Temperature-programmed reduction of metal-contaminated fluid catalytic cracking (FCC) catalysts

Abstract

A temperature-programmed reduction study of equilibrium fluid catalytic cracking (FCC) catalysts has shown three hydrogen-consumption peaks associated with contaminanted metals. A low-temperature peak, located near 510 °C, is produced by the reduction of several components in the catalyst. Highly-dispersed vanadium contributes to this peak. A high-temperature peak, located near 800 °C, is produced by reduction of nickel aluminate or nickel silicate compounds. A linear relationship exists between the area of the high-temperature peak and nickel concentration on equilibrium catalysts. An intermediate-temperature peak, located near 690 °C, appears to be related to some form of vanadium compound. The intermediate-temperature peak does not occur on low-vanadium-concentration equilibrium catalysts, but is observed at higher vanadium-contamination levels. The presence of the 690 °C peak was found by deconvoluting hydrogen-consumption data. The existence of this intermediate-temperature peak was proven by external reduction of highly-contaminated equilibrium catalyst at 500 and 700 °C. External reduction at 500 °C removes the low-temperature peak from the temperature-programmed reduction (TPR) spectrum. External reduction at 700 °C removes both the low-temperature and intermediate-temperature peaks from the TPR spectrum. The difference in spectrum between calcined and 700 °C reduced samples shows a clear spectrum with only the low and intermediate-temperature peaks present.