Preparation and characterization of γ-Al2O3 with rich Brønsted acid sites and its application in the fluid catalytic cracking process

Rui Feng, Songtao Liu, Peng Bai, Ke Qiao, Youhe Wang, Hamid A. Al-Megren, Mark J. Rood, Zifeng Yan

Research output: Contribution to journalArticlepeer-review

Abstract

The objective of this work is to investigate the surface acidity of γ-Al2O3 after modification and its application in reducing coke formation in the fluid catalytic cracking (FCC) process. γ-Al2O3 with rich Brönsted acid sites and reduced Lewis acid sites was prepared by the sol-gel method using NH 4BF4 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 γ-Al 2O3. The results showed that partial fluorination of the surface of γ-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 γ-Al2O3 reduced the Lewis acid concentration and increased the surface area of γ-Al2O 3. After aging in an alkaline solution with a F/Al mole ratio of 0.45, the modified γ-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 γ-Al2O3 exhibited the high Brönsted/Lewis acid ratio of 0.75. In the bench-scale tests with heavy oil, the modified γ-Al2O3 showed good catalytic performance by increasing conversion of heavy oil to light oil while reducing coke formation.

Original languageEnglish (US)
Pages (from-to)6226-6234
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number12
DOIs
StatePublished - Mar 27 2014

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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