No abstract

A series of cyclic aromatic disulfide oligomers have been synthesized in high yields by catalytic oxidization of arenedithiols in DMAc. The aryl groups contain moieties such as ketone, sulfone, isopropylidene, ether, thioether, and phenylphosphine oxide groups. The cyclic aromatic disulfide oligomers have been analyzed by gradient HPLC, GPC, 1 H-NMR, MALDI-TOF-MS, DSC, and TGA methods. Repeating units up to 9 for some cyclic aromatic disulfide ketone oligomers have been confirmed by MALDI-TOF-MS. In general, these cyclic aromatic disulfide oligomers are soluble in common organic solvents and have sharp melting points. Cyclic disulfide ketone oligomers and cyclic disulfide sulfone oligomers have higher glass transition temperatures and melting points than their ether or thioether counterparts.

A series of new poly(amic acid) salt polymers were synthesized and characterized. It has been found that these poly(amic acid) salt polymers are highly soluble in alcohol-based solvents, a feature that is useful for membrane preparation. It was also found that poly(amic acid) tertiary amine salts can be quantitatively imidized at 150 °C, a temperature that is lower than the imidization temperature of poly(amic acid) or of poly(amic acid) quaternary amine salts of identical backbone structure. This makes poly(amic acid) tertiary amine salt polymer a preferred precursor for preparation of polyimide gas separation membranes. Gas permeation characteristics of dense polyimide films prepared from poly-(amic acid) tertiary amine precursors were further measured and compared to chemically identical polyimide films obtained by conventional methodologies.

Poly(ether ether ketone) (PEEK) hollow fiber membrane modules were scaled up from 2 inch diameter and 16 inch long to 4 inch diameter and 58 inch long (a factor of 90 increase in membrane area) for CO 2 capture from flue gases using a membrane contactor process, which combines advantageous features of both absorption and membrane processes. Field tests of a 4-inch-diameter module with activated methyldiethanolamine (aMDEA) solvent demonstrated greater than 90% CO 2 removal. The mass transfer coefficient in the absorption step was 1.2 (sec)-1 , which is over an order of magnitude greater than that of conventional column contactors. The membrane module was further scaled up from 4 inch to 8 inch diameter (a factor of 3 increase in membrane area). Singlegas permeation measurements indicated that 8-inch modules have an intrinsic CO 2 permeance as high as 2,150-2,670 GPU. One 8-inch-diameter module was tested in membrane contactor mode for CO 2 capture using a simulated flue gas. Carbon dioxide removal rate of 91.3% was achieved with a mass transfer coefficient of 1.5 (sec)-1. Parametric tests indicated CO 2 flux and capture rate increased with increasing feed pressure, solvent flow velocity and solvent temperature. PEEK hollow fiber membrane contactor is effective in capturing CO 2 from low CO 2-concentration feeds, showing its high potential for natural gas flue gas CO 2 capture.