Carbon monoxide membranes

The primary reference method used for measuring carbon monoxide in the United States is based on nondispersive infrared (NDIR) photometry (1, 2). The principle involved is the preferential absorption of infrared radiation by carbon monoxide. Figure 14-1 is a schematic representation of an NDIR analyzer. The analyzer has a hot filament source of infrared radiation, a chopper, a sample cell, reference cell, and a detector. The reference cell is filled with a non-infrared-absorbing gas, and the sample cell is continuously flushed with ambient air containing an unknown amount of CO. The detector cell is divided into two compartments by a flexible membrane, with each compartment filled with CO. Movement of the membrane causes a change in electrical capacitance in a control circuit whose signal is processed and fed to a recorder. 

The authors developed a multi-layered microreactor system with a methanol reforma- to supply hydrogen for a small proton exchange membrane fiiel cell (PEMFC) to be used as a power source for portable electronic devices [6]. The microreactor consists of four units (a methanol reformer with catalytic combustor, a carbon monoxide remover, and two vaporizers), and was designed using thermal simulations to establish the rppropriate temperature distribution for each reaction, as shown in Fig. 3. 

Svetlitchnyi V, C Peschel, G Acker, O Meyer (2001) Two membrane-associated NiFeS-carbon monoxide dehydrogenases from the anaerobic carbon-monoxide-utilizing eubacterium Carboxydothermus hydrogeno-formans. J Bacterial 183 5134-5144. 

Gibbs TK, McCallum C, Pletcher D. 1977. The oxidation of carbon monoxide at platinum and gold metallized membrane electrodes. Electrochim Acta 22 525-530. 

Haem, Fe Chlorophyll, Mg Coenzyme B12, Co Factor F-430, Ni Electron transfer in membranes and elsewhere Light capture and transduction in membranes Transfer of methyl, rearrangements of substrates Activation of carbon monoxide... 

The PEMFCs require expensive polymer membrane (e.g., Nation ), and operate at a low temperature (e.g., 80°C). Although low temperature reduced the cost of material, the heat generated at low temperatures is more difficult to remove. Alternate proton conducting membranes (e.g., inorganic polymer composites) that will operate at a high temperature (e.g., 200°C) are required. The expensive platinum catalyst used for electrochemical reactions can be poisoned by even trace amounts of carbon monoxide in the hydrogen fuel stream. Hence, a more tolerant catalyst material needs to be developed. 

Fig. 3.29 Resistances of the 38 sensor segments of a Sn02-microarray equipped with Si02-membrane during alternating exposure to carbon monoxide contaminated humid air and clean air with the same relative humidity...

Cleavage of the oxirane C-0 bond produces a zwitterionic intermediate (Fig. 10.22), which that can undergo chloride shift (Pathway a) to 2,2-dich-loroacetyl chloride (10.90) followed by hydrolysis to 2,2-dichloroacetic acid (10.91). Furthermore, the zwitterionic intermediate reacts with H20 or H30+ (Pathway b) by pH-independent or a H30+-dependent hydrolysis, respectively. The pH-independent pathway only is shown in Fig. 10.22, Pathway b, but the mechanism of the H30+-dependent hydrolysis is comparable. Hydration and loss of Cl, thus, leads to glyoxylyl chloride (10.92), a reactive acyl chloride that is detoxified by H20 to glyoxylic acid (10.93), breaks down to formic acid and carbon monoxide, or reacts with lysine residues to form adducts with proteins and cytochrome P450 [157], There is also evidence for reaction with phosphatidylethanolamine in the membrane. 

Reiativeiy recentiy, the gases nitric oxide (NO) and carbon monoxide (CO) have been found to act as neurotransmitters in the nervous system. Nitric oxide is synthesized from L-arginine via nitric oxide synthase, requiring NADPH as a co-enzyme and tetrahydrobiopterin as a cofactor. Unlike other neurotransmitters, NO is a smaii, very soiubie moiecuie and cannot be stored in synaptic vesicles. Rather, it is synthesized on demand and freeiy diffuses through membranes. It is not broken down enzymaticaiiy because it is unstabie and degrades rapidiy. NO may have several actions, one of which is to increase the production of cGMP by guanyiyi... 

Oxidation of Carbon Monoxide to Carbon Dioxide Porous AI2O3 membranes... 

Conversion of Carbon monoxide with Hydrogen Nonporous Pd-based membranes... 

Carbon monoxide oxidation, ethane dehydrogenation, ethane hydrogenolysis, ethene hydrogenation. Pt, Mg, Zn catalysts placed either in the pores of the membrane or at the entrance of the membrane pores. 

Guryanova, O. S., Y. M. Serov, S. G. Gul yanova and V. M. Gryaznov. 1988. Conversion of carbon monoxide on membrane catalysts of palladium alloys Reaction between CO and H2 on binary palladium alloys with ruthenium and nickel. Kinet. and Catal. 29(4) 728-731. 

Hugenholtz J, Ivey DM, Ljungdahl LG. 1987. Carbon monoxide driven electron transport in Clostridium thermoautotrophicum membranes. J Bacteriol 169 5845-7. 

The carbon dioxide from the gas mixture is removed by washing with water and the carbon monoxide is removed by absorption or membrane separation. 

Nitric oxide (NO) and carbon monoxide are atypical neurotransmitters. They are not stored in synaptic vesicles, are not released in by exocytosis, and do not act at postsynaptic membrane receptor proteins. NO is generated in a single step from the amino acid arginine through the action of the NO synthase (NOS). The form of NOS initially purified was designated nNOS (neuronal NOS), the macrophage form is termed inducible NOS (iNOS), and the endothelial from is called eNOS. 

Slightly highertemperature(80-120°C), lower cost membrane materials for more efficient waste heat utilization for cogeneration in stationary/distributed applications or as process heat in a fuel reformer, reducing radiator size for transportation applications and for reduced carbon monoxide (CO) management requirements. 

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