Preparation and catalytic performances of a molecularly imprinted Ru-complex catalyst with an NH2 binding site on a SiO2 surface

A catalyst surface with an active metal site, a shape-selective reaction space, and an NH(2) binding site for o-fluorobenzophenone was designed and prepared by the molecular imprinting of a supported metal complex on a SiO(2) surface. A ligand of a SiO(2)-supported Ru complex that has a similar shape to the product of o-fluorobenzophenone hydrogenation was used as a template. An NH(2) binding site for o-fluorobenzophenone was spatially arranged on the wall of a molecularly imprinted cavity with a similar shape to the template. The structures of the SiO(2)-supported and molecularly imprinted Ru catalysts were characterized in a step-by-step manner by means of solid-state magic angle spinning (MAS) NMR, XPS, UV/Vis, N(2) adsorption, XRF, and Ru K-edge EXAFS. The molecularly imprinted Ru catalyst exhibited excellent shape selectivity for the transfer hydrogenation of benzophenone derivatives. It was found that the NH(2) binding site on the wall of the molecularly imprinted cavity enhanced the adsorption of o-fluorobenzophenone, of which the reduction product was imprinted, whereas there was no positive effect in the case of o-methylbenzophenone, which cannot interact with the NH(2) binding site through hydrogen bonding.     

Energy-gaining formation and catalytic behavior of active structures in a SiO(2)-supported unsaturated Ru complex catalyst for alkene epoxidation by DFT calculations

The formation and catalytic behavior of active structures in a SiO(2)-supported unsaturated Ru complex catalyst for alkene epoxidation were studied by means of hybrid density functional theory (DFT) calculations. An energy-gaining route for the catalyst activation was found to allow the formation of active unsaturated Ru complexes and the remarkable alkene epoxidation via an exothermic reaction path between isobutyraldehyde and oxygen. In the proposed Bartlett mechanism, Ru promotes the formation of peracid intermediate and facilitates the intermolecular hydrogen transfer in the peracid intermediate, while alkene molecules do not directly coordinate to the Ru site. It was found that stilbene epoxidation is easier to achieve than ethene epoxidation thanks to the electron donating phenyl groups.     

Preparation of surface molecularly imprinted Ru-complex catalysts for asymmetric transfer hydrogenation in water media

Molecularly imprinted Ru-complex catalysts acting in water were prepared on a SiO(2) surface by molecular imprinting of a SiO(2)-supported Ru-complex using organic polymers as surface matrix overlayers. (R)-1-(o-fluorophenyl)ethanol, which is one of the hydrogenated products of o-fluoroacetophenone, was imprinted on the supported Ru-complex as a template, and an active Ru-complex with a shape-selective reaction space (molecularly imprinted cavity) was prepared inside the wall of the hydrophobic organic polymer matrix overlayers. Structures of the SiO(2)-supported and molecularly imprinted Ru catalysts were characterized by means of solid-state NMR, XPS, XRF, ICP, UV/vis, XAFS, TGA, and SEM. The molecularly imprinted Ru catalysts exhibited fine shape selectivity and enantioselectivity for the asymmetric transfer hydrogenation of o-fluoroacetophenone and its derivatives.     

FTIR studies of CO adsorption on Al2O3- and SiO2-supported Ru catalysts

The adsorption of CO on Al2O3- and SiO2-supported Ru catalysts has been investigated through FTIR spectroscopy. Deconvolution of the spectra obtained reveals the presence of 11 distinct bands in the case of Ru/Al2O3 and 10 bands in the case of Ru/SiO2, which were assigned to different carbonyl species adsorbed on reduced as well as partially oxidized Ru sites. Although most of these bands on both supports are similar, they exhibit substantial differences in terms of stability. In general, the analogous CO species on Ru/Al2O3 are adsorbed stronger than those on Ru/SiO2, with the most stable species observed being a dicarbonyl adsorbed on metallic Ru (i.e., Ru0(CO)2). Following sintering of the Ru, the ratio of multicarbonyl to monocarbonyl adsorption is reduced substantially because of the lack of isolated sites or small Ru clusters that enable the formation of multicarbonyl species via oxidative disruption. Finally, in the presence of O2, the main features observed correspond to monocarbonyl, dicarbonyl, and tricarbonyl species adsorbed on partially oxidized Run+. The intensities of all bands decrease drastically at temperatures above 210 degrees C because of the onset of CO oxidation, which results in substantially reduced surface coverage.     

