**6. Conclusions and outlook**

Membrane-based separations have emerged as an economically favorable alternative due to its small footprint, reduced capital, and energetic cost. Membranes for C3+ hydrocarbon recovery from natural gas have been practiced in the chemical and petrochemical industries, the improved C3+ hydrocarbon separation and removal process from natural gas will be beneficial of these industries.

This chapter summarizes C3+ hydrocarbon separation and removal from natural gas using polymeric membrane-based technologies. More specifically, it addresses the removal of C3H8 and C4H10 from CH4 by perspective polymer architectures based on reverse-selective glassy polymers with stiff chains and rubbery polymers with flexible chains. At present PDMS, POMS and poly(ether-*b*-amide) rubbery polymer membranes are used by industries in the field for C3+/CH4 separation. However, improved mixed gas selectivity of C3+/C1 with high flux will have a positive impact of the economics of the C3+ hydrocarbon recovery from natural gas. In case of reverse selective glassy polymers, membrane separation performance can be improved by introducing new groups or additives into membrane matrix, however, the loss of permeances due to physical aging restrains their applications in industry. This chapter also accounts the effect of the chemical structure of rubbery polymers on their permeation properties for C3+ hydrocarbons recovery from natural gas. Modified siloxane rubbery polymers-based membranes may be seen in future in the field for enhanced C3+ hydrocarbons recovery from natural gas since these membrane materials display improved mixed gas C3+/CH4 selectivity than
