COMPARISON OF Pt-Sn/γ-Al2O3, Pt-Pb/γ-Al2O3 AND Pt/γ-Al2O3 CATALYSTS IN DEHYDROCYCLIZATION OF n-HEPTANE AT ATMOSPHERIC PRESSURE

Abstract

Twelve catalysts on the basis of Pt/γ-Al2O3 without and with Sn and Pb additives have been obtained and investigated. The content of Pt varied in the range of 0.15 ÷ 0.46 wt.% and the weight ratio of Pt:Sn (Pb) was changed in intervals of 0.75÷2.33 (weight ratio). Physicochemical characteristics of the catalysts were determined by several techniques, including nitrogen physisorption measurements, X-ray powder diffraction (XRD), hydrogen temperatureprogrammed reduction (H2-TPR), hydrogen pulse chemisorption, transmission electron microscopy (TEM) and ammonia thermodesorption). Activity of the catalysts in the dehydrocyclization of n-heptane was studied at the temperature range of 400 ÷ 550oC. Addition of Sn and Pb led to changes in physico-chemical properties of the catalysts that increased the activity of platinum catalysts. It was found that optimal contents of Pt was 0.35 wt.%. and optimal weight ratio Pt: Sn(Pb) was 2.33. The activity of the sample 0.35 wt.%Pt-0.15 wt.%Sn/γ-Al₂O₃ and 0.35 wt.%Pt-0.15 wt.%Pb/γ-Al₂O₃ was found to be higher than that of the non-promoted catalyst more than 1.5 times.