Gizela A. Lomić

Structural and textural properties of the NiOAl2O3 catalyst

Influence of nickel oxide loading (5; 10; 20 wt% Ni) and temperature of heat treatment (400, 700, 1100°C) on the structure, texture and reducibility of coprecipitated NiOAl2O3 catalyst was investigated. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), low temperature nitrogen adsorption (LTNA) and hydrogen reduction confirmed significant changes in physico-chemical properties as the function of mentioned variables. The results showed that the interactions in coprecipitated NiOAl2O3 system are intensive even at 400°C. At 700°C the observed interactions in coprecipitated NiOAl2O3 system are surface area, reducibility and the coordination of Ni(II), while at 1100°C treatment intensive structural and textural changes were registered.

Deactivation of industrial hydrotreating catalyst for middle petroleum fractions processing

Representative samples of regenerated hydrotreating NiO-MoO3/Al2O3 catalyst were investigated in order to define the main reasons for activity decline, observed after restarting the industrial reactor. By complex structural and textural characterization, followed by surface chemical analysis, it was shown that pronounced sintering and structural changes take place in a fraction of Catalyst bed, particularly in the upper layer. The intermediary presence of MoO3 in the liquid phase was assumed to be the cause of the intensive sintering during regeneration, which was followed by loss of active component. Restructuring and segregation of the active phase in hot spots, resulting from blocking of a part of the catalyst bed, are supposed to be the main causes for changes taking place later on during regeneration.

ACCELERATED POLYMORPHIC TRANSFORMATIONS OF ALUMINA

In binary systems MeO/Al2O3 (Me=Mg, Zn, Cu), the accelerated polymorphic transformation of alumina to α-Al2O3 was observed in the presence of Cu2+. The phenomenon is explained as catalytic, considering the Cu2+ electron configuration and Jahn-Teller effect.

Controlled re-oxidation of low-pressure methanol synthesis catalyst, followed by means of DSC

The re-oxidation of low-pressure methanol synthesis catalyst was followed by means of DSC, with the aim of contributing to a better understanding of the processes taking place during catalyst blanketing, stabilization and re-oxidation. The investigations were carried out with previously hydrogen-reduced samples, and their successive re-oxidation was performed with different oxygen contents in the oxygen/nitrogen gas mixtures. A procedure for catalyst stabilization and/or catalyst discharge is proposed.ZusammenfassungAls Beitrag zum besseren Verständnis der Vorgänge während Katalysator-Blanketing,-Stabilisation und-Reoxidation wurde mittels DSC die Reoxidation des Niedrigdruck-Katalysators für die Methanolsynthese verfolgt. Die Untersuchungen wurden mit zuvor wasserstoffreduzierten Proben durchgeführt, die anschließende Reoxidation hingegen mit Sauerstoff/Stickstoff-Gasgemischen unterschiedlichen Sauerstoffgehaltes. Es wird eine Methode zur Katalysatorenstabilisation und/oder zur Katalysatorenbeseitigung vorgeschlagen.