Nano-micrometer-architectural acidic silica prepared from iron oxide of leptothrix ochracea origin

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

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

We prepared nano-micrometer-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 C in a H2 gas flow leading to segregation of α-Fe crystalline particles and then dissolved in 1 M hydrochloric acid to remove the α-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-microstructure of the starting material - ∼1-μm-diameter micrometer-tubules consisting of inner globular and outer fibrillar structures several tens of nanometer in size - and has many large pores which are most probably formed as a result of segregation of the α-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 Brønsted and Lewis acidic centers that do not desorb pyridine, even upon evacuation at 400 C. The acidity of this new silica material was confirmed through representative two catalytic reactions: ring-opening reaction and Friedel-Crafts-type reaction, both of which are known to require acid catalysts.

Original languageEnglish
Pages (from-to)5194-5200
Number of pages7
JournalACS Applied Materials and Interfaces
Volume5
Issue number11
DOIs
Publication statusPublished - Jun 12 2013

Fingerprint

Leptothrix
Iron oxides
Silicon Dioxide
Silica
Pyridine
Iron
Hydrochloric Acid
Silicon
Hydrochloric acid
Particle Size
Acidity
Flow of gases
ferric oxide
Precipitates
Catalytic Domain
Bacteria
Hot Temperature
Gases
Particle size
Vapors

Keywords

  • acid catalysts
  • amorphous silica
  • biogenous iron oxides
  • Brønsted acid
  • iron-oxidizing bacteria
  • Lewis acid

ASJC Scopus subject areas

  • Materials Science(all)
  • Medicine(all)

Cite this

Nano-micrometer-architectural acidic silica prepared from iron oxide of leptothrix ochracea origin. / Hashimoto, Hideki; Itadani, Atsushi; Kudoh, Takayuki; Fukui, Satoshi; Kuroda, Yasushige; Seno, Masaharu; Kusano, Yoshihiro; Ikeda, Yasunori; Benino, Yasuhiko; Nanba, Tokuro; Nakanishi, Makoto; Fujii, Tatsuo; Takada, Jun.

In: ACS Applied Materials and Interfaces, Vol. 5, No. 11, 12.06.2013, p. 5194-5200.

Research output: Contribution to journalArticle

Hashimoto, Hideki ; Itadani, Atsushi ; Kudoh, Takayuki ; Fukui, Satoshi ; Kuroda, Yasushige ; Seno, Masaharu ; Kusano, Yoshihiro ; Ikeda, Yasunori ; Benino, Yasuhiko ; Nanba, Tokuro ; Nakanishi, Makoto ; Fujii, Tatsuo ; Takada, Jun. / Nano-micrometer-architectural acidic silica prepared from iron oxide of leptothrix ochracea origin. In: ACS Applied Materials and Interfaces. 2013 ; Vol. 5, No. 11. pp. 5194-5200.
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AU - Kuroda, Yasushige

AU - Seno, Masaharu

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AB - We prepared nano-micrometer-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 C in a H2 gas flow leading to segregation of α-Fe crystalline particles and then dissolved in 1 M hydrochloric acid to remove the α-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-microstructure of the starting material - ∼1-μm-diameter micrometer-tubules consisting of inner globular and outer fibrillar structures several tens of nanometer in size - and has many large pores which are most probably formed as a result of segregation of the α-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 Brønsted and Lewis acidic centers that do not desorb pyridine, even upon evacuation at 400 C. The acidity of this new silica material was confirmed through representative two catalytic reactions: ring-opening reaction and Friedel-Crafts-type reaction, both of which are known to require acid catalysts.

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