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|Title: ||Mesoporous H-AlMCM-48: highly efficient solid acid catalyst|
|Authors: ||DAPURKAR, SE|
|Keywords: ||friedel-crafts alkylation|
|Issue Date: ||2003|
|Publisher: ||ELSEVIER SCIENCE BV|
|Citation: ||APPLIED CATALYSIS A-GENERAL, 254(2), 239-249|
|Abstract: ||Mesoporous cubic Na-AlMCM-48 molecular sieve catalyst with a Si/Al (molar) ratio of 60 was synthesized hydrothermally and characterized by various analytical and spectroscopic techniques. Al-27 MAS-NNIR results indicate that the presence of aluminum in tetrahedral framework (Bronsted acid site) in both as-synthesized and calcined samples. However, in the case of the latter, a small amount of aluminum was found to be in octahedral coordination. This observation is well supported by NH3-TPD studies over protonated catalyst (H-AlMCM-48), where desorption profile at higher temperature shows features characteristic of Lewis acid sites. Further, these studies also indicate that the presence of high concentration of moderate-to-strong Bronsted acid sites at lower temperature, which are more suitable for the para-selective tertiary-butylation reaction of phenol. Hence, in the present investigation, the reaction was carried out H-AIMCM-48, which however showed much higher activity as compared to the hexagonal H-AlMCM-41. In addition, it was also found that the former does not get deactivated owing to three-dimensional pore system while the latter is susceptible to deactivation on account of one-dimensional pore system. (C) 2003|
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