Electrolytic hydrogenation

The impurities usually found in raw hydrogen are CO2, CO, N2, H2O, CH, and higher hydrocarbons. Removal of these impurities by shift catalysis, H2S and CO2 removal, and the pressure-swing adsorption (PSA) process have been described (vide supra). Traces of oxygen in electrolytic hydrogen are usually removed on a palladium or platinum catalyst at room temperature. 

E. Findl and M. Klein, "Electrolytic Hydrogen—Oxygen Fuel, CeU Battery," Proceedings of the 20th Power Sources Conference, Red Bank, N.J., 1966. 

Oxidation and chlorination of the catalyst are then performed to ensure complete carbon removal, restore the catalyst chloride to its proper level, and maintain full platinum dispersion on the catalyst surface. Typically, the catalyst is oxidized in sufficient oxygen at about 510°C for a period of six hours or more. Sufficient chloride is added, usually as an organic chloride, to restore the chloride content and acid function of the catalyst and to provide redispersion of any platinum agglomeration that may have occurred. The catalyst is then reduced to return the metal components to their active form. This reduction is accompHshed by using a flow of electrolytic hydrogen or recycle gas from another Platforming unit at 400 to 480°C for a period of one to two hours. 

Papaverine was condensed with formaldehyde to methylenepapaverine (XXII), which on successive catalytic and electrolytic hydrogenation yielded two dZ-methyltetrahydropapaverines (XXIII), which on successive demethylation, condensation with formaldehyde and re-methylation yielded a mixture of bases, from which the two optically inactive corydalines (XXIV), jwesocorydaline, m.p. 163-4° (nac.), and dZ-corydaline, m.p. 132-3°, identical with the products obtained by the hydrogenation of dehydrocorydaline were isolated. For the conversion of corycavine to corydaline, see p. 304. 

Cathodic hydrogen evolution is one of the most common electrochemical reactions. It is the principal reaction in electrolytic hydrogen production, the auxiliary reaction in the production of many substances forming at the anode, such as chlorine, and a side reaction in many cathodic processes, particularly in electrohydrometallurgy. It is of considerable importance in the corrosion of metals. Its special characteristic is the fact that it can proceed in any aqueous solution particular reactants need not be added. The reverse reaction, which is the anodic ionization of molecular hydrogen, is utilized in batteries and fuel cells. 

Parsons R. 1958. The rate of electrolytic hydrogen evolution and the heat of adsorption of hydrogen. Trans Farad Soc 94 1053-1063. 

Trasatti S. 1972. Work function, electronegativity, and electrochemical behaviour of metals. IB. Electrolytic hydrogen evolution in acid solutions. Electroanal Chem Interfacial Electrochem 39 163-184. 

In alkaline electrolyzers, hydrogen is obtained at the cathode with a purity of approximately 98 vol%, with oxygen and water vapor as the only impurities. Hydrogen may be further purified to almost 100% by the removal of oxygen in a catalytic deoxidizer and the subsequent removal of water vapor in a dryer. In the purification step, 5-10% of the produced hydrogen may be lost therefore, the use of electrolytic hydrogen without purification should always be considered in priority for each application. 

Laskin J.B., Feldwick R.D., Recent development of large electrolytic hydrogen generators, Int. ]. Hydrogen Energ., 3, 311-320, 1978. 

Dyer C.K., Improved cathodes for industrial electrolytic hydrogen production, Int.. Hydrogen Energ., 9(12), 993-995,1984. 

Saxe M., Alvfors P., Advantages of integration with industry for electrolytic hydrogen production, Energy, 32(1), 42-50,2007. 

Agbossou K., Kolhe M.L., Hamelin J., Bernier E., Bose T.K., Electrolytic hydrogen based renewable energy system with oxygen recovery and re-utilisation, Ren. Energ., 29,1305-1318, 2004. 

J. Ivy, Summary of Electrolytic Hydrogen Production, NREL/MP-560-36734, September 2004. Available at www.nrel.gov... 

Standard sieve, were introduced into the reactor and electrolytic hydrogen (99.9% purity) was passed up through the bed at 2.8 1/min at S.T.P. The pressure within the reactor was held constant during the entire run. The gas flow was initiated at the same time as the heating cycle. The temperature of the reactor was raised to the desired value over a period of about one hour and held constant at that value for the duration of the experiment. 

Dutta S (1990) Technology assessment of advanced electrolytic hydrogen production. Int J Hydrogen Energy 15 379-386... 

Carpetis C (1984) An assessment of electrolytic hydrogen production hy means of photovoltaic energy conversion. Int J Hydrogen Energy 9 969-991... 

Ogden JM, Williams RH (1990) Electrolytic hydrogen from thin-film solar cell. IntJ Hydrogen Energy 15 155-169... 

Fig. 18. Dependence of the exchange current density of electrolytic hydrogen evolution on the electronic work function. [C

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