钌-膦-二胺配合物的电子效应对选择氢化C=C和C=O键的影响

本文合成了一系列新的钌-膦-二胺配合物,并通过核磁和元素分析表征确定了配合物的组分和结构。文中进一步考察了这些配合物用于苄叉丙酮以及苯乙酮和苯乙烯组成的混合物的选择催化加氢,发现随着膦和二胺配体中配位原子碱性的增强,羰基加氢的活性和选择性大幅提高;反之,配位原子碱性减弱不仅降低反应活性,羰基加氢的选择性也大幅降低。基于这些配合物的电子效应对催化氢化性质的影响,我们提出了在钌-膦-二胺体系中的氢活化机理。     

制备因素对Ni-W/C催化剂活性及结构的影响

研究了以沥青活性为载体的Ｎｉ－Ｗ催化剂制备参数与其加氢脱硫，加氢脱氮和加氢脱芳活性的关系，并利用广延Ｘ射线吸收精细结构，透射电镜研究了金属原子的近程配位情况及金属的分散状况，发现金属原子比、催化剂焙烧气氛和温度等对催化剂活性有较大影响，浸渍液ＰＨ值与载体ＰＨＩＥＰ的相对关系对催化活性的影响与浸渍方式有关，表征结果表明，“类ＷＳ２”结构的完整性影响了催化剂活性，焙烧气氛温度影响了金属硫化物的分散度。     

原位制备的铁配合物催化烯烃选择性环氧化

制备了配体2-(2-吡啶基)-噁唑啉。该含氮配体能够在乙腈溶液中与三氟甲磺酸亚铁和其它辅助配体原位形成具有催化活性的六配位金属亚铁配合物。量子化学计算表明配体上的氮原子而非氧原子与铁配位。研究表明,以H_2O_2为氧化剂,该金属配合物能够在乙腈溶液中高活性地催化末端芳香烯烃和脂肪烯烃的环氧化反应;该反应条件温和、迅速、选择性好并且适用底物范围宽泛。辅助配体、溶剂和氧化剂等因素对反应的活性和选择性影响很敏感,文中对这些影响进行了较详细的研究。     

稀土金属配合物催化芳香型乙烯基极性单体立构选择性聚合

鉴于聚合物的立构规整度对其性能起着重要的作用,如何提高聚合物的立构规整度一直以来都是配位聚合领域的重要研究课题。经过几十年的发展,配位聚合已经在 α-烯烃、苯乙烯、共轭二烯烃等非极性烯烃单体的立构选择性聚合方面取得了巨大的成就。但非极性聚烯烃材料表面性能差,而化学性质稳定,难以被后功能化。因此通过极性单体的立构选择性聚合将极性基团引入聚烯烃大分子链中对于提高其性能具有非常重要的意义。然而,在传统的配位聚合中,单体上的极性原子(基团)易于向金属中心配位,导致催化体系失去立构选择性,甚至失去活性。因此选择合适的配体、金属种类与极性单体组合的策略对实现立构选择性聚合至关重要。近年来,针对2-乙烯基吡啶、含杂原子苯乙烯衍生物以及硼氮杂芳香型乙烯基单体的定向聚合,开发了大量的稀土金属配合物催化体系,聚合物的立构规整度取得了较大的突破,同时对单体上极性原子在聚合中的作用也有了新的认识。本综述以单体种类为主线,详细讨论了配体的结构、取代基的电子效应、空间位阻效应、中心稀土金属种类和聚合溶剂等对催化剂聚合活性、立构选择性的影响,并探讨可能的聚合反应机理。     

