Synthesis of a Carbon Molecular Sieve from Broom Corn Stalk via Carbon Deposition of Methane for the Selective Separation of a CO2/CH4 Mixture

Abstract

AbstractA carbon molecular sieve (CMS) was prepared from broom corn stalk as a low cost precursor by carbon vapor deposition of methane. The base activated carbon (AC) was produced from the broom corn stalk using ZnCl2 as the chemical activating agent. To produce the CMS, the pore structure of the AC prepared at the optimized condition was modified by chemical vapor deposition of methane. The CO2 and CH4 adsorption capacity of the developed CMS and the base AC was experimentally measured using the volumetric technique in the temperature range of 288–308 K and a pressure range of 1–40 bar. Experimental data revealed a better CO2/CH4 separation selectivity for the CMS compared to the AC. The results demonstrated the successful deposition of carbon on the AC during chemical vapor deposition of methane, where the Brunauer–Emmett–Teller surface area decreased from 1121 to 815 m2 g−1 and the micropores showed a reduced volume from 0.57 to 0.30 cm3 g−1. The enhancement of ideal selectivity from 3.5 for the base AC to 26.0 for the CMS was attributed to the molecular sieving effect due to the reduction of the average pore diameter from 2.02 to 1.47 nm. The evaluation of the isosteric heat of adsorption demonstrated the exothermic nature of the gas adsorption onto the synthesized CMS.