期刊文献+
共找到1,183篇文章
< 1 2 60 >
每页显示 20 50 100
Study of M-ZSM-5 nanocatalysts(M: Cu, Mn, Fe, Co …) for selective catalytic reduction of NO with NH_3: Process optimization by Taguchi method 被引量:2
1
作者 Parvaneh Nakhostin Panahi Darush Salari +1 位作者 Aligholi Niaei Seyed Mahdi Mousavi 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2015年第10期1647-1654,共8页
A series of different transition metals(V,Co,Cr,Mn,Fe,Ni,Cu and Zn) promoted H-ZSM-5 catalysts were prepared by impregnation method and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and tra... A series of different transition metals(V,Co,Cr,Mn,Fe,Ni,Cu and Zn) promoted H-ZSM-5 catalysts were prepared by impregnation method and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The catalytic activity of these catalysts was evaluated for the selective catalytic reduction(SCR) of NO with NH_3 as reductant in the presence of oxygen.The results revealed that the catalytic activity of Cu-ZSM-5 nanocatalyst for NO conversion to N_2 was 80%at 300 ℃,which was the best among various promoted metals.Design of experiments(DOEs) with Taguchi method was employed to optimize NH_3-SCR process parameters such as NH_3/NO ratio,O_2 concentration,and gas hourly space velocity(GHSV) over Cu-ZSM-5 nanocatalyst at 250 and 300 ℃.Results showed that the most important parameter in NH_3-SCR of NO is O_2 concentration;followed by NH_3/NO ratio and GHSV has little importance.The NO conversion to N_2 of 63.1%and 94.86%was observed at 250℃ and 300℃,respectively under the obtained optimum conditions. 展开更多
关键词 NO SCR ZSM-5 Transition metal Taguchi method
在线阅读 下载PDF
Synthesis and luminescence properties of nanocrystalline Gd_3Ga_5O_(12):Eu^(3+) by a homogeneous precipitation method 被引量:3
2
作者 Li Yanhong Lu Haiyan +2 位作者 Zhang Yongming Ma Jing Song Guoyi 《Rare Metals》 SCIE EI CAS CSCD 2012年第6期599-603,共5页
Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectrosc... Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the samples. The effects of the initial solution pH value and urea content on the structure of the sample were studied. The XRD results show that pure phase Gd3Ga5O12 can be obtained at pH =6 and pH =8 of the initial solution. The average crystallite size can be calculated as in the range of 24~33 nm. The average crystallite size decreases with increasing molar ratio of urea to metal ion. The results of excitation spectra and emission spectra show that the emission peaks are ascribed to 5D0→7FJ transitions of Eu3+, and the magnetic dipole transition originated from 5D0 →7F1 of Eu3+ is the strongest; the broad excitation bands belong to change transfer band of Eu?O and the host absorption of Gd3Ga5O12. An efficient energy transfer occurs from Gd3+ to Eu3+. 展开更多
关键词 Gd3Ga5O12:Eu3+ nanocrystal urea homogeneous precipitation method LUMINESCENCE
在线阅读 下载PDF
Assimilation of GMS-5 satellite winds using nudging method with MM5 被引量:1
3
作者 高山红 吴增茂 杨波 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2006年第3期215-224,共10页
With the aid of Meteorological Information Composite and Processing System (MICAPS), satellite wind vectors derived from the Geostationary Meteorological Statellite-5 (GMS-5) and retrieved by National Satellite Meteor... With the aid of Meteorological Information Composite and Processing System (MICAPS), satellite wind vectors derived from the Geostationary Meteorological Statellite-5 (GMS-5) and retrieved by National Satellite Meteorology Center of China (NSMC) can be obtained. Based on the nudging method built in the fifth-generation Mesoscale Model (MM5) of Pennsylvania State University and Na- tional Center for Atmospheric Research, a data preprocessor is developed to convert these satellite wind vectors to those with specified format required in MM5. To examine the data preprocessor and evaluate the impact of satellite winds from GMS-5 on MM5 simulations, a series of numerical experimental fore- casts consisting of four typhoon cases in 2002 are designed and implemented. The results show that the