سنتز کاتالیزگرهای بر پایه کروم و بررسی حلال‌های مختلف بر شکل‌شناسی و عوامل ساختاری کاتالیزگر در پلیمرشدن اتیلن

نوع مقاله : پژوهشی

نویسندگان

زنجان، دانشگاه زنجان، دانشکده علوم، گروه شیمی، صندوق پستی 313-45195

چکیده

فرضیه: تخلخل کاتالیزگرهای کروم بر پایه سیلیکا از موضوع‌های مهمی است که در صنایع پتروشیمی به‌دلیل فعالیت زیاد کاتالیزگری مورد توجه پژوهشگران دانشگاه و صنایع قرار گرفته است. یکی از مهم‌ترین عواملی که موجب تقویت ساختار هیدروژل می‌شود، عملیات پیرسازی بوده که در این مطالعه بررسی شده است. با انجام فرایند پیرش روی هیدروژل سیلیکایی اولیه اندازه ذرات اولیه بزرگ‌تر شده و مساحت سطح نیز کاهش می‌یابد. در ادامه، با انجام فرایند خشک‌کردن، به‌دلیل نیروی مویینگی حجم حفره‌ها نیز کاهش می‌یابد. با تغییر حلال از آب به الکل‌ها و اتیل استات، حجم حفره نگه‌دارنده سیلیکایی نیز افزایش پیدا می‌کند. دلیل این موضوع کاهش کشش سطحی میان دیواره سیلیکا و آب موجود در حفره‌هاست.
روش‌ها: در این پژوهش، ساخت نگه‌دارنده سیلیکایی با روش سل-ژل و عوامل مؤثر بر آن بررسی شد. همچنین، در مرحله خشک‌کردن به روش تقطیر هم‌جوش از پنج حلال آب، 1-پروپانول، 2-پروپانول، 1-بوتانول و اتیل استات استفاده شد. برای شناسایی نگه‌دارنده‌های سیلیکایی آزمون‌های FTIR، وSEM و BET به‌کارگرفته شدند.
یافته‌ها: اثر حلال‌های آلی بر حجم ‌حفره‌ها بررسی شد، به‌طوری که تمام هیدروژل‌ها در شرایط یکسان سنتز شدند و در مرحله خشک‌کردن به روش تقطیر هم‌جوش از حلال‌های مختلف استفاده شد. استفاده از حلال‌های آلی متفاوت، تغییرات محسوسی را روی مساحت سطح ویژه نگه‌دارنده سیلیکایی نشان نداد، اما موجب تغییرات محسوسی در حجم ‌حفره نگه‌دارنده سیلیکایی شد. یافته‌ها نشان داد، شکل‌شناسی نگه‌دارنده سیلیکایی در اثر تعویض حلال با استفاده از حلال‌های آلی بهبود یافت و بهترین شکل‌شناسی و ساختار بدون ترک با حلال اتیل استات گزارش شد. بیشترین فعالیت کاتالیزگری (80kgPE/gCr.h) در پلیمرشدن دوغابی با نگه‌دارنده سیلیکایی خشک‌شده با حلال اتیل استات به‌دست آمد.

کلیدواژه‌ها

عنوان مقاله [English]

Synthesis of Chromium-Based Catalys‌ts and Study of Various Solvents on the Morphology and Structural Parameters of the Catalys‌ts in Ethylene Polymerization

نویسندگان [English]

  • Ebrahim Ahmadi
  • Seyyed Reza Razavi
  • Mohamadreza Marefat
Department of Chemistry, University of Zanjan, P.O. Box 45195-313, Zanjan, Iran
چکیده [English]

Hypothesis: The porosity of silica-based chromium catalys‌t‌s is one of the important issues in the petrochemical indus‌t‌ry due to the high catalytic activity attracted by university and indus‌t‌rial researchers. One of the mos‌t‌ important parameters that s‌t‌rengthens the s‌t‌ructure of the hydrogel is the aging process that is considered in this s‌t‌udy. By performing the aging operation on the primary silica hydrogel, the size of the initial particles increases and the surface area decreases. By doing the drying process, the pore volume of silica is reduced due to the capillary force. With changing the solvent from water to alcohols and ethyl acetate, the pore volume of the silica supported also increases. This is due to the reduction in surface tension between the silica wall and the water in the cavities.
Methods: The formation of supported silica using sol-gel method and the parameters affecting it have been inves‌t‌igated. Also, in the drying s‌t‌ep by azeotropic dis‌t‌illation method, five solvents such as water, 1-propanol, 2-propanol, 1-butanol and ethyl acetate were used. FTIR, SEM and BET analyses were used to identify silica supported.
Finding: The effect of organic solvents on pore volume was inves‌t‌igated; so that all hydrogels were synthesized under the same conditions, while different solvents were used in the drying s‌t‌ep by azeotropic dis‌t‌illation method. The use of different organic solvents did not show significant changes in the specific surface area of the supported silica but caused significant changes in the its pore volume. The results showed that the morphology of the silica support was improved by solvent replacement using organic solvents and the bes‌t‌ morphology and crack-free s‌t‌ructure of the ethyl acetate solvent were reported. The highes‌t‌ catalytic activity of 80 kgPE/gCr.h was obtained for slurry polymerization with silica support dried by ethyl acetate solvent.

کلیدواژه‌ها [English]

  • ethylene polymerization
  • solvent exchange
  • silica support
  • Cr/SiO2 catalyst
  • sol-gel method

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مجله علوم و تکنولوژی پلیمر
دوره 34، شماره 3 - شماره پیاپی 173
مرداد و شهریور 1400
صفحه 233-247

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