Solid acid MoO_(3)/ZrO_(2)-TiO_(2)catalysts were prepared by impregnation method,and catalytic hydrolysis of difluorodichloromethane(CFC-12)over the catalyst was studied.The presence of MoO_(3)/ZrO_(2)-TiO_(2)catalyst...Solid acid MoO_(3)/ZrO_(2)-TiO_(2)catalysts were prepared by impregnation method,and catalytic hydrolysis of difluorodichloromethane(CFC-12)over the catalyst was studied.The presence of MoO_(3)/ZrO_(2)-TiO_(2)catalyst in polycrystalline state could be clearly observed by transmission electron microscopy(TEM).Mesopores were detected by N2 adsorption-desorption isotherms which further confirmed the MoO_(3)/ZrO_(2)-TiO_(2)structural characteristics of catalyst.The results of NH_(3)-TPD showed that the calcination temperatures had a great influence on the acidity of the catalyst,and the weak acidic site had a strong catalytic activity for the catalytic hydrolysis of CFC-12.Moreover,ZrO_(2)-TiO_(2)was highly dispersed in the MoO_(3)framework,suggested by powder X-ray diffraction(XRD)and N_(2)adsorption-desorption results.The effects of the catalyst calcination temperatures on the conversion rate of CFC-12 were studied.The effects of catalytic hydrolysis temperatures and water vapor concentration on the catalytic hydrolysis rate of CFC-12 were also studied.The solid acid MoO_(3)/ZrO_(2)-TiO_(2)was calcined at 500℃for 3 h at a catalytic hydrolysis temperature of 400℃and water vapor concentration of 83.18%,and catalytic hydrolysis rate of CFC-12 reached 98.65%.The hydrolysis rate of CFC-12 remained above 65.34%after 30 hours continuous reaction.展开更多
Pt/ZrO_(2)catalysts promoted with MoO_(3)and Nb_(2)O_(5)were tested for the combustion of short-chain alkanes(namely,methane,ethane,propane,and n-hexane).For short-chain alkane combustion,the inhibition of MoO_(3)(for...Pt/ZrO_(2)catalysts promoted with MoO_(3)and Nb_(2)O_(5)were tested for the combustion of short-chain alkanes(namely,methane,ethane,propane,and n-hexane).For short-chain alkane combustion,the inhibition of MoO_(3)(for the methane reaction)dramatically transformed to promotion(for the ethane,propane,and n-hexane reactions)as the carbon chain length increased,whereas the remarkable promotion of Nb_(2)O_(5)gradually weakened with an increase in the carbon chain length.Based on a detailed study of the oxidation reactions of methane and propane over the catalysts,the different roles of the promoters in the reactions were ascribed to differences in the acidic properties of the surface and the oxidation or reduction states of the Pt species.The MoO_(3)promoter could decorate the surface of the Pt species for a Pt-Mo/ZrO_(2)catalyst,whereas the Nb_(2)O_(5)promoter on the support could be partially covered by Pt particles for a Pt-Nb/ZrO_(2)catalyst.The formation of accessible Pt-MoO_(3)interfacial sites,a high concentration of metallic Pt species,and a high surface acidity in Pt-Mo/ZrO_(2)were responsible for the enhanced activity for catalytic propane combustion.The lack of enough accessible Pt-Nb_(2)O_(5)interfacial sites but an enhanced surface acid sites in Pt-Nb/ZrO_(2)explained the slight improvement in activity for catalytic propane combustion.However,the stabilized Pt^(n+)species in Pt-Nb/ZrO_(2)were responsible for the much-improved activity for methane combustion,whereas the Pt^(n+)species in Pt-Mo/ZrO_(2)could be reduced during the oxidation reaction,and the fewer exposed surface Pt species because of MoO_(3)decoration accounted for the inhibited activity for methane combustion.In addition,it can be concluded that MoO_(3)promotion is favorable for the activation of C-C bonds,whereas Nb_(2)O_(5)promotion is more beneficial for the activation of C-H bonds with high energy.展开更多
基金Funded by the National Natural Science Foundation of China(No.51568068)the Young and Middle-aged Academic and Technical Leaders Reserve Talent Program(No.202105AC160054)。
文摘Solid acid MoO_(3)/ZrO_(2)-TiO_(2)catalysts were prepared by impregnation method,and catalytic hydrolysis of difluorodichloromethane(CFC-12)over the catalyst was studied.The presence of MoO_(3)/ZrO_(2)-TiO_(2)catalyst in polycrystalline state could be clearly observed by transmission electron microscopy(TEM).Mesopores were detected by N2 adsorption-desorption isotherms which further confirmed the MoO_(3)/ZrO_(2)-TiO_(2)structural characteristics of catalyst.The results of NH_(3)-TPD showed that the calcination temperatures had a great influence on the acidity of the catalyst,and the weak acidic site had a strong catalytic activity for the catalytic hydrolysis of CFC-12.Moreover,ZrO_(2)-TiO_(2)was highly dispersed in the MoO_(3)framework,suggested by powder X-ray diffraction(XRD)and N_(2)adsorption-desorption results.The effects of the catalyst calcination temperatures on the conversion rate of CFC-12 were studied.The effects of catalytic hydrolysis temperatures and water vapor concentration on the catalytic hydrolysis rate of CFC-12 were also studied.The solid acid MoO_(3)/ZrO_(2)-TiO_(2)was calcined at 500℃for 3 h at a catalytic hydrolysis temperature of 400℃and water vapor concentration of 83.18%,and catalytic hydrolysis rate of CFC-12 reached 98.65%.The hydrolysis rate of CFC-12 remained above 65.34%after 30 hours continuous reaction.
文摘Pt/ZrO_(2)catalysts promoted with MoO_(3)and Nb_(2)O_(5)were tested for the combustion of short-chain alkanes(namely,methane,ethane,propane,and n-hexane).For short-chain alkane combustion,the inhibition of MoO_(3)(for the methane reaction)dramatically transformed to promotion(for the ethane,propane,and n-hexane reactions)as the carbon chain length increased,whereas the remarkable promotion of Nb_(2)O_(5)gradually weakened with an increase in the carbon chain length.Based on a detailed study of the oxidation reactions of methane and propane over the catalysts,the different roles of the promoters in the reactions were ascribed to differences in the acidic properties of the surface and the oxidation or reduction states of the Pt species.The MoO_(3)promoter could decorate the surface of the Pt species for a Pt-Mo/ZrO_(2)catalyst,whereas the Nb_(2)O_(5)promoter on the support could be partially covered by Pt particles for a Pt-Nb/ZrO_(2)catalyst.The formation of accessible Pt-MoO_(3)interfacial sites,a high concentration of metallic Pt species,and a high surface acidity in Pt-Mo/ZrO_(2)were responsible for the enhanced activity for catalytic propane combustion.The lack of enough accessible Pt-Nb_(2)O_(5)interfacial sites but an enhanced surface acid sites in Pt-Nb/ZrO_(2)explained the slight improvement in activity for catalytic propane combustion.However,the stabilized Pt^(n+)species in Pt-Nb/ZrO_(2)were responsible for the much-improved activity for methane combustion,whereas the Pt^(n+)species in Pt-Mo/ZrO_(2)could be reduced during the oxidation reaction,and the fewer exposed surface Pt species because of MoO_(3)decoration accounted for the inhibited activity for methane combustion.In addition,it can be concluded that MoO_(3)promotion is favorable for the activation of C-C bonds,whereas Nb_(2)O_(5)promotion is more beneficial for the activation of C-H bonds with high energy.
