Quasi-homogeneous hydrogenation with platinum and palladium nanoparticles stabilized by dendritic core-multishell architectures

Platinum and palladium nanoparticles, supported and stabilized by polymeric core-shell architectures, proved to be active catalysts for hydrogenation reactions. Here, two different reactions were used as probes to investigate the influence of the polymeric support: the hydrogenation of α-methyl styrene (AMS) to cumene and the partial hydrogenation of 1,5-cyclooctadiene (COD). We found that the stability of the nanoparticles and the rate of reaction are higher in the presence of a hydrophobic octadecyl shell within a three-shell polymer system. The kinetic study of AMS hydrogenation showed much higher activities for palladium nanoparticles than for platinum nanoparticles, and the obtained results (e.g., 35 kJ/mol for the activation energy) are of the same order of magnitude as reported earlier for palladium supported on alumina. A methanol/n-heptane biphasic mixture was tested for catalyst recycling and allowed for highly efficient catalyst separation with very low metal leaching.     

膦化聚2,6—二甲基1,4—苯醚负载钯催化剂的表征及其催化性能

报道了四种不同P/Pd摩尔比的膦化聚2,6-二甲基1,4-苯醚负载把催化剂的加氢和异构化性能;通过XPS、电镜和远红外对催化剂进行了表征;并考察了溶剂和温度对催化剂活性的影响.     

硝基芳烃氢化还原反应中高分子负载催化剂的双金属协同效应

制备了聚Ｎ－乙烯基－２－吡咯烷酮ＰＶＰ负载钯催化剂Ｐｄ／ＰＶＰ及各种双金属催化剂（１－ｍ）Ｐｄ－ｍＭ／ＰＶＰ，并用于硝基芳烃的加氢还原中，其中Ｐｄ／ＰＶＰ中加入Ｈ２ＰｔＣｌ６的效果最佳，碱的用量、溶剂和Ｐｄ、Ｐｔ的比例都对催化剂的活性有明显的影响，双金属催化剂０．８０Ｐｄ－０．２０Ｐｔ／ＰＶＰ在温和条件下能高活性，高选择性地催化硝基芳烃还原，得到相应的芳胺。     

On propene hydroformylation and hydrogenation over palladium

The complex kinetic influence of surface species of catalysts is discussed for propene hydrogenation and hydroformylation over sodium supported palladium and palladium catalyst. The reaction orders in CO demonstrate the involvement of CO in propene hydrogenation. Therefore, an additional pathway for hydrogenation with formation of a complex between CO and hydrogen, which further reacts with propene, is advanced.     

Thiophene Hydrogenation to Tetrahydrothiophene over Tungsten Sulfide Catalysts

Independent reactions of thiophene reduction to tetrahydrothiophene and thiophene hydrogenolysis to form hydrogen sulfide and C₄ hydrocarbons are shown to occur over supported tungsten sulfide catalysts and unsupported tungsten sulfide at an elevated temperature and a high pressure. The highest rate of tetrahydrothiophene formation over the supported catalysts is observed when alumina was used as a support, and the lowest reaction rate is found when silica gel was used as a support. Both catalysts are less active than unsupported tungsten disulfide. The rate of thiophene hydrogenation over tungsten disulfide increases with increasing thiophene concentration and hydrogen pressure and is inhibited by tetrahydrothiophene. The selectivity to tetrahydrothiophene is constant (70–90%) in the whole range up to high thiophene conversions. The high selectivity over tungsten sulfide catalysts is suggested to be due to the reaction pathway through thiophene protonation mediated with the surface SH groups and to the inhibition of hydrogenolysis.     

Comparing the hydrodesulfurization reaction of thiophene on γ-Al2O3 supported CoMo, NiMo and NiW sulfide catalysts

The thiophene hydrodesulfurization (HDS) reaction on γ-Al₂O₃ supported CoMo, NiMo and NiW sulfide catalysts was compared in order to gain insight into the promoter effect on direct desulfurization (DDS) and hydrogenation (HYD) pathways. Ni-promoted Mo (or W) sulfide catalysts favor the hydrogen transfer reactions relative to CoMo sulfide catalyst, which facilitates the direct route instead. This different performance and also the dependence of the apparent Arrhenius parameters with the catalyst formulation were attributed to the major participation of Mo (or W) edge for the Ni-containing catalysts and S edge for CoMo sulfide catalyst upon the thiophene-HDS reaction.     

