HY zeolite catalysts

Fig. 34. Improved HDS activity of 4,6-dimethyldibenzothiophene in the presence of a hybrid CoMo/A1203 and Ni-HY zeolite catalyst (270 C, 2.4 MPa, 0.1 wt% of reactant in 10 g of decane, C0M0/AI2O3 Ni-HY = 1.0 0.05 g). Reprinted with permission from Ref. 137, Isoda et at. (1996). Copyright 1996 American Chemical Society.

Namba and co-workers prepared SbF5/HY-zeolite catalysts and examined them in the reaction of pentane. Although the catalysts were quite active in the initial stage, they were completely deactivated afterward by the formation of heavy hydrocarbons (34). Krzywicki and co-workers also... 

TABLE I. Properties of Rare-Earth Exchanged HY Zeolite Catalyst... 

P6-26o A new catalytic pathway for an important intermediate in the production of the nonsteroidal anti-inflammatory drug ibuprofen (e.g., Advil) has been developed/CAer/j. Eng. Set, 51, 10, 1663(1996)]. The pathway involves the hydrogenation of p-isobutyl acetophenone (B) in a solution of methanol containing a HY zeolite catalyst and saturated with hydrogen. The intermediate products are p-isobutylphenyl ithanol (C), p-iscbutylphaiylethylnEtl lether (E) and p-isobutylethyl benzene (F). The reaction scheme is shown below. 

The low activity of HY zeolite catalysts for the acylation of toluene using benzoyl and propionyl chloride is in contrast to the much enhanced activities found for the lanthanum modified equivalents. The importance of the lanthanum component is confirmed by vaiying the level of exchange with high selectivities for the para-product being found for all catalyst modifications. The La-modified/add chloride system is found to be a much more active system for the acylation reaction compared to the equivalent carboxylic add. Higher activity for the aliphatic acylation compared to the benzoylation appears to indicate additional factors restricting the activity in the benzoylation reacton. 

Zeolites, by being in a half way between amorphous silica-alumina and fluorinated alumina, were early recognized as potential components of bifunctional isomerization catalysts. The earliest report of zeolites being used in this application deal on Pt containing X and Y structures (3). They found that the activity increased from the Na to the Ca to the decationized forms. The residual sodium content, and therefore the final acidity of the Pt or Pd HY zeolite catalysts was critical for these type of catalysts (2,4-6). However, to make a successful commercial catalyst the following characteristic have to be accomplished by the zeolitic component ... 

SCHEME 20 Synthesis of 1,5-diarylpyrazoles 29 over HY zeolite catalyst. 

The process which was developed hy DOW involves cyclodimerization of hutadiene over a proprietary copper-loaded zeolite catalyst at moderate temperature and pressure (100°C and 250 psig). To increase the yield, the cyclodimerization step takes place in a liquid phase process over the catalyst. Selectivity for vinylcyclohexene (VCH) was over 99%. In the second step VCH is oxidized with oxygen over a proprietary oxide catalyst in presence of steam. Conversion over 90% and selectivity to styrene of 92% could he achieved. ... 

The water-insoluble salts such as Cs2,5Ho., iPWi204o efficiently catalyse dehydration of 2-propanol in the gas phase and alkylation of m-xylene and trimethyl benzene with cyclohexene this catalyst is much more active than Nafion-H, HY-zeolite, H-ZSM-5, and sulphated zirconia (Okuhara et al., 1992). 

Molybdenum allyl complexes react with surface OH groups to produce catalysts active for olefin metathesis.34 35 Using silica as a support for the heterog-enization of Ti and Zr complexes for the polymerization of ethylene did not give clear results.36 In these cases, HY zeolite appeared to be a more suitable support. The comparable productivity of the zeolite-supported catalyst with... 

A very attractive method for the preparation of nitroalkenes, which is based on the reaction with NO, has been reported. Treatment of alkenes at ambient pressure of nitrogen monoxide (NO) at room temperature gives the corresponding nitroalkenes in fairly good yields along with P-nitroalcohols in a ratio of about 8 to 2. The nitroalcohol by-products are converted into the desired nitroalkenes by dehydration with acidic alumina in high total yield. This simple and convenient nitration procedure is applied successfully to the preparation of nitroalkenes derived from various terminal alkenes or styrenes (Eq. 2.27).53 This process is modified by the use of HY-zeolites instead of alumina. The lack of corrosiveness and the ability to regenerate and reuse the catalyst make this an attractive system (Eq. 2.28).54... 

Selective removal of one isopropylidene group from a diacetal may be achieved by a variety of procedures, most of them involving protic or Lewis acids.100 Particularly common is the hydrolysis of the acetal engaging of the primary position of di-O-isopropylidene derivatives. Bhaskar et al,101 studied the selective deprotection of di-O-isopropylidene acetals derived from D-glucose, D-xylose, and D-mannose, using acid zeolites and montmorillonite K-10. When 102 was submitted to acid hydrolysis in aqueous methanol, the best yields (85—96%) for the monoacetal 105 were obtained when H-beta and HZSM-5 zeolites were employed as catalysts (Scheme 24, Table IV). HY zeolite proved to be ineffective, whereas the yield obtained for the montmorillonite K-10-catalyzed reaction was low (22%). The zeolites found most effective were then used for the hydrolysis of the diacetal 103 and 104, providing excellent yields for the desired corresponding monoacetals 106 and 107. 

A. P. Rauter, F. Ramoa-Ribeiro, A. C. Fernandes, and J. A. Figueiredo, A new method of acetonation with the zeolite HY as catalyst. Synthesis of O-isopro-pylidene sugar derivatives, Tetrahedron, 51 (1995) 6529-6540. 

As already mentioned, the acidity of the HY zeolite precludes its use as a support for Fe3(C0)- 29 then iron particles. The same behaviour is observed for Fe3(C0) 2 silica alumina system. This material, when decomposed at 200°C is not an efficient catalyst for F-T synthesis and only C-j-C products are... 

By characterizing various zeolite catalysts under the same reaction conditions, the authors found weaker MAS NMR signals of alkoxy species for the less active zeolites HY and HZSM-5 than for the more active zeolite H-beta (250). This observation suggests that the alkoxy species observed under steady-state conditions act as reactive surface species in the MTBE synthesis from isobutylene and methanol on acidic zeolite catalysts. 

Zeolite samples that were exhaustively treated were gray in color (materials A). Portions of each treated catalyst (0.3 gram) were calcined at 500°C in oxygen for 6 hours, giving a white product (material B). X-ray analysis showed no deterioration in crystal structure on treatment with TMS and subsequent calcination. Surface area measurements using N2 adsorption at — 196°C and the Point B method are also given in Table I. The value for HY zeolite, activated as described, prior to TMS treatment was 840 m2/gram. 

The rearrangement of protoadamantane to adamantane was studied on HY zeolite and those samples of materials A and B produced by reaction with TMS at 400°C. The catalysts (0.1 gram) were activated at 600°C for 6 hours in vacuo and were transferred to a flow system where the reaction was carried out at 240° C under N2 at atmospheric pressure. The reaction is totally selective, giving 96.7% and 42.5% conversion to adamantane on HY and the A material, respectively, but only 7.2% conversion on the B material. 

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