Journal of Physical Chemistry C
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2014
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IF 4.835
Fang Niu,Shuiqing Li,Yichen Zong,Qiang Yao
A controlled one-step synthesis of titania-supported palladium (Pd/TiO2) nanoparticles is demonstrated by using a premixed stagnation swirl flame with an ultrafine spray feeding system. The new method produces well-dispersed palladium clusters on the surface of TiO2 particle. The low-temperature methane catalytic oxidation indicates that the flame-made Pd/TiO2 possesses activity apparently higher than that of the impregnated one under the same Pd loading. For the first time, we observe a special pinched hysteresis loop of catalytic activity of Pd/TiO2 nanoparticles from the curves of CH4 conversion versus temperature during heating–cooling cycles. Thermal stability analysis confirms the complex coexistence and transformation of metallic Pd and PdO in Pd/TiO2 particles. Further morphological characterization reveals the oxidation rate is controlled by the metallic Pd content on the particle surface, whereas the deactivation of the catalysts is mainly due to the Pd dispersion decrement. The competition between the Pd dispersion decrement and the PdO reduction at the surface may result in the pinched hysteresis loop of Pd/TiO2 catalysts during low-temperature methane combustion.
研究领域:
催化化学
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纳米材料科学
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环境催化
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能源化学
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表面科学
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DOI
高影响因子
Particuology
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2018
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IF 2.785
Nafeng Wang,Fang Niu,Shuhao Wang,Yun Huang
A nanocatalyst composed of 10 wt% Pd supported on TiO 2 was synthesized using one-step flame spray pyrolysis with a highly-quenched premixed stagnation flame. The as-prepared nanoparticles , having a mean diameter of approximately 10 nm, were then subjected to isothermal oxidation and reduction in a fixed bed reactor. The potential roles of Pd and PdO as well as possible synergistic effects between these two active species were explored during methane conversion. The lowest light-off temperature T 20 was obtained at a Pd ratio of 53% and this result can be reasonably explained based on a surface Pd–PdO site pair mechanism. Additionally, differences in the hysteresis behavior during methane oxidation were noted throughout a heating–cooling cycle over the temperature range of 200–600 °C, such that the degree of hysteresis was strongly correlated with the Pd ratio.
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高影响因子
JOURNAL OF CATALYSIS
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2021
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IF 7.92
Jing Zhang,Weiqi Liao,Hao Zheng,Yunshang Zhang,Lebing Xia,Bo-Tao Teng,Ji-Qing Lu,Weixin Huang,Zhenhua Zhang
Pd supported on different anatase TiO 2 nanocrystals predominantly exposing either {1 0 0}, {1 0 1}, or {0 0 1} facets were tested for CO 2 hydrogenation into formate. Remarkable morphology-dependent catalysis was observed. Compared to 2%Pd/TiO 2 {1 0 1} and 2%Pd/TiO 2 {0 0 1} catalysts, 2%Pd/TiO 2 {1 0 0} is highly active and stable, affording an unprecedented turnover frequency of ca. 1369 h −1 and keeping stable after 6 cycles at 313 K. This can be associated with, on the one hand, higher density of moderate basic site and relatively more Pd(0) species over 2%Pd/TiO 2 {1 0 0} contribute to the activations of CO 2 and H 2 , respectively, favorable for the activity; On the other hand, higher oxygen vacancy concentrations in the TiO 2 {1 0 0} promote the Pd-TiO 2 interactions and result in the formation and stability of flat Pd particles over 2%Pd/TiO 2 {1 0 0}, beneficial to the stability. These results highlight the importance of oxide morphology in formate formation and open up possibilities of oxide morphology engineering for developing efficient Pd-based catalysts for CO 2 hydrogenation.
