石墨负载Pt催化剂的制备、表征及活性研究

Pt/graphite catalyst was prepared by incipient wetness impregnation using H₂PtCl₆·6H₂O as precursor. The catalyst was characterized by SEM, XRD, XPS and its degradation ability for oxalic acid was evaluated. The preparation parameters, including the reduction temperature, Pt loading and pyrolysis were studied. The optimal preparation conditions were 350 ℃ with Pt loading of 1.0%. Results show that the loading of Pt can significantly enhance catalytic activity of graphite and that Pt/graphite catalytic ozonation can effectively remove oxalic acid in aqueous solution. The BET surface area of graphite is much smaller than that of activated carbon, however, the catalytic activity of Pt/graphite towards oxalic acid degradation is higher than that of Pt/AC. The XPS results indicate that the active phase at catalyst surface is in the form of Pt⁰. Compared with that of reduction process in hydrogen, the activity of Pt/graphite catalyst decreases when it is prepared by pyrolysis in air due to the lower Pt dispersion on graphite surface.     

Cu-Ni/La2O3热解C2H2制备碳纳米管的研究

Nano-sized and well-dispersed Cu-Ni/La₂O₃ can be obtained by reduction of LaCu_0.2Ni_0.8O₃ with the structure of perovskite. Using Cu-Ni/La₂O₃ as catalyst and C₂H₂ as carbon source, carbon nanotubes with a high yield and narrow diameter distribution can be obtained in the reaction temperature range of 650～700℃. Outer diameter of carbon nanotubes rangs from 9nm to 14nm. TG, Raman and XPS analysis indicate that carbon nanotubes prepared by Cu-Ni/La₂O₃ are relatively higher in graphitic degree.     

明胶基多孔碳球电极材料的制备及电化学性能研究

Gelatin-based porous carbon beads have been fabricated from gelatin micro-spheres by means of solidification, carbonization and chemical activation with KOH. The physical properties of gelatin-based porous carbon beads were studied by a t-plot method based on N₂ adsorption isotherms. The gelatin-based porous carbon beads activated at 800 ℃ exhibited the largest specific surface area and resulted in the highest capacitance. Carbon/carbon super-capacitors cells assembled with the electrode materials in 1.0 mol·L^-1 NEt₄BF₄ / acetonitrile electrolyte have also been studied. The electrochemical properties of gelatin-based porous carbon beads electrode were studied by using constant-current discharge tests. The results indicate that the gelatin-based porous carbon beads electrode is with good cycling stability and specific capacitance of 119.8 F·g^-1.     

Fe/La2O3纳米催化剂制备碳纳米管

Nanocrystalline LaFeO₃ was synthesised by the citrate method with La(NO₃)₃·6H₂O,Fe(NO₃)₃·9H₂O and citric acid as the raw materials. Before and after reduction, its structure was characterized by means of X-ray diffraction and transmission electron microscopy(TEM). And after reduction of LaFeO₃ oxide, the rare earth oxide, La₂O₃, prevents Fe particles from agglomerating and promotes the dispersion of nano-scale Fe particles (ca.40nm), which is one of the key factors for the growth of carbon nanotube. The carbon nanotubes from the catalytic de-composition of C₂H₂ were obtained using Fe/La₂O₃ nano-scale catalyst, which was formed from LaFeO₃ oxide as the catalyst precursor. The morphological structures of the carbon nanotube obtained have been examined by TEM. The results indicate that they are multi-walled nanotubes of good quality with inter diameter ranging from 20～25nm and length ranging from 25～40μm. The yields of carbon nanotube are 1.25g·gcat^-1 at the reaction temperature of 973K for 30min.     

载气气氛对Co/MgMoO4催化剂CVD法高效合成碳纳米材料的影响

High yield and quality mutli-walled carbon nanotube (MWNT) bundles and carbon nanofibers were synthesized by catalytic decomposition of methane over Co/MgMoO₄ catalyst at 1 000 ℃. TEM studies showed that the products were mainly carbon nanofibers without carrier gas and were all MWNT bundles with hydrogen or nitrogen as carrier gas. Thermal gravimetric analyses (TGA) on the raw product indicated that the purity of MWNT was higher than 95wt%. The growth mechanism of carbon nanofibers and MWNTs was also discussed.     

