Fluoride phases

In the fluoride phase HgFeF5-2H20, /nmv-Hg(On2)2F4 octahedra and FeF6 octahedra share F-corners to form layers connected by hydrogen bonds.351 Similarly, trans-Hg(OH)2F4 octahedra and FeF6 octahedra share F corners, but the Hg(OH)2F4 octahedra also share the OH corners to form the layers in Hg2FeF5(0H)2 H20 352... 

Calcium aluminate chloride, phase in Portland cement clinker, 5 472t Calcium aluminate fluoride, phase in Portland cement clinker, 5 472t Calcium aluminoferrite, phase in Portland cement clinker, 5 472t Calcium aluminoferrite hydrate, 5 477t Calcium—aluminum alloys, 4 530 Calcium amalgam, 22 773 Calcium ammonium nitrate, 2 724 Calcium analysis, of water, 26 37 Calcium A zeolite, separation of hydrocarbons by, 16 823 Calcium—barium—silicon alloy, 22 519 Calcium-bearing manganese silicon,... 

Fluoride (F ) anion conductors fluorides with general formula A F (A = Ca, Sr, Ba, Pb, Cd, Bi, Ln, Sn and their mixtures), and also oxy- and chloro-fluoride phases containing these metal cations. In the latter case, however, both types of anions are often mobile. 

Fluorides and compounds of zinc, cadmium, thallium and lead also undergo cycling and can be deposited in preheaters (K8). Emission of the toxic heavy metals must be avoided. Fluoride phases that have been reported in deposits include KCa,2(S04)2(Si04) 02F (F6) and an apatite phase of composition K3Ca2(S04)jF (T9,P14). 

Since phases related to / -AlF3 exhibit pronounced catalytic activity, attempts have been made to promote activity in this phase by doping with other metals. The perceived advantage is that doped fluoride phases should not alter in contact with haloalkanes since they are already fluorinated. At the present time metals that have been seriously investigated as dopants for /J-MF3 phases are for M = A1, Cr(III) and Mg(II) and for M = Cr, Fe(III) and Mg(II). 

Stezowski, J.J. and H.A. Eick, 1969, The Preparation of a Nonstoichiometric Samarium Fluoride Phase, in Proc. Seventh Rare Earth Research Conference, vol. 2 (National Technical Information Service, Springfield, VA) pp. 741-750. 

Schubert (1989) points out that radius ratio considerations in LaFj would suggest coordination near LaFg, and the LaFj structure should therefore be homeotypic with CaFj. He then relates the LaFj structure to that of CaFj, compares the displacements to those of related structures, e.g., CaFj-YFj superstructures, and discusses crystal energetics. LaFj crystals were examined by DSC from 100 -500 K an anomaly which occurs in the Cp versus T curve is related to a phase transition in which the fluoride sublattice fuses (Aliev and Fershtat 1984). This phenomenon appears related to the high ionic conductivity of the tysonite-type fluoride phases. 

Disordered Chloride Fluoride Phases 11.7.2.1 Samples Prepared by Precipitation... 

However, before doing so, an alternative synthesis approach to an equally Lewis acidic aluminum fluoride phase that can be obtained by a very simple reaction as shown by Equation (6.7) will be briefly introduced, since both phases exhibit very similar catalytic properties ... 

Figure 6.8 CO IR Difference Spectra of Magnesium Fluoride Phases Prepared Using HF of Different Concentrations (Indicated by the Numbers).

Another example of reactions in which M MF catalysts exhibit exiting properties is the very selective olefin hydrogenation by palladium nanoparticles supported on magnesium fluoride phase. Transmission electron microscope (TEM) micrographs in Figure 6.14 display that the majority of Pd particles are approximately 5 nm in diameter, although the particle size distribution spreads up to 20 nm. These catalysts showed extremely high metal dispersion compared with examples reported in literature [73]. 

On the other hand, the 25Nb AlF3 sample recovered after the separation of leached aluminum species became highly selective to hydroxy acids, with a preponderant formation of lactic acid, while the conversion of cellulose decreased only by a few percent when compared with the fresh catalyst (Table 6.9, entry 7). This catalytic performance improvement is clearly due to the leaching of aluminum that enriches the catalyst in niobium oxide fluoride phases (boiled catalyst contains 42.5 mol% Nb and 57.5 mol% A1 as against fresh catalyst (25 mol% Nb and 75 mol% Al)) alongside the introduction of an oxygen/aluminum vacancy adjacent to the niobium sites (NbOF - Lewis acid sites), by the formation of different sixfold coordinated Al units AlF Og. , fivefold coordinated units AIF 05, and fourfold coordinated species AlF 04 t- This way an optimum combination of acidity for the one-pot transformation of cellulose to lactic acid seems to be created. 

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