E. Kis

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.

Effects of the method of preparation of MgC2O4 as a support precursor on the properties of iron/magnesium oxide catalysts

Abstract Samples of iron/magnesium oxide catalyst in which magnesium oxalate was used as a common support precursor were prepared alternatively from magnesium nitrate (N) and from magnesium acetate (A) and were tested in hydrocarbon synthesis. Sample N showed the higher activity by one order of magnitude while sample A showed better initial selectivity towards alkenes and a slower initial deactivation. BET, X-ray diffraction (XRD), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and Mossbauer spectroscopy analysis revealed different methods for the formation of the catalyst in all the stages of preparation. Lower activity of sample A was explained by hindered reducibility of the iron component, due to the fact that support effects were affected by individual properties of the support precursor parent materials, as well as by the preparation conditions which they imposed.

Acid Sites in HZSM‐5 Upon Copper Exchange by FTIR and DSC Using Ammonia

The acidity of the parent HZSM-5 zeolite and Cu-HZSM-5 catalyst has been examined by FTIR and DSC using ammonia desorption. Sites of different strength were found in HZSM-5, desorbing ammonia at a relative temperature difference of about 100 °C. Upon copper exchange a fraction of Bronsted sites were transformed to Lewis sites, but the acid strength of the remaining Bronsted sites was increased. Aside from Lewis sites originating from copper exchange, there might be some additional sites formed from precipitated copper. This could explain the quantity of adsorbed NH3 on Cu-ZSM-5 which is higher than theoretically expected. While changing their nature, acid sites of higher strength keep their location, which is manifested by some diffusion effect towards ammonia.

Promoter Effects of Ca, Mo, Al, ON Fe/MgO Catalyst on CO Hydrogenation

Abstract Fe/MgO catalysts were promoted by CaO, Al 2 O 3 and molibdena and the FT reaction was investigated. It was established that molybdena can be reduced during the reaction, alumina can form various phases either with magnesia or with iron oxide, while calcium oxide proved to be a fully inert promoter. Formation of alcohols started at a later stage of the reaction and the process probably proceeds on a metal/carbide/oxide interphase.

Promoter effect of Cu, Co and K on Fe/MgO in CO hydrogenation

Abstract Promoter effects of Cu, Co and K on Fe/MgO catalysts in CO hydrogenation have been investigated. The catalytic activity and selectivity are related to the physical properties and to the state of iron observed by XRD and Mossbauer spectroscopy. The activity increase upon Cu and Co promotion is explained by different promoter-metal interactions. Decreased activity of the potassium-promoted catalyst is related to the enhanced carbonization of iron under the reaction conditions. Enhanced selectivity towards alcohols on all three promoted catalysts is attributed to new active sites generated during the initial period of the reaction and located at the interface between the different iron species and the support.

The effects of the architecture of the Ziegler-Natta catalyst on the morphology of polypropylene

Abstract The study of replication effects in propylene polymerization by TiCl3 Ziegler-Natta catalysts is made by comparison of optical microscope (OM) and scanning electron microscope (SEM) pictures of the catalyst and the polymer, obtained either in standard conditions or in absence of hydrogen, with corresponding values of “calculated” replication factor (Rc) and “found” replication factor (Rf). It has been shown that under given conditions replication is evident both in structure and substructure details; it is not influenced noticeably by polymerization pressure, but may depend on the time of polymerization in a way dependent on the architecture of the catalyst.

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.

Spinel-type structure of Co in conditions of HDS catalyst aging

Abstract The structural investigation of CoO–MoO 3 / γ -Al 2 O 3 HDS catalystassumed to accelerate aging in laboratory conditions followed by the DRS method pointed out the surface spinel formation The amount of spinel structure formed increased with increasing temperature and decreased with the treatment atmosphere in the order: nitrogen>air>steam On the basis of the experimental data of electronic d–d transitions of Co (II) ion in a catalyst treated in nitrogen atmosphere the parameter of the crystal-field splitting 10 D q and the energies of the electronic state of Co (II) in a spinel-type structure were calculated The most probable scheme of the molecular orbital has been proposed.

Deactivation studies on NiO-MoO3/Al2O3 and CoO-MoO3/Al2O3hydrodesulphurization catalysts

The results of comparative investigation of NiO-MoO 3 /γ-Al 2 O 3 hydrodesulphurization (HDS) catalyst deactivation in industrial plant and laboratory conditions are presented. Structural (XRD, DRS, XPS), textural (LTNA) and morphological (SEM) characteristics were followed depending on temperature, time of treatment and the atmosphere of regeneration. Based on the mathematical models the of textural changes intensity depending on two independent variables (time, temperature) the role of these variables in catalyst sintering were estimated. The mechanism of deactivation process is proposed, pointing out critical conditions in processing and/or regeneration. Parallel investigation of CoO-MoO 3 /γ-Al 2 O 3 catalyst was the basis for relative stability estimation depending on the precursor type.

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.