钯负载锰氧化物基双金属复合氧化物催化氧化羰基化合成碳酸二苯酯

采用共沉淀法分别制备锰掺杂钨、钒、铋3种双金属复合氧化物载体,以氯化钯为活性组分制备负载型催化剂,并用于苯酚氧化羰基化合成碳酸二苯酯（DPC）。通过气相色谱（GC）、X射线衍射（XRD）、氢气程序升温还原（H₂-TPR）、X射线光电子能谱（XPS）等表征手段,对催化剂结构和性能进行表征。结果表明:钨-锰载体随掺杂比例和焙烧温度升高,逐步形成四氧化三锰晶粒,同时钨渗入锰氧化物晶格中,在掺杂比（物质的量比）为1:1、焙烧温度为600 ℃条件下制备的催化剂性能最佳,DPC收率为5.20%;钒-锰载体在焙烧温度为400 ℃、掺杂比为1:5条件下形成二氧化锰晶相,催化剂性能明显提高,DPC收率为10.46%,而较高的焙烧温度会破坏晶型的完整;铋-锰载体在掺杂比为1:5、焙烧温度为400 ℃条件下制备的催化剂催化效果最好,DPC单程收率可达到13.13%。     

The influence of oxidative pretreatment of graphite electrodes on the catalysis of the and redox reactions

Cyclic voltammetry was applied to investigate the and redox couple reactions in HCI electrolytes on highly oriented pyrographite electrodes activated by oxidative pretreatment. The activation effect observed after the oxidative pretreatment was very unstable for the reaction in comparison to the Fe³⁺ reduction. It is thus concluded that acidic surface oxides are participating in the redox reaction. These oxides are reduced, however, in the case of Cr³⁺ reduction near the potential of hydrogen evolution.     

The electronic factor and related redox processes in oxidation catalysis

Catalysis by oxides concern mild selective oxidation as well as total oxidation reactions. Oxides are all semiconductors, either pure, mixed, doped or supported and the redox reactions they catalyse are all connected with their electronic properties. n-Type semiconductors possess anionic vacancies which, when once or twice ionized, are the real oxidative agent of the oxide catalyst. This is illustrated by the Sn–Sb–O system. p-Type oxide semiconductors have positive holes h⁺ as charge carriers, associated with an excess of anionic oxygen. They are illustrated by the case study of vanadyl-pyrophosphate (VO)₂P₂O₇ able to selectively oxidize butane into maleic anhydride in a single pass. In situ measurements of the electrical conductivity of titania during the catalytic oxidation of CO clearly indicated that the oxidizing agent was O⁻ species. All what is described in thermal catalysis can be transposed to photocatalysis at room temperature, with the simultaneous formation of photoelectrons and holes. In dry medium (gas or liquid phase), selective mild oxidation occur involving a neutral activated species O^*, illustrated by the direct oxidation of 4-tert-butyl-toluene into 4-tert-butyl-benzaldehyde.     

聚吡咯/钯中空胶囊的制备及其催化性研究

以单分散的聚苯乙烯为模板,经过一段时间的磺化处理,并使吡咯单体在其表面发生聚合,最终形成导电聚吡咯/聚苯乙烯复合物;同样以单分散的聚苯乙烯为模板,在其表面包覆聚吡咯后,形成的聚吡咯复合物经过溶剂的刻蚀,去除了聚苯乙烯结构,形成聚吡咯中空胶囊,并使用还原剂在其表面负载沉积钯纳米粒子,最终得到的聚吡咯/钯中空胶囊,并对其催化性进行研究。结果表明,这种复合材料在以硼氢化钠为还原剂还原亚甲基蓝的反应中展现了良好的催化活性。     

Homogeneous redox catalysis of the electroreduction of benzyl chloride

The reactions between benzyl chloride and radical anions derived from anthracene and 9,10-diphenylanthracene were studied by cyclic voltammetry and controlled-potential electrolyses in N,N-dimethylformamide solutions, for several concentrations of the aromatic hydrocarbons. The controlled-potential electrolyses for direct and catalytic homogeneous reduction of benzyl chloride on mercury showed toluene as being the main product in both cases. These results were used in the formulation of the overall catalytic mechanisms. The application of a new theoretical treatment for the cyclic voltammetric results, developed recently by Savéant and coworkers, allowed the establishment of the rate determining step and the calculation of the rate constant for the homogeneous electron transfer reaction between the anthracene radical anion and benzyl chloride. This resulted in a value of 1.8 × 10⁴ M^?1 s^?1. For 9,10-diphenylanthracene it was established the existence of a mixed kinetic control under normal experimental conditions. Using very low initial concentrations of the depolarizer it was possible to obtain for the rate constant the value of 5.0 × 10³ M^?1 s^?1.     

