Catalytic dechlorination of aromatic chloride with supported palladium catalysts in alkaline 2-propanol: influence of hydrocarbon solvents

Summary Catalytic dechlorination of p-chloroanisole (p-chloromethoxybenzene) was carried out in a solution of NaOH in 2-propanol in the presence of Pd/Al₂O₃ or Pd/C at 40°C. When aromatic hydrocarbons such as toluene or benzene were added to the solution, the dechlorination rates were strongly suppressed. However, aliphatic hydrocarbons such as n-hexane or cyclohexane hardly affected the dechlorination rates.     

Dehydrogenation of 2-propanol with suspended noble metal catalysts: activity enhancement by the addition of sodium hydoxide

Catalytic dehydrogenation of 2-propanol was carried out in the presence of suspended Rh/C, Ru/C, Pd/C, Pt/C or Pt/Al₂O₃ under boiling and refluxing conditions. Adding NaOH to the 2-propanol enhanced the H₂ evolution rate by a factor of 1.06-52.9, depending on the catalyst. The activity enhancements observed with KOH, Mg(OH)₂, Ca(OH)₂ and NaHCO₃ were lower than those with NaOH. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pd/C promoted by Au for 2-propanol electrooxidation in alkaline media

Pd/C catalysts promoted by Au are investigated as electrocatalysts for the direct 2-propanol fuel cells in alkaline media. The results show that Pd is a good electrocatalyst for 2-propanol oxidation and the activity for 2-propanol electrooxidation is higher than that for methanol electrooxidation on the Pd/C electrocatalysts in alkaline media. Addition of Au can significantly increase the palladium catalytic activity and stability for the 2-propanol oxidation. PdAu4:1/C has higher electrocatalytic activity and better stability for the electrooxidation of 2-propanol than Pd/C and E-TEK Pt/C electrocatalysts. The present study shows the promising properties of Au promoted Pd/C as effective electrocatalysts for 2-propanol fuel based direct alcohol fuel cells.     

浸渍法制备Pd/C催化剂过程中Pd前驱体的平衡吸附量与吸附态

使用不同浓度(0～67%)的硝酸对活性炭载体进行预处理,以H2PdCl4为前驱体,用浸渍法制备理论负载量为5%的Pd/C催化剂.浸渍过程中的吸附实验表明,Pd前驱体的平衡吸附量随预处理硝酸浓度的增加而逐渐减小,尤其是浓硝酸预处理的活性炭载体,其上仅有62.54%的Pd前驱体吸附,而37.46%的Pd前驱体仍在水浆液中.分析发现,Pd前驱体的平衡吸附量主要取决于活性炭的零电荷点,表面电荷模型能较好地描述Pd前驱体的吸附规律.当使用浓度≤5%的硝酸进行预处理时,Pd的粒径随硝酸浓度的增加而减小;当硝酸浓度继续增加时,Pd粒径急剧增大.Pd前驱体的平衡吸附量与Pd粒径的大小无直接关系,而Pd前驱体在活性炭表面上吸附物种及数量的不同也对Pd粒径的大小产生影响.活性炭表面基团的增加抑制了PdClyx-吸附物种的生成.当使用≤5%的硝酸处理活性炭时,Pd前驱体的吸附形态主要为PdClxy-和Pd0;当硝酸浓度>5%时,没有检测到PdClyx-的存在.     

发烟硫酸中Pd／C催化甲烷选择氧化制甲醇

以PdCl2为前驱体,采用浸渍法制备了Pd/C催化剂,并在发烟硫酸中考察了其催化甲烷选择氧化反应的性能,采用X射线粉末衍射、X射线光电子能谱、高分辨透射电镜和CO吸附等方法对催化剂进行了表征. 甲烷选择氧化反应得到的主产物硫酸单甲酯经水解后得到甲醇,在5%Pd/C催化剂、Pd用量30 μmol、反应温度180 ℃、反应压力4.0 MPa、反应时间 4 h 和发烟硫酸中SO3含量为50%的优化工艺条件下,甲烷转化率为23.6%, 甲醇的选择性和收率分别为69.5%和16.4%, 在一定程度上可实现催化剂的多次重复使用. Pd/C催化剂上的甲烷选择氧化反应可能遵循亲电取代机理,催化性能与Pd负载量、Pd粒子尺寸和分散度等有关.     

Pd/NH2C3H6-MCM-41催化水介质中的碘苯Ullmann反应

 采用室温共缩聚法合成了胺基改性MCM-41杂化材料(NH2C3H6-MCM-41), 并以此材料为载体制备了负载型Pd催化剂 (Pd/NH2C3H6-MCM-41). 采用X射线衍射、核磁共振、红外光谱、透射电镜、X射线光电子能谱和N2吸附等方法对催化剂进行了表征. 结果表明,催化剂仍保持有MCM-41的孔结构,但其有序度随着 NH2C3H6-基团和Pd含量的增加而降低. 催化剂在以水为溶剂的碘苯偶联反应(Ullmann反应)中显示出优良的催化性能,联苯收率可达63%, 有望为清洁有机合成提供高效非均相催化剂. 胺基修饰的促进作用可归因于催化剂Pd分散度的提高和表面化学性质的改变.     

