Preparation Of Biomass-based Composite Activated Carbon And Its Adsorption And Separation Of CH₄/N₂

With the development of China economy and the importance of environmental protection,the demand for clean natural gas in China is increasing rapidly.As an unconventional natural gas resource,the development of coalbed methane(CBM)is beneficial to environmental protection and economic development and has great potential.Our country has 18 billion m3 pure CH4 through the mine gas emptying every year,waste of resources is enormous.Therefore,how to adsorb and separate and enrich methane from coal mine gas has become a hot topic of common concern in the world's major coal producing countries.This paper is devoted to the preparation and surface modification of the special activated carbon adsorbent for enrichment CH4 by pressure swing adsorption.The main results are as follows:1.Preparation of biomass based activated carbon with high specific surface area from Corn cob.The biomass based corncob activated carbon suitable for CH4/N2 adsorption separation and enrichment.The best preparation process was obtained by single factor analysis:Using dry corncob as raw material,raising the temperature to 450? in a tubular furnace and carbonizing for 30min at constant temperature;Activation of carbonized materials at 4:1 ratio of KOH base to carbon,activation of 1h at 850?.Under these conditions,the specific surface area of biomass based activated carbon is 1583.14m2/:,the micropore ratio is 75.4%,the separation coefficient is 3.2,and the saturated adsorption capacity of methane is 16.15 mL/g under atmospheric pressure.The disadvantage of this process is that the yield of activated carbon is low.2.The comcore-taixi coal composite activated carbon was successfully prepared and the preparation conditions were optimized.The composite activated carbon was prepared by homogeneous mixing of corncob carbonized material and Taixi coal base activated carbon at preactivated at 400? for 1h and activated at 850? for 1h.The specific surface area of the composite activated carbon is 1711.9m1/g,the micropore ratio was 56.8%,1he dynamic adsorption capacity of methane at atmospheric pressure is 12.98 mL/g.the separation coefficient was 2.68,the dynamic breakthrough time of methane is 82s.The corncob has successfully improved the activated carbon performance of Taixi coal.3.Nitrogen load modification of biomass activated carbon and composite activated carbon,to enhance the surface nonpolarity of activated carbon by nitrogen load modification,and then enhance the adsorption and separation performance of activated carbon for CH4/N2.The optimized modification conditions are as follows:mass ratio of activated carbon to dicyandiamide 8:1,hydrothermal loading,reaction at 500? for 2 h in nitrogen shielded tube furnace,Nitrogen-doped modification was carried out for the activated carbon made from dried com cob:the saturated adsorption capacity of methane is 19.95mL/g at atmospheric pressure,the separation coefficient was 2.24,and the breakthrough time was 126s.Nitrogen-doped composite activated carbon:the saturated adsorption capacity of methane is 14.56 mL/g at atmospheric pressure,the separation coefficient is 1.87,and the breakthrough time is 92s.