钨过氧酸盐离子液体催化过氧化氢氧化苯甲醇制苯甲酸

用甲基三辛基氯化铵和钨酸钠一步法合成甲基三辛基季铵钨酸盐离子液体[(CH3)N(n-C8H17)3]2W2O11,以该离子液体为催化剂,在无反应溶剂条件下催化过氧化氢氧化苯甲醇生成苯甲酸。 考察了反应温度、催化剂用量以及氧化剂过氧化氢用量对苯甲酸产率的影响。 确定优化条件：反应温度70 ℃,苯甲醇用量5 mmol,催化剂用量是底物的0.4%(摩尔分数),30%过氧化氢用量2 mL,苯甲醇的转化率可达99%,苯甲酸选择性为98%。 该方法具有反应条件温和、产率高和选择性好的优点。     

Pd/PMO-SBA-15 催化剂催化苯甲醇选择氧化反应性能

 研究了 PMO-SBA-15 材料负载的金属钯纳米粒子 (Pd/PMO-SBA-15) 在水相中催化苯甲醇选择氧化制苯甲醛的反应. 考察了纳米粒子种类、氧化剂用量、反应时间和反应温度等对苯甲醇转化率及苯甲醛选择性的影响. 结果表明, 以水为溶剂, 以 H2O2 (30%) 为氧化剂时, 可得到较高的苯甲醇转化率和苯甲醛选择性. 当以 0.05 g 的 2%Pd/PMO-SBA-15 为催化剂, H2O2 用量为 1.5 ml, 反应温度为 80 oC, 反应 4 h 时, 苯甲醇转化率和苯甲醛选择性分别达到 97.1% 和 100.0%. 对该催化体系的重复使用性能进行了考察. 结果发现, 随着使用次数的增加, 苯甲醇转化率有所下降, 但苯甲醛选择性保持不变.     

离子交换法制备Pt-Sn_E/Mg(Al)O催化剂及其烷烃催化脱氢性能

以水滑石为载体,采用离子交换法制备了Pt-Sn_E/Mg(Al)O催化剂,并对其进行了X射线衍射、N2物理吸附、透射电镜等技术表征;考察了该离子交换法制备的Pt-SnE/Mg(Al)O催化剂对乙烷和丙烷脱氢的催化性能,并与浸渍法制备的Pt-SnI/Mg(Al)O催化剂进行了比较。结果表明,利用离子交换法制备的Pt-SnE/Mg(Al)O催化剂其反应活性和稳定性明显优于浸渍法制备Pt-SnI/Mg(Al)O催化剂的。在相同条件下反应2 h后,Pt-SnE/Mg(Al)O催化剂和Pt-SnI/Mg(Al)O催化剂的乙烷催化脱氢转化率分别为12.2%和3.1%,丙烷催化脱氢转化率分别为38.7%和26.4%。     

催化氧化合成邻苯二甲醛工艺的响应面优化的研究

以制备的Co/Mo/γ-Al_2O_3为催化剂,采用过氧化氢催化氧化工艺合成邻苯二甲醛,在前期实验基础上,通过响应面法对邻苯二甲醛的合成工艺参数进行了优化,选用Box-Behnken对实验进行设计,研究了对反应有较大影响的反应时间、反应温度及过氧化氢加量三个因素对邻苯二甲醛收率的影响,得到最佳工艺条件并进行模型的建立。实验表明:过氧化氢催化氧化合成邻苯二甲醛的优化工艺条件为:邻苯二甲醇的加量为5g,30%过氧化氢加量15g,反应温度为81℃,反应时间为3h,催化剂为0. 3g,邻苯二甲醛收率可达51. 4%。使用傅里叶红外光谱、核磁共振氢谱、气相色谱对产品结构进行了分析表征。     

