Ho Si Thoang

Kinetics of carbon monoxide methanation on nickel catalysts

The kinetics of CO methanation in excess H2 on CaO- and CeO2-doped nickel catalysts supported on Al2O3 and TiO2 was studied at atmospheric pressure in a temperature range of 180–240°C. It was found that the same rational fractional rate equation corresponding to the reaction taking place at high surface coverages, is valid for all of the catalysts. The activity of nickel catalysts in the methanation reaction and their adsorption capacity with respect to reaction mixture components depend on the nature of the support and dopants.

Reaction mechanism of CO methanation on nickel catalysts, as studied by isotopic and nonstationary methods

Kinetic isotope effects were measured upon the replacement of hydrogen by deuterium in the reaction of carbon monoxide methanation on nickel catalysts supported on TiO2 and γ-Al2O3. Data on the mechanism of the process were obtained with the use of a nonstationary method. A step-scheme was proposed, in which the interaction of oxygen-containing compounds with hydrogen is a slow step of the process.

A study on the properties of modified CuO samples and the kinetics of carbon monoxide oxidation over the given catalysts

Three catalyst samples 10 wt% CuO/γ-Al2O3 (CuAl), 10 wt%CuO + 10 wt% Cr2O3/γ-Al2O3 (CuCrAl) and 10 wt%CuO + 20 wt% CeO2/γ-Al2O3 (CuCeAl) have been taken for the study. Physico-chemical characteristics of the catalysts were determined by the methods of BET adsorption, X-ray diffraction and temperature-programmed reduction. Due to a strong interaction of CuO with Al2O3, resulting in the formation of copper aluminate the catalytic activity of CuO/γ-Al2O3 has been reduced. The bi-oxide catalyst CuCrAl was more active than CuAl, thanks to the formation of high catalytically active spinel CuCr2O4. The fact of very high activity of the CuCeAl sample can be explained by the presence of the catalytically active form CuO–CeO2–Al2O3. The kinetics of CO oxidation reaction on the given catalysts was studied at the temperature range between 200°C and 270°C. The values of initial partial pressures of carbon monoxide ( ), oxygen ( ) and carbon dioxide ( ) were varied in ranges (hPa): 10 ÷ 45; 33 ÷ 100 and 0 ÷ 30, respectively. It has been found that on all the catalysts, the common kinetic equation for the reaction was as follows: where r is the reaction rate, k is the reaction constant, and k 2 and k 3 are the O2 and CO2 adsorption constants, respectively. In the case of CuAl and CuCrAl, k 3 = 0, and since  ≫ 1, the equation should become r = k.P CO.

Kinetics of the total oxidation of para-xylene and its mixtures with carbon monoxide over supported copper catalysts

The kinetics of the total oxidation of para-xylene and its mixtures with CO over alumina-supported copper catalysts has been investigated at atmospheric pressure in the temperature range from 200 to 270°C. The reactions over the catalysts 10%CuO/γ-Al2O3 and (10%CuO + 20%CeO2)/γ-Al2O3 obey the same kinetic equations in fractional rational form. These equations imply that the reactions occur at medium surface coverages of adsorbed substances and differ only in numerical values of constants. The simultaneous oxidation of para-xylene and CO reveals a complicated mutual influence associated with the formation of new intermediates inducing a change in the kinetics of the process.

Mechanism of carbon monoxide oxidation on supported copper catalysts modified with cerium and platinum

The mechanism of CO oxidation on copper oxide catalysts without additives and with cerium and platinum additives supported on γ-Al2O3 was studied. It was found that the presence of Ce and Pt facilitated the reduction of copper and increased the activity of the catalysts. It was established that the parent substances participated in the reaction from an adsorbed state; in this case, the surface coverage of all of the catalysts with oxygen was greater than the coverage with CO, and the reaction system components exhibited different adsorption capacity. The introduction of Ce increases the bond strength of CO with the surface and weakens the bond of oxygen with the surface. The presence of Pt increases the bond strengths of CO, O2, and CO2 with the surface.