در این پژوهش یک سری از کاتالیزورهای Pt/W-Zr-HMS به منظور استفاده در واکنش ریفرمینگ با نسبت‌های مولی متفاوت از Si/Zr تهیه شد و سطح آنها با استفاده از ته‌نشست WO3 اصلاح گردید. کاتالیزورهای تهیه‌شده با استفاده از روش‌های XRD ،NH3–TPD، جذب شیمیایی H2 و جذب نیتروژن شناسایی شد. اثر مقادیر مختلف زیرکونیم بر فعالیت و گزینش‌پذیری در محدوده دمایی C° 500-200 مقایسه گردید. نتایج نشان می‌دهد که با افزایش تلفیق Zr و W در ساختار کاتالیزورهای Pt-HMS، اسیدیته کاتالیزورها بیشتر شده و فعالیت و گزینش‌پذیری کاتالیزوری برای محصولات مطلوب (مخصوصاً محصولات ایزومریزاسیون) با کاهش مقدار Si/Zr (یا افزایش محتوای زیرکونیم) افزایش می‌یابد. طبق نتایج به‌دست‌آمده، کاتالیزورهای مزوحفره فعالیت بالا و گزینش‌پذیری خوبی برای محصولات مطلوب دارند. گزینش‌پذیری بالا برای محصولات موردنظر مخصوصاً ایزومرهای چندشاخه و غیاب بنزن، مزیت اصلی این کاتالیزورهاست. بهترین گزینش‌پذیری i-C7، بر خلاف خواص اسیدیتی، برای Pt/W-Zr(35)-HMS در C°ا200 =T به‌دست آمد.
Effect of zirconium and tungsten mixed oxides on the activity of Pt/HMS catalyst in catalytic reforming reaction of normal heptane
چکیده [English]
A series of Pt/W-Zr-HMS catalysts with different molar ratios of Si/Zr has been prepared and modified their surface by depositing WO3. Then these catalysts were used for reforming reaction. The prepared catalysts were characterized by XRD, NH3–TPD, H2 chemisorption and nitrogen sorption techniques. The effect of various amounts of zirconium on activity and selectivity in temperature range of 200–500°C were compared. The results show that by increasing the incorporation of Zr and W into the Pt-HMS catalysts structure, the acidity of catalysts increases and the catalytic activity and selectivity for desired products (especially isomerization products) increases with decreasing Si/Zr amount (or increasing zirconium content). According to the results, these mesoporous catalysts have high activity and good selectivity for desirable products. High selectivity to desirable products especially multibranched isomers and absence of benzene are the main advantage of these catalysts. The best i-C7 selectivity, contrary to the acidic property, was observed for Pt/W-Zr(35)-HMS at T=200°C.
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