Effect of Crystallization of Zirconium Hydroxide on the Structure and Isomerization Performance for n-Heptane Hydroisomerization of Ni-WO3/ZrO2

采用XRD、BET、IR、SEM、NH3-TPD方法对以无定形Zr（OH）4和已晶化的ZrO2为载体制备的Ni-WO3/ZrO2催化剂进行了表征,考察了载体晶化对催化剂结构、酸性及催化性能的影响。结果表明,载体晶化减弱了W与Zr间的相互作用,抑制了四方相ZrO2的生成,减少了催化剂上强酸中心的数目,从而降低了Pt-WO3/ZrO2催化剂上正庚烷异构化反应活性.     

WO3/ZrO2固体强酸催化剂上异丁烷-丁烯烷基化反应的研究Ⅲ. 超细ZrO2载体对催化剂性能的影响

制备了以超细ZrO2为载体的WO3/ZrO2、 SO4 2-/ ZrO2、 MoO3/ZrO2固体强酸催化剂 ,并用XRD、 DTA-TG 、 H2-TPR、 NH3-TPD等方法表征了其晶型结构、表面状态和酸性. 结果表明,超细ZrO2及其催化剂均主要以T-晶相存在,与通常以Zr(OH)4为载体制备的同类催化剂相比,ZrO2中的T-晶相所占比例虽有所下降,但具有更大的比表面积、酸强度和对金属氧化物的负载能力,且酸强度随焙烧温度升高而增强,表明其表面状态亦有较大变化. 研究了以超细ZrO2为载体的固体强酸催化剂上, 异丁烷-丁烯的烷基化反应,与通常以Zr(OH)4为载体制得的催化剂相比,其具有更好的烯烃转化率,在烷基化产物中, C5～C7裂解产物较多,使C80的选择性有所下降.     

水合氧化锆的晶化方式对Pt/WO3-ZrO2异构化活性的影响

 采用不同方法制备了一系列具有一定晶相结构的水合 ZrO2, 考察了制备方法对水合 ZrO2 晶化方式及 Pt/WO3-ZrO2 催化剂催化正己烷异构化活性的影响. 采用 X射线衍射, Raman 光谱和 NH3-程序升温脱附对催化剂进行了表征. 结果表明, 水合 ZrO2 的晶化方式与制备时氧气的存在与否有关, 也大大影响了催化剂的异构化活性. 以无氧条件下制备的水合 ZrO2 为载体时, Pt/WO3-ZrO2 催化剂具有较高的异构化活性, 而以在空气气氛中制得的水合 ZrO2 为载体时, Pt/WO3-ZrO2 几乎无异构化活性.     

制备方法对WO_3/ZrO_2结构的影响

用XRD、比表面测定、LRS定性和定量的方法对用Zr（OH）4和已晶化的ZrO2作载体制得的两类WO3／ZrO2催化剂进行了表征．揭示了样品比表面、载体物相、活性组分的存在状态与制备方法、WO3含量、焙烧温度之间的关系．结果表明，WO3能单层分散在ZrO2上；单层覆盖在Zr（OH）4上的WO3使载体在焙烧时晶粒生长受阻，形成介稳的四方ZrO2，并阻止载体微粒间的烧结，使从Zr（OH）4出发制得的WO3／ZrO2比表面明显增大，在WO3含量达到单层分散容量时以上作用表现得最充分；WO3与Zr（OH）4（或四方ZrO2）在高温（～800℃）可能发生了某种化学结合，开创出超强酸位．用以上观点可对文献中已报导的主要实验事实作出较满意的解释.     

