Catalytic decomposition of hydrogen

Hydrogen sulfide has potentially high economic value if both sulfur and hydrogen can be recovered. Due to thermodynamic constraints, thermal catalytic decomposition is a good candidate for membrane reactor application. Silica membranes appear more suitable than noble metal membranes which are affected by chemical attack by hydrogen sulfide.  

A possible scheme of membrane assisted H2S decomposition is based on Claus process to generate heat for the thermal decomposition and on a lower temperature decomposition step equipped with H2 permeable membrane. In this way unconverted hydrogen sulfide, recycled to the Claus reactor, produces the required reaction heat according to the following reaction  

The product stream, containing H2S, H2, and S2, leaves through the top of the catalytic reactor and enter the first membrane module. Hydrogen is removed in the separation module and the retentate is cooled to the dew point temperature to separate sulfur. The decomposition gas leaving the third separator is recycled to the Claus reactor to treat the unconverted H2S and produce the required reaction heat through the Claus process. Hydrogen streams are cooled, compressed and further cooled before a final purification with a dedicated PSA. Since no natural gas is used the proposed scheme allows hydrogen production without CO2 emissions. 

This chapter has reported the basic features of a membrane reactor the properties of selective membranes, fabrication methods, actual markets and a cost analysis are described and assessed. 

Two membrane reactor configurations, the staged membrane reactor (SMR) and the integrated membrane reactor (IMR), are presented and compared, with the following main outcomes  

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Concentration Effects. The reactivity of ethyl alcohol—water mixtures has been correlated with three distinct alcohol concentration ranges (35,36). For example, the chromium trioxide oxidation of ethyl alcohol (37), the catalytic decomposition of hydrogen peroxide (38), and the sensitivities of coUoidal particles to coagulation (39) are characteristic for ethyl alcohol concentrations of 25—30%, 40—60%, and above 60% alcohol, respectively. The effect of various catalysts also differs for different alcohol concentrations (35). 

Catalytic Decomposition of Hydrogen Peroxide by Ferrous Ions... 

The catalytic decomposition of hydrogen peroxide under the action of the Fe2+/Fe3+ ions includes the following steps (H20, T = 298 K, acidic medium) [14—17] ... 

As in the case with catalytic decomposition of hydrogen peroxide, radical generation by the reaction of metal ions with hydroperoxide consists of several steps. In an aqueous solution, first ROOH is substituted in the internal coordination sphere of the ion followed by the transfer of an electron from the ion to ROOH accompanied by the subsequent cleavage of hydroperoxide to RO and OH, for example,... 

Our approach utilized the metals gold, platinum, then later gold, platinum, and nickel electroplated in succession because the catalytic decomposition of hydrogen peroxide reaction we tested was most efficiently catalyzed with platinum.After fabrication of the nanowires they were freed by removing the conductive silver backing with nitric acid and the sacrificial template with a strong base, sodium hydroxide. Then nanorods were washed with deionized water and ultracentrifuged to achieve a neutral pH. 

One of the potential applications of catalytically driven motors is in microelec-tromechanical devices (MEMS). Catchmark capitalized on the concept of the platinum-gold nanorods by designing gold gears (150 /rm in size) with platinum spots on the teeth (Fig. 3.4) to produce the first rotating devices driven by the catalytic decomposition of hydrogen peroxide. 

Hydrazine hydrate is used as a reducing agent in synthetic and analytical reactions and as a solvent for many inorganic compounds. It also is used with methanol as a propellant for rocket engines. Another apphcation is catalytic decomposition of hydrogen peroxide. 

The catalytic decomposition of hydrogen peroxide at the surface of platinum foil investigated by Bredig and Tetelow (Zeit. Elehtro-chem. XII. 581, 1906) was found to obey a unimolecular law and the seat of the reaction was shown to be the thin saturated layer at the surface of the metal. 

Moreover, the conductivity, and hence the catalytic decomposition of hydrogen peroxide, has been observed to influence the stability of the oxygen electrode. The stability of phthalocyanine catalysts is a decisive factor for the practical applicability of organic catalysts in fuel cells operating in an acid medium. This is therefore a very important observation. The observed disturbance of the delocalization of the n electrons (rubiconjugation) in Fe-polyphthalocyanines, in addition to the correlation between conductivity on the one hand, and electrocatalysis and catalytic decomposition of hydrogen peroxide on the other, leads to a special model of the electroreduction of oxygen on phthalocyanines. The model... 

Table 5. Activities of some metal chelates in the catalytic decomposition of hydrogen peroxide and in electrocatalysis with an oxygen cathode 38>...

Catalytic Decomposition of Hydrogen Peroxide by Ferrous Ions Catalysis by Transition Metal Ions and Complexes in Liquid-Phase Oxidation of Hydrocarbons and Aldehydes by Dioxygen... 

