Synthesis of micro/mesoporous carbon adsorbents by in-situ fast pyrolysis of reed for recovering gasoline vapor

Abstract In this research, pyrolysis of reed, as a carbon source, was carried out by fast and slow processes and the products were compared. Also, activated and N-doped porous carbons with different porosity properties were synthesized by one-step in-situ fast-pyrolysis process for gasoline vapor adsorption. Zinc chloride and phosphoric acid as the activating agents; and urea, mono- and di-ammonium phosphates as the N-doping materials were utilized in this process. Morphologies and physical properties of the carbon products were characterized by FE-SEM, EDXS, CHN elemental analyzer, and FT-IR spectroscopy. The porosity properties of the samples were analyzed by BET surface area analysis method. Adsorption capacities of the synthesized adsorbents were assessed for gasoline vapor by gravimetric method. The study revealed that carbon nanofibers/carbon hybrid was formed by free-catalyst fast pyrolysis of the reed. The suggested mechanisms for non-metal carbon nanofiber growth were discussed. The BET results showed that ZnCl2-activated carbons and the in-situ N-doped products using ammonium phosphate possessed micro/mesoporous structures and displayed composite type I/IV isotherms. However, H3PO4-activated carbons had microporous structures and presented type I isotherms. The post-treatment N-doped products had mesoporous structures and showed type IV isotherms. ZnCl2 and H3PO4 in-situ activated carbons, and (NH4) H2PO4 in-situ N-doped product had high surface areas of 1544.5, 1098 and 497.45 m2/g with 1.6, 0.52 and 0.30 cm3/g pore volumes, respectively. From FT-IR results can be concluded that the oxygen-containing functional groups of ZnCl2-activated products significantly were decreased compared to that of H3PO4-activated. Also the FT-IR analysis confirmed the presences of the nitrogen containing functional groups on the N-doped products. The finding showed that the micro/mesoporous structures considerably improved gasoline adsorption capacity. As a result, ZnCl2 in-situ activated carbon had the highest adsorption capacity of 1019 mg/gadsorbent which was approximately 10 times greater than the commercially activated carbon.