Abstract: A series of SnxZr1-xO2 solid solution catalysts with SnO2 content varied from 10％(w) to 90％(w) were prepared by co-current coprecipitation method (CCP method) using ammonia solution as precipitating agent and calcined at 500 ℃ for 4 h in air.The structure variation with SnO2 content was investigated by XRD,electron diffraction,FT-Raman and FT-IR.Tin dioxide and zirconia can react with each other to form solid solutions within a large composition range.In the present work,zirconia prepared by CCP method and calcined at 500 ℃ was monoclinic,and tin dioxide prepared by the same way possessed rutile structure.The experiment results showed the following dependence of the solid solution structure on SnO2 content.First,less than 20％ SnO2 inserted into the lattice of ZrO2 could stabilize the tetragonal structure of zirconia and form the zirconia-rich solid solutions.Then,amorphous zirconia-rich solid solutions were formed in the SnO2 content region from 30 ％ to 50％.Furthermore,a rutile structure tin dioxide-rich solid solution existed as SnO2 content over 60％.Finally,the zirconia-rich solid solution and tin dioxide-rich solid solution could co-exist while the SnO2 content maintained at 55％,which exhibited a structure transition between zirconia-rich and tin dioxide-rich solid solutions.Because the Sn－O bond was weakened and the effective electropositivity of Sn4＋ was decreased as Zr4＋ inserted into SnO2 lattice as proved by FT-Raman and FT-IR measurements,both the activation and the complete combustion of propene were restrained by Zr4＋,as a result,the catalytic performance for NO selective reduction was promoted.

Key words: NO, Selective catalytic reduction, Sn_xZr_1-xO₂ solid solution, Rutile structure