CoCr2O4在催化氢四氢萘的可控气氛下化学吸附氧的EPR研究

钴铬氧化物ＣｏＣｒ２Ｏ４对四氢萘催化氧化的比活性和得到萘满酮的选择性均高于单组分氧化物ＣｏＯ和 Ｃｒ２Ｏ３的。用ＥＰＲ方法对三个催化剂样品表面吸附氧及其在可控气氛下与四氢萘的作用进行了研究。     

SO2-4/CeO2-TiO2光催化材料的制备与光谱表征

采用溶胶-凝胶法结合硫酸浸渍法制备了SO2-4/CeO2-TiO2复合氧化物.利用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、吡啶吸附红外光谱(Py-FTIR)、紫外-可见光漫反射光谱(UV-Vis)、X射线光电子能谱价带谱(VB-XPS)及荧光光谱(PL)技术对样品的结构、性质进行了表征,以光催化分解水制氢为模型反应,评价了样品的光催化性能.XRD,FTIR结合PL结果表明CeO2与TiO2的复合形成了异质结构,有利于提高光生电子与光生空穴的分离效率,对催化剂活性的提高有促进作用;Py-FTIR谱图证明SO2-4/CeO2-TiO2复合氧化物在表面具有Lewis酸性,Lewis酸性位的产生是由于SO2-4在样品表面的配位吸附所致,S O— 的诱导效应增强了表面金属得电子能力,从而进一步提升光生载流子的分离效率;UV-Vis及XPS价带谱分析说明,半导体氧化物复合能够缩减带隙,拓宽光响应范围,Lewis酸性影响复合氧化物的能带结构,使其导带底位置向负向移动,利于光催化还原能力的提高,进而促进其光催化制氢活性.光催化分解水制氢实验结果表明,SO2-4/CeO2-TiO2复合氧化物具有优于纯氧化物CeO2,TiO2及未经硫酸浸渍的CeO2-TiO2复合氧化物的催化活性,5 h的产氢速率为1934.1μmol·g-1·h-1.光谱分析结果结合光催化制氢活性评价结果表明,SO2-4/CeO2-TiO2复合氧化物的异质结构与酸浸渍是影响样品光催化性能的主要因素.     

沉淀过程pH值对铈锆复合氧化物结构与性能的影响

采用加热回流老化技术制备了系列组成为0.6CeO₂-0.4ZrO₂的铈锆复合氧化物,通过N₂物理吸附、Raman光谱、UV-Vis 漫反射光谱等方法对沉淀过程pH值对铈锆复合氧化物结构及储氧性能的影响进行了研究。结果表明,沉淀过程pH值不同,将导致铈锆复合氧化物的组成产生波动,进而影响样品的晶相组成、缺陷性质、结晶程度和孔结构性质。控制沉淀pH值为10.5～11.0,可消除Si的影响,改善铈锆复合氧化物的孔结构,提高相均匀性,提高缺陷浓度,降低结晶度,从而可提高样品的储氧性能。     

不同形貌锰氧化物对重金属离子吸附的AAS和AFS分析

通过简单的水热法控制性合成了两种不同形貌的锰氧化物(层状OL和隧道状OMS),并考察了这两种材料对几种重金属离子Pb2+,Cu2+,Ni2+,Hg2+的吸附。通过原子吸收光谱(AAS)和原子荧光光谱(AFS)测定吸附前后离子浓度,比较两种材料的吸附性能,以及对不同离子的选择性吸附。实验表明OMS形貌的锰氧化物是一种良好吸附剂,对铅离子具有很好的选择性吸附,两分钟内吸附率达98%。由此可建立一种简单、绿色、高效地去除污水中重金属离子的方法。     

低温容器内活性炭吸氢性能的模拟研究

以石墨片微元构建活性炭的结构模型,采用巨正则蒙特卡罗(GCMC)方法从微观研究H2在以活性炭为基的复合吸氢剂中的吸附特性,获得了不同条件下复合吸氢剂对H2的吸附过程.结果表明,氧化物吸氢剂修饰对活性炭材料的表面化学性能影响较大,引入之后使其吸氢量增加了一倍以上;氧化物吸氢剂嫁接在活性炭上的不同位置吸氢效果不同,以双键连...     

