Steric effects in nitrogen adsorption by mordenite

Conference · Mon Mar 01 04:00:00 EST 1982 · Am. Chem. Soc., Div. Pet. Chem., Prepr.; (United States)

OSTI ID:6386875

Hayhurst, D T; Sefcik, M D

Zeolites are well known for their ability to adsorb a large variety of gases, including even highly volatile nonpolar permanent gases. Nitrogen is among the most strongly adsorbed non-polar gas; in fact, among some of the earliest observations on adsorptive separation of gaseous mixtures was the selectivity shown by several zeolites for nitrogen from air. Early work of Barrer, McKee and Domine and Hay showed that calcium A, calcium X, mordenite and several types of natural zeolites can be used to enrich air by a selective adsorption of nitrogen. Several pressure-swing-adsorption processes utilizing zeolite adsorbents have been developed which yield a product containing up to 95% oxygen at rates of up to 20 tons per day. The selective adsorption of nitrogen over oxygen is not a true molecular sieving effect since nitrogen (3.64A) is larger than oxygen (3.46A). Thus, the increased affinity of many zeolites for nitrogen can be ascribed to a greater heat of adsorption for nitrogen than for oxygen. The initial heat of adsorption in zeolites adsorbents can be partitioned into contributions from repulsive and dispersive forces, polarization energy and electrostatic interactions arising from dipole and electric quadrupole moment interactions with electric fields in the zeolite. At higher concentrations of adsorbates, interactions between adsorbates must also be considered. If, due to geometrical constraints in the zeolite, nitrogen is adsorbed into sites which reduce or eliminate its rotational freedom and, if the nitrogen quadrupole is aligned with the cation field gradient than a significant increase in the value of 0 /SUB f-q/ may be expected.

• Research Organization: Cleveland State Univ., Cleveland, OH
• OSTI ID: 6386875
• Report Number(s): CONF-820304-
• Conference Information: Journal Name: Am. Chem. Soc., Div. Pet. Chem., Prepr.; (United States) Journal Volume: 27:2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
ABSORPTION
ALKALINE EARTH METALS
CALCIUM
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
DENITRIFICATION
ELEMENTS
GASEOUS WASTES
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
METALS
MINERALS
MORDENITE
NITROGEN
NONMETALS
SILICATE MINERALS
SORPTIVE PROPERTIES
SURFACE PROPERTIES
WASTES
ZEOLITES