سنتز هیدروترمال یک‏مرحله‏ای غربال مولکولی نانوساختار LaAPSO-34 و توزیع کروم روی آن به‏روش سونوشیمی برای تبدیل اتان به اتیلن در حضور دی‏اکسیدکربن

نوع مقاله: مقاله پژوهشی

نویسندگان

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

چکیده

در این تحقیق هیدروژن‌گیری اتان در حضور دی‏اکسیدکربن روی کاتالیست‌های کروم توزیع‏شده روی SAPO-34 به‏روش سونوشیمی و غربال مولکولی نانوساختار LaAPSO-34، با هدف پی بردن به اثرات ماهیت پایه بر خواص فیزیکی- شیمیایی و عمل‏کردی کاتالیست و بررسی ورود فلز لانتانیوم به آن انجام شد. مانند SAPO-34، غربال مولکولی نانوساختار LaAPSO-34 به‏روش هیدروترمال یک‏مرحله‌ای با موفقیت ساخته شد و آنالیزهای XRDا، FESEMا، FTIRا، BET و EDX این امر را تایید کردند. براساس نتایج خصوصیت‏سنجی، وارد کردن فلز لانتانیوم به داخل ساختار SAPO-34، ضمن تکامل بلورینگی، سبب افزایش سطح ویژه SAPO-34 شد که توزیع بهتر ذرات کروم و مورفولوژی سطحی یک‏نواخت‌تری را به‏دنبال داشت. این خواص سطحی مناسب نانوکاتالیست سنتزی وجود ذرات کروم ردوکسی تثبیت‏شده بیش‏تر روی سطح را، در مقایسه با پایه(0.3) SAPO-34، نوید می‌دهند که به کارایی و پایداری چشم‏گیر نانوکاتالیست(0.3)Cr/LaAPSO-34 می‏انجامند. ارزیابی عمل‏کردی نمونه‌ها بیانگر کارایی قابل‏قبول نانوکاتالیست‌های سنتزی است. با تقویت SAPO-34 با فلز لانتانیوم نیز یک پایه بسیار موثر برای کاتالیست‌های کروم‏بنیان در فرآیند هیدروژن‌گیری اکسایشی ایجاد خواهد شد. مشاهده شد که نانوکاتالیست(0.3)Cr/LaAPSO-34 به‏خوبی اتان را در حضور CO2 و در دمای 700ºC، حتی پس از گذشتhr 5 از انجام واکنش، به اتیلن تبدیل می‌کند و راندمان تولید و انتخاب‌پذیری اتیلن به‏ترتیب 45 و 93% است. واضح است که حساسیت کم‏تر به غیرفعال شدن در طول مسیر انجام واکنش ناشی از اثر هم‌افزایی حضور لانتانیوم و انرژی التراسوند بر بهبود پایداری کاتالیست است.
 

کلیدواژه‌ها


عنوان مقاله [English]

One-Pot Hydrothermal Synthesis of Nanostructured LaAPSO-34 Molecular Sieve and Sono-dispersion of Cr over it Used in Conversion of Ethane to Ethylene in the Presence of Carbon Dioxide

نویسندگان [English]

  • Farhad Rahmani
  • Mohammad Haghighi
Chemical Engineering Faculty, Sahand University of Technology, Sahand New Town, Tabriz
چکیده [English]

Dehydrogenation of ethane to ethylene in the presence of CO2 has been carried out over chromium oxide catalysts sonochemically supported on parent SAPO-34 and nanostructured LaAPSO-34 molecular sieve with the aim of understanding the effects of support nature and La incorporation on the physicochemical properties and performance of catalyst. Like SAPO-34, nanostructured LaAPSO-34 with nominal Si/Al ratio of 0.3 in the gel was successfully synthesized via one-pot hydrothermal method as evidenced by XRD, FESEM, BET, EDX and FTIR techniques. Based on the characterization results, La incorporation into the framework of SAPO-34, not only complete crystallinity of SAPO-34, but increases in the surface area resulted in higher dispersion of Cr species and more uniform surface morphology. This reflects in higher content of redox Cr species stabilized in comparison with parent SAPO-34(0.3), which accounts for superior catalytic performance and stability of Cr/LaAPSO-34 (0.30) nanocatalyst. Moreover, more active sites which have been  attributed to the higher amount of OH groups for La-doped SAPO-34 were proved by FTIR analysis. By employing SAPO-34 supports, a reasonable catalytic performance was observed. Doping SAPO-34(0.3) by lanthanum metal endows a most efficient support applicable for the selective oxidative dehydrogenation process. It was found that Cr/LaAPSO-34(0.3) effectively dehydrogenated ethane to ethylene in the presence of CO2 at °700C even after 5 hrs on-stream operation, giving 45% and 93% ethylene yield and selectivity, respectively. Less sensitivity to deactivation during the course of running the reaction evidently indicated the synergism effect of lanthanum existence and ultrasound irradiation on alleviating the catalyst deactivation in ethane dehydrogenation with CO2.
 

کلیدواژه‌ها [English]

  • LaAPSO-34
  • Chromium
  • Dehydrogenation
  • Ethane
  • Ethylene

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