负载(S)-脯氨酸手性固相催化剂制备和在不对称加氢反应中的应用

用亲水性、高比表面积、硅烷化硅小球担载钯,以（Ｓ）－脯氨酸为手性助剂、苯乙酮为反应底物,考察不对称加氢反应和不同有机碱助催化剂的影响。实验表明,当使用三辛胺助催化剂时,（Ｒ）－苯乙醇的对映异构体选择性可达１７．５％。将（Ｓ）－脯氨酸负载于亲水性、高比表面积、硅烷化硅小球担体表面,以Ｐｄ（ＯＡｃ）２为催经剂前体,制备负载型手性固相催化剂,初步考察了（Ｓ）－脯氨酸与中心金属钯的摩尔比、疏水性不同的有机     

Properties of Pd–Ag/C catalysts in the reaction of selective hydrogenation of acetylene

Samples of Pd/C and Pd–Ag/C, where C represents carbon nanofibers (CNFs), are synthesized by methane decomposition on a Ni–Cu–Fe/Al₂O₃ catalyst. The properties of Pd/CNF are studied in the reaction of selective hydrogenation of acetylene into ethylene. It is found that the activity of the catalyst in hydrogenation reaction increases, while selectivity decreases considerably when the palladium content rises. The obtained dependences are caused by the features of palladium’s interaction with the carbon support. At a low Pd content (up to 0.04 wt %) in the catalyst, the metal is inserted into the interlayer space of graphite and the catalytic activity is zero. It is established by EXAFS that the main share of palladium in catalysts of 0.05–0.1 wt % Pd/CNF constitutes the metal in the atomically dispersed state. The coordination environment of palladium atoms consists of carbon atoms. An increase in the palladium content in a Pd/CNF catalyst up to 0.3 wt % leads to the formation of highly dispersed (0.8–1 nm) Pd particles. The Pd/CNF samples where palladium is mainly in the atomically dispersed state exhibit the highest selectivity in the acetylene hydrogenation reaction. The addition of silver to a 0.1 wt % Pd/CNF catalyst initially probably leads to the formation of Pd–Ag clusters and then to alloyed Pd–Ag particles. An increase in the silver content in the catalyst above 0.3% causes the enlargement of the alloyed particles and the palladium atoms are blocked by a silver layer, which considerably decreases the catalytic activity in the selective hydrogenation of acetylene.     

The influence of the support on activity and selectivity of nickel sulfide catalysts in the decarbonylation of stearic acid to heptadecenes

The influence of the support nature on the performance of nickel sulfide catalyst in the decarbonylation of stearic acid to heptadecenes was investigated. The catalyst supported on silica demonstrated higher activity and selectivity in comparison with the catalyst on γ-Al₂O₃ used as a reference. The reaction schemes over these catalysts are nearly the same; however, the contributions from the side reactions of hydrogenation and oligomerization are reasonably different. Introduction of the products of decarbonylation (CO and water vapor) decreases the stearic acid conversion; and in the case of the catalyst supported on silica, the addition of CO strongly reduces the rate of hydrogenation of heptadecenes. The reasons for the observed differences were discussed. It was suggested that the dispersion of the nickel component as well as the nature of support acidity played a significant role.     

Terpolymerization of carbon monoxide, ethylene and styrene in the presence of supported palladium catalyst

Terpolymers of carbon monoxide with ethylene and styrene are synthesized in the presence of supported palladium catalyst in toluene and heptane medium for the first time. The terpolymerization rate exceeds the rate of carbon monoxide and ethylene copolymerization. The maximum terpolymer yield amounts 7.9 g per g of supported catalyst per hour or 321 g per g of palladium per hour. The influence of reaction temperature, pressure, 1.4-benzoquinone amount and co-monomers mole ratio on the yield and the composition of terpolymer have been studied. The NMR ¹³C data obtained testify to a distribution of ethylene and styrene units in terpolymer with the predominance of short blocks at equal contents of comonomer units.     

