مقایسه روش‌های تلقیح و سل- ژل در سنتز و تعیین خصوصیات فیزیکی و شیمیایی نانوکاتالیست Ni/Al2O3 جهت استفاده در فرآیند ریفورمینگ خشک متان

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی شیمی، دانشگاه صنعتی سهند، شهر جدید سهند، تبریز، ایران/ مرکز تحقیقات راکتور و کاتالیست، دانشگاه صنعتی سهند، شهر جدید سهند، تبریز، ایران

چکیده

مصرف بیوگاز در فرآیند ریفورمینگ خشک متان در حضور کاتالیستی فعال و پایدار، دارای مزایای اقتصادی و محیط زیستی فراوانی است. کاتالیست Ni/Al2O3 علیرغم داشتن فعالیت بالا در ریفورمینگ خشک متان، دارای پایداری ضعیفی در این فرآیند بوده که دلایل آن کک گرفتگی و کلوخه شدن فاز فعال می‌باشد. لذا در این پژوهش تأثیر روش سنتز (تلقیح و سل-ژل) بر خواص فیزیکی-شیمیایی، فعالیت و پایداری کاتالیست Ni/Al2O3 مورد بررسی قرار گرفته است. ارزیابی خواص فیزیکی-شیمیایی نانوکاتالیست‌ها توسط آنالیزهای PSD ،BET ،FTIR FESEM ،XRD و TG-DTG نشان داد، روش سل-ژل سبب تولید فاز آمورف، توزیع یکنواخت نانو ذرات و سطح ویژه بالاتری نسبت به روش تلقیح گردید. آنالیز FTIR حضور گروه‌های عاملی مطلوب بر سطح کاتالیست‌ها و عدم تولید ترکیبات اسپینل را به همراه آنالیز XRD اثبات کرد. آنالیز PSD نشان داد سنتز Ni/Al2O3 به روش سل-ژل ذراتی کوچکتر از nm 60 تولید کرده است. در نتیجه روش سنتز کاتالیست تأثیر بسزایی بر خواص فیزیکی-شیمیایی کاتالیست مانند بلورینگی، مورفولوژی و سطح ویژه کاتالیست‌ها داشته است. عملکرد کاتالیست‌ها با نسبت 1=CO2/CH4ا، l/g.h 24=GHSV و در دمای 550 تا C°850 ارزیابی شد و پایداری آن‌ها در hr 24 و در دمای C° 850 انجام پذیرفت. نتایج نشان دادند، کاتالیست‌های سنتز شده به روش سل-ژل دارای بهترین عملکرد بودند. گاز سنتز با نسبت بسیار نزدیک به یک (99/0) در کاتالیست Ni/Al2O3 تهیه شده به روش سل-ژل به‌دست آمد وکاهش فعالیت آن کمتر از مقدار کاهش در کاتالیست تهیه شده به روش تلقیح بود.
 

کلیدواژه‌ها


عنوان مقاله [English]

A Comparative Synthesis and Physicochemical Characterizations of Ni/Al2O3 Nanocatalyst via Sequential Impregnation and Sol-Gel Methods Used for Dry Reforming of Methane

نویسندگان [English]

  • Mahdi Sharifi
  • Mohammad Haghighi
  • Nader Rahemi
  • Farhad Rahmani
Chemical Engineering Faculty, Sahand University of Technology, Sahand New Town, Tabriz, Iran\Reactor and Catalysis Research Center (RCRC), Sahand University of Technology, Sahand New Town, Tabriz, Iran
چکیده [English]

The use of Biogas as a feed for dry reforming of methane has many environmental and economical advantages. Despite the high activity and low cost of Ni/Al2O3 catalyst, it shows pour stability due to coke deposition and active phase sintering. In this study, the effect of the synthesis method (impregnation vs. sol-gel) was evaluated on (1) physicochemical properties, (2) activity and (3) stability of Ni/Al2O3 catalyst. Extraction of physicochemical properties of nanocatalysts by XRD, FESEM, FTIR, BET, PSD and TG-DTG showed that the sol-gel method produced amorphous phases, uniform nanoparticles´ distribution and a higher surface area in comparison with impregnation method. FTIR analysis confirmed the existence of desired functional groups and lack of spinel compounds which were in agreement with XRD analysis. PSD analysis (< 60 nm) demonstrated the promotion of Ni/Al2O3 catalyst by sol-gel method synthesis. Therefore, it can be found that preparation method had a great influence on physicochemical properties of catalyst; such as, crystallinity, surface area and morphology. The performances of catalysts were evaluated at atmospheric pressure, feed gas ratio of CO2/CH4= 1, GHSV=24 l/g.h and temperature ranges from 550 to 850°C. The stability test also was performed at °850C for 24 h. The results revealed that the synthesized catalyst by sol-gel method had better performances. The excellent syngas ratio (0.99) had been produced only by sol-gel synthesized Ni/Al2O3 nanocatalyst; besides, its activity loss was less than the nanocatalyst synthesized using impregnation method.
 

کلیدواژه‌ها [English]

  • Ni/Al2O3 Nanocatalyst
  • Impregnation
  • Sol-Gel
  • Dry Reforming
  • Synthesis Gas
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