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1.
Redox Properties of CeO2 at Low Temperature: The Direct Synthesis of Imines from Alcohol and Amine
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Dr. Masazumi Tamura Prof. Dr. Keiichi Tomishige 《Angewandte Chemie (International ed. in English)》2015,54(3):864-867
We disclosed the redox properties of CeO2 in organic reactions at low temperature of 303 K. CeO2 works as the most effective heterogeneous catalyst for imine formation from benzyl alcohol and aniline at 303 K among various metal oxides and showed more than 38‐fold higher activity than other simple metal oxides. CeO2 is applicable to the reaction of various alcohols and amines and gives high yields (80–98 %) and high selectivities (89–>99 %). Kinetic measurements, MS, and FTIR analyses demonstrated that the high activity of CeO2 is a result of reactive oxygen species at the redox sites on CeO2. This discovery can help to create a new field in metal oxide catalysis. 相似文献
2.
探讨负载型金属氧化物催化剂的表面组分与载体之间的相互作用, 有助于理解相关催化剂的催化作用本质. 近年来, 我们对单组分CuO以及双组分CuO-Mn2O3, CuO-CoO等金属氧化物在γ-Al2O3载体表面的分散行为和存在状态, 及其物理化学性质和催化性能(CO+O2和NO+CO模型反应)进行了研究. 结果表明, 这些金属氧化物在γ-Al2O3载体表面的分散行为和所得负载型催化剂样品的一些物理化学性质及其催化性能均可参照“嵌入模型”来解释. 在此基础上, 我们讨论了这些样品的“组成-结构-性质”间的关系, 并针对表面负载双组分金属氧化物样品提出了表面协同氧空位参与的NO+CO反应机理. 相似文献
3.
Arihiro Kanazawa Shokyoku Kanaoka Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2010,48(4):916-926
Cationic polymerization of isobutyl vinyl ether (IBVE) was examined using a variety of metal oxides in conjunction with IBVE–HCl adduct as a cationogen in toluene at 0 °C. Iron oxides (α‐Fe2O3, γ‐Fe2O3, and Fe3O4) induced living polymerization in the presence of an added base, ethyl acetate or 1,4‐dioxane, to give polymers with very narrow molecular weight distributions (MWDs). Conversely, with other metal oxides such as Ga2O3, In2O3, ZnO, Co3O4, and Bi2O3, polymers with bimodal MWDs, including long‐lived species along with uncontrolled higher molecular weight portions, were produced in the presence of an added base. A small amount of nBu4NCl or 2,6‐di‐tert‐butylpyridine (DTBP) suppressed the uncontrolled portion to induce controlled reactions with Ga2O3, In2O3, and ZnO. The roles of these reagents are discussed in terms of the nature of the active sites of the catalyst surface and the polymerization mechanisms. In addition, the reusability of the catalyst, the effect of stirring before and during polymerization, and the estimation of the number of active sites are also described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 916–926, 2010 相似文献
4.
Hajime Kato Masaki Nakashima Yoshihiko Mori Toshiaki Mori Tadashi Hattori Yuichi Murakami 《Research on Chemical Intermediates》1995,21(2):115-126
In CO hydrogenation over Rh/SiO2 catalysts, the effect of additive metal oxides on C-O bond dissociation was studied by using pulse surface reaction rate
analysis (PSRA). The addition of oxides of Al, Ti, Cr, V, and Mn resulted in an increase in the rate constant for the dissociation
according to this sequence, while the oxides of Cu, Zn, and Ag added decreased the rate constant to almost the same extent.
In contrast to these metal oxides, MoO3 and WO3 did not change the dissociation activity. CO adsorption measurement indicated that all of the added metal oxides covered
a considerable portion of the Rh metal surface, although the efficiency of covering was different from one metal oxide to
another. Covering the Rh metal surface with an added metal oxide should decrease the rate constant of C-O bond dissociation,
because ensemble sites, consisting of a group of surface Rh atoms and considered necessary for the dissociation, were destroyed.