preprocessor can process satellite winds smoothly and MM5 model runs successfully with a little extra computational load during ingesting these winds, and that assimilation of satellite winds by MM5 nudging method can obviously improve typhoon track forecast but contributes a little to typhoon intensity forecast. The impact of the satellite winds depends heavily upon whether the typhoon bogussing scheme in MM5 was turned on or not. The data preprocessor developed in this paper not only can treat GMS-5 satellite winds but also has capability with little modification to process derived winds from other geostationary satellites. 展开更多
关键词 satellite winds ASSIMILATION nudging method MM5
原文传递
Effects of different introduction methods of Ce^4+and Zr^4+on denitration performance and anti-K poisoning performance of V2O5-WO3/TiO2 catalyst 被引量:9
4
作者 Jun Cao Xiaojiang Yao +3 位作者 Li Chen Keke Kang Min Fu Yang Chen 《Journal of Rare Earths》 SCIE EI CAS CSCD 2020年第11期1207-1214,I0003,共9页
The purpose of this work is to explore the effects of the introduction methods of Ce^4+and Zr^4+on the physicochemical properties,activity,and K tolerance of V2 O5-WO3/TiO2 catalyst for the selective catalytic reducti... The purpose of this work is to explore the effects of the introduction methods of Ce^4+and Zr^4+on the physicochemical properties,activity,and K tolerance of V2 O5-WO3/TiO2 catalyst for the selective catalytic reduction of NOx by NH3.Four different methods,namely pre-impregnation,post-impregnation,coimpregnation,and co-precipitation,were used to synthesize a series of V2 O5-WO3-TiO2-CeO2-ZrO2 catalysts.The catalysts were characterized by XRD,BET,NH3-TPD,XPS,and H2-TPR techniques.Moreover,the activity and anti-K poisoning performance were tested by an NH3-SCR model reaction.The results show that the introduction of Ce^4+and Zr^4+can improve the catalytic performance of V2O5-WO3/TiO2 catalyst,but the impregnation method cannot enhance the anti-K poisoning performance.Ce^4+and Zr^4+introduced by co-precipitation method can effectively improve the tolerance of K,which is mainly due to the incorporation of Ce^4+and Zr^4+into TiO2 lattice to form a uniform TiO2-CeO2-ZrO2 solid solution,resulting in the optimal surface acidity and redox performance,and reducing the decreases caused by Kpoisoning.Furthermore,based on the best introduction method,we further optimized the molar ratio of Ce^4+/Zr^4+,It is found that the catalyst exhibits the best anti-K poisoning performance when the molar ratio of Ce^4+/Zr^4+is 2:1. 展开更多
关键词 V2O5-WO3/TiO2 denitration catalyst Ce^4+ Zr^4+modification Introduction methods Molar ratio Anti-K poisoning performance Rare Earths
原文传递
Comparative study of Co_(3)O_(4)-ZSM-5 catalysts synthesized by different hydrothermal methods for the catalytic oxidation of dichloromethane 被引量:1
5
作者 Xiaoqi Fei Shuang Cao +2 位作者 Weilong Ouyang Haiqiang Wang Zhongbiao Wu 《Chinese Chemical Letters》 SCIE CAS CSCD 2021年第3期1224-1228,共5页
In this work,various Co_(3)O_(4)-ZSM-5 catalysts were prepared by the microwave hydrothermal method(MH-Co_(3)O_(4)@ZSM-5),dynamic hydrothermal method(DH-Co_(3)O_(4)@ZSM-5),and conventio nal hydrothermal method(CH-Co_(... In this work,various Co_(3)O_(4)-ZSM-5 catalysts were prepared by the microwave hydrothermal method(MH-Co_(3)O_(4)@ZSM-5),dynamic hydrothermal method(DH-Co_(3)O_(4)@ZSM-5),and conventio nal hydrothermal method(CH-Co_(3)O_(4)/ZSM-5).Their catalytic oxidation of dichloromethane(DCM)was analyzed.Detailed characterizations such as X-ray diffractometer(XRD),scanning microscopy(SEM),X-ray photoelectron spectroscopy(XPS),Brunauer-Emmett-Teller(BET),H2 temperature-programmed reduction(H2-TPR),temperature-programmed desorption of O_(2)(O_(2)-TPD),temperature-programmed desorption of NH_(3)(NH_(3)-TPD),diffuse reflectance infrared Fourier-transform spectra with NH_(3)molecules(NH_(3)-DRIFT),and temperature-programmed surface reaction(TPSR)were performed.Results showed that with the assistance of microwave,MH-Co_(3)O_(4)@ZSM-5 