Na-Y zeolite

Szanyi et al., using again in situ IR-TPD coupled skills, studied the effect of acid sites on the catalytic activities of a series of H+-modified Na-Y zeolites in the non-thermal plasma assisted NO reduction reaction using a simulated diesel engine exhaust gas mixture. The acid sites were formed by NH ion exchange and subsequent heat treatment of a NaY zeolite. The catalytic activities of these H+- modified NaY zeolites... 

Kwak, J.H., Peden, C.H.F. and Szanyi, J. (2006) Non-thermal plasma-assisted NO reduction over Na-Y zeolites The promotional effect of acid sites, Catal. Lett., 109, 1. 

Figure 15, Dealumination of zeolite Na-Y using SiClk vapor studied by 29Si-MAS NMR at 79.8 MHz. Key top, parent Na-Y zeolite and bottom, after treatment with SiClk. (Reproduced from Ref. 30. Copyright 1982, American Chemical Society.)...

Figure 4.33 IR spectrum of a dehydrated H,Na-Y zeolite in OH stretching region. (Reprinted from Introduction to Zeolite Science and Practice, Studies in Surface Science and Catalysis, Vol. 58, J.H.C. van Hooff, J.W. Roelofsen, Techniques of Zeolite Characterization, pp. 241-283. Copyright 1991. With permission from Elsevier.)...

Calculate the Si/Al ratio of a Na-Y zeolite from a Si NMR spectrum with the following intensities ... 

The ACH process has recently been improved, as stated by Mitsubishi Gas. Acetone-cyanohydrin is first hydrolized to 2-hydroxyisobutylamide with an Mn02 catalyst the amide is then reacted with methylformiate to produce the methyl ester of 2-hydroxyisobutyric acid, with coproduction of formamide (this reaction is catalyzed by Na methoxide). The ester is finally dehydrated with an Na-Y zeolite to methylmethacrylate. Formamide is converted to cyanhydric acid, which is used to produce acetone-cyanohydrin by reaction with acetone. The process is very elegant, since it avoids the coproduction of ammonium bisulphate, and there is no net income of HCN. Problems may derive from the many synthetic steps involved, and from the high energy consumption. 

Synthetic forms Beryllophosphate X, Li-LSX, LZ-210, SAPO-37, siliceous Na-Y, zeolite X (Linde X), zeolite Y (Linde Y), zincophospate X... 

O2, H2, and CO adsorbed and condensed on (H,Na)-Y zeolite cages as studied by variable temperature IR spectroscopy. Phys. Chem. Chem. Phys., 8,1186-1196. 

Borgna, A., Magni, S., Speulveda, )., Padro, C.L., and Apesteguia, A.R. (2005) side chain alkylation of toluene with methanol on Cs-exchanged Na-Y zeolite effect of Cs loading. Catal. 

Rare-earth exchanged [Ce ", La ", Sm"" and RE (RE = La/Ce/Pr/Nd)] Na-Y zeolites, K-10 montmorillonite clay and amorphous silica-alumina have also been employed as solid acid catalysts for the vapour-phase Beckmann rearrangement of salicylaldoxime 245 to benzoxazole 248 (equation 74) and of cinnamaldoxime to isoquinoline . Under appropriate reaction conditions on zeolites, salicyl aldoxime 245 undergoes E-Z isomerization followed by Beckmann rearrangement and leads to the formation of benzoxazole 248 as the major product. Fragmentation product 247 and primary amide 246 are formed as minor compounds. When catalysts with both Br0nsted and Lewis acidity were used, a correlation between the amount of Br0nsted acid sites and benzoxazole 248 yields was observed. 

The distribution of cations in Na-Y, La,Na—Y and Cs,Na—Y zeolites were studied using xenon adsorption isotherms and Xenon- 129 NMR spectroscopy. 

Cs,Na-Y and La,Na—Y zeolites. The results are comparable with that of the Si and Na NMR investigations and the known structure data. 

A binder—free Na-Y zeolite with Si/Al ratio of 2.29 was obtained from Strem Chemical Co., La,Na—Y and Cs,Na-Y zeolites were prepared by exchanging Na-Y zeolite with LaCls and CsCl solution at room temperature. The percentage of metal ion exchanged in a zeolite has been determinated by Inductively-Coupled-Plasma Atomic Emission Spectroscopy and the number is used as prefix for the samples, e.g., Cs exchanged level of 667. is represented as 66Cs,Na-Y sample. 