Fabrication of DNA nanowires by orthogonal self-assembly and DNA intercalation on a Au patterned Si/SiO2 surface

A novel Ru complex bearing both an acridine group and anchoring phosphonate groups was immobilized on a surface in order to capture double-stranded DNAs (dsDNAs) from solution. At low surface coverage, the atomic force microscopy (AFM) image revealed the "molecular dot" morphology with the height of the Ru complex ( approximately 2.5 nm) on a mica surface, indicating that four phosphonate anchor groups keep the Ru complex in an upright orientation on the surface. Using a dynamic molecular combing method, the DNA capture efficiency of the Ru complex on a mica surface was examined in terms of the effects of the number of molecular dots and surface hydrophobicity. The immobilized surface could capture DNAs; however, the optimal number of molecular dots on the surface as well as the optimal pull-up speed exist to obtain the extended dsDNAs on the surface. Applying this optimal condition to a Au-patterned Si/SiO 2 (Au/SiO 2) surface, the Au electrode was selectively covered with the Ru complex by orthogonal self-assembly of 4-mercaptbutylphosphonic acid (MBPA), followed by the formation of a Zr (4+)-phosphonate layer and the Ru complex. At the same time, the remaining SiO 2 surface was covered with octylphosphonic acid (OPA) by self-assembly. The selective immobilization of the Ru complex only on the Au electrode was identified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS) imaging on the chemically modified Au/SiO 2 surface. The construction of DNA nanowires on the Au/SiO 2 patterned surface was accomplished by the molecular combing method of the selective immobilized Ru complex on Au electrodes. These interconnected nanowires between Au electrodes were used as a scaffold for the modification of Pd nanoparticles on the DNA. Furthermore, Cu metallization was achieved by electroless plating of Cu metal on a priming of Pd nanoparticles on the Pd-covered DNA nanowires. The resulting Cu nanowires showed a metallic behavior with relatively high resistance.     

Effect of EtOH/MgCl(2) molar ratios on the catalytic properties of MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalyst for ethylene polymerization

MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalysts for ethylene polymerization were prepared by impregnation of MgCl(2) on SiO(2) in heptane and further treatment with TiCl(4). MgCl(2)·nEtOH adduct solutions were prepared with various EtOH/MgCl(2) molar ratios for preparation of the MgCl(2)-supported and MgCl(2)-SiO(2)-supported catalysts in order to investigate the effect on polymerization performance of both catalyst systems. The catalytic activities for ethylene polymerization decreased markedly with increased molar ratios of [EtOH]/[MgCl(2)] for the MgCl(2)-supported catalysts, while for the bi-supported catalysts, the activities only decreased slightly. The MgCl(2)-SiO(2)-supported catalyst had relatively constant activity, independent of the [EtOH]/[MgCl(2)] ratio. The lower [EtOH]/[MgCl(2)] in MgCl(2)-supported catalyst exhibited better catalytic activity. However, for the MgCl(2)-SiO(2)-supported catalyst, MgCl(2) can agglomerate on the SiO(2) surface at low [EtOH]/[MgCl(2)] thus not being not suitable for TiCl(4) loading. It was found that the optimized [EtOH]/[MgCl(2)] value for preparation of bi-supported catalysts having high activity and good spherical morphology with little agglomerated MgCl(2) was 7. Morphological studies indicated that MgCl(2)-SiO(2)-supported catalysts have good morphology with spherical shapes that retain the morphology of SiO(2). The BET measurement revealed that pore size is the key parameter dictating polymerization activity. The TGA profiles of the bi-supported catalyst also confirmed that it was more stable than the mono-supported catalyst, especially in the ethanol removal region.     

