Resumo

RAMIREZ, Sergio; SCHACHT, Persi  e  ANCHEYTA, Jorge. Effect of Support Acidity on n-heptane Reforming over Pt/Beta zeolite+γAlumina Catalysts. J. Mex. Chem. Soc [online]. 2005, vol.49, n.3, pp.271-278. ISSN 1870-249X.

Platinum supported on beta zeolite+gamma alumina catalysts were synthesized in this work. The catalysts were prepared with Pt supported on mixtures of beta zeolite and alumina with different contents of zeolite in the final support, and with beta zeolite previously exchanged with lithium and cesium cations and mixed with alumina. Supports and catalysts were characterized by atomic absorption spectrometry, X-ray diffraction, nitrogen adsorption, FTIR of pyridine and CO adsorption, hydrogen chemisorption and NH₃ TPD. Results of supports characterization show values between the properties of raw materials and reveal that they have a uniform composition without destruction of the crystalline structures of beta zeolite and alumina. Activity of catalysts was evaluated in a glass reactor at 663 K and atmospheric pressure. Reforming of n-heptane was used as reaction test. Variations in the products selectivity of platinum supported catalysts were related to the composition of the support and the neutralization of the zeolite. These variations were attributed to the modification in the electronic properties of the supported platinum that affects the force and duration of the adsorbed hydrocarbon bond. The CO adsorption FTIR spectra also suggest the possibility of modifications in the morphology of the particles of supported platinum that may contribute to the changes in product selectivity.

Palavras-chave : Beta zeolite; alumina; reforming; lithium; cesium.