Hydrogen activating copper

A flow diagram for the system is shown in Figure 5. Feed gas is dried, and ammonia and sulfur compounds are removed to prevent the irreversible buildup of insoluble salts in the system. Water and soHds formed by trace ammonia and sulfur compounds are removed in the solvent maintenance section (96). The pretreated carbon monoxide feed gas enters the absorber where it is selectively absorbed by a countercurrent flow of solvent to form a carbon monoxide complex with the active copper salt. The carbon monoxide-rich solution flows from the bottom of the absorber to a flash vessel where physically absorbed gas species such as hydrogen, nitrogen, and methane are removed. The solution is then sent to the stripper where the carbon monoxide is released from the complex by heating and pressure reduction to about 0.15 MPa (1.5 atm). The solvent is stripped of residual carbon monoxide, heat-exchanged with the stripper feed, and pumped to the top of the absorber to complete the cycle. 

On sintering the surface activity progressively becomes less as is indicated by the following data on the adsorption of hydrogen by copper and nickel obtained by Beebe and Taylor J.A.O.S. XLVI. 43, 1924). 

The activation energy for adsorption of hydrogen on copper was set at 30 kJ mol-1, in agreement with the literature (80). A sticking coefficient of unity was assumed for this step. Furthermore, the entropy of the adsorbed surface hydrogen was adjusted in the analysis. 

Other Raney catalysts have been prepared. Raney cobalt has been described by several authors (28,29). The active cobalt has been claimed to be especially suitable for the reduction of nitriles. The preparation of an active copper has been described by Faucounau (30). Paul and Hilly (31) have described the preparation of Raney iron. It is claimed that Raney iron reduces acetylenic bonds to ethylenic bonds with no further hydrogenation occurring. 

The hydrogenation of an unsaturated ester to an unsaturated alcohol may be possible over zinc-chromium oxide as catalyst, although the catalyst is known to be much less active for the usual ester hydrogenations than copper-chromium oxide. Ethyl or butyl (eq. 10.25) oleates were hydrogenated to octadecenol in yields of over 60% with a zinc-chromium oxide at 280-300°C and 20 MPa H2.16 The butyl ester was much preferred to the ethyl ester, since it was difficult to separate the ethyl ester from the alcohol product because of their similar boiling points. 

Conversion of furfural to 2-methylfuran was achieved in 90-95% yields by vapor-phase hydrogenation over copper-chromium-barium oxide dispersed on activated charcoal at 1 atm H2 and 200-230°C (eq. 12.104).204... 

The reaction of an isocyanide containing an acidic hydrogen with copper(I) oxide and an activated olefin or a ketone [Eq. (123)] provides a synthesis of either pyrrolines or oxazolines, respectively (251,252). Addition of allyl bromide gave the coupling product with the allyl carbanion derived from allyl isocyanide. Oxazolines are obtained in yields as high as 957o> not pyrrolines because of competing dimerization... 

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]. 

The nse of polysnlfide complexes in catalysis has been discnssed. Two major classes of reactions are apparent (1) hydrogen activation and (2) electron transfers. For example, [CpMo(S)(SH)]2 catalyzes the conversion of nitrobenzene to aniline at room temperature, while (CpMo(S))2S2CH2 catalyzes a number of reactions snch as the conversion of bromoethylbenzene to ethylbenzene and the rednction of acetyl chloride, as well as the rednction of alkynes to the corresponding cw-alkenes. Electron transfer reactions see Electron Transfer in Coordination Compounds) have been studied because of their relevance to biological processes (in, for example, ferrodoxins), and these cluster compounds are dealt with in Iron-Sulfur Proteins. Other studies include the use of metal polysulfide complexes as catalysts for the photolytic reduction of water by THF and copper compounds for the hydration of acetylene to acetaldehyde. ... 

Results indicate that deposition is facilitated on active (copper, NijCr) compared to inert substrates. This is attributed to an easier decomposition of the precursor on copper or NijCr rather than on glass or carbon surfaces. Hydrogen can be dissociatively adsorbed on NijCr substrates enhancing the decomposition of NiCp. On copper substrates, the dissociative adsorption of hydrogen is not easy. In that case, the enhanced nucleation is certainly due to the... 

Finely divided copper has been used as a reducing agent for Fe(III). Activated copper,prepared by reducing copper(II) oxide with hydrogen, has been used to displace cadmium but not zinc from a cyanide solution. In cyanide solution, copper is a strong reducing agent (.F° = —1.09 V). Its formal potential hes between those of zinc (—1.26 V) and cadmium (—0.90 V) and several heavy metals (Pb, Bi, Sn, Ag, Hg) are displaced from solution. 

Povidone is manufactured by the Reppe process. Acetylene and formaldehyde are reacted in the presence of a highly active copper acetylide catalyst to form butynediol, which is hydrogenated to butanediol and then cyclodehydrogenated to form butyrolactone. Pyrrolidone is produced by reacting butyrolac-tone with ammonia. This is followed by a vinylation reaction in which pyrrolidone and acetylene are reacted under pressure. The monomer, vinylpyrrolidone, is then polymerized in the presence of a combination of catalysts to produce povidone. 

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