An initial study of the selectivity of methane over carbon dioxide and inert gases using a y-type zeolite membrane

Gaseous hydrocarbons that are prevalent under increased pressure include solute ion gases that are found in oil reservoirs. These hydrocarbon gases are usually conserved but in some cases exploration are considered uneconomical and thus they are flared. The impact of flaring on the environment cannot be over emphasised and therefore to increase the capacity for transporting a higher volume rather than flaring, an efficient separation of the gases is essential. Although the composition of natural gas varies extensively from one gas field to another, the major component of natural gas is methane with inert gases and carbon dioxide. Hence, all natural gas must undergo some treatment with about 20% of total reserves requiring extensive treatment before transportation via pipelines. There is on-going research on the use of composite mesoporous membranes to separate gaseous mixtures hence making it one of the emerging technologies that is growing fast. The question is can a zeolite membrane have a transport mechanism that will be highly selective for methane and be used for the treatment of natural gas? A methodology based on the use of dip-coated Y-type zeolite membrane was developed. Nitrogen physisorption measurements were carried out which showed the hysteresis isotherm of the membrane corresponding to type IV and V that is indicative of a mesoporous membrane. The surface area and the pore size was determined using the Barrett, Joyner, Halenda (BJH) desorption method. Single gas permeation test using a membrane reactor was carried out at the ambient temperature of 298 K and a pressure range of 0.01 to 0.1 MPa. The permeance of CH4 was in the range of 1.44 x 10-6 to 3.41 x 10 -6 mols-1m-2Pa-1 and a maximum CH4/CO2 selectivity of 2.04 at 293 K and 0.2 MPa.The results obtained have shown that it is possible to use a zeolite membrane to selectively remove carbon dioxide from methane to produce pipeline quality natural gas. There is a need for further study of the ambient conditions needed to achieve capillary condensation through the membrane as this is essential for the separation of other hydrocarbons that could be present as impurities.