Zeolite omega preparation

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. 

A study is presented of the synthesis and properties of the novel synthetic zeolite omega. The synthesis variables and kinetics of formation are discussed, as well as the ion exchange, sorption, and thermal properties. By decomposition of imbibed tetra-methylammonium ions and exhaustive treatments of the zeolite with ammonium ions, a pure hydrogen form can be obtained which is a suitable substrate for the preparation of hydrocarbon conversion catalysts. Several catalysts were prepared and utilized to isomerize n-hexane, and to hydrocrack a heavy gas oil. 

This speculation was not only completely vindicated in the preparation of silica-rich forms of a variety of known zeolites (2, 3) it was found that direct use of organic cations in syntheses promoted unusual structural designs which led to novel zeolites. Zeolite omega (S2) was one such material and was first synthesized by Flanigen and Kellberg (4) These... 

Table VI. Preparation, Properties, and Activity for n-C6 Isomerization of Catalysts Based on Zeolite Omega...

Freshly prepared Na+-TMA+-omega zeolite has a very small ultimate crystallite size, as indicated by line broadening in x-ray powder diffraction patterns and microscope studies. 

Preparation of Catalysts. A large amount of pure omega was prepared as described above. Platinum and palladium catalysts were made from this material by slurrying variously pretreated forms with aqueous solutions of Pt and Pd(NH3)4Cl2 of appropriate concentrations. Zeolites thus obtained were dried and calcined to a final temperature of 500° C. 

Before going on to list these families, one further point needs to be made. This arises because there are several instances where a unique zeolite framework has been first characterized from a laboratory preparation and later identified as a natural species. The first of these was mazzite, prepared first as synthetic zeolite ZSM-4 (or omega) but known in naMe prior to the allocation of the lUPAC code hence its inclusion in Table 7. The other species have been discovered in naMe after an lUPAC code had been allocated to their synthetic analogs. The details for these materials are given in Table 8. 

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