共查询到20条相似文献,搜索用时 140 毫秒
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氟离子对无胺法合成高硅丝光沸石的结构导向作用 总被引:4,自引:0,他引:4
在含氟无胺体系中合成了高硅丝光沸石,研究了合成条件对丝光沸石产物的影响.结果表明,投料n(SiO2)/n(Al2O3)=20~200时,控制晶化条件可得到高硅丝光沸石纯相.由含氟无胺体系中丝光沸石的热力学稳定相区可见,氟离子的引入对方沸石的生成的相区无影响,ZSM-5和镁碱沸石生成的相区消失,丝光沸石生成的相区扩大,石英生成的相区缩小,且基本上变为两相共存区.合成产物丝光沸石的硅铝比随着氟硅比的升高同步增大,证明氟离子在无胺合成高硅丝光沸石时具有结构导向作用. 相似文献
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在H-ZSM-5沸石上甲醇转化为汽油的初始产物分布姜玄珍(浙江大学化学系,杭州310027)R.F.Howe(新南威尔士大学物理化学系,澳大利亚)关键词H-ZSM-5沸石,甲醇转化汽油,产物分布以氢型ZSM-5沸石作催化剂转化甲醇为汽油(MTG),在... 相似文献
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四乙烯溴化铵—氟化物复合模板剂合β沸石(Ⅱ):β沸石 … 总被引:1,自引:0,他引:1
采用FT-IR、XRD,SEM,TG,ICP-AES等技术研究了四乙经铵-氟化物复合模板剂体系合成β沸石的晶化过程。,发现本体系β沸石的合成遵循液相转变机理,在诱导期向生长期转变的转折点存在过渡态,氟离子对过渡态的形成和转变起重要作用。在诱导期初期固是富铝的,但晶生长期固相硅铝比基本不变,表明硅铝同步进入骨架。 相似文献
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在水蒸气气氛中合成沸石分子筛及其特性 总被引:5,自引:0,他引:5
无定型硅铝凝胶-Na2O-Al2O3-SiO2-H2O在水蒸气相中可以晶化合成出LTA,FAU和MOR沸石晶体。本文重点研究了MOR沸石的晶化条件和物理化学特性。 相似文献
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在(TPA)2O—Na2O—SiO2—H2O体系中MFI型硅沸石的结晶行为(Ⅱ) 总被引:1,自引:0,他引:1
以白炭黑和硅溶胶为硅源,在(TPA)2O-Na2O-SiO2-H2O体系60℃下合成了高结晶度纯相硅沸石,由SEM没得其晶粒尺寸为0.2μm和0.45μm用XRD线宽法是的为0.02μm,一180℃时合成的硅沸石样品相比,低温合成的细晶粒硅沸石已上备内米级的若干特性,其正己烷吸附量反常增大;XRD、FTIR、^29SiMAS NMR和TG/DTG/DTA的研究证明,其结构破坏温度和单斜/正交对称性 相似文献
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Comparison study on transformation of iron oxyhydroxides: Based on theoretical and experimental data
We have investigated the catalytic transformation of ferrihydrite, feroxyhyte, and lepidocrocite in the presence of Fe(II). In this paper, the transformation from akaganeite and goethite to hematite in the presence of trace Fe(II) was studied in detail. The result indicates that trace Fe(II) can accelerate the transformation of akaganeite and goethite. Compared with the transformation of other iron oxyhydroxides (e.g., ferrihydrite, feroxyhyte, lepidocrocite, and akaganeite), a complete transformation from goethite to hematite was not observed in the presence of Fe(II). On the basis of our earlier and present experimental results, the transformation of various iron oxyhydroxides was compared based on their thermodynamic stability, crystalline structure, transformation mechanism, and transformation time. 相似文献
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紫外光谱法结合多元曲线分辨研究黄芩苷的转化规律 总被引:1,自引:0,他引:1
采用紫外光谱法采集不同工艺条件下黄芩苷转化过程的光谱数据, 结合多元曲线分辨-交替最小二乘法(MCR-ALS)处理获得的数据, 得到黄芩苷转化反应过程中各组分的光谱图和浓度随时间变化曲线. 结果表明, 黄芩苷转化过程符合两步连续一级反应模型; 根据不同时间点采集的多级质谱和飞行时间质谱信息, 推断了黄芩苷转化产物和可能的转化途径, 转化产物主要包括黄芩苷的同分异构体、 黄芩素和黄芩素二聚体. 对黄芩苷转化规律的研究有助于黄芩制剂的质量控制. 相似文献
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The effect of molecular weight on the polymorphic transformation of isotactic poly(1-butene)(iPB) under room temperature had been investigated by fourier transform infrared spectroscopy(FT-IR). The phase transformation time, phase transformation rate and phase transformation time difference between phase I and phase II at a given transformation degree were used to analysis the phase transformation kinetics of iPB aging at room temperature. The results show that the reduction of phase II can occur quickly at room temperature and seem less dependent on the molecular weight. However, the molecular weight has great effect on the formation of phase I. When the phase transformation degree for phase I reach 90%, a distinct transformation time difference can be observed. In order to clearly explain the difference in the reduction of phase II and the growth of phase I, a phase transformation model from the chain conformation level for iPB with different molecular weight have been drawn. DSC analysis was used to support the proposed model. 相似文献
