Copper oxidation catalysts

Reforming is completed in a secondary reformer, where air is added both to elevate the temperature by partial combustion of the gas stream and to produce the 3 1 H2 N2 ratio downstream of the shift converter as is required for ammonia synthesis. The water gas shift converter then produces more H2 from carbon monoxide and water. A low temperature shift process using a zinc—chromium—copper oxide catalyst has replaced the earlier iron oxide-catalyzed high temperature system. The majority of the CO2 is then removed. 

In the second stage, a more active 2inc oxide—copper oxide catalyst is used. This higher catalytic activity permits operation at lower exit temperatures than the first-stage reactor, and the resulting product has as low as 0.2% carbon monoxide. For space velocities of 2000-4000 h , exit carbon monoxide... 

An ethyl acetate yield of 24% is obtained using a copper oxide catalyst with 0.1—0.2% thoria at 350°C. Dehydration. Ethyl alcohol can be dehydrated to form ethylene or ethyl ether. 

H.-H. Hildenbrand, and H.-G. Lintz, Solid electrolyte potentiometry aided study of the influence of promotors on the phase transitions in copper-oxide catalysts under working conditions, Catalysis Today 9, 153-160 (1991). 

GP 6] [R 5] With a stabilized CU2O catalyst layer, by addition of bromomethane (ppm level), 20% selectivity at 5% conversion was found (0.5 vol.-% propene 0.1 vol.-% oxygen 2.25 ppm promoter 350 °C) [37]. This is far better than with non-conditioned copper oxide catalysts which contain CuO besides CU2O. It is expected that the first species promotes more total oxidation, whereas the latter steers partial oxidation. In the above experiment, selectivity rises from 7 to 30% at slightly reduced conversion after 3 h of promoter conditioning. 

General Considerations. The following chemicals were commercially available and used as received 3,3,3-Triphenylpropionic acid (Acros), 1.0 M LiAlH4 in tetrahydrofuran (THF) (Aldrich), pyridinium dichromate (Acros), 2,6 di-tert-butylpyridine (Acros), dichlorodimethylsilane (Acros), tetraethyl orthosilicate (Aldrich), 3-aminopropyltrimethoxy silane (Aldrich), hexamethyldisilazane (Aldrich), tetrakis (diethylamino) titanium (Aldrich), trimethyl silyl chloride (Aldrich), terephthaloyl chloride (Acros), anhydrous toluene (Acros), and n-butyllithium in hexanes (Aldrich). Anhydrous ether, anhydrous THF, anhydrous dichloromethane, and anhydrous hexanes were obtained from a packed bed solvent purification system utilizing columns of copper oxide catalyst and alumina (ether, hexanes) or dual alumina columns (tetrahydrofuran, dichloromethane) (9). Tetramethylcyclopentadiene (Aldrich) was distilled over sodium metal prior to use. p-Aminophenyltrimethoxysilane (Gelest) was purified by recrystallization from methanol. Anhydrous methanol (Acros) was... 

Park PW, Ledford JS (1998) The influence of surface structure on the catalytic activity of cerium promoted copper oxide catalysts on alumina oxidation of carbon monoxide and methane. Catal Lett 50(1—2) 41 48... 

For on-board fuel processing, there are two principal concerns (1) the feasibility of keeping the iron-chrome and copper oxide catalysts in the reduced state, especially during periods of shutdown and (2) the pyrophoric nature of the copper oxide catalyst in the reduced state [29], Because of these concerns, considerable research and development is being conducted to develop new WGS catalysts for on-board fuel processing. 

M. M. Gunter, T. Ressler, R. E. lentoft, and B. Bems, Redox behavior of copper oxide catalysts in the steam reforming of methanol studied by in situ X-ray diffraction and absorption spectroscopy, J. Catal. 203, 133-149 (2001). 

Propene to acrolein. Hildenbrand and Lintz87,88 have used solid electrolyte potentiometry to study the effect of the phase composition of a copper oxide catalyst on the selectivity and yield of acrolein during the partial oxidation of propene in the temperature range of 420-510°C. Potentiometric techniques were used to determine the catalyst oxygen activity, and hence the stable copper phase, under working conditions. Hildenbrand and Lintz used kinetic measurements to confirm that the thermodynamically stable phase had been formed (it is known that propene is totally oxidised over CuO but partially oxidised over ). 

Phenol can also be prepared by the decomposition of benzoic acid prepared by the oxidation of toluene.927,978 The process is an oxidative decarboxylation catalyzed by copper(II). An interesting feature of this reaction is that the phenolic hydroxyl group enters into the position ortho to the carboxyl group as was proved by 14C labeling.979 In the Dow process980 molten benzoic acid is transformed with steam and air in the presence of Cu(II) and Mg(II) salts at 230-240°C. A copper oxide catalyst is used in a vapor-phase oxidation developed by Lummus.981... 

