按凝胶中硅铝比分别为40和80,合成了板状和球形两种形貌的ZSM-5分子筛。通过将^(27)Al MAS NMR、Co(Ⅱ)离子交换能力及UV-Vis-DRS技术相结合表征了孤立铝和铝对的含量及骨架铝原子的落位信息;采用^(29)Si MAS NMR技术表征了骨架中Si(nSi...按凝胶中硅铝比分别为40和80,合成了板状和球形两种形貌的ZSM-5分子筛。通过将^(27)Al MAS NMR、Co(Ⅱ)离子交换能力及UV-Vis-DRS技术相结合表征了孤立铝和铝对的含量及骨架铝原子的落位信息;采用^(29)Si MAS NMR技术表征了骨架中Si(nSi,(4-n)Al)(n=0~4)序列群体;采用XPS结合XRF表征了ZSM-5分子筛体相、表面和内部的铝分布,并对上述表征骨架铝分布的方法进行了对比。结合多种表征技术,确定了合成的ZSM-5分子筛的铝分布和落位,确定了ZSM-5分子筛骨架中Al的化学环境,为构建ZSM-5分子筛的铝分布和落位与反应性能的关系提供了数据支持。展开更多
Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM...Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^(-2),equaling to a weight percentage around 4.5%.It has been revealed that the quantities of surface active oxygen(O_(2)^(-))and acid sites are crucial for the reaction,which can adsorb and activate NO_(x)and NH_(3)reactants effectively.Below the monolayer dispersion threshold,Co_(3)O_(4)is finely dispersed as sub-monolayers or monolayers and in an amorphous state,which is favorable to generate the two kinds of active sites,hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide.However,the formation of crystalline Co_(3)O_(4)above the capacity is harmful to the reaction performance.4%Co_(3)O_(4)/ZSM-5,the catalyst close to the monolayer dispersion capacity,possesses the most abundant active O_(2)^(-)species and acidic sites,thereby demonstrating the best reaction performance in all the samples.It is proposed the optimal Co_(3)O_(4)/ZSM-5 catalyst can be prepared by loading the capacity amount of Co_(3)O_(4)onto HZSM-5 support.展开更多
The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the...The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.展开更多
文摘按凝胶中硅铝比分别为40和80,合成了板状和球形两种形貌的ZSM-5分子筛。通过将^(27)Al MAS NMR、Co(Ⅱ)离子交换能力及UV-Vis-DRS技术相结合表征了孤立铝和铝对的含量及骨架铝原子的落位信息;采用^(29)Si MAS NMR技术表征了骨架中Si(nSi,(4-n)Al)(n=0~4)序列群体;采用XPS结合XRF表征了ZSM-5分子筛体相、表面和内部的铝分布,并对上述表征骨架铝分布的方法进行了对比。结合多种表征技术,确定了合成的ZSM-5分子筛的铝分布和落位,确定了ZSM-5分子筛骨架中Al的化学环境,为构建ZSM-5分子筛的铝分布和落位与反应性能的关系提供了数据支持。
基金the financial supporting by the National Natural Science Foundation of China(Grant Nos.21962009,22172071,22102069,22062013)the Natural Science Foundation of Jiangxi Province(Grant Nos.20202BAB203006,20181ACB20005)the Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis(Grant No.20181BCD40004).
文摘Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^(-2),equaling to a weight percentage around 4.5%.It has been revealed that the quantities of surface active oxygen(O_(2)^(-))and acid sites are crucial for the reaction,which can adsorb and activate NO_(x)and NH_(3)reactants effectively.Below the monolayer dispersion threshold,Co_(3)O_(4)is finely dispersed as sub-monolayers or monolayers and in an amorphous state,which is favorable to generate the two kinds of active sites,hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide.However,the formation of crystalline Co_(3)O_(4)above the capacity is harmful to the reaction performance.4%Co_(3)O_(4)/ZSM-5,the catalyst close to the monolayer dispersion capacity,possesses the most abundant active O_(2)^(-)species and acidic sites,thereby demonstrating the best reaction performance in all the samples.It is proposed the optimal Co_(3)O_(4)/ZSM-5 catalyst can be prepared by loading the capacity amount of Co_(3)O_(4)onto HZSM-5 support.
基金supported by the National Natural Science Foundation of China(21872160,U1832208)the National Science Fund for Distinguished Young Scholars(21825204)+2 种基金the National Key R&D Program of China(2017YFA0700101 and 2018YFB1501602)the Youth Innovation Promotion Association CAS(2017204)Natural Science Foundation of Shanxi Province(201901D211591)。
文摘The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.
