Over the last decades, different polymers have been used as continuous phase for preparing selective membranes for gas separation. Today, some of these materials have been consolidated commercially; however, the necessity to improve the performance (in terms of permeability/selectivity) of polymeric membranes above Robeson’s upper bound has been conducted by blending polymers, use of additives, implementation new methods, development of new materials, coating films, development of mixed matrix membranes, and so on. One of the most recent approaches is the use of polymers such as polyimides, i.e., Matrimid® 5218, which has demonstrated, to provide remarkable gas separation performance using the attempts aforementioned. The aim of this work is to present the current state-of-the-art of the use of Matrimid® 5218 in preparation of membrane for gas separation. The progress in this field is summarized and discussed chronologically in two periods, decade (from 1998 to 2008) and current (from 2009 up to now) frameworks. This contribution leads to take a complete and compelling overview of the state-of-the-art based on Matrimid. Furthermore, the main approaches, aim of study, gas separation evaluated, main techniques used for membrane characterization, main supplier of the polymer, main secondary materials for blending, fillers incorporated into the matrix, and remark of the study are summarized in detail. Finally, it denotes the prospects and future trends on use of Matrimid® 5218 for membrane applications.

Natural gas is one of the most highly used resources, not only as a fuel but also as a raw material for many industrial processes. In addition, it is an environmental friendly fuel due to its lower greenhouse gas emission than that of coal or oil. However, it is a nonrenewable energy source and the quality of the available resources is expected to deplete continuously. In this scenario, membrane technologies can play an important role in the purification of the reduced and contaminated resources, competing with the current technologies owing to their simpler adaptability to different feed compositions, lower energy consumption and investment costs. In this review, the current state of the natural gas sources, including nonconventional resources (tight/shale gas and biogas), is explored, along with the current market status of the conventional natural gas. A comparison between the conventional purification technologies and membrane processes is provided, together with the currently available commercial membranes as well as new materials. Furthermore, the latest materials in research stage are reviewed, pointing out their limitations to the current membranes technologies. Finally, future research trends to overcome the current membrane technology limitations are proposed, and the conclusions are addressed.