Nano鈥揗icrometer-Architectural Acidic Silica Prepared from Iron Oxide of Leptothrix ochracea Origin
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- 作者：Hideki Hashimoto ; Atsushi Itadani ; Takayuki Kudoh ; Satoshi Fukui ; Yasushige Kuroda ; Masaharu Seno ; Yoshihiro Kusano ; Yasunori Ikeda ; Yasuhiko Benino ; Tokuro Nanba ; Makoto Nakanishi ; Tatsuo Fujii ; Jun Takada
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2013
- 出版时间：June 12, 2013
- 年：2013
- 卷：5
- 期：11
- 页码：5194-5200
- 全文大小：393K
- 年卷期：v.5,no.11(June 12, 2013)
- ISSN：1944-8252
文摘
We prepared nano鈥搈icrometer-architectural acidic silica from a natural amorphous iron oxide with structural silicon which is a product of the iron-oxidizing bacterium Leptothrix ochracea. The starting material was heat-treated at 500 掳C in a H2 gas flow leading to segregation of 伪-Fe crystalline particles and then dissolved in 1 M hydrochloric acid to remove the 伪-Fe particles, giving a gray-colored precipitate. It was determined to be amorphous silica containing some amount of iron (Si/Fe = 60). The amorphous silica maintains the nano鈥搈icrostructure of the starting material鈥?img src="/appl/literatum/publisher/achs/journals/entities/223C.gif" alt="" class="entityA" align="bottom" />1-渭m-diameter micrometer-tubules consisting of inner globular and outer fibrillar structures several tens of nanometer in size鈥攁nd has many large pores which are most probably formed as a result of segregation of the 伪-Fe particles on the micrometer-tubule wall. The smallest particle size of the amorphous silica is 10 nm, and it has a large surface area of 550 m2/g with micropores (0.7 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, we found that it has relatively strong Br酶nsted and Lewis acidic centers that do not desorb pyridine, even upon evacuation at 400 掳C. The acidity of this new silica material was confirmed through representative two catalytic reactions: ring-opening reaction and Friedel鈥揅rafts-type reaction, both of which are known to require acid catalysts.