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1.
Several supported gold metal catalysts with different Au nanoparticles sizes were prepared and evaluated for the chemoselective hydrogenation of cinnamaldehyde (CA) to cinnamyl alcohol (CAL). To investigate the structure-activity relationship, stability of catalyst, heterogeneity and recyclability, the structural characteristics of materials and Au catalysts (fresh and spent catalysts) were studied by employing variety of physico-chemical techniques. The interrelationship among Au nanoparticles size (nm) with turnover frequency (h−1) of Au catalysts has also been explored. Among the various Au catalysts tested, nitrogen-doped mesoporous carbon (NMC) supported Au catalyst having homogeneously dispersed (78.8%) Au nanoparticles (1.6 nm) synthesized by sol-immobilization method (Au-NMC-SI) demonstrated improved catalytic activity affording 78% CAL selectivity and 94.2% CA conversion without using any promoter. Moreover, Au-NMC-SI catalyst exhibited good recyclability and stability. The catalyst synthesis approach described in this investigation opens up a novel strategy for the design of highly efficient metal nano-catalysts supported on NMC materials. 相似文献
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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 总被引:8,自引:0,他引:8
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。 相似文献
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Ni nanoparticles (Ni(1) and Ni(2)) and Ni loaded SiMCM‐41 (15Ni/SiMCM‐41) were prepared and characterized with XRD, TEM, N2 adsorption, CO chemisorption, and H2‐TPR. The Ni specific surface area followed the order of 15Ni/SiMCM‐41 > Ni(1) >> Ni(2), whereas the Ni particle size exhibited the opposite trend. These catalysts were utilized for vapour phase hydrogenation of cinnamaldehyde at 1 atm and 200 °C in a fixed‐bed, down flow reactor. The main products include hydrocinnamaldehyde, styrene, ethylbenzene, and 2‐phenyl‐1‐propanol. The catalytic activity decreased in the same order as that of Ni specific surface areas. The SiMCM‐41 support possessed very large surface area, leading to enhanced dispersion and specific surface area of Ni nanoparticles. As a result, the 15Ni/SiMCM‐41 catalyst exhibited the highest activity. Based on the investigation of reaction pathways, it is important to emphasize that both hydrogenation and hydroelimination of formaldehyde (hydrodeformylation) occur in the vapour phase reaction. 相似文献
4.
Lijun Gu Ding Ma Prof. Dr. Songdong Yao Xiumei Liu Xiuwen Han Prof. Wenjie Shen Prof. Dr. Xinhe Bao Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(48):13449-13455
A facile method has been developed for the fabrication of porous silicon carbide (SiC) by means of sintering a mixture of SiC powder and carbon pellets at a relatively lower temperature, that is, 1450 °C, in air. The pore density and the total pore volume of the resulting porous SiC could be tuned by changing the initial SiC/C weight ratio. The structure evolution and the associated property changes during the preparation were examined through X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, 29Si magic‐angle spinning (MAS) NMR spectroscopy, and mercury‐intrusion porosimetry analyses. Silica and SiOxCy ceramics formed in situ during the calcination process acted as binders of the porous SiC grains. The porous SiC can be used as a host for the growth of ZSM‐5 zeolite crystals to form the ZSM‐5/porous‐SiC composite material. After loading another catalytic active component of molybdenum, a novel catalytic material, Mo‐ZSM‐5/porous‐SiC, was obtained, which exhibited improved catalytic activity in the methane dehydroaromatization reaction. 相似文献
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Prof. Dr. William J. Kerr Richard J. Mudd Dr. Jack A. Brown 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4738-4742
The directed chemoselective hydrogenation of olefins has been established by using iridium(I) catalysts, which feature a tuned NHC/phosphine ligand combination. This selective reduction process has been demonstrated in a wide array of solvents, including more environmentally acceptable media, also allowing further refinement of hydrogenation selectivity. 相似文献
6.