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We demonstrate how a single-crystal to single-crystal transformation resulting from bridging-linker replacement is possible in extended 2D and 3D metal-organic frameworks (MOFs) by introducing pillared paddlewheel MOF structures into a solution containing dipyridyl linkers. No lateral movement of the layers was observed during this transformation, creating a templating effect from the "parent" structure to the "daughter" structure. A previously unattainable structure was obtained by a two-step synthetic method utilizing the bridging-linker replacement transformation method. Additionally, a bridging-linker insertion was observed when excess linker was used with the 2D MOF structure, inducing an overall 2D to 3D transformation. 相似文献
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Ferrihydrite was prepared by two different procedures. Ferrihydrite-1 was prepared by dropping NaOH solution into Fe(III) solution. Ferrihydrite-2 was prepared by adding Fe(III) and NaOH solutions into a certain volume of water simultaneously. Our earlier results obtained at ∼100 °C have shown that the structure of ferrihydrite-2 favors its solid state transformation mechanism. Further research reveals that the structure of ferrihydrite-2 favors its dissolution re-crystallization mechanism at a temperature of ≤60 °C. Based on the transformation mechanism of ferrihydrite at different temperatures, the controllable transformation from ferrihydrite to various iron (hydr)oxides such as lepidocrocite, goethite, hematite and magnetite can be achieved by adjusting the pH, transformation temperature, transformation time, the amount of Fe(II) as well as the preparation procedures of ferrihydrite. The results in the present paper give a nice example that the transformation of a precursor can be controlled with the help of mechanism. 相似文献
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Diana Carolina Albán Reyes Nils Skoglund Anna Svedberg Bertil Eliasson Ola Sundman 《Cellulose (London, England)》2016,23(2):1061-1072
A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 °C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25–1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH. 相似文献
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Fumio Watari P. Delavignette J. Van Landuty S. Amelinckx 《Journal of solid state chemistry》1983,48(1):49-64
The dehydration reaction accompanying the goethite-hematite transformation was observed by high resolution electron microscopy. The origin of the satellites which appear during the transformation is discussed from the point of view of structure factor and shape factor. Details of the transformation mechanism have been clarified through these results and from the considerations based on the observations. The transformation goes directly from goethite to hematite in such a way that the dehydration reaction is completed within a small volume of about 60 Å width in such a manner that practically only local rearrangement into the product structure takes place, growth of hematite being very limited. After surface transformation is completed, bulk transformation develops spatially by the repeated generation of units composed of voids and hematite, until the whole volume is occupied by such units. The role of the voids and the changes of their morphology are also discussed in comparison with other interpretations of the transformation sequences. 相似文献
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Phase Transformation Mechanism of Graphite-Turbostratic Graphite in the Course of Mechanical Grinding 总被引:1,自引:0,他引:1
GAO Zhong min * JIN Hong zheng LI Xiang shan HUA Zhong . State Key Laboratory of Inorgnic Synthesis & Preparative Chemistry . Department of Material Science Jilin University Changchun P. R. China 《高等学校化学研究》2003,19(2):216-218
IntroductionSome industrially- widely- used carbon materi-als,such as Pan- based carbon fiber,glassy car-bon,carbon black and carbon film,have a tur-bostratic graphitic structure[1— 4] . This structure isbased on the same hexagonal plane of the carbonatoms as graphitic crystalline. The difference be-tween atoms lies in the random translations and ro-tations which destroy the character of three dimen-sional ordering. Turbostratic graphite materials aremostly composed of non graphitic carbon. … 相似文献