William J. Ward

Carbon Dioxide-Oxygen Separation: Facilitated Transport of Carbon Dioxide across a Liquid Film

An immobilized film of an aqueous bicarbonate-carbonate solution was developed which was 4100 times more permeable to carbon dioxide than to oxygen. The carbon dioxide transport was reaction-rate limited, and thus it could be increased by addition to the film of catalysts for the hydrolysis of carbon dioxide.

Facilitated transport in ion-exchange membranes

Abstract Ions were used as mobile, membrane-bound carriers for selected gas species, these being introduced as the counter ions in ion-exchange membranes. For example, Ag+ ions were used as carriers for ethylene, and singly protonated ethylenediamine cations as carriers for CO2, both in cation-exchange membranes. Such preparations have the advantage that the carrier cannot easily be forced out of or washed out of the membrane, since it is retained there by strong electrostatic forces. This could be useful in practical gas separations, giving longer operating life under certain adverse conditions.

Ultrathin silicone/polycarbonate membranes for gas separation processes

Abstract Uniform, defect-free silicone/polycarbonate membranes as thin as 0.015 μ have been formed by spreading solutions of the copolymer on water surfaces. The membranes were readily applied to support materials. Composite membranes formed from several laminations of ultrathin membrane on a support were readily handleable and may provide the basis for practical gas separation processes. Two such processes are (1) the production of 30% oxygen-enriched air, which would require less energy than blending air with oxygen from a modern low-temperature air separation plant, and (2) the on-board generation of nitrogen-enriched air for inerting aircraft fuel tank vapor spaces and vent line.

Gas barrier improvement using vermiculite and mica in polymer films

Abstract The objective of this work was to develop a class of barrier materials based on filling a polymer film with impermeable plates aligned in the plane of the film. Mica and vermiculite fillers were developed for this application, and permeability reductions of more than two orders of magnitude were achieved in solvent cast films. The fillers will not survive extrusion but could provide the basis for high barrier coatings.

Catalysis of the Rochow Direct Process

Abstract The synthesis of dimethyldichlorosilane by the “Direct Process” is at the heart of the silicone industry. The Direct Process has been the object of intensive research and development over the past 40 years, yet there are aspects of the reaction that remain in an elementary state of understanding. The goal of this work was the discovery of previously unknown variables, including trace elements, which affect product distribution and rate. Fluidized and stirred bed reactors were used. Trace quantities of tin were found to affect the Direct Process profoundly, and the effects of tin and zinc were synergistic. A catalyst system consisting of copper, zinc, and tin was discovered which yielded 90% dimethyldichlorosilane with nearly complete silicon utilization. This is a major improvement over the best previously reported performance.

Rayleigh-benard convection in an electrochemical redox cell.

Damped voltage oscillations occur when current steps are applied to a cell consisting of a thin layer of Fe111/Fe11 electrolyte sandwiched between horizontal, parallel, platinized platinum electrodes. The upper electrode must be the anode, and the magnitude of the current must be larger than a threshold value. The oscillations signal the onset of convection in the fluid. The experiment provides a new method for investigating transient convection processes.

Thermal Conductivity Reduction of Polyurethane Insulating Foam by In Situ Carbon Dioxide Removal

Polyurethane foam of the type used for most refrigerator insulation is currently blown in the United States with a mixture of diclorofluoroethane (R-141b), and CO2. The object of this work has been to reduce the thermal conductivity of this foam by passively removing CO2 from the cell gas of the foam. This work is applicable to foams blown with R-141b, R-356, cyclopentane, and other low-boiling liquids plus CO2. In work with hand-mixed foams we demonstrated that NaOH in the form of beads or powder is an effective material for in situ CO2 removal from foam. After removal of CO2, originally present at 14%, foam thermal conductivity at refrigerator operating conditions was reduced 9%.

Membrane Gas Separations—Why and How

Significant advances are being made in the areas of membrane fabrication and packaging, and as a result it is reasonable to expect an increasing number of commercial membrane gas separation processes will be available. Therefore process engineers need to have an understanding of this area. To this end, the subjects to be covered in this chapter are: (1). An analysis showing how the basic process variables of pressure difference across the membrane, pressure ratio across the membrane, and membrane thickness determine system performance. (2) A discussion of available types of membranes, and membrane packages. (3) An introduction to carrier transport membranes. This is a new class of membranes, not yet commercially available, which promises much high er performance than conventional polymeric membranes.

Measurement of Co2 Permeability in Polymer Films

A simple and sensitive method for measuring CO2 permeability in polymer films has been developed. The method is based on the use of 14CO2. At time zero 14CO2 is injected on the high pressure side of the cell. Permeation is monitored with a Geiger counter which senses 14CO2 on the low pressure side of the cell. The counts/time on the low pressure side are proportional to the total concentration of CO 2 which has diffused through the film. With the known source concentration the volume-time curve is constructed and the permeability and time lag are calculated. The system sensitivity as it is presently configured is on the order of 10-15 em3(STP).cm/cm2.sec.cm Hg. Results are presented for a measurement of a 0.025 cm polycarbonate film.