Alkaline KMnO4 solution pretreat hydrochar to prepare high ultra-micropore volume carbon for CH4 enrichment from low-concentration coalbed methane

Rational design of the carbon adsorbent for recycling CH4 from low-concentration coalbed methane is impressive for sustainable development. However, facile approaches to prepare carbon materials with uniform pore size distribution and abundant ultra-micropore volume are still challenging. Herein, we designed a facile and effective strategy to produce ultra-microporous carbon material, which uses alkaline KMnO4 solution to pretreat carbon precursor, then activate at high temperature. The prepared carbon material has a microspherical morphology, uniform pore size distribution of mainly 0.4-0.7 nm and abundant ultra-micropore volume of 0.50 cm(3)/g. The excellent CH 4 adsorption capacity was demonstrated by the adsorption data with 3.38 mmol/g, 1.87 mmol/g at 273 K, 298 K and 101.3 kPa. The IAST simulation suggested the CH4/N-2 selectivity of sample AC-KP for a binary mixture of CH4 and N-2 was 6.5 at 298 K and 101.3 kPa. Meanwhile, the adsorption capacity of the binary mixture of CH4 and N-2 was also calculated. The fixed bed cycling breakthrough experiment showed good recycling performance with the regeneration rate maintained at about 95% in eight cycles. This work provides a promising avenue to carbon materials with abundant ultra-microporosity towards the superior performance of CH4 recycling from low-concentration coalbed methane.