Isomerização do n-Hexano sobre catalisadores Pt/H Modernita.

Abstract

Isomerization reactions of linear alkanes have been creating great interest in the petroleum industry due to its capacity to convert normal paraffins into branched ones. The most used catalysts in isomerization are denominated Afunctional containing acid and metal sites, normally platinum with the function of hydrogenation/dehydrogenation. In this research catalysts were prepared with different contents of platinum supported on Mordenite zeolite, through competitive ionic exchange, utilizing the complex [Pt(NH3)4]Cl2 as precursory material. The catalysts were characterized by TPR (temperature reduction programmed) and submitted to the catalytic evaluation in the isomerization of the n-hexane at 250°C and 1 atm in an atmosphere using molar ratio H2/C6 = 9. Chemical analysis using X ray spectrometry (XDS) showed the incorporation of platinum in the zeolites for all the samples studied (0.3 % ,0.5%, 0.7% and 1% of Pt); and the results of XRD confirmed stability and crystalinity of the zeolites. The profiles TPR of catalysts displayed that the reduction temperature of the metal depends on its localization in the zeolite structure. For all the samples containing platinum the largest temperature of reduction was 540°C in the catalyst containing 0.3% Pt. The results of the catalytic test indicated a diminution of the global activity during the first 40 minutes of reaction and then attained stable values. All the catalysts were more selective in the formation of isomers with high octane number (2-mC5 and 2,3-dmC4) that are the products of greater interest to the petroleum industry. The highest conversion of n-hexane and the best selectivity for mono and bi-ramified in paraffinic compounds was presented by the catalyst 1%Pt/HMordenite. The deactivation of the catalysts during of the n-hexane isomerization demonstrated that the deposited coke on the catalysts practically doesn't vary with the amount of platinum.