Zeolite admixing

Operationally, the basic difference between the Type X and Type Y structures was largely a matter of thermal stability, although acid strength-related differences in selectivity were also found. While the Type Y zeolite was much more stable, it was also much more expensive. Davison initially marketed their XZ-15 catalyst, containing steam-stabilized Y zeolite admixed with low-alumina silica-alumina, at a price of 800 per ton. This was quite a high price at the time, but despite that, about 15 refiners tried it. At the same time, Filtrol introduced their Grade 800 catalyst, and although they didn t officially claim that it contained molecular sieves, the product distributions clearly pointed to their presence (67). 

The moat favourable pH range lies between 9 and 11. Other oxides containing the main part of Qe co-precipitate with the HFI-type zeolitea in neutral or acidic medium. In a very alkaline madium, the formation of soluble germanatea restricts the incorporation of germanium in the zeolite. Moreover if the pH is adjusted with alkali or ammonium hydroxide, the corresponding germanates admix with an almoet purely silioeous HFI-type zeolite. These difficulties oan be... 

Pentasil type zeolite catalysts are synthesized and modified similar to the procedures in (ref. 2), but some of them were admixed with suitable binding material. Acidity was characterized by NH -TPD and IR spectra and surface property by ESCA as in (refs.2-3). Catalytic reaction was carried out in continuous flowtype systems with 2-30 g and more of catalyst and regeneration by oxidation at about 530°C. 

In these systems zeolite ZSM-48 does not form if HM " ions are absent (samples 5 and 6) or if their relative concentration is low (sample 4). Under such conditions the reaction leads to the formation of ZSM-5, probably because the formation of 5-1 SBU is favoured in a high-silica hydrogel containing both Al and Na" " [13,24,25]. The presence of a-quartz admixed with ZSM-5 is caused problably by the high synthesis temperature. Indeed if the synthesis temperature decreases no dense phases are detected (sample 6). In absence or with a low NaOH content even in the presence of NH4 ions, the starting hydrogel does not crystallize, showing that the presence of alkali cations is Indispensable for... 

In a previous paper [10] we assumed that the zeolite acidity is the driving force, that allows a substantial lowering of the reduction temperature of the admixed gallium oxide phase. Recently we proved the... 

The activity of copper-exchanged zeolite catalysts in direct decomposition was influenced by (i) the degree of copper ion-exchange [7] (no decomposition was observed in the absence of copper) and (ii) the Si/Al ratio of the zeolite [8], (iii) the preparation method of the parent Na-ZSM-5 [9]. The effect of admixed dioxygen and water vapour to the feed stream has been reported too [10]. 

The benzene alkylation by propane has been investigated using a zeolite-containing catalyst. The isopropylbenzene formation is shown to begin at 180-350°C over HY and Pt, Re/A Os admixed catalysts. The temperature increase leads to C3H6 (250°C) and other alkylbenzenes (300°C) formation. The by-products may be reduced by the selective poisoning of Bronsted acidic centres by ammonium. From the considerations on the reaction, the probable mechanism of benzene dehydroalkylation by propane has been proposed. 

Mao D, Xia J, Zhang B, Lu G (2010) Highly efficient synthesis of dimethyl ether from syngas over the admixed catalyst of CuO-ZnO-ALOs and antimony oxide modified HZSM-5 zeolite. Energy Convers Manag 51 1134—1139... 

Table 3. Starting materials, mixtures and results of solid-state ion exchange in the system NaCl/H-ZSM-5 . 1, parent zeolite 2, 055/0 1 ratio of the parent zeolite 3, A1 content of the parent zeolite 4, NaCl admixed to 1 g (dry) zeolite 5, HCl evolved on solid-state reaction 6, Cl extracted after solid-state reaction 7, Na+ extracted after solid-state reaction 8, Na+ irreversibly held in zeolite after extraction 9, degree of exchange (%) (data in column 8 divided by data in column 3)...

Narayanan and Sultana [208] as well as Narayanan and Deshpande [209] admixed V2O5 to H,Na-X, H-Y, H-ZSM-5 and H-MOR and subsequently conducted solid-state reaction. Compared to the parent hydrogen zeolites, considerably enhanced activity of the catalysts prepared via SSIE was observed in vapor-phase alkylation of aniline. 

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