Pd—Au／C催化剂中钯和金的测定

建立了一种用分光光度法测定Pd—Au／C催化剂的钯含量和金含量的方法,该方法简便、快捷、准确,相对标准偏差小于2．0％。     

醋酸乙烯Pd—Au／SiO2催化剂的老化研究

比较了乙烯气相法合成醋酸乙烯Pd—Au／SiO2催化剂不同反应时期的结构变化情况，指出催化剂的失活主要是由于稠环有机物的不可逆吸附而不是活性组分Pd晶粒增长造成的，由此提出了催化剂的多种老化方法促使Pd晶粒增长以降低初活性，从而达到缩短催化剂驯化期的目的。以XRD作为主要表征手段，研究了制备过程中各种气氛下的高温老化方法对Pd—Au／SiO2体系的影响。结果表明，高温焙烧不影响Pd，Au的合金结构，但会促使金属微粒的凝聚生长，从而降低了催化剂初活性，缩短了工业运行的驯化期，尤其是醋酸气氛老化的催化剂具有更好的活性稳定性和更高的反应选择性。     

聚吡咯碳载PdAu催化剂对甲酸的电催化氧化

通过低温氧化法制备了聚吡咯碳(PPyC),并以PPyC为载体制备了纳米Pd催化剂(Pd/PPyC)及PdAu催化剂(PdAu/PPyC),研究发现不同比例的Pd∶Au催化剂PdAu/PPyC对甲酸的甲催化活性不同。通过计算发现,催化剂的电化学比表面积催化剂中加入少量Au能够提高催化剂中活性粒子Pd的分散度,其中Pd∶Au为4∶1时电化学比表面最大,且对甲酸有最高的电催化氧化活性。     

微波辅助法制备Pd／C和Pd-Co／C催化剂及其氧还原催化活性研究

为了减少有机溶剂的使用量,使制备方法更加环境友好,文章研究了有机溶剂量对微波反应制备Pd／C系列催化剂的影响,并采用XRD、TEM和电化学测试等方法对催化剂结构和电化学性能进行了表征和评价。研究表明：当有机溶剂使用量降到5mL时,该催化剂依然能保持较高的催化活性。在此基础上,文章还对一系列不同组成的Pd-Co／C合金催化剂进行了研究．发现活性组分粒径约为3．5nm时,Pd2Co／C催化剂具有最佳的氧还原电催化活性。     

Au@Pd催化剂的制备及其催化甲醇氧化反应的研究

通过常温液相法制备了核壳结构Au@Pd/C催化剂和AuPd合金催化剂。利用XRD、TEM和电化学测试等手段对催化剂的组成、结构和催化甲醇氧化性能进行了表征。结果表明,2种催化剂的粒径均为20 nm左右;由于Au核的存在,Au@Pd/C催化剂有效增加了Pd的活性面积,提高了催化甲醇的氧化活性和稳定性;降低了Pd的还原电位,提高了其抗CO中毒的能力。     

水合肼还原对硝基乙酰苯胺的研究

本文以Pd／C为催化剂，水合肼为还原剂由p-硝基乙酰苯胺还原制备p-氨基乙酰苯胺。通过正交实验确定p-硝基乙酰苯胺的水合肼还原反应中催化剂用量是最重要的影响因素。当n(p-NO2C6H4NHCOCH3)：n(N2H4H2O))=1：1.8、0．8％Pd／C催化剂8．5g／mol p-硝基乙酰苯胺时．80℃，反应3小时，p-硝基乙酰苯胺的转化率达100％。用质谱及红外光谱对产物进行了表征。在液相色谱跟踪下对还原反应的历程进行了初步考察。     

用Pd/C催化剂加氢合成3,4-二甲基苯基-D-核糖胺

采用浸渍法制备Pd／C催化剂，用于3，4-二甲基苯基-D-核糖胺的合成，研究了活性炭种类、还原方法和反应条件对催化剂加氢性能的影响。结果表明，Pd／C催化剂是该缩合还原反应的有效催化剂，在低压下的单程收率可达60％以上。     

β—取代丁烯酮的双键选择加氢

研究了高选择性5％Pd／C催化剂上β-取代丁烯酮选择加氢制β-取代丁酮，转化率达100％．选择性大于97.5％．对异丙叉丙酮催化剂重复使用8次，平均转化率99．4％，平均选择性99．8％。     

Ni—Pd／C双金属催化剂羰基化反应合成丙酸的研究

考察了Ni—Pd／C双金属催化剂上催化乙醇气相羰基化合成丙酸的反应。实验结果表明,负载活性炭Ni—Pd双金属催化剂相比普通非贵金属催化剂具有很高的活性及选择性,最佳反应工艺条件为,在少量碘代乙烷存在下,压力0．15MPa,温度220℃,n（CO）：n（C2H5OH）=2．0：1,乙醇液体空速1．5h^-1此时乙醇羰基化反应产物中丙酸及丙酸酯的选择性可高达96．7％,通过GC—MS对反应产物分析,分析了反应过程的机理。     

