Iron-copper-alkali catalyst

Medium-pressure synthesis with iron catalysts. Up to January, 1935, the maximum yields of C5+ hydrocarbons obtained with iron catalysts at atmospheric pressure were 30-40 g./m.3 synthesis gas. The decline of catalyst activity amounted to 20% within 8 days (19). Fischer and Meyer (20) improved the yields of the normal-pressure synthesis with iron catalysts (in 1934-1936) to 50-60 g./m.3 synthesis gas and the lifetime of the catalyst from 8 days to about 30 days. These results were obtained with iron-copper precipitation catalysts (1 atm., 230-240°C.). The decline of catalyst activity was closely connected with changes of the composition of the reaction products. The color of the synthetic products changed from white to yellow and formation of fatty acids and organic iron salts was detected. Increased carbon monoxide content of the synthesis gas and increased alkali content of the catalyst accelerated this phenomenon. 

O Brien, R.J., and Davis, B.H. 2004. Impact of copper on an alkali promoted iron Fischer-Tropsch catalyst. Catal. Lett. 94 1-6. 

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). 

The catalyst is typically iron, which is promoted by dre addition of copper, Si02 and an alkali oxide, usually K2O. The catalyst can be prepared by... 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Following the development of sponge-metal nickel catalysts by alkali leaching of Ni-Al alloys by Raney, other alloy systems were considered. These include iron [4], cobalt [5], copper [6], platinum [7], ruthenium [8], and palladium [9]. Small amounts of a third metal such as chromium [10], molybdenum [11], or zinc [12] have been added to the binary alloy to promote catalyst activity. The two most common skeletal metal catalysts currently in use are nickel and copper in unpromoted or promoted forms. Skeletal copper is less active and more selective than skeletal nickel in hydrogenation reactions. It also finds use in the selective hydrolysis of nitriles [13]. This chapter is therefore mainly concerned with the preparation, properties and applications of promoted and unpromoted skeletal nickel and skeletal copper catalysts which are produced by the selective leaching of aluminum from binary or ternary alloys. 

The possible surface contaminations were carefully followed by Auger-XPS analysis. Similarly, as with the copper catalyst described earlier (Section III) the Cu/ZnO binaries were free from alkali metals, iron, chlorine, and sulfur, and contained only small amounts of carbon after the use in catalytic reactor (39). The latter result indicates that reactants, intermediates, and the product are adsorbed with moderate strength, a feature that is desirable for all efficient catalysts. 

The addition of copper to iron catalysts leads to an increased rate of reduction which can thus be carried out ai lower temperatures [15. ) ). 2t). If no copper is added, the degree of reduction is very low and the activity of the catalyst is inferior. Uven if the catalyst is reduced at higher temperatures to obtain the same degree of reduction, as in the presence of copper, a poorer catalyst activity is found. The hydrogenation activity of iron catalysts is strongly influenced by addition of electronic promoters like KjOor other alkali metals [181. Their elTiciency depends on the basicity and the following order is found [-MS]. 

Irreversible catalyst poisons (or deposits) can even influence the catalyst during the first passage through the reactor, but are not (easily) removed during the stripping and/or regeneration stages. Examples are the heavy metals in feed as vanadium and nickel and other poisons such as alkali components, iron and copper. 

Manufacture of many important amino intermediates used for dyes and other purposes is usually by conversion or replacement of a substituent. For example, as already mentioned, in substituted nitro compounds, the nitro groups may be reduced with iron/hydrochloric acid, hydrogen and catalyst, or zinc in aqueous alkali. Partial reductions can be brought about with sodium sulfide. Amino groups may be introduced by replacing halogens in the aromatic ring. Another approach to amination is by attack on a substituted aromatic compound with ammonia or amines. Thus, for example, direct amination of p-chloronitrobenzene (15a) in the presence of a copper catalyst affords p-nitroaniline (15b) in almost quantitative yield l,4-dichloro-2-nitrobenzene (16) is converted in a similar way to 4-chloro-2-nitroaniline (17). Reactions of ammonia with carboxylic acids or anhydrides are carried out on an industrial scale. 

The catalysts which were found to lie effective in the formation of methane from hydrogen and cavlion monoxide with the greatest activity were composed of nickel, iron, cobalt, and molybdenum. The catalysts most active in methanol synthesis in general consists of the oxides or mixtures of the oxides of zinc, copper, or chromium. Iron promoted with alkali lias been found to be very active but not at all directive in the synthesis of aliphatic compounds from water-gas. With it only a very complex mixture results, which it is impossible to separate commercially into constituents. 

The best catalyst was found to consist of zinc oxide and copper (or copper oxide) with an admixture of compounds of chromium. The success of the operation depended upon (a) the absence of alkali, which would cause decomposition of the methanol and the production of higher alcohols and oily products, and (b) the complete elimination of all metals except copper, aluminum and tin from those parts of the apparatus which come in contact with the reacting gases. Contact of carbon monoxide with iron, nickel, or cobalt had to be avoided since they formed volatile carbonyls winch deposited metal, by decomposition, on the active catalyst surface and thereby acted as poisons to destroy activity. 

ISOCIANATO de METILO (Spanish) (624-83-9) Forms explosive mixture with air (flash point 0°F/- 18°C). Reacts slowly with water violently with warm water or steam, forming carbon dioxide and heat. Decomposes above 100°F/38 C. Violent reaction with acetaldehyde, amines, alcohols, acids, alkalis, strong oxidizers. Unless inhibited, can produce unstable peroxides contact with iron, tin, copper, or salts of these elements, or with certain catalysts such as triphenylarsenic oxide, triethylphosphine, or tributyltin oxide, or elevated temperatures may cause polymerization. Incompatible with glycols, amides, ammonia, caprolactam. Attacks some plastics, rubber, or coatings. The uninhibited monomer vapor may block vents and confined spaces by forming a solid polymer material. 

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