Zr基载体负载Pd催化剂用于贫燃天然气汽车尾气净化

 采用共沉淀法制备了 ZrO2, Y0.1Zr0.9Ox, Ce0.1Zr0.9Ox 和 Al0.1Zr0.9Ox 系列 Zr 基载体, 并用 N2 吸附-脱附和 X 射线衍射对其进行了表征. 再以此为载体, 采用浸渍法制备了整体式负载 Pd 催化剂, 催化剂涂层的涂覆量为 180 g/L 左右, Pd 含量为 1.25%. 测定了催化剂上 Pd 的分散度. 在模拟的贫燃天然气汽车尾气中考察了催化剂的活性, 并在尾气中有或无 SO2 存在的条件下比较了催化剂活性的差异. 结果表明, Y3+, Ce4+ 或 Al3+ 改性载体负载的 Pd 催化剂的耐硫性能明显改善; 无论尾气中是否存在 SO2, 以 Y3+ 或 Al3+ 改性载体负载的 Pd 催化剂的活性均明显高于 ZrO2 负载体的 Pd 催化剂.     

Effect of preparation condition on catalytic performance of Ni/ZrO2-SiO2 for methanation of coal gas

采用浸渍法制备了ZrO2-SiO2复合载体和Ni质量分数为6％的Ni/ZrO2 -SiO2催化剂,考察了载体制备时浸渍溶液pH值、焙烧温度和催化剂制备时的焙烧温度对Ni/ZrO2-SiO2催化剂煤气甲烷化反应性能的影响.采用X射线衍射、程序升温还原和扫描电子显微镜等方法对催化剂进行了表征.结果表明,载体浸渍溶液pH值为8.0 ～9.0,载体焙烧温度为550℃,催化剂焙烧温度为450℃时,Ni/ZrO2-SiO2催化剂在煤气甲烷化反应中显示了最优的催化性能,CO转化率100％,CO2转化率1.8％,CH4生成速率16.6 mmol/(h·g).进一步表征发现,制备ZrO2-SiO2复合载体时,增大浸渍溶液的pH值有利于形成粒径较小的亚稳态四方晶相ZrO2,可见四方晶相ZrO2更有利于甲烷化反应;载体焙烧温度会影响到NiO粒径的大小和其在催化剂表面的分散,温度过高和过低都会导致NiO粒径大小的不适宜以及分散性的降低;催化剂焙烧温度过高则会导致NiO与载体间的相互作用减弱,NiO分散性降低.     

稀土氧化物掺杂对SO4^2-／ZrO2／Al2O3催化剂催化性能的影响

采用浸溃-沉淀法在具有较大比表面积的Al2O3上直接合成纳米ZrO2制备负载型纳米ZrO2/Al2O3复合载体,并将氧化钪、氧化钕、氧化错等稀土氧化物(RExOy)分别掺杂到负载型纳米ZrO2/Al2O3复合载体中以改善ZrO2的表面性能.同时以此复合载体负载SO42-制备SO42-/RExOy-ZrO2/Al2O3催化剂.运用XRD,BET,NH3-TPD,原位红外等技术与方法对催化剂的晶相结构、比表面积、孔径分布、酸中心种类等进行表征,并以α-蒎烯异构化反应为探针考察了催化剂的催化性能.结果表明,掺杂的稀土氧化物没有改变ZrO2的晶相结构,但ZrO2粒度有所减小,催化剂的比表面积增加,同时稀土氧化物的存在还会改变催化剂表面SO42-的配位方式,提高表面酸中心数和酸强度,增强催化剂的活性.催化剂的孔结构对选择性有较大的影响.     

纳米ZrO2/Al2O3复合载体及Ni/ZrO2/Al2O3催化剂的性能研究

 采用溶胶-凝胶法在经过扩孔处理的Al2O3基载体上制备了纳米ZrO2/Al2O3复合载体,并通过浸渍法制备了NiO/ZrO2/Al2O3催化剂. 用XRD,TPR,TPD和N2吸附等技术分别考察了载体和催化剂的结构及表面性能,研究了复合载体对Ni/ZrO2/Al2O3催化CO2重整CH4反应性能的影响. 结果表明,纳米ZrO2/Al2O3复合载体具有较大的比表面积、适宜的孔径分布及稳定的t-ZrO2结构,Ni/ZrO2/Al2O3催化剂具有较好的CO2重整CH4反应活性和稳定性.     

