Membrane catalytic systems

Considering the characteristic of strength and productivity, it was stated that the Ni-Al support was the most suitable for the formation of the membrane catalytic systems (Tsodikov et al., 2011). In particular, the catalytic components of Table 4.18 were tested after their deposition on the internal surface of membrane channels. 

During the last few years, progress has been made in preparation of polymer-inorganic composites based on the LbL films, mainly related to membrane catalytic systems (Fig. 18). The LbL adsorption in porous polymeric membranes... 

Fig. 18 Membrane catalytic systems (a) TEM images of pores of an alumina membrane modified with a PAA/PAH/(platinum NP) film. Modification of membrane pore surfaces using (b) the LbL deposition of PAA/PAH/(platinum NP) films, or (c) the LbL deposition of PAA/PEI-Pt films followed by a reduction. Reprinted from [125] Copyright 2009 with permission fi om Elsevier...

Membrane techniques have already been combined with two-phase liquid catalysis. The main function of this method is to perform fine separation of undesirable constituents from the catalytic system after phase decantation has already performed the coarse separation of the catalyst from the products. This technique can be applied to ionic liquid systems as a promising approach for the selective removal of volatile solutes from ionic liquids [20]. 

Run/Nin heteronuclear complexes such as (653), in which a photosensitizer [Ru(bpy)3]2+ or [Ru(phen)3]2+ is covalently attached to the Ni1 cyclam complex, have been synthesized in order to improve the efficiency of electron transfer from the photoexcited photosensitizer to the catalytic site.1 44-1646 However, these complexes did not perform particularly well, either due to unfavorable configuration of the Nin-cyclam subunit and the resulting steric hindrance or due to short lifetime of the excited states of the Ru photosensitizer moieties. A stable catalytic system has been prepared by immobilizing macrocyclic Ni11 complexes and [Ru(bipy)3]2+ in a nafion membrane.164... 

The PDMS-membrane-occluded FePcY was the first room temperature catalytic membrane and the first solid catalyst dispersed in dense organic polymer.169 The catalytic system mimics the cytochrome P-450 enzyme and can oxidize alkanes at room temperature with rates comparable to those of the... 

A number of metal porphyrins have been examined as electrocatalysts for H20 reduction to H2. Cobalt complexes of water soluble masri-tetrakis(7V-methylpyridinium-4-yl)porphyrin chloride, meso-tetrakis(4-pyridyl)porphyrin, and mam-tetrakis(A,A,A-trimethylamlinium-4-yl)porphyrin chloride have been shown to catalyze H2 production via controlled potential electrolysis at relatively low overpotential (—0.95 V vs. SCE at Hg pool in 0.1 M in fluoroacetic acid), with nearly 100% current efficiency.12 Since the electrode kinetics appeared to be dominated by porphyrin adsorption at the electrode surface, H2-evolution catalysts have been examined at Co-porphyrin films on electrode surfaces.13,14 These catalytic systems appeared to be limited by slow electron transfer or poor stability.13 However, CoTPP incorporated into a Nafion membrane coated on a Pt electrode shows high activity for H2 production, and the catalysis takes place at the theoretical potential of H+/H2.14... 

After an induction period of ca. 9 hours, the maximum productivity was reached. This was followed by a decrease in activity, which cannot solely be explained by the lack of retention. Calculations showed that at least 20% of the catalyst should still remain in the reactor after 80 h. Additional to this wash-out effect, a deactivation process took place, visible by precipitation of palladium black on the surface of the membrane. Although the catalytic system suffered from deactivation, its selectivity towards 3-phenylbut-l-ene was excellent, being 98% and 85% for the G0- and Gr catalysts respectively. 

Under carefully adjusted experimental conditions unmodified catalysts can be used in nanofiltration coupled homogeneous catalysis. Also non-dendritic but nanosized rigid catalytic systems can be retained by nanofiltration membranes. In this section, unmodified catalysts and rigid non-dendritic systems applied in continuous catalysis will be discussed. 

A catalytic activity must be present that is linked to the replication process, so that variations in replication affect the catalysed reactions. Under such circumstances, variations will change the fitness of the system and lead to evolution. Compartmentalisation of the replicating catalytic system within a membrane-bound volume allows selection of variations, leading to speciation ... 

Figure 7. Solid state UV-vis absorption spectrum of Nafion 417 and Ru(bpy)32-l--modified NPyc catalytic system (psrPyc-Ru(bpy)32+ ) in ambient conditions. In the modification procedure, 1 cm2 test membrane is first dipped in 1 mM Ru(bpy)3 2+ CH3CN H20 (1 1) solution for 30 min followed by water washing.

T0507 Membrane Technology and Research, Inc., VaporSep Membrane Recovery System T0535 Molten Metal Technology, Inc., Quantum Catalytic Extraction Process (Q-CEP) T0546 Natural Attenuation—General... 

TiOz coated with potassium ferrocyanide proved to be an effective catalyst for the reduction of C02 to formic acid and formaldehyde.169 A very stable and reproducible catalytic system was prepared by immobilizing Ni2+ and Ru2+ complexes into Nation membrane, which was used for the selective reduction of C02 to formic acid.170 Formic acid was again formed when Zn and Co phthalocyanines were adsorbed onto a Nation membrane on irradiation with visible light in acidic aqueous solution containing triethanolamine as a hole scavenger. Cobalt comns (B i2) acting as homogeneous catalysts in acetonitrile-methanol solutions induced the formation of formic acid and CO.172... 

Not just the enzyme but also whole enzyme catalytic systems can be mimicked as an example, if the influence of interaction of an enzyme with its environment is the target of the investigation, frequently either model membrane surfaces or aggregates formed with surfactant molecules such as micelles or vesicles are employed. 

In fact, there are examples of chemical reaction in catalysis, which proceed on membranes not dividing the reaction zone into zones. They behave in the system as normal catalysts, e.g. obeying kinetic regularities of heterogeneous catalytic systems. 

The same dendritic ligands, but used in combination with rhodium, were utilized in hydroformylation reactions [46]. Preliminary experiments with this catalytic system in a nanofiltration membrane reactor, however, showed that this membrane set-up was not compatible with the standard hydroformylation conditions because of its temperature and solvent restrictions. 

Ceramic membranes can be used in catalytic systems in three modes ... 

Reactive or catalytic systems are based on pH-responsive hydrogels where the chosen reaction generates a pH shift, which in mm leads to a swelling change in the hydrogel. This response can either be used to increase the internal mesh size to increase solute diffusivity in the gel phase for a diffusive membrane [44] or alternatively the gel can be used as a mechanical valve within the pores of a microporous membrane such that a convective flux may be mmed on or off in response to analyte... 

The present study also investigate the catalytic reduction of CO2 into carbon with CH4 applying for membrane reactor system. 

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