担载型钌催化剂吸附CO性能的原位红外研究

用原位红外研究了ＣＯ的吸附与脱附，ＣＯ／Ｈ２的共吸附及反应，考察了焙烧温度对Ｒｕ／Ａｌ２Ｏ３及Ｒｕ／ＳｉＯ２催化剂的影响，结果表明，经不同温度焙烧的催化剂样品，其吸附性能有很大差别。随着焙烧温度的升高，金属－载体相互作用增强，导致ＣＯ吸附量减少。Ｒｕ／Ａｌ２Ｏ３吸附的ＣＯ较稳定，而Ｒｕ／ＳｉＯ２吸附的ＣＯ在高温易脱附。各不同ＣＯ吸会态间、多重态更易发生反应。在未焙烧的Ｒｕ／ＳｉＯ２低ＣＯ／Ｈ２反应     

Mechanistic study of partial oxidation of methane to syngas using in situ time-resolved FTIR and microprobe Raman spectroscopies

In situ time-resolved Fourier transform infrared (FTIR) and microprobe Raman spectroscopies were used to characterize the reaction mechanisms of the partial oxidation of methane to syngas over SiO(2)- and gamma-Al(2)O(3)-supported rhodium and ruthenium catalysts. The interaction of both pure methane and a methane/oxygen mixture at a stoichiometric feed ratio with an oxygen-rich catalyst surface led to the formation of CO2 and H(2)O as the primary products. For the H(2)-pretreated samples, the reaction mechanisms with the catalysts differ. Only Rh/SiO(2) is capable of catalyzing the direct oxidation of methane to syngas, while syngas formation over Rh/gamma-Al(2)O(3), Ru/SiO(2), and Ru/gamma-Al(2)O(3) can be achieved mainly via a combustion-reforming scheme. The significant difference in the mechanisms for partial oxidation of methane to syngas over the catalysts can be correlated to the differences in the concentration of oxygen species (O(2-)) on the catalyst surface during the reaction, mainly due to the difference in the nature of the metals and supports.     

Ru-B/SiO2非晶态催化剂应用于液相葡萄糖加氢制山梨醇

 采用浸渍法结合KBH4还原法制备了Ru-B/SiO2非晶态催化剂(3.14%Ru),并将其用于液相葡萄糖加氢制山梨醇反应. 结果表明,该催化剂具有良好的热稳定性,且其催化活性远高于Raney Ni和Ni-B/SiO2非晶态催化剂,山梨醇的选择性接近于100%,显示出良好的工业化应用前景. 通过与晶态Ru-B/SiO2及Ru/SiO2的催化活性进行比较,并结合ICP,XRD,DSC,SEM,XPS及氢吸附等表征结果,初步讨论了非晶态合金结构和表面电子态对催化剂活性的促进作用.     

Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles: efficient and easily recyclable heterogeneous nanocatalysts

We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO(2)@Pd-PAMAM core-shell microspheres containing SiO(2) microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO(2) microspheres, which were prepared by the St?ber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO(2)-supported epoxides underwent ring-opening and gave SiO(2)@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO(2)-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH(4). This produced the SiO(2)@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO(2)@Pd-PAMAM core-shell microspheres. The SiO(2)@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ~100% conversion and high turnover numbers (TONs) under 10 bar H(2) pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO(2)@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture.     

Design of an NO photoinduced releaser xerogel based on the controlled nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF6)2 (cyclam=1,4,8,11-tetraazacyclotetradecane)

The immobilization and properties of the nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF(6))(2), RuNO, entrapped in a silica matrix by the sol-gel process is reported herein. The entrapped nitrosyl complex was characterized by spectroscopic (UV-vis, infrared (IR), X-ray photoelectron, and (13)C and (29)Si MAS NMR) and electrochemical techniques. The entrapped species exhibit one characteristic absorption band in the UV-vis region of the electronic spectrum at 354 nm and one IR nu(NO) stretching band at 1865 cm(-1), as does the RuNO species in aqueous solution. Our results show that trans-[Ru(NO)Cl(cyclam)](PF(6))(2) can be entrapped in a SiO(2) matrix with preservation of the molecular structure. However, in a SiO(2)/SiNH(2) matrix, the complex undergoes a nucleophilic attack by the amine group at the nitrosonium. Irradiation of the complex, entrapped in the SiO(2) matrix, with light of 334 nm, resulted in NO release. The material was regenerated to its initial nitrosyl form by reaction with nitric oxide.     

以SIO~2为载体的乙烯丙烯共聚高效Ziegler-Natta催化剂

本工作以反应法制备了sio~2负载的乙丙烯共聚高效ziegler-natta催化剂, 考察了Ticl~4/Al~2t~3l~3/Sio~2催化体系的催化效率,发现在无Mgcl~2及Mg系化合物存在下,使催化活性大大提高,并利用ESR对高效的原因进行了初步探讨,得到了一些有意义的结果.     

