Alumina sodium role

Alumina supported sodium metaperiodate, which can be prepared by soaking the inorganic support with a hot solution of sodium metaperiodate, was also found to be a very convenient reagent for the selective and clean oxidation of sulphides to sulphoxides79. The oxidation reaction may be simply carried out by vigorous stirring of this solid oxidant with the sulphide solution at room temperature. As may be expected for such a procedure, solvent plays an important role in this oxidation and ethanol (95%) was found to be... 

The effect of the impurities besides sodium do not seem to play an important role in determining the structure of the surface vanadium oxide species. Flourine is the only other impurity whose concentration varies appreciably in the different alumina phases. Flourine cannot be responsible for influencing the vanadium oxide structures since flourine is present in similar concentrations in a and 6,0-Al2O3 while the vanadium oxide structures are changing. It may therefore be concluded that surface impurities other than sodium oxide do not contribute significantly to the change in the structure of the surface vanadium oxide species on the different alumina phases. 

Cho et al. reported that a-alumina is formed from aluminum hydroxide prepared by precipitation with potassium hydroxide. However, when alkaline hydroxide is used as the precipitation agent, alkali cations are incorporated into the product, and commercial gibbsite samples are always contaminated with a small amount of sodium ions. Therefore their starting material seems to be contaminated with potassium, and the presence of potassium ions in their precursor seems to play an important role in the nucleation of a-alumina. They also reported that hydroxyl ions, acetic acid, and pyridine added to the glycothermal reaction system affect the morphology of the a-alumina particles because of their preferential adsorption to a specific surface. ... 

Surface Superbasic Sites of One-electron Donor Character. - The reaction of alkali metal with anionic vacancies on the oxide surfaces (equation 1) leads to the creation of colour centres of F type. The transfer of one electron from the alkali metal atom to an anionic vacancy is the reason for the formation of these defects. The largest quantities of this type of active centre are obtained by evaporation of the alkali metal onto an oxide surface calcined at about 1023 K, at which temperature the largest quantity of anionic vacancies is formed. Oxide surfaces calcined at such high temperatures contain only a small quantity of OH groups ca. 0.5 OH per 100 for MgO and 0.8 OH per 100 for AI2O3), so their role in the reaction is small and the action of alkali metal leads selectively to the creation of defects of the electron in anionic vacancy type. The evidence for such a reaction mechanism is the occurrence of specific colours in the oxide. Magnesium oxide after deposition by evaporation of sodium, potassium, or a caesium turns blue, alumina after sodium evaporation becomes a navy blue in colour, and silica after sodium evaporation becomes violet-brown in colour. ... 

The electrical and/or magnetic properties of a number of mixed oxides of A1 and other metals including members of the spinel family (see Box 12.6) and sodium P-alumina (see Section 27.3) have extremely important industrial applications. In this section, we single out Ca3Al205 because of its role in cement manufacture, and because it contains a... 

Thus the reaction of sodium chloride with titanium from the alloy, or rutile from the scale leads to the formation of TiCl2, Na2Ti03, HC1 and Cl2.This list of reactions is by no means exhaustive, and may also involve reaction with other alloying additions which may be substituted for the titanium metal. Particularly, the role of aluminium must be of importance. A thermodynamic analysis by Travkin et al. [32] confirms that complex oxide scales are formed when titanium and its alloys react with NaCl. Particularly that the formation of volatile metallic chlorides are thermodynamically favourable, especially for alloying additions Zr, Mo and Al. The subsequent pyrohydrolysis of these metal chlorides results in the formation of HC1 gas, particularly with Mod., and AlClj. Furthermore, such pyrohydrolysis of halide salts may be accelerated by the presence of alumina within the scales, which acts as a catalyst [25]. 

Yoon, S. Panov, A. G. Tonkyn, R. G. Fbcling, A. C. Barlow, S. E. and Balmcr., M. L. An examination of the role of plasma treatment for lean NOx reduction over sodium zeolite Y and gamma alumina Part I. Plasma assisted NOx reduction over NaY and AI2O3 Catal. Today. 2002, 72,243-250... 

Small amounts of water act in synergy with sonication and solid-support catalysis, for instance, in the reaction of thiocyanate ions. As in the previous case, presonication of the reagent and the support was found to improve the selectivity. These methods permit the substitution reactions to be run even in apolar solvents. Two practically simultaneous papers have described the preparation of aryl sulfones by alkylation of sodium arylsulfinates with reactive alkyl chlorides.i The reaction with benzyl chlorides is best performed on alumina, and allyl bromide reacts quantitatively in a DMF-water mixture in a few minutes. Activated primary halides undergo substitution by sodium azide in aqueous solution to give the potentially explosive organic azides. 1 The paper discusses the possible role of the relative densities of the starting material, the aqueous solution of the reagent, and the product in the success of the preparation. 

We have previously studied the role played by the support (silica, alumina, magnesia and titania, both anatase and rutile) on the surface properties of vanadia (ref. 6-9), concluding that the interaction between the support and the supported phase, and hence their activity in the above mentioned processes, greatly depends on the difference in their basicities. The aim of the present paper is to insight in this study, analyzing the role played by a usual dopant (sodium) on the properties of alumina- and titania- supported vanadia, using two different methods to incorporate vanadia on the surface of the support, i.e., standard impregnation methods and mechanical mixture of the oxides, as we have observed (ref. 7 and 9) that some of the properties of the final... 

---