Preparation Of Novel Carbon-based Porous Materials And Their Separation Properties For Small Gas Molecules

In the field of petrochemical industry and environmental protection,there is an urgent need to study the separation of small hydrocarbons molecules,CO₂ capture and VOCs pollution control.In this work,several new porous carbon-based adsorbents were prepared.The effects of pore structure and surface chemistry on adsorption and separation of these gases were studied.This work belongs to the interdisciplinary fields of chemical engineering,surface science and material engineering.It is of great significance for the scientific research and practical applications.A series of novel dopamine-based porous carbon material C-PDAs were synthesized and their adsorption and separation performance toward ethylene/ethane binary mixture was examed.The as-synthesized C-PDAs exhibited preferential adsorption of ethane,with adsorption capacity up to 7.93 mmol/g at 298 K,which is among the adsorbents having the highest adsorption capacity in this field.The selectivity toward C₂H₆/C₂H₄（1:9,v/v）can reach 7.94,which is far higher than most of the adsorbents that currently reported as preferential adsorbents for ethane.DFT calculations revealed that the main reason for showing preferential adsorption of ethane was the stronger electrostatic interaction between ethane and N/O functional group sites on C-PDAs.In this thesis,MGAs carbon materials were prepared and the mechanism of separation of ethylene/ethane by synergistic enhancement of pore structure and surface group were studied.Glucosamine-based porous carbon materials（MGAs）were prepared by selecting glucosamine as carbon source.The MGAs material possessed avanced micropore structure and abundant N/O surface functional groups,the ethane adsorption capacity was up to 7.6 mmol/g at 298 K and 1 bar,and the selectivity for C₂H₆/C₂H₄（1:1,v/v）was up to 6.8.It was clarified that the synergistic effect of surface N/O functional groups and 6-10?pores was the key to improve the selectivity toward C₂H₆/C₂H₄ on MGAs material by using DFT simulation.The breakthrough experiment showed that MGAs can be used to separate ethane/ethylene mixture completely at ambient condition.In this thesis,the carbon dioxide adsorption performance on Glc-Cs in the range of 1-30bar were studied.The prepared Glc-C700-3 material showed mainly microporous structure.At ambient condition,the CO₂ adsorption capacity was up to 4.7 mmol/g,which is much higher than that of most carbon-based adsorbents.In addition,the surface area and pore volume of the prepared Glc-C800-4 material was as high as 3150 m²/g and 2.05 cm³/g,respectively.The CO₂ adsorption capacity can reach 22.4 mmol/g at 30 bar,and the selectivity toward CO₂/N₂ and CO₂/CH₄ was 20 and 4.5,respectively,which was superior to the traditional activated carbon and most of the metal-organic frameworks.Glc-Cs had excellent recycling stability,and the regeneration process can easily realize up to 99%of the performance.In this thesis,urea modified starch-based carbon materials（urea@Sta-Cs）were prepared and the CO₂ adsorption performance was studied.Urea was used as N source to modify starch-based carbon material.After modification,the amount of surface N-containing functional groups for the modified Sta-Cs were significantly increased,and the CO₂ uptake increased from 4.2 mmol/g to 4.8 mmol/g at 298 K and 1 bar.The selectivity toward CO₂/CH₄ increased from 3.7 to 4.5.The modified material not only possessed good hydrophobic property,but also had good recycling property.In this thesis,the benzene/toluene adsorption and separation performance with C-PDAs in the presence of water vapor was studied.The adsorption capacity of benzene and toluene on C-PDAs at room temperature were up to 19.1 and 15.8 mmol/g,respectively,which is one of the best materials reported in this area so far.C-PDAs exhibited good hydrophobic property,so it still exhibited high separation coefficient of C₆H₆/C₇H₈/H₂O（g）in the presence of water vapor.The results calculated by using the adsorption heat difference（DIH）equation in this paper showed that the selectivities of C-PDAs for C₆H₆/H₂O（g）and C₇H₈/H₂O（g）were up to 99 and 13.6,respectively.All these properties made C-PDAs a potential material for purifying VOCs pollution.