J. Góralski

Physico-Chemical and Catalytic Study of the Co/SiO2 Catalysts

This paper is focused on the physico-chemical and catalytic properties of Co/SiO2 catalysts. Silica-supported cobalt catalysts were prepared by sol-gel and impregnation methods and characterized by BET measurements, temperature programmed reduction (TPRH2), X-ray diffraction (XRD), and thermogravimetry-mass spectroscopy (TG-DTA-MS). The sol-gel method of preparation leads to metal/support catalyst precursor with a homogenous distribution of metal ions into bulk silica network or on its surface. After drying the catalysts were calcined at 500, 700, and 900°C. The reducibility of the supported metal oxide phases in hydrogen was determined by TPR measurements. The influence of high temperature—atmosphere treatment on the phase composition of Co/SiO2 catalysts was investigated by XRD and TG-DTA-MS methods. At least five crystallographic cobalt phases may exist on silica: metallic Co, CoO, Co3O4 , and two different forms of Co2SiO4 cobalt silicate. Those catalysts in which cobalt was chemically bonded with silica show worse reducibility as a result of strongly bonded Co-O-Si species formed during high-temperature oxidation. The TPR measurements show that a gradual increase in the oxidation temperature (500–900°C) leads to a decrease in low-temperature hydrogen reduction effects (<600°C). The decrease of cobalt oxide reduction degree is caused by cobalt silicate formation during the oxidation at high temperature (T ≤ 1000°C). The catalysts were tested by the reforming of methane by carbon dioxide and methanation of CO2 reactions.

Chemisortion method for the determination and removal of trace amounts of oxygen in unreactive gases

Summary An effective purification of carrier gas from trace amounts of oxygen and a simple determination of trace amounts of oxygen in unreactive gases have been achieved with the use of the catalysts Pt/γ-Al203 and Pd/γAl2O3.

Reduction requirements for Ru(Na)/Fe2O3 catalytic activity in water-gas shift reaction

This paper is focused upon the influence of potassium on the reduction behavior and catalytic properties of Fe2O3, Ru/Fe2O3 and Ru/(K)Fe2O3 catalysts for the water gas shift (WGS) reaction. The effect of promotion by potassium is attributed to stabilization of a highly dispersed ruthenium phase on the iron oxide surface. The hydrogen reduction behavior of Fe2O3 catalysts is strongly influenced by time-pressure dependent processes and comprises two or three heavily overlapped TPR peaks which can be ascribed to the following stages of the iron(III) oxide reduction 3Fe2O3 → 2Fe3O4 → 6FeO → 6Fe. The appearance of FeO as an intermediate phase was confirmed by XRD. The presence of ruthenium(IV) oxide substantially changes the kinetics of the reduction process. In the case of potassium-doped catalysts, the reduction of Fe2O3 is substantially different and is assigned to the reduction phase of KFeO2. Both ruthenium and potassium have a promoting effect on the catalytic activity for the WGS reaction.

Temperature-programmed reduction and oxidation of bimetallic catalysts Rh−Ag/Al2O3

Investigations of temperature-programmed reduction and oxidation of bimetallic catalysts Rh−Al2O3 seem to indicate that there are no strong interactions between rhodium and silver. Bimetallic catalysts rather show the additive properties of individual components, i. e. rhodium and silver.AbstractИсследования температурно-программированного восстановления или окисления биметаллических катализаторов Rh−Al/Al2O3 указывают на отсутствие сильного взаимодействия между родием и серебром. Биметаллические катализаторы скорее обладают аддитивными свойствами индивидуальных компонентов, а именно родия и серебра.

Time-of-flight secondary ion-mass spectrometry as a new technique for the investigations of the deactivation process of hydrodechlorination catalysts

Time-of-flight secondary ion-mass spectrometry (ToF-SIMS) was applied to investigations of the deactivation process of hydrodechlorination catalysts. It appeared that, owing to the use of the ToF-SIMS technique, simultaneous monitoring of various reasons for catalyst deactivation was possible in one measurement. As a model catalyst, the Pd/Al2O3 sample was chosen. ToF-SIMS studies revealed an increase in the amount of Cl and PdCl2 on the catalyst surface during the hydrodechlorination reaction. Moreover, a drop in the quantity of surface-accessible Pd was observed.