Pt在MgAl2O4载体上的分散程度对催化苯甲醛加氢反应影响

构建催化剂特别是在亚纳米尺度下分散的贵金属催化剂的构效关系是多相催化研究领域中的主要任务之一.我们采用与金属Pt具有强相互作用的MgAl2O4尖晶石作为载体,通过简单浸渍法制备了在纳米、亚纳米和单原子尺度上分散的Pt催化剂.首先利用X射线衍射和原子分辨的球差校正电镜,确定了Pt在MgAl2O4尖晶石载体表面上随负载量增大逐渐形成孤立的和相邻的单原子Pt,然后逐渐形成无定形Pt聚集体和小晶粒;然后利用电感耦合等离子体光谱和CO化学吸附测定了催化剂中Pt的含量和分散度;进一步通过测定CO在Pt表面吸附的红外光谱,区分了载体表面单原子和金属颗粒表面原子的CO吸附特征结构,并据此对不同结构的Pt原子进行了半定量估算.考察了具有不同Pt分散结构的Pt/MgAl2O4催化剂的催化苯甲醛选择性加氢能力,发现以载体表面Pt单原子物种为主的催化剂,可在较宽的温度区间内保持较高的部分加氢产物苯甲醇的选择性(60–150oC,苯甲醇选择性99.4–97.9％,甲苯选择性～0.4％),而以Pt纳米颗粒为主的催化剂上苯甲醇选择性降低显著,同时生成较多深度加氢产物甲苯(60–150oC,苯甲醇选择性99.0–93.1％,甲苯选择性0.7–5.0％).此外,我们测定了各催化剂在不同转化率(～20–90％)时催化剂加氢反应的质量比活性和转化频率(TOF),并在较低苯甲醛转化率(～20％)时,估算了不同结构Pt物种对苯甲醛加氢反应的本征活性,发现Pt纳米颗粒表面原子比MgAl2O4载体表面Pt单原子本征活性更高(4807 h–1 versus 3277 h–1).综上,Pt单原子催化剂具有贵金属原子利用率高,本征活性和加氢选择性高等优点;Pt纳米催化剂表面原子深度加氢能力强,加氢选择性较差,虽本征活性更高,但不足以补偿贵金属原子利用率降低带来的活性损失,Pt质量比活性显著低于单原子催化剂.此外,MgAl2O4尖晶石负载的单原子Pt催化剂也具有良好的催化反应循环稳定性,是一种较为理想的催化苯甲醛选择性加氢制苯甲醇催化剂.     

视角:单原子尺度的负载型金属催化剂

综述了负载型单原子催化剂设计的最新进展,以及负载型单原子催化剂在多种反应,如低温水汽变换、甲醇蒸汽重整、选择性乙醇脱氢、炔烃和二烯烃的选择性加氢等反应中的应用.研究活性金属原子位的固有活性和选择性,并与相应的金属纳米颗粒和次纳米簇的性质相比较是非常重要的.同时,理解在不同反应环境下稳定的活性金属原子位的组成,并最大化其负载量可使我们设计出适合工业应用的强健催化剂.在实际工作中,应将催化剂活性和稳定性研究相结合,尽可能遵循活性位随催化剂实时处理条件的变化规律.原子尺度的先进表征方法至关重要,可用于指导设计新催化剂.     

Pt在MgAl_2O_4载体上的分散程度对催化苯甲醛加氢反应影响（英文）

构建催化剂特别是在亚纳米尺度下分散的贵金属催化剂的构效关系是多相催化研究领域中的主要任务之一.我们采用与金属Pt具有强相互作用的Mg Al_2O_4尖晶石作为载体,通过简单浸渍法制备了在纳米、亚纳米和单原子尺度上分散的Pt催化剂.首先利用X射线衍射和原子分辨的球差校正电镜,确定了Pt在Mg Al_2O_4尖晶石载体表面上随负载量增大逐渐形成孤立的和相邻的单原子Pt,然后逐渐形成无定形Pt聚集体和小晶粒;然后利用电感耦合等离子体光谱和CO化学吸附测定了催化剂中Pt的含量和分散度;进一步通过测定CO在Pt表面吸附的红外光谱,区分了载体表面单原子和金属颗粒表面原子的CO吸附特征结构,并据此对不同结构的Pt原子进行了半定量估算.考察了具有不同Pt分散结构的Pt/Mg Al_2O_4催化剂的催化苯甲醛选择性加氢能力,发现以载体表面Pt单原子物种为主的催化剂,可在较宽的温度区间内保持较高的部分加氢产物苯甲醇的选择性(60–150oC,苯甲醇选择性99.4–97.9%,甲苯选择性~0.4%),而以Pt纳米颗粒为主的催化剂上苯甲醇选择性降低显著,同时生成较多深度加氢产物甲苯(60-150oC,苯甲醇选择性99.0–93.1%,甲苯选择性0.7–5.0%).此外,我们测定了各催化剂在不同转化率(~20–90%)时催化剂加氢反应的质量比活性和转化频率(TOF),并在较低苯甲醛转化率(~20%)时,估算了不同结构Pt物种对苯甲醛加氢反应的本征活性,发现Pt纳米颗粒表面原子比Mg Al_2O_4载体表面Pt单原子本征活性更高(4807 h–1 versus 3277 h–1).综上,Pt单原子催化剂具有贵金属原子利用率高,本征活性和加氢选择性高等优点;Pt纳米催化剂表面原子深度加氢能力强,加氢选择性较差,虽本征活性更高,但不足以补偿贵金属原子利用率降低带来的活性损失,Pt质量比活性显著低于单原子催化剂.此外,Mg Al_2O_4尖晶石负载的单原子Pt催化剂也具有良好的催化反应循环稳定性,是一种较为理想的催化苯甲醛选择性加氢制苯甲醇催化剂.     

