Recent Progress in a Membrane-Based Technique for Propylene/Propane Separation

Abstract

The similar physico-chemical properties of propylene and propane molecules have made the separation process of propylene/propane challenging. Membrane separation techniques show substantial prospects in propylene/propane separation due to their low energy consumption and investment costs, and they have been proposed to replace or to be combined with the conventional cryogenic distillation process. Over the past decade, organosilica membranes have attracted considerable attention due to their significant features, such as their good molecular sieving properties and high hydrothermal stability. In the present review, holistic insight is provided to summarize the recent progress in propylene/propane separation using polymeric, inorganic, and hybrid membranes, and a particular inspection of organosilica membranes is conducted. The importance of the pore subnano-environment of organosilica membranes is highlighted, and future directions and perspectives for propylene/propane separation are also provided.

Keywords: affinity control; hybrid membrane; inorganic membrane; organosilica membrane; polymeric membrane; pore size control; propylene/propane separation.

Figure 1

(a) Overview of the various membrane materials for C₃H₆/C₃H₈ separation. (b) General permeation mechanisms for C₃H₆/C₃H₈ separation through membranes.

Figure 2

Trade-off of C₃H₆/C₃H₈ separation performance of pristine and metal-modified polymer of intrinsic microporosity (PIM) membranes [22].

Figure 3

(a) Structure of pyrolytic carbon material [51]. (b) Schematic image of the “slit-like” structure and (c) the bimodal pore size distribution [49]. (d) Hypothetical semi-quantitative ultramicropore size distribution of CMS membrane [31].

Figure 4

Typical field-emission scanning electron microscopy (FE-SEM) images of (a,b) Na-X and (c,d) Ag-X membrane ion exchanged with 10 mM AgNO₃ solution [56]. (e) Schematic illustration of the relationship between the adsorption selectivity and permeation selectivity of the Ag-exchanged zeolite membrane [57].

Figure 5

(a) Structure of porous graphene models. (b) Structure of the modified pore-13 [61].

Figure 6

(a) Schematic illustration of membrane synthesis using the counter-diffusion method [17]. (b) Schematic image of the heterogeneous nucleation and crystal growth on the 3-(2-imidazolin-1-yl)propyltriethoxysilane (IPTES)-modified surface [73]. (c) Illustration of the experimental apparatus of atomic layer deposition (ALD) for the fabrication of ZIF-8 membranes [69].

Figure 7

(a) Schematic illustration of the PDMS-coated ZIF-8 membrane [74]. (b) Separation properties of C₃H₆/C₃H₈ as a function of the transmembrane pressure [74]. Permeation conditions for C₃H₆/C₃H₈ separation (c) with sweep gas, (d) without sweep gas, and (e) with vacuum pump [75].

Figure 8

(a) Schematic illustration of the membrane synthesis via heteroepitaxial growth [76]. (b) Schematic illustration of the design of bimetallic Zn_(100-x)Co_xZIF membranes [68].

Figure 9

Schematic image of the in situ formation of metal organic framework (MOF)-doped MMMs [77].

Figure 10

(a) Schematic illustration of the detailed fabrication process of organosilica membranes. (b) Sol–gel process for the formation of a separation layer including polymeric and colloidal sol routes [81]. (c) One-sided chemical vapor deposition (CVD) and counter-diffusion CVD methods for the deposition of an organosilica layer [81].

Figure 11

Schematic diagram for fabrication of organosilica/polymeric support membrane via the “flow-induced deposition” approach [111].

Figure 12

(a) Schematic illustration of amorphous network structures derived from tetraethoxysilane (TEOS), bis(triethoxysilyl)methane (BTESM), and bis(triethoxysilyl)ethane (BTESE) [89]. (b) Bonding structure model of BTESE-, BTESEthy-, and BTESA-derived networks [93].

Figure 13

(a) Schematic image of the possible structures of Pd–Nb–BTESE networks for H₂/CO₂ separation [114]. (b) ²⁹Si and (c) ²⁷Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra for BTESM and Al-BTESM gel powders [100].

Figure 14

Relationships between pore size and single gas permeation properties: (a) C₃H₆ permeance and (b) C₃H₆/C₃H₈ permeance ratio at 200 °C for a variety of (composite) organosilica membranes. (c) Possible schematic image for C₃H₆/C₃H₈ separation utilizing organosilica membranes with different pore sizes [101].

Figure 15

(a) Model reactions cyclic trimers and optimized geometries of propylene complexes. (b) Plausible C₃H₆/C₃H₈ separation mechanisms through BTESA membranes with different chemical properties [45].

Figure 16

C₃H₆ and C₃H₈ adsorption isotherms at 25 °C for the triethoxyfluorosilane (TEFS) powders calcined at 350 °C before/after steam treatment (closed symbols: before steam treatment, open symbols: after steam treatment) [118].

Figure 17

Trade–off of C₃H₆/C₃H₈ for polyimide [20,46], MMMs [27,120], facilitated transport membranes [22,23], CMS [31,33,52,53], ZIF–8 [17,65,66,67,68,69,72,73,74,75,76], and organosilica [45,89,93,97,98,99,101,118] membranes.