Continuous synthesis of palladium nanorods in oxidative segmented flow

Laminar and segmented flow methods are presented for producing Pd rod‐shaped nanostructures from Na₂PdCl₄ in mixtures of water, ethylene glycol, polyvinyl pyrrolidone, and KBr. Synthesis in laminar flow produced an evolution from Pd nanoparticles to short nanorods with residence time. Use of air as the segmentation gas tuned the oxidative environment promoting anisotropic growth of Pd. Moreover, the elevated temperatures (160°C and 190°C) and pressure (0.8 MPa) reduced the synthesis time from hours for most batch systems to 2 min. The ratio of polyol and Pd precursor metal flow streams controlled the anisotropic growth, obtaining nanorods with a diameter approximately 4 nm and an aspect ratio up to 6. Nanorods were single crystal with the {100} lattice spacing of fcc structure, and without any dislocation, stacking fault, or twin defects. The resulting Pd nanorods had high activity at moderate temperature (40ºC) and pressure (0.2 MPa) in the catalytic hydrogenation of styrene. © 2015 American Institute of Chemical Engineers AIChE J, 62: 373–380, 2016     

Bimetallic gold/palladium catalysts for the selective liquid phase oxidation of glycerol

A new methodology for the preparation of single phase bimetallic Au–Pd on activated carbon (AC) has been recently developed and now used for preparing Au/Pd catalysts at different atomic ratio. The bimetallic catalysts have been tested in the liquid phase oxidation on glycerol in water using oxygen as the oxidant and compared with monometallic Au and Pd catalysts. We observed that strong synergistic effect is present in a large range of Au/Pd ratio, being maximized for Au₉₀–Pd₁₀ composition. Gold-rich composition showed an increased durability compared to palladium-rich alloy.     

Coordination,atom reorganization,and catalysis of palladium in zeolite cages

Zeolite encaged palladium clusters undergo thorough atomic reorganizations when exposed to an adsorptive such as carbon monoxide or when used as catalysts e.g. in CO hydrogenation. Exposure to carbon monoxide of metal particles, which are initially anchored to zeolite walls via proton bridges, transforms the metal clusters into small, highly mobile carbonyl clusters. They coalesce and form larger clusters. At low temperature, this process is limited by the geometric constraints of the cage windows. At higher temperatures, further growth of metal particles occurs, conceivably via partial destruction of the zeolite matrix. The interaction of the metal particles with zeolite protons gives rise to electrondeficient metal clusters, which catalyze neopentane at a much higher rate than neutral metal particles. Such clusters might also act as collapsed bifunctional sites in bifunctional catalysis.     

The dicarbonylation and hydrodimerization of unsaturated hydrocarbons via heterogeneous palladium catalysis

Graphite and polymer-supported palladium catalysts, coupled with copper/lithium cocatalysts, have been found very effective for the oxidative carbonylation of unsaturated hydrocarbons. Hex-3-ene-1,6-dioate has been generated in 85% selectivity from 1,3-butadiene,-olefins yield dimethyl succinate derivatives. Butadiene hydrodimerization via analogous platinum catalysis selectively provides 1,6-octadiene, or 2,7-octadienyl formate. Mechanisms for the product selectivity are described.     

A recyclable palladium catalysis in cross-coupling reactions between aroyl chlorides and sodium tetraphenylborate

Aroyl chlorides react with sodium tetraphenylborate in THF at room temperature in the presence of a nano-palladium catalyst prepared from Pd(OAc)₂ and PEG-2000 to give the corresponding diaryl ketones in high yields. The catalytic system could be recovered and reused five times without any loss of catalytic activity.     

Lead corrole complexes in solution: Powerful multielectron transfer reagents for redox catalysis

The first observation of Pb(II)-complexes of corroles and their photoinduced oxidation to the corresponding Pb(IV)-derivatives is reported. These compounds display metal-centered redox chemistry in solution. Their potential for catalytic oxygen atom transfer processes is explored.     

