贵金属对NM/WO_3-ZrO_2(NM=Ru,Rh和Pd)催化乙烯直接氧化制乙酸反应的影响

 研究了负载 Ru, Rh 和 Pd 的 WO3-ZrO2 催化剂在乙烯直接氧化制乙酸反应中的催化性能. 结果显示, 负载的贵金属对催化剂的催化性能有非常重要的影响. Rh/WO3-ZrO2 催化剂具有最高的乙烯转化率, 而 Ru/WO3-ZrO2 催化剂对反应几乎没有活性. H2 化学吸附结果显示, 高的催化性能来源于高的金属分散度. Pd/WO3-ZrO2 催化剂显示了最高的乙酸选择性 (75%), 而其它两个催化剂的乙酸选择性都非常低 (~10%). 程序升温氧化和程序升温还原结果显示, 贵金属–O 键的键强对产物的选择性具有重要的影响. 弱的贵金属–O 键可以通过将氧插入到乙烯和/或乙醛中而有利于乙酸的生成, 而强的贵金属–O 键会导致乙烯完全氧化为 COx.     

On the Functional Group Tolerance of Ester Hydrogenation and Polyester Depolymerisation Catalysed by Ruthenium Complexes of Tridentate Aminophosphine Ligands

The synthesis of a range of phosphine‐diamine, phosphine‐amino‐alcohol, and phosphine‐amino‐amide ligands and their ruthenium(II) complexes are reported. Five of these were characterised by X‐ray crystallography. The activities of this collection of catalysts were initially compared for the hydrogenation of two model ester hydrogenations. Catalyst turnover frequencies up to 2400 h^?1 were observed at 85 °C. However, turnover is slow at near ambient temperatures. By using a phosphine‐diamine Ru^II complex, identified as the most active catalyst, a range of aromatic esters were reduced in high yield. The hydrogenation of alkene‐, diene‐, and alkyne‐functionalised esters was also studied. Substrates with a remote, but reactive terminal alkene substituent could be reduced chemoselectively in the presence of 4‐dimethylaminopyridine (DMAP) co‐catalyst. The chemoselective reduction of the ester function in conjugated dienoate ethyl sorbate could deliver (2E,4E)‐hexa‐2,4‐dien‐1‐ol, a precursor to leaf alcohol. The monounsaturated alcohol (E)‐hex‐4‐en‐1‐ol was produced with reasonable selectivity, but complete chemoselectivity of C?O over the diene is elusive. High chemoselectivity for the reduction of an ester over an alkyne group was observed in the hydrogenation of an alkynoate for the first time. The catalysts were also active in the depolymerisation reduction of samples of waste poly(ethylene terephthalate) (PET) to produce benzene dimethanol. These depolymerisations were found to be poisoned by the ethylene glycol side product, although good yields could still be achieved.     

Transfer Hydrogenation of Ketones Catalyzed by Surface‐Active Ruthenium and Rhodium Complexes in Water

An improved, high‐yield, one‐pot synthetic procedure for water‐soluble ligands functionalized with trialkyl ammonium side groups H₂N(CH₂)₂NHSO₂‐p‐C₆H₄CH₂[NMe₂(C_nH_2n+1)]⁺ ( [HL ⁿ ]⁺ ; n=8, 16) was developed. The corresponding new surface‐active complexes [(p‐cymene)RuCl( L ⁿ )] and [Cp*RhCl( L ⁿ )] (Cp*=η⁵‐C₅Me₅) were prepared and characterized. For n=16 micelles are formed in water at concentrations as low as 0.6 mM , as demonstrated by surface‐tension measurements. The complexes were used for catalytic transfer hydrogenation of ketones with formate in water. Highly active catalyst systems were obtained in the case of complexes bearing C₁₆ tails due to their ability to be adsorbed at the water/substrate interface. The scope of these catalyst systems in aqueous solutions was extended from partially water soluble aryl alkyl ketones (acetophenone, butyrophenone) to hydrophobic dialkyl ketones (2‐dodecanone).     

Hydrogen Isotope Exchange Catalyzed by Ru Nanocatalysts: Labelling of Complex Molecules Containing N-Heterocycles and Reaction Mechanism Insights

Ruthenium nanocatalysis can provide effective deuteration and tritiation of oxazole, imidazole, triazole and carbazole substructures in complex molecules using D₂ or T₂ gas as isotopic sources. Depending on the substructure considered, this approach does not only represent a significant step forward in practice, with notably higher isotope uptakes, a broader substrate scope and a higher solvent applicability compared to existing procedures, but also the unique way to label important heterocycles using hydrogen isotope exchange. In terms of applications, the high incorporation of deuterium atoms, allows the synthesis of internal standards for LC-MS quantification. Moreover, the efficacy of the catalyst permits, even under subatmospheric pressure of T₂ gas, the preparation of complex radiolabeled drugs owning high molar activities. From a fundamental point of view, a detailed DFT-based mechanistic study identifying undisclosed key intermediates, allowed a deeper understanding of C−H (and N−H) activation processes occurring at the surface of metallic nanoclusters.     

