Smart Membrane- A Technology of CO2 Removal from Natural Gas
Authors: Kittichai C. , Tanaporn P. 
Published: February 2024

Membrane separation technology is widely employed in offshore applications due to its compact design and versatility in handling varying CO2 contents. Currently, polymeric CO2 removal membranes serve as essential components in offshore acid gas removal units, extracting CO2 from natural gas to meet sales gas specification. However, ensuring their longevity and sustainability necessitates rigorous upstream pre-treatment. Despite facing significant operational challenges, such as a high replacement rate of costly membrane elements and hydrocarbon loss, a novel membrane type with a superior overall life cycle cost is currently in development.

PTTEP and Chulalongkorn University (CU) have collaborated in researching and developing a novel composite CO2 removal membrane. This innovative membrane boasts superior material and an optimized fabrication process, aiming to overcome the trade-off behavior commonly found in polymeric membranes (permeability-selectivity trade-off) and address the fragility challenges associated with the fabrication of inorganic membranes. To achieve this breakthrough, a comprehensive approach was taken. Various membrane materials were fabricated and rigorously tested under diverse offshore operating conditions. These conditions include variation in temperature, pressure, CO2 contents (both as removal target and plasticizing agent), as well as impurities such as water vapor, benzene, and toluene. The primary goal of this research is to optimize membrane performance and identify the most promising materials, fabrication process and conditions. The ultimate aim is to scaleup the production and employ this novel composite CO2 removal membrane as an alternative solution in offshore applications.

The underdeveloped composite membrane comprises a support layer made of polyetherimide (PEI) coated with a selective organic layer based, Poly (amide-b-ethylene oxide) or called Poly ether-block-amide (PEBA), complemented by various inorganic fillers. Testing conducted on this innovative membrane has yielded the following promising results: It demonstrates suitability for efficient CO2 removal from natural gas, even when the gas contains high partial pressures of CO2, reaching up to 27 barg.The membrane displays outstanding resistance to saturate water vapor content, particularly under the operating conditions pertinent to offshore applications.Applying a crosslinking technique has resulted in a stable CO2/CH4 selectivity, even in the presence of higher concentrations of toluene and benzene commonly found in raw natural gas.

The latest obtained result indicates that application of the crosslinking technique holds promising potential for enhancing both the separation efficiency of the membrane and its overall material properties, suggesting opportunities for further development. Moreover, the membrane's performance suggests that stringent control parameters for pre-treatment systems could be relaxed, making it more adaptable and easier to implement in various operating conditions. In summary, the new novel composite membrane demonstrates commendable gas separation efficiency, comparable to commercial membranes. Further research and development efforts can concentrate on optimizing the design, scalability, and cost-effectiveness to fully exploit its potential for mass production and commercialization.