研究领域:
化学工程
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催化科学
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DOI
高影响因子
RARE METALS
·
2026
·Vol. 45
·期 10
·e70671
·
IF 12.1
Zhidan Wang,Rui Li,Yawen Wang,Yunfang Wang,Caimei Fan,Jianxin Liu,Shan Gao,Jiancheng Wang
en This link goes to a English section zh This link goes to a Chinese section Photocatalytic acetylene (C 2 H 2 ) semihydrogenation is a green route for ethylene (C 2 H 4 ) production, yet the activity–selectivity trade-off caused by imbalanced adsorption/activation of reactants and products remains a core challenge. Herein, we realize precise regulation of Pd oxidation states (Pd 0 , Pd δ + , and Pd 2+ ) on anatase TiO 2 nanocubes via a mild reduction strategy, fabricating a Pd δ + /TiO 2 photocatalyst with intermediate valence of Pd sites. Systematic characterizations and theoretical calculations reveal that Pd δ + optimizes the d-π/d-π* orbital interactions between Pd and C 2 H 2 /C 2 H 4 , achieving a moderate adsorption strength that balances efficient C 2 H 2 activation and rapid C 2 H 4 desorption. Pd 0 causes overadsorption/overhydrogenation, whereas Pd 2+ leads to weak substrate activation. Consequently, Pd δ + /TiO 2 achieves nearly 100% C 2 H 2 conversion and ∼90% C 2 H 4 selectivity, with a record-high turnover number (TON) of ∼4.1 × 10 4 and excellent cycling stability. This work clarifies the electronic mechanism of Pd valence engineering in carrier dynamics and modulating orbital hybridization, providing a new strategy for the rational design of C 2 H 2 semihydrogenation photocatalysts. 摘要 en This link goes to a English section zh This link goes to a Chinese section 光催化乙炔(C 2 H 2 )半加氢是一种制备乙烯(C 2 H 4 )的绿色路径,但反应物与产物吸附与活化不均衡引发的活性-选择性权衡问题仍是核心难题。本文通过温和还原策略,在锐钛矿二氧化钛纳米立方体上实现钯氧化态(Pd 0 、Pd δ + 、Pd 2+ )的精准调控,制备出活性位点为中间价态钯的 Pd δ + /TiO 2 光催化剂。系统表征与理论计算结果表明,Pd δ + 能够优化钯与C 2 H 2 /C 2 H 4 之间的d-π/d-π* 轨道相互作用,形成适中的吸附强度,兼顾高效活化乙炔与乙烯快速脱附, Pd 0 会造成吸附过强并引发过度加氢,而Pd 2+ 对底物活化能力较弱。因此,Pd δ + /TiO 2 可实现接近 100% 的乙炔转化率和约 90% 的乙烯选择性,周转数(TON)高达4.1 × 10 4 ,同时具备优异的循环稳定性。该研究阐明了调控钯价态对载流子动力学及轨道杂化进行调控的电子作用机制,为乙炔半加氢光催化剂的合理设计提供了新思路。
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DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Zhichen Liu,Zongxuan Yang,Hongwei Zhang,Shidong Wang,Qunhong Liu,Zhengyu Zhao,Xiaojun Bao,Pei Yuan
Palladium-based catalysts have been intensively investigated for the hydrogenation of nitroarenes due to their high activity. However, it remains a challenge to achieve high selectivity when reducing or halo groups are present. Herein, we propose a facet engineering strategy to regulate the activity and selectivity of Pd/TiO 2 and a series of Pd/TiO 2 catalysts with adjustable proportions of (101) and (001) facet of TiO 2 were synthesized for the selective hydrogenation of nitroarenes. With increased percentage of (101) facet, better dispersed Pd species and more oxygen vacancies (O V ) can be generated on the Pd/TiO 2 catalyst, thereby providing increasing hydrogenation reaction centers with strongly adsorbed nitro groups. As a result, the Pd/TiO 2 with dominant (101) facet and 0.1 wt% of Pd loading (Pd/TiO 2 -c) delivers an outstanding conversion (100 %) of m-chloronitrobenzene, high selectivity (96.8 %) toward m-chloroaniline, and excellent reusability. In situ characterizations and density functional theory (DFT) simulation reveal that the Pd/TiO 2 -c exhibits much stronger adsorption toward nitro groups than chlorine group, while the catalyst with more (001) facet shows similar adsorption capability toward these two groups. Thereby, nitro group is more preferentially adsorbed and hydrogenated during the reaction on Pd/TiO 2 -c, which explains the excellent selectivity. Remarkably, Pd/TiO 2 -c can also realize excellent conversion (100 %) and selectivity (> 96 %) toward other functional nitroarenes containing −F, –OH, –CHO, –COCH 2 - groups. This work highlights the facet engineering of supports to tune the physicochemical properties of loaded active metal and the adsorption behavior of reactants, and provides an effective strategy for the further development of efficient Pd-based catalysts for selective nitroarenes hydrogenation.
研究领域:
催化化学
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材料科学
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产品关联
DOI
高影响因子
JOURNAL OF MATERIALS CHEMISTRY
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2012
·Vol. 22
·期 28
·14155-14159
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IF 5.968
Yonghua Zhou,Xingyun Li,Xiulian Pan,Xinhe Bao
Carbon has been widely used as a catalyst support and adsorbent in industry. However, it suffers from poor stability due to its limited mechanical strength, particularly under high pressures and temperatures. We report here a carbide derived carbon (CDC) layer on a porous SiC surface, which has the properties of high mechanical strength and is easy to shape. The CDC exhibits an amorphous structure and contains mainly mesopores with a BET surface area of 125 m2 g−1. The CDC–SiC composite yields a comparable performance to coconut activated carbon (AC) as a catalyst support in the probe reaction hydrogenation of 4-carboxybenzaldehyde. The further introduction of TiO2 nanoparticles enhances the activity and stability significantly because of the improved dispersion of Pd particles on CDC–SiC. The activity is 4 times higher than the Pd/AC catalyst. Pd–TiO2/CDC–SiC shows great promise as an alternative to the current AC supported Pd catalyst for the crude terephthalic acid hydropurification industry.
