Ludmila P. Oleksenko

Semiconductor Gas Sensors Based on Pd/SnO2 Nanomaterials for Methane Detection in Air

Semiconductor sensors based on nanosized Pd-containing tin dioxide have been obtained by a sol–gel technique. Semiconductor gas-sensitive materials were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods. Influence of Pd additives on sensitivity of the sensors to methane has been studied. Temperature dependences of electrical resistance in air and sensor response to methane on palladium content for the sensors based on nanosized materials Pd/SnO2 have been investigated.

Adsorption and Catalytic Properties of Co/ZSM-5 Zeolite Catalysts for CO Oxidation

Studies were made of the adsorption and acidic properties, the coordination state of the Co ion in Co2+, Co3+-containing ZSM-5 zeolite systems and the catalytic activity of these zeolites in CO oxidation. A correlation was established between the catalytic activity of these Co-containing zeolites and the number of Brönsted acid sites on the surface and in the system bulk as obtained by different methods. The content of various forms of Co ion coordination states and the ratio of Brönsted to Lewis acidic sites at the surface of the Co-containing zeolites defined their activity in CO oxidation.

Catalysis of the oxidation of hydrogen by a platinum-acetylacetone complex anchored on silica

By binding platinum ions with acetylacetone immobilized on a silica surface, we have obtained a metal complex catalyst containing Pt(II). We have also studied its catalytic activity in the model reaction of oxidation of hydrogen. We have shown that over the course of the catalytic process, this catalyst exhibits high catalytic activity at room temperatures and displays the “surface memory” effect with respect to a previous reaction. The activity of the grafted Pt complex is significantly higher than the activity of a supported platinum catalyst.

Platinum-Containing Adsorption-semiconductor Sensors Based on Nanosized Tin Dioxide for Methane Detection

It was found that platinum-containing adsorption-semiconductor sensors based on nanosized tin dioxide obtained by the sol–gel technique have higher sensitivity to CH4 than analogs known in literature. The sensitivity of the sensors to methane depends on the platinum content of their gas-sensitive layer, and this is explained by influence of the CH4 heterogeneous catalytic oxidation that occurs on the surface of the sensors.

Effect of Palladium Additives on the Functional Characteristics of Semiconductor Hydrogen Sensors Based on Nanosized SnO2

A study was carried out on the effect of palladium additives to nanosized stannic oxide on the electrical resistance in air and hydrogen, sensitivity to H2, and the response and relaxation time of sensors containing the nanosized semiconductor, Pd/SnO2. The introduction of palladium leads to enhanced sensitivity of the sensors to H2 and improved response and recovery time.

Influence of Preparation Conditions of Mixed-valence Con+/ZSM-5 Zeolites on Their Adsorption and Catalytic Properties in CO Oxidation

The adsorption properties, thermal stability and catalytic activity in CO oxidation of Co2+, Co3+-containing ZSM-5 zeolite systems with different metal loadings were studied. Treatment in H2 caused an increase in the activity of Co2+/ZSM-5 and Co2+–Co3+/ZSM-5 systems, but the activity of the Co3+/ZSM-5 system remained unchanged, demonstrating the very low reducibility of the [Co(NH3)6]3+ ion when embedded in the zeolite framework. The catalytic activity changed in the order: Co3+/ZSM-5 < Co2+–Co3+/ZSM-5 < Co2+/ZSM-5. A correlation was established between the temperature necessary for the total decomposition of the cobalt salts introduced into the zeolite, the acidity, the coordination state of the Co ions and the catalytic activity of the cobalt-containing zeolites.

Metal-containing Pd and Cu and bimetallic Pd-Cu catalytic systems based on HZSM-5 zeolite

Palladium- and copper-containing HZSM-5 zeolites with different metal loadings, together with Pd–Cu and Cu–Pd bimetallic zeolite systems, were prepared by ion-exchanging HZSM-5 zeolite with metal–ammine complex cations. The catalytic activity of such materials in CO oxidation was investigated under flowing conditions using various gas mixtures (0.5–2% CO, 20% O2 and 78–79.5% He). The dependence of the activity of the Cu–Pd system on the CO content in the gaseous mixture was observed. The influence of the catalytic properties on the reduction conditions employed for the metal-containing zeolites was investigated. Correlations between the catalytic activity and the intensity of the N–H band in the IR spectra characteristic of the various Pd/Cu–ammine complexes incorporated in the zeolite matrix were demonstrated.

Characteristics of the Oxidation of Carbon Monoxide on Platinum and Palladium Acetylacetonates Immobilized on a Silica Surface

Characteristics of the kinetics of the oxidation of carbon monoxide on acetylacetonates of palladium and platinum immobilized on a silica surface have been studied. The bound metal complexes show no hysteresis in the dependence of the rate of reaction on the concentration of CO and O2 and have a higher catalytic activity than Pt/SiO2 and Pd/SiO2. A mechanism is proposed for the oxidation of carbon monoxide on platinum and palladium complexes bound to a SiO2 surface.

Immobilized Pt complex compounds as catalysts for the oxidation reactions of small molecules

A heterogeneous catalyst for the oxidation of small molecules has been prepared by the immobilization of PtII and PtIV complex compounds on the surface of amorphous macroporous silica. The structure of the surface platinum complex compounds has been established by means of vibrational and electronic spectroscopy while the catalytic activity of the catalyst was investigated for the hydrogen (or carbon monoxide) oxidation reaction by molecular oxygen under mild conditions.