剥离型纳米片作为一种新型的强固体酸催化剂。

Exfoliated nanosheets as a new strong solid acid catalyst.

作者信息

Takagaki Atsushi, Sugisawa Mariko, Lu Darling, Kondo Junko N, Hara Michikazu, Domen Kazunari, Hayashi Shigenobu

机构信息

Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.

出版信息

J Am Chem Soc. 2003 May 7;125(18):5479-85. doi: 10.1021/ja034085q.

DOI:10.1021/ja034085q

PMID:12720462

Abstract

Two-dimensional metal oxide sheets in HTiNbO(5) and HSr(2)Nb(3)O(10), cation-exchangeable layered metal oxides, were examined as solid acid catalysts. Exfoliation of HTiNbO(5) and HSr(2)Nb(3)O(10) in aqueous solutions formed colloidal single-crystal TiNbO(5)(-) and Sr(2)Nb(3)O(10)(-) nanosheets, which precipitated under an acidic condition to form aggregates of HTiNbO(5) nanosheets and HSr(2)Nb(3)O(10) nanosheets. Although esterification of acetic acid, cracking of cumene, and dehydration of 2-propanol were not catalyzed by original HTiNbO(5) because of the narrow interlayer distance, which prevents the insertion of organic molecules, HTiNbO(5) nanosheets functioned as a strong solid acid catalyst for the reactions. Nanosheets of HSr(2)Nb(3)O(10) exhibited no or slight catalytic activity for these reactions. NH(3) temperature-programmed desorption and (1)H magic-angle spinning nuclear magnetic resonance spectroscopy revealed that HTiNbO(5) nanosheets have strong Brønsted acid sites, whereas HSr(2)Nb(3)O(10) nanosheets do not.

摘要

作为固体酸催化剂，我们研究了阳离子可交换层状金属氧化物HTiNbO₅和HSr₂Nb₃O₁₀中的二维金属氧化物片层。HTiNbO₅和HSr₂Nb₃O₁₀在水溶液中剥离形成了胶体单晶TiNbO₅⁻和Sr₂Nb₃O₁₀⁻纳米片，这些纳米片在酸性条件下沉淀，形成了HTiNbO₅纳米片和HSr₂Nb₃O₁₀纳米片的聚集体。尽管由于层间距离狭窄（阻止有机分子插入），原始的HTiNbO₅对乙酸酯化、异丙苯裂解和2-丙醇脱水没有催化作用，但HTiNbO₅纳米片对这些反应起到了强固体酸催化剂的作用。HSr₂Nb₃O₁₀纳米片对这些反应没有或仅有轻微的催化活性。NH₃程序升温脱附和¹H魔角旋转核磁共振光谱表明，HTiNbO₅纳米片具有强布朗斯特酸位点，而HSr₂Nb₃O₁₀纳米片则没有。