Regioselective carbon-carbon bond formation in proteins with palladium catalysis; new protein chemistry by organometallic chemistry

Palladium-catalyzed reactions have contributed to the advancement of many areas of organic chemistry, in particular, the synthesis of organic compounds such as natural products and polymeric materials. In this study, we have used a Mizoroki-Heck reaction for site-specific carbon-carbon bond formation in the Ras protein. This was performed by the following two steps: 1) the His6-fused Ras protein containing 4-iodo-L-phenylalanine at position 32 (iF32-Ras-His) was prepared by genetic engineering and 2) the aryl iodide group on the iF32-Ras-His was coupled with vinylated biotin in the presence of a palladium catalyst. The biotinylation was confirmed by Western blotting and liquid chromatography-mass spectrometry (LC-MS). The regioselectivity of the Mizoroki-Heck reaction was furthermore confirmed by LC-MS/MS analysis. However, in addition to the biotinylated product (bF32-Ras-His), a dehalogenated product (F32-Ras-His) was detected by LC-MS/MS. This dehalogenation resulted from the undesired termination of the Mizoroki-Heck reaction due to steric and electrostatic hindrance around residue 32. The biotinylated Ras showed binding activity for the Ras-binding domain as its downstream target, Raf-1, with no sign of decomposition. This study is the first report of an application of organometallic chemistry in protein chemistry.     

Enhanced stability of nitrogen-doped carbon-supported palladium catalyst for oxidative carbonylation of phenol

Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst (Pd/NCF) was prepared by supporting Pd ultrafine metal nanoparticles (NPs) on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepar...     

The influence of oxidative pretreatment of graphite electrodes on the catalysis of the Cr3+Cr2+ and Fe3+Fe2+ redox reactions

Cyclic voltammetry was applied to investigate the $\text{Cr}{}^{\mathrm{3+}}\text{Cr}{}^{\mathrm{2+}}$ and $\text{Fe}{}^{\mathrm{3+}}\text{Fe}{}^{\mathrm{2+}}$ redox couple reactions in HCI electrolytes on highly oriented pyrographite electrodes activated by oxidative pretreatment. The activation effect observed after the oxidative pretreatment was very unstable for the $\text{Cr}{}^{\mathrm{3+}}\text{Cr}{}^{\mathrm{2+}}$ reaction in comparison to the Fe³⁺ reduction. It is thus concluded that acidic surface oxides are participating in the redox reaction. These oxides are reduced, however, in the case of Cr³⁺ reduction near the potential of hydrogen evolution.     

Role of acid and redox properties on propane oxidative dehydrogenation over polyoxometallates

Cs_2.5H_1.5PV₁Mo₁₁O₄₀ heteropolyoxometallate compounds have been studied for propane oxidative dehydrogenation (ODH) in the 340–400 °C temperature range. Their redox and Brønsted acid properties have been tuned by introducing a redox metal element M such as Co^II, Fe^III, Ga^III, Ni^II, Sb^III or Zn^II in a V:M atom ratio equal to 1:1. This introduction was carried out either directly in the synthesis solution or by usual aqueous cationic exchange of protons of the solid Cs salt. TGA and FT-IR analyses allowed us to determine the extent of metal M substitution for Mo^VI in the Keggin anion and proton replacement by the M cation. It was observed that, under catalytic conditions (C₃:O₂:He=2:1:2, flow rate 15 cm³ min⁻¹, 12 h on stream), the catalysts were stable, with only a small part of the substituted elements (V and/or M) being extracted from the Keggin anion during the reaction. The presence of these metal M cations enabled us to tune the redox and acid properties of the material and to get high selectivity for propene (60–80% at 5 and 10% propane conversion) at a relatively low temperature (300–400 °C). The direct synthesis method was found more efficient than the classical cationic exchange technique for propane ODH.     

Homogeneous palladium catalyst for the oxidative carbonylation of bisphenol A to polycarbonate in propylene carbonate

Polycarbonates (PCs) were prepared in a propylene carbonate solvent by the oxidative carbonylation of bisphenol A with Pd/bithienyl complexes, Pd/bipyridyl complexes, and Pd C σ-bonded complexes for comparison as homogeneous Pd catalysts. With the Pd/bipyridyl complexes, the 6,6′-disubstituted 2,2′-bipyridyl ligand showed a stronger substituent effect than the 2,2′-bipyridyl ligand, which lacked substituents at the 6,6′ positions. With the Pd/bithienyl complexes, however, the substituent effect was not seen. The Pd/bithienyl complexes, which lacked substituents at the 5,5′ positions, gave a PC yield that was the same as the yield of those that had substituents at the 5,5′ positions. The combination of the Pd C σ-bonded complexes and an inorganoredox cocatalyst showed a PC polymerization behavior that was different from the other two types of complexes. When Co(OAc)₂·4H₂O was used as the inorganoredox cocatalyst, all of the Pd C σ-bonded complexes gave a good PC yield. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Basic characteristics of spinel type manganese mixed oxide/titanium composite anodes for electroorganic redox catalysis

