H3PW12O40／CeO2光催化脱色甲基橙溶液的研究

以CeO2为载体,用浸渍法制备了不同负载量的磷钨酸催化剂,并且考察了催化剂光催化脱色甲基橙溶液的催化性能。结果表明:磷钨酸最佳负载量为9%(质量分数);光催化剂加入量为300mg/100mL;在较低浓度下,甲基橙溶液的光催化脱色反应符合一级动力学方程;H3PW12O40/CeO2与TiO2具有相同的催化性能;催化剂再生后活性可恢复至65%。     

Charge transfer and formation of reduced Ce3+ upon adsorption of metal atoms at the ceria (110) surface

The modification of cerium dioxide with nanoscale metal clusters is intensely researched for catalysis applications, with gold, silver, and copper having been particularly well studied. The interaction of the metal cluster with ceria is driven principally by a localised interaction between a small number of metal atoms (as small as one) and the surface and understanding the fundamentals of the interaction of metal atoms with ceria surfaces is therefore of great interest. Much attention has been focused on the interaction of metals with the (111) surface of ceria, since this is the most stable surface and can be grown as films, which are probed experimentally. However, nanostructures exposing other surfaces such as (110) show high activity for reactions including CO oxidation and require further study; these nanostructures could be modified by deposition of metal atoms or small clusters, but there is no information to date on the atomic level details of metal-ceria interactions involving the (110) surface. This paper presents the results of density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U) calculations of the adsorption of a number of different metal atoms at an extended ceria (110) surface; the metals are Au, Ag, Cu, Al, Ga, In, La, Ce, V, Cr, and Fe. Upon adsorption all metals are oxidised, transferring electron(s) to the surface, resulting in localised surface distortions. The precise details depend on the identity of the metal atom. Au, Ag, Cu each transfer one electron to the surface, reducing one Ce ion to Ce(3+), while of the trivalent metals, Al and La are fully oxidised, but Ga and In are only partially oxidised. Ce and the transition metals are also partially oxidised, with the number of reduced Ce ions possible in this surface no more than three per adsorbed metal atom. The predicted oxidation states of the adsorbed metal atoms should be testable in experiments on ceria nanostructures modified with metal atoms.     

Synthesis and crystal structure of complex of Ce(NO_3)_3 with N-(3-methyl-pyridin-2-yl)-formimidoyl-(3-methyl-pyridin-2-yl) hydrazone

Rare earth complexes with organic ligands have been used as luminescence-material usually. Except their luminescent property, the complexes of trivalent lanthanide ions have low toxicity and powerful para-magnetic properties[1,2], so the lanthanide complexes are associated with important biological uses as diag-nostic tools and medicines[36]. Recently, there are some reports on Ce(III) complexes, some of which show anti-cancer activities[7]. S- tetrazines can be used as poly-dentate chelatin…     

含双齿酸性烯醇式β-双酮的十配位稀土金属配合物[Ce(NO3)2(phen)2(CH3COCHCOCH3)]·H2O的合成与晶体结构

标题化合物由邻菲罗啉和乙酰丙酮等在无水乙醇和蒸馏水的混合溶剂中合成 ,用IR谱和X射线结构分析进行表征。晶体学数据如下 :C2 9H2 5N6O9Ce ,Mr=741.6 7,单斜 ,a =1.1110 ( 2 )nm ,b =0 .9834( 2 )nm ,c =1.344 9( 3)nm ,β =10 2 .0 3( 3)°,V =1.4371( 5 )nm3 ,Z =2 ,Dc=1.714kg·m- 3 ,F( 0 0 0 ) =742 ,μ(MoKα) =1.6 5 0mm- 1 ,R =0 .0 42。结果表明 ,具有十配位的中心Ce+3 含有一个双齿负离子烯醇式的β 双酮作为配体。对乙酰丙酮以双齿酸性烯醇式与Ce的配合型式进行了讨论     

