Preparation and Characterization of 纬-Al2O3 with Rich Br酶nsted Acid Sites and Its Application in the Fluid Catalytic Cracking Process

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• 作者：Rui Feng ; Songtao Liu ; Peng Bai ; Ke Qiao ; Youhe Wang ; Hamid A. Al-Megren ; Mark J. Rood ; Zifeng Yan
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 27, 2014
• 年：2014
• 卷：118
• 期：12
• 页码：6226-6234
• 全文大小：515K
• 年卷期：v.118,no.12(March 27, 2014)
• ISSN：1932-7455

文摘

The objective of this work is to investigate the surface acidity of 纬-Al₂O₃ after modification and its application in reducing coke formation in the fluid catalytic cracking (FCC) process. 纬-Al₂O₃ with rich Br枚nsted acid sites and reduced Lewis acid sites was prepared by the sol鈥揼el method using NH₄BF₄ as a modifier to develop a new functional material to adjust surface acidity. N₂ sorption, powder X-ray diffraction (XRD), ²⁷Al magic angle spinning nuclear magnetic resonance (²⁷Al MAS NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the structure and surface properties of the prepared 纬-Al₂O₃. The results showed that partial fluorination of the surface of 纬-Al₂O₃ generated small quantities of a pyrochlore-type phase which was formed mainly by substitution of the OH group on six-coordinated aluminum with fluorine. In addition, boron insertion in the structure of 纬-Al₂O₃ reduced the Lewis acid concentration and increased the surface area of 纬-Al₂O₃. After aging in an alkaline solution with a F/Al mole ratio of 0.45, the modified 纬-Al₂O₃ demonstrated high surface area (276 m²/g) with gamma alumina structure due to the synergistic effect of boron and fluorine doping by using NH₄BF₄. However, most importantly the modified 纬-Al₂O₃ exhibited the high Br枚nsted/Lewis acid ratio of 0.75. In the bench-scale tests with heavy oil, the modified 纬-Al₂O₃ showed good catalytic performance by increasing conversion of heavy oil to light oil while reducing coke formation.