OS6B-7:SEPARATION OF ETHYLENE FROM ETHYLENE/METHANE MIXTURES IN W/O EMULSION

Huang LIU, Bo WANG, Jin WANG, Guangjin CHEN, Changyu SUN, Xiaoxin ZHANG, Xinyang ZENG
State Key Laboratory of Heavy Oil Processing, China University of Petroleum, CHINA

    C2s are the main products of oxidative coupling of methane in the process for converting natural gas into a more useful chemical feedstock, thus they certainly need to be separated out from the unreacted methane. In the present work, a so-called absorption-hydration hybrid method for separation C2H4 from C2H4/CH4 gas mixtures by using water-oil (W/O) emulsion system under hydrate formation conditions was adopted. C2H4 is hoped to be first selectively absorbed by the diesel and then selectively formation hydrate due to its relative higher solubility in diesel and lower hydrate formation pressure than that of CH4. Span 20 with the concentration of 1.0 wt% to water was added to disperse water or hydrate in diesel to form flowable emulsion or hydrate slurry. Our experimental results show, contributed to the co-exist of diesel and anti-agglomerant (Span 20), the activity of droplets in the W/O emulsion is lower than that of pure water, made C2H4/CH4 hydrate formation pressure in the emulsion system is some higher than that in pure water. For the separation of C2H4/CH4 (31/69 mol%) mixture, the concentration of C2H4 in the gas phase could be reduced from 31 to as low as 14 mol% at 274.15 K and equilibrium pressure 1.83 MPa, with the mole fraction of C2H4 in the diesel-hydrate slurry reached to 48 mol% (on dry basis) and 75 mol% C2H4 could be recovered from it. Under this condition, the separation factor of C2H4 over CH4 is about 5.5. The influence of temperature, pressure, and water cuts upon the separation ability and hydrate formation rate were investigated in detail. Results show that suitable operation conditions are temperature 274.15 K or so, initial pressure 3 ~ 5 MPa, and water cut 30 vol%.