十聚钨酸盐催化环己醇制备环己酮工艺研究

合成新型N-甲基吗啉十聚钨酸盐[Mor1,2]4W10O32,对其进行提纯、表征和催化性能研究。催化体系是以[Mor1,2]4W10O32为催化剂,30%H2O2为氧化剂,催化氧化环己醇制备环己酮。考察催化剂用量、氧化剂用量、反应温度变化和反应时间变化对环己酮产率的影响,确定最佳反应条件为:反应温度80℃、环己醇用量5mmol、催化剂用量30μmol、氧化剂H2O2用量12.5 mmol,反应时间6小时,此时环己酮产率可达到96%。     

镁铝水滑石负载MnO-4催化氧化乙苯合成苯乙酮

采用焙烧还原法制备了镁铝水滑石负载MnO4-催化剂,并将其应用于催化氧气氧化乙苯合成苯乙酮的反应中。考察了催化剂用量、反应温度、反应时间、MnO4-负载量和镁铝比等因素对催化氧化反应的影响及催化剂的重复使用性能。在优化条件下:催化剂用量3 g,乙苯用量45 mL,反应温度120℃,水滑石结构中n(Mg)/n(Al)=5,氧气流量100 mL/min,苯乙酮产率可达57.0%,苯乙酮选择性可达96.3%,催化剂重复使用3次催化活性降低较小。     

磷钼杂多蓝作为反应控制相转移催化剂

设计合成了第一个由磷钼杂多蓝作为反应控制相转移催化剂的反应体系,用于对环己烯进行催化环氧化,苯甲醇进行催化氧化.在体系中,催化剂以均相的方式催化反应,以多相的方式分离回收.催化剂显示了很高的催化活性和稳定性.在催化氧化苯甲醇的反应中,H₂O₂的利用率为100%,苯甲醛的选择性为100%.     

负载Cr(VI)纳米Fe_3O_4磁性高分子材料的催化性能

采用氨基功能化纳米Fe3O4磁性高分子材料(NH2-NMPs)处理含Cr(VI)水溶液,得到了吸附重金属Cr(VI)后回收材料(Cr-NH2-NMPs).通过透射电镜(TEM)、振动样品磁强计(VSM)、热重差热分析(TGA)、X射线粉末衍射(XRD)、红外光谱(FTIR)等对其进行表征.着重研究了以苯甲醇为底物,30%的H2O2为氧化剂,Cr-NH2-NMPs对醇的选择性氧化的催化性能.详细考察了H2O2用量与加入方式、反应时间、反应温度、反应体系中加入酸的种类与用量、催化剂用量、溶剂种类等因素对催化氧化性能的影响,推导出可能的催化机理.结果表明:吸附重金属Cr(VI)后回收材料(Cr-NH2-NMPs)能有效催化苯甲醇氧化至苯甲醛.反应温度为70℃,环己烷为溶剂,在适量质子酸作用下,H2O2与苯甲醇的物质的量比为3.2:1时,苯甲醇的转化率及苯甲醛的选择性均达100%,可以实现"变废为宝"的目的.     

介孔载体嫁接的Schiff碱铬配合物催化氧化苯甲醇合成苯甲醛

将Cr(salen)配合物分别嫁接于介孔SiO2,MCM-41和SBA-15上制备成非均相Schiff碱铬配合物,并用FT-IR,UV-Vis,XRD,N2吸附和元素分析等对非均相铬配合物进行了表征.以30%的H2O2为氧化剂,以非均相铬配合物为催化剂,在无有机溶剂、相转移催化剂和添加剂的条件下,研究了选择性催化氧化苯甲醇合成苯甲醛的反应.结果表明,非均相铬配合物都表现出较好的催化性能.选择不同的介孔载体对非均相铬配合物的催化性能有较大的影响,Cr(salen)/MCM-41配合物显示有最好的催化性能;在优化的反应条件下,苯甲醇转化率可达52.5%,苯甲醛选择性为100%,且该非均相铬配合物重复使用4次后仍保持较好的催化性能.     

