الفهرس 
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Abstract
Catalysts with different loadings (2. 5 and 8% w/w metal) of nickel and cobalt over different supports (y alumina, silica, synthetic amorphous and natural crystalline alumo-silicates) were prepared by impregnation method. The work aimed at the study of the mutual effects and the interaction modes of the metal with the support.
These mutual effects were studied with respect to the catalytic activity, structural and textural properties of the prepared catalysts.
The catalytic activity was studied through the isomerization and cracking of n-hexane and through the dehydrogenation of cyclohexane in pulse flow system attached with gas chromatograph. Dehydrogenation of cyclohexane showed the catalytically active metal, cracking took place on the support while isomerization occured on both the metal and the support. 2% w!w Ni over alumo silicate and 5% w/w Ni over clay were found to be the most
active and selective catalysts for isomerization and
dehydrogenation reactions. They could be used for refining of petroleum distillates to obtain high octane gasoline, low freezing point civil and military jet fuel and low pour point diesel oil. 8% w/w Co over alumo-silicate was highly active and selective cracking catalyst and could be used for the
cracking and hydrocracking of heavy petrokum fractions to lighter ones.
Adequate mathematical models were derived for the different reactions over the different prep<lred catalysts. These models showed that metal loading is the most effective factor in these reactions.
The interaction of the metal and support was studied by means of XRD and DSC techniques to detect the interacted species and phases. Many interaction species were detected such as metal aluminates, metal oxides and metal alumo silicate hydrates; being varied according to the metal loading, the type of metal and support used.
Hydrogen chemisorption was used to estimate the degree of metal dispersion, metallic surface area and average particle size of loaded metals.
Physical adsorption of nitrogen was applied to study the textural properties of the prepared catalysts to investigate the specific surface area, pore volume, pore radius, por size
distribution and Ve-t plots. The results obtain were found to
run in harmony with the catalytic activity data.