Tailored Clinoptilolites for Nitrogen/Methane Separation

Abstract

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.

Enrichment of coal‐bed methane by PSA complemented with CO2 displacement

“…Details of the breakthrough experiment and calculation of the separation coefficient were described in the literature. 26 The carbon was dried in vacuo at 393 K for 8 h before experiments. All gases used in the experiments were provided by Liufang Gas Co. Tianjin.…”

“…As a bottom-product, both concentration and recovery of methane are limited not to mention the loss of pressure. Fortunately the kinetic property difference of the two gases allows methane to be collected at column top 14 when carbon molecular sieves (CMS), [15][16][17] synthesized zeolites, [18][19][20][21] clinoptilolites and their modified species [22][23][24][25][26] are used as adsorbents. Because N 2 shows more adsorption preference over these materials, CH 4 is obtained at column top.…”

Effect of carbon pore structure on the CH4/N2 separation

“…The adsorption selectivity may be shown either in equilibrium adsorption or adsorption kinetics. Although remarkable progress has been made in the latter respect (Jayaraman et al 2004(Jayaraman et al , 2005Kouvelos et al 2007), the industrial PSA separation still relies on the equilibrium difference on activated carbons, though the separation selectivity is not satisfactory (Fatehi et al 1995;Baksh et al 1990;Buczek 1996). Here we investigated the effect of structure parameters of porous carbon on the separation coefficient between CH 4 and N 2 , and a series of carbon samples were prepared at different extent of activation.…”

Binary adsorption behaviour of methane and nitrogen gases

“…This is necessary to obtain pure petroleum products and achieve a high heating value for methane. Traditionally, the CH 4 -N 2 separation is practiced by cryogenic distillation, involving expensive high pressure units and large requirements of energy [6]. Adsorption separations are used widely among other separation processes as they tend to utilize fewer resources including energy and are highly efficient [7][8][9][10][11][12].…”