Copper alumina catalyst

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... 

In situ dynamic surface structural changes of catalyst particles in response to variations in gas environments were examined by ETEM by Gai et al. (78,97). In studies of copper catalysts on alumina, which are of interest for the water gas shift reaction, bulk diffusion of metal particles through the support in oxygen atmospheres was shown (78). The discovery of this new catalyst diffusion process required a radical revision of the understanding of regeneration processes in catalysis. 

Alkylphenanthridines (and 6-aryl) have been obtained by passing a mixture of 2-nitrobiphenyl and the appropriate alcohol over a copper-alumina catalyst at 320-360°.59... 

The catalytic reaction of steam with methane at elevated temperatures (300-400 + C) over various catalysts copper or nickel/molybde-num oxide/alumina—can be made to yield CO and H2 in desired ratios. The generalized reaction for hydrocarbons with steam is ... 

Several of the early oxide studies have already been mentioned in the introduction. The copper-alumina oxidation catalyst, which finds applications for the synthesis of glyoxal from glycol and as the principal component of base-metal formulations for automobile exhaust emission control, has... 

The metallic function and the acid-base properties of the catalysts used, play a central role in the reforming reaction of ethanol. This is illustrated by the Cu/Ni/K/y-AUCU catalyst, which exhibits acceptable activity, stability and hydrogen selectivity at relatively low temperature (573 K) and at atmospheric pressure.171 In this catalyst, copper is the active agent, nickel promotes C-C bond rupture and increases hydrogen selectivity, and potassium neutralises the acidic sites of the 7-alumina substrate and improves the general performance of the catalyst. 

In such situation, when copper is deposited on these supports one may expect the presence of at least three kinds of copper entities differing in their interactions with the underlying support and which may be designated as copper-alumina, copper-2D-Ce and copper-3D-Ce. The chemical behaviour of the first and the last of these entities can be assumed in principle to be close to that of copper supported on the pure supports. For the calcined samples, in the case of the CuA catalyst two different Cu entities have been identified on the EPR spectra differing in their dispersion degree, with a fraction of Cu remaining undetected. On CuC, the observable species is clearly different from those... 

An extensive literature exists on the characterization and structure—activity correlation of industrial copper-alumina oxychlorination catalysts [95-120]. At least two different major copper species have been identified. At low concentrations of copper (below ca 5 %), a well-dispersed copper species in intimate interaction with the alumina surface is formed. This species has a very low oxychlorination activity. At higher concentrations, a second species, probably formed by the de-position/precipitation of the copper chloro complexes, is observed. The latter gives rise to the active sites during the oxychlorination reaction. On the basis of an FTIR study of the oxychlorination reaction Finocchio et al. [42] postulated the formation of surface copper chloride-ethylene r-complex intermediates (which lead eventually to EDC) and weakly adsorbed HCl during oxychlorination. Formate species associated with copper and probable precursors for formation of the oxides of carbon by combustion were also identified. 

Single-bed catalysts had been used to produce sulfur from dry sulfur dioxide gases. Ryason 1,2) used either Cu, Pd, Ag, Co, or Ni supported on alumina. Khalafalla and Haas (3) optimized the composition of iron-alumina catalysts to produce sulfur from dry gases containing sulfur dioxide and carbon monoxide. Querido and Short (4) demonstrated the feasibility of reducing sulfur dioxide by carbon monoxide on a copper-alumina catalyst at concentrations and temperatures typical of power plant stack gases. 

Recently Okay and Short (5) reported that the sulfur dioxide reduction activity of the single-bed copper-alumina catalyst was reduced when water was added to an inlet gas containing 0.2% sulfur dioxide. Neither hydrogen nor hydrogen sulfide was detected in their experiments although thermodynamic calculations indicate that these gases could form at detectable concentrations. 

The disparity between these results and those reported by Okay and Short (5) on a copper-alumina catalyst can best be explained in the... 

A few measurements of catalytic activity have been made on the reduced copper-alumina system. Comparison of catalysts containing varying proportions of copper was made as usual by mechanically mixing all samples, except the lowest in copper, with 7-alumina so that all samples contained 3.2 per cent copper. The catalytic measurements were not extended below that concentration. The reaction chosen was the dehydrogenation of isopropyl alcohol. 

Relative Catalytic Activity of Copper-Alumina Catalyeis Acetone High-boiling Catalyst % %... 