烷烃加氢异构化反应

综述了烷烃加氢异构化反应中的正碳离子异构和裂化机理、孔口与钥匙锁催化、择形催化及双分子机理,详细论述了分子筛基双功能催化剂酸性、金属、金属酸位比、孔道、晶粒尺寸和催化剂改性对烷烃加氢异构反应活性、异构选择性等的影响。论述了近期烷烃加氢异构催化剂改性的新方法。提出针对不同催化剂体系,根据反应机理提高异构催化剂活性和选择性的途径。     

视角:单原子尺度的负载型金属催化剂（英文）

综述了负载型单原子催化剂设计的最新进展,以及负载型单原子催化剂在多种反应,如低温水汽变换、甲醇蒸汽重整、选择性乙醇脱氢、炔烃和二烯烃的选择性加氢等反应中的应用.研究活性金属原子位的固有活性和选择性,并与相应的金属纳米颗粒和次纳米簇的性质相比较是非常重要的.同时,理解在不同反应环境下稳定的活性金属原子位的组成,并最大化其负载量可使我们设计出适合工业应用的强健催化剂.在实际工作中,应将催化剂活性和稳定性研究相结合,尽可能遵循活性位随催化剂实时处理条件的变化规律.原子尺度的先进表征方法至关重要,可用于指导设计新催化剂.     

制备因素对Ni－W／C催化剂活性及结构的影响

研究了以沥青活性炭为载体的Ｎｉ－Ｗ催化剂制备参数与其加氢脱硫（ＨＤＳ）、加氢脱氮（ＨＤＮ）和加氢脱芳（ＨＤＡ）活性的关系,并利用广延Ｘ射线吸收精细结构．（ＥＸＡＦ）、透射电镜（ＴＥＭ）研究了金属原子的近程配位情况及金属的分散状况．发现金属原子比、催化剂焙烧气氛和温度等对催化剂活性有较大影响．浸渍液ＰＨ值与载体ＰＨＩＥＰ的相对关系对催化活性的影响与浸渍方式有关．表征结果表明,“类ＷＳ２”结构的完整性影响了催化剂活性,焙烧气氛温度影响了金属硫化物的分散度．     

MIL-100(Fe) Supported Pt−Co Nanoparticles as Active and Selective Heterogeneous Catalysts for Hydrogenation of 1,3-Butadiene

Superior catalytic performance for selective 1,3-butadiene (1,3-BD) hydrogenation can usually be achieved with supported bimetallic catalysts. In this work, Pt−Co nanoparticles and Pt nanoparticles supported on metal–organic framework MIL-100(Fe) catalysts (MIL=Materials of Institut Lavoisier, PtCo/MIL-100(Fe) and Pt/MIL-100(Fe)) were synthesized via a simple impregnation reduction method, and their catalytic performance was investigated for the hydrogenation of 1,3-BD. Pt1Co1/MIL-100(Fe) presented better catalytic performance than Pt/MIL-100(Fe), with significantly enhanced total butene selectivity. Moreover, the secondary hydrogenation of butenes was effectively inhibited after doping with Co. The Pt1Co1/MIL-100(Fe) catalyst displayed good stability in the 1,3-BD hydrogenation reaction. No significant catalyst deactivation was observed during 9 h of hydrogenation, but its catalytic activity gradually reduces for the next 17 h. Carbon deposition on Pt1Co1/MIL-100(Fe) is the reason for its deactivation in 1,3-BD hydrogenation reaction. The spent Pt1Co1/MIL-100(Fe) catalyst could be regenerated at 200 °C, and regenerated catalysts displayed the similar 1,3-BD conversion and butene selectivity with fresh catalysts. Moreover, the rate-determining step of this reaction was hydrogen dissociation. The outstanding activity and total butene selectivity of the Pt1Co1/MIL-100(Fe) catalyst illustrate that Pt−Co bimetallic catalysts are an ideal alternative for replacing mono-noble-metal-based catalysts in selective 1,3-BD hydrogenation reactions.     