Polymer-metal complexes often exhibit high efficiency in the catalytic decomposition of hydrogen peroxide. The following reasons for this activity have been advanced, (i) Some polymer-metal complexes contain incomplete complexes due to steric hindrance, and this contributes to their catalytic activity121, 122. (ii) In other polymer complexes, the coordinate bond between polymer ligand and metal ion is relatively weak and the substrate coordinates with high frequency124. ... 

Another example of a reaction nearly independent of pressure in this way is the catalytic decomposition of hydrogen iodide on the surface of a heated gold wire. X The initial pressure of the gas can be varied from 100 mm. to 400 mm. with a resulting change in the absolute rate of reaction which amounts to about 45% only instead of 400%. 

It is probable that the actual mechanism of the decomposition is unimolecular, but, the observed order of the reaction being zero, we cannot tell whether the molecules decompose singly or by interaction with their neighbours. The catalytic decomposition of hydrogen iodide on the surface of platinum can actually be shown to be unimolecular. The heat of activation in this instance is even lower (14,000 cals.), but is again subject to the same uncertainty as the values for the unimolecular reactions of nitrous oxide. 

Ealy, "Catalytic Decomposition of Hydrogen Peroxide Foam Production," Chemical Demonstrations, A Sourcebook for Teachers, Vol. 1 (American Chemical Society, Washington, DC, 1988), pp. 101-102. Oxygen gas is catalytically produced in the presence of detergent resulting in the formation of a large quantity of foam. 

Oxygen is the most abundant element in the earth s crust. Dioxygen (O2) can be prepared in the laboratory by electrolysis of water, by catalytic decomposition of hydrogen peroxide, or by thermal decomposition of KCIO3. Oxygen is manufactured by fractional distillation of liquefied air and is used in making steel. The O2 molecule is paramagnetic and has an... 

Lin, S. and Gurol, M., Catalytic decomposition of hydrogen peroxide on iron oxide kinetics, mechanism, and implications, Environ. Sci. Technol., 32(10), 1417-1423,... 

Haber, F. and Weiss, J., The catalytic decomposition of hydrogen peroxide by iron salts, /. Proc. Royal Soc. Assoc., 147, 332, 1934. 

Kremer, M.L., Nature of intermediates in the catalytic decomposition of hydrogen peroxide by ferric ion, Trans. Faraday Soc., 58, 702-706, 1962. 

Goldstein S, Lind J, Merenyi G (2002) The reaction of ONOO with carbonyls estimation of the half-lives of 0N0C(0)0" and 02N0C(0)0". J Chem Soc Dalton Trans 808-810 Haber F, Weiss J (1932) Ober die Katalyse des Hydroperoxydes. Naturwissenschaften 20 948-950 Haber F, Weiss J (1934) The catalytic decomposition of hydrogen peroxide by iron salts. Proc R Soc (Lond) A 147 332-352... 

Metal salt dyes cannot be removed with these preparations because of the catalytic decomposition of hydrogen peroxide and their resistance to reducing agents. 

J Haber, F., Weiss, J. The Catalytic Decomposition of Hydrogen Peroxide by Iron Salts. 

Huang H-H, Lu M-C, Chen J-N. Catalytic decomposition of hydrogen peroxide and 2-chlorophenol with iron oxides. Water Res 2001 35 2291-2299. 

De Laat, 1. and H. Gallard, H. (1999) Catalytic decomposition of hydrogen peroxide by Fe(III) in homogeneous aqueous solution Mechanism and kinetic modeling. Environ. Sci. Technol. 33, 2726-2732. 

The catalytic decomposition of hydrogen peroxide as catalysed by oxide surfaces has been extensively studied by several authors [413-415], The activity on spinel cobaltite oxides supported on carbon has been reported [409-412, 416-419] to follow the order... 

Lin, S. S. Gurol, M. D. Catalytic Decomposition of Hydrogen Peroxide on Iron Oxide Kinetics, Mechanism, and Implications, Environ. Sci. Technol. 1998, 32, 1417-1423. 

Huang HH, Lu MC, Chen JN, Lee CT. Catalytic decomposition of hydrogen peroxide and 4-chlorophenol in the presence of modified activated carbons. 

Hwang, G.J. and Onuki, K., Simulation study ou the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the thermochemical water splitting IS process. Journal of Membrane Science, 194, 207, 2001. 

DOT CLASSIFICATION 6.1 Label Poison SAFETY PROFILE Poison by ingestion, inhalation, and intraperitoneal routes. Human systemic effects by inhalation lachrymation and other eye effects and structural or funcdonal changes in trachea or bronchi. Experimental reproductive effects. Mutation data reported. Explodes on contact with 1 -methylimidazole. Catalytic decomposition of hydrogen peroxide can be hazardous. See also OSMIUM. 

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