formed a uniform core-shell structure,while the other two samples did not.MH-Co_(3)O_(4)@ZSM-5 possessed rich surface adsorbed oxygen species,higher ratio of Co^(3+)/Co^(2+),strong acidity,high reducibility,and oxygen mobility among the three Co_(3)O_(4)-ZSM-5 catalysts,which was beneficial for the improvement of DCM oxidation.In the oxidation of dichloromethane,MH-Co_(3)O_(4)@ZSM-5 presented the best activity and mineralization,which was consistent with the characterizations results.Meanwhile,according to the TPSR test,HCl or Cl_(2)removal from the catalyst surface was also promoted in MH-Co_(3)O_(4)@ZSM-5 by their abundant Bronsted acid sites and the promotion of Deacon reaction by Co_(3)O_(4)or the synergistic effect of Co_(3)O_(4)and ZSM-5.According to the results of in situ DRIFT studies,a possible reaction pathway of DCM oxidation was proposed over the MH-Co_(3)O_(4)@ZSM-5 catalysts. 展开更多
关键词 DICHLOROMETHANE Catalytic oxidation Co_(3)O_(4) ZSM-5 Core-shell structure Microwave hydrothermal method
原文传递
Optical and scintillation properties of Ce:Y_(3)Al_(5)O_(12) single crystal fibers grown by laser heated pedestal growth method 被引量:2
6
作者 Xibin Wang Yun Dai +4 位作者 Zhonghan Zhang Liangbi Su Huamin Kou Yangxiao Wang Anhua Wu 《Journal of Rare Earths》 SCIE EI CAS CSCD 2021年第12期1533-1539,I0003,共8页
The single crystal scintillating optical fibers acting as the scintillators and light conductors show potential application in scintillating fiber array detectors with high spatial resolution.In this paper we report t... The single crystal scintillating optical fibers acting as the scintillators and light conductors show potential application in scintillating fiber array detectors with high spatial resolution.In this paper we report the growth of 0.2 at%Ce:Y_(3)Al_(5)O_(12) single crystal fiber.The crystalline phase,surface morphology of the axialsection and cro ss-section,optical and scintillation properties of the as-grown fiber were investigated.The Ce:Y_(3)Al_(5)O_(12) single crystal fiber has a pure YAG phase,a uniform distribution of cerium in the axialsection and cross-section surface.Emission spectrum is composed of broad bands ranging from 440 to700 nm.In addition,the single crystal fiber has a high light yield of 26115±2000 photons/MeV,low energy resolution of 9.44%@662 keV and decay time of a fast component of 78 ns and a slow component of 301 ns.The intensity ratio of fast to slow components is roughly 8:1. 展开更多
关键词 Ce:Y_(3)Al_(5)O_(12) Single crystal fiber Laser heated pedestal growth method Rare earth Scintillator
原文传递
The tidal tails of globular cluster Palomar 5 based on the neural networks method
7
作者 Hu Zou Zhen-Yu Wu +1 位作者 Jun Ma Xu Zhou 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2009年第10期1131-1148,共18页
The sixth Data Release (DR6) of the Sloan Digital Sky Survey (SDSS) provides more photometric regions, new features and more accurate data around globular cluster Palomar 5. A new method, Back Propagation Neural N... The sixth Data Release (DR6) of the Sloan Digital Sky Survey (SDSS) provides more photometric regions, new features and more accurate data around globular cluster Palomar 5. A new method, Back Propagation Neural Network (BPNN), is used to estimate the cluster membership probability in order to detect its tidal tails. Cluster and field stars, used for training the networks, are extracted over a 40 × 20 deg^2 field by color-magnitude diagrams (CMDs). The best BPNNs with two hidden layers and a Levenberg-Marquardt (LM) training algorithm are determined by the chosen cluster and field samples. The membership probabilities of stars in the whole field are obtained with the BPNNs, and contour maps of the probability distribution show that a tail extends .5.42° to the north of the cluster and another tail extends 3.77° to the south. The tails are similar to those detected by Odenkirchen et al., but no more debris from the cluster is found to the northeast in the sky. The radial density profiles are investigated both along the tails and near the cluster center. Quite a few substructures are discovered in the tails. The number density profile of the cluster is fitted with the King model and the tidal radius is determined as 14.28'. However, the King model cannot fit the observed profile at the outer regions (R 〉 8') because of the tidal tails generated by the tidal force. Luminosity functions of the cluster and the tidal tails are calculated, which confirm that the tails originate from Palomar 5. 展开更多
