Wojciech K. Jozwiak

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.

The effect of spinel type support FeAlO3, ZnAl2O4, CrAl3O6 on physicochemical properties of Cu, Ag, Au, Ru supported catalysts for methanol synthesis

The comparative study of the role of binary oxide support on catalyst physico-chemical properties and performance in methanol synthesis were undertaken and the spinel like type structures (ZnAl2O4, FeAlO3, CrAl3O6) were prepared and used as the supports for 5% metal (Cu, Ag, Au, Ru) dispersed catalysts. The monometallic 5% Cu/support and bimetallic 1% Au (or 1% Ru)-5% Cu/support (Al2O3, ZnAl2O4, FeAlO3, CrAl3O6) catalysts were investigated by BET, XRD and TPR methods. Activity tests in methanol synthesis of CO and CO2 mixture hydrogenation were carried out. The order of Cu/support catalysts activity in methanol synthesis: CrAl3O{ia6} > FeAlO3 > ZnAl2O4 is conditioned by their reducibility in hydrogen at low temperature. Gold appeared more efficient than ruthenium in promotion of Cu/support catalysts.

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.

An active phase transformation on surface of Ni-Au/Al2O3 catalyst during partial oxidation of methane to synthesis gas

It was studied the influence of gold addition on physico-chemical properties and catalytic activity of bimetallic Ni-Au/Al2O3 catalyst in partial oxidation of methane (POM). The reduction behavior in hydrogen, XRD crystal structure, XPS spectra and POM catalytic activity were investigated. The reduction of Ni-Au catalyst is a prerequisite condition to catalyze POM reaction. The formation of Ni-Au alloy during high temperature reduction in hydrogen and also in the conditions of POM reaction was experimentally proved. The addition of gold to Ni/Al2O3 system improves catalyst stability and activity in POM reaction.

Catalytic activity and physicochemical properties of Ni-Au/Al3CrO6 system for partial oxidation of methane to synthesis gas

This work is focused on the role of gold and Al3CrO6 support for physicochemical properties, and catalytic activity of supported nickel catalysts in partial oxidation of methane (POM). Catalysts, containing 5% Ni and 5% Ni-2% Au active phases dispersed on mono- (Al2O3, Cr2O3) and bi-oxide Al3CrO6 support, were investigated by TPR, BET and XRD methods, and the activity tests in POM reaction were carried out. Bimetallic Ni-Au catalysts dispersed on Al3CrO6 support remained highly stable and active. The amorphous binary oxide Al3CrO6 can stabilize considerable amount of Cr4+, Cr5+, and Cr6+ species in Ni-Au/Al3CrO6 catalyst network during its calcination in the air. Nickel supported on binary oxide Ni/Al3CrO6 can form Ni(III)CrO3 bi-oxide phase in reductive conditions. During TPR H2 reduction of Ni-Au/Al3CrO6 catalyst chromium(II) oxide Cr(II)O phase is observed. After POM reaction the existence of bimetallic Au-Ni alloy was experimentally confirmed on mono-oxide Al2O3 support surface, but its formation was not identified on bioxide Al3CrO6 support.

Hydroconversion of parafine LTP56-H over nickel/Na-mordenite catalysts

AbstractNickel catalysts supported on Na-mordenite were used for paraffin LTP56-H hydroconversion into liquid material as a possible component for engine fuels. The effects of none-catalytic thermal treatment and catalytic conditions-zeolite type and reaction conditions (solvent) on the process of liquefaction of LTP56-H paraffin and physicochemical properties of catalysts were studied. The physicochemical properties of catalytic systems were investigated using XRD, TPR, TPD-NH3 and SEM-EDS methods.