Cu/ZrO2催化剂上乙醇水蒸气重整反应的研究 Ⅰ 催化剂性能及其制备参数的影响

研究了Cu/ZrO2催化剂在乙醇水蒸气重整反应中的催化性能。用常规沉淀法、醇凝胶法制备了ZrO2载体；用浸渍法或共沉淀法制备了Cu/ZrO2催化剂。考察了ZrO2载体的制备方法以及Cu/ZrO2的制备参数对催化剂性能的影响。采用BET、XRD、TEM及XRF等方法对催化剂的比表面积、孔容、晶相、表面形貌以及活性组分等进行了表征。同时，制备并比较了Ni/ZrO2、Cu/10MgO-90ZrO2和Cu/10CaO-90ZrO2催化剂的性能，考察了活性组分Cu、Ni的差异以及ZrO2载体的影响。在Cu/ZrO2催化剂(Cu的质量分数为8%)上，500 ℃~600 ℃乙醇转化率达到98%~100％、H2选择性为2.0~2.6（摩尔比）。 Cu/ZrO2与Ni/ZrO2机械混合有助于H2选择性的提高。在催化剂载体中添加MgO、CaO碱性物质可以使H2选择性提高1.3倍~2.0倍。浸渍法制备的Cu/ZrO2催化剂的性能优于共沉淀法。     

稀土氧化物的掺杂量对SO42-/ZrO2/Al2O3催化剂催化性能的影响

采用浸渍-沉淀法制备负载型纳米ZrO2/Al2O3,复合载体,并将不同量的氧化钕、氧化镨掺杂到负载型纳米ZrO2/Al2O3复合载体中以调变ZrO2的表面性能.同时以此复合载体负载SO42-制备SO42-/REXOY-ZrO2/Al2O3催化剂.运用XHD、BET、NH3-TPD、原位红外技术对催化剂的晶相结构、比表面积、孔径分布、酸中心种类等进行表征,并以α-蒎烯异构化为探针反应考察了催化剂的活性.结果表明,适量的稀土掺杂会增加催化剂的比表面积,降低ZrO2的粒径,从而增加催化剂表面SO42-的配位吸附量,提高表面酸中心数和酸强度,增强催化剂的活性.     

n-Hexane Isomerization by Pt/WO3-ZrO2 Using Hydrothermally Synthesized Hydrous Zirconia as Support

A series of hydrous zirconia samples were prepared by the hydrothermal method, and the Pt/WO₃-ZrO₂ catalyst was prepared by impregnation. The effects of hydrothermal temperature of Zr(OH)₄ on the isomerization activity of the catalyst was investigated. The crystalline structure, acidity, and reduction properties of the catalyst were characterized by X-ray diffraction, NH₃ temperature-programmed desorption, and H₂ temperature-programmed reduction, respectively. The results indicated that the crystalline structure of hydrous zirconia and the catalyst varied with the hydrothermal temperature, and the increase of hydrothermal temperature reduced the fraction of tetragonal zirconia. Strong acid sites on the catalyst and the isomerization activity increased with the crystallization of Zr(OH)₄. It was proposed that the higher isomerization activity may be related to the existence of large numbers of strong acid sites.     

以水热法合成的水合氧化锆为载体的Pt／WO3-ZrO2上的正己烷异构化

通过水热法合成了一系列水合氧化锆,以之为载体采用浸渍法制备了Pt/WO3-ZrO2催化剂,考察了氢氧化锆的水热温度对Pt/WO3-ZrO2异构化活性的影响.通过X射线衍射、NH3程序升温脱附及H2程序升温还原表征了样品的晶相结构、酸性及还原性能.结果表明,水合氧化锆及以此为载体的催化剂的晶相结构均随着氢氧化锆水热温度的变化而变化,水热温度升高,四方相氧化锆比例下降.具有一定晶相结构的水合氧化锆为载体的催化剂具有较无定形氢氧化锆为载体的催化剂更多的强酸中心和更高的异构化催化活性.高的异构化活性可能与催化剂上更多的强酸中心有关。     

