Poly -based composite membranes

A process performance study has been conducted by David et al. [96] taking the coupling of the esterification reactions of 1-propanol and 2-propanol with propionic acid to pervaporation as a model system. Toluene sulphonic acid was applied as the homogeneous acid catalyst. A poly (vinyl alcohol)-based composite membrane, supplied by Carbone Lorraine-GFT, was used. Figure 5.10 shows the comparison between the esterification reaction with and without pervaporation. Without pervaporation, the conversion factor reaches a limit, which corresponds to the equilibrium of the esterification reaction. Coupling of the esterification to pervaporation allows the reaction to reach almost complete conversion. 

Keurentjes et al. [98] studied the esterification of tartaric acid with ethanol using pervaporation. The equilibrium composition could be shifted significantly towards the final product diethyltartrate by integration of pervaporation with hydrophilic poly(vinyl alcohol)-based composite membranes in the process. Based on the kinetic parameters, an optimum membrane surface area could be calculated that results in a minimal reaction time for the esterification reaction. Where the membrane surface area to volume ratio is too low, the water removal is rather slow, whereas at high surface area to volume ratios significant amounts of ethanol are removed as well. 

Table 4.3 Water content and proton conductivities of sulfonated poly(arylene ether ketone)s-based composite membranes...

Poly(arylene ether)-Based Composite Membranes... 

According to literary data, the following mixtures of aromatic/aliphatic-aromatic hydrocarbons were separated toluene/ n-hexane, toluene/n-heptane, toluene/n-octane, toluene/f-octane, benzene/w-hexane, benzene/w-heptane, benzene/toluene, and styrene/ethylbenzene [10,82,83,109-129]. As membrane media, various polymers were used polyetherurethane, poly-esterurethane, polyetherimide, sulfonyl-containing polyimide, ionicaUy cross-linked copolymers of methyl, ethyl, n-butyl acrylate with acrilic acid. For example, when a composite polyetherimide-based membrane was used to separate a toluene (50 wt%)/n-octane mixture, the flux Q of 10 kg pm/m h and the separation factor of 70 were achieved [121]. When a composite mebrane based on sulfonyl-containing polyimide was used to separate a toluene (1 wt%)/ -octane mixture, the flux 2 of 1.1 kg pm/m h and the separation factor of 155 were achieved [10]. When a composite membrane based on ionically cross-linked copolymers of methyl, ethyl, w-butyl acrylate with acrilic acid was used to separate toluene (50 wt%)//-octane mixture, the flux Q of 20-1000 kg pm/m h and the separation factor of 2.5-13 were achieved [126,127]. 

Zhang et al. [128] synthesized a self-humidifying membrane based on a sulfonated poly(ether ether ketone) (SPEEK) hybrid with a sulfated zirconia (SO / ZrO2, SZ) -supported platinum catalyst (Pt-SZ catalyst). This type of composite membrane has a higher proton conductivity than plain SPEEK, due to the effect of the Pt-SZ catalyst the membrane also provided excellent single cell performance at low humidity. 

M. Deka, A. K. Nath, and A. Kumar, Effect of dedoped (insulating) polyaniline nanofibers on the ionic transport and interfacial stability of poly(vinylidene fluoride-hexafluoropropylene) based composite polymer electrolyte membranes, J. Membrane Set, ill, 188-194 (2009). 