SO_4~(2-)/CeO_2-TiO_2光催化材料的制备与光谱表征（英文）

采用溶胶-凝胶法结合硫酸浸渍法制备了SO_4~(2-)/CeO_2-TiO_2复合氧化物。利用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、吡啶吸附红外光谱(Py-FTIR)、紫外-可见光漫反射光谱(UV-Vis)、X射线光电子能谱价带谱(VB-XPS)及荧光光谱(PL)技术对样品的结构、性质进行了表征,以光催化分解水制氢为模型反应,评价了样品的光催化性能。XRD,FTIR结合PL结果表明CeO_2与TiO_2的复合形成了异质结构,有利于提高光生电子与光生空穴的分离效率,对催化剂活性的提高有促进作用;Py-FTIR谱图证明SO_4~(2-)/CeO_2-TiO_2复合氧化物在表面具有Lewis酸性,Lewis酸性位的产生是由于S_4O~(2-)在样品表面的配位吸附所致,S=O的诱导效应增强了表面金属得电子能力,从而进一步提升光生载流子的分离效率;UV-Vis及XPS价带谱分析说明,半导体氧化物复合能够缩减带隙,拓宽光响应范围,Lewis酸性影响复合氧化物的能带结构,使其导带底位置向负向移动,利于光催化还原能力的提高,进而促进其光催化制氢活性。光催化分解水制氢实验结果表明,SO_4~(2-)/CeO_2-TiO_2复合氧化物具有优于纯氧化物CeO2,TiO2及未经硫酸浸渍的CeO_2-TiO_2复合氧化物的催化活性,5h的产氢速率为1 934.1μmol·g~(-1)·h~(-1)。光谱分析结果结合光催化制氢活性评价结果表明,SO_4~(2-)/CeO_2-TiO_2复合氧化物的异质结构与酸浸渍是影响样品光催化性能的主要因素。     

Low-temperature Catalytic Reduction of Nitrogen Monoxide with Carbon Monoxide on Copper Iron and Copper Cobalt Composite Oxides

通过共沉淀法, 在低温下制备了铜铁复合氧化物CuO/Fe2O3和铜钴复合氧化物CuO/Co3O4．利用GC微反应器评价了这些复合氧化物的催化活性和热稳定性,结果表明, CuO/Fe2O3和CuO/Co3O4的NO100%转化温度分别为80和90 ℃,该催化活性和热稳定性在较宽的温度和较长的时间范围内都能得以保持．此外,还系统研究了试剂的摩尔比率、NaOH的体积、陈化时间、煅烧温度和煅烧时间对该复合氧化物催化活性的影响．     

控制脉冲还原法研究氧化物催化剂中晶格氧化的活动性

通过微分反应器中的丙烯脉冲还原反应，研究了铁铋钼，铁锑碲及铁锑三种复合氧化物催化剂中晶格氧的活动性，测定了铁铋钼，铁锑碲两种氧化物催化剂体相晶格氧化扩散活化能，半定量地研究了氧化物表面区晶格氧的活动性，对晶格氧的活动性与氧化选择性的关系进行了讨论。     

电场作用下S修饰C24N24从CO2/N2混合气体中选择性吸附

在燃烧后气体中选择性捕获CO2,对减缓因CO2浓度过高引发的环境问题具有十分重要的意义。本文采用第一性原理计算的方法,研究了外加电场作用下S修饰C24N24富勒烯对CO2的选择性吸附性能。首先研究了S@C24N24的结构和性质,发现其具有良好的稳定性。其次,研究了无电场时S修饰C24N24富勒烯对CO2的吸附行为,发现其吸附为弱的物理吸附。另外,进一步研究了外加电场作用下S@C24N24对CO2的吸附行为。结果表明,结合距离（CO2与S）和CO2的键角（O=C=O）随电场的增大而减小;当电场增加到0.018 au时,物理吸附转变为化学吸附。关闭电场时,化学吸附又转化为物理吸附。此外,即使在相同的电场条件下,S修饰C24N24富勒烯对N2的吸附也为弱的物理吸附。这表明,通过控制外加电场的开/关,S@C24N24可以从CO2/N2混合气体中选择性捕获/释放CO2,可作为选择性捕获CO2的优良候选材料。     

激光促进异丁烷选择氧化制甲基丙烯酸

用共沉淀法制备了Fe和Mo的复合氧化物。运用XRD,IR,TPD和LSSR技术研究了其晶体结构,表面构造,化学吸附特性和激光促进异丁烷选择氧化反应性能,结果表明,Fe-Mo-O的主体物相为Fe2(MoO4)3,并有少量的MoO3相;其表面上存在Lewis碱位（Mo=O和Mo0O-Fe键中的O）及Lewis酸位Fe^3+,异丁烷的两个甲基H分别吸附在两个相邻的Lewis碱位（Mo=O)上形成双位分子吸附态;在常压和200度条件下,用一定频率的激光激发Mo=O键1000次,异丁烷的转化率为5．8％,其反应产物是异丁烯,甲基丙烯醛和甲基丙烯酸,其中甲基丙烯酸的选择性为80％,根据实验结果,探讨了激光促进异丁烷选择氧化为甲基丙烯酸的表面反应机理。     

Iron Species Present in Fe/ZSM-5 Catalysts – Influence of the Preparation Method

The Fe species present in Fe/ZSM-5 catalysts prepared by ionic exchange in aqueous solution or in the solid state are investigated. The samples were characterized by XRD, EPR, Mössbauer Spectroscopy (MOS-S) and chemical analysis. XRD showed that the peak intensity decreased with the increase in Fe content in the samples. EPR and MOS-S showed that the Fe atoms in all the activated samples appear as Fe⁺³, independently of the method used in the catalyst preparation. The MOS-S data also showed that Fe/ZSM-5, prepared by ion exchange in the solid state presented lower hematite content and more Fe species in charge-compensation sites, the responsible for the catalytic activity, as confirmed by the behavior in the propane oxidation.     

