Preparation Of Graphene Based Composite Porous Material And Gas Adsorption Separation Properties

The shortage of natural gas currently seriously threatens national gas anu energy secunLy.To this end,the state vigorously develops unconventional natural gas dominated by coal-bed methane.On the other hand,the increasing greenhouse effect has made carbon capture technology a hot topic.How to achieve the C02 capture and the concentration and utilization of CH4 in coalbed methane has become a major challenge in the field of gas separation.Therefore,a new porous adsorbent with high adsorption capacity and high separation coefficient was developed for the effective separation of CH4,CO2 and N2 gases.It is of great significance for improving China's energy structure,reducing waste of resources,alleviating environmental pollution and developing low-carbon economy.A new grapheme based porous material(GPM)was prepared by KOH chemical activation process using graphite powder as precursor.The optimum activation conditions were determined by single factor experiments:the activation agent concentration was 9 M and the activation temperature was 1073 K.The prepared grapheme based porous(GPM-9)has a specific surface area of 2465.76 m2/g,a total pore volume of 1.53 cm3/g and an average pore size of 3.20 nm.Under the same pressure,the adsorption capacity of GPM decreases with the increase of temperature.After fitting the adsorption data model,it is found that the Freundlich model is more suitable for describing the adsorption behavior of CO2 and N2 on GPM,and the Langmuir model is more suitable for describing the adsorption behavior of CH4 on GPM.The CH4 saturated adsorption capacity of GPM was 11.45 mmol/g and CO2 saturated adsorption capacity was 33.14 mmol/g.At 298 K and 303 K,the separation coefficients of GPM to CH4/N2 were 2.86 and 2.77 respectively,and the separation coefficients for CO2/N2 were 5.53 and 5.16,respectively.Graphene based composite porous carbon(GCPC)was prepared by using biomass activated carbon(CAC)and coal based activated carbon(MAC)as raw materials to compounded with graphene oxide(GO)respectively.By single factor experiments,it is found that when the ratio of GO to CAC is 1:50 and the ratio of KOH to carbon is 4:1,the composite porous carbon material(CAC-50)with a surface area of 3140.61 m2/g can be prepared,and the CH4/N2 separation coefficient is 2.83.The optimum ratio of GO and MAC is 1:200 and the optimum KOH to carbon ratio is 5:1.The specific surface area of composite porous carbon material(MAC-200)is 2695.22 m2/g,and the separation coefficient of CH4/N2 is 2.72.The penetration time of CAC-50 and MAC-200 was 200%and 70.8%less than that of CAC and MAC respectively.The functional groups of porous carbons were modified by three methods:organic reagent impregnation,low temperature plasma modification and graphene oxide GO assisted modification.The results showed that the organic functional groups were introduced on the surface of the composite porous carbon after the modification of the organic reagents,and the type and strength of the oxygen containing functional groups and the nitrogen functional groups on the surface of the composite porous carbon materials were obviously changed by the low temperature plasma irradiation.Organic reagents play a role in regulating pore structure of porous carbon materials,and the separation coefficient of porous carbon is increased after the modification of organic reagents.The separation coefficient of porous carbon(MAC200-C24)modified by positive twenty-four alkane impregnation is up to 3.06.The separation coefficient of porous carbon(MAC200-DN2)modified by low temperature plasma irradiation under N2 atmosphere is superior to that of irradiated porous carbons(MAC200-DO2)under O2 atmosphere.This paper provides new ideas for the efficient utilization of graphite resources and low concentration CBM,and puts forward some new methods for the efficient preparation of porous carbon and the change of pore channel and surface modification.It also provides basic data for the adsorption and separation of carbon materials.