关键词 methodS statistical -- galaxy halo -- galaxy structure -- globular cluster individual (Palomar 5
在线阅读 下载PDF
STUDY ON MEAN ACTIVITY C0EFFICIENT OF 5,10,15,20—TETRAKIS PORPHYRIN SODIUM BY FREEZING—POINT DEPRESSION METHOD
8
作者 徐英 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 1997年第3期48-50,共3页
The mean activity coefficient of 5, 10,15 , 20-tetrakis (P-methoxyl-O-sulfophenyl)porphyrin sodium in dilute aqueous solution has been determined in the modality range 0. 00547-0. 08871 mol · kg-1at 273. 2 K by t... The mean activity coefficient of 5, 10,15 , 20-tetrakis (P-methoxyl-O-sulfophenyl)porphyrin sodium in dilute aqueous solution has been determined in the modality range 0. 00547-0. 08871 mol · kg-1at 273. 2 K by the freezing-point depression method . The results of γ± are 0. 9945-0. 7695, it is in close agreement with that by isopiestic method. 展开更多
关键词 5 10 15 20-tetrakis (p-methoxyl-o-sul-fophenyl) porphyrin sodium mean activity coefficient freezing-point depression method
在线阅读 下载PDF
Synthesis and electrochemical properties of nanocrystalline Li[Li_(1/3)Ti_(5/3)O_4] by complex sol-gel method 被引量:1
9
作者 杨建文 钟晖 +3 位作者 钟海云 戴艳阳 李荐 赵绚 《中国有色金属学会会刊:英文版》 CSCD 2004年第5期1012-1016,共5页
Li[Li1/3Ti5/3O4] spinel-framework structure material is a kind of great interest for negative electrodes in energy storage cell. The synthesis of nanocrystalline Li[Li1/3Ti5/3O4] by sol-gel method using inorganic comp... Li[Li1/3Ti5/3O4] spinel-framework structure material is a kind of great interest for negative electrodes in energy storage cell. The synthesis of nanocrystalline Li[Li1/3Ti5/3O4] by sol-gel method using inorganic compounds and citric acid is developed, and single phase powder is obtained above 700 ℃. The electrochemical performances (of Li[Li1/3Ti5/3O4]) cathodes in lithium cell are studied. Special capacities are 131 mA·h·g-1 at 0.5C rate and 154 mA·h·g-1 at 0.1C in cycle test. No passivation layer is formed on Li[Li1/3Ti5/3O4] anode in lithium ion battery, and it is much safer than lithium metal and carbonaceous anodes. Faradic impedance in the charged cell is remarkably higher than that in discharged state, which is caused by distinct conductivities of Li[Li1/3Ti5/3O4] and (Li2[Li1/3Ti5/3O4].) 展开更多
关键词 电化学特征 微晶体材料 Li[Li1/3Ti5/3O4] 溶胶-凝胶方法 电池
在线阅读 下载PDF
A NOVEL METHOD FOR SYNTHESIZING α,α-DISUBSTITUTED α-AMINO ACID——DIALKYLATION OF 2-OXAZOLIN-5-ONE
10
作者 Ji Jun CHEN Zheng Ming DU +1 位作者 Yao Zeng SHI Hong Wen HU Dcpratment of Chemistry,Nanjing University,Nanjing 210008 《Chinese Chemical Letters》 SCIE CAS CSCD 1991年第3期193-194,共2页
4,4-Dialkyl-2-oxazolin-5-ones are prepared by one step reaction of 2-oxazolin-5-one with the magnesium methyl carbonate(MMC)and alkyIhalides.It is a novel and convenient method for synthesis of α, Υ-disubstitutcd α... 4,4-Dialkyl-2-oxazolin-5-ones are prepared by one step reaction of 2-oxazolin-5-one with the magnesium methyl carbonate(MMC)and alkyIhalides.It is a novel and convenient method for synthesis of α, Υ-disubstitutcd α-amino acid by hydrolysis of 4,4-dialkyl-2-oxazolin-5-ones. 展开更多
关键词 AMINO ACID A NOVEL method FOR SYNTHESIZING DIALKYLATION OF 2-OXAZOLIN-5-ONE DISUBSTITUTED PPM NH
在线阅读 下载PDF
Exact Solutions of the φ^6 + φ^5 Model Using Truncated Method
11
作者 YANG Jian-Song 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第2X期295-298,共4页
In this letter, the φ^6 + φ^5 model in (D + 1) dimensions can be solved by a truncated series method. A series of solitary solutions of the φ^6 + φ^5 model in (D + 1) dimensions have be obtained.