NHC‐Stabilized Iridium Nanoparticles as Catalysts in Hydrogen Isotope Exchange Reactions of Anilines
Mgane Valero Donia Bouzouita Alberto Palazzolo Jens Atzrodt Christophe Dugave Simon Tricard Sophie Feuillastre Grgory Pieters Bruno Chaudret Volker Derdau 《Angewandte Chemie (International ed. in English)》2020,59(9):3517-3522
The preparation of N‐heterocyclic carbene‐stabilized iridium nanoparticles and their application in hydrogen isotope exchange reactions is reported. These air‐stable and easy‐to‐handle iridium nanoparticles showed a unique catalytic activity, allowing selective and efficient hydrogen isotope incorporation on anilines using D2 or T2 as isotopic source. The usefulness of this transformation has been demonstrated by the deuterium and tritium labeling of diverse complex pharmaceuticals. 相似文献
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Dr. Xu Quan Dr. Sutthichat Kerdphon Bram B. C. Peters Dr. Janjira Rujirawanich Dr. Suppachai Krajangsri Dr. Jira Jongcharoenkamol Prof. Pher G. Andersson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(58):13311-13316
Novel bidentate N-heterocyclic carbene-phosphine iridium complexes have been synthesized and evaluated in the hydrogenation of ketones. Reported catalytic systems require base additives and, if excluded, need elevated temperature or high pressure of hydrogen gas to achieve satisfactory reactivity. The developed catalysts showed extremely high reactivity and good enantioselectivity under base-free and mild conditions. In the presence of 1 mol % catalyst under 1 bar hydrogen pressure at room temperature, hydrogenation was complete in 30 minutes giving up to 96 % ee. Again, this high reactivity was achieved in additive-free conditions. Mechanistic experiments demonstrated that balloon pressure of hydrogen was sufficient to form the activate species by reducing and eliminating the 1,5-cyclooctadiene ligand. The pre-activated catalyst was able to hydrogenate acetophenone with 89 % conversion in 5 min. 相似文献
8.
Effective and Selective Catalysts for Cinnamaldehyde Hydrogenation: Hydrophobic Hybrids of Metal–Organic Frameworks,Metal Nanoparticles,and Micro‐ and Mesoporous Polymers 下载免费PDF全文
Kuo Yuan Tianqun Song Dr. Dawei Wang Dr. Xiaotao Zhang Xiong Gao Dr. Ye Zou Prof. Dr. Huanli Dong Prof. Dr. Zhiyong Tang Prof. Dr. Wenping Hu 《Angewandte Chemie (International ed. in English)》2018,57(20):5708-5713
Metal–organic frameworks (MOFs) as selectivity regulators for catalytic reactions have attracted much attention, especially MOFs and metal nanoparticle (NP) shelled structures, e.g., MOFs@NPs@MOFs. Nevertheless, making hydrophilic MOF shells for gathering hydrophobic reactants is challenging. Described here is a new and viable approach employing conjugated micro‐ and mesoporous polymers with iron(III) porphyrin (FeP‐CMPs) as a new shell to fabricate MIL‐101@Pt@FeP‐CMP. It is not only hydrophobic and porous for enriching reactants, but also possesses iron sites to activate C=O bonds, thereby regulating the selectivity for cinnamyl alcohol in the hydrogenation of cinnamaldehyde. Interestingly, MIL‐101@Pt@FeP‐CMPsponge can achieve a high turnover frequency ( 1516.1 h?1), with 97.3 % selectivity for cinnamyl alcohol at 97.6 % conversion. 相似文献
9.
Highly efficient catalysts play an important role in the effective use of biomass oil to produce clean fuel. In this work, pure-phase Ni−Mo bimetallic nitrides (Ni2Mo3N and Ni3Mo3N) with different stoichiometric ratios are prepared by temperature-programmed nitridation of the metal oxide precursors in ammonia, which are investigated in the hydrodeoxygenation of methyl palmitate in the fixed-bed reactor at moderate conditions. The physical and chemical properties of catalysts were evaluated by H2-TPR, XRD, SEM, TEM, XPS, and CO chemisorption. The Ni2Mo3N catalyst presents the best methyl palmitate hydrogenation activity (con.%=95.4 %) and the maximum hexadecane selectivity (95.0 %), which is obviously higher than those of Ni3Mo3N and Mo2N catalysts. By introducing transition metal Ni into the Mo2N lattice to form nickel-molybdenum bimetallic nitride, the lattice structure and electronic structure of the Mo active center have been changed, which greatly enhances the hydrodeoxygenation performances for the transformation of biomass oil to clean fuel. 相似文献
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Jincan Kang Shuli Zhang Qinghong Zhang Dr. Ye Wang Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(14):2565-2568
Diesel do nicely : The title system is a highly selective Fischer–Tropsch catalyst for the production of C10–C20 hydrocarbons (diesel fuel). The C10–C20 selectivity strongly depends on the mean size of the Ru nanoparticles. Nanoparticles with a mean size around 7 nm exhibit the highest C10–C20 selectivity (ca. 65 %) and a relatively higher turnover frequency for CO conversion.