Selective CO oxidation in hydrogen-rich gas over CuO/CeO2 catalysts

A series of CuO/CeO₂ catalysts with different Cu-Ce compositions were synthesized by co-precipitation method and characterized by X-ray diffraction, H₂-TPR, CO-TPD, SEM and X-ray photoelectron spectroscopy (XPS) techniques. The effects of Cu-Ce composition and water vapor on the catalytic properties for the selective CO oxidation in the hydrogen-rich gas were investigated. The results indicated that CuO (10%)/CeO₂ catalyst remained the maximum CO conversion and selectivity at 140 and 160 °C, while the performance of CuO/CeO₂ catalysts deteriorated with the CuO molar ratio further increased. The interfacial CuO and CeO₂ interaction and synergistic effect enhanced the redox properties of CuO/CeO₂ catalyst and the highly dispersed copper species were proposed as the active sites for the selective CO oxidation. The blockage of catalytic active sites by absorbed water and the formation of CO-H₂O surface complexes reduced the activity of CuO (10%)/CeO₂ catalyst. The decreasing of surface lattice oxygen and absorbed oxygen species and the agglomeration of copper particles were the plausible interpretations for the deactivation of CuO (10%)/CeO₂ catalyst.     

葡萄糖催化氧化反应用Pd-Co/C催化剂的XPS研究

活性炭为载体，制备了Pd/C、Pd-Co/C催化剂，并进行了活性评价和XPS表征。在Pd-Co／C催化剂上反应3h后，葡萄糖的转化率达92％，选择性为94％，较Pd/C催化剂有显著提高。Co的添加及焙烧过程改变了Pd/C催化剂的表面组成及结构，提高了贵金属Pd在催化剂表面的分散程度，有利于Pd的还原，使Pd-Co/C催化剂表现出良好的催化活性和选择性。     

DRIFTS study of Cu1Zr1Ce9Odelta catalysts for selective CO oxidation

The Cu1Zr1Ce9Odelta catalysts synthesized with coprecipitation method were used into the selective CO oxidation in hydrogen-rich gas. The adsorbed species and the intermediates on Cu1Zr1Ce9Odelta catalysts were examined by in-situ diffuse reflectance FTIR spectroscopy (in-situ DRIFTS) technique. It was found that hydrogen, oxygen and CO in the feed stream were adsorbed competitively at the same adsorption sites on the surface of Cu1Zr1Ce9Odelta catalysts. The pretreatment with hydrogen caused the deep reduction of Cu+ species to Cu0 species and decreased the capacity of CO adsorption on the catalyst surface. The Cu1Zr1Ce9Odelta catalyst pretreated with oxygen offered more active oxygen species and inhibited the deep reduction of Cu+ species. The helium pretreatment only purified the surface of Cu1Zr1Ce9Odelta catalyst. Two IR bands at 2938.7 and 2843.8 cm(-1) due to bridged formate and bidentate formate species appeared at 180 degrees C. The active oxygen anion of Cu1Zr1Ce9Odelta catalyst could react with CO and produce carbonate species at room temperatures. The carbonate and formate species occupied the adsorption sites and deteriorated the catalytic performance of Cu1Zr1Ce9Odelta. Flushing the Cu1ZnrCe9Odelta catalyst with helium at 300 degrees C, the bidentate formate species on the catalyst surface decomposed to monodentate carbonate species and then further decomposed to CO2, which could release the adsorption sites and restore well the catalytic activity.     

Surface and catalytic properties of doped tin oxide nanoparticles

Mixed oxides composed of Zn-Sn, Ti-Sn and V-Sn were prepared by a co-precipitation method and evaluated as catalysts for methanol oxidation in an ambient fixed-bed reactor. Surface analysis by X-ray photoelectron spectroscopy (XPS) revealed an electronic interaction between dopant and Sn atoms in the oxide structure and showed the formation of surface states associated with the dopants. Oxygen vacancies were present on the Zn-doped oxide, and the oxidation of methanol to carbon oxides was favored. The Ti-doped oxide exhibited a favorable selectivity to dimethyl ether, related to the oxygen anions near Ti centers. Vanadium dopants not only dramatically increased the catalytic activity but also promoted the partial oxidation of methanol to formaldehyde. Results demonstrate that the bridging dopant-O-Sn bond acts as active sites and influences product distribution.     

