self-diffusion coefficient, in terms of its concentration and molecular weight dependencies. In this study, we use two compatible polymers, polystyrene and poly(vinyl methyl ether), and a solvent, o-fluorotoluene, chosen specifically because its refractive index matches that of the poly(vinyl methyl ether). The technique is advantageous in that it allows the experimenter to vary independently the molecular weight of both the probe and “invisible” matrix polymers, their individual molecular topologies, and the overall polymer concentration with relative ease. No special chemical tagging is required, although it must be borne in mind that we are not measuring self-diffusion but the diffusion of a dissimilar tracer. Our experiments probe the diffusion of linear polystyrenes in matrices composed of linear poly(vinyl methyl ether)/o-fluorotoluene. Our results show a crossover from non-free draining (Zimm) to free draining (Rouse) hydrodynamic behavior of polystyrene as the concentration of the invisible poly(vinyl methyl ether) making up the matrix is increased.

An experimental study of polymer diffusion in concentrated solution: implications for diffusion in polymerization

Abstract The Trommsdorf or gel effect in free radical polymerization is due to the fact that the termination reaction becomes strongly diffusion controlled above a critical concentration associated with the onset of molecular entanglements. Therefore, an understanding of polymer self-diffusion in entangled systems becomes essential to understanding the Trommsdorf effect. Our group has previously proposed a molecular model for the gel effect which uses a specific theory for polymer diffusion (reptution). The present work represents an experimental attack on the same problem Experimental studies of polymer self-diffusion in entangled systems are scarce. Quasielastic light scattering from ternary systems composed of solvent(l)-polymer(2)-polymer(3), in which species (3) is isorefractive to the solvent (i.e. 0n/0c 3 = 0), offers an attractive way to study the tracer diffusion coefficient of species (2) in a binary mixture of composition c 3. In regimes of low momentum transfer (qR G < 1,) where q is the scatt...

The effect of polydispersity on the analysis of optical tracer diffusion experiments

SummaryThe recently developed technique of dynamic light scattering from ternary solutions, in which the solvent and matrix polymer are isorefractive, can provide extensive information about the translational diffusion of polymers in semidilute and concentrated solutions. However, the strong molecular weight dependence of diffusion in these regimes has a substantial effect on the observed autocorrelation functions. It is demonstrated that the traditional cumulants approach is inadequate for extracting the desired decay rates, even for narrow distribution samples (i.e. Mw/Mn≅1.05). Alternative methods of analysis are proposed, and implications for other polymer diffusion experiments are discussed.

The effect of polydispersity on the analysis of optical tracer diffusion experiments. II: Intramolecular interference

SummaryThe effect of intramolecular interference on the wave vector dependence of the average tracer diffusion coefficient in a dynamic light scattering experiment from an optically matched ternary system in which the tracer polymer reptates is examined using a Schulz molecular weight distribution and the Debye interference function for random coils. The average tracer diffusion coefficient in a system in which the tracer is polydisperse is shown to vary continually with q. This variation can be quite substantial for moderate polydispersities even in the regime q¯Rg(n)<1. It is shown that a two parameter linear fit of 〈Γ〉 versus q2 data will have a negative intercept and that the apparent q power law dependence of the average decay rate will be greater than 2.