Mordenite dual function catalysts based

The application of zeolitic materials cls catalysts in paraffin isomerization is discussed. Particular attention is given to catalyst preparation variables such as sodium removal for zeolite Y and mordenite. Dual function catalysts based on these zeolites are compared with respect to activity. A reaction mechanism for paraffin isomerization over zeolitic dual function catalysts, on the basis of literature and own data, is presented. 

Preparation of Dual Function Catalysts Based on Zeolite Y and Mordenite... 

It has been claimed that noble metal dual function catalysts based on H-mordenite are more active for paraffin isomerization than their counterparts based on H-zeolite Y (25). For both zeolites the isomerization activity depends strongly on the degree of sodium removal and comparison of low sodium Pd-H-mordenite and low sodium Pd-H-zeolite Y for isomerization of n-hexane at 250° C shows that both materials have about the same activity (Table IV), the Y sieve based material being slightly more active. 

Paraffin isomerization over dual function catalysts based on zeolite Y and mordenite has been reviewedand a reaction mechanism was proposed in which olefin-paraffin equilibrium is established and carbonium ions are formed from both paraffins and olefins. The isomerization of n-hexane and hydrocrack-... 

In the reaction mechanisms described above the acidity of the catalyst plays an important role. Zeolites can be converted into the H+ form and as such are powerful catalysts for acid-catalyzed reactions. We discuss below some aspects of isomerization catalyst preparation to demonstrate factors which influence the activity of catalysts based on zeolites. In this discussion we are concerned with zeolite Y and mordenite. Data on paraffin isomerization over dual function catalysts besed on other zeolites are scarce, and no data have been published showing that materials like zeolite X, zeolite L, offretite, zeolite omega, or gmelinite can be converted into catalyst bases having an isomerization activity comparable with that of H-zeolite Y or H-mordenite. 

For optimal performance of dual function isomerization catalysts based on zeolite Y or mordenite, extensive removal of sodium is necessary. The finished catalyst must be highly crystalline, and the finely dispersed metallic hydrogenation function should be well distributed throughout the catalyst particles. The proposed mechanism explains the stabilizing influence on conversion and the suppression of cracking reactions by addition of the metallic hydrogenation function to the active acidic catalyst base. 

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