Manganese mixed oxide composite layers of about 1 μm thickness on titanium sheet as substrate were fabricated by firing of the corresponding nitrates at a typical temperature of 400°C in air. The activity of these anodes was evaluated by cyclic voltammetry (10 mV/s) and the stability was determined by chronopotentiometry (2.5 mA/cm²) in 1M H₂SO₄. The oxidation of 2-propanol was examined as a simple electroorganic model reaction. The quality of a first category of mixed oxides with general composition MnMe₂O₄ decresed in the order Me = Co, Ni, Fe. In a second group with the general formula MeMn₂O₄ a decrease in the order Me = Co, Cu, Fe, Ni, Ti, Zn, Cd, Ca, Mg, (Zn, Ge), Li was observed. The corresponding candidates of the second group were superior to those of the first. The anode service life τ of the optimum spinel anode CoMn₂O₄/Ti is dependent on the current density, according to j^λ τ = const. (λ = 1.7). Thus high current densities are precluded. The mechanism has been discussed in terms of a heterogeneous redox catalysis: surface Mn(VII) states are formed in a slow electrochemical step. In a subsequent fast chemical oxidation of the organic molecule the original reduced state is regenerated. This also explains the comparatively good service life of these anodes.     

Organogold reactivity with palladium, nickel, and rhodium: transmetalation, cross-coupling, and dual catalysis

Using two transition metals to simultaneously catalyze a reaction can offer distinct opportunities for reactivity and selectivity when compared to using single-metal catalyst systems. Creating dual transition metal catalytic systems is complicated, however, by challenges in predicting compatible reactivities and designing turnover pathways for both metals. In this Account, we describe our development of dual-metal catalysis reactions involving gold and a second transition metal. The unique rearrangement intermediates accessible through gold-only catalysis, which exploits the soft Lewis acidity of Au(I), make gold an attractive partner for dual-metal catalysis reactions. Because of the complexity of achieving simultaneous turnover of two catalysts and predicting compatibilities, our approach has been to first gain a fundamental understanding of the reactivity of the two metals with each other, both in stoichiometric and monocatalyzed reactions. To this end, we have investigated the combined reactivity of organogold compounds with palladium, nickel, and rhodium. We narrate the intricacies of turning over two catalysts simultaneously and thereby illuminate the valuable role of fundamental studies in identifying the optimal conditions to promote desirable two-metal reactivity and compatibility. Transmetalation, redox reactivity, and new mechanisms for dual-metal catalytic turnover were probed from this standpoint. We have applied the knowledge gained through these studies to the development of reactions that are dual-catalyzed by gold and palladium, as well as nickel- and rhodium-catalyzed reactions of organogold compounds. More broadly, these new reactions expand the reactivity available to catalytic organogold intermediates via trapping and functionalization reactions with other transition metals. Our investigations reveal strategies useful for designing dual-metal reactions with gold. First, the versatility of gold as a transmetalation partner suggests that many potential methods may exist to intercept catalytic organogold intermediates with a second transition metal. Second, ligands on both metals should be selected carefully in order to prevent catalyst deactivation. Finally, reactions must be designed such that any oxidative steps involving the second metal outcompete undesired reactions with redox-active organogold compounds. We believe that the application of these principles will allow for the design of a diverse set of dual-catalyzed functionalizations befitting the wide variety of gold-catalyzed transformations already established.     

Structure and the catalysis mechanism of oxidative chlorination in nanostructural layers of a surface of alumina

On the basis of X-ray diffraction and mass spectrometric analysis of carrier γ-Al₂O₃ and catalysts CuCl₂/CuCl on its surface, the chemical structure of the active centers of two types oxidative chlorination catalysts applied and permeated type of industrial brands “Harshow” and “MEDС-B” was investigated. On the basis of quantum-mechanical theory of the crystal, field complexes were detected by the presence of CuCl₂ cation stoichiometry and structure of the proposed model crystal quasichemical industrial catalyst permeated type MEDС-B for oxidative chlorination of ethylene. On the basis of quantum-mechanical calculations, we propose a new mechanism of catalysis crystal quasichemical oxidative chlorination of ethylene reaction for the catalysts of this type (MEDС-B) and confirmed the possibility of such a mechanism after the analysis of mass spectrometric studies of the active phase (H₂ [CuCl₄]) catalyst oxidative chlorination of ethylene. The possibility of the formation of atomic and molecular chlorine on the oxidative chlorination of ethylene catalyst surface during Deacon reaction was displaying, which may react with ethylene to produce 1,2-dichloroethane. For the active phase (H [CuCl₂]), catalyst offered another model of the metal complex catalyst oxidative chlorination of ethylene deposited type (firm ‘Harshow,’ USA) and the mechanism of catalysis of oxidative chlorination of ethylene with this catalyst.