Microporous carbons chemical vapor deposition

Wang L-J and Chau-Nan Hong F. Carbon-based molecular sieve membranes for gas separation by inductively-coupled-plasma chemical vapor deposition. Micropor. Mesopor. Mat. 2005 77 167-174. 

Pedrero et al. - prepared CMS by chemical vapor deposition on a lignin-based microporous carbon. The textural characterization of the CMS was carried out by adsorption of N2 at 77 K and CO2 at 273 K. The sieving properties of the CMS were determined by the kinetics of adsorption of O2/N4 and CO2/CH4 mixtures. The adsorption capacities of the carbon for O2 and CO2 decreased slightly with deposition. When the pyrolytic carbon deposited was 0.3%, the adsorption of nitrogen was reduced drastically, and the adsorption of CH4 was impeded. The oxygen selectivity (ratio of O2 to N2 adsorbed in 2 min.) was increased rapidly to a value of 6, while the decrease in the adsorption of N2 was only 20%. Similar behavior was observed in the case of CO2/CH4 mixtures. 

Pore size and surface functionality of active carbon fiber (ACF) were modified by design by selective chemical vapor deposition (CVD) where the deposition temperature was selected carefully (1). In this system, particular organic compounds, like benzene, are useful due to their thermal stability (2). The pore structure of ACF was another key factor which influences strongly its performance after CVD. The ACF of low activation, which carries micropores in majority, showed molecular... 

Instead of the PA precursors, Hayashi et al. deposited a polyimide film on the outer surface of a porous alumina tube by dip-coating three times. After imidization and pyrolyzation at 973-1073 K, the carbon membranes were fabricated on porous alumina tube. The enhancement of the volume of micropores accessible to smaller molecules has been observed. Hayashi et al. obtained an optimal pyrolysis temperature of 973 K and maximum permeance was achieved. In order to improve selectivity, a carbon layer was further deposited on the resultant supported carbon membrane by chemical vapor deposition (CVD) of propylene at 923 K.The CVD process favors the deposition of carbon in micropores, which explains the increase of the selectivity of CO2/N2 from 47 to 73. 

Kyotani and coworkers [81] systematically demonstrated the preparation of micro-porous carbons using zeolite templates, whereas early studies [82-84] described the pyrolysis of carbon precursors to make carbon materials in the presence of zeolites. Subsequently, Mallouk and coworkers [85] employed zeolites Y, L, and P as templates to prepare microporous carbons with a specific surface area as high as 1580 m /g. It was reported that the zeolite template has a direct relationship with the structural and topological properties of the resultant carbon. Rodri-guez-Mirasol et al. [71] described the preparation of microporous carbons with a wide distribution of pore sizes, well-developed mesoporosity, and high adsorption capacity. Zeolite Y was used as template, and a chemical vapor infiltration method was employed to deposit carbon in the template pores. It was found that the apparent surface area of the resultant carbons increased with increasing deposition temperatures. Meyers et al. [72] synthesized porous carbon materials with a surface area of about 1000 m /g using zeolites Y, p, and ZSM-5 as templates and acrylonitrile, FA, pyrene, and vinyl acetate as carbon precursors. The template-encapsulated carbon precursors were pyrolyzed at 600 C, and the resultant materials were observed to be composed of disordered carbon arrays. 

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