NaCl溶液中纤连蛋白在TiO_2表面吸附的动力学模拟

对NaCl水溶液环境中,纤连蛋白(FNIII_(10))分子在金红石型TiO_2 (110)表面的吸附行为进行了分子动力学模拟.根据模拟溶液各成分与TiO_2表面原子之间的径向分布函数、离子在水溶液中的扩散系数及FNIII10和离子的吸附构象等相关参数发现,分布于TiO_2表面的稳定双层水分子是固液界面的主要特征,FNIII10分子通过天冬氨酸残基侧链末端的羧基基团(COO~-)同表面Ti原子之间的强相互作用,结合赖氨酸残基侧链及位于FNIII_(10)始端的精氨酸残基N端的氨基基团(NH_3~+)与表面桥氧原子之间的氢键作用,牢固地吸附在TiO_2表面.溶液中吸附在TiO_2表面的Na~+可与羧基氧原子配合形成稳定的吸附构型,而分布在第二水层外侧的Cl-对纤连蛋白分子在TiO_2(110)表面的吸附点位基本无影响.     

长期低剂量饲喂稀土对大白鼠体重及基因组DNA的影响

利用Operon公司C ,D ,E 3组共 60个引物对饲喂不同浓度稀土的大白鼠基因组DNA进行了RAPD分析 ,共获得了 1 71个DNA片段 ,其中有 4个片段呈多态性。实验表明这些片段均与饲喂稀土无关 ,提示稀土对大白鼠基因组DNA并不造成影响 ;但是大白鼠体重测定显示 ,高浓度时大白鼠增长明显低于对照组 ,说明稀土具有一定的毒性。     

On the interaction of Mg with the (111) and (110) surfaces of ceria

The catalytic activity of cerium dioxide can be modified by deposition of alkaline earth oxide layers or nanoparticles or by substitutional doping of metal cations at the Ce site in ceria. In order to understand the effect of Mg oxide deposition and doping, a combination of experiment and first principles simulations is a powerful tool. In this paper, we examine the interaction of Mg with the ceria (111) surface using both angle resolved X-ray (ARXPS) and resonant (RPES) photoelectron spectroscopy measurements and density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U). With DFT + U, we also examine the interaction of Mg with the ceria (110) surface. The experiments show that upon deposition of Mg, Ce ions are reduced to Ce(3+), while Mg is oxidised. When Mg is incorporated into ceria, no reduced Ce(3+) ions are found and oxygen vacancies are present. The DFT + U simulations show that each Mg that is introduced leads to formation of two reduced Ce(3+) ions. When Mg is incorporated at a Ce site in the (111) surface, one oxygen vacancy is formed for each Mg to compensate the different valencies, so that all Ce ions are oxidised. The behaviour of Mg upon interaction with the (110) surface is the same as with the (111) surface. The combined results provide a basis for deeper insights into the catalytic behaviour of ceria-based mixed oxide catalysts.     

Pretreatment of switchgrass by ammonia fiber explosion (AFEX)

The effects of ammonia fiber explosion (AFEX) pretreatment of switch grass using its major process variables are reported. The optimal pretreatment conditions for switchgrass were found to be near 100°C reactor temperature, and ammonia loading of 1:1 kg of ammonia: kg of dry matter with 80% moisture content (dry weight basis [dwb]) at 5 min residence time. Hydrolysis results of AFEX-treated and untreated samples showed 93% vs 16% glucan conversion, respectively. The ethanol yield of optimized AFEX-treated switchgrass was measured to be about 0.2 g ethanol/g dry biomass, which is 2.5 times more than that of the untreated sample.     

硝酸铈及热处理对化学镀Ni-W-P合金的性能影响

为提高化学镀Ni-W-P镀层的耐蚀性和耐磨性,拓宽其应用,采用电化学方法和热处理等手段,研究了镀液中添加剂硝酸铈(Ce(NO3)3)的质量分数和热处理对化学镀Ni-W-P镀层的沉积速度、孔隙率、失重腐蚀速度、腐蚀电位、腐蚀电流、交流阻抗、显微硬度、摩擦系数等性能的影响。结果表明:添加1.0 wt%Ce(NO3)3时,所得镀层的沉积速度最大(36.5 g/m2·h),孔隙率最低(0.8个/cm2),耐腐蚀性能最好。镀层的组织均匀、致密、无缺陷和非晶态结构是其耐蚀性能高的重要原因。100~600℃热处理后,镀层硬度和耐磨性有所提高,而400℃热处理之后,合金显微硬度高达1100 HV,是镀态的1.8倍。     

