纯相和镍取代的Co_3O_4尖晶石催化剂用于N_2O直接分解(英文)

A series of NixCo1-xCo2O4(0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N2O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500 °C for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co3O4. The N2O decomposition measurement revealed significant increase in the activity of Co3O4 spinel oxide catalyst with the partial replacement of Co2+ by Ni2+. The activity of this series of catalysts was controlled by the degree of Co2+ substitution by Ni2+, spinel crystallite size, catalyst surface area, presence of residual K+, and calcination temperature.     

Catalytic Hydrogenation of Nitrobenzene to Aniline by Ag/γ-Fe_2O_3

The Ag/γ-Fe_2O_3 nanocomposite was synthesized by solvothermal reduction method via using ferric nitrate and silver nitrate as raw materials, and ethylene glycol as the reducing agent. The composite was characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscope, and energy dispersive X-ray. The prepared Ag/γ-Fe_2O_3 was used for the catalytic hydrogenation of nitrobenzene to aniline by hydrazine hydrate. The factors such as the silver content in the catalyst, reaction time, reaction temperature and the regeneration of catalyst were investigated. The results showed that the yield of aniline reached 100% by utilizing the 1%wt(nitrobenzene) Ag/γ-Fe_2O_3 for the catalytic hydrogenation of nitrobenzene for 3 h to obtain aniline at 78 ℃, hydrazine hydrate as the hydrogen source, while the silver content in the catalyst was 3%mol.     

Detection of sulfamethazine by voltammetry based on γ -cd/g-c3n4 nanosheets modified electrodeEI北大核心CSCD

Bulk carbon nitride (b-C3N4) was prepared from melamine by thermal polymerization method. The graphitic carbon nitride (g-C3N4) was prepared by recombining ultrasonication method, and γ-CD/g-C3N4 composites were obtained by ultrasonication g-C3N4 with γ-cyclodextrin (γ-CD). The working electrode of the sensor for sulfamethazine (SM2) detection was decorated by γ-CD/g-C3N4 on glassy carbon electrode (GCE). Electrochemical analysis of SM2 was performed under optimized conditions, and the results showed that the determination of SM2 on this electrode was controlled by adsorption. The linear range of this method was 1-150 µmol/L and 150750 µmol/L with a detection limit of 0.79 µmol/L. Results showed that the determination was not interfered after adding 50 times K+, Ca2+, Fe3+, Cu2+, NH4+, SO42−, NO3−, chlortetracycline hydrochloride, vitamins, paraaminobenzoic acid and other interfering substances. In addition, the peak currents retained 93% and 87% of the original response after the electrode was stored for 5 d and 10 d at 5°C, respectively. This method was successfully applied to determine the levels of SM2 in milk samples with good recoveries ranging from 84% to 113% and the relative standard deviations (RSD) was lower than 5%. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Co-modified Pd/CeO2-ZrO2 catalysts for methanol decomposition

Pd/Ce0.8Zr0.2O2 catalysts modified by cobalt were prepared by a sequential impregnation method and characterized by X-ray powder diffraction(XRD), N2adsorption/desorption(Brunauer-Emmet-Teller), oxygen storage capacity(OSC), CO-chemisorption, H2-temperature-programmed reduction(H2-TPR) and X-ray photoelectron spectroscopy(XPS). The effect of Co on the performance of methanol decomposition was evaluated at a fixed-bed microreactor. The results showed that the addition of Co can improve the oxygen storage capacity of the catalyst and the dispersion of Pd. XPS results indicated that Pd was in a partly oxidized(Pdδ+, 1δ2) state and Co2+was present in Pd catalysts modified by Co. A 90% conversion of methanol was achieved at around 280°C over Pd-Co/Ce0.8Zr0.2O2 catalyst which was 20°C lower than that over Pd/Ce0.8Zr0.2O2, indicating that both Pdδ+and Co2+play an important role in improving the catalytic activity of methanol decomposition.     

