Catalytic activity of Pt-Re-Pb/Al2O3 naphtha reforming catalysts

MARÍA A. SÁNCHEZ; VANINA A. MAZZIERI; JAVIER M. GRAU; JUAN C. YORI; CARLOS L. PIECK

JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY

JOHN WILEY & SONS LTD

Año: 2011 vol. 86 p. 1198 - 1204

0268-2575

BACKGROUND: The main purpose of the naphtha reforming process is to obtain high octane naphtha, aromatic compounds and hydrogen.  The catalysts are bifunctional in nature, having both acid and metal sites.  The metal function is supplied by metal particles (Pt with promoters such as Re, Ge, Sn, etc.) deposited on the support.  The influence of the addition of Pb to Pt-Re/Al2O3 naphtha reforming catalysts was studied in this work.  The catalysts were prepared by co-impregnation and characterized by means of temperature programmed reduction, thermal programmed desorption of pyridine and several test reactions such as cyclohexane dehydrogenation, cyclopentane hydrogenolysis and n-heptane reforming. RESULTS: It was found that Pb interacts strongly with the (Pt-Re) active phase resulting in a decay of the metal function activity.  Hydrogenolysis is more affected than dehydrogenation.  Part of the Pb is deposited over the support decreasing its acidity and the strength of the most acidic sites.  CONCLUSION: The n-heptane reforming reaction shows that Pb modifies the stability and the selectivity of the Pt-Re catalysts.  Small Pb additions increase the stability and greatly improve the selectivity to C7 isomers and aromatics with decreased formation of low value products like methane and gases.