The acid-base Nafion composite membranes include blends of Nafion with polypyrrole (PPy) [98-104], polybenzimidazole (PBI) [105-107], poly (propyleneoxide) (PPO) [108, 109], polyfurfuryl alcohol (PFA) [110], poly(vinyl alcohol) (PVA) [111-115], sulfonated phenol-formaldehyde (sPF) [116], polyvinylidene fluoride (PVdF) [117-122], poly(p-phenylene vinylene) (PPV) [123], poly(vinyl pyrrolidone) (PVP) [124] polyanifine (PANI) [125-128], polyethylene (PE) [129], poly(ethylene-terephtalate) [130], sulfated p-cyclodextrin (sCD) [131], sulfonated poly(ether ether ketone) (sPEEK) [132-135], sulfonated poly(aryl ether ketone) (sPAEK) [136], poly(arylene ether sulfone) (PAES) [137], poly(vinylimidazole) (PVl) [138], poly(vinyl pyridine) (PVPy) [139], poly (tetrafluoroethylene) (PTFE) [140-142], poly(fluorinated ethylene-propylene) [143], sulfonated polyhedral oligomeric silsesquioxane (sPOSS) [144], poly (3,4-ethylenedioxythiophene) (PEDT) [145, 146], polyrotaxanes (PR) [147], purple membrane [148], sulfonated polystyrene (PSSA) [149, 150], polystyrene-b-poly(ethylene-ran-butylene)-bpolystyrene (SEES) [151], poly(2-acrylamido-2-methyl-l-propanesulphonic acid-co-l,6-hexanediol propoxylate diacrylate-co-ethyl methacrylate) (AMPS) [152], and chitosan [31]. A binary PVA/chitosan [153] and a ternary Nafion composite with PVA, polyimide (PI) and 8-trimethoxy silylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS) has also been reported [154]. 

Some PVA-based membranes showing modest selectivities, like sulfonated PVA [339] and PVA/PSSA/mordenite [361] exhibit unexpected high MPD (81 and 74 mW.cm , respectively) at 70 °C. PVA/poly(ether sulfone)/PWA membranes [354], with very low selectivity, show MPD in the range 95-117 mW.cm at 80 °C. In summary, the performance of DMFC with PVA-based membranes could not yet overpass the results obtained with Nafion composite membranes, although some promising results have been obtained during the last years. Indeed, the results shown in Table 6.3 forNafi(Mi/PVA blends [114] and PVA-coated Nafion membranes are superior to those obtained with PVA-based membranes. 

A PVDF-HFP/PSSA composite membrane was tested in DMFC [490] reaching 80 mW.cm at 60 °C. When Si02 was added to the composite the MPD increased up to 110 mW.cm at the same temperature, which represents the best DMFC performance for a PVDF-based membrane. Recently, a composite of PVDF with sulfonated poly(styrene-b-ethylene butylenes-b-styrene) (sPSEBS) was reported to deliver up to 72 mW.cm at 60 °C in a DMFC, although the characteristics of the catalysts and the MEA were not described [491]. 

Na T, Shao K, Zhu J, Sun H, Xu D, Zhang Z, Lew CM, Zhang G (2013) Composite membranes based on fully sulfonated poly(aryl ether ketone)/epoxy resin/different curing agents for direct methanol fuel cells. J Power Sources 230 290-297... 

Surya Prakash GK, Smart MC, Wang QJ, Atti A, Pleynet V, Yang B, McGrath K, Olah GA, Narayanan SR, Chun W, Valdez T, Surampudi S (2004) High efficiency direct methanol fuel cell based rat poly(styrenesulfonic) acid (PSSA) - poly(vinylidene fluraide) (PVDF) composite membranes. J Fluorine Chem 125 1217-1230... 

Stable membrane gas desorption (MGD) using a thin-film composite membranes made of hydrophobic glassy pofymer poly[l-(trinietliylsyhl)-l )ropyne] on a flexible metal-ceramic microfilter was achieved based on MDEA as COrabsoiption liquid. MGD can be used as a novel methodology for desorption of amine solution for natural gas treatment In particular, MGD can be useful for obtaining CO2 with methane pipeline specification... 

The phenomenon of PV was described for the first time by Kober in 1917 (Kober, 1919). The real breakthrough of this membrane process started in the 1980s with the development of a series of industrial appUcations and the use of poly(vinyl alcohol)-poly(acryl nitrile) (PVA-PAN) composite membranes for the dehydration of alcohol/water azeotropic mixtures (Thsel and Bruschke, 1985). The other main PV commerdal application was developed by Membrane Technology Research (MTR) and is based on the removal of VOCs from contaminated water (Cox and Baker, 1998). 

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