关键词 φ^6 φ^5 model solitary solutions truncated series method
在线阅读 下载PDF
两步变温合成纳米堆积ZSM-5分子筛及其催化性能 被引量:1
12
作者 宋金锐 梁亚凝 +6 位作者 张燕挺 张红智 李宁 刘景怡 丁云龙 侯楠 李晓峰 《石油学报(石油加工)》 北大核心 2025年第2期489-497,共9页
纳米堆积ZSM-5分子筛具有良好的扩散与传质能力,在各类催化和吸附方面表现出优异的性能。采用两步变温法制备纳米堆积ZSM-5分子筛,通过X射线衍射光谱、扫描电子显微镜、N 2吸附-脱附、氨气程序升温脱附、X射线荧光光谱分析、X射线光电... 纳米堆积ZSM-5分子筛具有良好的扩散与传质能力,在各类催化和吸附方面表现出优异的性能。采用两步变温法制备纳米堆积ZSM-5分子筛,通过X射线衍射光谱、扫描电子显微镜、N 2吸附-脱附、氨气程序升温脱附、X射线荧光光谱分析、X射线光电子能谱分析等手段对合成的分子筛样品进行表征。采用偏三甲苯异构化反应表征纳米堆积ZSM-5分子筛的催化性能。结果表明:两步变温法比传统法更快合成分子筛(10 h);初级晶粒粒径为100~200 nm,晶粒堆积组成的团聚体尺寸更小,约为800 nm;两步变温法所合成的样品外比表面积最大可达53.92 m^(2)/g,与传统法相比酸性无明显变化。偏三甲苯异构化在MHSV=5.28 h-1、T=350℃、p=0.8 MPa的反应条件下,两步变温法合成样品(低温4 h,高温24 h)比传统法合成样品的性能显著提高,偏三甲苯转化率提高了14.1百分点,均三甲苯收率和选择性分别提高了8.5百分点和2.0百分点。 展开更多
关键词 ZSM-5分子筛 两步变温法 晶种溶液 纳米堆积 偏三甲苯异构化
在线阅读 下载PDF
静脉用5-羟色胺3受体拮抗剂的多准则量化评价实践
13
作者 魏浩洁 武东 +3 位作者 潘行山 孙翠玲 高丽 汪晓娟 《中国新药与临床杂志》 北大核心 2025年第3期206-212,共7页
目的对静脉用5-羟色胺3(5-HT3)受体拮抗剂进行多维测量化评价药品遴选和评价提供参考依据。方法通过德尔菲法构建药品遴选和评价多准则量化评分表,对本院昂丹司琼、格拉司琼、托烷司琼和帕洛诺司琼4个品种(7个品规)进行量化评价。结果... 目的对静脉用5-羟色胺3(5-HT3)受体拮抗剂进行多维测量化评价药品遴选和评价提供参考依据。方法通过德尔菲法构建药品遴选和评价多准则量化评分表,对本院昂丹司琼、格拉司琼、托烷司琼和帕洛诺司琼4个品种(7个品规)进行量化评价。结果构建的药品遴选和评价多准则量化评分表包括临床必需性、有效性、安全性、经济性、政策属性、药品质量、生产企业评估7个一级量化指标(共19个二级量化指标)。7个静脉用5-HT3受体拮抗剂得分为45.0~65.5分,昂丹司琼得分较高,帕洛诺司琼得分较低,最主要的差异表现在药品经济性和政策属性等方面。结论构建的药品遴选和评价多准则量化评分表有助于医疗机构对静脉用5-HT3受体拮抗剂进行多维度的横向综合评价。 展开更多
关键词 德尔菲法 5-羟色胺3受体拮抗剂 多准则量化 药品遴选
原文传递
STUDIES ON THE SYNTHESIS OF Ti_3O_5 BY MICROWAVE INDUCED PLASMA METHOD
14
作者 Ai Min YU Wen Guo XU +1 位作者 Wen Jun YANG Quan Zhong LI and Qin Han JIN (Department of Chemistry, Jinn University, Changchun 130023) 《Chinese Chemical Letters》 SCIE CAS CSCD 1994年第5期447-448,共2页
