Characterization and Catalytic Activities of Al 2 O 3 -Promoted Sulfated Tin Oxides
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Characterization and Catalytic Activities of Al2O3-Promoted Sulfated Tin Oxides Jie Zhao Æ Yinghong Yue Æ Dewei Zhai Æ Changxi Miao Æ Jianyi Shen Æ Heyong He Æ Weiming Hua Æ Zi Gao
Received: 21 August 2009 / Accepted: 4 September 2009 / Published online: 16 September 2009 Springer Science+Business Media, LLC 2009
Abstract A series of Al2O3-doped (0.5–3 mol%) sulfated tin oxides have been prepared by a co-precipitation method, followed by sulfation and calcination. Textural and structural characterizations of these samples were performed by means of XRD, N2 adsorption, XPS, DTG, Raman spectroscopy, diffuse reflectance UV-vis spectroscopy and 27Al MAS NMR. FT-IR spectra of adsorbed pyridine were used to determine the acid properties. The addition of small amounts of Al2O3 (0.2–1.5 mol%) to sulfated tin oxide brings about a dramatic improvement of catalytic activity from 36.1 to 52.4–58.0% for acylation of 2-methoxynaphthalene with acetic anhydride. Keywords Acylation
Sulfated tin oxide Al2O3 promotion
1 Introduction Solid superacids of sulfated metal oxides, as environmentally friendly catalysts, have attracted enormous interests in
J. Zhao Y. Yue D. Zhai H. He W. Hua (&) Z. Gao Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, 200433 Shanghai, People’s Republic of China e-mail: [email protected] C. Miao (&) Shanghai Research Institute of Petrochemical Technology, 201208 Shanghai, People’s Republic of China e-mail: [email protected] J. Shen Lab of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, 210093 Nanjing, People’s Republic of China
the last 20 years because of their higher activities than traditional strong solid acids (e.g., zeolites) in a number of industrially important reactions such as alkane isomerization, alkylation, acylation, esterification and etc. [1–6]. Among sulfated metal oxides, sulfated zirconia (SO42-/ ZrO2) has been studied most extensively. Sulfated tin oxide (SO42-/SnO2) is one of the candidates with the strongest acidity on the surface, and its acid strength is reported to be equal to that of SO42-/ZrO2 at least [7–9]. Arata et al. reported that SO42-/SnO2 showed even higher catalytic activities for some reactions than SO42-/ZrO2 [10, 11]. However, in contrast to numerous studies on SO42-/ZrO2, papers concerning SO42-/SnO2 catalyst have been quite few because of difficulty in preparation. Tin oxide gels usually obtained were fine particles, and a large part of the precipitates were passed through a conventional filter paper, leading to their decreased yields. This difficulty could, however, be avoided by washing the gels with aqueous ammonium acetate solution. In our early study we found that incorporating small amounts of Al2O3 (0.5–3 mol%) into SO42-/ZrO2 enhanced substantially the catalytic activity and stability, if n-butane isomerization was performed at 250 C in the presence of H2 [12]. This remarkable promoting effect was most likely attributed to a dif
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