اثر نسبت Si/Al روی خواص فیزیکی – شیمیایی LaAPSO-34 نانوساختار جهت استفاده در تبدیل متانول به الفینهای سبک
محورهای موضوعی : فصلنامه علمی - پژوهشی مواد نوین
ابوالفضل آموزگار
1
(کارشناس ارشد، دانشکده مهندسی شیمی، دانشگاه صنعتی سهند، شهر جدید سهند، تبریز، ایران.)
محمد حقیقی
2
(مرکز تحقیقات راکتور و کاتالیست، دانشگاه صنعتی سهند، شهر جدید سهند، تبریز، ایران.)
کلید واژه: LaAPSO-34, اثر Si/Al, متانول, الفینهای سبک, MTO,
چکیده مقاله :
نسبت Si/Al از جمله پارامترهای موثر بر خواص فیزیکی-شیمیایی کاتالیستهای نانوساختار LaAPSO-34 می باشد. استفاده از نسبت بهینه Si/Al در این غربال مولکولی کارایی آنها را تا حدچشمگیری در فرایند تبدیل متانول به الفینهای سبک افزایش داده است. کاتالیستهای نانوساختار LaAPSO-34 با نسبتهای گوناگون Si/Al به روش هیدروترمال سنتز و با آنالیزهایXRD، FESEM، EDX، BET و FTIR تعیین خصوصیات شدند. نتایج آنالیز XRD نشان دادند که در نسبتهای پایین Si/Al شبکه کریستالی رشد چشمگیری نداشت، اما با افزایش این نسبت، بلورینگی افزایش یافت. تصاویر FESEM نشان داد با افزایش نسبت Si/Al ذرات مکعبی شکل چابازیت به صورت کامل ایجاد شده، اما در نسبتهای بالای Si/Al صافی سطح ذرات کاتالیستی کاهش یافت. آنالیز EDX حضور عناصر سازنده این زئولیت را تایید کرد و پراکندگی یکنواخت اجزا را نشان داد. نتایج بدست آمده از آنالیزBET نشان دادند که با افزایش نسبت Si/Al از 1/0 به 3/0 سطح ویژه در کاتالیستهای نانوساختار LaAPSO-34 افزایش یافته است. پیک های ناشی از آنالیز FTIR گروههای عاملی ساختار چابازیت را در نسبتهای گوناگون Si/Al تایید نمود. نتایج ارزیابی عملکرد کاتالیستها نشان دادند که با افزایش دمای واکنش مقدار تبدیل متانول افزایش یافته است. با افزایش نسبت Si/Al از 1/0 به 3/0 کارایی کاتالیستهای نانوساختار LaAPSO-34 بهبود یافت و مدت زمان بیشتری طول کشید تا کاتالیست غیرفعال شود.
The Si/Al ratio is one of the effective parameters on the physicochemical properties of nanostructured LaAPSO-34 catalysts. Utilization of optimum ratio of Si/Al could significantly enhance the efficiency of these molecular sieves in the methanol to olefins conversion. To this aim, a series of nanostructured LaAPSO-34 catalysts with different Si/Al ratios were synthesized via hydrothermal method and characterized by XRD, FESEM, EDX, BET and FTIR techniques. XRD results showed that the growth of crystalline network is not considerable in the low Si/Al ratio, while the crystallinity has increased by increasing of this ratio. FESEM images revealed that by increasing Si/Al ratio, cube-shaped chabazite particles completely were formed. However, rough on the surface of the catalyst particles was observed in the high ratio of Si/Al. EDX analysis confirmed the presence of elements of this zeolite and also showed a uniform distribution of components. BET results showed that by increasing of Si/Al ratio from 0.1 to 0.3, specific surface area of the nanostructured LaAPSO-34 catalysts increased. FTIR spectrums confirmed framework vibrations of chabazite in different Si/Al ratios. Catalytic performance tests showed that by increasing of reaction temperature, methanol conversion increased. Increasing the Si/Al ratio from 0.1 to 0.3 led to the enhancement of the LaAPSO-34 performance and catalyst stability.
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