Using a low power microwave generator and a surfatron discharge cavity, Ti3O5 was synthesized via the hydrogenation of TiO2 in surface wave induced microwave plasma. Besides, the chemical behavior of hydrogen in the p... Using a low power microwave generator and a surfatron discharge cavity, Ti3O5 was synthesized via the hydrogenation of TiO2 in surface wave induced microwave plasma. Besides, the chemical behavior of hydrogen in the plasma and its influence on the formation of Ti3O5 were preliminarily studied. 展开更多
关键词 TI STUDIES ON THE SYNTHESIS OF Ti3O5 BY MICROWAVE INDUCED PLASMA method
在线阅读 下载PDF
制备方法对CO_(2)甲烷化Ni/ZSM-5结构和催化性能的影响
15
作者 黄贤金 莫文龙 +5 位作者 马童童 丛兴顺 卢立菊 马亚亚 王锋 杨晓勤 《分子催化(中英文)》 北大核心 2025年第5期405-414,I0001,I0002,共12页
采用等体积浸渍法、旋转真空浸渍法、机械化学法和机械化学/旋转真空浸渍法分别制备了IWIP、RVIP、MC和MC/RVIP四种Ni/ZSM-5催化剂.通过XRD、H_(2)-TPR、NH_(3)-TPD、N2吸附/脱附、SEM、EDX-mapping、TG-DTG和H_(2)-TPH等分析催化剂的... 采用等体积浸渍法、旋转真空浸渍法、机械化学法和机械化学/旋转真空浸渍法分别制备了IWIP、RVIP、MC和MC/RVIP四种Ni/ZSM-5催化剂.通过XRD、H_(2)-TPR、NH_(3)-TPD、N2吸附/脱附、SEM、EDX-mapping、TG-DTG和H_(2)-TPH等分析催化剂的晶相结构、还原性、酸碱性、织构性质、微观形貌和积炭含量.结果表明,IWIP催化剂的Ni颗粒尺寸较大,金属-载体相互作用较弱,主要是游离态α-NiO.RVIP催化剂的活性组分前驱体在真空状态下被充分浸入载体孔隙内部,较大的比表面积有助于提高RVIP催化剂活性金属的分散性.MC和MC/RVIP催化剂的Ni颗粒尺寸较小,且金属-载体相互作用显著增强.在温度为250~550℃、压力为0.1 MPa、CO_(2)流量为80 mL·min^(-1)、CO_(2)∶H_(2)体积比4∶1条件下反应10 h评价催化剂反应性能,MC/RVIP催化剂表现出最佳的反应活性,其CO_(2)转化率、CH4选择性分别为84.8%、94.1%.通过稳定性测试发现,MC/RVIP催化剂的稳定性效果较好,反应后催化剂的积炭量较少,活性较高,积炭类型主要是β型炭物种. 展开更多
关键词 制备方法 二氧化碳 甲烷化 Ni/ZSM-5催化剂 积炭
在线阅读 下载PDF
无溶剂法合成小晶粒ZSM-5及丁烯催化裂解性能
16
作者 麻馨 杨佳宝 +2 位作者 周健 秦玉才 宋丽娟 《燃料化学学报(中英文)》 北大核心 2025年第1期163-173,共11页
