Analytical chemist's approach to heterogeneous catalysis. Gas chromatographic–mass spectrometric characterization of polycyclic aromatic hydrocarbons as a fingerprint of active sites in hydrocarbon-reforming catalysts

Abstract

The analytical GC–MS characterization of polycyclic aromatic hydrocarbons (PAHs), formed as by-products in the model reaction of methylcyclopentane reforming, is proposed as a convenient tool for fingerprinting the nature of active sites in heterogeneous catalysts. The by-products obtained with non-acidic Pt/KL and Pt/NaY catalysts (platinum particles inside zeolite cages) were characterized as 2–4 condensed-ring PAHs. The distribution and the structure of such by-products were demonstrated to be related to the geometry of the zeolite framework. With acid catalysts, families of isomers of all the polymethyl-derivatives of three- and four-ring aromatics were obtained. Careful analyses of total-ion GC profiles via single-ion monitoring allowed the identification of each family of isomers.