Torlon® hollow fiber membranes for organic solvent reverse osmosis separation of complex aromatic hydrocarbon mixtures

Abstract

Defect‐free polyamide‐imide (Torlon®) hollow fiber membranes were fabricated to investigate the potential for polymer‐based organic solvent reverse osmosis (OSRO) separations. The quality of the membranes was assessed by gas permeation, and the membranes were found to be defect‐free. Low molecular weight cut‐offs of ~180 g/mol were obtained using a complex mixture of aromatic hydrocarbons relevant to refinery separations. We demonstrate bulk OSRO‐type separations of 80/20 (mol%) mixtures of toluene and 1,3,5‐triisopropylbenzene (TIPB, 204 g/mol). At an upstream pressure of 80–90 bar, we find that the permeate concentration was approximately 98.5–99.0 mol% toluene and that the TIPB rejection coefficient was approximately 90% in the permeate. We observed low solvent permeances of 0.01 L/m2 hr bar, which can be attributed to the low OSRO driving forces and the low permeability of Torlon®. The membranes were found to provide stable performance up to pressures of 95 bar and temperatures of 60°C.

Hydrocarbon separations by glassy polymer membranes

“…OSRO is emerging to compete with pervaporation for liquid organics separations. [26,184] Jang and coworkers [131] studied aromatics separation in defect-free Torlon ® hollow fiber membranes using OSRO (Figure 3e). The hollow fibers showed p-xylene and o-xylene rejections $4 and $17%, respectively.…”

“…Adapted from ref. [131] with permission from Wiley blocking CH 4 molecules by n-C 4 H 10 sorption. [85] The size and structure of side groups is known to strongly affect permeation properties of polyacetylenes.…”

“…[ 130 ] Clearly, the excellent plasticization resistance of polyamide‐imides made them promising candidates for hydrocarbon separations. [ 131 ] For example, attractive aromatics/aromatics separation factors were reported in defect‐free asymmetric Torlon ® hollow fiber membranes. [ 131 ]…”

“…[ 131 ] For example, attractive aromatics/aromatics separation factors were reported in defect‐free asymmetric Torlon ® hollow fiber membranes. [ 131 ]…”

“…Attractive aromatics/aromatics selectivity was seen in a polyamide‐imide under 95 bar trans‐membrane pressure. [ 131 ] The membrane showed unsurprisingly low permeance as a result of strong interchain hydrogen bonds and low FFV. Pinnau and coworkers attempted to address the low permeability challenge of amide‐containing polymers by synthesizing polyamides of intrinsic microporosity (PIM‐PAs) using a triptycene‐based diamine monomer.…”