In the last few decades, membrane technology has been a great attention for gas separation technology especially for natural gas sweetening. The intrinsic character of membranes makes them fit for process escalation, and this versatility could be the significant factor to induce membrane technology in most gas separation areas. Membranes were synthesized with various materials which depended on the applications. The fabrication of polymeric membrane was one of the fastest growing fields of membrane technology. However, polymeric membranes could not meet the separation performances required especially in high operating pressure due to deficiencies problem. The chemistry and structure of support materials like inorganic membranes were also one of the focus areas when inorganic membranes showed some positive results towards gas separation. However, the materials are somewhat lacking to meet the separation performance requirement. Mixed matrix membrane (MMM) which is comprising polymeric and inorganic membranes presents an interesting approach for enhancing the separation performance. Nevertheless, MMM is yet to be commercialized as the material combinations are still in the research stage. This paper highlights the potential promising areas of research in gas separation by taking into account the material selections and the addition of a third component for conventional MMM. -------------------------------------------------
Natural gas can be considered as the largest fuel source required after the oil and coal . Nowadays, the consumption of natural gas is not only limited to the industry, but natural gas is also extensively consumed by the power generation and transportation sector . These phenomena supported the idea of going towards sustainability and green technology as the natural gas is claimed to generate less-toxic gases like carbon dioxide (CO2) and nitrogen oxides () upon combustion as shown in Table 1 .
Table 1: Fossil fuel emission levels (pounds per billion Btu of energy input). However, pure natural gas from the wellhead cannot directly be used as it contains undesirable impurities such as carbon dioxide (CO2) and hydrogen sulphide (H2S) . All of these unwanted substances must be removed as these toxic gases could corrode the pipeline since CO2 is highly acidic in the presence of water. Furthermore, the existence of CO2 may waste the pipeline capacity and reduce the energy content of natural gas which eventually lowers the calorific value of natural gas . Conventionally, natural gas treatment was predominated with some methods such as absorption, adsorption, and cryogenic distillation. But these methods require high treatment cost due to regeneration process, large equipments, and broad area for the big equipments . With the advantages of lower capital cost, easy operation process, and high CO2 removal percentage, membrane technology offers the best treatment for natural gas . Natural gas is expected to contain less than 2 vol% or less than 2 ppm of CO2 after the natural gas treatment in order to meet the pipeline and commercial specification . This specification is made to secure the lifetime of the pipeline and to avoid an excessive budget for pipeline replacement. Membrane technology has received significant attention from various sectors especially industries and academics in their research as it gives the most relevant impact in reducing the environmental problem and costs. Membrane is defined as a thin layer, which separates two phases and restricts transport of various chemicals in a selective manner . Membrane restricts the penetration of some molecules that have bigger kinetic diameter. The commercial value of membrane is determined by the membrane’s transport properties which are permeability and selectivity. Major gap of the existing technologies is limited to low CO2 loading (<15 mol%)....