Cyclohexanone oxime alumina

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... 

In conclusion, decrease in cyclohexanone oxime yield and caprolactam selectivity with time on stream is a major factor in the use of boria on alumina catalyst in the rearrangement reaction. Coke deposition and basic by-product adsorption have been suggested as a means of deactivation. In addition the conversion of water soluble boron, which is selective to lactam formation, to an amorphous water insoluble boron species is another factor that can account for the catalyst deactivation. 

A simple oxide catalyst can be used in either the bulk state or supported on an inert oxide support material. The bulk oxides are usually prepared using a precipitation-calcination sequence similar to those described in Chapter 9 for the preparation of support oxides. " In general, the simple semiconductor oxides are not very good catalysts for synthetic reactions. The insulator oxides, however, can be used as solid acids and bases for a number of reactions. Alumina has been used as an acid catalyst for the vapor phase rearrangement of cyclohexanone oxime to caprolactam (Eqn. 10.9). Modification of the y-alumina surface by the addition of 10-20% of B2O3 increased its activity for this reaction, giving caprolactam in 80% selectivity even after several hours of continuous operation. "... 

Aluminas modified by the addition of Cl , P04 , SO/ , Na, and B2O3 were used for the Beckmann rearrangement of cyclohexanone oxime [6]. Among the aluminas the B203-modified alumina was the best and that modified with Na the least suitable. B2O3 coupled with hydroxyapatite, Caio(P04)6(OH)2, was more selective than B2O3-AI2O3 and the enhanced selectivity was ascribed to the basicity of hydroxyapatite [7]. 

The rearrangement of oximes over solid acids has been studied for some time although the total number of studies has remained low. Zeolite and alumina based solid acids have been mostly studied and the substrate most often used has been cyclohexanone oxime, with a view to its transformation into caprolactam [1-15). A major problem associated with this reaction is coke formation and it appears with all catalyst types studied to date. The origin of coke formation have not been established, although there is a tendency to assume that it arises via a similar set of conditions to those which are responsible for coke formation in, for example, toluene disproportionation. 

Allied Chemical recently proposed a simplified technique, producing caprolactam from cyclohexanone, ammonia and oxygen in a single step, in the vapor phase, on a sffica or alumina-based catalyst However, the drawback of this process resides in the fact that only half of the oxime is converted in situ to caprolactam. This makes it necessary to resort to the Beckmann rearrangement For a 50 per cent conversion of cyclohexanone, the molar selectivity of oxime and caprolactam is 68 per cent Although this method considerably reduces the production of ammonium sulfate, the yields are still too low for it to appear to be more economical than the foregoing routes. 

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