Hydrogenation of sorbic acid in mono- and biphasic systems catalyzed by Rh(I)- phosphine complexes

Hydrogenation of sorbic acid in ethyl acetate with [RhCl(PPh₃)₃] was studied and compared to the hydrogenation of its K-salt in water catalyzed by [RhCl(mtppms)₃]. Aqueous biphasic hydrogenation of sorbic acid with [RhCl(mtppms)₃] as catalyst proceeded faster and more selectively than that in homogeneous solutions and afforded trans-hex-2-enoic acid with 80% selectivity.     

Syntheses and structural characterizations of the octahedral boride clusters [Rh2Ru4H(CO)16−2x (nbd) x B] (x=1,2) and gold(I) phosphine derivatives (nbd=norbornadiene)

The reaction of less than one equivalent of [Rh₂Cl₂(nbd)₂] with [Ru₄H(CO)₁₂BH]⁻, which contains a semi-interstitial boron atom, yields the heterometallic boride clustercis-[Rh₂Ru₄H(CO)₁₂(nbd)₂B] which has been characterized by spectroscopic and X-ray diffraction methods. The cluster has an octahedral core, consistent with an 86 electron count. Deprotonation yields the conjugate basecis-[Rh₂Ru₄(CO)₁₂(nbd)₂B]⁻ which has been isolated and fully characterized as the [(Ph₃P)₂N]⁺ salt. There is little structural perturbation upon going fromcis-[Rh₂Ru₄H(CO)₁₂(nbd)₂B] tocis-[Rh₂Ru₄(CO)₁₂(nbd)₂B]⁻ and neither cluster shows a tendency for the formation of thetrans skeletal isomer in contrast to the analogous carbonyl clustercis-[Rh₂Ru₄(CO)₁₆B]⁻. If the reaction of [Rh₂Cl₂(nbd)₂] with [Ru₄H(CO)₁₂BH]⁻ is allowed to proceed for 30 min and [R ₃PAuCl] (R=Ph, C₆H₁₁, 2-MeC₆H₄) is then added, the clusterscis-[Rh₂Ru₄(CO)₁₂(nbd)₂B(AuPR₃)] andcis-[Rh₂Ru₄(CO)₁₄(nbd)B(AuPR₃)] are formed in yields that are dependent upon the initial reaction period. The single crystal structures ofcis-[Rh₂Ru₄(CO)₁₂(nbd)₂B(AuPPh₃)] andcis-[Rh₂Ru₄(CO)₁₄(nbd)B(AuPPh₃)] are reported. In contrast to their all-carbonyl analoguescis-[Rh₂Ru₄(CO)₁₆B(AuPR ₃)] (R=Ph or C₆H₁₁), the nbd derivatives do not undergocis →trans skeletal isomerism.     

Ru3(CO)9(TPPTS)3催化的水/有机两相芳香硝基化合物CO选择性还原的研究

将水溶性膦/钌配合物Ru₃(CO)₉(TPPTS)₃(TPPTS:三苯基膦三-间磺酸钠)用于以CO为还原剂的水/有机两相芳香硝基化合物选择还原为芳胺的反应,发现相转移催化剂对反应有明显的促进作用,其中以添加十六烷基三甲基溴化铵(CTAB)的效果最好.以邻氯硝基苯为底物考察了相转移催化剂浓度、NaOH浓度、反应温度、压力等对反应转化率和选择性的影响.当反应条件为120℃,4MPa,3mol/LNaOH时,反应8h,邻氯硝基苯的转化率和邻氯苯胺的选择性均可达到99.9%.而且对含有羰基、氰基的芳香硝基化合物也有很高的活性和选择性.催化剂循环3次后,邻氯硝基苯的转化率和邻氯苯胺的收率仍可达到92%.     

