In order to create effective oxide catalyst for purification of hydrogen rich gas mixtures of carbon monoxide impurities a systematic study of the influence of chemical nature of the carrier, its texture and structural characteristics on activity and selectivity of modified copper and platinum catalysts in the reaction of selective CO oxidation in excess hydrogen, the chemical composition active phase, the ratio of active ingredients, preparation method and conditions of the reaction activity and selectivity of catalysts carried out.
The fundamental result is the scientific understanding of the impact of expansion of composite systems based on oxide supports, including alumina, titania, mangania and zirconia on their functional characteristics in the catalytic CO oxidation, including prefererntial CO in hydrogen rich gas mixtures, oxidation of hydrogen for synthesis effective catalysts for hydrogen purification processes. The data allowed to establish correlations between catalytic activity and physico-chemical characteristics of catalysts.
The systematic study of the influence of structural and dimensional characteristics of deposited oxide copper-ceria systems on their catalytic properties in oxidation of CO and hydrogen, including prefererntial CO oxidation in hydrogen rich gas mixtures revealed that:
• copper-containing catalysts can be divided into two groups: low-temperature catalysts on alumina and zirconia and a high temperature on manganese dioxide and titania;
• copper-ceria-containing catalytic system deposited on industrial zirconia, characterized by higher rates of conversion and selectivity, are perspective for development of effective contacts for purification of hydrogen at low temperatures;
• active phase of copper-cerium-zirconium catalyst is finely dispersed copper oxide phase; it connected with ceria and zirconia through the surface phase interaction;
• to ensure high activity of copper-cerium-zirconium catalysts in the preferential CO oxidation is necessary a certain ratio of ceria, zirconia, copper and its oxide, and interaction of fine copper oxide with cerium and zirconium dioxide;
• Catalytic activity of oxide copper-cerium-zirconium catalysts for CO oxidation, including preferential oxidation depends on the presence of defects in the structure of cerium dioxide, which is applied to the active ingredient;
• size of particles deposited components, copper and cerium oxide is independent of particle size and specific surface of the support, but is determined by the method of catalyst synthesis.
• Promoting monoclinic zirconia by additions of germanium dioxide greatly increases its catalytic activity in CO oxidation in excess oxygen, allowing to lower the temperature reaching
100%- conversion in the 150-180 ºC;
• introduction to monoclinic zirconia of niobium oxide impurities, in contrast, raises the temperature reaching 100% conversion- up to 50 º. Multicomponent copper-cerium catalysts, which were obtained based on modified supports, show high selectivity, providing the prefererntial CO oxidation at 130 º C, but rates of CO conversion in reducive environment do not exceed similar results were obtained in monoclinic zirconia.
The practical result of the project was the development of copper-containing oxide catalyst for hydrogen purification from CO by its preferential oxidation and practical recommendations for their use. Long term test of catalysts have found their
stability and the prospects for further implementation.
Keywords: preferential CO oxidation, hydrogen oxidation, copper-cerium-zirconium catalysts, X-ray analysis, zirconia X-ray analysis, zirconia.