A NUCLEAR MICROPROBE EXAMINATION OF CATALYSTS USED IN HYDROTREATING AND HYDROCONVERSION OF PETROLEUM FRACTIONS

Nuclear microprobe methods have been developed to measure light elemen t and metallic poison distributions in used catalysts. The methods are based on the irradiation of sectioned catalyst pellets with microbeam s of energetic (MeV) charged particles. Irradiation with deuterons all ows the determination of carbon and nitrogen by nuclear reactions, and vanadium, nickel, and other elements with atomic number >12 by partic le-induced X-ray emissions. Hydrogen can be determined by an elastic r ecoil analysis method based on irradiation with helium ions. The devel opment of the methods for catalyst applications is described. All elem ents can be determined at concentrations of <0.1 wt% at spatial resolu tions as high as 5 mu m. The methods have been applied to examine hydr otreating and hydroconversion catalysts used to treat heavy petroleum fractions. The extent of intra- and interpellet variations in deposite d elements has been found to be high, but statistically acceptable ave rage distributions can be obtained by examining no less than five pell ets per batch. The interrelationship between deposited elements has be en examined. An observation is that the H/C atom ratio of coke falls i n regions of pellets containing high concentrations of vanadium. Early work indicates that nitrogen compounds tend to form coke nearer the s urface of pellets than hydrocarbons. Information has been obtained on pore filling. (C) 1995 Academic Press, Inc.