Co-modified Pd/CeO_2-ZrO_2 catalysts for methanol decomposition

Pd/Ce0.8Zr0.2O2 catalysts modified by cobalt were prepared by a sequential impregnation method and characterized by X-ray powder diffraction(XRD), N2adsorption/desorption(Brunauer-Emmet-Teller), oxygen storage capacity(OSC), CO-chemisorption, H2-temperature-programmed reduction(H2-TPR) and X-ray photoelectron spectroscopy(XPS). The effect of Co on the performance of methanol decomposition was evaluated at a fixed-bed microreactor. The results showed that the addition of Co can improve the oxygen storage capacity of the catalyst and the dispersion of Pd. XPS results indicated that Pd was in a partly oxidized(Pdδ+, 1δ2) state and Co2+was present in Pd catalysts modified by Co. A 90% conversion of methanol was achieved at around 280°C over Pd-Co/Ce0.8Zr0.2O2 catalyst which was 20°C lower than that over Pd/Ce0.8Zr0.2O2, indicating that both Pdδ+and Co2+play an important role in improving the catalytic activity of methanol decomposition.     

Preparation and Characterization of Single-Phase Perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ

Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ has been successfully prepared by using citrate-EDTA complexation method at relatively low calcination temperature. The structure and thermal decomposition process of the complex precursor have been investigated by means of differential scanning calorimetry-thermal gravimetric analysis (DSC/TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopic (FT-IR) measurements. The precursor decomposed completely and started to form perovskite-type oxide above 420℃ according to the differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results. Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ obtained has been confirmed from the XRD pattern, and no peak of SrCO3 was found by XR.D of the oxides synthesized at a relatively low temperature of 800 ℃. The reducibility of La0.6Sr0.4Co0.8Fe0.2O3-δ was also characterized by the temperature programmed reduction (TPR) technique. Disk shaped dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was prepared by the isostatical pressing method. The oxygen flux rate of dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was (2.8-18)×10-8 mol/(cm2·s) in the temperature range of 800-1 000℃.     

Egyptian heavy vacuum gas oil hydrotreating over Co-Mo/CNT and Co-Mo/γ-Al_2O_3 catalysts

The catalytic activity of CoMoS /CNT towards the Egyptian heavy vacuum gas oil hydrotreating was studied. The delivered CNT was functionalized with 6 mol /L HNO_3. The CNT were loaded with 12% MoO_3( by weight) and 0.7 Co /Mo atomic ratio with impregnation methods. The γ-Al_2O_3 catalyst was also prepared by impregnation method to compare both catalysts activities.The analysis tools such XRD,Raman spectroscopy,TEM,and BET were used to characterize the catalysts. The autoclave reactor was used to operate the hydrotreating experiments. The hydrotreating reactions were tested at various operating conditions of temperature 325-375 ℃,pressure 2-6 MPa,time 2-6 h,and catalyst /oil ratio( by weight) of 1 ∶75,1 ∶33 and 1 ∶10. The results revealed that the CoMoS /CNT was highly efficient for the hydrotreating more than the CoMoS /γ-Al_2O_3. Also, the hydrodesulfurization( HDS) increased with increasing catalyst /oil ratio. Additionally,results showed that the optimum condition was temperature 350℃,pressure 4 MPa,catalyst /oil ratio of 1 ∶75 for 2 h. Furthermore,even at low CoMoS /CNT catalyst /oil ratio of 1 ∶75,an acceptable HDS of 77.1% was achieved.     

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

The Ru/Al_2O_3 catalysts modified with metal oxide(K_2O and La_2O_3)were prepared via incipient wetness impregnation method from RuCl_3·nH_2O mixed with nitrate loading on Al_2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX)from the hydrogen-rich gas streams produced by reforming gas,and the performances of catalysts were investigated by XRD and TPR.The results showed that the activity temperature of the modified catalysts Ru-K_2O/Al_2O3 and Ru-La_2O_3/Al_2O_3 were lowered approximately 30℃compared with pure Ru/Al_2O_3,and the activity temperature range was widened.The conversion of CO on Ru-K_2O/Al_2O_3 and Ru-La_2O_3/Al_2O_3 was above 99% at 140-160℃,suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La_2O_3/Al_2O_3 was higher than that of Ru-K_2O/Al_2O_3 in the active temperature range. Slight methanation reaction was detected at 220℃and above.     