Surface characterization and reactivity of vanadium-tin oxide nanoparticles

Surface state and reactivity of vanadium-tin mixed oxide nanoparticles (V/Sn ratios 0.05-0.2) were characterized by spectroscopic techniques and catalytic measurements. Analyses by X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS) revealed that the oxidation state and surface structure of vanadium oxide species and the electronic interaction between Sn and V atoms are dependent upon the vanadium content. These oxides were evaluated as catalysts for methanol oxidation in a fixed-bed reactor. Both reaction rate and formaldehyde selectivity increased with increasing the vanadium amount in catalyst. Results demonstrate that the V⁵⁺ site in the bridging V-O-Sn structure exhibits a high redox activity to facilitate the transformation of adsorbed methoxy to formaldehyde and that the vanadium dispersion plays a crucial role in the surface reactivity. A mechanism that elucidates the catalytic redox process is proposed.     

Impact of active phase chemical composition and dispersity on catalytic behavior in PROX reaction

Iron and iron-platinum catalysts supported on activated carbon have been successfully synthesized by wet impregnation method and low-temperature treatment in inert atmosphere. The content of the supported phases corresponds to 10 wt % Fe and 0.5 wt % Pt. Four catalytic samples were synthesized: Sample A—activated carbon impregnated with Fe nitrate; Sample B—activated carbon impregnated with Pt salt; Sample C—activated carbon impregnated consequently with Fe and Pt salts; Sample D—activated carbon impregnated simultaneously with Fe and Pt salts. The as-prepared materials were characterized by Mössbauer spectroscopy, X-ray diffraction, infrared and X-ray photoelectron spectroscopy. The spectra show that the activated carbon support and the preparation procedure give rise to the synthesis of isolated metal Pt ions and ultradispersed Fe and Pt oxide species. Probably the presence of different functional groups of activated carbon gives rise to registered very high dispersion of loaded species on support. The catalytic tests were carried out in PROX reaction. A lower activity of bimetallic Pt-Fe samples was explained with the increase in surface oxygen species as a result of predomination of iron oxide on the support leading to the increase in selectivity to the H₂ oxidation. Partial agglomeration of supported iron oxide phase was registered after catalytic tests.     

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The catalytic activity of the substoichiometric tungsten trioxide electrodes for the oxidation of hydrogen has been investigated, using simultaneous EPR spectroscopy and linear-sweep voltammetry measurements. The parameters of the EPR spectral line observed for all oxides except stoichiometric WO₃ were determined in relation to the electronic structure of the paramagnetic centers associated with the oxygen anion vacancies. Hydrogen adsorption was followed by means of changes both in the EPR line parameters and in the electrode potential. The intensity-versus-potential curves for suboxide electrodes under hydrogen were analyzed in terms of the occurrence of two processes. It was shown that one process is associated with the hydrogen oxidation and that the other is connected with oxidation of the WO_3?x surface. The mechanisms of both reactions were interpreted as involving the formation and oxidation of an hydrogen tungsten bronze.     

Promoting effect of tin oxides on alumina-supported gold catalysts used in CO oxidation

In this study the influence of SnO_x nanoparticles on the catalytic performance of alumina-supported gold catalysts was investigated in CO oxidation. The tin modified supports were prepared by grafting of tetraethyltin onto the surface of alumina via its hydroxyl groups. The decomposition of organometallic surface species in oxygen yielded highly dispersed tin oxide on the surface of alumina. Gold was introduced onto the tin modified alumina support by both deposition-precipitation with urea and direct anionic exchange techniques using HAuCl₄ solution. Based on catalytic and different spectroscopic measurements it is suggested that the presence of “Snⁿ⁺-Au ensemble sites” is responsible for the increased activity of these catalysts.     

Sensitivity of styrene oxidation reaction to the catalyst structure of silver nanoparticles

This study shows how different morphologies of silver nanoparticles affect the selective oxidation of styrene in the gas phase using oxygen as oxidant. Silver nanoparticles (nanowires and nanopolyhedra), prepared using the polyol process, were supported on α-Al₂O₃. For comparison, a conventional catalyst obtained by wet impregnation was also prepared. Phenylacetaldehyde (Phe) and styrene oxide (SO) were the main products for nanoparticles catalysts. The promotion effect on the catalytic activity of potassium and cesium on the silver nanowires catalysts was also studied. At 573 K, the styrene conversion and selectivity to styrene oxide with the silver nanowires catalyst were 57.6 and 42.5%, respectively. Silver nanopolyhedra catalyst showed 57.5% conversion and 30.8% selectivity to styrene oxide. The promotion by cesium played an important role in improving the epoxidation of styrene. The samples were structurally characterized using X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) were applied to characterize the oxygen species detected (O_β, O_γ) on the silver surface.