Preparation,structural characterization of a novel egg-shell palladium sulfide catalyst and its application in selective reductive alkylation reaction

A novel egg-shell Pd-S catalyst with palladium metal as the core and a membrane of palladium sulfide as the surface has been prepared by sulphidizing Pd/C with H₂S.This catalyst is effective for the reductive alkylation of p-amino diphenylamine（PADPA） and methylisobutyl ketone（MIBK） to afford N-（1,3-dimethylbutyl）-N′-phenyl-p-phenylenedianine（DBPPD） with conversion up to 99.42%and selectivity to 97.46%.Comparing with the other common palladium sulfide catalysts,the membrane of palladium sulfide on the surface and the core of palladium metal cause the Pd on the surface of the new catalyst in a lower sulfur coordination, which improves its activity.Our result indicates that this new egg-shell Pd-S/C is an efficient hydrogenation catalyst.     

Ni-Mo/Al_2O_3催化剂上硫转移反应的研究

制备了以γ-Al2O3为载体的Ni-Mo催化剂,并用于FCC汽油的加氢硫转移反应。对Ni-Mo/Al2O3催化剂上的硫转移反应机理进行了研究,考察了不同反应条件对硫转移反应的影响。实验结果表明,硫醇与烯烃的反应在催化剂表面的加氢活性位上进行,小分子的硫醇发生加氢脱硫,生成吸附态H2S,吸附态的H2S与烯烃反应,生成大分子硫醇和硫醚;另外小分子硫醇还可直接与烯烃发生反应,生成硫醚。提高反应温度、压力、氢油比或降低空速,均可提高催化剂的硫转移反应活性,轻质硫转化率得到明显提高,且单烯选择性还能维持在98%左右。     

Kinetic Study of Catalytic Hydrogenation of Thiophene on a Palladium Sulfide Catalyst

The kinetics of thiophene hydrogenation on a palladium sulfide catalyst is studied at high hydrogen pressures. The reaction mainly occurs via the consecutive scheme: the reaction of thiophene with hydrogen results in the formation of tetrahydrothiophene, which partially decomposes under the action of hydrogen to yield butane and hydrogen sulfide. A kinetic model describing the reaction rates and the selectivity to tetrahydrothiophene at 0.2–3.0 MPa and 493–533 K is proposed. The rate constants and activation energies are determined. The effect of temperature and pressure on the maximal yield of tetrahydrothiophene is examined.     

含氨基酸侧链的有机硅高分子催化剂 Ⅵ.聚γ-(赖氨酸基)丙基硅氧烷钯催化剂的合成及加氢活性

合成了聚γ-(顿氨酸基)丙基硅氧烷钯催化剂当N/Pd摩尔比为3.4时,这种催化剂在常温常压下对丙烯腈的加氢活性高达3057·6mL H_2/min·mmolPd;对环戊二烯的氢化反应是分两步进行的。溶剂对催化剂的活性有明显影响。     

Effect of support on activity of palladium catalysts in nitrobenzene hydrogenation

The effect of two types of catalysts on the activity of the catalytic hydrogenation of nitrobenzene was studied. Catalysts were prepared by the surface deposition of palladium hydroxide with a simultaneous reduction with formaldehyde in a basic environment and were characterised by X-ray powder diffraction, transmission electron microscopy, adsorption-desorption, and catalytic tests — hydrogenation of nitrobenzene in methanol. The influence of the supports’ (activated carbon and a mixture of activated carbon and multi-walled carbon nanotubes) surface area is discussed. Despite having a size comparable (4–5 nm) to crystallites of metallic palladium, the catalyst prepared on a mixture of activated carbon and nanotubes (Pd/C/CNT) was significantly less active than the catalyst prepared on pure activated carbon (Pd/C); the rate of this reaction was approximately 30 % lower than the initial reaction rate. This feature could be attributed to the lower specific surface area of the Pd/C/CNT (531 m² g^?1) in comparison with the Pd/C (692 m² g^?1).     

