Polymeric membrane pervaporation

Transport phenomena through polymeric systems

Separation of organic–organic mixtures by pervaporation—a review

Polymer Blends (or Alloys)

https://ris.utwente.nl/ws/files/6534926/terminology.pdf

Terminology for Membrane Distillation

Membranes prepared from polymeric alloys of polyphosphonates and acetyl cellulose are highly permeable to benzene and the cyclohexene, but practically impermeable to the aliphatic hydrocarbons cyclohexane and decalin. Pervaporation and osmotic distillation techniques were used in order to achieve separation of the benzene–cyclohexane mixtures. The flux of the permeate increases sharply with increasing temperature, concentration of benzene in the feed solution, and fraction of polyphosphonate in the membrane. The increase of permeate flux is accompanied by a slight decrease of the separation factors. The permeation characteristics of the membranes were compared with those predicted from the results of sorption experiments. The agreement between the observed and the predicted fluxes and separation factors indicates that the permeation mechanism can be described in terms of molecular diffusion. The high selectivity of the membranes makes possible the development of a novel “osmotic distillation” technique. Such a technique, which combines osmotic permeation of organic liquids with conventional distillation, may be advantageous in the separations of azeotropic mixtures.

A study of permeation of organic solvents through polymeric membranes based on polymeric alloys of polyphosphonates and acetyl cellulose. II. Separation of benzene, cyclohexene, and cyclohexane

Soluble chloromethylated polystyrene and its copolymers with vinylidene chloride as well as poly(phenyl oxides) brominated in the side chains and in the ring were synthesized and characterized in detail by NMR. The halogenated polymers were phosphonylated with alkyl phosphites. Uncrosslinked polymers with pendent phosphonate groups were prepared in the presence of etheral solvents, which solvate the ionic intermediates of the Arbuzov reaction. These polyphosphonates are highly hygroscopic and are soluble in a variety of solvents. Their Tg's are in the range of 50–175°C. Their thermal behavior was analyzed on the basis of thermogravimetric measurements combined with mass-spectrometric analysis. Poly(styrene phosphonate) seems to be the most stable, and its thermal decomposition starts at ∼330°C. The polymeric phosphonates are compatible with an unusually large number of polymeric systems and seem to form “true” polymeric alloys with acetylcellulose.

Synthesis and characterization of polymers with pendent phosphonate groups

The solubility of benzene in the polymeric alloys (P/A) consisting of polyphosphonates (PPN) and acetyl cellulose (AC) is nearly two orders of magnitude larger than that of cyclohexane. The preferential absorption of benzene by P/A membranes is also maintained upon its dilution with cyclohexane, though the solubility of the latter in the P/A membranes is affected by their swelling with benzene. Absolute values of solubilities increase exponentially with increase in the weight fraction of PPN in P/A membranes. They are also affected by the thermal and solvent “history” of a membrane. For the sorption of benzene by a P/A-50 membrane 



The diffusion coefficients of benzene in the solvent-swollen membranes are strongly concentration dependent and increase exponentially up to ∼10−6 cm2/sec with the increase in the volume fraction of benzene. Values of D0 are of the order of 10−11 to 10−10 cm2/sec. Sorption experiments indicate a pronounced time dependence of the diffusion coefficients. Self-diffusion experiments conducted with 14C-labeled benzene revealed that values of D* derived from the steady-state permeation measurements are in certain membranes much larger than those derived from the “time-lag.” It was observed that the discrepancies between the two sets of values depend strongly upon the thermal “history” of the membranes and vanish when the membranes are swollen to a high degree at elevated temperatures. The above phenomenon is discussed in terms of differences in the membrane structure; a model is proposed. The apparent energy of activation of diffusion of benzene at 10–40°C in the swollen P/A-50 membrane EBD 14.4 kcal/mole was derived from the temperature dependence of the self-diffusion coefficients. For the same temperature range at C(B) → 0, EB = 8.3 kcal/mole was derived from the final slopes of the desorption curves. The small difference between the energies of activation in a swollen and in an unswollen system is due to the fact that at room temperature it remains below Tg even upon extensive swelling with benzene.

Polymeric alloys of polyphosponates and acetyl cellulose. I. Sorption and diffusion of benzene and cyclohexane

Phosphorylation of methylbrominated poly(phenylene oxide) by hydroquinone phosphate

Polymer alloys consist of two (or more) polymers which are compatible at the molecular level. The virtue of such materials is that they assimilate the properties of each of the polymeric components into a new, distinct product. Such an alloy displays a glass transition temperature, Tg°, intermediate between those of the two polymer components, and can be tailored into a product with desired properties, e.g., hydrophilic/hydrophobic balance.

Israel Cabasso

Papers

A study of permeation of organic solvents through polymeric membranes based on polymeric alloys of polyphosphonates and acetyl cellulose. II. Separation of benzene, cyclohexene, and cyclohexane

Synthesis and characterization of polymers with pendent phosphonate groups

Polymeric alloys of polyphosponates and acetyl cellulose. I. Sorption and diffusion of benzene and cyclohexane

Phosphorylation of methylbrominated poly(phenylene oxide) by hydroquinone phosphate

Advanced Polymer Alloys Containing Polyphosphonate Components