Ullmann偶联反应催化剂研究进展

Ullmann偶联反应是典型的碳碳键偶联反应,反应合成的联苯类化合物是重要有机化工原料,应用前景广阔。初期采用均相Pd催化剂,不能重复利用,工业化生产受到限制。改用多相Pd催化剂催化反应,需要添加剂导致产物分离困难。多相Au催化剂适用性受到限制,反应底物局限于碘代芳烃,双金属催化剂在催化活性与选择性方面均有较好的优势。综述Ullmann-type偶联反应中均相Pd催化体系、多相Pd催化体系、多相Au催化体系以及多相双金属催化体系催化剂的研究进展,阐述反应机理,并对Ullmann偶联反应研究进行展望。     

Catalytic Oxidation of Polyethylene Glycol Dodecyl Ether to Corresponding Carboxylic Acid by Gold, Palladium (Mono and Bimetallic) Nanoparticles Supported on Carbon

Mono and bimetallic catalysts based on Au and Pd nanoparticles were synthesized by sol immobilization method. The catalytic oxidation of polyethylene glycol dodecyl ether was performed using as-synthesized supported catalyst. The use of water as solvent and dioxygen as oxidant makes the reaction interesting from both an economic and environmental point of view. For 100 min, the conversion of polyethylene glycol dodecyl ether using Au–Pd/C bimetallic catalyst was 38%, showing an increase of 9% for Au/C and 15% for Pd/C respectively indicating that a synergetic effect exists between Au and Pd. For the Au–Pd/C catalyst, adding Au after the prior addition and reduction of Pd metal can form the most active catalyst.     

Selective Oxidation of Benzyl-Alcohol over Biomass-Supported Au/Pd Bioinorganic Catalysts

We report a novel biochemical method based on the sacrificial hydrogen strategy to synthesise bimetallic Au/Pd nanoparticles supported on bacterial cells. The synergistic effect of Au/Pd over monometallic preparations was demonstrated in the oxidation of benzyl alcohol. The bioinorganic catalysts outperformed a commercial Pd catalyst (5% Pd/C) showing no deactivation and high selectivity towards benzaldehyde.     

Selective aerobic oxidation of alcohols over Au–Pd/sodium titanate nanotubes

The catalytic application of Au–Pd nanoparticles supported on sodium titanate nanotubes (NaTNTs) for liquid-phase aerobic oxidation of alcohols is reported, for the first time. This reaction occurs at 80–120 °C, 1 atm and solvent-/alkali-free conditions yielding the corresponding carbonyls in high selectivity. This catalyst was reusable and found to be more active/selective than the corresponding monometallic Au and Pd catalysts and Au–Pd/TiO₂. Higher dispersion, smaller particle size and higher amount of electron density at gold are the causes for the superior activity of Au–Pd/NaTNT catalyst.     

用于合成4-(反-4′-正丙基环己基)环己酮催化剂的研究

环己酮衍生物作为一种重要的液晶中间体,其制备方法尤其是催化加氢合成法的研究受到关注。以质量分数55%HNO₃处理的工业椰壳活性炭为载体,采用等体积浸渍与沉积-沉淀结合的方法制备0.9%Au-5%Pd/C-IM-DP催化剂,并应用于选择性加氢制备4-(反-4′-正丙基环己基)环己酮的反应。以环己烷作为溶剂,在反应温度150 ℃和反应压力0.8 MPa条件下反应2 h,原料转化率为98.7%,目标产物选择性达91.2%。相比于单金属5%Pd/C催化剂,0.9%Au-5%Pd/C-IM-DP催化剂具有较高的活性和选择性。通过XRD和TEM等对催化剂组成和形貌进行表征分析,结果表明,Au和Pd均以单金属颗粒形式存在,而Pd和Au之间的氢溢流作用可能是催化剂具有优异性能的原因。     

A Comparative Study of Partial Oxidation of Methanol over Zinc Oxide Supported Metallic Catalysts

Au/ZnO, Pd/ZnO and Au–Pd/ZnO catalysts were prepared by PVP-stabilized reduction method by C₂H₅OH. The catalysts have been used successfully for hydrogen production by partial oxidation of methanol (POM). The influence of Au, Pd and Au–Pd on the performance of supported catalysts for POM has been investigated. The prepared samples were characterized by ICP, XRD, BET, TPR and TPD. The results show that the Au–Pd/ZnO catalyst are more active and exhibit higher hydrogen selectively compared to the Pd/ZnO and Au/ZnO catalyst, the methanol conversion of 99.5% and hydrogen selectivity of 65.6% were obtained at 573 K. The enhanced activity and stability of the bimetallic Au–Pd/ZnO catalyst has been explained in terms of the higher dispersion and basic density, smaller particles of gold and synergetic effect between gold and palladium.     