New polydentate ligand and catalytic properties of the corresponding ruthenium complex during sulfoxidation and alkene epoxidation

Bis(diimine)-ruthenium complexes constitute a class of catalysts with good activity for oxidation reactions, such as sulfoxidation and epoxidation. The synthesis and the full characterization of a new ruthenium complex bearing an original pentadentate ligand (L5pyr for 2,6-bis-(6-ethyl-2,2'-bipyridyl)-pyridine) is reported. Comparison of its activity with regard to[Ru(bpy)2(CH3CN)2](2+) and [Ru(bpy)2(py)(CH3CN)](2+) during alkene and sulfide oxidation allowed us to conclude that the addition of a fifth pyridine ligand in the coordination sphere improves the efficiency of the catalyst. Moreover, under these oxidation conditions a hydroxylation of the ligand L5pyr led to a better activity than its analogue [Ru(bpy)2(py)(CH3CN)](2+), especially during epoxidation of alkenes by PhI(OAc)2.     

Ru-Re/SiO2催化剂上丙三醇氢解制丙二醇:催化剂的酸性质与Re组分的作用

考察了Ru-Re/SiO2 组分催化剂的酸性质,并探讨了Re组分在丙三醇氢解制丙二醇反应中对提高该催化剂性能所起的作用.本文采用氨气程序升温脱附法和吸附吡啶原位红外光谱法表征了双组分Ru.Re/SiO2和单组分Ru/SiO2、Re/SiO2催化剂的酸性质,并比较了催化剂在丙三醇氢解反应中的催化性能.结果显示,Ru-Re...     

Hydrothermal and solid-state transformation of ruthenium-supported Keggin-type heteropolytungstates [XW11O39{Ru(II)(benzene)(H2O)}]n- (X = P (n = 5), Si (n = 6), Ge (n = 6)) to ruthenium-substituted Keggin-type heteropolytungstates

A new pathway for the preparation of mono-ruthenium (Ru)(iii)-substituted Keggin-type heteropolytungstates with an aqua ligand, [PW(11)O(39)Ru(iii)(H(2)O)](4-) (1a), [SiW(11)O(39)Ru(iii)(H(2)O)](5-) (1b) and [GeW(11)O(39)Ru(iii)(H(2)O)](5-) (1c), using [Ru(ii)(benzene)Cl(2)](2) as a Ru source was described. Compounds 1a-1c were prepared by reacting [XW(11)O(39)](n-) (X = P, Si and Ge) with [Ru(ii)(benzene)Cl(2)](2) under hydrothermal condition and were isolated as caesium salts. Ru(benzene)-supported heteropolytungstates, [PW(11)O(39){Ru(ii)(benzene)(H(2)O)}](5-) (2a), [SiW(11)O(39){Ru(ii)(benzene)(H(2)O)}](6-) (2b) and [GeW(11)O(39){Ru(ii)(benzene)(H(2)O)}](6-) (2c), were first produced in the reaction media, and then transformed to 1a, 1b and 1c, respectively, under hydrothermal conditions. Calcination of Ru(benzene)-supported heteropolytungstates, 2a, 2b and 2c, in the solid state produced mixtures of 1a, 1b and 1c with CO (carbon monoxide)-coordinated complexes, [PW(11)O(39)Ru(ii)(CO)](5-) (4a), [SiW(11)O(39)Ru(ii)(CO)](6-) (4b) and [GeW(11)O(39)Ru(ii)(CO)](6-) (4c), respectively. From comparison of their catalytic activities in water oxidation reaction, it was indicated that ruthenium should be incorporated in the heteropolytungstate in order to promote catalytic activity.     

