Fe-based catalysts have been discovered as the best elementary metal-based heterogeneous catalysts for the ammonia synthesis in industrial application during the last century.Herein,a novel and scalable strategy is de...Fe-based catalysts have been discovered as the best elementary metal-based heterogeneous catalysts for the ammonia synthesis in industrial application during the last century.Herein,a novel and scalable strategy is developed to prepare the K-promoted Fe/C catalyst with extremely high Fe loading (> 50 wt.%) through pyrolysis of the Fe-based metal-organic framework (MOF) xerogel.The obtained K-Fe/C catalysts exhibited superior activity and stability towards ammonia synthesis.The weight-specific reaction rate of Fe/C with K2O as promoter can achieve 12.4 mmol·g-1·h-1 at 350 ℃ and 30.4 mmol·g-1·h-1 at 400 ℃,approximately four and two times higher than that of the commercial fused-iron catalyst (3.4 mmol·g-1·h-1 at 350 ℃ and 16.7 mmol·g-1·h-1 at 400 ℃) under the same condition,respectively.The excellent performance of K-Fe/C can be ascribed to the inherited structure derived from the metal-organic frame precursors and the promotion of potassium,which can modify the binding energy of reactant molecules on the Fe surface,transfer electrons to iron for effective activation of nitrogen,prevent agglomeration of Fe nanoparticle (NPs) and restrain side reaction of carbon matrix to methane.展开更多
Spherical YAG：Ce^3＋ phosphor particles with narrow size distribution were prepared by spray pyrolysis. The effects of the concentration of solution, the flow rate of cartier gas and the annexing temperature on the p...Spherical YAG：Ce^3＋ phosphor particles with narrow size distribution were prepared by spray pyrolysis. The effects of the concentration of solution, the flow rate of cartier gas and the annexing temperature on the phosphor morphology were studied. The productivity of precursor particles shows a trend of drop after rising with the increase of concentration Raising the flow rate of nitrogen can improve the productivity of the precursor particles. Phosphor prepared by spray pyrolysis has obviously higher emission intensity than that synthesized by solid state reaction, spray pyrolysis makes Ce^3＋ ions well distributed in the crystal lattice as the luminescent centers, and phosphor particles have regular sphericity and narrow size distribution.展开更多
The organic matter in tropospheric aerosol plays an important role in atmospheric physical and chemical processes. The bulk of organic matter, representing a significant proportion of the total suspended particulate ...The organic matter in tropospheric aerosol plays an important role in atmospheric physical and chemical processes. The bulk of organic matter, representing a significant proportion of the total suspended particulate （TSP） mass, is bound to polymeric material whose structure and properties are largely unknown. Here we used thermodesorption gas chromatography/mass spectrometry （Td-GC/MS） to study organic compounds of low molecular mass and pyrolysis gas chromatography/mass spectrometry （Py-GC/MS） to characterize the chemical structure of macromolecules in TSP samples collected in different seasons from different sites in Guangzhou. n-Alkanes, fatty acids and nitriles were the predominant compounds in the thermodesorption products, whereas aromatics, fatty acids, nitriles and n-alkanes/alkenes were the major compounds in the pyrolysates. The results indicated that aromatics were main units in macromolecules. The fatty acids and nltriles formed from carboxylic ammonium salts were detected in both thermodesorption products and pyrolysates at a certain concentration, indicating the importance of these compounds in TSP formation. The TSP source mainly determined the occurrence of compounds in samples from urban, suburban and forest sites, whereas the TSP source and formation process maybe controlled the seasonal variation in compounds detected. High levels of nitriles in summer samples from suburban and forest sites coincide with the release of ammonium from the land and of fatty acids from vegetation at these sites.展开更多
The fibrous nickel oxide particles were prepared by chemical precipitation and pyrolysis method. The NiO precursors were firstly precipitated from nickel ions solution with addition of oxalate salt, and then the final...The fibrous nickel oxide particles were prepared by chemical precipitation and pyrolysis method. The NiO precursors were firstly precipitated from nickel ions solution with addition of oxalate salt, and then the final NiO particles were obtained by pyrolysis of the precursor. The effects of the pH value, precipitation temperature, reactant concentration, addition of surfactant on the morphology of the precursor particles were investigated. The crystallinity, purity, morphology of the fibrous NiO were analyzed by XRD and SEM. The fibrous NiO particles with 100120 in axis/diameter ratio may be produced under the optimal process conditions that are proposed: the Ni2+ concentration is （0.5）0.8 mol/L, pH value is 8.38.9, precipitation temperature is 6075 ℃, pyrolysis temperature is 500600 ℃.展开更多
基金This work was financially supported by the National Key Research and Development Program of China(Nos.2017YFB0602200 and 2017YFA0206701)National Program for Support of Top-notch Young Professionals,Changjiang Scholar Program and the National Natural Science Foundation of China(Nos.21725301,91645115,21673273,21473003,21872104,and 21821004)The XPS experiments were conducted at Lab of Multitechniques Electron&Ion Spectrometer for Surface Analysis of Peking University.We thank Jinglin Xie for XPS data discussion.
