Desenvolvimento de catalisadores à base de Pt, Ni e Ru suportados em zeólitas ZSM-5 mais resistentes a enxofre na aplicação de reforma de naftas ácidas.

Abstract

The aim of this work was based catalysts of Pt, Ni and Ru supported on zeolites ZSM-5 more resistant to sulfur in the application of acidic reforming of naphtha. The catalysts were prepared by competitive ion exchange using zeolite as support for ZSM-5. This material was incorporated metals Ni, Pt and Ru in different combinations (Ni, Pt, Ru, Pt-Ni, Pt-Ru, Ru-Ni and Pt-Ni-Ru), then the samples were dried and calcined at 500 °C, which were characterized by analysis chemistry by x ray spectrophotometer for energy dispersive (EDX), x ray Diffraction (XRD), nitrogen adsorption (BET method) and the Temperature Programmed Reduction (TPR). The tioresistencia, activity and regeneration of metal catalysts were evaluated using the reaction of dehydrogenation of cyclohexane to 1 atm, 300 °C, WHSV = 6.2 h"1 and H2/CH = 14.4. The tioresistencia, poisoning the metal with 50 ul of a mixture of cyclohexane with 1000 ppm of carbon disulfide and measuring the residual activity after poisoning and regeneration conditions in H2 1 hour at 500 °C. Resistance to deactivation by coking was analyzed by the accumulation of carbon deposited after 90min with accelerated deactivation cyclopentane (CP), 500 °C, 1 atm and WSHV = 8 h"1. Through the analysis of X-ray diffraction, it is possible to identify the preservation of the structure of zeolite ZSM-5 after the competitive ion exchange with metals (Ni, Pt, Ru, Pt-Ni, Pt-Ru, Ru-Ni and Pt-Ni-Ru) and calcination. The dispersion of platinum and ruthenium in zeolite ZSM-5, did not modify the textural characteristics of the zeolite, but the dispersion of nickel resulted in a decrease in the values of surface area of the catalysts in relation to the commercial zeolite. The reduction profiles of bimetallic catalysts (Pt-Ni/ZSM-5 and Pt-Ru/ZSM-5) show the influence of platinum in relation to reduction of nickel and ruthenium. The results show that the addition of Ni or Ru not improve tioresistencia Pt hidrogenante but modifies their ability and tolerance to coke. In the accelerated deactivation obtains a deposit and you can eliminate hydrogenated to lower temperature. The higher yield is obtained by adding the aromatic Ni. Coke lighter or hydrogenated obtained by adding Ru.