The suppression effect resulted from the destruction of the ensemble sites by adding the oxides of Cu, Zn, and Ag. For other
metal oxides, temperature-programmed reduction (TPR) or O2 uptake measurement revealed that the added oxides, especially those existing on the Rh metal surface, were in a partially
reduced state under reaction conditions. Owing to its high affinity for an oxygen atom, the cation in a partially reduced
state participated in the reaction in such a way that the oxygen end of adsorbed CO species was bound to the cation so as
to dissociate the C-O bond, which resulted in promotion of the dissociation. The observed promotion was explained in terms
of the enhancement owing to the high affinity sufficient to overcome the suppression caused by destroying ensemble sites.
Lack of the promotion effect of MoO3 and WO3 might result from a balance between promotion due to the high affinity of the partially reduced Mo or W and suppression caused
by destroying ensemble sites. Excellent correlation was observed between the intrinsic activity increase, from which the suppression
effect was excluded, and the heat of formation of metal oxide including MoO3 and WO3. Since the heat of formation of metal oxide is considered to be a measure of the affinity, this correlation supports the
idea that the high affinity of additive cations for an oxygen atom is of primary importance in the promotion of C-O bond dissociation
in CO hydrogenation. 相似文献
5.
M. Esmaeilpour 《Green Chemistry Letters and Reviews》2014,7(3):301-308
Fe3O4@SiO2/Schiff base complex of metal ions catalyzed the reaction between phenylene-1,2-diamines and 1,2-diketones to produce quinoxalines in aqueous media at room temperature. This eco-friendly method provides several advantages such as mild reaction conditions, good to excellent yields, simple work-up, and nanocatalyst stability. Also, nanocatalyst can be simply recovered by a magnetic field and reused for at least five successive reactions. 相似文献
6.
Dr. Kelly L. Materna Prof. Leif Hammarström 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16966-16977
Heterogenized photoredox catalysts provide a path for sustainable chemical synthesis using highly tunable, reusable constructs. Here, heterogenized iridium complexes as photoredox catalysts were assembled via covalent attachment to metal oxide surfaces (ITO, ZrO2, Al2O3) in thin film or nanopowder constructs. The goal was to understand which materials provided the most promising constructs for catalysis. To do this, reductive dehalogenation of bromoacetophenone to acetophenone was studied as a test reaction for system optimization. All catalyst constructs produced acetophenone with high conversions and yields with the fastest reactions complete in fifteen minutes using Al2O3 supports. The nanopowder catalysts resulted in faster and more efficient catalysis, while the thin film catalysts were more robust and easily reused. Importantly, the thin film constructs show promise for future photoelectrochemical and electrochemical photoredox setups. Finally, all catalysts were reusable 2–3 times, performing at least 1000 turnovers (Al2O3), demonstrating that heterogenized catalysts are a sustainable catalyst alternative. 相似文献
7.
Dr. Soichi Kikkawa Yu Fujiki Vorakit Chudatemiya Hiroki Nagakari Kazuki Shibusawa Dr. Jun Hirayama Prof. Naoki Nakatani Prof. Seiji Yamazoe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(17):e202401526
Here, doubly protonated Lindqvist-type niobium oxide cluster [H2(Nb6O19)]6–, fabricated by microwave-assisted hydrothermal synthesis, exhibited superbase catalysis for Knoevenagel and crossed aldol condensation reactions accompanied by activating C−H bond with pKa >26 and proton abstraction from a base indicator with pKa=26.5. Surprisingly, [H2(Nb6O19)]6− exhibited water-tolerant superbase properties for Knoevenagel and crossed aldol condensation reactions in the presence of water, although it is well known that the strong basicity of metal oxides and organic superbase is typically lost by the adsorption of water. Density functional theory calculation revealed that the basic surface oxygens that share the corner of NbO6 units in [H2(Nb6O19)]8− maintained the negative charges even after proton adsorption. This proton capacity and the presence of un-protonated basic sites led to the water tolerance of the superbase catalysis. 相似文献
8.