乙酸在Rh(100)表面吸附和分散的HREELS和TDS研究

 用高分辨电子能量损失谱（HREELS）和热脱附谱（TDS）研究了乙酸在Rh（100）表面上的吸附和分解,提出了乙酸吸附和分解反应的模式．130K时,高暴露量的乙酸在Rh（100）表面上形成多层吸附的凝聚态乙酸．升温至290K时,部分乙酸以分子形式直接脱附,另一部分乙酸分子通过O—H键断裂形成乙酸根和氢吸附在表面上;在升温至400K的过程中,乙酸根在表面发生两个相互竞争的反应,即乙酸根分解成CO,CHx,O和H,以及乙酸根分解成CHx,H和CO2;升温至500K,只剩下CHx,O和CO吸附在表面上;600K后,表面吸附的CHx完全解离,同时表面吸附的碳原子和氧原子结合成CO脱附．     

Insights into Electrochemical CO2 Reduction on SnS2: Main Product Switch from Hydrogen to Formate by Pulsed Potential Electrolysis

Tin disulfide (SnS₂) is a promising candidate for electrosynthesis of CO₂-to-formate while the low activity and selectivity remain a great challenge. Herein, we report the potentiostatic and pulsed potential CO₂RR performance of SnS₂ nanosheets (NSs) with tunable S-vacancy and exposure of Sn-atoms or S-atoms prepared controllably by calcination of SnS₂ at different temperatures under the H₂/Ar atmosphere. The catalytic activity of S-vacancy SnS₂ (V_s-SnS₂) is improved 1.8 times, but it exhibits an exclusive hydrogen evolution with about 100 % FE under all potentials investigated in the static conditions. The theoretical calculations reveal that the adsorption of *H on the V_s-SnS₂ surface is energetically more favorable than the carbonaceous intermediates, resulting in active site coverage that hinders the carbon intermediates from being adsorbed. Fortunately, the main product can be switched from hydrogen to formate by applying pulsed potential electrolysis benefiting from in situ formed partially oxidized SnS_2−x with the oxide phase selective to formate and the S-vacancy to hydrogen. This work highlights not only the V_s-SnS₂ NSs lead to exclusively H₂ formation, but also provides insights into the systematic design of highly selective CO₂ reduction catalysts reconstructed by pulsed potential electrolysis.     

CuO-ZnO-ZrO2的柠檬酸燃烧法制备及其催化CO2加氢合成甲醇的性能

采用柠檬酸燃烧法制备了CuO-ZnO-ZrO2(CZZ)催化剂,并将其用于CO2加氢合成甲醇反应.按推进剂化学原理对燃烧反应进行了分析,并采用热重-差热分析(TG-DTA)技术记录了其燃烧行为.采用X射线衍射(XRD)、氮吸附、程序升温还原(TPR)及氧化亚氮(N2O)反应吸附技术对制得的催化剂进行了表征.结果表明:柠檬酸燃烧法的燃烧过程比较温和,燃料用量对催化剂物化和催化性能的影响不大,并结合燃烧反应的特点进行了解释.此外,还对三种燃料(柠檬酸、尿素和甘氨酸)的用量与CZZ性能之间的关系进行了比较,表明柠檬酸作燃料具有更好的工艺可控性.柠檬酸燃烧法是一种简单、快速且有效的制备CZZ催化剂的方法.     

Catalytic Hydrogen Production by Ruthenium Complexes from the Conversion of Primary Amines to Nitriles: Potential Application as a Liquid Organic Hydrogen Carrier

The potential application of the primary amine/nitrile pair as a liquid organic hydrogen carrier (LOHC) has been evaluated. Ruthenium complexes of formula [(p‐cym)Ru(NHC)Cl₂] (NHC=N‐heterocyclic carbene) catalyze the acceptorless dehydrogenation of primary amines to nitriles with the formation of molecular hydrogen. Notably, the reaction proceeds without any external additive, under air, and under mild reaction conditions. The catalytic properties of a ruthenium complex supported on the surface of graphene have been explored for reutilization purposes. The ruthenium‐supported catalyst is active for at least 10 runs without any apparent loss of activity. The results obtained in terms of catalytic activity, stability, and recyclability are encouraging for the potential application of the amine/nitrile pair as a LOHC. The main challenge in the dehydrogenation of benzylamines is the selectivity control, such as avoiding the formation of imine byproducts due to transamination reactions. Herein, selectivity has been achieved by using long‐chain primary amines such as dodecylamine. Mechanistic studies have been performed to rationalize the key factors involved in the activity and selectivity of the catalysts in the dehydrogenation of amines. The experimental results suggest that the catalyst resting state contains a coordinated amine.     

Selective Hydrogen Generation from Formic Acid with Well‐Defined Complexes of Ruthenium and Phosphorus–Nitrogen PN3‐Pincer Ligand

An unsymmetrically protonated PN³‐pincer complex in which ruthenium is coordinated by one nitrogen and two phosphorus atoms was employed for the selective generation of hydrogen from formic acid. Mechanistic studies suggest that the imine arm participates in the formic acid activation/deprotonation step. A long life time of 150 h with a turnover number over 1 million was achieved.     

