The Influence of Carrier on the Critical Phenomena in CO Oxidation over NiO

The influence of thermo-exfoliated graphite (TEG) on the catalytic activity of nickel in the CO oxidation process has been investigated. It was shown that nickel supported on the thermo-exfoliated graphite surface was more active catalytically than the bulk metal. Alternate oxidation–reduction on the Ni–NiO phase boundary occurred at temperatures higher than 633 K (Curie temperature of pure nickel). Using a magnetogravimetric method, it was found that the nickel catalyst was transformed by the reaction mixture into a heterophase (Ni/NiO) system both in the presence of a carrier and in its absence. Hence the carrier did not influence the size of the Ni particles. The high catalytic activity of the catalyst supported on graphite may be explained by an increase in the number of Ni particles. Ni/TEG and Ni/NiO samples were studied via X-ray diffraction, Auger spectroscopy and electron microscopy methods

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

The adsorption properties, thermal stability and catalytic activity in CO oxidation of Co 2+ , Co 3+ -containing ZSM-5 zeolite systems with different metal loadings were studied. Treatment in H 2 caused an increase in the activity of Co 2+ /ZSM-5 and Co 2+ –Co 3+ /ZSM-5 systems, but the activity of the Co 3+ /ZSM-5 system remained unchanged, demonstrating the very low reducibility of the [Co(NH 3 ) 6 ] 3+ ion when embedded in the zeolite framework. The catalytic activity changed in the order: Co 3+ /ZSM-5 < Co 2+ –Co 3+ /ZSM-5 < Co 2+ /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

The Structure and Catalytic Activity of Pt Complexes Heterogenized on a Silica Surface

The catalytic activity of complex compounds containing different metal contents immobilized on a silica surface towards the oxidation of carbon monoxide and hydrogen has been investigated. In addition, the influence of the concentration of hydrogen and oxygen and the treatment of such catalysts by the individual components in the reaction mixture on their catalytic activity in the hydrogen oxidation reaction has also been studied. The structural peculiarities of platinum complexes heterogenized on a silica surface have been established by diffuse reflectance electronic spectroscopy

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% O 2 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

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 Co 2 +, Co 3 +-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

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 Pt II and Pt IV 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

The Hydrophobisation of Activated Carbon Surfaces by Organic Functional Groups

A technique of hydrophobic surface design with a high degree of structural homogeneity has been developed for catalytic materials. Mesoporous activated carbons and silica gel were modified by (A) treatment with vinyltrimethoxysilane (vtms) or (B) chlorination with carbon tetrachloride followed by reaction with a Grignard reagent. Evidence for silica gel modification was obtained from FT-IR and 13 C NMR spectroscopy and from elemental analysis. Carbons chemically modified with alkanes and olefins were studied using thermogravimetry (TG) and the results compared with those for the modified silica gel. TG and differential scanning calorimetry (DSC) revealed that the polymerisation of vinyl groups occurred on the carbon surface. The participation of the carrier surface in the initiation of radical processes has been discussed