Yulu Yang Mingguang Wu Xingwang Zhu Hui Xu Si Ma Yongfeng Zhi Hong Xia Xiaoming Liu Jun Pan Jie-Yinn Tang Siang-Piao Chai Leonardo Palmisano Francesco Parrino Junli Liu Jianzhong Ma Ze-Lin Wang Ling Tan Yu-Fei Zhao Jianmin Ma 《中国化学快报》2019,30(12):2065-2088
Environmental catalysis has drawn a great deal of attention due to its clean ways to produce useful chemicals or carry out some chemical processes. Photocatalysis and electrocatalysis play important roles in these fields. They can decompose and remove organic pollutants from the aqueous environment, and prepare some fine chemicals. Moreover, they also can carry out some important reactions, such as O2 reduction reaction (ORR), O2 evolution reaction (OER), H2 evolution reaction (HER), CO2 reduction reaction (CO2RR), and N2 fixation (NRR). For catalytic reactions, it is the key to develop high-performance catalysts to meet the demand for targeted reactions. In recent years, two-dimensional (2D) materials have attracted great interest in environmental catalysis due to their unique layered structures, which offer us to make use of their electronic and structural characteristics. Great progress has been made so far, including graphene, black phosphorus, oxides, layered double hydroxides (LDHs), chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks (MOFs), covalent organic frameworks (COFs), and others. This content drives us to invite many famous groups in these fields to write the roadmap on two-dimensional nanomaterials for environmental catalysis. We hope that this roadmap can give the useful guidance to researchers in future researches, and provide the research directions. 相似文献
9.
Seung Tae Hong Dal Ryung Park Seung-Joon Yoo Jae-Duck Kim Hyung Sang Park 《Research on Chemical Intermediates》2006,32(9):857-870
The active phase of the NiMo/Al2O3 catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the
effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their
sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which
are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of
Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then
induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high
Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts;
one is that Mo should be located at the tetrahedral coordination on Al2O3 in high dispersion (Mo/Al2O3) and the other is that the Ni species should be supported on MoAl2O4 to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation. 相似文献
10.
Yuma Kato Muneaki Yamamoto Masato Akatsuka Ryota Ito Akiyo Ozawa Yu Kawaguchi Tetsuo Tanabe Tomoko Yoshida 《Surface and interface analysis : SIA》2019,51(1):40-45
Various metal oxides with 0.1 wt% Ag loaded as a cocatalyst were prepared by an impregnation method and examined their photocatalytic activity for CO2 reduction with water. Among all the prepared Ag-loaded metal oxides, Ga2O3, ZrO2, Y2O3, MgO, and La2O3 showed activities for CO and H2 productions under ultraviolet light irradiation. Thus, metal oxides involving metal cations with closed shell electronic structures such as d0, d10, and s0 had the potential for CO2 reduction with water. In situ Fourier transform infrared measurement revealed that the photocatalytic activity and selectivity for CO production are controlled by the amount and chemical states of CO2 adsorbed on the catalyst surface and by the surface basicity, as summarized as follows: Ag/ZrO2 enhanced H2 production rather than CO production due to very little CO2 adsorption. Ag/Ga2O3 exhibited the highest activity for CO production, because adsorbed monodentate bicarbonate was effectively converted to bidentate formate being the reaction intermediates for CO production owing to its weak surface basicity. Ag/La2O3, Ag/Y2O3, and Ag/MgO having both weak and strong basic sites adsorbed larger amount of carbonate species including their ions and suppressed H2 production. However, the adsorbed carbonate species were hardly converted to the bidentate formate. 相似文献
11.
This paper reviews acid–base bifunctional catalysis and surface properties (morphology, composition, specific area, acidity/basicity, site density) on TiO2–ZrO2 (abbreviated as TZ) mixed oxides. The phase change from crystalline single oxides (TiO2 and ZrO2) to amorphous TZ mixed oxide results in decreasing grain size and site density, increasing surface area, acid/base amount and strength, and better activity/selectivity. Different acid–base bifunctional mechanisms (concerted, go-together, stepwise) were proposed to interpret the reaction behavior of various reactions (esterification, dehydration, dehydrogenation, isomerization, dehydrocyclization) over the acid–base bifunctional TZ catalysts. 相似文献
12.
