Hydrogenations in CO

R. M. Torres Sanchez, A. Ueda, K. Tanaka and M. Hamta, Selective oxidation of CO in hydrogen over gold supported on manganese oxides, J. Catal. 168, 125—127 (1997). 

P. Ratnasamy, D. Srinivas, C. V. V. Satyanarayana, P. Manikandan, R. S. Sendiil Kumaran, M. Sachin, and V. N. Shetti, Influence of flie support on flie preferential oxidation of CO in hydrogen-rich stream reformates over flie CuO—Ce02—Zr02 system, J. Catal. 221, 455 65... 

H. Tanaka, S.-I. Ito, S. Kameoka, K. Tomishige, and K. Kunimori, Promoting effect of potassium in selective oxidation of CO in hydrogen-rich stream on Rh catalysts, Catal. Commun. 4, 1-4... 

The surface properties and paramagnetic species in the mixed Ce02-Zr02 oxides have also been investigated by EPR in relation to steam reforming of ethanol76 and oxidation of CO in hydrogen-rich steam reformates.77 A complex... 

The water-gas-shift reaction (Eqn. 1) has been studied extensively as a basis for improving the yield of hydrogen production. In many applications, including ammonia synthesis or fuel reforming for proton exchange membrane (PEM) fuel cells, the maximum acceptable level of CO in hydrogen is in the parts per million range, therefore the water-gas shift reaction is needed. 

The selective oxidation or preferential oxidation of CO in hydrogen-rich stream is another important object for ceria based catalysts. The gas mixture from steam reforming/partial oxidation of alcohols or hydrocarbons, followed by the WGS reaction contains mainly FI2, CO2 and a small portion of CO, H2O, and N2. When such gaseous stream would be taken as input for hydrogen fuel cells, the CO has to be removed to avoid poisoning of the anode electrocatalysts. Ceria based nanomaterials, such as ceria/gold, ceria/copper oxide catalysts exhibit suitable catalytic activities and selectivities for CO PROX process. 

NaY (Katalistiksj Si/Al=2 56) was used as a starting material for preparation of NH, K, Cs exchanged samples and three series of stab.lliJed Y-zeolites. Nickel was introduced before molybdenum by ion-exchange from Wi(NO )2 solution. Molybdenum was incorporated into the zeolite by sublimation of Mo(CO) in hydrogen stream at room temperature. Sulfided and non-sulfided Mo Y and Ni-Mo-Y samples were characterized with XRD, ND sorption capacity and FTIR spectroscopy. Each sample (0.25 g. 0.5-1 mm grains) was partially decarbonylated at 425 K before the WGS reaction and next presulfided with 1 2 vo1 %)/H2 mixture at 675 K, Catalysts after pre-... 

There is clear evidence that adsorbate and alloyed metal atoms on platinum surface promote CO electro-oxidation. The reduced overpotential is primarily a result of the promotion of the activation of water. The subsequent kinetics are determined by the details of a Langmuir-Hinshelwood reaction between the adsorbed oxidant (OH) and adsorbed CO. Evidence is also presented that relates this promotion (or poisoning) of CO electro-oxidation to tolerate CO in hydrogen feeds in the hydrogen electro-oxidation reaction. An alternative mechanism that may operate at low potentials [79,113] may be that the reduction in CO adsorption energy on platinum induced by Ru [86,113,114] results in a higher equilibrium concentration of nonpoisoned sites. The relative importance of these mechanisms is a function... 

Selective oxidation of CO in hydrogen over different catalysts has been extensively examined. Most research to date has occurred with formulations that include a precious metal component supported on an alumina carrier. The catalyst-mediated oxidation of CO is a multistage process, commonly obeying Langmuir-Hinshelwood kinetics for a single-site competitive mechanism between CO and 02. Initially, CO is chemisorbed on a PGM surface site, while an 02 molecule undergoes dissociative chemisorption either on an adjacent site or on the support in order for surface reaction between chemisorbed CO and O atoms to produce C02. 

Ratnasamy, P. Srinivas, D Satyanarayana, C.V.V. Manikandan, P. Senthil Kumaran, R.S. Sachin, M. Shetti, V.N. Influence of the support on the preferential oxidation of CO in hydrogen-rich steam reformates over the CuO-Ce02-Zr02 system. J. Catal. 2004, 221 (2), 455-465. 

In this study, we have synthesized Pt supported mesoporous carbons by carbonization of a mixture of neutral surfactants (P123), R complex and resorcinol resin. The eatalytic properties of this composite in selective oxidation of CO in hydrogen rich condition have been studied. 

For fuel-cell operation, most often technical hydrogen obtained by the conversion of primary fuels such as methanol or petroleum products is used, rather than pure hydrogen obtained by electrolysis. Technical hydrogen always contains carbon monoxide and a number of other impurities, even after an initial purification. In the first experiments conducted in the mid-1980s it was shown that traces of CO in hydrogen used for the operation of fuel cells with phosphoric acid electrolyte lead to a marked increase in the hydrogen electrodepolarization. 

Springer T, Zawodzinski T, Gottesfeld S (1997) Modelling of polymer electrolyte fuel cell performance with reformate feed streams effects of low levels of CO in hydrogen. The Electrochemical Society, Pennington... 

He, C Z., Kunz, H.R., Fenton, J.M. 2001. Selective oxidation of CO in hydrogen under fuel cell operation conditions. /. Electrochem. Soc. 148 A116-24. 

However, for some contaminants in the feeding gas, such as CO in hydrogen and NOj in air, the negative influence on the fuel cell is reversible when the contaminating gas is switched to pure reactant gas... 

Effective cleanup of CO in hydrogen by PROX over perovskite and mixed oxides. 

Sometimes my bad habit of assuming equilibrium gets me into trouble. A few years ago 1 was hired by a refinery in Lithuania to redesign their hydrogen production plant, to increase plant capacity by 25 percent, and to reduce the CO content of the hydrogen product. The COj content of the hydrogen was 2 percent, and the new specification was 0.5 percent CO in hydrogen product. 

---