Hydroisomerization of Benzene-Containing Paraffinic Feedstocks over Pt/WO3-ZrO2 Catalysts
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- 作者：Viviana M. Benitez ; Javier M. Grau ; Juan C. Yori ; Carlos L. Pieck ; Carlos R. Vera
- 刊名：Energy & Fuels
- 出版年：2006
- 出版时间：September 2006
- 年：2006
- 卷：20
- 期：5
- 页码：1791 - 1798
- 全文大小：113K
- 年卷期：v.20,no.5(September 2006)
- ISSN：1520-5029
文摘
This report studies the feasibility of carrying out the elimination of benzene contained in paraffinic feedstocks(3-15%) with economy of equipment and sparing of pretreatment steps by hydrogenating benzene tocyclohexane and isomerizing partly the latter to methylcyclopentane in an isomerization reactor loaded witha Pt/WO3-ZrO2 catalyst. The results indicate that the temperature of calcination of the catalysts affects differentlythe acid and metal functions. The hydrogenating capacity of Pt mildly decreases at higher temperatures becauseof an increasing interaction with the support, while the isomerization capacity is enhanced because of thecreation of strong acid sites. The optimum catalyst is the one calcined at 800 
f">C because of the formation ofstrong acid sites at this temperature.With respect to the reaction temperature, there exists a narrow range inwhich both the hydrogenation of benzene and the isomerization of n-paraffins are thermodynamically feasiblewith nonnegligible yield. At 200 f">C, the conversion of benzene is greatly favored but the activity of the acidfunction for the acid-catalyzed reactions, i.e., the ring contraction of cyclohexane and the isomerization ofn-hexane, is too small. At 300 f">C, the acid activity is high but the conversion of benzene is low, even at highpressure, due to thermodynamic reasons. 250 f">C seems to be the best temperature for performing both reactionssimultaneously.The inhibition of the hydrogenolytic activity due to the interaction of Pt with the WO3-ZrO2support suppresses the ring-opening activity of supported Pt; therefore,benzene transforms only into cyclohexaneand methylcyclopentane over Pt/WO3-ZrO2. Addition of Pt/Al2O3 to form a composite catalyst enhances themetal activity and ring-opening products appear. However, this is not considered convenient in this case,because methylcyclopentane has a conveniently high octane number and most ring-opening products havesimilar or lower values.The presence of benzene partly inhibits the conversion of n-hexane because of theadsorption over the strong acid sites of WO3-ZrO2. The selectivity is also modified because of the suppressionof most of the cracking activity.
f">C because of the formation ofstrong acid sites at this temperature.With respect to the reaction temperature, there exists a narrow range inwhich both the hydrogenation of benzene and the isomerization of n-paraffins are thermodynamically feasiblewith nonnegligible yield. At 200 f">C, the conversion of benzene is greatly favored but the activity of the acidfunction for the acid-catalyzed reactions, i.e., the ring contraction of cyclohexane and the isomerization ofn-hexane, is too small. At 300 f">C, the acid activity is high but the conversion of benzene is low, even at highpressure, due to thermodynamic reasons. 250 f">C seems to be the best temperature for performing both reactionssimultaneously.The inhibition of the hydrogenolytic activity due to the interaction of Pt with the WO3-ZrO2support suppresses the ring-opening activity of supported Pt; therefore,benzene transforms only into cyclohexaneand methylcyclopentane over Pt/WO3-ZrO2. Addition of Pt/Al2O3 to form a composite catalyst enhances themetal activity and ring-opening products appear. However, this is not considered convenient in this case,because methylcyclopentane has a conveniently high octane number and most ring-opening products havesimilar or lower values.The presence of benzene partly inhibits the conversion of n-hexane because of theadsorption over the strong acid sites of WO3-ZrO2. The selectivity is also modified because of the suppressionof most of the cracking activity.