Study on deactivation and regeneration of Pd/Al2O3 catalyst in hydrogen peroxide production by the anthraquinone process

Deactivated palladium catalysts in the hydrogenation of anthraquinione were regenerated with ethanol, nitric acid, hydrogen peroxide, boiling water and steam, respectively. The deactivated and regenerated catalysts were characterized by XPS, ICP, TG, FTIR, TPD, XRD, etc., and studied in the hydrogenation of anthraquinone. The results showed that the main cause of catalyst deactivation is the coverage of the active component by deposits. The treatments by hydrogen peroxide and boiling water can effectively regenerate the deactivated catalysts. This revised version was published online in August 2006 with corrections to the Cover Date.     

高效组合型 Pd/C 催化剂用于 Suzuki 偶联反应

 采用有机金属 Pd2(dba)3 (dba 为二亚苄基丙酮) 还原分解法制得均匀分布的 Pd 纳米颗粒 (粒径为 3~6 nm) 混合液, 并用活性炭直接吸附得到了组合型 Pd/C 纳米催化剂. 采用透射电子显微镜、X 射线光电子能谱和 X 射线衍射等手段测定了催化剂表面 Pd 颗粒大小分布、晶型和化学态等. 将该催化剂用于 Suzuki 碳-碳偶联反应, 其催化活性比浸渍法制备的 Pd/C 催化剂高 2 倍以上. 以溴代芳烃为底物时, 在 80 oC 下 0.5 h 后偶联产物收率可达 98% 以上. 以邻氯硝基苯为底物时, 在 110 oC 下 1 h 后偶联产物收率可达 64%; 延长反应时间, 产物收率可达 90% 以上.     

Pd/MoO3-TiO2/SiO2光催化CO2与C2H6合成烃类氧化物的反应性能

 采用化学反应改性和等体积浸渍法制备了负载型Pd/MoO3-TiO2/SiO2催化剂,并用IR,FT-Raman,TPD-MS,UV-Vis DRS和活性评价等方法研究了催化剂的表面结构、光吸收性能、化学吸附性能及光催化CO2与C2H6合成烃类氧化物的反应性能. 结果表明,SiO2负载的MoO3和TiO2之间存在着强相互作用,并能部分形成Mo-O-Ti键联,使得两种氧化物微粒均匀分布于载体表面; 表面MoO3和TiO2的复合作用使TiO2/SiO2的吸光带边红移,扩展了其吸光域,Pd的引入明显提高了固体材料的可见光吸收率; CO2和C2H6能较好地吸附在催化剂表面,在紫外光的激发下,CO2吸附态能解离生成CO,而C2H6单位吸附态能部分转化为C和H同时吸附在两个晶格氧上的双位吸附态; 光促CO2和C2H6反应主要生成丙醛、乙醇和乙醛; 在合适的条件下,烃类氧化物的选择性可超过90%.     

钯/聚乙烯醇纤维膜催化水相中的Heck偶联反应

通过静电纺丝和热交联技术、以聚乙烯醇( PVA)作为载体制备了一种电纺纤维膜负载型钯催化剂.利用扫描电镜(SEM)、能谱仪(EDS)和X射线光电子能谱(XPS)对其进行了表征.SEM结果显示:PdCl2的加入导致PVA纤维直径增加、形貌变差,而热交联过程可以减小纤维直径、改善纤维形貌.XPS表征则表明PVA可以还原pd...     

Solid-supported Pd(0): an efficient heterogeneous catalyst for aerobic oxidation of benzyl alcohols into aldehydes and ketones

Solid-supported nano- and microparticles of Pd(0) (SS-Pd) were used as heterogeneous catalysts for aerobic oxidation of benzyl alcohols. Primary and secondary benzyl alcohols gave the corresponding products in good yields. In addition, the catalysts could be reused up to five runs without significant loss of activities.     

PVP-Pd催化剂六氯苯加氢脱氯中两种氢源的贡献

近年来,随着环境问题的日益突出,含卤有机化合物作为一类主要的环境污染物,其加氢脱卤反应的研究越来越多地受到人们的关注.     

Pd/Nb2O5: efficient supported palladium heterogeneous catalyst in the production of key intermediates for the synthesis of ‘sartans’ via the Suzuki reaction

Pd/Nb₂O₅ was prepared, characterized and tested in Suzuki-Miyaura cross-coupling reactions under ligand-free conditions. High yields and selectivities were observed within short reaction times and very low palladium loadings.     

