Synthesis of Sulfated Silica-Doped Tin Oxides and Their High Activities in Transesterification
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Synthesis of Sulfated Silica-Doped Tin Oxides and Their High Activities in Transesterification Yunchen Du Æ Sen Liu Æ Yanyan Ji Æ Yonglai Zhang Æ Shu Wei Æ Fujian Liu Æ Feng-Shou Xiao
Received: 21 September 2007 / Accepted: 11 February 2008 / Published online: 26 February 2008 Ó Springer Science+Business Media, LLC 2008
Abstract A series of sulfated silica-doped tin oxides with large surface areas (113–188 m2/g) have been successfully prepared from hydrothermal synthesis, followed by sulfation and calcination. These samples are characterized by XRD, FT-IR, TEM, nitrogen isotherms, and TG techniques, and obtained results indicate that the samples are composed of tetragonal nanocrystalline tin oxides and amorphous silica. Very interestingly, catalytic tests show that these sulfated silica-doped tin oxides are much more active than conventional sulfated tin oxides for transesterification of triacetin with methanol. Keywords Sulfated tin oxides Silica-doped Tetragonal crystalline Transesterification
1 Introduction Biodiesel is a renewable fuel that can be produced by transesterifications from vegetable oils and short-chain alcohols in the presence of homogeneous catalysts such as sulfuric acid and sodium hydroxide [1–5]. However, these homogeneous catalysts usually have the disadvantages in separation and environmental pollution. Therefore, there is a great interest on developing catalytically active solids in transesterification [6–22]. Among them, basic solid catalysts exhibit excellent catalytic activities [7–14], but the interaction between CO2 in air with these basic solid
Y. Du S. Liu Y. Ji Y. Zhang S. Wei F. Liu F.-S. Xiao (&) State Key Laboratory of Inorganic Synthesis and Preparative Chemistry and College of Chemistry, Jilin University, Changchun 130012, China e-mail: [email protected]
catalysts normally results in deactivation of these catalysts. In contrast, acidic solid catalysts which are also active for transesterification [16–23], are more chemically stable than basic solid catalysts. As typical acidic solids, sulfated zirconia and tungstated zirconia have been considered to be very effective catalysts for transesterification [20–23]. It is well known that sulfated tin oxides (SO24 /SnO2) is one of the candidates with strong acidity [24–26], giving higher catalytic activities in esterification and FriedelCrafts acylation than sulfated zirconia [27, 28], but there are few reports concerning on its performance in transesterification. Conventionally, sulfated tin oxides prepared by precipitation method shows relatively small surface area, and one solution for this problem is to fabricate mesostructured sulfated tin oxides with enhanced catalytic activities [29–31]. Unfortunately, some of them exhibit poor thermal stability [29, 30]. Herein, we demonstrated a facile route to prepare sulfated silica-doped tin oxides from hydrothermal synthesis, followed by sulfation and calcination. Very interestingly, these samples have much higher BET surface areas (113– 188 m2/g) and better activi
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