Synthesis and structure of asymmetric zirconium-substituted silicotungstates, [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3]14- and [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2]10-

The reaction of ZrCl4 with [gamma-SiW10O36]8- in a potassium acetate buffer results in two different products depending on the reactant ratios. The trimeric species [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3]14- (1) consists of three beta23-SiW10O37 units linked by an unprecedented Zr6O2(OH)4(H2O)3 cluster with C1 point group symmetry. The dimeric species [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2]10- (2) consists of beta22- and beta12-SiW10O37 units sandwiching a Zr4O2(OH)2(H2O)4 cluster, which also has C1 symmetry. Polyanion 1 contains more zirconium centers than any other polyoxometalate known to date.     

制备方法对WO3/ZrO2结构的影响

WO3/ZrO2 catalysts prepared from Zr(OH)4 and crystallized ZrO2 have been characterized by means of XRD, LRS (qualitative and quantitative), and the specific sufrace area has been measured. The influence of the preparation method, the contents of WO3 in the samples and the calcination tempearture on the specific surface areas of the samples, the phase of support and the structural states of active component has been studied. The results show: (1) WO3 can disperse on ZrO2 as a monolayer; (2) WO3 dispersed on Zr(OH)4 as a monolayer retards the crystalline growth of the support on calcination, makes it crystallizing into a metastable tetragonal modification, and prevents the inter- crystalline sintering between the crystallites of ZrO2. These factors would result in an increase in the specific surface area of WO3／ZrO2 prepared from Zr(OH)4. As the content of WO3 in the sample comes up to its monolayer capacity, this effect is displayed most fully. A chemical reaction can occur between WO3 and Zr(OH)4 (or the tetragonal ZrO2) at a high temperature(800℃),producing some superacid sites on the surface. By these views, the main experimental facts published in the literatures can been interpreted satisfactotily.     

Adsorption of ammonia by sulfuric acid treated zirconium hydroxide

The adsorption of ammonia on Zr(OH)(4), as well as Zr(OH)(4) treated with sulfuric acid, were examined. The results show that treating Zr(OH)(4) with sulfuric acid leads to the formation of a sulfate on the surface of the material, and that the sulfate contributes to the ammonia adsorption capacity through the formation of an ammonium sulfates species. Calcination of Zr(OH)(4) decreases the ammonia adsorption capacity of the material and limits the formation of sulfate species. NMR and FTIR spectroscopy results are presented that show the presence of two distinct ammonium species on the surface of the material. The adsorption capacity of the materials is shown to be a complex phenomenon that is impacted by the surface area, the sulfur content, and the pH of the material. The results illustrate that Zr(OH)(4), which is known to adsorb acidic gases, can be modified and used to adsorb basic gases.     

Methyltriskaidecazirconates, molecular forms of zirconia

Repeated methanolysis of [Zr(3)O](OPr(n)(10) followed by extraction and crystallization from toluene yields material that is X-ray crystallographically indistinguishable from the compound previously formulated as [Zr(13)O(8)](OMe)(36). Elemental analysis and (1)H solution NMR spectroscopy strongly suggest that this material is a mixture of methyltriskaidecazirconates (MTZ) [Zr(13)O(8)](OMe)(x)(OH)(36)(-)(x), x(av) approximately 20, that readily cocrystallize from hydrocarbon solution. These species have the metal-oxygen framework structure reported for [Zr(13)O(8)](OMe)(36), where the 13 zirconium and 32 bridging oxygen atoms comprise a fragment of the fluorite structure adopted by ZrO(2) at elevated temperatures. Ethanolysis of [Zr(3)O](OPr(n)(10) yields its ethyl analogue, [Zr(3)O](OEt)(10). Both trizirconates display temperature-dependent (1)H solution NMR spectra that are interpreted mechanistically in terms of rearrangement mechanisms involving trigonal twists at the octahedral zirconium centers.     

