The effect of active component content on the catalytic activity of supported sulfide catalysts in the synthesis of C17 olefins from stearic acid has been studied. It has been shown that an increase in the nickel content leads to a decrease in the catalyst activity; in addition, there is a negative correlation between the activity and the fraction of large particles on the support surface. The highest heptadecene selectivity (50–60%) is observed for alumina-supported catalysts owing to the higher degree of dispersion of the active component.
The kinetics of liquid-phase decarbonylation of stearic acid in n-dodecane on γ-Al2O3 supported nickel sulfide catalyst promoted with silver was experimentally studied at 350 °C. The parameters of the reaction steps were determined and a structural kinetic model was developed. The model was compared with an earlier developed kinetic model for the unpromoted catalyst. It was suggested that an increased reaction selectivity in the presence of silver promoted catalyst was caused by a change in the composition of the adsorption complexes formed by the active sites of the catalyst. This change in the composition of the complexes is probably associated with an increase in the average size of the surface active particles of the catalyst.
Liquid phase hydrogenation of phenylacetylene was investigated on a series of 9.1 wt% Pd/C catalysts prepared from bis(eta(3)-allyl)palladium complexes, as well as commercial Russian Pd/C catalyst (GIPKH-108). Pd/C catalysts were characterized by oxygen absorption and SEM. All prepared Pd/C catalysts demonstrated very high selectivity to styrene. The reduction temperature of palladium precursor has a significant effect on the palladium dispersity, but the substituent near terminal carbon atom of allyl ligand affects the dispersity more essentially than reduction temperature. Pd/C catalyst prepared from bis[(eta(3)-allyl)palladium acetate] showed highest metal dispersity, activity and selectivity in the hydrogenation of phenylacetylene to styrene.
The substitution of silica gel for γ-Al 2 O 3 to be used as a support for a nickel sulfide catalyst for stearic acid decarbonylation leads to a significant increase in the catalyst activity and a slight improvement of the heptadecene selectivity. Comparison with the γ-Al 2 O 3 -supported catalyst has been made in terms of the kinetic model based on experimental data. An increase in the catalyst activity is attributed to a decrease in the strength of the active site–reactant adsorption complexes on the basis of the Sabatier–Balandin principle. Relationships between the features of the reaction mechanism, the acidity of the support, and the nanoparticle size of the active substance have been discussed.