NAMS 2002 Workshop - ICOM 2008

eaction didn t seem to be influenced by the fillers. Both types of membranes
had previously been optimized for applications in alcohol such as isopropanol.
These optimal membranes were reproduced, crosslinked and tested for their
performance in DMF, NMP, DMAC, DMSO and THF. The cross-linked
membranes showed a remarkable performance in DMF with permeabilities at 6
bar ranging from 0,7 to 5,4 l/m² bar h. Rejections of rose Bengal (1017Da) up to
99% and of methyl orange (327,2 Da) up to 97% were found. Permeability of
DMF, NMP and DMAc of filled and unfilled membranes dropped considerably at
higher pressures (up to 40 bar), most probably due to compaction of the
membrane. This may be resolved by further optimization and fine-tuning of the
membrane composition. The long term stability was estimated by 10 h lasting
dead end filtrations in DMF, DMSO and THF. The results showed that rejections
and permeabilities remained virtually constant after an initial stabilizing period of
about one hour.
Overall, these are very promising results. Modified polyimide membranes were
created that are stable in a range of aprotic solvents. Both the unfilled polyimide
membranes and those filled with nano-sized zeolite precursors have high
permeabilities and a good MWCO in these solvents. The easy methodology may
allow for a straightforward upscaling of these membranes.