Highly reactive and reusable heterogeneous activated carbons-based palladium catalysts for Suzuki-Miyaura reaction

Suzuki-Miyaura reaction of aryl halides with phenylboronic acid using a heterogeneous palladium catalyst based on activated carbons(AC) was systematically investigated in this work. Two different reaction modes(batch procedure and continuous-flow procedure) were used to study the variations of reaction processing. The heterogeneous catalysts presented excellent reactivity and recyclability for iodobenzene and bromobenzene substrates in batch mode, which can be attributed to stabilization of Pd nanoparticles by the thiol and amino groups on the AC supports. However, significant dehalogenation in the reaction mixture and Pd leaching from the heterogeneous catalysts were observed in continuous-flow mode.This unique phenomenon in continuous-flow mode resulted in a dramatic decline in reaction selectivity and durability of heterogeneous catalysts comparing with that of batch mode. In addition, the heterogeneous Pd catalysts with thiol-and amino-modified AC supports exhibited different reactivity and durability in batch and continuous-flow mode owing to the difference of interaction between Pd species and AC supports.

Influence of CeO_2 and La_2O_3 on properties of palladium catalysts used for emission control of natural gas vehicles

Pd/YZ-Al2O3 （Y and Zr modified Al2O3, and hereafter, labelled as A1） catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared and characterized by X-ray photoelectron spectroscopy （XPS）, NO-temperature programmed desorption （NO-TPD）, Nz-adsorption/desorption （Branauer-Emmet-Teller BET method）, X-ray diffraction （XRD） and CO-chemisorption. Catalytic activities for CH4, CO and NO conversion were tested in a gas mixture simulated the emissions from natural gas vehicles （NGVs） operated under stoichiometric conditions. The results indicated that all catalysts exhibited excellent catalytic performances for CH4 and CO oxidation and the promoting effect of CeO2 or La2O3 was significant for NO conversion. XPS results showed that the electron density around Pd was increased by CeO2 and/or La2O3, the binding energy of Pd 3d decreased as the order： Pd/Al 〉 Pd/Ce/Al 〉 Pd/La/Al 〉 Pd/CeLa/Al. The electron-rich Pd showed Rh-like catalytic properties which exhibited good activity for the reduction of NO. NO-TPD results showed that the addition of CeO2 and/or La2O3 increased NO adsorption on surface, and promoted the conversion of NO.

Effect of Lanthanum on Methanol Fuel Exhaust Deep Oxidation over Palladium Catalyst

The performance of deep oxidation of methanol on supported Pd catalyst was exami ned by a chromatograph-micro-reactor. The results show that the add ition of La into γ-Al 2O 3 support can affect greatly the performance of t he Pd catalyst. In the absence of CO, La can decrease the content of oxygen-c ontaining intermediate, although La can not lower the light-off temperature of methanol oxidation. In the presence of CO, La can lower the light-off tem perature, decrease the amount of CO adsorption, and weaken evidently 'CO inhibi tion' to the oxidation of methanol. By XPS technique, it is shown that La modi fies the electronic structure of Pd, which attributes to the modifications of th e catalytic performance.

In-Situ FTIR Study on Effect of Lathanum on Oxidation Mechanism of Methanol Automobile Exhaust on Supported Palladium Catalyst

The performance of severe oxidation of methanol on 0.1%Pd supported on alumina was studied by a combined device of chromatograph-micro reactor. The results show that the addition of La into γ-Al 2O 3 as support can affect the performance of Pd catalyst greatly. By using Pd catalyst containing La in methanol oxidation, though, the ignition temperature is not lower than that by using Pd catalyst, the presence of La does suppress the formation of oxygenic intermediates. The results by in-situ FTIR show that the presence of La in the support affects the adsorbed species and hence the mechanism of severe oxidation of methanol on Pd catalyst.

Novel Oxygen Storage Components Promoted Palladium Catalysts for Emission Control in Natural Gas Powered Engines

A three-way catalyst comprised novel oxygen storage components for emission control in natural gas powered engines was prepared. The addition of novel oxygen storage components to the Pd/γ-Al2O3 catalysts resulted in improved activities of the fresh and aged catalyst by lowering the light-off temperature for methane in natural gas engines exhaust.