Mo-Sn催化剂上甲醇低温氧化制甲缩醛

采用水热合成法制备了甲醇合成甲缩醛的新型Mo-Sn催化剂。该催化剂可以在低Mo含量时实现甲醇低温氧化高选择性制取甲缩醛。通过考察Mo含量对催化剂结构及甲醇低温氧化制甲缩醛性能的影响,发现Mo1Sn10催化剂在甲醇氧化中表现出了较好的催化性能,在140℃、常压反应条件下,甲醇转化率为14.2%,甲缩醛选择性达到了88.9%,并且反应过程中无COx生成。采用XRD、Raman、FT-IR、XPS、NH3-TPD及H2-TPR等表征手段对催化剂进行深入研究。结果表明,不同Mo含量的催化剂结构性能存在着明显的差别,较低含量Mo的存在更有利于Mo~(5+)及MoOx的生成,而由此引起的酸性及氧化还原性的变化是催化剂具有良好性能的重要原因。     

SBA-15负载钒氧化物催化剂上甲烷选择氧化反应

对SBA-15负载的钒、钼、钨氧化物催化的甲烷选择氧化反应性能进行了比较,发现VO_x/SBA-15催化剂优于MoOx/SBA-15和WOx/SBA-15催化剂.针对钒氧化物催化剂,考察了不同钒源、不同载体以及少量P元素的添加对催化性能的影响,结果表明以SBA-15为载体的催化剂的性能好于MCM-41和Cab-O-Sil为载体的催化剂;与V₂O₅,VO(C₂O₄)相比,NH₄VO₃是制备性能良好的VO_x/SBA-15的钒源;在VO_x/SBA-15中,添加少量P元素后,HCHO的选择性有一定程度的提高.XRD,N₂物理吸附、UN-Raman和H₂-TPR表征结果表明,负载量低于3 wt%时,钒组分可能主要以高分散的单核的VO_x物种存在,我们推测该物种对甲烷选择氧化制甲醛起关键作用.     

Preparation and properties of the full series of cuboidal clusters [Mo(x)W4-xSe4(H2O)12]n+ (n = 4-6) and their derivatives

Hydrothermal reactions between incomplete cuboidal cluster aqua complexes [M3Q4(H2O)9]4+ and M(CO)6 (M = Mo, W; Q = S, Se) offer easy access to the corresponding cuboidal clusters M4Q4. The complete series of homometal and mixed Mo/W clusters [Mo(x)W4-xQ4(H2O)12]n+ (x = 0-4, n = 4-6) has been prepared. Upon oxidation of the mixed-metal clusters, it is the W atom which is lost, allowing selective preparation of new trinuclear clusters [Mo2WSe4(H2O)9]4+ and [MoW2Se4(H2O)9]4+. The aqua complexes were converted by ligand exchange reactions into dithiophosphato and thiocyanato complexes, and crystal structures of [W4S4((EtO)2PS2)6], [MoW3S4((EtO)2PS2)6], [Mo4Se4((EtO)2PS2)6], [W4Se4((i-PrO)2PS2)6], and (NH4)6[W4Se4(NCS)12]-4H20 were determined. Cyclic voltammetry was performed on [Mo(x)W4-xCO4(H2O)12]n+, showing reversible redox waves 6+/5+ and 5+/4+. The lower oxidation states are more difficult to access as the number of W atoms increases. The [Mo2WSe4(H2O)9]4+ and [MoW2Se4(H2O)9]4+ species were derivatized into [Mo2WSe4(acac)3(py)3]+ and [MoW2Se4(acac)3(py)3]+, which were also studied by CV. When appropriate, the products were also characterized by FAB-MS and NMR (31P, 1H) data.     