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《化学:亚洲杂志》2017,12(3):355-360
A series of NHC–iridium coordination polymers have proven to be robust, efficient and recyclable solid molecular catalysts toward the hydrogenation of biomass levulinic acid (LA) to γ‐valerolactone. Along with quantitative yields attained at 0.01 mol % catalyst loading under 50 atm of H2, the solid molecular catalyst was readily recovered and reused for 12 runs without obvious loss of the selectivity and activity. Remarkably, up to 1.2×105 TON, an unprecedented value could be achieved in this important transformation. In addition, a number of LA homologues, analogues and derivatives were well tolerated to deliver various intriguing and functional lactones in good to excellent yields, which further confirmed the feasibility of the solid molecular catalysts. 相似文献
15.
Lei Shi Xingwang Wang Dr. Christian A. Sandoval Prof. Dr. Zheng Wang Prof. Dr. Hongji Li Jiang Wu Liting Yu Kuiling Ding Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(38):9855-9867
Well‐designed, self‐assembled, metal–organic frameworks were constructed by simple mixing of multitopic MonoPhos‐based ligands ( 3 ; MonoPhos=chiral, monodentate phosphoramidites based on the 1,1′‐bi‐2‐naphthol platform) and [Rh(cod)2]BF4 (cod=cycloocta‐1,5‐diene). This self‐supporting strategy allowed for simple and efficient catalyst immobilization without the use of extra added support, giving well‐characterized, insoluble (in toluene) polymeric materials ( 4 ). The resulting self‐supported catalysts ( 4 ) showed outstanding catalytic performance for the asymmetric hydrogenation of a number of α‐dehydroamino acids ( 5 ) and 2‐aryl enamides ( 7 ) with enantiomeric excess (ee) ranges of 94–98 % and 90–98 %, respectively. The linker moiety in 4 influenced the reactivity significantly, albeit with slight impact on the enantioselectivity. Acquisition of reaction profiles under steady‐state conditions showed 4 h and 4 i to have the highest reactivity (turnover frequency (TOF)=95 and 97 h?1 at 2 atm, respectively), whereas appropriate substrate/catalyst matching was needed for optimum chiral induction. The former was recycled 10 times without loss in ee (95–96 %), although a drop in TOF of approximately 20 % per cycle was observed. The estimation of effective catalytic sites in self‐supported catalyst 4 e was also carried out by isolation and hydrogenation of catalyst–substrate complex, showing about 37 % of the RhI centers in the self‐supported catalyst 4 e are accessible to substrate 5 c in the catalysis. A continuous flow reaction system using an activated C/ 4 h mixture as stationary‐phase catalyst for the asymmetric hydrogenation of 5 b was developed and run continuously for a total of 144 h with >99 % conversion and 96–97 % enantioselectivity. The total Rh leaching in the product solution is 1.7 % of that in original catalyst 4 h . 相似文献
16.
Octahedral Chiral‐at‐Metal Iridium Catalysts: Versatile Chiral Lewis Acids for Asymmetric Conjugate Additions 下载免费PDF全文
Xiaodong Shen Haohua Huo Chuanyong Wang Bo Zhang Dr. Klaus Harms Prof. Dr. Eric Meggers 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9720-9726
Octahedral iridium(III) complexes containing two bidentate cyclometalating 5‐tert‐butyl‐2‐phenylbenzoxazole ( IrO ) or 5‐tert‐butyl‐2‐phenylbenzothiazole ( IrS ) ligands in addition to two labile acetonitrile ligands are demonstrated to constitute a highly versatile class of asymmetric Lewis acid catalysts. These complexes feature the metal center as the exclusive source of chirality and serve as effective asymmetric catalysts (0.5–5.0 mol % catalyst loading) for a variety of reactions with α,β‐unsaturated carbonyl compounds, namely Friedel–Crafts alkylations (94–99 % ee), Michael additions with CH‐acidic compounds (81–97 % ee), and a variety of cycloadditions (92–99 % ee with high d.r.). Mechanistic investigations and crystal structures of an iridium‐coordinated substrates and iridium‐coordinated products are consistent with a mechanistic picture in which the α,β‐unsaturated carbonyl compounds are activated by two‐point binding (bidentate coordination) to the chiral Lewis acid. 相似文献
17.
