Synthesis of novel particle rice-based carbon materials and its excellent CH4/N2 adsorption selectivity for methane enrichment from Low-rank natural gas

Abstract Developing novel particle carbon adsorbents with excellent separation performance for recovering low concentration CH4 from coal mine gas remains great challenging. In this work, a novel and effective method was proposed for preparing particle carbon adsorbents with excellent separation performance of CH4/N2 mixtures. Rice was selected as carbon source to prepare carbon precursors in particle form by carbonization, followed by CO2 activation yielding particle rice-based carbon materials (PRCs) with narrow micropore distribution. Noteworthy, neither binding agent nor KOH was used in preparation process of particle PRCs. The resulting particle PRCs exhibited specific BET surface area of 776 m2/g. Its CH4 uptake and CH4/N2 adsorption selectivity were up to 1.12 mmol/g and 5.7 at 298 K and 100 kPa, which was superior to most of the reported powdery carbon materials and MOFs. Besides, computational simulation was applied to reveal the different contributions of the surface hydroxyl/carboxyl/aldehyde groups of the PRCs to the adsorption selectivity of CH4/N2. Calculation showed that the surface carboxyl groups played an important role in enhancement of the adsorption selectivity of PRCs toward CH4/N2 mixture. Fixed-bed experiments approved that CH4/N2 mixtures can be greatly separated at ambient condition. The particle PRCs are great potential materials for recovering low concentration CH4 from coal mine. This facile and effective method proposed in this work is great attractive in low cost preparation of particle porous carbon materials without binding agent and KOH.