EFFECTS OF NEUTRON AND ULTRAVIOLET IRRADIATION ON THE CATALYTIC ACTIVITY OF MAGNESIUM OXIDE

Abstract

A technique was developed for changing the electronic and defect structure of magnesium oxide catalysts. Relatively small doses of ultraviolet and neutron irradiation were found to enhance the catalytic activity of MgO for the reaction H/sub 2/ + D/sub 2/ in equilibrium 2HD. The enhancement by radiation depends on the extent of degassing of the catalyst prior to irradiation; the less active samples are more sensitive to irradiation. For samples activated at 291 deg , ultravioletirradiated MgO reaches a precise saturation value of catalytic activity, while neutron-irradiated samples continue to increase in activity upon further irradiation. Both types of irradiation produce a large initial increase in activity. Changes in activation energy depend on the thermal activation and type of irradiation. The activation energy either increases or remains unchanged for neutron irradiation, while ultraviolet irradiation does not cause a change. For this system, a simple model based upon Fe/sup 3+/ as the irradiation-induced site was developed. Other possibilities are discussed. It was shown that most of the activity change must be attributed to changes in the electronic structure of the crystal rather than in the number of lattice imperfections.