IB金属对Ni/SiO2催化剂乙炔选择性加氢反应性能的影响

乙烯是合成聚乙烯的原料,其主要来源是石油裂解气,其中少量的乙炔杂质会严重毒化生产聚乙烯的催化剂,因此需要将其去除.对于乙炔选择加氢反应,传统工业上使用的是Pd基催化剂,尽管其乙炔转化率很高,但对乙烯的选择性很低.我们前期的研究发现,IB族金属(Au,Ag和Cu)与Pd形成的合金单原子催化剂可以有效地提高乙烯的选择性.作为与Pd同组的非贵金属,Ni催化剂在多种催化加氢反应中显示出优异活性,而在乙炔选择加氢反应中,Ni是否能够替代贵金属Pd尚无定论.本文系统地研究了IB金属对Ni/SiO2催化剂乙炔选择性加氢性能的影响.与Pd/SiO2催化剂不同,单金属Ni/SiO2催化剂在低温下不具有活性.将IB金属添加到Ni/SiO2催化剂中,可以显著提高其催化活性以及对乙烯的选择性.其中,AuNix/SiO2和CuNix/SiO2催化剂的催化活性随还原温度升高而提高,而AgNix/SiO2催化剂对预处理温度不敏感.通过调变IB/Ni原子比和还原温度优化了催化剂的催化性能,发现优化后的三种催化剂(CuNi0.125/SiO2、AgNi0.5/SiO2和AuNi0.5/SiO2)的活性和选择性随反应温度升高表现出相似的变化趋势.催化稳定性考察结果显示,CuNi0.125/SiO2催化剂表现出最高选择性和稳定性;尽管AuNi0.5/SiO2的初始活性最高,但是稳定性最低.采用XRD、TPR和微量吸附量热等表征手段对不同IB金属对Ni基催化剂性质的影响进行了系统考察.以Cu-Nix/SiO2催化剂为例,H2-TPR测试结果表明,Cu-Ni双金属纳米颗粒的形成使得还原温度低于相应的单金属催化剂,表明铜和镍之间存在明显的相互作用.此外,通过TPR获得的CuNix/SiO2催化剂上的氢气消耗量与理论耗氢量相吻合,表明在还原处理的过程中双金属催化剂中的CuO和NiO可以被完全还原.乙炔的微量吸附量热结果表明,在CuNi0.125/SiO2,AgNi0.5/SiO2,AuNi0.5/SiO2和Ni0.5/SiO2催化剂上的初始吸附热分别为187,196,304和103 kJ/mol,即它们的初始乙炔吸附强度顺序为AuNi0.5/SiO2>AgNi0.5/SiO2>CuNi0.125/SiO2>Ni0.5/SiO2.该结果与三者的初始催化活性顺序一致,表明IB金属的加入可以增强乙炔在催化剂表面的吸附,从而提高催化活性.     

Diatomite-supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts for selective hydrogenation of long-chain aliphatic esters

Diatomite supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts with various metal compositions were prepared and characterized by means of X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the metal nanoparticles were uniformly distributed on the support, and their size was centered around 8nm with a relatively narrow size distribution. The catalysts were used to catalyze hydrogenation of long-chain aliphatic esters, including methyl palmitate, methyl stearate, and methyl laurate. It was indicated that the all diatomite-supported Pd-based bimetal catalysts were active to the selective hydrogenation of long-chain esters to corresponding alcohols at 270°C, originated from the synergistic effect between the metal particles and the diatomite support. For the selective hydrogenation of methyl palmitate, Pd-Cu/diatomite with metal loading of 1% and Pd/Cu=3 displayed the highest performance, giving a 1-hexadecanol yield of 82.9% at the substrate conversion of 98.8%.     