结构助剂SiO2、Al2O3对铁基催化剂浆态床F-T合成性能的影响

采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了微球状Fe/Cu/K/SiO2和Fe/Cu/K/Al2O3催化剂,研究SiO2和Al2O3作为结构助剂对铁基催化剂吸附行为、炭化行为及F-T合成反应性能的影响。表征结果表明,与Al2O3相比较,SiO2抑制了H2的吸附,但促进了CO的吸附,有利于催化剂的炭化。催化剂在260℃、1.5MPa、H2/CO=0.67和2000h-1下的浆态床F-T合成反应评价表明,Fe/Cu/K/SiO2催化剂具有较高的F-T合成活性、高的水煤气变换反应（WGS）活性,且其烃产物选择性明显向高炭数方向偏移,而Fe/Cu/K/Al2O3催化剂则表现出较低的F-T合成活性、低的水煤气变换反应（WGS）活性和高的轻质烃选择性。但Fe/Cu/K/Al2O3催化剂比Fe/Cu/K/SiO2催化剂具有更好的运行稳定性。     

Quantum Chemical Studies on the Mechanism of Producing Oxygenates in Fischer-Tropsch Synthesis on M/SiO2(M = Ni,Ru,Rh,Pd)

EHMO calculations and orbital analyses of fragment;;have been performed for the formation of oxygenates in Fischer-Tropsch synthesis on the butterfly model for four different metal (Ni,Ru,Rh,Pd) catalysts supported on SiO2.Calculations were made for the four processes,i.e.,CO-dissociation;Coupling of CO and H to produce CHO;Insertion of CO to M-CH3;insertion of CH2 to M-CH3 On the basis of comparing the degree of CO bonds activation and the energy barriers of the foregoing processes for these four catalysts,it is concluded that Ni/SiO2 can be used as the methanation catalyst.On Ru/SiO2 and Rh/SiO2 C2-oxygenated compound can be produced (acetaldehyde),especially Rh/SiO2 is the even better catalyst,and Pd/SiO2 is a methanol synthesis catalyst.     

Redox chemistry of tantalum clusters on silica characterized by X-ray absorption spectroscopy

SiO(2)-supported clusters of tantalum were synthesized from adsorbed Ta(CH(2)Ph)(5) by treatment in H(2) at 523 K. The surface species were characterized by X-ray absorption spectroscopy (extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near edge spectroscopy (XANES)) and ultraviolet-visible spectroscopy. The EXAFS data show that SiO(2)-supported tantalum clusters were characterized by a Ta-Ta coordination number of approximately 2, consistent with the presence of tritantalum clusters, on average. When these were reduced in H(2) and reoxidized in O(2), the cluster nuclearity remained essentially unchanged, although reduction and oxidation occurred, respectively, as shown by XANES and UV-vis spectra; in the reoxidation, the tantalum oxidation state change was approximately two electronic charges per tritantalum cluster. The data demonstrate an analogy between the chemistry of group 5 metals on the SiO(2) support and their chemistry in solution, as determined by the group of Cotton.     

SiO2负载型铁系催化剂催化乙烯齐聚的研究

制备了硅胶负载型2,6-二亚胺基吡啶铁系齐聚催化剂。考察了不同负载温度,聚合中乙烯加压方式,催化剂的加入量以及丙烯对乙烯齐聚活性和α-烯烃分布的影响。结果表明,低温负载有利于催化剂活性提高,分段加压可以使催化剂的活性周期增加,聚合温度平稳,单位助催化剂MAO转化的乙烯量增加,而α-烯烃的选择性基本不变。Fe催化剂负载后,以单位助催化剂MAO计算的乙烯转化率提高。增加催化剂的量后,单位助催化剂MAO转化的乙烯量增加。在乙烯齐聚中加入少量丙烯催化剂的活性降低,α-烯烃分布向低碳方向移动。     

二氧化硅负载偏钨酸铵催化剂上邻苯二酚和甲醇气相单醚化反应

考察了SiO2负载的偏钨酸铵催化剂(AMT/SiO2)上邻苯二酚和甲醇气相单醚化反应的性能.结果表明,经533和573K焙烧的AMT/SiO2催化剂表现出较高的邻苯二酚转化率(97%)和主产物邻羟基苯甲醚的选择性(91%).程序升温脱附和吡啶吸附红外光谱结果表明,催化剂表面存在的弱酸-弱碱位是反应的活性中心.经533K焙烧制备的催化剂在反应最初46h内保持较高的稳定性,随着反应时间延长,邻苯二酚的转化率逐渐降低,但主产物的选择性基本保持不变.扫描电镜和差热热重分析结果表明,催化剂表面积炭是其活性下降的主要原因,采用适当的焙烧处理可以消除大部分积炭,从而部分恢复催化剂活性.