Adsorption Equilibrium and Kinetics of Methane and Nitrogen on Carbon Molecular Sieve

Abstract

Knowledge of adsorption equilibrium and kinetic data is essential for the design of an adsorption process. In this work, the adsorption equilibrium isotherms of methane and nitrogen are reported at 303, 323, and 343 K over the pressure range from 0 to 700 kPa by a gravimetric system on a carbon molecular sieve (CMS-131510). Methane is preferentially adsorbed. The adsorption capacity at 303 K and 700 kPa is 1.91 mol/kg for methane and 1.01 mol/kg for nitrogen. Experimental data obtained were fitted with the multisite Langmuir model and Toth model. The adsorption kinetics of pure gas was studied by a batch uptake experiment at several different surface coverages within the pressure range of 0−100 kPa and in the same temperature range covered by the equilibrium isotherm. The adsorption rate of both gases is found to be controlled by the surface barrier resistance at the mouth of the micropore and diffusion in the micropore interior. The dual resistance model employed in the simulation can successfully describe the uptake curves. The temperature and concentration dependences of kinetic parameters were also studied. A very high kinetic selectivity was observed. The effect of micropore distribution on the transport parameters is discussed in detail. Binary breakthrough curves were determined, and an enrichment of 50% for methane in the first few seconds was observed. The data reported in this work can be used for the future modeling of adsorption process for the separation of methane and nitrogen on this CMS material.

Adsorption kinetics of CO2, CO, N2 and CH4 on zeolite LiX pellet and activated carbon granule

“…Therefore, studies have analyzed the contributions of macropores and micropores in the rate-determining step of N 2 , CH 4 and CO 2 in zeolite 4A, 5A, CaX and 13X pellets (Ahn et al 2002(Ahn et al , 2004Silva et al 2012;Hu et al 2014). In a carbon molecular sieve, controlled micropores significantly affect the adsorption kinetics, and the kinetic difference among adsorbates strongly depends on molecular size and adsorption affinity (Bae and Lee 2005;Giesy and LeVan 2013;Yang et al 2014). There are few studies of adsorption kinetics of activated carbon granules with wide pore size distribution from micropores to macropores (Gray and Do 1991;Himeno et al 2005).…”

Role of porosity and polarity of nanoporous carbon spheres in adsorption applications

“…† The Töth model is a semi-empirical expression that effectively describes many systems with submonolayer coverage and presents correct behavior at both the low and high pressure ends, reducing deviation errors between experimental data and calculated values of adsorption equilibrium. [44][45][46][47][48][49] It is noteworthy that the parameter n presents the system heterogeneity. 22,[44][45][46][47][48][49] If it the heterogeneity parameter n becomes unity, it is identical to the Langmuir model presenting homogeneous surface; in contrast, if this parameter is lower than unity, the more heterogeneous system is expected.…”

“…[44][45][46][47][48][49] It is noteworthy that the parameter n presents the system heterogeneity. 22,[44][45][46][47][48][49] If it the heterogeneity parameter n becomes unity, it is identical to the Langmuir model presenting homogeneous surface; in contrast, if this parameter is lower than unity, the more heterogeneous system is expected. [44][45][46] According to the heterogeneity parameters of CH 4 on the carbon samples (Table S2 †), the values are in the range 0.5-0.67, inferring that the surface heterogeneity of carbon surfaces strongly favors CH 4 adsorption.…”

“…A good relationship (R 2 ¼ 0.97) between the q m values and SSAs of RFC samples is identied, as has been reported in the literature. [49][50][51][52][53] Thus, the superb q m value (101 mg g À1 ) for RFC_C390 is attributed to ultrahigh SSA of 3958 m 2 g À1 derived from a prolonged CO 2 activation process. When the q m (Fig.…”

Supercritical Adsorption Based CO<sub>2</sub> Capture from N<sub>2</sub>/CO<sub>2</sub> Mixture by Activated Carbon and Carbon Molecular Sieve

“…The selectivity based on steric effect or equilibrium or kinetics is taken advantage of in the adsorption separation process [34]. Adsorption separation based on kinetic selectivity has a potential to capture CO 2 from N 2 /CO 2 mixture after successful separation of N 2 /O 2 , CH 4 /CO 2 and CH 4 /N 2 on carbon molecular sieve CMS [35][36][37][38][39], Using an economic adsorbent also raises the process efficiency of cost and of energy for CO 2 capture. The carbogenic adsorbents are lightweight, elastic, heat and electric conductive (may be used in electric swing adsorption), cheap, easy-shapeable from precursors, higher specific surficial, thermal and chemical stable, durable, non-moisture sensitive, stable under the impurity, environment-protective and energy saving, it solves many difficulties of the other adsorbents possess in the process of implementation [40][41][42][43][44].…”