Interaction of oxygen and hydrogen with platinum in pulse gas chromatography

Abstract The interaction of oxygen and hydrogen with the surfaces of platinum black, platinum-silica and platinum-alumina catalysts within the temperature range 196–970°K was examined by pulse gas chromatography. Chemisorption of oxygen and hydrogen was carried out on a “clean” platinum surface and titrations of the oxidized surface with hydrogen were performed together with those of the reverse reaction, i.e., titration of the reduced surface with oxygen. We were able to define the extent of slow, reversible hydrogen sorption within a wide temperature range, desorption of oxygen from the platinum surface and the formation of an oxide multilayer at higher temperatures. The results indicate that the stoichiometries of the surface interactions between platinum and oxygen and between platinum and irreversibly chemisorbed hydrogen are the same and approximate to unity: O/Pt2 ≈ H/Pt5 ≈ 1. The temperature range 300–570°K is suitable for determining platinum dispersions by means of oxygen and hydrogen chemisorption.

Characteristic of physicochemical properties of Pd/MgO catalysts used in the hydrodechlorination process with CCI4

Characteristic of physicochemical properties of Pd/MgO catalysts used in the hydrodechlorination process with CCI4 The aim of this paper was to investigate the physicochemical properties of palladium catalyst containing basic support MgO which was used in hydrodechlorination reaction with carbon tetrachloride. In order to characterize the investigated sample the catalyst was put to tests of XRD, TOF - SIMS, TG-DTA-MS and TPRH2 measurements, activity tests were also performed. The XRD and TPR results demonstrated the presence of PdOxCly species whose decomposition takes place above 700°C. The calcination of the Pd/MgO catalyst at 700°C resulted in the transformation of PdOxCly to PdO.

Studies on TiO2/SiO2 and Pd/TiO2/SiO2 Catalysts in Photoreduction of CO2 with H2O to Methanol

The development of industry induced a massive increase in the emission of carbon dioxide into the atmosphere. A large amount of CO2 and its general availability causes that it could be a cheap reactant in a reaction that runs in a way similar to photosynthesis in plants. Pure TiO2 and metal doped TiO2 are the most studied semiconductor catalysts for photoreduction of CO2. The TiO2/SiO2 and Pd/TiO2/SiO2 catalysts were prepared and studied by temperature-programmed desorption, X-ray diffraction analysis, SEM-EDS, temperature-programmed reduction and then used for the methanol synthesis. The photoactivity of Pd/TiO2/SiO2 catalysts in the reduction of CO2 with H2O was tested at room temperature using photoreactor equipped with 16 lamps. The wavelength was characteristic of near ultraviolet. Post-reaction products were identified with gas chromatograph equipped with the flame ionization detector. Pd doping made the catalysts photoactive and the photoactivity of catalysts was changing as follows: 1%Pd/5%TiO2/SiO2 > 1% Pd/10% TiO2/SiO2 > 1% Pd/15% TiO2/SiO2. Optimum ultraviolet radiation time in the photoreduction of CO2 to methanol was 7 h. An addition of Pd does not change the surface of the carrier.

Effect of water on the desorption of carbon dioxide from the surface of alumina

Based on investigations of temperature-programmed desorption of CO2 from γ-Al2O3 surface, three forms of CO2 adsorption differing considerably in quantitative contributions and temperature ranges of desorption have been distinguished. A significant inhibiting influence of water on CO2 adsorption has been observed. Water adsorption results in gradual blocking of high and medium-energy adsorptive centers of CO2 on γ-Al2O3.AbstractНа основе исследований температурно-программированно и десорбции CO2 с поверхности γ-Al2O3 были различены три формы адсорбции CO2, отличающиеся по количественным вкладам и температурным интервалам десорбции. Наблюдалось существенное ингибирующее влияние влияние воды на адсорбцию CO2. Адсорбция воды приводит к последовательному блокированию адсорбционных центров CO2 на Al2O3 с высокой и низкой энергией.

Chemisorption of H2, O2 and CO on bimetallic catalysts Rh−Ag/Al2O3

Comparison of adsorptive properties of Rh−Al2O3 catalysts in relation to H2, O2 and CO as adsorbates points to different surface interactions between the adsorbates and metallic surface of the catalysts. The differences may result from the changing composition of bimetal surface in relation to the catalyst composition and/or from the changing stoichiometry of surface interactions of the adsorbates.AbstractСравнение адсорбционных свойств H2, O2 и CO на катализаторах Rh−Ag/Al2O3 указывает на различный на различный характер поверхностных взаимодействий между адсорбатами и металлической поверхностыо катализатора. Разница вероятно вызвана изменением состава поверхности биметалла, в смысле состава катализатора, и (или) изменением стехиометрии поверхностных взаимодействий адсорбатов.