パイロクロア構造を有する新化合物の水熱合成及びそのNO_x浄化特性

概要

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Several new compounds with a pyrochlore-type crystal structure have been synthesized by a low-temperature hydrothermal process under N_2 atmosphere using a mixture of nitrate salts. The chemical compositions of the new pyrochlores are represented as (a) Y_2Sn_1.8Cr_0.2O_7, (b) Y_1.8Sm_0.2Sn_1.8Cr_0.2O_7, (c) Y_1.8Ce_0.2Sn_1.8Cr_0.2O_7, (d) Y_1.8Eu_0.2Sn_1.8Cr_0.2O_7, (e) Y_2Zr_1.8Co_0.2O_7, (f) Ba_0.8Y_1.2Sn_1.8Cr_0.2O_7, (g) Ba_0.6Y_1.2Sm_0.2Sn_1.8Cr_0.2O_7 and (h) Ca_0.8Sm_1.2Sn_1.8Ni_0.2O_7. The Ba- and Ca-containing pyrochlores exhibited excellent spherical morphology with a pure pyrochlore phase structure and were composed of nanometer-sized particles. A- and B-site-doped pyrochlores maintained a fully ordered crystal structure over a wide temperature range. The pyrochlore oxide powders were tested as catalysts for NO_x absorption and reduction by CH_4. NO could be almost completely converted into N_2 using hydrothermally derived pyrochlore oxide catalysts in the absence of oxygen at high temperatures. Rapid absorption of NO into alkali-substituted pyrochlores was effective for NO removal from the gas phase, absorption being significantly accelerated by the presence of oxygen.
社団法人日本セラミックス協会の論文
2002-11-01