Investigation of the interaction of Ce(IV) with diethylenetriaminepentaacetic acid

Conclusions The formation of a neutral monocomplex of Ce(IV) with diethylenetriaminepentaacetic acid was found by a spectrophotometric method. The instability constant of the complex at =1.0 and pH 1.4, the value of which was equal to (0.8±0.2)·10^–34, was calculated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2186–2189, October, 1970.     

过渡金属替代的CeO_2(111)表面上NO+CO反应机理的理论研究(英文)

采用DFT+U方法研究了过渡金属替代的CeO2(111)表面上的NO+CO反应机理,以探求不同过渡金属对N2选择性的影响.结果表明,在反应过程中,反应活性中心由过渡金属单原子与其最近邻的氧空位组成.NO在过渡金属-氧空位上发生N–O断键,不同过渡金属上该还原步骤的难易程度不同.计算发现,右过渡金属Rh,Pd和Pt替代的CeO2(111)表面可以与吸附物之间形成较强的吸附作用,进而可以达到较高的N2选择性.其主要原因是右过渡金属具有较多的d电子,可以与吸附小分子之间形成有效的反馈键.而左过渡金属拥有较少的d电子,难以有效抓住吸附物,最终导致较低的N2选择性.     

Adsorption of NO and CO and specific features of their interaction on the Pt(100) surface

This article presents an analytical review of the author’s results and the literature concerning the nature of species resulting from NO and CO adsorption on the unreconstructed (1 × 1) and reconstructed hexagonal (hex) Pt(100) surfaces, including specific features of the reactions between these species. At 300 K, both surfaces adsorb NO and CO mainly in their molecular states. When adsorbed on Pt(100)-1 × 1, the NO_ads and CO_ads molecules are uniformly distributed on the surface. Under the same conditions, the hexagonal surface undergoes adsorption-induced reconstruction with the formation of NO_ads/1 × 1 and CO_ads/1 × 1 islands, which are areas of the unreconstructed phase saturated with adsorbed molecules and surrounded with the adsorbate-free hex phase. In adsorption on structurally heterogeneous surfaces containing both hex and 1 × 1 areas, the 1 × 1 and hex phases are occupied in succession, the latter undergoing reconstruction into the 1 × 1 phase. The reaction between NO and CO on the unreconstructed surfaces occurs even at room temperature and results in the formation of N₂ and CO₂ in quantitative yield. On the hexagonal surface, a stable layer of adsorbed molecules as (NO_ads + CO_ads)/1 × 1 mixed islands forms under these conditions. Above 350 K, the reaction in the mixed islands is initiated by the desorption of small amounts of the initial compounds, and this is followed by rapid self-acceleration leading to a surface explosion yielding N₂, CO₂, and N₂O (minor product). These products show themselves as very narrow desorption peaks in the temperature-programmed reaction spectrum.     

Chemiluminecsence in the oxidation of Na2C60 by the (NH4)2Ce(NO3)6 complex in THF

Chemiluminescence (_max = 790 nm) in the oxidation of fulleride Na₂C₆₀ by the (NH₄)₂Ce(NO₃)₆ complex in THF was found. The ³C₆₀* triplet of fullerene formed in the transfer of an electron from the intermediate C₆₀ ^– anion to Ce^IV was suggested to be the chemiluminescence emitter.     

Synthesis,X-ray structure and properties of the trinuclear copper(I) complex [Cu3(dppm)3(NO3)(OH)](NO3)

The novel trinuclear Cu^I complex [Cu₃(dppm)₃(NO₃)(OH)](NO₃) obtained by reacting dppm with Cu(NO₃)₂ · 3H₂O in the presence of NaBPh₄ was characterized by a single-crystal X-ray analysis as well as by physico-chemical and spectroscopic methods. The [Cu₃(dppm)₃(NO₃)(OH)]⁺ cation consists of a triangular array of copper atoms, (with dppm ligands bridging each edge of the triangle), a triply bridging OH group and NO^– ₃ anion bound to two faces of the Cu₃ unit, respectively.     