Among three-dimensional framework hosts forming intercalation compounds, zeolites (see Section 1.5) have attracted considerable attention because of their technical importance (Derouane, 1982 Dyer, 1984). Intracrystalline voids in anhydrous zeolites provide a strongly polar environment that can be filled with polar or ionic species to increase the crystal energy. Treatment of zeolites (e.g. Na-Y zeolite) with vapours of sodium results in the formation of a red product consisting of Na " intercalated into the zeolite cavities (Thomas, 1983). The locations of these clusters inside the zeolites are not yet known, but they seem to be buried within the rather inaccessible cavities inside zeolites, with the result that ordinary solvents do not reach them. Such intercalation of ionic species in zeolites may have implications in nuclear-waste treatment and storage. 

Kinetics and Mechanism of w-Butene and w-Pentene Isomerization over Na-Y Zeolites... 

Tphe isomerization of olefins over acidic catalysts has been carefully A studied in the past few years. Hightower and Hall (1, 2) have studied the isomerization of n-butenes over silica-alumina. They were able to interpret their results in terms of a simple model involving the 2-butyl carbonium ion as a common intermediate. More recently Lombardo and Hall studied the isomerization of the same olefins over Na-Y-zeolite. They showed that the reaction was first order in conversion as well as time (3), that the isomers could be directly interconverted (4), and that activity sharply increased with water addition reaching a saturation value (5). There are, however, reports in the literature which are at variance with this idea. Dimitrov et al. (7, 8) explained their results for n-butene isomerization on Na-X-zeolite in terms of a free radical type mechanism. As discussed more thoroughly elsewhere (4) others have argued about the nature of catalytic activity on zeolites (9-13). 

In view of this situation we thought it worthwhile to investigate further the mechanism of normal olefin isomerization over Na-Y-zeolite. 

Catalysts and Pretreatment. The starting molecular sieve was a Linde Na-Y-zeolite (lot 1280-133). It was purified by succesive exchanges with sodium acetate to remove almost completely the divalent cations it was then carefully washed with slightly alkaline water (pH = 10). Aliquots of this parent catalyst (I) were treated in two different ways (a) catalysts II to V were back exchanged to increase their Ca2+ content (b) four other samples (VI to IX) were treated with increasing amounts of distilled double deionized water to produce varying degrees of cation deficiencies. The analytical data for these samples are listed in Table I. 

Figure 3. Variation of catalytic activity of Na-Y zeolite with H+ content...

The isomerizations of n-butenes and n-pentenes over a purified Na-Y-zeolite are first-order reactions in conversion as well as time. Arrhenius plots for the absolute values of the rate constants are linear (Figure 2). Similar plots for the ratio of rate constants (Figure 1), however, are linear at low temperatures but in all cases except one became curved at higher temperatures. This problem has been investigated before (4), and it was concluded that there were no diffusion limitations involved. The curvature could be the result of redistribution of the Ca2+ ions between the Si and Sn positions, or it could be caused by an increase in the number of de-cationated sites by hydrolysis (6). In any case the process appears to be reversible, and it is affected by the nature of the olefin involved. In view of this, the following discussion concerning the mechanism is limited to the low temperature region where the behavior is completely consistent with the Arrhenius law. 

Closer examination of the cyclobutanol t/c ratios from homologous and isomeric n-alkanones in the same zeolites reveals some interesting trends (Table 12). The t/c ratios from all of the alkanones in the Na-X and Na-Y zeolites are as expected from reaction in a large or flexible reaction cavity which is very polar (like that provided by an alcohol solution). The t/c ratios in the ZSM zeolites indicate that selectivity depends upon the total ketone length and the position of the odd electron centers of the BR along the chain. Ratios of 60 or more are reported from 4-alkanones with 9 or more carbon atoms the t/c ratios from 4-octanone in ZSM-5 and ZSM-11, 15 and 18 respectively, mark 8 carbon atom chains as being critical to a c-BR occupying... 

Catalytic activity measurements. Alkali metal ion X and Y zeolites show no activity for hydrocarbon conversions involving carbonium ion intermediates. Ward (210) showed that the decomposition of cumene to benzene and propylene did not occur over Na—Y zeolite at 260°C, whereas extensive conversion took place with H—Y and alkaline earth ion-exchanged forms. Similarly, isomerization of o-xylene at 250°C did... 

Ammonium Ion Exchamge. Linde anhydrous Na Y zeolite was used ais received to prepare NH + ion exchainged samples. The general procedure wais to add the zeolite to 1.0 M NH.NOg solution at a designated temperature (23, 50, 65, 85, or 100°C) such that the ratio of solution volume to solid mass (v/m) wais 20 cnr/g. 

Copper(II) Ion Exchanged Y Zeolites. The zeolites utilized were the parent anhydrous Na Y zeolite [Na. (A10 ). (SiO.),.. and... 

---