文摘Fe-based catalysts have been discovered as the best elementary metal-based heterogeneous catalysts for the ammonia synthesis in industrial application during the last century.Herein,a novel and scalable strategy is developed to prepare the K-promoted Fe/C catalyst with extremely high Fe loading (> 50 wt.%) through pyrolysis of the Fe-based metal-organic framework (MOF) xerogel.The obtained K-Fe/C catalysts exhibited superior activity and stability towards ammonia synthesis.The weight-specific reaction rate of Fe/C with K2O as promoter can achieve 12.4 mmol·g-1·h-1 at 350 ℃ and 30.4 mmol·g-1·h-1 at 400 ℃,approximately four and two times higher than that of the commercial fused-iron catalyst (3.4 mmol·g-1·h-1 at 350 ℃ and 16.7 mmol·g-1·h-1 at 400 ℃) under the same condition,respectively.The excellent performance of K-Fe/C can be ascribed to the inherited structure derived from the metal-organic frame precursors and the promotion of potassium,which can modify the binding energy of reactant molecules on the Fe surface,transfer electrons to iron for effective activation of nitrogen,prevent agglomeration of Fe nanoparticle (NPs) and restrain side reaction of carbon matrix to methane.
基金Project supported by National "The Tenth Five-Year"plan (2003BA316A01-03-05) and "The Tenth Five-Year"Plan(BE2004021) of Jiangsu provicce
文摘Spherical YAG：Ce^3＋ phosphor particles with narrow size distribution were prepared by spray pyrolysis. The effects of the concentration of solution, the flow rate of cartier gas and the annexing temperature on the phosphor morphology were studied. The productivity of precursor particles shows a trend of drop after rising with the increase of concentration Raising the flow rate of nitrogen can improve the productivity of the precursor particles. Phosphor prepared by spray pyrolysis has obviously higher emission intensity than that synthesized by solid state reaction, spray pyrolysis makes Ce^3＋ ions well distributed in the crystal lattice as the luminescent centers, and phosphor particles have regular sphericity and narrow size distribution.
基金supported by the National Natural Science Foundation of China (No. 40505026)the Chinese Academy of Sciences (No. KZCX2-YW-403)
文摘The organic matter in tropospheric aerosol plays an important role in atmospheric physical and chemical processes. The bulk of organic matter, representing a significant proportion of the total suspended particulate （TSP） mass, is bound to polymeric material whose structure and properties are largely unknown. Here we used thermodesorption gas chromatography/mass spectrometry （Td-GC/MS） to study organic compounds of low molecular mass and pyrolysis gas chromatography/mass spectrometry （Py-GC/MS） to characterize the chemical structure of macromolecules in TSP samples collected in different seasons from different sites in Guangzhou. n-Alkanes, fatty acids and nitriles were the predominant compounds in the thermodesorption products, whereas aromatics, fatty acids, nitriles and n-alkanes/alkenes were the major compounds in the pyrolysates. The results indicated that aromatics were main units in macromolecules. The fatty acids and nltriles formed from carboxylic ammonium salts were detected in both thermodesorption products and pyrolysates at a certain concentration, indicating the importance of these compounds in TSP formation. The TSP source mainly determined the occurrence of compounds in samples from urban, suburban and forest sites, whereas the TSP source and formation process maybe controlled the seasonal variation in compounds detected. High levels of nitriles in summer samples from suburban and forest sites coincide with the release of ammonium from the land and of fatty acids from vegetation at these sites.
文摘The fibrous nickel oxide particles were prepared by chemical precipitation and pyrolysis method. The NiO precursors were firstly precipitated from nickel ions solution with addition of oxalate salt, and then the final NiO particles were obtained by pyrolysis of the precursor. The effects of the pH value, precipitation temperature, reactant concentration, addition of surfactant on the morphology of the precursor particles were investigated. The crystallinity, purity, morphology of the fibrous NiO were analyzed by XRD and SEM. The fibrous NiO particles with 100120 in axis/diameter ratio may be produced under the optimal process conditions that are proposed: the Ni2+ concentration is （0.5）0.8 mol/L, pH value is 8.38.9, precipitation temperature is 6075 ℃, pyrolysis temperature is 500600 ℃.