High Electrochemical Performance and Stability of Co-Deposited Pd–Au on Phase-Pure Tungsten Carbide for Hydrogen Oxidation

Co-deposited Pd and Au nanoparticles were loaded on phase-pure tungsten mono-carbide (WC) prepared by a polymer-induced carburization method. Among the electrocatalysts, Pd₃Au/WC displayed an excellent electrochemical activity for the hydrogen oxidation reaction comparable to the state-of-the-art Pt/C catalyst both in half-cell tests and single cell tests under proton exchange membrane fuel cell (PEMFC) conditions. This unique and strong synergistic effect was not observed on the carbon support, and thus the crucial role of WC was demonstrated as a strongly interacting support as well as an active component of the electrocatalyst. Dissolution of Pd observed on the carbon support was suppressed in this Pd₃Au/WC electrocatalyst, which showed good stability in a continuous operation for 3,000?min. Thus the proposed electrocatalyst could be a potential alternative anode catalyst of lower cost for PEMFC replacing Pt/C.     

含氮中孔碳负载的Au-Pd双金属催化剂在甲酸分解制氢中的催化性能

以SBA-15作为硬模板剂,吡咯作为碳源和氮源,制得的含氮中孔碳作为载体,采用吸附还原法分别制备了单Pd和Au-Pd双金属催化剂,并考察其在甲酸分解制氢反应中的催化性能。结果发现,Au-Pd/N-C比Au-Pd/C催化剂具有更高的甲酸分解活性,这可能是因为N的亲核作用促进了甲酸中H质子的脱除。由于Au-Pd之间的强相互作用,使Au的加入显著提高了Pd/N-C催化剂甲酸分解活性及其抗CO中毒能力,在50℃条件下,分解1 mol·L-1的甲酸初始转换频率(TOF)达到2 221 h-1。     

PdAg、PdAu合金纳米晶的制备及其催化性能研究

采用硼氢化钠一步还原法,首先得到PdAg和PdAu双金属合金纳米颗粒.利用XRD、TEM以及紫外可见光光谱技术对其进行了表征分析.结果表明,PdAg和PdAu两种合金都具有纳米颗粒分散均匀且颗粒尺寸小等优点.随后采用胶体沉积法将两种合金均匀地负载到Al2O3上,成功获得PdAg/Al2O3和PdAu/Al2O3两种金属纳米催化剂.在邻氯硝基苯加氢反应中,与Pd/Al2O3纳米催化剂相比,PdAg/Al2O3催化剂显示出95.5％的选择性,而PdAu/AI2O3催化剂的选择性高达98.7％,这可能归因于Pd与Ag或Au金属间的协同效应.     

The Formation of PdCx over Pd-Based Catalysts in Vapor-Phase Vinyl Acetate Synthesis: Does a Pd–Au Alloy Catalyst Resist Carbide Formation?

The formation of Pd carbide (PdC _x ) during the synthesis of vinyl acetate (VA) was investigated over Pd/SiO₂ catalysts with two different Pd particle sizes, as well as over a Pd–Au/SiO₂ mixed-metal catalyst. XRD data show that PdC _x was produced in the pure Pd catalysts after reaction based on the downshift of the Pd(111) and (200) XRD features. The smaller Pd particles showed greater resistance to the formation of PdC _x . The XRD and XPS data are consistent with formation of a PdC _x species at the surface of the Pd–Au catalyst, however, the primary contributor to the downshift of the Pd(111) feature subsequent to reaction in the mixed-metal catalyst is believed to arise from reaction-induced alloying of Au with Pd. The alloying of Au with Pd is apparently very effective in preventing PdC _x formation in Pd-based catalysts for VA synthesis.     

Solvent-free oxidation of benzyl alcohol using titania-supported gold–palladium catalysts: Effect of Au–Pd ratio on catalytic performance

The oxidation of benzyl alcohol with molecular oxygen under solvent-free conditions has been investigated using a range of titania-supported Au–Pd alloy catalysts to examine the effect of the Au–Pd ratio on the conversion and selectivity. The catalysts have been compared at high reaction temperature (160 °C) as well as at 100 °C, to determine the effect on selectivity since at lower reaction temperature the range of by-products that are formed are limited. Under these conditions the 2.5 wt.% Au–2.5 wt.% Pd/TiO₂ was found to be the most active catalyst, whereas the Au/TiO₂ catalyst demonstrated the highest selectivity to benzaldehyde. Toluene, formed via either a hydrogen transfer process or an oxygen transfer process, was observed as a major by-product under these forcing conditions.