Synthesis of High-purity Fe2AlB2 and the Effect as Sintering Additive for ZrB2

Fe₂AlB₂ powder material was prepared by the direct reaction of iron,aluminum and boron powders in a tubular furnace.The effects of different Al contents,temperature and raw material pretreatment on the purity of product were studied.The mixed powder with the stoichiometric ratio of 1.5Al/2Fe/2B was processed by CIP (Cold Isostatic Pressing),and then calcined at 1150℃ for 120 min.The product containing a small amount of impurities is treated with alkaline solution to obtain high-purity Fe₂Al B₂ powder.Zr B₂-Fe₂Al B₂ composite ceramic was successfully prepared at 1250℃ by hot pressing sintering.The density,hardness and fracture toughness were 96.2%,22±0.3 GPa and 5.78±0.5 MPa·m^1/2,respectively.     

Al2O3基Ni-Cu双金属催化剂上乙酰丙酸氢解（英）

Inexpensive γ-alumina-based nickel-copper bimetallic catalysts were studied for the hydrogenolysis of levulinic acid,a key platform molecule for biomass conversion to biofuels and other valued chemicals,into γ-valerolactone as a first step towards the production of 2-methyltetrahydrofurane.The activities of both monometallic and bimetallic catalysts were tested.Their textural and chemical characteristics were determined by nitrogen physisorption,elemental analysis,temperature-programmed ammonia desorption,and temperature-programmed reduction.The monometallic nickel catalyst showed high activity but the highest bγ-product production and significant amounts of carbon deposited on the catalyst surface.The copper monometallic catalyst showed the lowest activity but the lowest carbon deposition.The incorporation of the two metals generated a bimetallic catalyst that displayed a similar activity to that of the Ni monometallic catalyst and significantly low bγ-product and carbon contents,indicating the occurrence of important synergetic effects.The influence of the preparation method was also examined by studying impregnated- and sol-gel-derived bimetallic catalysts.A strong dependency on the preparation procedure and calcination temperature was observed.The highest activity per metal atom was achieved using the sol-gel-derived catalyst that was calcined at 450 ℃.High reaction rates were achieved;the total levulinic acid conversion was obtained in less than 2 h of reaction time,yielding up to 96%γ-valerolactone,at operating temperature and pressure of 250 ℃ and 6.5 MPa hydrogen,respectively.     

锂离子电池正极材料LiCo1/3Ni1/3Mn1/3O2

镍钴锰三元材料作为锂二次电池正极材料是目前国内外研究热点。综述了三元材料近几年国内外的研究状况，重点介绍了LiCo1/3Ni1/3Mn1/3O2材料的结构与电化学性能的内在联系，探讨了不同制备方法及不同元素的掺杂改性对材料的影响，讨论了LiCo1/3Ni1/3Mn1/3O2正极材料的应用前景。     

溶胶凝胶法制备钇掺杂锂离子电池正极材料LiCo1/3Ni1/3Mn1/3O2

采用溶胶凝胶方法制备了LiCo1/3Ni1/3Mn1/3O2正极材料，研究了不同掺杂量的Y对于LiCo1/3Ni1／3Mn1/3O2材料结构和性能的影响。研究发现，掺杂量〉1％后Y不能很好地融入材料的晶格之中。电化学性能测试结果表明，少量Y的掺杂（1％～3％）可以明显改善LiCo1／3Ni1／3Mn1/3O2材料的循环性能。     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺,在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3.采用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析.结果表明,Y2O3包覆并没有改变LiCO1/3Ni1/3Mn1/3O2的晶体结构,只存在于LiCo1/3Ni1/3Mn1/3O2的表面;与未包覆的材料相比,Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量.CV测试表明,包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

湿化学法合成LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2及其表征(英文)

利用琥珀酸为鳌合剂的湿化学法成功合成了一系列锂离子电池正极材料LiNi1/3Mn1/3Co1/3O2,在合成过程中改变琥珀酸与金属离子摩尔比(R)并研究了这一参数对合成LiNi1/3Mn1/3Co1/3O2材料物理及电化学性质的影响.采用热重、X射线衍射、Rietveld精修、扫描电镜以及超导量子干涉仪对反应机理、材料的结构、形貌以及磁学性质进行了详细表征.得到最佳合成条件为R=1,此时LiNi1/3Mn1/3Co1/3O2的阳离子混排度最低.此外,通过Rietveld精修得到该材料阳离子混排度的结果与通过磁学方法得到的结果定量相符,如对于在R=1条件下合成的样品,Rietveld精修结果显示其阳离子混排度为1.85%,而超导量子干涉仪的测试结果为1.80%.当充放电区间为3.0-4.3V,电流密度为0.2C(1C=160mA·g-1)时,该样品的首次放电容量为161mAh·g-1,库仑效率为93.1%,经过50次循环后,容量保持率可达91.3%.     