Thermogravimetric investigations of new γ-γ′ cobalt-based superalloys

The aim of the study is characterization of high-temperature oxidation behavior of new Co-based superalloys by thermogravimetry (TG). The following alloys have been taken into account: Co–9Al–9W, Co–20–Ni–7Al–7W, Co–10Al–5Mo–2Nb and Co–20Ni–10Al–5Mo–2Nb (at.%). The thermogravimetric analysis was carried out in the temperature range 40–1200 °C of heating rate 5° min^?1. The investigation was performed using the thermal analyzer NETZSCH STA 449 F3 Jupiter. TG–DTG plots showed oxidation behavior up to 1200 °C and indicated the temperatures of further isothermal oxidation examinations. The oxidation behavior of basic Co–9Al–9W (at.%) alloy was compared to W-free Co–10Al–5Mo–2Nb and Co–20Ni–10Al–5Mo–2Nb (at.%) alloys. The obtained data showed different oxidation behavior dependably on the type of alloying elements. Moreover, the effect of Ni addition on oxidation performance was determined. The scales grown on Co-base superalloys after thermogravimetry were evaluated by means of scanning electron microscopy and energy dispersive spectroscopy.     

Metathesis of nitrogen atoms within triple bonds involving carbon, tungsten, and molybdenum

(ButO)3Mo triple bond N and W2(OBut)6(M triple bond M) react in hydrocarbons to form Mo2(OBut)6(M triple bond M) and (ButO)3W triple bond N via the reactive intermediate MoW(OBut)6(M triple bond M). (ButO)3W triple bond N and CH3C triple bond N15 react in tetrahydrofuran (THF) at room temperature to give an equilibrium mixture involving (ButO)3W triple bond N15 and CH3C triple bond N. The (ButO)3W triple bond N compound is similarly shown to act as a catalyst for N15-atom scrambling between MeC13 triple bond N15 and PhC triple bond N to give a mixture of MeC13 triple bond N and PhC triple bond N15. From studies of degenerate scrambling of N atoms involving (ButO)3W triple bond N and MeC13 triple bond N in THF-d8 by 13C(1H) NMR spectroscopy, the reaction was found to be first order in acetonitrile and the activation parameters were estimated to be DeltaH = 13.4(7) kcal/mol and DeltaS = -32(2) eu. A similar reaction is observed for (ButO)3Mo triple bond N and CH3C triple bond N15 upon heating in THF-d8. The reaction is suppressed in pyridine solutions and not observed for the dimeric [(ButMe2SiO)3W triple bond N]2. The reaction pathway has been investigated by calculations employing density functional theory on the model compounds (MeO)3M triple bond N and CH3C triple bond N where M = Mo and W. The transition state was found to involve a product of the 2 + 2 cycloaddition of M triple bond N and C triple bond N, a planar metalladiazacyclobutadiene. This resembles the pathway calculated for alkyne metathesis involving (MeO)3W triple bond CMe, which modeled the metathesis of (ButO)3W triple bond CBut. The calculations also predict that the energy of the transition state is notably higher for M = Mo relative to M = W.     