研究领域:
化学工程
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材料科学
✓ 已验证
DOI
高影响因子
Progress in Natural Science-Materials International
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2016
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IF 1.753
Yu Bai,Chunlei Wang,Xingyi Zhou,Junling Lu,Yujie Xiong
Pd typically exhibits relatively low catalytic activity in CO oxidation, as CO is apt to be adsorbed on Pd to poison the surface for O 2 activation. In this Letter, we report that this limitation can be overcome by integrating Pd with TiO 2 . The TiO 2 was coated on Pd nanocubes with a controllable thickness using atomic layer deposition (ALD) method. Given the different work functions of TiO 2 and Pd, the electrons in TiO 2 semiconductor will flow toward Pd. With the electron density increased on Pd, the adsorption of CO to Pd will be weakened while the oxygen activation can be facilitated. Meanwhile, the interface-confined sites at Pd-TiO 2 may further enhance the oxygen activation. As the species adsorption and activation are strongly correlated with electron density, the performance of Pd-TiO 2 in CO oxidation turns out to depend on the TiO 2 thickness, which determines the number of transferred electrons, within a certain range (<1.8 nm). This work provides a new strategy for enhancing catalytic performance through tailoring charge densities in hybrid catalysts.
研究领域:
材料科学
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催化化学
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产品关联
DOI
高影响因子
Catalysts
·
2023
·Vol. 13
·期 4
·643
·
IF 3.9
Minming Bao,Yuxi Liu,Jiguang Deng,Lin Jing,Zhiquan Hou,Zhiwei Wang,Lu Wei,Xiaohui Yu,Hongxing Dai
The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPdxnanoparticles (NPs) were loaded on TiO2through the electrostatic adsorption approach to generate theyAuPdx/TiO2(i.e., 0.35AuPd0.46/TiO2, 0.34AuPd2.09/TiO2, and 0.37AuPd2.72/TiO2;xandyare Pd/Au molar ratio and AuPdxloading, respectively;x= 0.46–2.72; andy= 0.34–0.37 wt%) catalysts, and their catalytic activities for the oxidation of ethyl acetate were determined. The results showed that the 0.37AuPd2.72/TiO2sample exhibited the best activity (T50%= 217 °C andT90%= 239 °C at SV = 40,000 mL/(g h),Ea= 37 kJ/mol, specific reaction rate at 220 °C = 113.8 µmol/(gPds), and turnover frequency (TOFNoble metal) at 220 °C = 109.7 × 10−3s−1). The high catalytic performance of the 0.37AuPd2.72/TiO2sample was attributed to the good dispersion of AuPd2.72NPs, the strong redox ability, the large ethyl acetate adsorption capacity, and the strong interaction between AuPdxand TiO2. Acetaldehyde, ethanol, and acetic acid are the main intermediates in the oxidation of ethyl acetate, and the loading of AuPdxNPs effectively reduces the formation of the toxic by-product acetaldehyde. The oxidation of ethyl acetate over the 0.34AuPd2.09/TiO2sample might occur via the pathway of ethyl acetate → ethanol → acetic acid → acetate → CO2and H2O. We believe that the obtained results may provide a useful idea for the design of bimetallic catalysts under industrial conditions and for understanding the VOCs oxidation mechanisms.Keywords:supported Au–Pd nanocatalyst;ethyl acetate oxidation;strong electrostatic adsorption;sulfur dioxide resistance;reaction mechanism
研究领域:
催化化学
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环境科学
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材料科学
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产品关联
DOI
高影响因子
ChemCatChem
·
2022
·Vol. 14
·期 13
·e202200120
·
IF 5.497
Hongmei Fu,Haijun Chen,Beibei Gao,Tianliang Lu,Yunlai Su,Lipeng Zhou,Meijiang Liu,Hongji Li,Xiaomei Yang
Graphical Hydrodeoxygenation and reductive etherification of biomass-derived aldehydes were realized on the same Pd/TiO 2 photocatalyst via photocatalytic transfer hydrogenation using aliphatic alcohols as hydrogen donor, and the selectivity was easily switched by the substrate concentration. The development of selectivity control strategies based on external operational conditions without modification of catalyst is an attractive but challenging issue in photocatalysis. Herein we reported the substrate concentration-switched selectivity in photocatalytic transfer hydrogenation of biomass-derived aromatic aldehydes. With the same catalyst, hydrodeoxygenation was realized at low aldehyde concentration and reductive etherification was realized at high aldehyde concentration. Mechanistic studies revealed that the substrate concentration affected the electron density on catalyst, thus controlled the initial reduction of formyl group and types of intermediates. Competitive adsorption of these intermediates on the catalyst affected hydrogenolysis of C−O bonds in the later stage. This method is easy to handle, and achieved selective hydrogenation of diverse bio-based aldehydes to corresponding deoxygenated products and unsymmetric ether products as potential fuel additives under mild conditions. This work sheds light on the effect of substrate concentration on the selectivity in photocatalysis.
