Mesoporous Beckmann rearrangement

Zeolites and other mesoporous materials are excellent catalysts for industrial and laboratory applications. Favourable characteristics are their capacity to immobihze homogenous catalysts rendering them heterogeneous, their thermal stability, and the ease of separation from the reaction products and reuse in hquid- and gas-phase conditions. The pore size and Brpnsted and Lewis acidic properties are determinant for their use as catalyst in the Beckmann rearrangement. Recently, a review on the use of zeolites and mesoporous materials in the Beckmann rearrangement was published. ... 

The Beckmann rearrangement of cyclohexanone oxime in the gas phase has been investigated over siliceous MCM-41- and MCM-48-type materials. At 275°C complete conversion occurs for several hours with selectivities for s-caprolactam up to 65 %, until the catalysts deactivate rapidly. The deactivation of the mesoporous catalysts is considerably reduced as compared to that obtained over an amorphous silica gel. MCM-48 exhibits the highest catalyst lifetime which, for MCM-41-type materials, is longer with larger pore diameter. With an aluminum-containing H-MCM-41 catalyst an increased e-caprolactam selectivity is achieved. 

ITQ-2 zeolite prepared by delamination of MCM-22 precursor, is formed by disordered individual sheets of crystalline zeolitic layers in where the Bronsted acid sites are of zeolitic nature and the vast majority of them aecessible to large molecules. The delaminated zeolite combines the acid characteristic of microporous zeolites with accessibility of the sites of mesoporous Al/MCM-41 and amorphous silica-alumina. The superior catalytic performance of delaminated zeolites compared to conventional zeolites and Al/MCM- 1 is examplified for reactions involving large reactant molecules, namely the preparation of dimethyl acetals, the Beckmann rearrangement of bulky cycloalkanone oximes and hydroxylation of aromatics. 

Beckmann rearrangement of cyclohexanone oxime over mesoporous MCM-41 and MCM-48 type materials... 

Shouro, D., Moriya, Y, Nakajima, T., and Mishima, S. 2000. Mesoporous silica ESM-16 catalysts modified with various oxides for the vapor-phase Beckmann rearrangement of cyclohexanone oxime. App/. Catal. A.- Gen. 198 275-282. 

Mesoporous silica FSM-16 catalysts modified with various oxides were used in the vapor-phase Beckmann rearrangement of The selective formation of the lactam 6 was improved by using FSM-16 supported by AI2O3, ZnO and CdO. 

The liquid phase Beckmann rearrangement of cyclohexanone oxime 5 in the presence of a series of mesoporous molecular sieves with various Si02/Al203 ratios has been reported. The surface silanol groups ineffectively catalyzed the rearrangement, whereas the acid sites generated by incorporation of aluminium improved the activity and selectivity to lactam 6. 

Flego, C. and Dalloro, L. (2003). Beckmann Rearrangement of Cyclohexanone Oxime over Silicalite-1 An FT-IR Spectroscopic Study, Micropor. Mesopor. Mat., 60, pp. 263-271. 

B. Thomas, S. Prathapan, S. Sugunan, Beckmann rearrangement of E,E-dnnamaldoxime on rare earth exchanged (Ce3+, La3+, and RE3+) HFAU-Y zeoKtes an efficient green pwocess for the synthesis of isoquinohne, Microporous Mesoporous Mater. 84 (2005) 137-143. 

Thomas, B. Sugunan, S. Rare-earth (Ce, La, Sm, and RE ) exchanged Na-Y zeolites and K-10 clay as solid acid catalysts for the synthesis of benzoxazole via Beckmann rearrangement of salicylaldoxime. Micropor. Mesopor. Mater. 2006, 96, 55-64. 

Crosslinked TS-1 zeohte materials are among the best catalysts for the gas-phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam [156]. Crosshnking of the zeolite particles resulted in the additional mesoporosity and as a result, in an increased activity in the title reaction. Note that the deactivation of the catalysts is significantly decreased. The increased activity correlates with the newly created mesopore surface area. 

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