Theoretical Investigation On CO₂ And H₂ Adsorption And Separation In The Modified Carbonaceous Porous Materials

With the rapid increase of population and energy consumption,the amount of CO₂gradually increases in the atmosphere,which leads to global climate warming,and forms greenhouse effect.The main sources of CO₂ in the atmosphere are automobile exhaust and flue gases.Carbon capture and storage technology has been regarded as the promising strategy to alleviate excessive emissions of CO₂ into the atmosphere.In order to reduce further greenhouse gas emissions,using renewable and clean energy could solve this problem.Hydrogen energy has received widespread concerns due to its high calorific value,pollution-free and renewability.There are many impurities in the production process of H₂.Membrane separation technology has been widely used in gas separation because of its high energy efficiency,easy operation,etc..The core issue is exploring the adsorbent and membrane material with high adsorption and separation capacity.Carbonaceous porous materials exhibit remarkable advantages because of their lightweight property,easy regeneration,low-cost preparation.Chemical functionalization is a significant method to improve adsorption and separation capacity of carbonaceous porous materials.In this thesis,density functional theory and grand canonical Monte Carlo molecular simulation are performed to study CO₂ and H₂ adsorption and separation in the modified carbonaceous porous materialsFirstly,adsorption and seperation of CO₂ over N₂ in Li-modified nanoporous carbons?NPCs?with 1,2,4 physical and 2,4,6 chemical Li dopants have been investigated.Li doping lead that surface area and porosity increase 7%and 21%,respectively.The saturated adsorption capacity follows the order:Chem₆Li>Chem₄Li>Phys₂Li>Chem₂Li>Phys₄Li>Phys₁Li>NPC in Li-modified NPCs.Chem₆Li exhibits the best selectivity of CO₂ over N₂?²00?.Then,N atoms are adopted to dop the multilayer graphene sheets?N-MGNs?for CO₂capture and separation CO₂ from CO₂/N₂ mixtures.The results show N doping improve effectively CO₂ and N₂ adsorption and separation capacity,and the lay distance has effect on adsorption and separation capacity.The isosteric heats and relative concentration profiles show at low pressure,the N-MGNs with layer distance of 6.8?has highest adsorption and separation capacity,while at high pressure,the N-MGNs with layer distance of 17.0?has highest adsorption and separation capacity.Finally,Porous graphene?PG?and nitrogen-substituted PG monolayers of 3N-PG and 6N-PG are designed as effective membranes for the separation of H₂ over Ne,Ar,N₂,CO,and CH₄.Results showed that the energy barriers H₂ passing through PG-based membranes are 0.60,0.49,and 0.18 eV.3N-PG and 6N-PG present excellent H₂ selectivities,and the selectivities of H₂over Ne,Ar,N₂,CO and CH₄ are higher than 10⁵?10³¹?10²⁴?10²¹?10³².6N-PG membrane exerted unexceptionable H₂ permeances(0.15 mol m^-2 s^-1 Pa^-1).This thesis highlight the effects of functionalization on the adsorption and separation of CO₂ and H₂ in carbonaceous porous materials,and provided an effective strategy for designing and screening adsorbent and separating membrane materials.