EXAFS study of aqueous Zr(IV) and Th(IV) complexes in alkaline CaCl(2) solutions: Ca(3)[Zr(OH)(6)](4+) and Ca(4)[Th(OH)(8)](4+)

A hitherto unknown type of aqueous complex, ternary Ca-MIV-OH complexes (M = Zr and Th), causes unexpectedly high solubilities of zirconium(IV) and thorium(IV) hydrous oxides in alkaline CaCl2 solutions (pHc = 10-12, [CaCl2] > 0.05 mol.L(-1), and pHc = 11-12, [CaCl2] > 0.5 mol.L(-1), respectively). The dominant aqueous species are identified as Ca3[Zr(OH)6]4+ and Ca4[Th(OH)8]4+ and characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. The number of OH- ligands in the first coordination sphere detected by EXAFS, NO = 6 (6.6 +/- 1.2) for Zr and NO = 8 (8.6 +/- 1.2) for Th, are consistent with the observed slopes of 2 and 4 in the solubility curves log [M]tot vs pHc. The presence of polynuclear hydrolysis species and the formation of chloride complexes can be excluded. EXAFS spectra clearly show a second coordination shell of calcium ions. The [Zr(OH)6]2- and [Th(OH)8]4- complexes with an unusually large number of OH- ligands are stabilized by the formation of associates or ion pairs with Ca2+ ions. The number of neighboring Ca2+ ions around the [Zr(OH)6]2- and [Th(OH)8]4- units is determined to be NCa = 3 (2.7 +/- 0.6) at a distance of RZr-Ca = 3.38 +/- 0.02 A and NCa = 4 (3.8 +/- 0.5) at a distance of RTh-Ca = 3.98 +/- 0.02 A. The Ca3[Zr(OH)6]4+ and Ca4[Th(OH)8]4+ complexes have first (M-O) and second (M-Ca) coordination spheres with the Ca2+ ions bound to coordination polyhedra edges.     

H_3PO_4/Zr(OH)_4高效促进NBS对取代烷基苯的亲电溴代

使用固体酸H3PO4/Zr(OH)4催化NBS对取代烷基苯进行苯环溴代反应.根据不同取代烷基苯的反应活性,在乙腈中,高产率(79%～96%)地得到了相应的苯环单溴代产物,同时反应体系中无苄位溴代的副产物生成.在反应过程中,固体酸催化剂可以重复使用多次.     

Theoretical Study of Isomerization and Decomposition Reactions for Methyl-nitramine

The complex potential energy surface and reaction mechanisms for the unimolecular isomerization and decomposition of methyl-nitramine (CH3NHNO2) were theoretically probed at the QCISD(T)/6-311+G*//B3LYP/6-311+G* level of theory. The results demonstrated that there are four low-lying energy channels: (i) the NN bond fission pathway; (ii) a sequence of isomerization reactions via CH3NN(OH)O; (IS2a); (iii) the HONO elimination pathway; (iv) the isomerization and the dissociation reactions via CH3NHONO (IS3). The rate constants of each initial step (rate-determining step) for these channels were calculated using the canonical transition state theory. The Arrhenius expressions of the channels over the temperature range 298-2000 K are k6(T)=1014:8e-46:0=RT , k7(T)=1013:7e-42:1=RT , k8(T)=1013:6e-51:8=RT and k9(T)=1015:6e-54:3=RT s-1, respectively. The calculated overall rate constants is 6.9￡10-4 at 543 K, which is in good agreement with the experimental data. Based on the analysis of the rate constants, the dominant pathway is the isomerization reaction to form CH3NN(OH)O at low temperatures, while the NN bond fission and the isomerization reaction to produce CH3NHONO are expected to be competitive with the isomerization reaction to form CH3NN(OH)O at high temperatures.