Tailor‐Made Ruthenium‐Triphos Catalysts for the Selective Homogeneous Hydrogenation of Lactams 下载免费PDF全文
Markus Meuresch Stefan Westhues Prof. Dr. Walter Leitner Prof. Dr. Jürgen Klankermayer 《Angewandte Chemie (International ed. in English)》2016,55(4):1392-1395
The development of a tailored tridentate ligand enabled the synthesis of a molecular ruthenium‐triphos catalyst, eliminating dimerization as the major deactivation pathway. The novel catalyst design showed strongly increased performance and facilitated the hydrogenation of highly challenging lactam substrates with unprecedented activity and selectivity. 相似文献
18.
Site‐Selective CH Borylation of Quinolines at the C8 Position Catalyzed by a Silica‐Supported Phosphane–Iridium System 下载免费PDF全文
Shota Konishi Dr. Soichiro Kawamorita Dr. Tomohiro Iwai Prof. Patrick G. Steel Prof. Dr. Todd B. Marder Prof. Dr. Masaya Sawamura 《化学:亚洲杂志》2014,9(2):434-438
Site‐selective C? H borylation of quinoline derivatives at the C8 position has been achieved by using a heterogeneous Ir catalyst system based on a silica‐supported cage‐type monophosphane ligand SMAP. The efficient synthesis of a corticotropin‐releasing factor1 (CRF1) receptor antagonist based on a late‐stage C? H borylation strategy demonstrates the utility of the C8 borylation reaction. 相似文献
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In Situ Observation of Hydrogen‐Induced Surface Faceting for Palladium–Copper Nanocrystals at Atmospheric Pressure 下载免费PDF全文
Ying Jiang Hengbo Li Zhemin Wu Wenying Ye Prof. Hui Zhang Prof. Yong Wang Dr. Chenghua Sun Prof. Ze Zhang 《Angewandte Chemie (International ed. in English)》2016,55(40):12427-12430
Nanocrystal (NC) morphology, which decides the number of active sites and catalytic efficiency, is strongly determined by the gases involved in synthesis, treatment, and reaction. Myriad investigations have been performed to understand the morphological response to the involved gases. However, most prior work is limited to low pressures, which is far beyond realistic conditions. A dynamic morphological evolution of palladium–copper (PdCu) NC within a nanoreactor is reported, with atmospheric pressure hydrogen at the atomic scale. In situ transmission electron microscopy (TEM) videos reveal that spherical PdCu particles transform into truncated cubes at high hydrogen pressure. First principles calculations demonstrate that the surface energies decline with hydrogen pressure, with a new order of γH‐001<γH‐110<γH‐111 at 1 bar. A comprehensive Wulff construction based on the corrected surface energies is perfectly consistent with the experiments. The work provides a microscopic insight into NC behaviors at realistic gas pressure and is promising for the shaping of nanocatalysts by gas‐assisted treatments. 相似文献
20.
A Mild Dihydrobenzooxaphosphole Oxazoline/Iridium Catalytic System for Asymmetric Hydrogenation of Unfunctionalized Dialins 下载免费PDF全文
Dr. Bo Qu Dr. Lalith P. Samankumara Dr. Shengli Ma Dr. Keith R. Fandrick Dr. Jean‐Nicolas Desrosiers Dr. Sonia Rodriguez Dr. Zhibin Li Dr. Nizar Haddad Dr. Zhengxu S. Han Keith McKellop Scott Pennino Dr. Nelu Grinberg Dr. Nina C. Gonnella Dr. Jinhua J. Song Dr. Chris H. Senanayake 《Angewandte Chemie (International ed. in English)》2014,53(52):14428-14432
Air‐stable P‐chiral dihydrobenzooxaphosphole oxazoline ligands were designed and synthesized. When they were used in the iridium‐catalyzed asymmetric hydrogenation of unfunctionalized 1‐aryl‐3,4‐dihydronaphthalenes under one atmosphere pressure of H2, up to 99:1 e.r. was obtained. High enantioselectivities were also observed in the reduction of the exocyclic imine derivatives of 1‐tetralones. 相似文献