壳寡糖与硝酸钕配合物的合成和配位机理研究

用壳寡糖与硝酸钕反应,制备了壳寡糖-钕配合物。用红外光谱和X射线光电子能谱等分析测试手段对配合物进行了表征。从IR和XPS的测试结果可知,Nd^3＋与壳寡糖上的氨基N和仲羟基O配位,形成壳寡糖-钕配位聚合物。通过电导率研究其配位数,发现Nd^3＋可与壳寡糖的4个链节单元配位.根据以上的实验可推定中心离子Nd^3＋与壳寡糖4个链节单元上的氨基N和仲羟基O结合,形成八配位的壳寡糖-钕配位聚合物。     

磷酸对二氧化铈催化剂氨选择性催化还原氮氧化物反应的促进作用(英文)

氮氧化物NO_x(NO和NO_2)对大气的污染日益严重,主要表现为形成酸雨、导致光化学烟雾和产生温室效应等,严重危害人类健康.氨气选择性催化还原(NH_3-SCR)NO_x是目前最有效的固定源NO_x消除技术.工业中常用的催化剂主要是V_2O_5-WO_3/TiO_2,但其活性组分V_2O_5有毒,且存在氧化能力较强和操作温度窗口过窄等缺点.开发新型环境友好的非钒基NH_3-SCR催化剂体系己成为NO_x催化净化领域的研究热点.CeO_2在稀土市场中占有很大比重且相对廉价,同时还具有优异的氧化-还原及储氧性能,因此开发Ce基SCR脱硝催化剂具有非常好的发展前景.对于NH_3-SCR反应,催化剂必须同时具有酸性位和氧化还原中心.酸性位有利于还原剂NH_3的吸附与活化,而氧化还原中心可以促使氧化剂和还原剂之间发生反应.对于低温SCR催化剂,表面酸性适中即可,氧化还原性能起决定作用;而对于中高温SCR催化剂,不仅要提高其表面酸性以保证足够的NH_3吸附量,同时还要控制其表面氧化性不宜太强,否则在高温段NH_3氧化,N_2选择性下降,NO转化率降低.CeO_2具有一定碱性以及优异的氧化还原性能,因此在高温阶段CeO_2催化剂上易发生NH_3深度氧化,高温NH_3-SCR活性差,温度窗口窄.为了拓宽CeO_2基催化剂的温度窗口,改善其催化性能,有必要调整CeO_2的氧化还原性能和酸碱性能.过渡金属磷酸盐或焦磷酸盐具有特殊的表面酸性和氧化还原性,被广泛应用于多种催化反应.考虑到过渡金属磷酸盐或焦磷酸盐表面同时具有酸性位和氧化还原中心,因而可用于NH_3-SCR反应.最近本课题组通过水热法制备了一种环境友好的Ce-P-O催化剂,该催化剂在较宽的温度范围(300-550℃)内表现出较高的催化NO转化能力,同时具有较强的抗碱和耐硫能力,显示出很好的应用前景.此外,硫酸盐和镍盐修饰能有效改善铈锆固溶体催化剂的NH_3-SCR性能:镍修饰增强了铈锆固溶体的Lewis酸性,有利于提高催化剂的低温活性,而硫酸盐改性提高了催化剂的Bronsted酸性,因此有利于催化剂高温下吸附NH_3,抑制了NH_3的过度氧化.另外,磷酸盐修饰能提高铈锆固溶体催化剂NH_3-SCR反应活性.然而,有关催化剂结构系统表征鲜见报道,催化剂的构效关系阐述不够详细.本文采用浸渍法将不同量的H_3PO_4负载于CeO_2上制备了H_3PO_4修饰的CeO_2催化剂,发现H_3PO_4修饰能显著改善CeO_2催化剂的NH_3-SCR性能.本文对催化剂结构进行了系统表征,详细探讨了H_3PO_4促进作用的原因.NH_3-SCR活性测试显示,H_3PO_4修饰后,催化剂活性显著提高,部分抑制了高温时CeO_2催化剂上NH_3的直接氧化,提高了SCR反应的选择性,从而拓宽了温度窗口.X射线衍射、红外光谱和拉曼光谱表征结果发现,随着H_3PO_4负载量增加,样品中CeO_2相逐渐减少,而新相如CeP_2O_7和Ce(PO_3)_4等逐渐增多,多磷酸根阴离子可能是表面酸性增强的关键因素.NH_3程序升温脱附和吸附吡啶红外光谱结果表明,随着H_3PO_4修饰量的增加,样品的酸强度逐渐增大,Lewis酸性逐渐减弱至消失,而Bronsted酸性逐渐增强.增强的Bronsted酸性可能归因于H_3PO_4修饰后样品表面不断增加的P-OH基团.相对于Lewis酸,Bronsted酸性位氧化能力更弱,可以抑制高温下NH_2(ads)继续脱氢,避免了NH_3深度氧化.程序升温还原测试结果表明,H_3PO_4修饰后,各还原峰向高温偏移,偏移量随H_3PO_4负载量增加而增加.这说明H_3PO_4修饰后CeO_2的氧化还原能力降低,抑制了高温下NH_3的过度氧化.因此,H_3PO_4的修饰使得CeO_2催化剂高温NH_3-SCR活性和N_2选择性大幅提高.综上所述,H_3PO_4-CeO_2样品优异的脱硝催化活性可能归因于H_3PO_4修饰后催化剂酸性,尤其是Bronsted酸性的增强以及氧化还原性的降低.     

