Catalyst cyclohexane, hydrogenation

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

To hydrogenate an aromatic ring, it s necessary either to use a platinum catalyst with hydrogen gas at several hundred atmospheres pressure or to use a more effective catalyst such as rhodium on carbon. Under these conditions, aromatic rings are converted into cyclohexanes. For example, o-xylene yields 1,2-dimethylcvclohexane, and 4-terf-butylphenol gives 4-terf-butyl-cyclohexanol. 

Vesicle-entrapped or isolated Pt were used as 564 catalysts for ethylene and cyclohexane hydrogenation... 

The role of the support was also demonstrated in the competitive hydrogenation of cyclohexene and cyclohexanone in water-cyclohexane mixtures52. Cyclohexene was exclusively hydrogenated on a hydrophobic Rh—C, since this catalyst is covered by a cyclohexane layer, which preferentially dissolves cyclohexene. On a hydrophilic Rh-silica cyclohexanone, present mainly in the water phase covering the catalyst, was hydrogenated. 

This catalyst (1) is a selective catalyst for hydrogenation of 4-octyne to cw-4-octene (90% yield). If the product is left in contact with 1, it isomerizes to the trans-isomer. Since monoalkenes are hydrogenated slowly with this catalyst, cyclo-octene can be obtained from either 1,3- or 1,5-cyclooctadiene. Of more interest, benzene can be hydrogenated to cyclohexane (83% yield). One drawback is that the catalyst loses about 90% of its activity after one cycle. 

It is seen from Table III that the elements known as catalysts of dehydrogenation of cyclohexane and its derivatives include, in fact, only metals with lattices of the types AI and M3 and with d s lying within the limits from 2.7746 A (Pt) to 2.4916 A (Ni). These elements are framed in Table III. It is evident that this requirement of the theory is completely met. Table III shows why the metals Ni, Co, Cr, Rh, Ir, Pd, Pt, Ru, Os, and Re belong to the group of catalysts of hydrogenation and dehydrogenation of six-membered cyclic hydrocarbons and the metals, Ca, Ce, and Fe, for example, do not. 

Rh/Si02 Pt/Ti02 Catalyst preparation Hydrogenation Cyclohexane/n-alcohol Octane NP-5,7.5,10,15/ CTAB/CTAC/ AOT RhC aq 1.8-6 113 85... 

We find that the pentamethylcyclopentadienyl-rhodium compounds, and particularly the chloride (la), are useful catalysts for arene hydrogenation at 50°C and 50 atm H2 (19), Again, base (Et3N) is a necessary co-catalyst and the reactions proceed well in 2-propanol as solvent, where turnover numbers in excess of 200 per rhodium can easily be obtained for benzene-to-cyclohexane hydrogenation. The reactions also proceed in benzene, where turnover numbers in excess of 800 per rhodium are found, and even in the presence of water. No metal is formed under these conditions. 

C24K is a moderately active catalyst for hydrogenation of alkenes. It is a very efficient catalyst for isomerization of cw-stilbene to trcnj-stilbene. It is also effective for isomerization of alkynes 2-octyne-> 1-octyne (86% yield). An allene is a probable intermediate 2-decyne -> 1-decyne (207o) and 1,2-decadiene (9%,). Potassium alone also effects these isomerizations, but only at higher temperatures. Benzene is slowly converted into biphenyl when in contact with C24K in refluxing cyclohexane. This reaction has also been reported for CgK in DMF at 20 (61%, yield).=... 

Pande, J. V., Shukla, A., Biniwale, R. B. (2012). Catalytic dehydrogenation of cyclohexane over Ag-M/ACC catalysts for hydrogen supply. International Journal of Hydrogen Energy, 37, 6756—6763. 

Aqueous colloidal solutions of Ru/PTA and Pt/PTA NPs were involved as catalysts in hydrogenation of model olefins and aromatic substrates. These nanocatalysts appeared active in mild conditions. For example, octene and dodecene were fully converted into the corresponding alkanes (r.t. 1 bar H2) with moderate activities. An increase in the hydrogen pressure = lObar) was not detrimental for the stability of the colloidal suspension. The complete hydrogenation of toluene into cyclohexane was observed overnight with Ru/PTA, whereas 60% of m-methoxymethylcyclohexane was formed from methoxymethylanisole. Nevertheless, preliminary recycling tests showed that an improvement of the stability and recovery of these materials was necessary to increase their interest in catalysis. 

C, b.p. 81"C. Manufactured by the reduction of benzene with hydrogen in the presence of a nickel catalyst and recovered from natural gase.s. It is inflammable. Used as an intermediate in the preparation of nylon [6] and [66] via caprolactam and as a solvent for oils, fats and waxes, and also as a paint remover. For stereochemistry of cyclohexane see conformation. U.S. production 1980 1 megatonne. 

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