Thomas Richard Gaffney

Porous solids for air separation

Abstract Recent advances have been made in research on carbon molecular sieve and zeolite adsorbents used in the non-cryogenic production of nitrogen and oxygen. Preparation methods that allow stringent control of porosity, density, and surface properties have resulted in carbon molecular sieve adsorbents with higher capacity and selectivity for nitrogen production. Recently, a new generation of mixed-cation zeolite adsorbents with high N 2 /O 2 selectivity and improved stability has been developed for oxygen production.

Preparation of carbon molecular sieves, I. Two-step hydrocarbon deposition with a single hydrocarbon

Abstract A process is described for preparing a carbon molecular sieve that is suitable for the kinetic separation of gases, such as oxygen from nitrogen. The process involves modifying a carbon support, having a majority of micropores with an effective pore size of about 4.5 to 20 A, using a two-step process in which the sieve is contacted with two different concentrations of a volatile carbon-containing organic compound. The concentration of the carbon-containing compound used in the first step is larger than that in the second step, so that the pore openings of the micropores of the support are narrowed successively in two distinct steps without excessively filling the micropores themselves.

Granular carbon molecular sieves

Abstract Any future carbon molecular sieve (CMS) for use in the commercial production of N2 should have a high volumetric O2 equilibrium capacity. We developed a procedure for producing a high capacity coconut shell char that can be converted into a high capacity CMS for air separation. Granules of coconut shell char are heated in flowing inert gas at about 2 to 12°C per minute to a peak temperature of 775° to 900°C. After holding from 1 to 8 hours, the char is cooled in an inert gas atmosphere. The granular char thus produced has an oxygen capacity in excess of 8.0 cc/cc. Contacting the char with an oxidizing atmosphere containing CO2, H2O, or O2 at 650° to 900°C increases the O2 capacity to greater than 9.0 cc/cc. The coconut shell char can be converted to a CMS by treatment with a volatile carbon-containing organic compound that, when pyrolyzed, deposits carbon within the interior of the carbon granules. The granular CMS thus produced can be used in a nitrogen pressure swing adsorption column without the need for pelletization.

High micropore volume low silica EMT-containing metallosilicates

The present invention is a composition, a synthesis of the composition and a method of using the composition for selectively adsorptively separating nitrogen from oxygen wherein the composition is a crystalline EMT with a Si/Al ratio less than 2.0 and a micropore volume determined in the sodium and/or potassium form of at least 0.20 cm3 /g and a lithium cation exchange of at least 80%, preferably including an intergrowth with a crystalline FAU structure, wherein the pure or intergrowth compositions have the chemical formula: M.sub.2/n O:X.sub.2 O.sub.3 :(2.0 to <4.0)SiO.sub.2 wherein M=one or more metal cations having a valence of n, and X is selected from the group consisting of aluminum, gallium and boron, preferably aluminum.

Defining effective microporosity in carbon molecular sieves

Abstract A pseudo equilibrium method is described for establishing the micropore distribution in carbon molecular sieves (CMS) having micropore sizes below 6 A. The method uses a series of carefully selected molecular probes varying in their minimum Van der Waals diameter between 3.7 and 6.0 A. Various small-pore zeolites were used to validate the method. Over the critical micropore size range these probes can establish the “effective” microporosity which can be modified by post-treatment to produce an O 2 -selective CMS useful for air separation. This method coupled with kinetic measurements of O 2 and N 2 uptake indicates that pores larger than 4 A are not highly O 2 -selective. Results from these molecular probe studies in combination with porosimetry and pycnometry measurements show that the O 2 -selective carbons have an unusual bimodal pore distribution with no significant mesoporosity. We found obtaining pore distributions from equilibrium analysis of N 2 or O 2 isotherms at cryogenic conditions was inappropriate on these carbons. The study clearly demonstrates the importance of the method which monitors the size and relative amounts of micropores which are O 2 -selective.