排序方式: 共有26条查询结果,搜索用时 15 毫秒
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T. Giornelli A. Lfberg L. Guillou S. Paul V. Le Courtois E. Bordes-Richard 《Catalysis Today》2007,128(3-4):201-207
Catalytic wall (structured) reactors and structured supports are suitable to study the catalytic properties of nanosized materials. The coating of metallic (aluminum and stainless steel) plates by thin layers of active phase is presented in two cases, VOx/TiO2 and Co/SiO2, catalysts used in the oxidative dehydrogenation (ODH) of propane and in Fischer–Tropsch synthesis (FTS) of clean fuels, respectively. The preparation of coated plates and their characterisation by various methods of physicochemical analysis are described. Both chemical and physical methods were used for coating. VOx/TiO2 layers were obtained by grafting of Ti (on Al or stainless-steel plates) and V (on TiO2) alkoxides and use of sol–gel media or suspension. A silica primer was deposited (on stainless-steel plate) by plasma-assisted chemical vapour deposition (PACVD) onto which Co oxide and silica were coprecipitated from sol–gel. The catalytic experiments in the respective reactions were carried out in special plate reactors and compared with those of catalytic powders. The study shows that the coating of a metallic substrate by a catalyst is not straightforward and requires specific studies dealing with both chemistry (chemical affinity between substrate and catalytic layers) and catalytic engineering (catalytic performance in taylor-made reactors). 相似文献
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室温下,采用脉冲直流反应磁控溅射技术在玻璃衬底上制备了氧化钒薄膜.研究了脉冲调制功率占空比对薄膜物相、表面形貌、组分和热敏电学性能的影响.X射线衍射测试结果表明在室温及不同占空比下生长的氧化钒薄膜均为非晶结构;原子力显微镜表面形貌测试表明降低占空比可以得到更加光滑的薄膜表面;X射线光电子能谱测试表明降低占空比能够在反应溅射气氛不变的情况下促进钒的氧化;对薄膜的热敏电学特性测试发现,在293~368 K,小极化子跳跃是脉冲反应磁控溅射氧化钒薄膜中主要的导电机制. 相似文献
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以高纯氧和高纯氩为气源,通过改变薄膜的制备工艺,用直流磁控溅射法在玻璃和单晶硅片上制备了VOx
薄膜,并对其进行了退火处理。借助LCR测试仪和X射线衍射仪,对VOx薄膜的电阻温度系数、晶体结构进行了检测。结果表明,当溅射
气压为1.5Pa,功率为100W,时间为1h,氧氩比为0.8∶25时,
经450℃退火后,玻璃基片上制备的薄膜的电阻温度系数(TCR)超过-0.02/℃,其结构和性能最好。同时对比了玻璃和单晶硅基片对VOx
薄膜的生长、性能和结构的影响。当氧氩比为0.8∶25时,单晶硅片上制得的VOx薄膜的质量和性能最好。 相似文献
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J. M. L pez Nieto P. Concepci n A. Dejoz F. Melo H. Kn zinger M. I. V zquez 《Catalysis Today》2000,61(1-4):361-367
The oxidative dehydrogenation (OXDH) of n-butane and 1-butene on undoped and K-doped alumina-supported vanadia catalysts has been studied. The low selectivity to OXDH products on alumina-supported vanadia catalysts is a consequence of the isomerization of olefins (low temperatures) and the formation of carbon oxides (high temperatures) on acid sites. The presence of potassium results in a decrease of the number of acid sites and a higher selectivity to OXDH products from both n-butane and 1-butene. Infrared spectroscopy data of 1-butene adsorbed on the catalysts suggest the presence of different adsorbed species: (i) O-containing species on the undoped catalyst, or (ii) adsorbed butadiene on K-doped catalyst. A reaction network including parallel and consecutive reactions is proposed. 相似文献
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通过共沉淀法将La组分掺入到TiO_2载体中,采用浸渍法将V和W组分负载到La_2O_3-TiO_2复合氧化物上,制备出V2O5-WO3/La_2O_3-TiO_2催化剂。考察不同La_2O_3掺杂量对其NH3催化还原NO性能的影响,同时通过多种物理化学手段进行表征分析。XRD,NH_3-in situ DRIFTS,H_2-TPR,XPS和UV-vis DRS测试结果表明,元素La与Ti以La-O-Ti键相互作用,生成高度分散的镧物种,也使得TiO_2具有更好的热稳定性,但由于LaO_x物种与VO_x物种和WO_x物种之间的相互作用,降低了催化剂的氧化还原性和表面Brnsted酸数量,从而降低了其催化活性。 相似文献
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采用射频磁控溅射法,在普通玻璃基片上成功制备了SiO2/VOx多层复合薄膜。采用X射线衍射仪(XRD)、傅立叶变换红外光谱仪(FTIR)、紫外可见光分光光度计(UV-Vis)和X射线光电子能谱仪(XPS)研究了薄膜的物相、热致相变特性及V的价态。结果表明,薄膜中VO2晶体具有(110)择优取向生长;SiO2底膜有助于多层复合薄膜中VO2相结晶度的提高,可使V4+摩尔分数由53.9%提高至66.0%;同时,SiO2增透膜的增透效果明显,增透膜沉积时间为60 min时,可使SiO2/VOx/SiO2多层复合薄膜可见光透过率提高至51%;制得的SiO2/VOx/SiO2多层复合薄膜具有较好的热致相变特性。 相似文献
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《International Journal of Hydrogen Energy》2019,44(21):10156-10162
Developing effective and robust electrocatalysts that are applicable for intense conditions is promising for variable industrial oxygen evolution reaction (OER). Herein, we have developed a simple hydrothermal strategy to construct a three dimensional nanoflower-like VOx nanosheets (VOx/NiS/NF) that utilizes S-modified NF as substrate. NiS/NF can provide not only high-surface area for the growth of VOx but also better conductivity and stability derived from NiS. XRD shows the formation of amorphous VOx supported on NiS/NF. XPS confirms the existence and valence state of V, Ni and S. EDX and SEM elemental mapping reveal the composition and great distribution of V, O, Ni and S. SEM and TEM show that the thin VOx nanosheets covered on the surface of NiS/NF uniformly, which implying more exposed active sites. OER measurements display that VOx/NiS/NF has the outstanding catalytic activity with the lower overpotential (330 mV, 50 mA cm−2), smaller tafel slope (121 mV dec−1) and lower value of semicircle of EIS than VOx/NF. The modification of NF may be the key for enhancement performances for OER due to reduced charge transfer resistance. The strong durability of VOx/NiS/NF may be attributed to the tighter integration between VOx and NiS/NF in alkaline electrolytes. The impressive results may provide a new strategy to design suitable substrate with good dispersion and conductivity to prepare effective electrocatalysts for OER. 相似文献