Metal oxides Lewis acid-treated

Metal oxides, 31 78-79, 89, 102, 123, 157-158, 191, 32 199-121 see also Amorphous metal oxides Sulfate-supported metal oxides specific oxides adsorbed oxygen on, 27 196-198 binary, surface acidity, 27 136-138 catalytic etching, 41 390-396 coordination number, 27 136 electrocatalysts, 40 127-128 Fe3(CO)i2 reaction with, 38 311-314 Lewis acid-treated, 37 169-170 multiply-valent metals, electrocatalytic oxidations, 40 154-157 superacids by, 37 201-204 surface acidity, methods for determining, 27 121... 

Solid superacids may be made by treating ordinary solid add catalysts with strong Br0nsted or Lewis acids. For example, if freshly precipitated titanium hydroxide or zirconium hydroxide is treated with sulfuric acid and calcined in air at 500 °C. a very active solid acid catalyst results. The solids consist mainly of the metal dioxides with sulfate ions coordinated to the metal ions on the surface. Likewise, a superacid solid catalyst can be made by treating these metal oxides with antimony penlafluonde. Both catalysts contain both Br nsted and Lewis acid sites, and they arc sufficiently active to catalyze the isomerization of n-butane at room temperature.26... 

Simple tertiary amines are difficult to deprotonate selectively [195, 196, 200], To increase the acidity of the a-C,H-groups the amine can be quaternized [207], treated with a Lewis acid [208-211], oxidized to an amine N-oxide[161], or, for secondary amines, derivatized with a functional group capable of forming a chelate with the metal (Scheme 5.22). 

The type of superacid sites on SO /metal oxides evacuated at 773 K is only a Lewis type according to the IR absorption bands of adsorbed pyridine [31]. Mortcrra ct al. [32] have shown that pyridine adsorbed on Lewis acid sites dominated the spectra of samples evacuated at 673 K and that the addition of water at 300 K significantly increased the amount of Bronsted acidity. Nascimcnto ct al. [8] report that both Bronsted and Lewis acid sites exist on SO4 /Zr02 treated at 723 K and the ratio of Bronsted to Lewis sites changes with the change of sulfur content. Recently. Lunsford ct al. revealed by use of 31P MAS NMR spectra of adsorbed trimcthylphosphinc that three types of Lewis... 

Transition metal cations in normal oxidation states Until the late 1970s, there had been little study of transition metal cations in HF because of the very low solubility of the di-, tri- and tetrafluorides of the d- and /-elements in HF. Use of counter-anions other than fluoride was precluded because the anions were protonated or solvolysed leading to formation of insoluble metal fluorides. The problem was overcome by treating the insoluble fluoride (MF ) in HF with an appropriate Lewis acid (AFm) ... 

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