Separation of Methane and Nitrogen by Adsorption on Carbon Molecular Sieve

Salix viminaliswood as a new precursor for manufacturing of carbon molecular sieves for effective methane/nitrogen separation

“…Some authors [6] state that, for molecular sieves, diffusion through pore entry is adsorption/desorption rate-limiting, and the order of the adsorption activation energy E ADS is strongly influenced by the atomic/molecular size of adsorbate. Successful passage through pore entry (in both directions: adsorptiondesorption) is a key factor in molecule discrimination by shape as suggested and proven in several studies [6,32,33,34,35].…”

“…Extensive studies [6,31,32] on the mechanism of adsorption on CMS have led to the conclusion that two basic factors are essential for the overall process: Factor (1) -entering the pore and passage through the pore neck (repellent potential barrier at the pore entrance) and Factor (2) -diffusion along the pore walls (spot-to-spot transfer of molecules). In many cases, the adsorption/desorption rate and velocity are limited by the entry through the pore aperture, which may be considered as a "geometric factor" which is in fact an interaction with the repellent potential barrier at the entrance.…”

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

“…3) Diffusion coefficients D c of the whole particle on each temperature is considered as constant during each corresponding kinetic test [62]. Taking the initial and boundary conditions as equation- (4), -(5) and -(6) for the adsorbate, the analytical solution for equation- (3) is as equation- (7) [63,64], where, m is the amount adsorbed at the time t (mmol/g), m 0 is the amount adsorbed at the equilibrium state (mmol/g), q(r, t) is the adsorbate concentration (mol/m 3 ), t is the time of diffusion (s), r c is the radial coordinate, The measured radius of particle of the activated carbon Yigao-A and of the carbon molecular sieve CMS-200 is r c (Yigao-A) =1.05 mm and r c (CMS-200) =1.6 mm, n is the natural number. The fitting of the Fickian model for N 2 adsorption and for CO 2 adsorption on the activated carbon Yigao-A and on the carbon molecular sieve CMS-200 is demonstrated in Figure 9, 10, 11 and Figure 12.…”

“…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].…”

Carbon Molecular Sieves for Hydrocarbon Separations by Adsorption

“…In these works, poor purity was obtained because the feed has high nitrogen molar fractions (>40%) for landfill gas applications. We already measured adsorption characteristics of pure methane and nitrogen on CMS 3K from Takeda [14], which has presented a good kinetic selectivity towards nitrogen, even when methane is the most adsorbed gas. The challenging issue of a PSA process for these separations is that the size of the molecules involved is very close and they have very similar energetic characteristics.…”