نقش زئولیت های سلسله مراتبی Y بر عملکرد کاتالیست فرآیند گوگردزدایی هیدروژنی گازوئیل

نوع مقاله : پژوهشی اصیل

نویسندگان

1 دانشکده مهندسی شیمی و نفت، دانشگاه صنعتی شریف، تهران، ایران

2 پژوهشکده توسعه فناوری های کاتالیست،پژوهشگاه صنعت نفت، تهران، ایران

چکیده
موضوع تحقیق:گوگرد­­­­­­­­زدایی‌ هیدروژنی یکی از روش‌های مؤثر برای حذف ترکیبات گوگردی از برش‌های نفتی و ارتقاء کیفیت سوخت‌ می­باشد. یکی از چالش­های عمده در این فرآیند دستیابی به پایه کاتالیست مناسب می­باشد که بهترین عملکرد را داشته باشد. در این میان پایه‌های اصلاح‌شده با زئولیت به دلیل قوی بودن سایت‌های اسیدی، مساحت سطح ویژه و ثبات هیدروترمال و شیمیایی بالا توجه زیادی را به خود اختصاص داده‌اند؛ اما اسیدیته و حجم مزوحفرات زئولیت‌ها نیازمند اصلاح است.

روش تحقیق: در این پژوهش ابتدا زئولیت سلسله مراتبی Y با به­کارگیری روش پسا-سنتز (آلومینیوم زدایی) و با استفاده از فرم آمونیومی زئولیت و محلول NH4F (75/0 مولار) در دمای ºC90 به مدت 3 ساعت تحت شرایط رفلاکس تهیه شد. خصوصیات فیزیکی- شیمیایی زئولیت با آنالیزهای BET, FESEM, FTIR AAS, XRD بررسی شد. زئولیت‌های اصلاح‌شده در سنتز پایه کاتالیست فرآیند HDS بکار گرفته شد. سولفیداسیون و ارزیابی عملکرد کاتالیست‌های تهیه‌شده در سیستم میکرو-راکتوری با خوراک گازوئیل حاصل از واحد آیزوماکس پالایشگاه هدف انجام گرفت.

نتایج اصلی:نتایج نشان می‌دهد که حجم مزوپورها، مساحت سطح ویژه و نسبت SiO2 / Al2O3 در زئولیت سلسله مراتبی به ترتیب به cm3 g-1 073/0، m2 g-136/783 و 2/5 (مقادیر اولیه به ترتیب cm3 g-1 032/0، m2 g-1 18/567 و 5/4) افزایش‌یافته است. همچنین نتایج حاصل از آنالیز زئولیت، حفظ ساختار و میزان بلورینگی طی فرآیند اصلاح زئولیت را اثبات می­کند. اثر اصلاح زئولیت به ویژه تغییرات اسیدیته، مساحت سطح ویژه و حجم مزوحفرات بر فعالیت کاتالیست­های NiMo/Zeolite+Al2O3 مورد ارزیابی قرار گرفت. افزایش اسیدیته و بهبود ویژگی‌های فیزیکی- شیمیایی زئولیت­ اصلاح شده، موجب افزایش عملکرد کاتالیست در فرآیند گوگردزدایی هیدروژنی گازوئیل(Conversion =90%) شده است.. بهبود فعالیت کاتالیست­ها را می‌توان به اثر مثبت زئولیت­ها بر توزیع سایت­های فلزی، مساحت سطح ویژه، اسیدیته و اندازه­ی مطلوب حفرات کاتالیست نسبت داد.

کلیدواژه‌ها

موضوعات


عنوان مقاله English

The role of hierarchical Y zeolites on the catalyst performance of diesel Hydrodesulfurization Process

نویسندگان English

Hamid Karami 1
Mohammad Kazemeini 1
Saeed Soltanali 2
Mehdi Rashidzadeh 2
1 Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran
2 Catalysis Technologies Development Division,Research Institute of Petroleum Industry (RIPI), Tehran, Iran
چکیده English

Research subject: Hydrodesulfurization is one of the effective methods to remove sulfur compounds from oil fractions and improve fuel quality. One of the major challenges in this process is to find the proper catalyst support that performs best. In the meantime, modified supports with zeolite have allocated a lot of attention due to their strong acidic sites, specific surface area and high hydrothermal and chemical stability; But the acidity and volume of zeolite mesopores need to be corrected.

Research approach: In this study, first, hierarchical Y zeolite was prepared using post-synthesis (Dealumination) and using ammonium form of zeolite and NH4F solution (0.75 M) at 90˚C for 3h under reflux conditions. Physicochemical properties of zeolite were investigated by BET, FESEM, FTIR, AAS and XRD analyzes. Modified zeolites were used in the support synthesis of the HDS process catalyst. The sulfidation and performance evaluation of the prepared catalysts were carried out in the fixed-bed microreactor were performed with diesel cutting feed from the Isomax unit of the target refinery.

Main results: The results show that the volume of mesopores, specific surface area and SiO2/Al2O3 ratio in hierarchical zeolites has increased 0.073 cm3 g-1, 783.36 m2 g-1 and 5.2, respectively (initial values are 0.032 cm3 g-1, 567.18 m2 g-1 and 4.5). The results of zeolite analysis show the preservation of the structure and crystallinity during the zeolite modification process. The effect of zeolite modification, especially the Si/Al ratio variations, mesopores and specific surface area, was investigated on the activity of NiMo/Zeolite+Al2O3 catalysts. Increasing the acidity and improving the physicochemical properties of the modified zeolites has increased the catalyst performance in the process of diesel hydrodesulfurization (Conversion= 90%). Improving the activity of catalysts can be attributed to the positive effect of zeolites on the dispersion of the metallic site, surface area, acidity, optimal size of pores and volume of catalyst mesopores.

کلیدواژه‌ها English

Ammonium Fluoride
Post-Synthesis
Hydrodesulfurization
Hierarchical Zeolite
Dealumination
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