Generalized Wagner’s diffusion model of surface modification of materials by plasma diffusion treatment

0 f^-1(t/t₀), where g(t) is the sub-layer thickness at time t, g₀ and t₀ are parameters that depend on the treated material and plasma characteristics, and f^-1 is the inverse function of f(x)=-(ln(1-x)+x), where x=g(t)/g₀, 0≤x≤1. Under negligible erosion effects, the model becomes of Wagner’s diffusion model type and the expression for g(t) reduces to the parabolic law. The model can be simplified by considering the compound layer as a united one. The general and simplified models can be used as a method for the experimental determining of the effective diffusion coefficients and the erosion rate during plasma treatment of material surfaces. Received: 26 February 1998/Accepted: 15 March 1998     

Preparation of fibrous CoMo/Al2O3 hydrotreating catalysts by the sol-gel method

Fibrous CoMo–Al oxide hydrotreating catalysts have been prepared by the sol-gel method. It is shown that their catalytic properties are similar to the properties of commercial catalysts prepared by traditional methods.     

Electron and Geometry Structure of Hydrogen-Bonded Complexes of Guanine with One Molecule Methanol. A DFT Level Study

The geometries, harmonic vibrational frequencies, and energies of eight hydrogen-bonded complexes of guanine with one molecule methanol are computed using the DFT (B3LYP) method together with the 6-31+G* basis functions. In the investigation two stable tautomers of guanine (oxo-amino N9H and oxo-amino N7H) were chosen. They were included in a variety of H-bonded complexes with one molecule methanol. In order to investigate the nature of the intermolecular bonds, the bonding energies and thermodynamic properties of the complexes were calculated.     

Isomerization and disproportionation of 1-methylnaphthalene on zeolites

The catalytic conversions of 1-methylnaphthalene in the presence of HY, HM, HZSM-5 and SAPO-5 have been studied under varying experimental conditions. While the main reaction is the isomerization, disproportionation also takes place. A correlation between the pore size and acidity of the catalysts and their activity, selectivity and stability is observed.     

Synthesis of 5,7,11 b,12-tetrahydro-isoindolo[2,1-b]isoquinolinium methiodides and theirStevens rearrangement

The title compounds5 were synthetized in two steps from the corresponding isoindolo[2,1–b]isoquinoline-5(7H)-ones3, obtained in high yields from 3-ethoxy-1H-isoindoles2 and homopthalic anhydrides1. TheStevens rearrangement of5 gave 2-methyl-2,3-dihydro-1H-isoindole-1-spiro-2-indanes6.

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Synthese von 5,7,11 b,12-Tetrahydro-isoindolo[2,1-b]isochinolinium Methiodiden und ihre Stevens-Umlagerung

Zusammenfassung Die Titelverbindungen5 wurden in zwei Stufen aus den entsprechenden Isoindolo[2,1–b]isochinolin-5(7H)-onen (3) dargestellt, die ihrerseits in hohen Ausbeuten aus 3-Ethoxy-1H-isoindolen (2) und Homophthalsäureanhydriden erhältlich sind. DieStevens-Umlagerung von5 führte zu 2-Methyl-2,3-dihydro-1H-isoindol-1-spiro-2-indanen (6).

     

Kinetik und Mechanismus der Oxydation von 1,2,4,5-Tetramethylbenzol in essigsaurem Medium

The liquid phase oxidation of 1.2.4.5-tetramethylbenzene catalysed by cobaltous acetate and promoted by KBr in acetic acid was kinetically studied. In view of deriving the kinetic equation for the absorption of oxygen, a number of experiments were carried out. The values of the activation energy and of the preexponentA=10¹⁴ were determined as well. The resulting kinetic equation: $$ - \frac{{d\left[ {O_2 } \right]}}{{d\tau }} = 10^{14} \cdot \exp \left( { - \frac{{84,460 \times 10^3 }}{{RT}}} \right) \cdot C_{C_6 H_2 (CH_3 )_4 }^{0,5} \cdot C_{Co(OAc)_2 }^{0,5} \cdot C_{KBr}^{0,5} $$ is in accordance with the theoretically derived expression of this type.