Rare earth Y

Metals able to form dodecaborides with the UB,2-type structure are Zr, most of the rare earths (Y, Gd - Lu) and some actinides (Th, U, Np, Pu). 

Rare Earths and Alumina. A much easier and cheaper way of getting the SO2 removal enhancement from rare earths that was observed with the well-exchanged rare earth Y zeolite was to add rare earths, especially cerium, by direct impregnation to high alumina cracking catalyst (24). 

When rare earth Y-zeolite (REY) was added to the PILC or to the parent clay, the dried PILC or "as received" clay was reslurried in water and the calcined REY added to the 10 wt % level. This slurry was then mixed, filtered, dried, and calcined at 500 C for 2 hours in air. The calcined REY was obtained from Union Carbide and contained 14.1 wt % rare earth elements, primarily lanthanum and cerium. Portions of the PILC were pretreated by one of the methods listed below prior to the microactivity testing. 

The intensity of the 3640 cm-1 band is several times greater in rare earth Y zeolite than in the corresponding alkaline earth forms, which led Ward (2/2) to propose a further step in the hydrolysis mechanism, resulting in formation of two structural hydroxyl groups per cation ... 

Previous results(2) had shown that a Pd-Ni-SMM catalyst was effective for hydrocracking hexane as well as a raffinate feed. Conclusions showed that this catalyst system when containing two nickel atoms per unit cell (15 wt % nickel) was approximately 15 times more active than a Pd-rare earth-Y zeolite catalyst and 1.2 times more active than Pd-H-mordenite. This same catalyst system (0.7 wt % Pd-15 wt % Ni-SMM) was chosen for our raffinate processing studies. 

During the five months of operation with the zero rare earth octane catalyst, the effective fresh catalyst addition rate, after correction for catalyst loss from the unit as fines, was about 5 tons/day. Based on a rare earth material balance (Table II) that was used to give the best estimate of pedigree, the equilibrium sample consists of 88% USY octane catalyst. The remaining 12% should be a mixture of the prior two catalysts, the first of which contains a contaminant rare earth level of 0.5 wt% versus 0.1 wt% for the octane catalyst. The balance of this mixture is the rare earth-Y catalyst from the previous changeover which exhibits a rare earth level of 0.85 wt% (Table II). 

Beltrame et al. [19, 20] Flow reactor PE, PS Silica gel, alumina, silica-alumina, rare earths, Y and H-Y zeolites... 

Further examination of the data in Table I reveals several interesting points. Sieve geometry affects selectivity somewhat as shown by the slight differences between powdered, 20-40 mesh size, and tableted Na-Y sieve. Both basic sodium and ammonium-Y sieves and acidic rare earth-Y sieves... 

In the alkylation of benzene with long-chain a-olefins (Ce, Cg, C12, etc ), the large-pore zeolites mordenite, beta-zeolite, and ZSM-12 favor the less bulky 2-phenyl isomers. HY and rare-earth-Y produce a mixture of other -alkylbenzene isomCTS. Shiqie selectivity is attributed here to both product- and restricted transition state type selectivities [76]. 

The final equilibrium concentrations of M+n and H+ depend, as in any chemical reaction, principally upon the activities of the two cations and upon the respective affinities of each for the resin. In general, the cation-resin bond strength increases with increasing charge on the cation, and decreases with increasing radius of the hydrated ion. A typical series, from strong to weak, is Th, La, Ce, Rare Earths, Y, Ba, Cs, Sr, K, NH4, Na, H. 

La2 xSr< +xCu206 -x/2+5 with (4+1) Cu-0 pyramidal coordinations. The small solid/ circles are copper atoms, the large open circles are oxygen atoms, and the shaded circles are the rare earth, Y, Ba, or Sr atoms. 

In their use as catalyst components, rare earth Y zeolites are freauently prepared by ion exchange with commercial rare earth salt solutions. Such commercial salts are mixtures of different rare earths, in which the major components are lanthanum, cerium, praseodymium and neodymium (5). These rare earth elements therefore play a major role in determining the physico-chemical characteristics and stability of Y zeolites that are used in many commercial catalysts. 

Readsorption of water on rare earth Y zeolite did not give rise to a band at 3690 cm"1 but to bands at 3610 and near 3560-3550 cm1. Subsequent dehydration simply removed the water reversibly. If the surface hydroxyl groups are eliminated by evacuation at 700°C, readdition of water at room temperature does not result in the formation of new hydroxyl groups but subsequent heating at 200°C restores the 3640 and 3520 cm"1 bands (48). Zhdanov et al. (78) found that the frequency and ease of removal of adsorbed water depended on the silica-to-alumina ratio of the zeolite. 

Lewis acidity on CeY zeolite after heating to 460°C, whereas Ward (67) detected only Bronsted acidity on rare earth Y zeolite after heating to 480 °C but both forms of acidity after heating to 680°C. 

Figure 6. Flow diagram for the preparation of rare-earth, Y, and Sc orthophosphate powders with controlled particle size by means of precipitation from molten urea. Powders synthesized by this technique have been compacted by hot pressing to form ceramic bodies with >97% of the theoretical density of the compound (after Abraham et al. 1980b).

Figure 19. X-band EPR spectra (at T = 4.2 K) showing the hyperfme structure due to Nd (isotopically enriched with " Nd). The spectra are shown for the apphed magnetic field oriented parallel and perpendicular to the c-axis of the Y(P04) host single crystal. The EPR spectrum of eE and lines from the spectrum of Gd are also present. This type of magnetic resonance spectroscopy has proven to be very useful in the study of the solid-state chemical properties of the rare-earth-, Y-, and Sc-orthophosphates (after Abraham et al. 1983).

Co-milling polypropylene and zeolite Y was carried out by Audisio and co-workers. The product distributions as a function of carbon number at 673 K are reproduced in Figure 6 for NaY, HY and rare earth Y (REY, 10.7% of rare earth oxides) and compared with those observed for thermal degradation and in the presence of silica-alumina (also reproduced above in Figure 4). The product distributions for HY and REY were very similar, while a significantly lower fraction of C5-C11 products was formed when NaY was used. A detailed analysis of the products over HY and REY revealed that a significant amount of isomerization had occurred and olefins were formed in large yields. 

Ultrasound and microwave irradiation processes are known as excellent methods for the preparation of nanoparticles. Recently, nanoparticles of rare earth (Y, La, Ce, Sm, Eu, and Er) oxides have been synthesized [77-81]. In these cases, rare earth nitrates were used as starting materials. When sodium dodecyl sulfate (SDS) was added as a templating agent, layered and hexagonal mesostructures of high specific surface area (225-250 m g ) can be obtained [77]. Monodispersed Ce02 nanoparticles with a mean particle of ca. 3 nm are obtained when tetrametylammonium hydroxide [78] or polyethylene glycol [79, 80] are used as the additives. In addtion, europium oxide nanorods are obtained by the sonication of an aqueous solution of europium nitrate in the presence of anunonia [81]. The particle sizes were about 50 x 500 nm (IF x L) as described in Fig. 6-9. 

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