THERMOSTABILITY OF COPPER-CHROMIUM OXIDE CATALYSTS ON ALUMINA SUPPORT PROMOTED BY LANTHANUM AND CERIUM. 

The catalytic carbon monoxide clean-up worked with a two-stage water-gas shift in tubular reactors cooled by steam generation. The kinetics for a rhenium-alumina catalyst for high temperature water-gas shift and for a copper/alumina catalyst for low temperature shift had been extracted from the literature. 

It has been concluded from experimental work with catalysts containing alumina that methanol forms from carbon dioxide and that the catalyst activity is proportional to the copper metal surface area. The presence of carbon dioxide in the gas increases the synthesis rate. The zinc oxide and alumina play little part in the actual reaction apart from stabihzing the reduced copper and protecting it from the effect of any poisons. On the other hand, with catalysts containing chromia, the carbon dioxide leads to a decrease in the reaction rate. ... 

Iron-based catalysts are used in both LTFT and HTFT process mode. Precipitated iron catalysts, used in fixed-bed or slurry reactors for the production of waxes, are prepared by precipitation and have a high surface area. A sihca support is commonly used with added alumina to prevent sintering. HTFT catalysts for fluidized bed apphcations must be more resistant to attrition. Fused iron catalysts, prepared by fusion, satisfy this requirement (Olah and Molnar, 2003). For both types of iron-based catalysts, the basicity of the surface is of vital importance. The probability of chain growth increases with alkali promotion in the order Li, Na, K, and Rb (Dry, 2002), as alkalis tend to increase the strength of CO chemisorption and enhance its decomposition to C and O atoms. Due to the high price o Rb, K is used in practice as a promoter for iron catalysts. Copper is also typically added to enhance the reduction of iron oxide to metallic iron during the catalyst pretreatment step (Adesina, 1996). Under steady state FT conditions, the Fe catalyst consists of a mixture of iron carbides and reoxidized Fe304 phase, active for the WGS reaction (Adesina, 1996 Davis, 2003). 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

This reaction is first conducted on a chromium-promoted iron oxide catalyst in the high temperature shift (HTS) reactor at about 370°C at the inlet. This catalyst is usually in the form of 6 x 6-mm or 9.5 x 9.5-mm tablets, SV about 4000 h . Converted gases are cooled outside of the HTS by producing steam or heating boiler feed water and are sent to the low temperature shift (LTS) converter at about 200—215°C to complete the water gas shift reaction. The LTS catalyst is a copper—zinc oxide catalyst supported on alumina. CO content of the effluent gas is usually 0.1—0.25% on a dry gas basis and has a 14°C approach to equihbrium, ie, an equihbrium temperature 14°C higher than actual, and SV about 4000 h . Operating at as low a temperature as possible is advantageous because of the more favorable equihbrium constants. The product gas from this section contains about 77% H2, 18% CO2, 0.30% CO, and 4.7% CH. ... 

Because the synthesis reactions are exothermic with a net decrease in molar volume, equiUbrium conversions of the carbon oxides to methanol by reactions 1 and 2 are favored by high pressure and low temperature, as shown for the indicated reformed natural gas composition in Figure 1. The mechanism of methanol synthesis on the copper—zinc—alumina catalyst was elucidated as recentiy as 1990 (7). For a pure H2—CO mixture, carbon monoxide is adsorbed on the copper surface where it is hydrogenated to methanol. When CO2 is added to the reacting mixture, the copper surface becomes partially covered by adsorbed oxygen by the reaction C02 CO + O (ads). This results in a change in mechanism where CO reacts with the adsorbed oxygen to form CO2, which becomes the primary source of carbon for methanol. 

The zinc oxide component of the catalyst serves to maintain the activity and surface area of the copper sites, and additionally helps to reduce light ends by-product formation. Selectivity is better than 99%, with typical impurities being ethers, esters, aldehydes, ketones, higher alcohols, and waxes. The alumina portion of the catalyst primarily serves as a support. 

Miscellaneous Reactions. Ahyl alcohol can be isomerized to propionaldehyde [123-38-6] in the presence of sohd acid catalyst at 200—300°C. When copper or alumina is used as the catalyst, only propionaldehyde is obtained, because of intramolecular hydrogen transfer. On the other hand, acrolein and hydrogen are produced by a zinc oxide catalyst. In this case, it is considered that propionaldehyde is obtained mainly by intermolecular hydrogen transfer between ahyl alcohol and acrolein (31). 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

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