Luu Cam Loc

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.

Synthesis of α-MoO3 Thin Sheets and Their Catalytic Behavior for Selective Oxidation of Methanol to Formaldehyde

Abstractα-MoO3 thin sheets were successfully synthesized from all commercial materials using a fast, effective and simple method and characterized by X-ray diffractometer, scanning electron microscopy, IR and Raman spectroscopy. The prepared catalyst was highly active and selective to formaldehyde formation from methanol over a wide range of reaction temperatures comparing to the commercial one. We found that the high selectivity of formaldehyde over the prepared α-MoO3 was originated from its special morphology, which had abundant exposed edges comparing to the commercial α-MoO3. Additionally, the prepared α-MoO3 showed significant stability due to its stable nature.Graphical Abstract

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.

Synthesis of adsorbent with zeolite structure from red mud and rice husk ash and its properties

There are many researches in the modification of red mud as adsorbent for treatment of wastewater or waste gases. Yet, most of them have to face up with a thorny problem caused by remaining alkali in red mud. In this study, the material with zeolite structure was synthesized by fusion method using red mud with the remaining alkali and rice husk ash as raw materials. It comprised alkaline fusion followed by hydrothermal treatment with step – change of synthesis temperature. The synthesized materials were characterized by powder X–ray diffraction (XRD), scanning electron microscopy (SEM), BET and CO2 adsorption capacity. The influences on the quality of these materialswere investigated under various calcination temperatures, calcination times and the ratios of raw materials (based on SiO2/Al2O3 ratio). The optimum reaction parameters were determined. The results depicted that the sample treated at 600 °C for 2 hours with the ratio of SiO2/Al2O3 of 1.8 had the best adsorption capacity and total specific surface area compared with the others.There are many researches in the modification of red mud as adsorbent for treatment of wastewater or waste gases. Yet, most of them have to face up with a thorny problem caused by remaining alkali in red mud. In this study, the material with zeolite structure was synthesized by fusion method using red mud with the remaining alkali and rice husk ash as raw materials. It comprised alkaline fusion followed by hydrothermal treatment with step – change of synthesis temperature. The synthesized materials were characterized by powder X–ray diffraction (XRD), scanning electron microscopy (SEM), BET and CO2 adsorption capacity. The influences on the quality of these materialswere investigated under various calcination temperatures, calcination times and the ratios of raw materials (based on SiO2/Al2O3 ratio). The optimum reaction parameters were determined. The results depicted that the sample treated at 600 °C for 2 hours with the ratio of SiO2/Al2O3 of 1.8 had the best adsorption capacity and total specific surf...

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.

Role of CeO2 promoter in NiO/α-Al2O3 catalyst for dry reforming of methane

A series of Ni/α-Al2O3 (NiAl) catalysts promoted by CeO2 was prepared by co-impregnation methods with content of (NiO+CeO2) being in the range of 10-30 wt%. The NiO:CeO2 weight ratio was fluctuated at 1:1, 1:2 and 1:3. Several techniques, including X-ray powder diffraction (XRD), Hydrogen temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM) were used to investigate catalysts’ physico-chemical properties. The activity of these catalysts in dry reforming of CH4 was investigated at temperature range of 550-800 °C. The results revealed that the most suitable CeO2 promoted Ni catalyst contained 20 wt% of (NiO+CeO2) and NiO:CeO2 weight ratio of 1:2. The best catalytic performance of catalyst [20(1Ni2Ce)Al] due to a better reducibility resulted in a higher amount of free small particle NiO. At 700 °C and CH4:CO2 molar ratio of 1:1, the conversion of CH4 and CO2 on the most suitable CeO2 promoted Ni catalyst reached 86% and 67%, respectively; H2 and CO selectivity of 90% and H2:CO...

Photodegradation of Cinnamic Acid Solution in the Presence of Various Oxidizing Agents on TiO2 and Fe-TiO2 Catalysts

In this paper, TiO2 and Fe-doped TiO2 had been prepared by the sol-gel method. Physico-chemical characteristics of the catalysts were determined by the methods of BET Adsorption, XRD, FT-IR, and UV-Vis spectroscopies. Experimental results showed that the The modification of TiO2 catalyst with Fe led to reducing the crystallite size and PZC, and extending the spectrum of photon absorption to the visible region. The activity of obtained catalysts for photodegradation of cinnamic acid (CA) solution in the presence of various oxidizing agents (O2, O3 and H2O2) was investigated and the optimum reaction conditions were identified. It follows that the addition of Fe additive is able to reduce the optimal catalyst concentration 3-5 times and increase the catalytic activity. It was found that O3 and H2O2 agents showed the higher efficiency for cinnamic acid photodecomposition than usual O2. In optimum conditions, after 90 minutes reaction, the conversion of cinnamic acid in the solution achieved 58.5, 77.7 and 83.1% on TiO2 and 85.7, 82.8 and 89.4% on Fe-TiO2 in the presence of O2, O3 and H2O2 respectively.

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.