TiO2包覆对LiCO1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3MnO2的循环件能,采用浸渍-水解法对其进行TiO2包覆.用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流允放电测试研究包覆材料的结构和电化学性能.TiO2仅在材料表面形成包覆层,并未改变材料的结构.TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能,TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%,而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%.包覆后的材料在2.0C下循环12周后的容最没有衰减,而未包覆的材料容量保持率仅为94.4%.EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高.循环后材料的XRD和ICP-OES测试表明,包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

回火处理对LiNi1/3Co1/3Mn1/3O2结构和电化学性能的影响

以硝酸锂、四水合乙酸镍、四水合乙酸钴、四水合乙酸锰、氨水和草酸为原料,通过共沉淀-燃烧法合成了锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2,采用XRD、SEM和充放电试验对合成产物进行了表征,研究了回火处理对合成产物结构和电化学性能的影响.实验结果表明,嫩烧反应形成的LiNi1/3C1/3Mn31/3O2结...     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺, 在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3. 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析. 结果表明, Y2O3包覆并没有改变LiCo1/3Ni1/3Mn1/3O2的晶体结构, 只存在于LiCo1/3Ni1/3Mn1/3O2的表面; 与未包覆的材料相比, Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量. CV测试表明, 包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

ZnO包覆LiNi1/3Co1/3Mn1/3O2的表面结构和电化学性能

在LiNi_1/3Co_1/3Mn_1/3O₂正极材料表面包覆ZnO,通过X射线衍射（XRD）和光电子能谱（XPS）分析包覆层对正极材料表面状态的改变,并考察了改性后材料的放电容量、首次不可逆容量等电化学性能变化. 结果表明：ZnO主要存在于材料表面并影响着材料表面组成和电化学性质,材料表面镍和锰的含量随着包覆量的增加而增大;400 ^oC热处理可使过渡金属与锌在材料表面形成复合氧化物,过渡金属的结合能增大;包覆2%（by mass,下同）的ZnO可有效抑制55 ^oC下充放电时3.6 V附近的不可逆反应,提高了材料的首次库仑效率;包覆2% ZnO的电池材料在55 ^oC/0.5C的放电比容量和循环寿命最佳.     

TiO2包覆对LiCo1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3Mn1/3O2的循环性能, 采用浸渍-水解法对其进行TiO2包覆. 用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流充放电测试研究包覆材料的结构和电化学性能. TiO2仅在材料表面形成包覆层, 并未改变材料的结构. TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能, TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%, 而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%. 包覆后的材料在2.0C下循环12周后的容量没有衰减, 而未包覆的材料容量保持率仅为94.4%. EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高. 循环后材料的XRD和ICP-OES测试表明, 包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2的低温燃烧合成

以LiNO3、Ni(NO3)2·6H2O、Co(NO3)2·6H2O、Mn(NO3)2、CO(NH2)2为原料,通过低温燃烧法在空气中合成了锂离子正极材料LiNi1/3Mn1/3Co1/3O2.采用XRD研究了合成产物的物相与结构,用SEM研究了合成产物的形貌,考察了点火温度、回火温度,回火时间以及锂过量对合成产物电化学性能的影响.研究结果表明,合成产物与层状LiNiO2的结构相同,属α-NaFeO2型层状结构,合成产物的粒度较小且比较均匀,并具有良好的电化学性能.采用低温燃烧法在空气中合成LiNi1/3Mn1/3Co1/3O2的最佳条件为:500℃点火,850℃回火20h,锂过量为15mol%.在此条件下得到的合成产物首次放电比容量达到158.9mAh/g.