Nation-Teflon bimembrane-supported palladium catalysts for Suzuki coupling reactions

Nation-Teflon bimembrane was used as an efficient support for the preparation and application of heterogeneous palladium catalysts. The supported palladium catalysts exhibit high activity and stability in the Suzuki cross-coupling of aryl bromides with arylboronic acids to afford the corresponding biaryls in good to excellent yields, and can be readily recovered and reused several times without significant loss of activity.

Nitric Oxide Reduction Performance of Automotive Palladium Catalysts

Activity of three-way palladium catalyst was examined by means of a pulse-flam-microreactor. The effects of cerium on the catalytic properties of gamma-alumina-supported palladium for the reduction of nitric oxide were studied with X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR). The reduction of nitric oxide on palladium catalysts is inhibited significantly by hydrocarbon. However, the reduction of nitric oxide was improved by the addition of cerium to the catalysts. The XPS and TPR studies showed that the presence of cerium provided, palladium oxide in a hard-reduced state and suppressed the chemisorption of hydrocarbons on the palladium oxide. Additionally,cerium could increase surface specific oxygen storage capacity and decrease the apparent activation energy for the rea;ltion CO+NO-->CO2-+-1/2 N-2. So a high conversion of NOx reduction could shift to higher A/F ratio.

Preparation of microcapsule-supported palladium catalyst using SPG (Shirasu Porous Glass)emulsification technique

A new method for the preparation of microcapsule-supported palladium catalyst was described.The highly monodisperse crosslinked polystyrene microcapsules containing phosphine ligand were synthesized by the self-assembling of phase separated polymer （SaPSeP） method using diphenyl（4-vinylphenyl） phosphine and divinylbenzene as a monomer and crosslinking agent,respectively, and 2,2＇-azobisisobutyronitrile（AIBN） as an initiator within the droplets of oil-in-water（O/W） emulsions,which were prepared by using the Shirasu Porous Glass（SPG） membrane emulsification technique.The prepared microcapsule-supported palladium catalyst exhibited high catalytic activity for Heck reaction and can be reused several times without loss of activity.

CARBONYLATION OF ALLYL HALIDES CATALYZED BY POLY(N-VINYL-2-PYRROLIDONE) ANCHORED PALLADIUM CATALYST UNDER ATMOSPHERIC PRESSURE

Carbonylation of allyl halides catalyzed by poly(N-vinyl-2-pyrro- lidone) anchored palladium catalyst affords β,r-butonic acid under atmo- spheric pressure and at room temperature.The activity and efficiency of the catalyst are much higher than those of the reported catalysts for this reaction.

Research Progress of Palladium Catalysts for Methane Combustion

Recent research progress and development of the palladium catalysts for methane combustion are described in this study.The influence of active species,precursor,solvent,preparation methodologies,support and dopant on the catalytic activity and thermal stability of the palladium catalysts was discussed.Results of deactivation and poisoning of palladium catalysts were analyzed.Furthermore,possible kinetic models and reaction mechanism were indicated for Pd catalysts.

Synthesis of the Palladium Catalyst with the Supercritical СO2-Impregnation Method Realized in the Static Mode

Results of research of supercritical fluid CO2-impregnation process (the static mode) within a problem of synthesis of the palladium catalyst are given. The kinetics of process is characterized in the pressure range from 15.0 to 35.0 MPa on temperatures 308.15?K, 313.15?K, 318.15?K, 323.15?K, 328.15?K and 333.15?K. Results of surface assessment and activity measurements of the catalyst samples synthesized by supercritical СO2-impregnation of aluminum oxide suggest competitiveness of the discussed approach in comparison to traditional methods.

Use of Ionic Liquids in Recycle of Palladium Catalysts for Synthesis of Polyketone

Room temperature ionic liquids as solvents for palladium-catalyzed copolymerization of carbon monoxide and styrene were prepared by reaction of aqueous lead tetrafluoroborate with correspond-ing chloride or bromide salts. The recyclability of palladium composite catalyst in various ionic liquids was investigated. [Pd(bipy)2][BF4]2 showed a lower catalytic activity than [Pd(bipy)2][PF6]2 in similar conditions, although the catalytic activity of each composite catalyst in ionic liquids still existed after 4 successive recycles. It was shown the catalytic activity of palladium composite catalyst was higher than that of the catalyst formed in situ from palladium acetate, 2,2′-bipyridyl, and HA (A=PF6-, BF4-) in ionic liquids. The effects of volume of ionic liquids, reaction time, and the dosage of benzoquinone on the copolymerization were also studied.