Selective conversion of furfuryl alcohol to 2-methylfuran over nanosilica supported Au:Pd bimetallic catalysts at room temperature

Using gold and palladium supported catalysts, the selective hydrogenation of furfuryl alcohol into 2-methylfuran at 25 °C was examined. The use of 2-methylfuran has become applicable in the perfumery and personalised care product industry, and it has been shown that there are two conditions under which Au:Pd/SiO₂ catalysts are successful for selectivity to 2-methylfuran at 25 °C and (1 bar, H₂). Moreover, this study has shed light on the effectiveness of several reaction conditions (supports and catalyst amount).     

Morphological and chemical influences on alumina-supported palladium catalysts active for the gas phase hydrogenation of crotonaldehyde

A series of five alumina-supported palladium catalysts have previously been prepared and characterised by a combination of CO chemisorption and infrared spectroscopy. The reactive attributes of these catalysts are examined using the hydrogenation of crotonaldehyde as a test reaction, using a modified infrared gas cell as a batch reactor. Periodic scanning of the infrared spectrum of the gaseous phase present over the Pd/Al(2)O(3) catalysts was used to construct reaction profiles. Four of the catalysts were able to facilitate a 2-stage hydrogenation process (crotonaldehyde → butanal → butanol), whilst one catalyst was totally selective for the first stage hydrogenation process (crotonaldehyde → butanal). Rate coefficients for the first and second stage hydrogenation processes are normalised to the number of surface palladium atoms for the particular catalyst. Correlation of these kinetic parameters as a function of mean particle size indicates the first stage process to be structure insensitive, whilst the second stage hydrogenation is structure sensitive. Chlorine residues associated with the preparative process of one of the catalysts is seen to selectively poison the second stage hydrogenation process for that catalyst. Structure/activity relationships are considered to explain the observed trends.     

Formation and the nature of activity of Ziegler systems based on palladium β-diketonate complexes in hydrogenation catalysis

The catalytic properties and nature of Ziegler-type Pd(Acac)₂ and Pd(Acac)₂PPh₃ based catalysts are studied in the hydrogenation of unsaturated compounds. The causes of an extremum appearing in the dependence of the specific activity of the catalyst in styrene and phenylacetylene hydrogenation on the proportions of the starting components are considered. The increase in the specific activity of the Pd(Acac)₂ + AlEt₃ catalytic system in hydrogenation as a function of the Al/Pd ratio arises from an increase in the degree of dispersion of the microheterogeneous system, an increase in the fraction of reduced palladium, and changes in the nature of the ligand shell. The inhibiting effect is caused by triethylaluminum adsorption on palladium nanoparticles. Palladium nanoparticle models are suggested.     

Perfluorinated membranes as catalyst supports

The perfluorinated polymer Nafion and porous PTFE/Nafion composite membranes have been employed as supports for nickel complexes or for platinum and palladium metal particles. The resultant materials have been employed as catalysts in various olefin conversion processes. Supported platinum and palladium metal systems were evaluated as catalysts for the hydrogenation of cyclohexene. Rates of reaction are better than those of commercially available catalysts; turnover numbers in excess of 6000 have been obtained with no poisoning apparent. Catalysts may be regenerated many times. The reduction rate approaches a limit at high pressures of hydrogen and has an activation energy of 13 kJ mol^?1 in neat cyclohexene. Nafion was employed as a strong acid cocatalyst to activate and then support a nickel complex catalyst. The resultant catalyst was active for double-bond-shift isomerization.     

SBA-15负载氧化铁催化剂上乙酸选择加氢制乙醛

制备了一系列SBA-15负载α-Fe₂O₃催化剂.研究了负载量、预还原温度和反应温度对乙酸选择加氢制乙醛反应的活性和选择性的影响.负载催化剂上乙醛的最高产率达到42.7%,比纯α-Fe₂O₃催化剂的32.2%高.催化剂表面Fe₃O₄和Fe⁰共存对提高反应性能有利.该反应有可能遵循Mars-vanKrevelen机理.