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In the present work, the potential of polyPOSS-imide membranes designed for the purification of H2 from a coke gas (utilized in the steelmaking industry) is investigated. Aiming at upscaling the membrane fabrication, tubular single-channel and multi-channel membranes were prepared, using polyhedral oligomeric silsesquioxane (POSS) nanostructures and 6FDA as reactive precursors. The gas separation performance has been investigated by means of single gas and quaternary (H2, CH4, CO2, N2) mixtures, the latter used to simulate the conditions expected at the membrane module inlet in the process of upgrading H2 from a coke oven gas. Preliminary results obtained on tubular membranes showed that the fabricated membranes can achieve high H2 permeance (>2000 GPU), displaying also suitable selectivity towards CO2, N2 and CH4. The selectivity of these upscaled tubular membrane samples meets the performance of those previously obtained for the disc-shaped lab-scale membranes. These results revealed the promising potential in the upscaling of polyPOSS-imide membranes fabricated via interfacial polymerization on ceramic porous supports for H2 upgrading.

PolyPOSS-imide membranes are promising for separating H2 from larger molecules (CO2, N2, CH4) at temperatures up to 300 °C. Their fabrication involves two steps: interfacial polymerization of POSS and 6FDA, followed by thermal imidization. This work provides a systematic study of the effects of cations on membrane properties and performance. For this, two distinct POSS molecules were used: functionalized with -NH3+Cl− or, so far unexplored, -NH2. The ammonium groups are partially deprotonated by using three different bases, LiOH, NaOH, and KOH. We demonstrate that the introduced cations affect the film thickness but not the molecular composition of the polyamic acid. All polyamic acids can be imidized, but the cations reduce the imidization kinetics as well as the loss of organic crosslinkers. For flat disc membranes, at 200 °C, the absence of cations results in comparable permeability combined with higher selectivity for H2/N2. This, and the possibility to discard adding a base, motivated a scale-up study of the new POSS. For tubular membranes, much higher ideal and mixed gas selectivities are found than for membranes where NaOH was added. Results indicate that the new route allows more reproducible production of defect free membranes and has potential for larger-scale polyPOSSimide fabrication.

Ceramic-supported polymer (CSP) membranes were prepared based on Torlon, P84, and Matrimid. The dehydration performance of these membranes was determined by pervaporation of n -butanol/water mixtures (95/5 wt%) at 95 °C. Based on their performance P84 was selected for further testing. P84 membranes showed excellent separation performance in dehydration of n -butanol for at least 300 days. Different curing temperatures in the range of 70–300 °C were used. The most significant flux difference was seen for a P84 membrane cured at 300 °C, compared to the lower temperatures. The separation performance of a P84 CSP membrane at 150 °C showed water fluxes in the range of 1–6 kg/m 2 h and separation factors of at least 360. The membrane life-time in n -butanol/water mixtures ranges from 80 to 140 days at 150 °C. No clear relation between curing temperature and membrane stability could be derived. Reasonable separation performance of a P84 CSP membrane in an ethanol/water mixture was demonstrated. Stable performance at 150 °C was observed for the dehydration of t -butanol up to at least 250 days.