Study On The Adsorption Equilibrium Of C1-C4in Natural Gas

Hydrocarbons from natural gas can provide a large number of resources forchemical products. The adsorption separation of the hydrocarbons from natural gashas been reported rarely. The composition of natural gas produced from one gas fieldis different from those from other fields. So adsorption data for different compositionsof natural gas at certain pressure and temperature is required for industrial design. It isknown that the collection of multicomponent adsorption data is very tedious andtime-consuming. As a result, adsorption isotherms of single component is often usedto predict multicomponent adsorption equilibrium with a suitable model.The adsorption isotherms of pure methane, ethane, propane and butane on fourkinds of adsorbents were detected respectively by a volumetric method at thetemperature of283、293、303and313K. For methane, the adsorption pressure is0~3.0MPa. For ethane and propane, it is0~0.3MPa and for butane, it is0~0.08MPa.The isotherms are fitted by the Langmuir equation, Langmuir-Freundlich equation(L-F) and the vacancy solution theory (VSMT). It is showed that The L-F equationand the vacancy solution theory are better than the Langmuir equation.The adsorption equilibrium of gas mixture (CH4-C2H6-C3H8-C4H10) was collectedwith a trapping method at the temperature of303K, and up to pressure3.0MPa. Thenthe adsorption separation coefficients of CH4/C2H6、C2H6/C3H8and C3H8/C4H10werecalculated respectively. The results show that the adsorption separation coefficient isdecreased gradually with the increase of adsorption pressure decreases, and when thepressure is greater than1.0MPa, it comes to a platform. The adsorbents by adsorptionseparation coefficient of CH4/C2H6in descending order are: Jx-104>CMK-3>HY-Hsilica gel>Kit-6. However, for the adsorption separation coefficient of C2H6/C3H8andC3H8/C4H10, they are: Kit-6> HY-H silica gel>CMK-3>Jx-104. In addition, theadsorption equilibrium of gas mixture (CH4-C2H6-C3H8-C4H10) was measured atdifferent temperature. It was shown that the temperature has little effect on theseparation coefficient.