Hydrocarbon separations by glassy polymer membranes

Abstract

Polymers are unarguably the most broadly used membrane materials for molecular separations and beyond. Motivated by the commercial success of membrane‐based desalination and permanent gas separations, glassy polymer membranes are increasingly being studied for hydrocarbon separations. They represent a class of challenging yet economically impactful bulk separations extensively practiced in the refining and petrochemical industry. This review discusses recent developments in membrane‐based hydrocarbon separations using glassy polymer membranes relying on the sorption‐diffusion mechanism. Hydrocarbon separations by both diffusion‐selective and sorption‐selective glassy polymer membranes are considered. Opinions on the likelihoods of large‐scale implementation are provided for selected hydrocarbon pairs. Finally, a discussion of the challenges and outlook of glassy polymer membrane‐based hydrocarbon separations is presented.

Membranes for olefin–paraffin separation: An industrial perspective

“…Rubbery polymers can plasticize very easily in the presence of cracked gases compared to glassy polymer membranes because of their framework flexibility. Glassy polymers such as cellulose acetate, poly(phenylene oxide), matrimid, polysulfone, ethylcellulose, and 6FDA-based copolymers showed improvement in hydrocarbon separation performance while displaying improved plasticization resistance (20). Porous polymers, such as polymers of intrinsic microporosity (PIM) and TR polymer membranes, surpassed the Robeson upper bound for most gas pairs (21).…”

Mixed-Gas Selectivity Based on Pure Gas Permeation Measurements: An Approximate Model

“…Diffusivity selectivity glassy polymers (polyimides, microporous polymers), which are used to separate olefins and paraffins C 2+ , have almost no sorption selectivity (α S ∼ 1), and the ideal selectivity values are α 12 ∼ α D = 2 − 30 [8,30]. If one accepts α 12 = α D = 10 and S 2 = 10 cm 3 (STP)/(cm 3 •atm) (as the average solubility of propane in aromatic polyimides) for a rough estimate, then from Equation (50) one obtains that the Peclét numbers vary from 0.2 to 1.9.…”

“…If one accepts α 12 = α D = 10 and S 2 = 10 cm 3 (STP)/(cm 3 •atm) (as the average solubility of propane in aromatic polyimides) for a rough estimate, then from Equation (50) one obtains that the Peclét numbers vary from 0.2 to 1.9. For solubility selectivity glassy polymers (polyacetylenes, polynorbornenes, PIM-1) used for C 2+ /methane separations, the diffusion selectivity is less than 1, and the sorption selectivity is in a wide range from 5 to ~10 3 [8,31]. For typical values α 12 = 10, α D = 0.2 and S 2 = 4 cm 3 (STP)/(cm 3 •atm) (as the solubility of methane in PTMSP at 25 • C) one gets from Equation (50) the range of Peclét numbers from 0.4 to 3.6.…”

“…Gas permeation through a dense polymeric membrane is governed by a solution-diffusion mechanism where gas dissolution on the feed side and diffusion across the membranes determine an overall gas separation process. Although single gas permeation properties are more often reported, the selectivity of membranes for mixed gas can be different compared to the ideal selectivity based on single gas measurements [1][2][3][4][5][6][7][8][9]. In some cases, ideal selectivities are higher than mixed gas selectivities.…”

n-Octyltrichlorosilane Modified SAPO-34/PDMS Mixed Matrix Membranes for Propane/Nitrogen Mixture Separation

“…Polymeric membranes formed by glassy polymer and rubbery polymer are a hot spot of research due to its excellent gas permeability and good processability [7]. Glassy polymer membranes are constructed from stiff unsaturated frameworks and bulky side chains [8] such as polyetherimide [9,10], poly (1-trimethylsilyl-1-propyne) [11,12]. Glassy polymer membranes usually have good gas permeability, but highly raw prices, complicated synthesis process and poor chemical stability limit its application in practical production.…”