Adsorption Separation Of Ethylene/Propylene In Refinery Dry Gas

Ethylene is an important chemical raw material,the world's ethylene production is one of the standards to measure a national petrochemical production level.A lot of ethylene is often contained in refinery dry gas,however refinery dry gas is mostly ignited or used as fuel gas before in the comprehensive utilization of technology before the immature,refinery dry gas mostly ignited or as fuel gas before the comprehensive utilization technology mature.Using refinery dry gas reasonable not only can improve resource utilization,but also enable enterprises to reduce production costs and increase efficiency.One of the important uses of refinery dry gas is using the dilute ethylene to preparaing ethylbenzene.However,the propylene in the dry gas will interfere with the progress of the reaction,resulting in by-products,generally require propylene in dry gas content of less than 0.15%.Therefore,the effective removal of propylene in ethylene,purification of raw materials gas,is an important step in the use of refinery gas.In this paper,the adsorption separation process of ethylene and propylene was studied by adsorption separation method,which can provide data reference and theoretical basis for industrial production process.First of all,12 different types of adsorbents were selected.They are activated carbon AC-1 and AC-2,ordered mesoporous materials CMK-3 and SBA-15,zeolite5A,13X and Y,the metal organic framework materials?MOFs?MIL-101,Cu-BTC and ZIF-8,silica gel SG-1 and SG-2.Among them,CMK-3,SBA-15 and SG-2 are mesoporous adsorbents,and the others are microporous adsorbents.The adsorption isotherms of C₂H₄ and C₃H₆ on 12 kinds of adsorbents were measured by static volumetric method at 293 K and the pressure range was 0-0.8 MPa.The results showed that the pore size of adsorbent has a great influence on the adsorption performance.Due to the small pore size of 5A zeolite,the adsorption of C₃H₆ is limited and the adsorption of C₂H₄ is preferentially adsorbed.AC-2,Y and 13X adsorption capacity of C₂H₄ and C₃H₆ are basically the same,other adsorbents are preferentially adsorbed C₃H₆.The ideal solution?IAST?theory was used to calculate the adsorption and separation performance of the adsorbent to C₂H₄/C₃H₆,and the separation factor of AC-1 was 8.7.Five representative microporous adsorbents were selected to investigate their adsorption properties at different temperatures,the adsorption isotherm was fitted by Langmuir equation,L-F equation and Langmuir-Toth?L-T?equation,respectively.The results showed that the three parameter equation L-F and L-T equation fit well.According to the adsorption isotherms at different temperatures,equal adsorption heat was calculated.With the increase of coverage,the adsorption heat of C₂H₄ on 5A,SG-1 and AC-1 decreased and then stabilized,and the adsorption heat on MIL-101and ZIF-8 stabilized at about 15 kJ/mol.With the increase of coverage,the adsorption heat of C₂H₄ on 5A,SG-1 and AC-1 decreased and then stabilized,and the adsorption heat on MIL-101 and ZIF-8 stabilized at about 15 kJ/mol,the adsorption heat of C3H6 on MIL-101,ZIF-8,AC-1 and 5A increased with the increase of coverage rate,while SG-1 decreased slowly.The adsorbent activated carbon AC-1 with the highest separation factor was selected for dynamic penetration experiment and the permeation curves under different conditions were measured for further study of the C₂H₄ and C₃H₆adsorption separation performance.The experimental temperature were 273 K,293 K and 313 K,the total pressure were 0.1 MPa,0.3 MPa and 0.5 MPa.The adsorption capacity and the separation factor were calculated according to the penetration curve.The adsorption of both gases decreased with increasing temperature and increased with increasing pressure.The separation factor increased slightly with the increase of pressure,which was consistent with the predicted results of IAST theory,and the effect of temperature on the separation factor was not significant.