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Isomerização de n-hexano sobre Pt-NiHUSY empregando zeolita com alto teor de Al
(Universidade Federal de São Carlos, 2005-08-03) Barsi, Fabrício Ventura; Cardoso, Dilson; https://lattes.cnpq.br/2462847535959232
The isomerization reactions of linear alkanes are very important to petrochemical industries due to the isomer products in reaction possess high octane number. The majority of the literature articles involves the job of bifunctional catalysts, in the other words, catalysts containing acid sites and metallic sites. In this work, monometallic (Ni or Pt) and bimetallic (Pt-Ni) bifunctional catalysts were prepared using the USY zeolite (acid sites). The method utilized to disperse the metals in the zeolite was the competitive ion exchange, using its amin complexes [Ni(NH3)6]Cl2 and [Pt(NH3)4]Cl2 as precursors. Three series of catalysts were prepared containg a constant atomic metal: 130, 180, 230 and 280.10-6 atg Me.gcat -1. The catalysts had been characterized by reduction temperature programmed (TPR) and submitted to the catalytic evaluation using the n-hexane isomerization reaction at 250 ºC, 1 atm and a ratio H2/C6 = 9. In the TPR results, a larger reducibility of cations Ni2+ was verified when in presence of Pt, evidenced for the displacement of the peak of reduction to lower temperatures in the monometallic catalysts front to the bimetallic. In the isomerization of n-hexane, the bimetallic catalysts presented a higher activity and selectivity to isomers compared to the monometallic ones, and the stability increased with the content of Pt in the solid. Comparing the monometallic catalysts of Ni and Pt, it was observed that monometallic catalysts of Pt, presents higher activity and lower eactivation. Evaluating the activity in function of the content of Pt, it was observed a maximum for lower content of Pt (about 50%). Above of this content, an addition of Pt leads to the reduction of the initial catalytic activity.
Avaliação de sistema estabilizante para cobertura de cabos aéreos em XLPE
(Universidade Federal de São Carlos, 2005-08-03) Feresin, Fábio; Nascente, Pedro Augusto de Paula; https://lattes.cnpq.br/1387043320265189
Overhead energy lines with covered conductors are increasingly used in the 15 kV distribution systems in Brazil. The advantages are, among others, reduced distances between phases, no disruptions due to conductor clashes, maintained withstand strength when fallen trees touch the line and simple mounting. However, the service reliability of overhead lines with covered conductors in our exposed climate is not quite clarified; normally the specification requirement gives a good performance. When the compounds are formulated to have sunlight and thermal resistance at the same time, because the cables normally work at 90°C conductor temperature, the relationship between both stabilizers becomes very important. The work developed and based on 2² factorial with centroid design taking in account two stabilizers as influent factor to be investigated as well their interactions by measuring the mechanical properties and oxidation temperature. One compound group wereas exposed during eighth thousand hour in weatherometer and the other group, at temperatures of 140°C, 150°C e and 160°C, in the oven. A high performance of the hindered phenol antioxidant was observed during thermo-oxidative degradation and no effectiveness was observed during the photo-oxidative degradation. In the order hand, a great performance of polymeric HALS was observed during photo-oxidation ands a quite good performance was observed as thermal-oxidative stabiliser. An antagonist effect was observed whith this two types of stabilizers used, during photo or thermaloxidative degradations, related with aditives concentrations or rates.