Enantioselective Alternating Copolymerization of Propylene with Carbon Monoxide Using Cationic Palladium-Chiral Diphosphine Catalyst

Enantioselective alternating copolymerization of carbon monoxide with propylene was carried out using palladium catalyst modified by 1,4-3,6-dianhydro-2,5-dideoxy-2,5-bis (diphenylphosphino)-L-iditol (DDPPI). The chiral diphosphine was proved to be effective at enantioselective copolymerization. Optical rotation, elemental analysis, H-1, C-13-NMR and IR spectra showed that the copolymer was optically active, isotactic, alternating poly(1,4-ketone) structure.

MODIFICATION OF PALLADIUM METALLIC CATALYST WITH POLYMER-ANCHORED THIOETHER LIGANDS

A well-dispersed metallic palladium catalyst modified by polymer-anchored thioether ligands was used for the hydrogenation of cyclopentadiene to cyclopentene with high activity and selectivity in ambient condition. The evidences to show the modification of catalytic properties by polymer anchored ligands were given.

Incorporating Sulfur Atoms into Palladium Catalysts by Reactive Metal–Support Interaction for Selective Hydrogenation

Developing highly active and selective catalysts for the hydrogenation of nitroarenes,an environmentally benign process to produce industrially important aniline intermediates,is highly desirable but very challenging.Pd catalysts are generally recognized as active but nonselective catalysts for this important reaction.Here,we report an effective strategy to greatly improve the selectivity of Pd catalysts based on the reactive metal–support interaction.

Preparation and application of SBA-15-supported palladium catalyst for Heck reaction in supercritical carbon dioxide

为 SBA-15-supported 钯催化剂为的准备的一个新方法哎呀在 supercritical 二氧化碳的反应被介绍。最新形成的 SBA-15-supported 钯催化剂(Ph-SBA-15-PPh3-Pd ) 与甲基 acrylate 为 4-nitrobromobenzene 的 Heck 反应展出了高催化的活动。没有活动的损失，催化剂能若干次被再使用。

Influence of chelate ring size on the properties of phosphine-sulfonate palladium catalysts

Phosphine-sulfonate based palladium is one of the most extensively studied catalyst systems in olefin polymerization.This type of catalyst features six-membered chelate ring size,and can enable the copolymerizations of ethylene with a wide variety of polar monomers.In this contribution,we decide to investigate the influence of chelate ring size on the properties of phosphinesulfonate palladium catalysts.As such,a series of phosphine-sulfonate ligands and the corresponding seven-membered ring Pd(II)complexes[κ~2-(P,O)-2-(CH_2-PR_1R_2)-4-methylphenyl-sulfonato]Pd(Me)(DMSO)(Pd1,R_1=R_2=Cy,Pd2,R_1=R_2=o-Me O-C_6H_4;Pd3,R_1=Ph,R_2=2-[2,6-(Me O)_2C_6H_3]C_6H_4;DMSO=dimethyl sulfoxide)were designed,prepared and characterized.These palladium complexes are moderately active when they were applied in ethylene polymerization and copolymerizations with methyl acrylate and butyl vinyl ether.However,their properties are greatly reduced from those of the classic six-membered ring phosphine-sulfonate palladium complex Pd2′.The experimental results indicate that the bigger chelate ring size can increase the ligand flexibility and damage the catalytic properties for the phosphine-sulfonate type palladium catalysts.

Chitosan-immobilized Palladium Complex: a Green and Highly Active Heterogeneous Catalyst for Heck Reaction

A green heterogeneous catalyst for Heck reaction-chitosan-immobilized palladium complex was prepared. The catalyst exhibits high activity and stereoselectivity under the moderate reaction conditions. The catalyst can be separated easily from the reaction mixture and reused after washing. Under the suitable reaction conditions, the cross-coupling of iodobenzene (ArI) with acrylic acid (AA) or acrylate can be achieved 93.3% or 99% yield of trans-cinnamic acid or trans-cinnamic ester.

Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres supported palladium complex as an efficient catalyst for Heck reaction

Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres synthesized by suspension polymerization were used as supports for palladium catalyst.The results showed the novel magnetic catalyst can promote Heck reaction of aryl halides with acrylic acid efficiently without an inert atmosphere.In addition,the novel catalyst can be conveniently recovered by applying an external magnet and reused at least five times without significant loss of its activity.