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.

Preparation of palladium-based catalyst by plasma-assisted atomic layer deposition and its applications in CO_(2) hydrogenation reduction

Supported Pd catalyst is an important noble metal material in recent years due to its high catalytic performance in CO_(2)hydrogenation.A fluidized-bed plasma assisted atomic layer deposition(FP-ALD) process is reported to fabricate Pd nanoparticle catalyst over γ-Al_(2)O_(3)or Fe_(2)O_(3)/γ-Al_(2)O_(3)support,using palladium hexafluoroacetylacetonate as the Pd precursor and H_(2)plasma as counter-reactant.Scanning transmission electron microscopy exhibits that highdensity Pd nanoparticles are uniformly dispersed over Fe_(2)O_(3)/γ-Al_(2)O_(3)support with an average diameter of 4.4 nm.The deposited Pd-Fe_(2)O_(3)/γ-Al_(2)O_(3)shows excellent catalytic performance for CO_(2)hydrogenation in a dielectric barrier discharge reactor.Under a typical condition of H_(2)to CO_(2)ratio of 4 in the feed gas,the discharge power of 19.6 W,and gas hourly space velocity of10000 h^(-1),the conversion of CO_(2)is as high as 16.3% with CH_(3)OH and CH4selectivities of 26.5%and 3.9%,respectively.

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.

Palladium nanoparticles in cross-linked polyaniline as highly efficient catalysts for Suzuki-Miyaura reactions

Palladium nanoparticles supported on cross-linked polyaniline with bulky phosphorus ligands were developed.These catalysts showed high efficiency in the Suzuki-Miyaura reaction of aryl chlorides and bromides with phenylboronic acids.Aryl chlorides and bromides with functional groups,such as CN,MeO,CHO,MeCO and NO_2,were converted to the corresponding biphenyls in high yields with catalyst loading.Additionally,the catalysts combined high activity with good reusability;they could be used at least five times for the Suzuki-Miyaura coupling reaction.

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.

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.

Methane combustion over palladium catalyst within the confined space of MFI zeolite

Isolated cationic Pd species encapsulated in MFI zeolite,i.e.,Pd@MFI,have been successfully prepared via in situ hydrothermal route followed by oxidative treatment.The as-prepared Pd@MFI samples are investigated as promising catalysts in the reaction of methane combustion.Typically,Pd@H-ZSM-5 shows remarkable activity in methane catalytic combustion with a low apparent activation energy value of 70.7 kj/mol as well as good catalytic stability even in excess water vapor.Detailed characterization results demonstrate the strong interaction between Pd sites and zeolite framework in Pd@ZSM-5 and the efficient stabilization of isolated Pd sites by zeolite thereof.Spectroscopy analyses reveal that the presence of BrΦnsted acid sites is beneficial to methane adsorption and its subsequent activation on adjacent Pd sites,constructing cooperation between Bronsted acid sites and Pd sites within the confined space of MFI zeolite toward high-efficiency methane catalytic combustion.The reaction mechanism of methane combustion catalyzed by Pd@H-ZSM-5 model catalyst is finally discussed.

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.

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.

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.

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.

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.

Aerobic oxidation assisted by ligand-free palladium catalysts

Aerobic oxidation of electron-rich benzylic and phenyl allylic alcohols was achieved with high yields with only 0.1 mol.% of Pd(OAc)2 catalyst in the absence of any ligand. This procedure was expected to be valuable for realistic industrial-scale applications from both economic as well as environmental points of view.

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.

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.

POLYMERIZATION OF A NEW SUBSTITUTED ACETYLENE BEARING A FURAN RING WITH PALLADIUM ACETYLIDE CATALYSTS

A substituted polyacetylene bearing a furan ring, poly(2-propynyl 2-furoate) (PPF), was synthesized for the first time with palladium acetylide complex catalysts in CHCl3 at 60°C to give a soluble and stable polymer with a yield of ca. 75%. Some features for polymerization of 2-propynyl 2-furoate are described and discussed. The resulting polymer was characterized by IR, GPC and 1H-NMR analysis.

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.

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.

Ceria-Modified Clay Supported Palladium Catalysts for Complete Oxidation of Volatile Organic Compounds

Ceria- and alumina-pillared interlayered clays were synthesized in the presence of PEO surfactant by using laponite clay as raw material.And the synthesized pillared clays were used as supports to load palladium catalysts for complete oxidation of benzene.Nitrogen adsorption/desorption experiments reveal that the pillared clays have higher tests show that ceria pillar exhibited promoting effect on the activity of the palladium catalysts, and ceria-pillared clay supported palladium catalyst catalyzed the complete oxidation of benzene at less than 250 ℃.The calcination temperature affects the activity of the catalysts significantly, and it is found that the optimal calcination temperature are 600 and 400 ℃ for ceria- and alumina-pillared clay supported palladium catalysts, respectively.