Catalytic gas phase oxidation of methanol to formaldehyde

Two gas-phase catalytic cycles for the two-electron oxidation of primary and secondary alcohols were detected by multistage mass spectrometry experiments. A binuclear dimolybdate center [Mo(2)O(6)(OCHR(2))](-) acts as the catalyst in both these cycles. The first cycle proceeds via three steps: (1) reaction of [Mo(2)O(6)(OH)](-) with alcohol R(2)HCOH and elimination of water to form [Mo(2)O(6)(OCHR(2))](-); (2) oxidation of the alkoxo ligand and its elimination as aldehyde or ketone in the rate-determining step; and (3) regeneration of the catalyst via oxidation by nitromethane. Step 2 does not occur at room temperature and requires the use of collisional activation to proceed. The second cycle is similar but differs in the order of reaction with alcohol and nitromethane. The nature of each of these reactions was probed by kinetic measurements and by variation of the substrate alcohols (structure and isotope labeling). The role of the binuclear molybdenum center was assessed by examination of the relative reactivities of the mononuclear [MO(3)(OH)](-) and binuclear [M(2)O(6)(OH)](-) ions (M = Cr, Mo, W). The molybdenum and tungsten binuclear centers [M(2)O(6)(OH)](-) (M = Mo, W) were reactive toward alcohol but the chromium center [Cr(2)O(6)(OH)](-) was not. This is consistent with the expected order of basicity of the hydroxo ligand in these species. The chromium and molybdenum centers [M(2)O(6)(OCHR(2))](-) (M = Cr, Mo) oxidized the alkoxo ligand to aldehyde, while the tungsten center [W(2)O(6)(OCHR(2))](-) did not, instead preferring the non-redox elimination of alkene. This is consistent with the expected order of oxidizing power of the anions. Each of the mononuclear anions [MO(3)(OH)](-) (M = Cr, Mo, W) was inert to reaction with methanol, highlighting the importance of the second MoO(3) unit in these catalytic cycles. Only the dimolybdate center has the mix of properties that allow it to participate in each of the three steps of the two catalytic cycles. The three reactions of these cycles are equivalent to the three essential steps proposed to occur in the industrial oxidation of gaseous methanol to formaldehyde at 300-400 degrees C over solid-state catalysts based upon molybdenum(VI)-trioxide. The new gas-phase catalytic data is compared with those for the heterogeneous process.     

New metal-organic polygons involving MM quadruple bonds: M8(O2CtBu)4(mu-SC4H2-3,4-{CO2}2)6 (M=Mo, W)

The reactions between M2(O2CtBu)4, where M=Mo or W, and thienyl-3,4-dicarboxylic acid (0.5-1.5 equiv) in toluene proceed via a series of detectable intermediates to the compounds M8(O2CtBu)4(mu-SC4H2-3,4-{CO2}2)6, which are isolated as air-sensitive yellow (M=Mo) or red (M=W) powders and show parent molecular ions in their mass spectra (MALDI). The structure of the molybdenum complex was determined by single-crystal X-ray crystallography and shown to contain an unusual M8 polygon involving four Mo2 quadruply bonded units linked via the agency of the six 3,4-thienylcarboxylate groups. The structure has crystallographically imposed S4 symmetry and may be described in terms of a highly distorted tetrahedron of Mo2 units or a bisphenoid in which two Mo2 units are linked by a thienyldicarboxylate such that intramolecular Mo2...O bonding is present, while the other thienylcarboxylate bridges merely serve to link these two [Mo2]...[Mo2] units together. The color of the compounds arises from intense M2 delta-to-thienyl pi transitions and, in THF, the complexes are redox-active and show four successive quasi-reversible oxidation waves. The [M8]+ radical cations, generated by one-electron oxidation with AgPF6, are shown to be valence-trapped (class II) by UV-vis-near-IR and electron paramagnetic resonance spectroscopy. These results are supported by the electronic structure calculations on model compounds M8(O2CH)4(mu-SC4H2-3,4-{CO}2)6 employing density functional theory that reveal only a small splitting of the M2 delta manifold via mixing with the 3,4-thienylcarboxylate pi system.     

Cooperativity of copper and molybdenum centers in polyoxometalate-based electrocatalysts: cyclic voltammetry, EQCM, and AFM characterization

