Pore Geometry Alternation Of Carbon Adsorbents For Hydrocarbon Separation

Due to the similar physical and chemical properties,the separation and purification of hydrocarbons is a high energy consumption separation process in the petrochemical industry.Among them,the propane/propylene separation and xylene isomer separation are also considered to be one of the seven world-changing chemical separations.As an energy-saving gas separation technology,adsorption separation has received extensive attention in the separation and purification of hydrocarbons in recent years.The key to adsorption separation lies in adsorbents.For the development of adsorbents,appropriate micropores can distinguish two molecules with similar properties,which is the key to improve the selectivity of hydrocarbon separation.Porous carbon materials have shown great application prospects in the field of adsorption separation because of their high specific surface area,controllable physical and chemical properties,low price and easy availability.At present,the focus of carbon adsorbents is mainly on the of microporous carbon.However,the molecular diffusion in the highly tortuous ultramicropores is suppressed,which is not conducive to practical use.Enlarging pore sizes to mesopores i.e.,2 nm and above could greatly increase the diffusion kinetics.To date,a plethora of hierarchical micro-and mesoporous carbon materials can be prepared,however barely any hydrocarbon separation performance can be reached.In view of the above challenges in the development of carbon adsorbents,porous carbon with wiggling mesopores was prepared,in order to provide a basis for the study of new adsorption materials.The main results are as follows:（1）Using phenolic resin as carbon source,a kind of monolithic carbon with wiggling mesopores was synthesized by disturbing micelle with boric acid and ammonia.It is characterized by a unique two-step desorption process for on a series of gas probes with different kinetic sizes,such as Ar,N₂,H₂O and toluene.The specific surface area of the representative sample is 413 m² g^-1,and the pore size distribution is concentrated in 1.5,4.2and 6.6nm.The three-dimensional structure of wiggling mesopores is reconstructed by using advanced electronic tomography technology.In addition,the adsorbent has good axial and radial compressive strength,reaching 5.5 MPa and 221 N cm^-1,respectively.The synergistically kinetic and equilibrium effects were observed and quantitatively assessed,which together ensured a remarkable propylene/propane selectivity up to 39.Moreover,the adsorbent adsorbed propylene via moderate physisorption interactions with the heat of being17 k J mol^-1 at zero loading,which allowed the material to be easily regenerated under mild conditions.（2）As a new carbon source,the diversity of phenols,aldehydes and amines gives polybenzoxazine more flexibility and wide applicability.Based on the phthalonitrile-based resins,the wiggling mesopores were successfully introduced into benzoxazine resin carbon catalyzed by ethylenediamine,hexanediamine and p-phenylenediamine.The specific surface areas of representative samples were 161,305 and 33 m² g^-1,respectively.The adsorbent shows strong antioxidant performance,and 46%of the residual mass is still after air treatment at 700℃.The application of wiggling mesopores in the separation of xylene isomers was studied systematically.The wiggling mesopores kinetically amplify the adsorptive separation of xylene isomers,and the adsorption capacity of p-Xylene is up to 2 times of that of m-Xylene at 303 K.