JOURNAL OF ALLOYS AND COMPOUNDS
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2023
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IF 6.2
Xiaohui Wu,Yulan Jing,Yuanxun Li,Hua Su
The comprehensive properties and sintering temperature of microwave dielectric ceramics are the key factors limiting their practical application. In this work, a novel strategy of complex (Co 1/3 Nb 2/3 ) 4+ ions substituted and adding glass (Li 2 O-B 2 O 3 - SiO 2 -CaO-Al 2 O 3 : LBSCA) was proposed to greatly enhance the microwave dielectric properties of Ba 3 Ti 4- x (Co 1/3 Nb 2/3 ) x Nb 4 O 21 (0 ≤ x ≤ 12 mol%, x CN-BTN) ceramics. A new ceramic of (Co 1/3 Nb 2/3 ) 4+ substitution improved hexagonal phase BTN was successfully fabricated and systematically investigated. As the increased of (Co 1/3 Nb 2/3 ) 4+ ions concentration, the Q× f was greatly increased because of higher packing fraction, and the reduction in the [Nb1/Ti1O 6 ] octahedral distortion caused great changes of τ f . Besides, the P-V-L theory revealed that the Ti/Nb ratio greatly contributed in permittivity ε r , and the Nb-O bonds mainly affected dielectric loss, especially in Nb(1)-O2(1) bond. As a result, the superior microwave dielectric properties were obtained in 6CN-BTN ceramic sintered at 950 °C: ε r ∼40.99 ± 0.48, Q× f ∼17,310 ± 565 GHz, and τ f ∼8.62 ± 4.34 ppm/°C. More encouragingly, 6CN-BTN showed good compatibility with silver, making it a promising K 40 LTCC material for filter and dielectric resonators . This study presented a new strategy to improve the properties of BTN-based materials by complex ions substitution, which was expected to provide a general approach for the design of advanced microwave dielectric ceramics for other material systems.
研究领域:
材料科学
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电子工程
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产品关联
DOI
高影响因子
Molecular Catalysis
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2023
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IF 4.6
Yanlin Xu,Zhuoyi Liu,Bin Liu,Bin Dong,Yuan Pan,Yanpeng Li,Yichuan Li,Hailing Guo,Yongming Chai,Chenguang Liu
Transformation of lignin-derived feedstocks into valuable hydrocarbons is of significant importance but still challenging. This work investigates the hydrodeoxygenation (HDO) of lignin compound guaiacol on Pt-based catalysts with improved surface hydrophobicity and metal dispersion for the first time. The efficiency of guaiacol hydrodeoxygenation into hydrocarbons over Nb 2 O 5 -modified Pt-based catalyst reaches 51 %, nearly doubling that over unmodified Pt/γ-Al 2 O 3 catalyst (25 %). On the one hand, Nb 2 O 5 causes the decrease of hydroxyl groups on catalyst, leading to the enhanced hydrophobicity of catalysts, which increases the reaction rate of guaiacol into hydrocarbons on unit of Pt metal sites. On the other hand, Nb 2 O 5 strengthens the metal-support interaction, which minimizes the size of Pt nanoparticles, providing more exposed metal sites, thus leading to a higher hydrocarbons yield on catalyst. However, excess introduction of Nb 2 O 5 leads to partial coverage of Pt metal sites, resulting in decreased yield of hydrocarbons. Furthermore, the routes of guaiacol HDO reaction over modified Pt-based catalysts are investigated. This work further illustrates the influence of catalyst surface properties on the HDO process of lignin compound, and thereby provides a promising approach for adjustment of catalyst surface properties in order to promote water-liberated reactions.
研究领域:
化学工程
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催化科学
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产品关联
DOI
高影响因子
Biomass Conversion and Biorefinery
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2022
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IF 4.05
Wang Jiacheng,Li Xingyong,Wu Yankun,Duan Jinyi,Zhuang Nihong,Wang Dechao,Zhang Zhaoxia,Ye Yueyuan,Li Shuirong,Zheng Zhifeng
The wide-scale application in the bio-fuel area of fatty acid methyl esters (FAME) has been limited because of its high oxygen content, awful low temperature flowability, and low heating value. In this work, the hydrodeoxygenation (HDO) of methyl palmitate as fatty acid methyl ester model compounds for long-chain alkane via Nb 2 O 5 modified NiAl 2 O 4 catalysts was investigated. The effect of Nb/Ni atomic ratio (0.05:0.30), reaction temperature (260–340 ℃), time (2–10 h), and H 2 pressure (1–5 MPa) on the production of long-chain alkane is exhaustively researched. The results show that the products are mainly pentadecane with a few other alkane hydrocarbons and nickel metal was the main active site. Besides, the added promoter Nb promoted the dispersion of active metal Nickel, increased the acidity, and thus substantially enhanced the HDO activity of methyl palmitate. In response to the best conditions (0.3 g catalyst, 3 g methyl palmitate), the methyl palmitate conversion and pentadecane selectivity over Nb 2 O 5 -NiAl 2 O 4 with 0.20 Nb/Ni atomic ratio reached 91.14% and 80.07%, respectively. However, the methyl palmitate conversion and pentadecane selectivity over pure NiAl 2 O 4 catalyst were only 62.53% and 74.67%, respectively. Therefore, Nb 2 O 5 -NiAl 2 O 4 catalysts exhibit remarkable catalytic ability for HDO of methyl palmitate to alkanes. The low cost, easy preparation, high catalytic performance, and recycling stability of Nb 2 O 5 -NiAl 2 O 4 catalyst demonstrate that catalyst Nb 2 O 5 -NiAl 2 O 4 is a promising effective and efficient catalyst for producing long-chain alkane from methyl palmitate. Graphical abstract
研究领域:
催化化学
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可再生燃料化学
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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）