采用无溶剂法合成了四种不同硅铝比的小晶粒ZSM-5分子筛,运用XRD、SEM和N_(2)吸附-脱附等温线等对其晶体结构和织构性质进行了表征,并运用NH3-TPD和Py-FTIR探究了分子筛的酸性质,考察了ZSM-5分子筛的丁烯催化裂解反应性能。结果表明,无... 采用无溶剂法合成了四种不同硅铝比的小晶粒ZSM-5分子筛,运用XRD、SEM和N_(2)吸附-脱附等温线等对其晶体结构和织构性质进行了表征,并运用NH3-TPD和Py-FTIR探究了分子筛的酸性质,考察了ZSM-5分子筛的丁烯催化裂解反应性能。结果表明,无溶剂法合成的H型ZSM-5分子筛晶粒呈近球形,粒径(约160 nm)分布均匀。C_(4)烯烃裂解性能与文献已报道水热合成小晶粒ZSM-5分子筛相当,随硅铝比增大丁烯催化裂解活性降低,但乙烯和丙烯选择性明显提高。根据产物分析证实低硅铝比的ZSM-5分子筛较高的酸密度会导致烯烃分子通过氢转移反应生成烷烃,从而降低目标产物的选择性。 展开更多
关键词 ZSM-5分子筛 无溶剂法 催化裂解 酸密度 氢转移反应
在线阅读 下载PDF
沸石间转化法制备xNi@HZSM-5用于煤焦油催化提质的研究
17
作者 郭向阳 樊磊 +3 位作者 王明义 董子豪 王玉高 王俊文 《煤炭转化》 北大核心 2025年第6期17-26,共10页
煤热解焦油催化提质可以将其中的重质组分转化为轻质芳烃,但负载型Ni/HZSM-5中金属Ni多位于分子筛的外表面,在提升轻质芳烃含量的同时会造成焦油过度裂解。采用以HBeta为母体的沸石间转化法制备x Ni@HZSM-5(x为Ni的质量分数,x=3,5,7),... 煤热解焦油催化提质可以将其中的重质组分转化为轻质芳烃,但负载型Ni/HZSM-5中金属Ni多位于分子筛的外表面,在提升轻质芳烃含量的同时会造成焦油过度裂解。采用以HBeta为母体的沸石间转化法制备x Ni@HZSM-5(x为Ni的质量分数,x=3,5,7),将金属Ni封装于分子筛的孔道内,利用HZSM-5分子筛孔道的空间限域特性实现富氢气体活化和焦油裂解活性位点的分离;同时,考察了H_(2)气氛下xNi@HZSM-5对焦油模型化合物芘和荧蒽催化性能及加氢产物的影响。结果表明:经沸石间转化法制备的5Ni@HZSM-5中分子筛晶体呈现非常均匀规则的米粒状颗粒,且金属Ni具有较高的分散性;在原位催化裂解过程中,沸石间转化前后催化剂载体的改变对焦油各性质影响不大,且转化后的催化剂焦油产率、轻质焦油产率及含量均明显高于其母体沸石。其中,5Ni@HZSM-5具有最大的芘和荧蒽转化率,分别为49.1%和56.8%,此时轻质芳烃选择性也达到最大,分别为70.3%和76.0%。 展开更多
关键词 焦油催化提质 沸石间转化法 xNi@HZSM-5 模型化合物 轻质芳烃
在线阅读 下载PDF
时空针灸治疗失眠的疗效观察及对血清褪黑素和5-羟色胺水平的影响
18
作者 刘亮先 王祖红 +5 位作者 方永江 郭春艳 王英浩 盘雪娇 普菊华 朱勉生 《上海针灸杂志》 2025年第4期402-406,共5页
目的 观察时空针灸治疗心肾不交型失眠的临床疗效及对患者血清褪黑素(melatonin, MT)和5-羟色胺(5-hydroxytryptamine,5-HT)水平的影响。方法 将80例心肾不交型失眠患者按随机数字表法分为治疗组和对照组,每组40例。治疗组采用时空针灸... 目的 观察时空针灸治疗心肾不交型失眠的临床疗效及对患者血清褪黑素(melatonin, MT)和5-羟色胺(5-hydroxytryptamine,5-HT)水平的影响。方法 将80例心肾不交型失眠患者按随机数字表法分为治疗组和对照组,每组40例。治疗组采用时空针灸灵龟八法治疗,对照组采用常规针刺治疗。