Mechanism and Kinetics of some Reactions on Silica-Alumina Catalysts

The dehydration of alcohol when its vapor is led over alumina, or some other heterogeneously acting catalysts, is already known from the end of the eighteenth century.     

Transition Metal Ion Photoluminescence as a Technique for the Study of Structures of Oxidic Catalysts

The use of spectroscopic techniques in the study of catalysts is rapidly increasing and has given a stimulus to research in catalysis. All techniques, however, are of restricted applicability; for example, ESR, NMR, reflection spectroscopy, and X-ray electron spectroscopy. Often a number of techniques have to be applied to give the full answer to a problem. The same is true for the technique under discussion in this paper. Luminescence spectroscopy can be helpful for a certain number of systems but is far from being generally applicable. It is, however, specific in the sense that it can solve certain problems, especially in oxidic catalysts, which are very difficult to solve with other techniques.     

The Kinetics of the Fischer-Tropsch Synthesis

The literature on Fischer-Tropsch synthesis can be divided into two broad categories: The major portion falls into the category of empirical product distribution studies done with catalyst improvement in mind, while a smaller body of data has been slowly accumulated with the intention of understanding the fundamentals of the reaction. Of this smaller body of mechanistic and kinetic work, only part deals with the quantitative formulation of rate and product distribution phenomena. A vigorous effort has also been made in recent years to contribute to this understanding by surface studies. This approach, however, has at best offered tantalizing views of the various adsorbed species without leading to a quantitative formulation of the kinetics of observable phenomena at reaction conditions.     

COMPLEX FORMATION AND LIQUID-LIQUID EXTRACTION OF SILVER WITH CYCLIC AND OPEN-CHAIN OXATHIA ALKANES

The complex forming and extraction properties of various open-chain and two cyclic oxathia alkanes towards silver have been studied. The investigations confirm the direct proportionality between extraction constants and related complex stability constants.The extraction of silver by open-chain oxethie alkenee is greeter than by structurally analogoue thicacrown compounds. This fact and the determined stability constants show an absence of a macrocyclic effect during complex formation. The differences of extraction power between the various open-chain compounds can be interpreted on the basic o f the coordinative saturation and stereochemiatry of the silver ion, on the size o f the poesible chelate rings, and on the complexing capability o f the ether oxygen atoms.     

THE USE OF THE ROTATING DIFFUSION CELL TECHNIQUE FOR THE STUDY OF SOLVENT EXTRACTION KINETICS

The application of the Rotating Diffusion Cell (RDC) to the study of solvent extraction kinetics has been described. In the RDC the two phases are brought into contact at the surface of a membrane filter. The filter la rotated on a cylinder, establishing well defined rotating disk hydrodynamics on either side of the filter surface- It is therefore possible to characterize precisely the diffusional processes of the reactant and product species on the aqueous and organic sides of the interface. The area of interfacial contact may be varied without affecting the diffusional processes. It is the characterization of the diffusional processes and the ability to vary the area of interfacial contact which makes this technique very useful in solvent extraction kinetic studies. A few experiments from the cobalt-HEHEHP system have been described to illustrate the use of the RDC.     

LIQUID-LIQUID EXTRACTION STUDIES OF METAL IONS WITH DIAZACROWN AND STRUCTURE ANALOGOUS OPEN-CHAIN COMPOUNOS

1,10-diaze [8]crown-6, their N,N'-dibutyl- and dioctyl-substituted derivatives and the structure analogous open-chein tetreoxedieza slkanee have been synthesized in order to examine the extraction properties for Na⁺, K⁺, Sr²⁺ and Hg²⁺. It wes found, that the extraction of strontium, potassium and sodium picratee with azacrown compounds ie much higher than that with open-chein oxaaze alkanes. 1,10-diaze [18] erown-6 has a good selectivity for the extraction of Sr²⁺ over K⁺ and Na in alkaline solution. In the case of Sr²⁺ the diffarencea between tha various azacrown compounds are email, whereea in the caee of K⁺ and Na the substituted derivativee are better extractante. Theserssulte correspond qualitativsly with tha order of stebility conetantB in protic solvsnts. The extrectebility of N,N'-dioctyl-l, 10-dieze[18]crown-6 for HgCl₂ is very high. Contrerv to the order of stability conetants the uneubetituted conpound do not extract mercury under the choeen experimental condition*. The extraction power of open-chain conpounde ie aleo high and strong Influenced by the alkyl eubatltuente at the nitrogen donor stons,     

THE EXTRACTION OF CADMIUM FROM A MIXTURE OF PHOSPHORIC AND HYDROCHLORIC ACIDS

ABSTRACT

The feasibility of using trialkylphosphine oxides to remove cadmium from mixed, acidic chloride-phosphate systems was investigated. Interpolations from extraction isotherms indicated that raffinates containing very low levels of cadmium (approximately 0.5 mg/L) could be produced readily. Stripping was accomplished with water. The co-extraction of acids was minimal.     

SPECIATION STUDY ON THE ION EXCHANGE EXTRACTION OF SILVER,COPPER, IRON AND ZINC CYANO COMPLEXES WITH AN ITERATIVE SLOPE ANALYSIS TECHNIQUE.

ABSTRACT

A slope analysis technique was developed and applied to the study of various equilibrium distribution isotherms in order to determine the speciation involved in the ion exchange. The slope analysis technique consisted of a computer iterative procedure to estimate the equilibriura resin composition and the introduction of ‘macro’ concentrations of a foreign anion to induce limiting conditions.

The results indicate that, under the experimental conditions and with tht resi.is studied, both copper and ziac are extracted mainly as bivalent ions. Evidence was found that iron is extracted as a tetravalent ion whereas silver appears to be extracted as a mixture of mono- and bivalent ions.     

Cation Exchange Equilibria with Chromium (III) Species by Strong Acid Ion Exchangers

The exchange of hydrogen ions for trivalent chromium species with strongly acidic exchange resins has been investigated. The experiments comprised of systems with chromium chloride and basic chromium sulphate which are applied in leather tanning. Exchange equilibria at ambient temperature were investigated as a function of pH and total chromium concentration. Exchange strongly depends on the speciation in each system. As can be expected, with chromium chloride solutions a strong preference of chromium species occurs. However, a complete pattern is found for systems with basic chromium sulphate where chromium species are not fully preferred.