The design and fabrication of solid nanomaterials are the key issues in heterogeneous catalysis to achieve desired performance.Traditionally,the main theme is to reduce the size of the catalyst particles as small as possible for maximizing the number of active sites.In recent years,the rapid advancement in materials science has enabled us to fabricate catalyst particles with tunable morphology.Consequently,both size modulation and morphology control of the catalyst particles can be achieved independently or synergistically to optimize their catalytic properties.In particular,morphology control of solid catalyst particles at the nanometer level can selectively expose the reactive crystal facets,and thus drastically promote their catalytic performance.In this review,we summarize our recent work on the morphology impact of Co3O4,CeO2 and Fe2O3 nanomaterials in catalytic reactions,together with related literature on morphology-dependent nanocatalysis of metal oxides,to demonstrate the importance of tuning the shape of oxide-nanocatalysts for prompting their activity,selectivity and stability,which is a rapidly growing topic in heterogeneous catalysis.The fundamental understanding of the active sites in morphology-tunable oxides that are enclosed by reactive crystal facets is expected to direct the development of highly efficient nanocatalysts. 相似文献
13.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):10895-10900
Indium oxide catalyzes acetylene hydrogenation with high selectivity to ethylene (>85 %); even with a large excess of the alkene. In situ characterization reveals the formation of oxygen vacancies under reaction conditions, while an in depth theoretical analysis links the surface reduction with the creation of well‐defined vacancies and surrounding In3O5 ensembles, which are considered responsible for this outstanding catalytic function. This behavior, which differs from that of other common reducible oxides, originates from the presence of four crystallographically inequivalent oxygen sites in the indium oxide surface. These resulting ensembles are 1) stable against deactivation, 2) homogeneously and densely distributed, and 3) spatially isolated and confined against transport; thereby broadening the scope of oxides in hydrogenation catalysis. 相似文献
14.
Surface structure and reaction performances of highly dispersed and supported bimetallic catalysts 总被引:1,自引:0,他引:1
Surface structures of Pt-Sn and Pt-Fe bimetallic catalysts have been investigated by means of Mssbauer spectroscopy, Pt-L_Ⅲ-edge EXAFS and H_2-adsorption. The results showed that the second component, such as Sn or Fe, remained in the oxidative state and dispersed on the γ-Al_2O_3 surface after reduction, while Pt was completely reduced to the metallic state and dispersed on either the metal oxide surface or the γ-Al_2O_3 surface. By correlating the distribution of Pt species on different surfaces with the reaction and adsorption performances, it is proposed that two kinds of active Pt species existed on the surfaces of both catalysts, named M_1 sites and M_2 sites. M_1 sites are the sites in which Pt directly anchored on the γ-Al_2O_3 surface, while M_2 sites are those in which Pt anchored on the metal oxide surface. M_1 sites are favorable for low temperature H_2 adsorption, and responsible for the hydrogenolysis reaction and carbon deposition, while M_2 sites which adsorb more H_2 at higher tem 相似文献
15.
Metal oxides are stable and highly durable catalysts for the selective catalytic reduction (SCR) of NO by hydrocarbons and potential candidates for practical use. This review focuses on the development as well as the fundamental understanding of metal oxide based catalysts for selective reduction of NO by hydrocarbons. Our studies on the SCR-deNOx properties of Ga2O3/Al2O3, Cu-Al2O3, and Ag-Al2O3 catalysts are presented and it is attempted to demonstrate the advantages of this type of catalysts. On the basis of several spectroscopic characterizations, the effect of important factors, such as dispersion, coordination, and the electronic states of the metal cation, on the intrinsic catalytic activity are quite well clarified. From the in situ FTIR results, the reaction mechanism is understood in terms of formation and reaction of surface molecules. The structural and kinetic information obtained at the molecular level provides a useful strategy for designing better deNOx catalysts using metal oxides. 相似文献
16.