Rapid monitoring of the nature and interconversion of supported catalyst phases and of their influence upon performance: CO oxidation to CO2 by gamma-Al2O3 supported Rh catalysts

Spatially and temporally resolved energy-dispersive EXAFS (EDE) has been utilised in situ to study supported Rh nanoparticles during CO oxidation by O2 under plug-flow conditions. Three distinct phases of Rh supported upon Al2O3 were identified by using EDE at the Rh K-edge during CO oxidation. Their presence and interconversion are related to the efficiency of the catalysts in oxidising CO to CO2. A metallic phase is only found at higher temperatures (>450 K) and CO fractions (CO/O2 > 1); an oxidic phase resembling Rh2O3 dominates the active catalyst under oxygen-rich conditions. Below about 573 K, and in CO-rich environments, high proportions of isolated Rh(I)(CO)2 species are found to co-exist with metallic Rh nanoparticles. Alongside these discrete situations a large proportion of the active phase space comprises small Rh cores surrounded by layers of active oxide. Confinement of Rh to nanoscale domains induces structural lability that influences catalytic behaviour. For CO oxidation over Rh/Al2O3 there are two redox phase equilibria alongside the chemistry of CO and O adsorbed upon extended Rh surfaces.     

溶胶-凝胶自燃烧法制备的CuO-ZnO/Al2O3及催化二氧化碳加氢制甲醇的性能研究

采用溶胶-凝胶自燃烧法,以柠檬酸为燃料制备了多种CuO-ZnO/Al2O3催化剂.利用N2静态吸附(BET)、X射线衍射(XRD)、扫描电子显微镜(SEM)、X-射线光电子能谱(XPS)和H2程序升温还原(H2-TPR)等方法研究了柠檬酸与硝酸盐比例关系对催化剂物化性质,形貌和还原性能的影响.并将其用于二氧化碳加氢制甲醇反应,考察催化剂的CO2转化率,甲醇选择性以及甲醇时空收率等催化性能.实验结果表明,当柠檬酸用量等于化学计量比时,CuO-ZnO/Al2O3催化剂的催化性能最好,当柠檬酸用量大于化学计量比时,催化性能次之,且变化不大,但当柠檬酸用量小于化学计量比时,催化性能明显降低.这一结果与其物化性质和还原性能有关,当柠檬酸用量等于或大于化学计量比时,催化剂中CuO颗粒较小,分散均匀,且分散度高.     

微波水热制备Fe-Zr催化剂及其CO加氢制烯烃性能研究

以ZrO（NO₃）₂·2H₂O和Fe（NO₃）₃·9H₂O为原料,采用微波水热法制备了不同Fe₂O₃/ZrO₂物质的量比的Fe-Zr催化剂,并经K改性,研究了其催化CO加氢一步法合成低碳烯烃性能。采用XRD、SEM、TEM和N₂吸附-脱附等手段对其物相、形貌和比表面积等进行了表征。结果表明,与共沉淀法相比,微波水热制备的Fe-Zr催化剂颗粒粒径均一,具有相对较小的比表面积和较大的孔径;在CO加氢反应中,Zr助剂的添加显著改善了产物分布,Fe、Zr间适宜的相互作用和相对较大的孔径,有利于抑制CH₄的生成,提高烯烃选择性。随着Fe₂O₃/ZrO₂物质的量比的降低,Fe、Zr间相互作用逐渐增强,烯烃选择性和收率先增加后降低。当Fe₂O₃/ZrO₂物质的量比为75：25时,在340 ℃、1.5 MPa、1 000 h^-1和H₂/CO物质的量比为2的条件下,烯烷比（O/P）达4.86,总烯烃收率达62.57 g/m³。     

水热法Fe-Mn催化剂制备及其合成气制低碳烯烃催化活性

以水热合成法制备了K原位改性的Fe-Mn催化剂,考察了其CO加氢合成低碳烯烃催化活性。采用SEM、TEM、XRD、H₂-TPR和FT-IR等手段对催化剂进行了表征。结果表明,制备的催化剂前驱体呈50~70 nm的球形颗粒,表面富含羰基和羟基,物相组成以Fe₃O₄为主,用于反应后有Fe₅C₂和MnCO₃相生成。与共沉淀法制备催化剂相比,在设定的反应条件下,不同K含量改性的催化剂均具有较高的活性,以原料配比Fe:Mn:C₆:K=3:1:5:0.10的催化剂性能最佳,CO转化率达95.02%,总低碳烯烃收率为62.86 g/m³(H₂+CO),CH₄和CO₂选择性分别为13.88%和13.98%。