Pd/TiN nanocomposite catalysts for selective hydrogenation of phenol and its derivatives

Pd/TiN nanocomposite catalysts were fabricated for one-step selective hydrogenation of phenol to cyclohexanone successfully. High conversion of phenol (99%) and selectivity of cyclohexanone (98%) were obtained at 30℃ and 0.2 MPa H₂ for 12 h in the mixed solvents of H₂O and CH₂Cl₂. The Pd nanoparticles were stable in the reaction, and no aggregation was detected after four successive runs. The catalytic activity and selectivity depended on slightly the Pd particle sizes. The generality of the catalysts for this reaction was demonstrated by the selective hydrogenation of phenol derivatives, which showed that the catalyst was selective for the formation of cyclohexanone.     

Catalytic Performance of Carbon Materials Supported Pd Nanoparticles in Selective Hydrogenation of Acetylene

Pd/C catalysts were prepared by deposited Pd nanoparticles (NPs) on different carbon supports including activated carbon (AC), graphite oxide (GO), and reduced graphite oxide (rGO) using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.     

金属有机骨架高温自还原制备高性能等级孔碳负载Co基催化剂

以钴基金属有机框架为前驱体, 利用一步高温碳化自还原法, 通过精确调控碳化过程, 实现等级孔道结构及钴纳米颗粒分散性的可控调节, 制备出高催化活性及产物选择性的等级孔碳负载Co基催化剂. 研究发现, 600 ℃碳化后的催化剂为具有高比表面积的等级孔道结构和高分散的钴纳米颗粒, 在选择性催化1,3-丁二烯加氢反应中, 丁二烯完全转化温度低至60 ℃, 对应丁烯的选择性高达61%, 实现了低温高选择性催化加氢.     

Study of Carbon Nanotube Supported Co-Mo Selective Hydrodesulphurization Catalysts for Fluid Catalytic Cracking Gasoline

In this paper, carbon nanotube supported Co-Mo catalysts for selective hydrodesulphurization （HDS） of fluid catalytic cracking （FCC） gasoline were studied, using di-isobutylene, cyclohexene, 1-octene and thiophene as model compounds to simulate FCC gasoline. The results show that the Co-Mo/CNT has very high HDS activity and HDS/hydrogenation selectivity comparing with the Co-Mo/γ-Al2O3 and Co-Mo/AC catalyst systems. The saturation ratio of cyclohexene was lower than 50%, and the saturation ratio of 1,3-di-isobutylene lower than 60% for the Co-Mo/CNT catalysts. Co/Mo atomic ratio was found to be one of the most important key factors in influencing the hydrogenation selectivity and HDS activity, and the most suitable Co/Mo atomic ratio was 0.4. Co/CNT and Mo/CNT mono-metallic catalysts showed lower HDS activity and selectivity than the Co-Mo/CNT bi-metallic catalysts.     

氧化铁负载铂纳米簇催化卤代硝基苯本体氢化性质研究

复相金属催化剂中的载体效应研究具有重要意义。我们以结构不同的氧化铁载体吸附"非保护型"Pt金属纳米簇制备了具有相同Pt纳米簇的Pt/Fe_3O_4、Pt/γ-Fe_2O_3和Pt/α-Fe_2O_3催化剂,考察了其在无溶剂条件下(本体条件)催化邻氯硝基苯(o-CNB)选择性氢化反应的性能,发现三种铂/氧化铁催化剂的催化选择性远高于商购铂/碳催化剂,Pt/γ-Fe_2O_3和Pt/α-Fe_2O_3的催化选择性明显高于Pt/Fe_3O_4,而Pt/Fe_3O_4的催化活性较Pt/α-Fe_2O_3高50%。铂/氧化铁对不同卤代硝基苯的本体选择性氢化反应表现出优良的催化性能,相应卤代苯胺产物的选择性均可达到99%以上。考察了温度、氢气压力对Pt/Fe_3O_4催化o-CNB本体氢化性能的影响。本工作为理解氧化铁负载金属纳米簇催化剂的特殊催化性质,进而发展高效金属纳米簇基催化体系提供了新的基础。     

Selective hydrogenation of dienic and acetylenic compounds on metal-containing catalysts

Studies on selective hydrogenation of dienic and acetylenic hydrocarbons and their derivatives on metal-containing catalysts are reviewed. The review covers publications over a wide period of time and concentrates on the fundamental principles of catalyst operation. The catalysts modified in the surface layer were shown to be promising for selective hydrogenation.     

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.