ISSN:
1572-9028
Keywords:
NO reduction
;
Rh-MoO3 catalysts
;
automotive catalysts
;
catalyst characterisation (XPS, FTIR of NO, TPRS of NO)]
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Rh-MoO3/Al2O3, Rh/Al2O3 and MoO3/Al2O3 catalysts have been prepared and subjected to various pretreatments including high temperature reduction, high temperature oxidation and oxidation/ reduction cycles. After each series of treatments, surfaces were analysed by XPS and FTIR of adsorbed NO. The effectiveness of these surfaces in dissociating NO was studied by TPRS in the temperature range 300–773 K. Reduction rates of Mo oxides in H2 were determined gravimetrically while rhodium dispersion was determined from H2 adsorption isotherms at 298 K. Results indicate that molybdenum and rhodium exist in close contact in both oxidised and reduced forms. H2 chemisorption was suppressed following HTR of the catalyst due to coverage of rhodium by molybdenum oxide species but this could be reversed by HTO (773 K) followed by low temperature reduction. Although a small proportion of Mo could be reduced following HTR, cycles of HTR/HTO produced Rh/Mo oxide phases in which a proportion of Mo could be reduced to Mo° at 473 K. The presence of reduced Mo would appear to play an important role in the improved performance of Rh-MoO3/Al2O3 catalysts.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01379582