研究领域:
催化
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化学工程
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材料科学
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可再生能源
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DOI
高影响因子
JOURNAL OF ORGANIC CHEMISTRY
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2018
·
IF 4.805
Zhenhua Dong,Jinwei Yuan,Yongmei Xiao,Pu Mao,Wentao Wang
A rapid and practical protocol for the chemoselective deoxygenation of various aromatic ketones and aldehydes was described, which used a tandem catalyst composed of heterogeneous Pd/TiO2 + homogeneous FeCl3 with the green hydrogen source, polymethylhydrosiloxane (PMHS). The developed catalytic system was robust and scalable, as exemplified by the deoxygenation of acetophenone, which was performed on a gram scale in an atmospheric environment utilizing only 0.4 mol % Pd/TiO2 + 10 mol % FeCl3 catalyst to give the corresponding ethylbenzene in 96% yield within 10 min at room temperature. Furthermore, the Pd/TiO2 catalyst was shown to be recyclable up to three times without an observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. Insights toward the reaction mechanism of Pd-catalyzed reductive deoxygenation for aromatic ketones and aldehydes were investigated through operando IR, NMR, and GC-MS techniques.
研究领域:
有机化学
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催化化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Physical Chemistry C
·
2022
·
IF 4.177
Jiarui Zhao,Junhong Fu,Jian Wang,Kaixin Tang,Qi Liu,Jiahui Huang
The Pd/TiO2 catalysts with varying Pd nanoparticle sizes are used to study the control of selectivity toward the hydrogenation of 3-nitrostyrene (3-NS). Our results show the selectivities of 3-vinylanilline (3-VA) rise by decreasing the particle size, while the selectivity of 3-ethylnitrobenzene (3-EN) is the opposite. However, over the Pd/SiO2 catalysts, 3-EN moieties are the dominant product regardless of their differences in particle size. We find that the electronic interactions between Pd NPs and the TiO2 support rise by decreasing particle size, as a result, creating more admetals on the Pd NPs in contact with TiO2, which favorably adsorb the nitro group of 3-NS, thus resulting in enhanced selectivity of 3-VA. However, the classical strong metal–support interactions (SMSI) induced by reduction at elevated temperatures play no significant role in the controlling of selectivities of 3-VA and 3-EN. The SiO2-supported Pd NPs without electronic metal–support interactions (EMSIs) prefer the reduction of the vinyl group of 3-NS. This work underlines the importance of EMSI governing the selectivity for hydrogenation of unsaturated nitroarene reactions.
研究领域:
催化化学
·
材料科学
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产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
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2020
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IF 16.683
Ming Lei,Zhiying Wang,Yao Tang,Huimin Wang,Lihua Zhu,Heqing Tang
The use of palladium deposited TiO 2 (Pd/TiO 2 ) as catalysts yielded complete debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE47) in isopropanol solution containing NaOH at 40 °C within 60 min. The final organic products were diphenyl ether and dibenzofuran. It was disclosed that two competing reduction paths (hydro-debromination and coupling-debromination) occurred over Pd nanoparticles . The hydro-debromination was dependent on the participation of active H atom species generated by catalytic transfer hydrogenation on metallic Pd. The coupling-debromination proceeded via the oxidative addition of Pd(0) to B r 2 C 12 H 8 OB r 2 ′ , leading to an transition state of B r 2 Pd II C 12 H 8 OB r 2 ′ , the reductive dissociation of which resulted in the elimination of Br − ions, producing a new transition state Pd 0 C 12 H 8 OB r 2 ′ − . A further oxidative addition of Pd 0 C 12 H 8 OB r 2 ′ − generated B r 2 ′ Pd II C 12 H 8 O − , and its final reductive elimination provided dibenzofuran, leading to the regeneration of Pd(0). The integration of the catalytic coupling and hydrogenation reaction on Pd nanoparticles greatly accelerated the removal of the halogenated organic pollutants.
研究领域:
环境科学
·
催化化学
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）