Oxidation of 2-Methylpropene over Copper Oxide Catalysts in the Presence of Selenium Dioxide... 

The air oxidation of 2-methylpropene to methacrolein was investigated at atmospheric pressure and temperatures ranging between 200° and 460°C. over pumice-supported copper oxide catalyst in the presence of selenium dioxide in an integral isothermal flow reactor. The reaction products were analyzed quantitatively by gas chromatography, and the effects of several process variables on conversion and yield were determined. The experimental results are explained by the electron theory of catalysis on semiconductors, and a reaction mechanism is proposed. It is postulated that while at low selenium-copper ratios, the rate-determining step in the oxidation of 2-methylpropene to methacrolein is a p-type, it is n-type at higher ratios. 

This paper reports the effect of various amounts of selenium dioxide under different operating conditions on the conversion of 2-methylpropene to methacrolein and proposes a hypothesis for the hydrocarbon oxidation, which explains particularly the reactivity and selectivity of selenium-copper oxide catalysts in oxidizing 2-methylpropene. 

The pumice-supported copper oxide catalyst containing 16 weight % of copper was prepared by impregnating 20 to 40-mesh crushed ptimice stone with a copper nitrate solution and drying it at 105°C. for 6 hours The dried catalyst was subsequently calcined at 600°C. for 6 hours and placed in the reactor. The catalyst was activated by passing air over it for 12 hours before any experimental run was made. 

Extending the definition of n-type and p-type reactions, as defined by Vol kenshtein (21) to the electron transfer step, it would seem that the only reaction given by Equation 1 is a p-type reaction. This reaction would be accelerated by the increase in the value of free hole concentration. On the other hand, all other reactions besides the one given by Equation 1 are n-type and would be accelerated by the increase in free electron concentration. Hydrocarbon oxidation reactions catalyzed by solid oxides are accompanied by oxidation and reduction of the catalyst and the degree of the stoichiometric disturbance in the semiconductor changes. The catalytic process in the oxidation of 2-methylpropene over copper oxide catalyst in the presence of Se02 can be visualized as ... 

A certain amount of selenium may be considered as an acceptor impurity to copper oxide since the Fermi level of copper oxide catalyst is lowered or its p-typeness is increased. This agrees with the observation of Margolis (16). 

Decomposition of NzO on a copper oxide catalyst in adiabatic circulating reactor Hugo (46) X ... 

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. 

Shore, L., Ruettinger, W.F., and Farrauto, R.J. Platinum group metal promoted copper oxidation catalysts and methods for carbon monoxide remediation. United States Patent Application... 

Fig. 7. Experimental propylene oxidation activity vs. catalyst oxidation state-copper oxide catalyst. Reaction temperature = 300°C. From (6). 

Preparation of copper-oxide catalyst systems for hydrogenation... 

In this work, we investigate the preparation of copper-oxide catalyst system for hydrogenation, particularly CO hydrogenation for methanol production. We report the relations between the condition and morphology of the catalyst originated from the preparation condition of the catalyst and the catalytic activity for CO hydrogenation as well as the catalytic activity of various oxide contained copper. 

Two kinds of catalyst precursors were mainly employed in this work. One was the mixed oxide of Cu60sLn(N03), prepared by pyrolysis of the mixture of corresponding nitrates under O2 flow at 673 K, referred to in previous reports [7,11,12], The other was the homogeneous mixture of the corresponding oxides, which was prepared by calcination of the hydroxide coprecipitate, obtained by the hydrolysis of the mixed nitrate solution added with NaaCOs solution (0.05 mol/1) and washing the obtained coprecipitates with distilled water several times until the pH of the supernatant solution was dropped to 7, at prescribed temperature. The copper-oxide catalyst systems were obtained by the reduction of the prepared precursors under H2 (300 Torr 1 Torr=l33.32 Pa) at prescribed temperatures before the reaction. 

It is concluded that copper-oxide catalyst system, particularly copper-lanthanide oxide catalyst system, show a high activity for CO hydrogenation. The effective condition of the catalyst is the homogeneous mixture of copper and oxide where a fine particle of the oxide dispersed homogeneously in the copper metal and the active eatalyst can be prepared from the mixed oxide of CueOgLnfNOj) and the homogeneous oxide mixture obtained from the calcination of the hydroxide coprecipitate. If the combined oxides were changed. 

Preparation of copper-oxide catalyst systems for hydrogenation Y. Sakata, N. Kouda, Y. Sakata and H. Imamura... 

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