Synthesis of Cu3Sn Alloy Nanocrystals through Sequential Reduction Induced by Gradual Increase of the Reaction Temperature

Cu₃Sn alloy nanocrystals are synthesized by sequential reduction of Cu and Sn precursors through a gradual increase of the reaction temperature. By transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), UV/Vis spectroscopy, and X‐ray diffraction (XRD) analyses, the alloy formation mechanism of Cu₃Sn nanocrystals has been studied. The incremental increase of the reaction temperature sequentially induces the reduction of Sn, the diffusion of Sn into the preformed Cu nanocrystals, resulting in the intermediate phase of Cu–Sn alloy nanocrystals, and then the formation of Cu₃Sn alloy nanocrystals. We anticipate that the synthesis of Cu₃Sn alloy nanocrystals encourages studies toward the synthesis of various alloy nanomaterials.     

AgmC60(OH)n(NO3)m的合成及其热稳定性

自从富勒烯被发现并克量级制备以来,富勒烯独特的结构和性质引起了人们极大兴趣和关注,对富勒烯及其衍生物的研究已迅速发展[1],由于C60具有光诱导剪切DNA、抑制艾滋病毒等特性,因而在生物化学及医学方面具有潜在应用前景,其中水溶性富勒烯衍生物的研究是富勒烯化学较为活跃的研究领域之一[2～5],尤其是羟基化富勒烯(或称富勒醇fullerenols)的合成方向的研究[5]。目前富勒烯羟基衍生物的合成方法已得以深入研究,但其化学反应性能的研究未见报道,本文合成了羟基C60银盐,并对其热稳定性能进行了研究。1　实验部分1 1　主要仪器及试剂C6…     

Studies on the interaction of poly(4-vinylpyridiniumchloride) with poly(sodiumphosphate) in an aqueous solution by conductometry

A reaction between poly(4-vinylpyridiniumchloride) and poly(sodiumphosphate) in the presence and absence of NaCl and NaBr salts was studied in aqueous solution by conductometry. The interaction of polycation and polyanion gave insoluble polyelectrolyte complex which contained polycation and polyanion in unit mole ratio in a salt-free solution. A deviation from stoichiometry was observed at high polyion concentration and in the presence of NaCl and NaBr salts. The resultant complex showed swelling property in different solvent mixtures. A maximum degree of swelling was obtained in the solvent mixture of NaBr + water and NaBr + water + acetone. Furthermore, polyelectrolyte complex sorbed salts from aqueous electrolyte solutions. The sorption of salts increased with increasing salt concentration. © 1996 John Wiley & Sons, Inc.