溶剂化金属原子浸渍法制备Pd-Cu/γ-Al2O3低温CO氧化催化剂

Nano-particle Pd/γ-Al₂O₃ monometallic and Pd-Cu/γ-Al₂O₃ bimetallic catalysts were prepared by solvated metal atom impregnation (SMAI) method. The results of XRD measurement indicated that Pd- Cu alloy was formed in the bimetallic catalysts and the crystalline particle size of the alloy increased as Cu contents increased with av-erage diameters < 6.0nm for all the samples. XPS and Auger spectra showed that Pd was in zero- valent state, Cu existed mainly in zero- valent state and partially in monovalent state Cu⁺. The Pd/γ-Al₂O₃ and Pd-Cu/γ-Al₂O₃ catalysts exhibited higher activity for CO oxidation at low temperature. The activity of Pd-Cu/γ-Al₂O₃ bimetallic catalyst was higher than that of Pd/γ-Al₂O₃ monometallic catalyst. The Pd-Cu/γ-Al₂O₃ catalyst with Pd/Cu atomic ratio of 1∶1 showed the highest activity.     

Sm修饰的Ni-MgO催化剂制备碳纳米管的研究

Carbon nanotubes (CNTs) have been synthesized over Ni-MgO and Ni-Sm-MgO catalysts by decomposition of CH₄ at 650 ℃. The addition of Sm into Ni-MgO catalyst not only promotes the catalytic activity and lifetime of the catalyst, but also improves the graphitization and heat stability of carbon nanotubes. The yield of CNTs obtained over the Ni-10Sm-MgO catalyst reaches 33 g C·(g Ni)^-1, being more than 5 times higher than that of the Ni-MgO catalyst. XRD and TPR results of the catalysts indicate that there is a remarkable interaction of Ni with Sm species, which facilitates the reduction of nickel and restrains the Ni particles from agglomerating.     

水热改性对NiMo/γ-Al2O3加氢脱氮催化剂结构及性能的影响

The influence of hydrothermal modification on the structure and hydrodenitrogenation (HDN) activity of NiMo/γ-Al₂O₃catalyst was studied in the range 140～180 ℃. The experimental results indicated that the hydrodenitrogenation reaction rate of pyridine was accelerated using the NiMo/γ-Al₂O₃catalyst synthesized via hydrothermal route due to the change of the structure, the increase of the amount of Mo and Ni and the rise of the specific surface area. The change of the structure of catalysts was enhanced at higher hydrothermal temperature, producing NiMo/γ-Al₂O₃catalyst with better HDN activity.     

Cr/CeO2体系及其对乙烷脱氢反应催化性能的研究

The dehydrogenation reaction of ethane over Cr/CeO₂ catalysts in presence of CO₂ was studied with fixed-bed micro-reactor. The Cr/CeO₂ catalysts of different Cr loading have been synthesized using impregnation techniques. The Cr/CeO₂ system has already been found to be active and selective in the reaction at around 740 ℃. The function of carbon dioxide is to remove coke and hydrogen to accelerate dehydrogenation of ethane. The results of catalysts characterizations indicated that Cr³⁺ and Cr⁶⁺ occurred on the surface of the catalysts. The 1.2 mmol Cr/100m₂ CeO₂ catalyst sample with a monolayer dispersion of Cr on CeO₂ support showed a stronger surface acidity and a maximum yield of ethylene of about 35.5% at 36.6% conversion of ethane.     

La2O2S∶Mn2+荧光粉的微波合成及其荧光特性

Using La₂(SO₄)3 and the active carbon powder as reactants, La₂O₂S∶Mn²⁺ red phosphor was synthesized by microwave radiation method. The phosphor was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), laser-diffraction size analyzer and fluorospectrophotometer. The XRD analysis showed that the phosphor was pure phase La₂O₂S. The phosphor of La₂O₂S∶Mn²⁺ showed hexagonal crystal structure with diverse shapes, such as spherical and rod, with average particle size of 10.22 μm. The emission and excitation spectra of the phosphor were determined by fluorospectrophotometer and the results showed that the excitation spectrum of the phosphor under 600 nm emission wavelength was excitation bands between 250 nm and 350 nm with a peak value of 303 nm. Then ,when exicited under UV 303 nm, the phosphor showed broad band emission of 550~700 nm with a peak at 607 nm. In addition, the optimal effects were obtained for the phosphor preparation when the concentration of the activator Mn²⁺ was x_Mn=0.01, the ratio of C and O (n_C / n_O) in the reactants was 0.6∶1, and the time of reaction was about 1 h. La₂O₂S∶Mn²⁺ has strong absorption of UV spectrum and can emit bright red light.