Potassium oxygen layer

The iron surface is wetted by promoter oxides. The potassium atoms can migrate to the iron surface under ammonia synthesis conditions to adsorb on the free iron atoms or cover the layer of the other promoter oxides present there earlier. A recent paper demonstrates that under ammonia s3mthesis conditions a clean iron surface which is in direct contact with the multiply promoted iron catalyst is covered with a potassium oxygen layer. This result indicates that despite the presence of other promoters (Al, Ca) in the catalyst it is potassium that covers the iron surface. Even prolonged maintenance of such a sample under ammonia synthesis conditions (700 K, 10 MPa) does not change the composition of its surface. 

Figure 3.73 shows the vertical views of Fe (100) face covered by potassimn and oxygen in the double-layer model. The surface of the catalyst is fully and homogeneously covered with a potassium-oxygen layer. Due to the assmned K/O ratio being 1 1 and the location of potassium atoms on the outer layer, no other adsorption sites on the iron surface are occupied. According to this model, the oxygen atoms occupy from 50% to 57% of the adsorption sites on the iron surface, but since they are located under the potassium atoms, the free adsorption sites exist and are exposed to vacuum (Fig. 3.73). Nitrogen molecules can find their way to these sites between potassium atoms.

Arabczyk postulated a simple model. Potassium atoms are adsorbed on iron surfaces, while in the free sites, adsorbed non-metals are present under the potassium atomic layers. Under the ammonia synthesis conditions, those free sites are partly occupied by oxygen atom in order to stabilize the potassium. The existence... 

Once purification of the niobium has been effected, the niobium can be reduced to the metallic form. The double fluoride salt with potassium, K2NbFy, can be reduced using sodium metal. The reaction is carried out in a cylindrical iron vessel filled with alternating layers of K NbF and oxygen-free sodium ... 

Dissolution of Silver. Silver is dissolved by oxidising acids and alkaU metal cyanide solutions in the presence of oxygen. The latter method is the principal technique for dissolving silver from ore. Silver has extensive solubiUty in mercury (qv) and low melting metals such as sodium, potassium, and their mixtures. Cyanide solutions of silver are used for electroplating and electroforming. The silver is deposited at the cathode either as pure crystals or as layers on a mandrel. 

Fig. 1. Diagrammatic representation of the succession of layers in some layer lattice siHcates (12) where 0 is oxygen , hydroxyl , siHcon o. Si—Al aluminum C, Al—Mg O, potassium , Na—Ca. Sample layers are designated as O, octahedral T, tetrahedral and B/G, bmcite- or gibbsitelike. The...

Recently, the immobilisation of indicators in tiny beads rather than in polymer layers has provided nanoparticles which can be inserted into cells and allow the measurement of various analytes (oxygen, sodium, potassium) within a living cell16. 

Monensin belongs to the family of polyether ionophores. These compounds consist of a series of tetrahydrofuran and tetrahydro-pyran rings and have a carboxyl group that forms neutral salts with alkali metal cations. Their three-dimensional structure presents a lipophilic hydrocarbon exterior with the cation encircled in the oxygen-rich interior. They probably act by transporting cations through the lipid bi-layer of cell membranes, thereby preventing the concentration of potassium by the cells. Evidence for this is... 

The catalyst, used in the form of a ceramic honeycomb monolith, is constituted, as in mobile applications, by a noble metal and an absorber element, such as potassium, deposited on a Y-AI2O3 wash-coat layer. In the oxidation and absorption cycle, the SCON Ox catalyst works by simultaneously oxidizing CO and UHCs to CO2 and H2O, while NOj, are captured on the adsorber compound. Catalyst regeneration is accomplished by passing a controlled mixture of regeneration gases across the surface of the catalyst in the absence of oxygen. 

Figure 6. HREELS spectra following the adsorption of 1.0 L oxygen on a K i(lOO) layer at 300 K. The K/Ni(100) surface was prepared by evaporating 2 ML of potassium onto a clean Ni(lOO) surface at 300 K.

The oxidation of sulfides to sulfones has been the subject of extensive studies, since sulfones are useful synthons for the construction of various chemically and biologically significant moleculesJ Recently, a new catalytic system has been developed by exchanging potassium osmate onto chloride-saturated layered double hydroxides (Figure 9.1), which we have shown to be an efficient catalyst for the direct oxidation of sulfides to sulfones, using molecular oxygen as the stoichiometric oxidant and with delivery of two oxygen atoms simultaneously to the sulfide, reminiscent of olefin dihydroxylation reactions. 

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