*Polymer-Based Membranes for C3+ Hydrocarbon Removal from Natural Gas DOI: http://dx.doi.org/10.5772/intechopen.103903*



*Polymer-Based Membranes for C3+ Hydrocarbon Removal from Natural Gas DOI: http://dx.doi.org/10.5772/intechopen.103903*

> **Table 7.**

*C3+hydrocarbon properties in high free volume glassy polymeric membranes.*

#### **Figure 10.**

*Chemical structures of selected branched polyacetylene-based polymers (i.e. PTMSP, PMP, PTMGP, PTMSPA) and linear poly(2-alkylacetylenes) (i.e. i.e., poly(2-hexyne), poly(2-octyne), poly(2-nonyne), poly (2-decyne), and poly-(2-undecyne)).*

#### **Figure 11.**

*Mixed gas C4H10 permeability and C4H10/CH4 selectivity for selected branched polyacetylene (i.e. PTMSP, PMP, PTMGP and PTMSDPA) and linear poly(2-alkylacetylenes) (i.e. poly(2-hexyne), poly(2-octyne), poly (2-nonyne), poly(2-decyne), and poly-(2-undecyne)) membranes.*

### *5.1.2 PIM-1*

PIMs are spirobisindane-based rigid, glassy polymers with high fractional free volume (FFV = 0.26), excellent chemical stability and good solvent resistance. PIM-1 is the most studied PIMs for gas separation, and it shows high CO2 permeability with moderate CO2/CH4 selectivity, which is exceeding the upper bounds [97]. A new perspective on the role of PIMs and its functionalized ladder PIMs (e.g. PIMpolyimide copolymers) in key energy-intensive membrane-based gas separations, including O2/N2, H2/N2, H2/CH4, CO2/CH4, H2S/CH4, C2H4/C2H6, and C3H6/C3H8, was described in detail in a recent review paper by Wang et al. [98]. Similar as PTMSP, PIM-1 is also particularly permeable to hydrocarbon vapors (**Table 7**). Thomas et al*.* [16, 17] investigated the pure- and mixed-gas permeation properties of PIM-1, it exhibits C4H10/CH4 and C4H10/H2 mixed gas selectivities up to 25 and 27, respectively, under a mixture of 2 vol% C4H10 in CH4. Since PIM-1 has better solvent resistance than PTMSP, it could find applications as an advanced membrane material for the separation of organic vapor/permanent gas mixtures [17], and further membrane performance evaluation under industrially relevant feed streams and testing conditions will be the topic of future studies in the research groups.

1.Polynorbornene-based polymers
