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Rare earths self-supported

A similar type of catalyst including a supported noble metal for regeneration was described extensively in a series of patents assigned to UOP (209-214). The catalysts were prepared by the sublimation of metal halides, especially aluminum chloride and boron trifluoride, onto an alumina carrier modified with alkali or rare earth-alkali metal ions. The noble metal was preferably deposited in an eggshell concentration profile. An earlier patent assigned to Texaco (215) describes the use of chlorinated alumina in the isobutane alkylation with higher alkenes, especially hexenes. TMPs were supposed to form via self-alkylation. Fluorinated alumina and silica samples were also tested in isobutane alkylation,... [Pg.292]

In some respects the rare earths are almost like oxides of isotopes of the same metal. In other respects they differ in ways that are so subtle as almost to defy understanding. Data will be presented for extrinsic field effects at relatively high and low fields over most of the rare earths in normal (referred to here as self-supported ) form and also in lanthana-supported form. One example of a rare earth in alumina-supported form will be given. [Pg.32]

Conversion Rates for Self-Supported Rare Earths and Fractional Rate Changes at 29S K in a Field of 18 kOe... [Pg.33]

Fractional Rate Changes for Self-Supported and Lanthana-Supported Rare Earths at 298 K in a Field of 40 Oe... [Pg.33]

These samples were prepared by impregnation of La203, of surface 2.0 m2 g 1, with rare earth nitrate solution of concentration sufficient to give approximately the same nominal surface concentration of the paramagnetic species as occurs in the self-supported oxide. Moderate differences in preparative treatment caused changes of 2 to 3 fold in ka, but no significant change in AkH except as described later. [Pg.34]

All paramagnetic self-supported rare earths show a large positive rate change in fields of over 1 kOe. The effect reaches saturation at about 10 kOe. [Pg.38]

It might be thought from its anomalous behavior that in self-supported Eu203 the Eu3+ is actually reduced to Eu2+, but this change is accompanied by a marked increase in /3 which is not reflected in an abnormal k0. The anomalous behavior of Gd203/La203 may be related to the fact that Gd3+ is the only trivalent rare earth ion in an S spectroscopic state. [Pg.38]

Strontium ferrite perovskite. The nonstoiehiometric strontium ion oxide SrFeOx (2.5solid state electrolyte itself, doped with rare earths or transition metals, it forms materials, whieh exhibit even greater ionie conductivity. These oxides are used as materials for self-supported oxygen conduetivity membranes. [Pg.128]

Detailed analysis of the product distributions demonstrates the selectivity of supported Ce02 and other rare-earth oxides (REOs) for unsymmetric ketoniz-ation. For example, if acid condensation were statistically random, the ratio of the self-condensation products to the unsymmetric product MCPK should be 0.20 for a 4/1 molar acetic acid/CCA. Actual observed ratios were as low as 0.03. Low ratios were attainable only after a certain time on stream, which leads to the question considered below of what is happening to supported REOs in the first few days of operation. [Pg.297]

The activated interstitial model which hinges on the relative ease of some f electron promotion in its initial form or on the possibility of d-f hydridization in its modified form seems to account for the main anomalous features observed in connection with self-diffusion in bcc e-Pu, S-Ce and possibly y-La and y-Yb. Beside these metals, however, anomalous diffusion has also been observed in /3-Ti, /3-Zr, /3-Hf, y-U and the rare earth metals -Pr, /3-Nd and P-Gd. The normal behavior of Eu (table 12.2), which among this latter group of metals is the only one having the bcc structure as its only allotropic form, stands out in marked contrast to the other bcc rare earth metals. It strongly supports Seeger s (1972) suggestion that anomalous diffusion in bcc metals is in some way connected to the phase transformation which precedes the bcc phase. [Pg.859]

As described in sect. 2, the potential of a free atom from the rare-earth sequence develops two wells. The outer well is the usual atomic well, with an asymptotically coulombic behaviour (long range potential), and contains an infinite number of states. The inner one is a short range well, which is close to the critical binding condition to support one state (4f). This model is backed up by central field self-consistent ab initio Hartree-Fock calculations for free atoms, and involves no adjustable parameters. It correctly describes (a) the order of filling of d and f subshells of the transition elements and R elements (b) the fact that filling occurs deep inside the atom and (c) the behaviour of XAS of free atoms of the Q- and R-element sequences. [Pg.46]


See other pages where Rare earths self-supported is mentioned: [Pg.275]    [Pg.142]    [Pg.34]    [Pg.202]    [Pg.597]    [Pg.578]    [Pg.688]    [Pg.736]   
See also in sourсe #XX -- [ Pg.32 , Pg.33 ]




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