Catalytic transfer hydrogenation of 2-butanone with 2-propanol was studied in gas phase over a series of oxides of different
acid-base properties. Although the basic oxides (MgO, La2O3) gave high initial conversions, these oxides underwent deactivation during the reaction. This deactivation could be partially
prevented by a previous treatment with chloroform of the oxide. The amphoteric oxides (TiO2, ZrO2, Al2O3) were also active in this reaction. Increasing the acidic character of the catalyst (Nb2O5, WO3) led to a pronounced dehydration of 2-propanol. The results obtained over a series of rare earth oxides (La2O3, Sm2O3, Gd2O3, Dy2O3, Er2O3) revealed that beside the role of basic and acid sites a correlation seems to exist between the number of unpaired electrons
of the metal ion and the catalytic activity, indicating the role of one electron donor sites. 相似文献
17.
Metal oxides are stable and highly durable catalysts for the selective catalytic reduction (SCR) of NO by hydrocarbons and potential candidates for practical use. This review focuses on the development as well as the fundamental understanding of metal oxide based catalysts for selective reduction of NO by hydrocarbons. Our studies on the SCR-deNOx properties of Ga2O3/Al2O3, Cu-Al2O3, and Ag-Al2O3 catalysts are presented and it is attempted to demonstrate the advantages of this type of catalysts. On the basis of several spectroscopic characterizations, the effect of important factors, such as dispersion, coordination, and the electronic states of the metal cation, on the intrinsic catalytic activity are quite well clarified. From the in situ FTIR results, the reaction mechanism is understood in terms of formation and reaction of surface molecules. The structural and kinetic information obtained at the molecular level provides a useful strategy for designing better deNOx catalysts using metal oxides. 相似文献
18.
LIU Chi-Biao ZHAO Zhen YANG Xiang-Guang YE Xing-Kai WU Yue Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin China 《中国化学》1996,14(6):516-524
Superconductor mixed oxides were often used as catalysts at higher temperature in gas phase oxidations, and considered not suitable for lower temperature reactions in the liquid-solid phase; here the catalysis of YBa2Cu3O7+x and Y2BaCuO5+x in the phenol hydroxylation at lower temperature with H2O2 as oxygen donor was studied, and found that the superconductor YBaCu3O7±x has no catalytic activity for phenol hydroxylation, but Y2BaCuO5±x does, even has better catalytic activity and stability than most previously reported ones. With the studies of catalysis of other simple metal oxides and perovskite-like mixed oxides, a radical substitution mechanism is proposed and the experimental facts are explained clearly, and draw a conclusion that the perovskite-like mixed oxides with (AO)(ABO3) and (AO)2(ABO3) structure have better catalytic activity than the simple per-ovskite oxides with (ABO3)3 structure alone, and (AO) structure unit is the key for the mixed oxides to have the phenol hydroxylation activity. 相似文献
19.
Kavita Kumar Laetitia Dubau Michel Mermoux Jingkun Li Andrea Zitolo Jaysen Nelayah Frdric Jaouen Frdric Maillard 《Angewandte Chemie (International ed. in English)》2020,59(8):3235-3243
Fe‐N‐C catalysts containing atomic FeNx sites are promising candidates as precious‐metal‐free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The durability of Fe‐N‐C catalysts in fuel cells has been extensively studied using accelerated stress tests (AST). Herein we reveal stronger degradation of the Fe‐N‐C structure and four‐times higher ORR activity loss when performing load cycling AST in O2‐ vs. Ar‐saturated pH 1 electrolyte. Raman spectroscopy results show carbon corrosion after AST in O2, even when cycling at low potentials, while no corrosion occurred after any load cycling AST in Ar. The load‐cycling AST in O2 leads to loss of a significant fraction of FeNx sites, as shown by energy dispersive X‐ray spectroscopy analyses, and to the formation of Fe oxides. The results support that the unexpected carbon corrosion occurring at such low potential in the presence of O2 is due to reactive oxygen species produced between H2O2 and Fe sites via Fenton reactions. 相似文献
20.
Guanghui Sun Yuekang Jin Zhengming Wang Hong Xu Peng Chai Weixin Huang 《中国化学快报》2018,29(12):1883-1887
A complete fundamental understanding of propylene oxidation with molecular O2 on Au surface is achieved, in which site-and surface species-dependent reaction behaviors are revealed. 相似文献