Effect Of Countercations Research Articles

Effect of countercations in catalytic photooxidation of isopropyl alcohol by decatungstate isopolyanion

By utilizing homogeneous decatungstate solution, we have found a novel catalyst system for photooxidation of isopropyl alcohol under excess of O 2. The decatungstate with countercation ratio of K: TBA (tetrabutylammonium) = 3 : 1 shows an activity about double that of the homogeneous K or TBA salt of decatungstate. A new redox cycle considering the ion-pair between decatungstate and countercations is proposed.

The selective determination of halogens and sulphur in solution by atmospheric-pressure helium microwave-induced plasma emission spectrometry coupled to an electrothermal introduction system

Instrumentation is described for the direct determination of Cl, Br, I and S in dissolved samples. A tantalum furnace is coupled directly to a TM 010 cavity, in which a helium microwave plasma is generated at atmospheric pressure. Samples (20 μl) are dried, ashed and atomized; the free atoms are transported by helium to the cavity, where they are excited. Detection limits are in the sub-mg l -1 region. The effect of counter cations is removed by the addition of 50 mg l -1 potassium hydroxide, which also helps to suppress interferences by large amounts of matrix constituents, but the standard addition technique remains necessary to permit determinations that are reliable to within 5%.

Characteristics of heteropoly compounds as catalysts for selective oxidation

As catalysts for selective oxidation, heteropoly compounds such as 12-molybdophosphoric acid (H 3PMo 12O 40) and its salts have been investigated, in relation to the acidic property, the contribution of bulk acid, the effect of steam in the feed gas, the thermal stability, the effect of countercations, and the oxidation activity and selectivity. It was found that, though the heteropoly compounds are different in several physical characteristics from ordinary mixed metal oxides, the catalytic actions can be understood, to a great extent, from the acid-base properties much as in the case of mixed-oxide catalysts.