Electrochemical behaviors of selected Dawson-type polytungstates including 2-K10[P2W15Mo2O61box] where the symbol [box] designates a vacant site, alpha2-K7[Fe(OH2)P2W15Mo2O61], alpha2-K8[Cu(OH2)P2W15Mo2O61], alpha1- and alpha2-K8[Cu(OH2)P2W17O61], alpha2-K8[Cu(OH2)P2W13Mo4O61], and alpha2-K8[Cu(OH2)P2W12Mo5O61] were investigated by cyclic voltammetry (CV) coupled with the electrochemical quartz microbalance (EQCM), and the results were completed by atomic force microscopy (AFM) observations of the electrodeposited films. The electrocatalytic abilities of these polyoxometalates (POMs) in the reduction of dioxygen, hydrogen peroxide, and NOx were also assessed by CV and EQCM. It turns out that the remarkable electrocatalysis obtained at the reduction potential of Mo centers within alpha2-K8[Cu(OH2)P2W15Mo2O61], but in a domain where Cu2+ is not deposited, benefits from the assistance of the copper center because such catalysis could not be observed in the absence of Cu2+. EQCM confirms that no copper deposition occurs under the experimental conditions used. Analogous behaviors are encountered in the electrocatalytic reduction of nitrite where assistance by the presence of the Cu2+ center induced the observation of catalysis at the potential location of Mo centers. Finally, the reduction of nitrate is triggered by electrodeposited copper but was remarkably favored by the presence of molybdenum atoms within these polyoxometalates (POMs). All of the results converge to indicate a cooperative effect between the Mo and Cu centers within these POMs. The various results suggest that copper deposition from these POMs should give morphologically different surfaces. AFM studies confirm this expectation, and the observed morphologies and sizes of particles were rationalized by taking into account the role of the POM skeleton and its atomic composition in the electrodeposition process.     

Mono-oxo bis(dithiolene) Mo(IV)/W(IV) complexes as building blocks for sulfide bridged Bi- and Tri-nuclear complexes

A new electron precise, six-electron, sulfide-bicapped trinuclear cluster complex [Et4N]4[Mo(IV)3(mu3-S)2(mnt)6] (1) has been synthesized, where each Mo(IV) atom is seven coordinated. Identical reaction conditions yielded a dimeric complex, [PNP]2[W(V)2(mu2-S)2(mnt)4] (2) from the starting W(IV) analogue due to oxidation by sulfur formed by the auto-oxidation of H2S. Two stepwise reversible reductions and no oxidation of 2 as observed by cyclic voltammetry are correlated with the nonbonding nature of the lowest unoccupied molecular orbital and deeply buried highest occupied molecular orbital by theoretical calculations at the density-functional theory level.     

H_3PMo_(12-n)WnO_(40)·xH_2O的电子光谱与电化学性质研究

系统地考察了H3PMo12 -nWnO4 0 ·xH2 O系列酸在不同溶剂中的电子光谱行为 ,结果表明 ,Mo Ob ,c Mo键在稀水溶液中断裂 ,而在乙醇溶液中能够稳定存在 ;W Ob ,c W键在极稀的水溶液中也能够稳定存在 ;在有机溶剂中所有酸的特征吸收峰均发生红移。电化学性质的研究表明 ,随着分子中钨原子取代数的增多 ,酸的氧化性降低 ,最高还原峰电位和分子中钨原子取代数之间存在一近似线性关系。     

Oxidation-state and metal-ion dependent stereoisomerization in oxo molybdenum and tungsten complexes of a bulky alkoxy heteroscorpionate ligand

Monooxo Mo(V) complexes of a N2O heteroscorpionate ligand designated (L10O) are found to exist as isolable cis and trans isomers. We have been able to trap the kinetically labile cis isomer and follow its isomerization to the thermodynamically more stable trans form. We have also followed the kinetics of isomerization between the cis and trans isomers of the corresponding dioxo Mo(VI) and W(VI) species. Here the trans is the labile isomer that spontaneously converts to the thermodynamically more stable cis. It is observed that at 60 degrees C in DMSO the Mo(VI) complex isomerizes approximately 6.5 times faster than the Mo(V) and nearly 5 times faster than the corresponding W(VI) analogs. The temperature dependence to the kinetics of the Mo(V) and Mo(VI) isomerizations give activation parameters that are similar for both oxidation states and consistent with those previously observed in [(L1O)MoOCl2] suggesting a similar twist mechanism is operating in all cases. Thus there are oxidation state, metal ion and donor atom dependent differences in isomeric stability that could have significant implications for understanding the mechanisms of both enzymatic and nonenzymatic oxo atom transfer reactions catalyzed by complexes of Mo, W and Re.