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Clinoptilolites were tailored through controlled ion exchange with both indigenous cations, such as Na+ and Mg+, and other cations, such as Li+, Sr2+, and Ce3+. These partially exchanged clinoptilolites are characterized through neutron activation analysis, and the adsorption isotherms and diffusion rates of nitrogen and methane were measured. Partially exchanged Ce clinoptilolite showed reversal of equilibrium selectivity from nitrogen to methane as the extent of Ce3+ exchange increased, while mixed Na/Li (also referred to as partially exchanged Li+) clinoptilolites showed reversal of equilibrium selectivity as the extent of Li+ exchange decreased. High-pressure isotherms on mixed Mg/Na clinoptilolites and partially exchanged Ce clinoptilolites were measured through the differential adsorption bed technique. Pressure swing adsorption (PSA) simulations were performed on a two-stage PSA process operating on a five-step PSA cycle for the tailored clinoptilolite sorbents. The simulation results of tailored clinoptilolites were compared against those of the commercial sorbent ETS-4 and the purified clinoptilolite. The tailored clinoptilolites gave slightly less recovery than purified clinoptilolite and ETS-4 but showed 50% improvement in product throughput, making tailored clinoptilolites suitable for use in a PSA process for nitrogen/methane separation.

Organonitrogen compounds are present in commercial fuels after the hydrodenitrogenation process in quantities up to a few hundred ppmw N. Polyaromatic hydrocarbons (PAH) are present in significant quantities (1.4−11 wt %) in transportation fuels depending on both the region and season. In this work, the effect of organonitrogen (quinoline, carbazole) and PAH (naphthalene, fluorene, phenanthrene) compounds on desulfurization by π-complexation with Cu(I)Y zeolite was studied and found to be moderate. The high selectivity for sulfur was not affected because a very low-sulfur fuel (<0.1 ppm S) was produced prior to the sulfur breakthrough. The effects of these compounds were quantified by the decrease in desulfurization capacity of Cu(I)Y in the presence of each additive at a concentration of 1.6 mmol/L in a model fuel (100 ppmw S dibenzothiophene in 20 wt % benzene + 80 wt % n-octane). The extent of inhibition in desulfurization capacity by these compounds was found to follow the order carbazole > quinoline > phenanthrene > fluorene ≈ naphthalene. Ab initio molecular orbital calculations were also performed to provide an understanding of the inhibition effect. The observed order of inhibition was in good agreement with that predicted by molecular orbital calculation results.

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The π-complexation sorbents are the best sorbents for bulk olefin/paraffin separation and purification of normal R-olefins. Hydrogen produced during cracking operations would remain in small or trace amounts in the process streams. The effect of hydrogen exposure on Ag + -exchanged Y zeolite (AgY) and monolayer-dispersed AgNO 3 /SiO 2 (π-complexation sorbents) on olefin adsorption was studied by using accelerated tests. Hydrogen exposure could severely deactivate the π-complexation sorbents for adsorption of ethylene, 1,3-butadiene, and 1-butene. XPS analysis indicated that the Ag + ion responsible for π-complexation was partially reduced, hence, the deactivation. It was found that the deactivated sorbents could be rejuvenated by mild oxidation. The reoxidation of the H 2 -exposed AgY samples were carried out under different oxidation conditions to locate the optimum conditions. The treatment of the H 2 -exposed samples to 0.13 atm of O 2 in He at 350 °C for 0.5 h was the best reoxidation condition achieved in this study.

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Commercial type X zeolites (Linde 13X) are nitrogen selective. Oxygen is the less abundant component in air; hence oxygen selective sorbents are desired for air separation. Mixed Na-Ce type X zeolites containing different ratios of Ce 3+ /Na + ions are prepared by partial ion exchange of commercial X zeolite. The adsorption isotherms of nitrogen, oxygen and argon are measured and the pure-component selectivity ratios are compared and analyzed against commercial zeolites (13X) for air separation. Oxygen selectivity over nitrogen (∼1.5) and argon (∼4.0) are seen for mixed Na-Ce type X zeolite (Si/Al = 1.25; Ce 3+ /Na + < 4.0) from Henry's constant determined from low pressure adsorption measurements. The oxygen and nitrogen isotherms cross over for mixed Na-Ce type X zeolite (Si/Al = 1.25; Ce 3+ /Na + < 4.0), and the pressure at which cross they over increases as Ce 3+ /Na + approaches 1. The oxygen selectivity as claimed in the patent by N.V. Choudary, R.V. Jasra, and S.G.T. Bhat (US Patent no. 6,087,289, 2000) is seen only at very low pressures in the volumetric adsorption measurement and the hydrogen treatment of the Ce-exchanged samples have no effect on the adsorption characteristics.

Natural gas is the fuel of choice for fuel cell applications due to its extensive existing supply infrastructure. However, the sulfur level in the natural gas needs to be reduced to less than 0.1 ppm for use in the fuel cells. TDA has developed SulfaTrap TM series of sorbents to effectively remove sulfur by adsorption from natural gas streams and has been carrying out field demonstrations with fuel cell developers for the past two years. In this paper we have compare the performance of the TDA's SulfaTrap sorbents with commercially available adsorbents.