用Na_2HPO_4与NaVO_3和Na_2WO_4·12H_2O合成Keggin型催化剂H_(3+x)PW_(12-x)V_xO_(40),并将H_(3+x)PW_(12-x)V_xO_(40)、1-丁基-3-甲基咪唑溴离子液体混合,制备[Bmim]_(3+x)PW_(12)-xV_xO_(40),以SiO_2为载体,制备负载型的杂多酸...用Na_2HPO_4与NaVO_3和Na_2WO_4·12H_2O合成Keggin型催化剂H_(3+x)PW_(12-x)V_xO_(40),并将H_(3+x)PW_(12-x)V_xO_(40)、1-丁基-3-甲基咪唑溴离子液体混合,制备[Bmim]_(3+x)PW_(12)-xV_xO_(40),以SiO_2为载体,制备负载型的杂多酸杂化分子材料催化剂[Bmim]_(3+x)PW_(12-x)V_xO_(40)/SiO_2,以H_2O_2为氧化剂,考察[Bmim]_5PW_(10)V_2O_(40)/SiO_2对染料甲基橙的降解脱色性能。结果表明,催化剂在用量为0.10 g(50%)、H_2O_2为5 m L、温度为60℃、p H为3对甲基橙(碱氮颜料)具有很好的降解效果,可达95.1%。并催化剂有很好的回收效果,可以多次重复使用。展开更多
Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO_(x)removal reactions through the inter-particle diffusion of intermediate species,their s...Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO_(x)removal reactions through the inter-particle diffusion of intermediate species,their subsequent reaction mechanism on acid sites is still unclear and requires investigation.In this study,the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions,which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species.Systematic in situ diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)reaction demonstrate that the Lewis acid sites over MnO_(x)are more active for NO reduction but have lower selectivity to N_(2)than Brønsted acids sites.Brønsted acid sites primarily produce N_(2),whereas Lewis acid sites primarily produce N_(2)O,contributing to unfavorable N_(2)selectivity.The Brønsted acid sites present in Y zeolite,which are stronger than those on MnO_(x),accelerate the NH_(3)-SCR reaction in which the nitrite/nitrate species diffused from the MnO_(x)particles rapidly convert into the N_(2).Therefore,it is important to design the catalyst so that the activated NO species formed in MnO_(x)diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnO_(x)particle.For the physically mixed H-MnO_(x)+H-Y sample,the abundant Brønsted/Lewis acid sites in H-MnO_(x)give rise to significant consumption of activated NO species before their inter-particle diffusion,thereby hindering the enhancement of the synergistic effects.Furthermore,we found that the intercalated K+in K-MnO_(x)has an unexpected favorable role in the NO reduction rate,probably owing to faster diffusion of the activated NO species on K-MnO_(x)than H-MnO_(x).This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.展开更多
文摘用Na_2HPO_4与NaVO_3和Na_2WO_4·12H_2O合成Keggin型催化剂H_(3+x)PW_(12-x)V_xO_(40),并将H_(3+x)PW_(12-x)V_xO_(40)、1-丁基-3-甲基咪唑溴离子液体混合,制备[Bmim]_(3+x)PW_(12)-xV_xO_(40),以SiO_2为载体,制备负载型的杂多酸杂化分子材料催化剂[Bmim]_(3+x)PW_(12-x)V_xO_(40)/SiO_2,以H_2O_2为氧化剂,考察[Bmim]_5PW_(10)V_2O_(40)/SiO_2对染料甲基橙的降解脱色性能。结果表明,催化剂在用量为0.10 g(50%)、H_2O_2为5 m L、温度为60℃、p H为3对甲基橙(碱氮颜料)具有很好的降解效果,可达95.1%。并催化剂有很好的回收效果,可以多次重复使用。
文摘Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO_(x)removal reactions through the inter-particle diffusion of intermediate species,their subsequent reaction mechanism on acid sites is still unclear and requires investigation.In this study,the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions,which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species.Systematic in situ diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)reaction demonstrate that the Lewis acid sites over MnO_(x)are more active for NO reduction but have lower selectivity to N_(2)than Brønsted acids sites.Brønsted acid sites primarily produce N_(2),whereas Lewis acid sites primarily produce N_(2)O,contributing to unfavorable N_(2)selectivity.The Brønsted acid sites present in Y zeolite,which are stronger than those on MnO_(x),accelerate the NH_(3)-SCR reaction in which the nitrite/nitrate species diffused from the MnO_(x)particles rapidly convert into the N_(2).Therefore,it is important to design the catalyst so that the activated NO species formed in MnO_(x)diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnO_(x)particle.For the physically mixed H-MnO_(x)+H-Y sample,the abundant Brønsted/Lewis acid sites in H-MnO_(x)give rise to significant consumption of activated NO species before their inter-particle diffusion,thereby hindering the enhancement of the synergistic effects.Furthermore,we found that the intercalated K+in K-MnO_(x)has an unexpected favorable role in the NO reduction rate,probably owing to faster diffusion of the activated NO species on K-MnO_(x)than H-MnO_(x).This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.