固体强酸催化剂Pd/WO3-ZrO2的制备及其对正庚烷异构化反应的催化性能

 采用共沉淀方法制备了固体酸载体WO3-ZrO2,考察了W含量和焙烧温度等对WO3-ZrO2酸性和物相结构的影响,并且考察了Pd/WO3-ZrO2催化剂对正庚烷异构化反应的催化性能. 结果表明,Pd/WO3-ZrO2催化剂的催化性能与固体强酸的W含量及晶相结构密切相关. 在w(W)=13.2%～15.8%时,经700～800 ℃焙烧,WO3在ZrO2表面达到单层分散,且大部分ZrO2以四方晶相存在,所制备的0.5%Pd/WO3-ZrO2对正庚烷异构化反应的催化活性可达到70.4%,选择性可达到81.0%.     

超声浸渍法制备Pd/Al2O3催化剂及其催化蒽醌加氢性能

 以球形 γ-Al2O3 和 θ-Al2O3 为载体,分别采用超声浸渍和普通浸渍方法制备了Pd含量为0.3%的负载型催化剂,并将其用于蒽醌加氢反应. 采用X射线衍射、 N2吸附和透射电镜等手段对催化剂的理化性质和孔结构进行了分析,考察了浸渍方法对催化剂活性金属分散度的影响. 结果表明,与普通浸渍法相比,超声浸渍法制备的负载型Pd催化剂金属分散度明显提高,因而对蒽醌加氢反应表现出较高的催化活性. 以960 ℃焙烧的球θ-Al2O3 为载体,通过超声浸渍制备的负载型Pd催化剂具有较高的Pd分散度和较大的孔径,在蒽醌加氢反应中对反应物的扩散阻力较小,因而表现出更高的催化活性,而且反应中催化剂的稳定性良好.     

Efficient deprotection of N-benzyloxycarbonyl group from amino acids by hydroxyapatite-bound Pd catalyst in the presence of molecular hydrogen

Hydroxyapatite-bound Pd catalyst was found to be highly effective for the deprotection of N-benzyloxycarbonyl group from amino acids in the presence of molecular hydrogen. The catalyst was also applicable to the hydrogenolysis of a sterically encumbered core-Z-protected poly(amido amine) dendrimer, affording the dendritic amino compound in 99% yield.     

Pd/MWCNTs(多壁碳纳米管)催化剂的制备及其Heck反应催化活性

以浓硝酸处理后的多壁碳纳米管(MWCNTs)为载体,通过微波辅助法简单而快速地制备了高度分散、粒径均一的Pd/MWCNTs催化剂。利用XRD、HRTEM、XPS等手段对催化剂进行了表征。考察了Pd/MWCNTs催化剂对Heck反应的催化活性,并优化了反应温度、碱的种类和用量等反应条件。结果表明,Pd/MWCNTs在Heck反应中具有良好的催化活性。     

Efficient C–H activation of alkylbenzenes and methylcyclohexenes to benzyl esters by Pd(OAc)2/Sn(OAc)2 catalyst system

Selective activation of the side-chain C–H bond of alkylbenzenes and methylcyclohexenes is achieved by a Pd(OAc)₂/Sn(OAc)₂ catalyst system. Under an oxygen atmosphere, various benzyl esters were obtained from the substrates and carboxylic anhydrides. The esters were obtained in more than 100% yield based on the amount of benzoic anhydride, and consumption of oxygen was observed. This suggests that oxygen may be incorporated to produce two moles of the benzoxyl group from one mole of benzoic anhydride. It is interesting that either 1-, 3- or 4-methylcyclohexene reacted with benzoic anhydride to give benzyl benzoate. These carboxylations proceeded at the side-chain alkyl group with high selectivity and no ring-carboxylated product or coupling product was detected. From these results, a mechanism involving the formation of a η³-benzylpalladium complex was proposed. © 1997 John Wiley & Sons, Ltd.     

La2O3对Pd/Al2O3催化蒽醌氢化制H2O2性能的影响

 采用湿浸法制备了用于蒽醌氢化制H2O2的La2O3促进的Pd/Al2O3催化剂,并考察了不同La2O3含量对催化性能的影响. 采用XRD,N2物理吸附,CO2-TPD,H2-O2滴定和电子探针等技术对催化剂进行了表征. 结果表明,加入适量的La2O3能够抑制高温焙烧时Al2O3晶粒的长大,增大催化剂的比表面积,提高金属Pd的分散度,增强载体表面碱性,提高催化剂表面的Pd浓度,减小Pd层厚度,从而提高催化剂的氢化活性. 加入La2O3可使催化剂的Pd负载量由0.281%降至0.188%,而催化剂活性提高了44%.     

Synthesis of 2-Aminoindole Derivatives with Hantzsch Ester Catalyzed by Pd/C

Catalytic hydrogenation of 2‐cyano‐2‐(2‐nitrophenyl)acetates bearing an electron withdrawing substituent to the nitrile, using Hantzsch ester catalyzed by Pd/C, affords 2‐aminoindoles in good to excellent yields.