观察两组治疗前后匹兹堡睡眠质量指数(Pittsburgh sleep quality index, PSQI)及血清MT和5-HT水平的变化,比较两组临床疗效和不良反应发生情况。结果 治疗后,两组PSQI总分和各单项评分均降低(P<0.05),且治疗组PSQI总分及入睡时间、睡眠时间、睡眠效率和睡眠障碍的单项评分均低于对照组(P<0.05)。治疗后,治疗组血清MT和5-HT水平均较治疗前升高(P<0.05),且治疗组血清MT和5-HT水平均高于对照组(P<0.05),治疗组血清MT和5-HT治疗前后差值均高于对照组(P<0.05)。治疗组总有效率为92.5%,显著高于对照组的77.5%,差异具有统计学意义(P<0.05)。结论 时空针灸治疗失眠的临床疗效优于常规针刺,可有效改善睡眠质量,可能与调节血清MT和5-HT水平有关。 展开更多
关键词 针刺疗法 时空针灸 灵龟八法 睡眠障碍 褪黑素 5-羟色胺
暂未订购
反浮选菱镁矿尾矿制备MgB_(2)O_(5)晶须的研究
19
作者 董泽明 董泽光 +1 位作者 王疏星 刘朝阳 《耐火材料》 北大核心 2025年第3期185-191,共7页
为了提高菱镁矿尾矿的回收利用,且寻找一种环保的镁源制备MgB_(2)O_(5)晶须,以反浮选菱镁矿尾矿作为镁源,利用熔盐法合成Mg_(2)B_(2)O_(5)晶须。研究了尾矿活化处理、反应温度(700、800和900℃)以及硼酸与尾矿质量比(定义为硼镁比,分别... 为了提高菱镁矿尾矿的回收利用,且寻找一种环保的镁源制备MgB_(2)O_(5)晶须,以反浮选菱镁矿尾矿作为镁源,利用熔盐法合成Mg_(2)B_(2)O_(5)晶须。研究了尾矿活化处理、反应温度(700、800和900℃)以及硼酸与尾矿质量比(定义为硼镁比,分别为0.62、1.24、1.86和2.48)对Mg_(2)B_(2)O_(5)晶须物相组成和显微结构的影响。结果表明:Mg_(2)B_(2)O_(5)晶须的长径比随着硼镁比的增加先增加后减小,当硼镁比为1.86时,达到最大值;800℃为MgB_(2)O_(5)晶须生长的最佳温度,低于此温度难以生成晶须,而温度过高则会导致晶须粗化,长径比减小;球磨和轻烧处理菱镁矿尾矿可破坏尾矿分解后存在的母盐假相,减小粒径,从而提高镁源活性,以此为镁源可获得尺寸均匀和高长径比的Mg_(2)B_(2)O_(5)晶须。 展开更多
关键词 MgB_(2)O_(5)晶须 熔盐法 母盐假相 长径比
在线阅读 下载PDF
ZSM-5表面酸性对正己烷扩散行为的影响
20
作者 姜森 杨野 +2 位作者 张莉 郝芳 秦玉才 《当代化工》 2025年第10期2281-2286,共6页
分子筛表面酸性是影响其吸附-扩散性能的关键因素,但是具体影响机制还未被完全揭示。采用水热合成法合成了3种不同硅铝比的ZSM-5分子筛,并采用零长柱(ZLC)法研究了正己烷的扩散行为,探讨了表面酸性质对ZSM-5分子筛上正己烷扩散行为的影... 分子筛表面酸性是影响其吸附-扩散性能的关键因素,但是具体影响机制还未被完全揭示。采用水热合成法合成了3种不同硅铝比的ZSM-5分子筛,并采用零长柱(ZLC)法研究了正己烷的扩散行为,探讨了表面酸性质对ZSM-5分子筛上正己烷扩散行为的影响机制。结果表明:所合成的3种ZSM-5分子筛形貌特征相近,但表面羟基结构和酸性质存在显著差异,正己烷在较低硅铝比的ZSM-5分子筛(Z5-30和Z5-100)上的扩散速率明显大于高硅铝比的Z5-200样品,这表明正己烷的扩散行为受孔道结构影响较小,而主要取决于表面酸性质,高的表面羟基和酸密度更利于正己烷分子的扩散行为。 展开更多
关键词 ZSM-5 硅铝比 扩散 零柱长(ZLC)法 羟基
在线阅读 下载PDF
上一页 1 2 60 下一页 到第
使用帮助 返回顶部