共查询到18条相似文献,搜索用时 328 毫秒
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本文应用碱性气体吸附的红外光谱和TPD技术研究了FeZSM-5(F_4)的酸性,酸性顺序为:H-F_4>Fe_2O_3/F_4>F_4原粉>水热处理的K-F_4>Li-F_4>NaF_4>K-F_4>NaOH/F_4,比较了酸强度和积炭对乙苯氧化脱氢性能的影响,以及催化剂酸碱性质与积炭的关系.结果表明,乙苯氧化脱氢反应是在酸碱协同作用下进行的,积炭也参与了氧化脱氢反应,催化剂表面上L酸中心产生的具有一定C、H、O比的积炭具有高的氧化脱氢活性.碱金属阳离子改性的具有L酸中心的FeZSM-5是乙苯氧化脱氢的高活性催化剂。 相似文献
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乙苯氧化脱氢反应中铁酸镁,铁酸锌超微粉的催化行为 总被引:4,自引:0,他引:4
超微粉铁酸镁、铁酸锌对乙苯氧化脱氢反应具有良好的性能.300℃时能使乙苯分子活化,350℃时实现了对活性氧物种的稳定活化.反应活性氧物种被证明是O_2~-物种.其中,过量尿素爆炸分解法系本工作首创.由此法制得的D型样品具有最佳的反应性能.ESR分析表明D型样品的原子配置对称性较差. 相似文献
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氧化镍中非化学计量氧在乙烷氧化脱氢中的作用 总被引:12,自引:2,他引:12
以纯NiO为模型催化剂考察了乙烷氧化脱氢(ODHE)性能,发现非化学计量氧的存在与反应的活性及选择性密切相关.TGA研究结果表明,500℃制备的样品具有x≈6%的非化学计量氧.H2TPR结果表明,非化学计量氧与晶格氧的可还原性明显不同;O2TPDMS又把非化学计量氧区分为两个氧物种,O-2和O-(或O2-2).脉冲试验结果表明,非化学计量氧对ODHE制乙烯是选择性反应的活性氧物种,晶格氧是完全氧化反应的活性氧物种.一旦催化剂中非化学计量氧耗尽并动用晶格氧时,催化剂便有Ni0生成,表现出自催化性能,使反应活性迅速提高,但产物均为CO2,CO,CH4等完全燃烧或裂解产物.为保持有较高的乙烯收率,反应处于稳态时Ni必须处于高价态.电导测定结果表明,优良的ODHE催化剂应有P型半导性. 相似文献
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本文应用碱性气体吸附的红外光谱和TPD技术研究了FeZSM-5(F4)的酸性,酸性为:H-F4〉Fe2O3/F4〉F4原粉〉水热处理的K-F4〉Li-F4〉Na-F4〉K-F4〉NaOH/F4。比较了酸强度和积炭对乙苯氧化脱氢性能的影响,以及催化剂酸碱性质与积炭的关系。结果表明,乙苯氧化脱氢反应是在酸碱协同作用下进行的,积炭也参与了氧化脱氢反应,催化剂表面上L酸中心产生的具有一定C、H、O比的积炭 相似文献
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O. N. Krasnobaeva I. P. Belomestnykh T. A. Nosova T. A. Elizarova G. V. Isagulyants S. P. Kolesnikov V. P. Danilov 《Russian Journal of Inorganic Chemistry》2011,56(7):1012-1016
The first methods were developed for introducing tantalum(V) into Mg-Al hydrotalcites, which are precursors of oxide catalysts
for oxydehydrogenation of hydrocarbons and alcohols. Samples of oxide tantalum(V)-containing catalysts were synthesized. Their
catalytic properties were studied in the oxydehydrogenation of ethane to ethylene and ethylbenzene to styrene, oxydehydrocyclization
of octane to ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to ketone (octan-2-one). The transformation of ethane to ethylene over the tantalum-containing catalyst occurs with
a high selectivity (92–97%) at relatively low temperatures (500°C), and the catalyst is quite efficient in conversion of ethylbenzene
to styrene, dehydrocyclization of n-octane to ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to octan-2-one. Comparison with a niobium-containing catalyst showed that it ensures higher yields and selectivities
in similar reactions than its tantalum-containing analogue does. 相似文献
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O. N. Krasnobaeva I. P. Belomestnykh T. A. Nosova T. A. Elizarova G. V. Isagulyants S. P. Kolesnikov V. P. Danilov 《Russian Journal of Inorganic Chemistry》2011,56(2):168-172
The first methods are developed for introducing niobium(V) into Mg-Al hydrotalcites used as precursors of oxide catalysts
for oxydehydrogenation (OD) of alkanes and alcohols. Samples of niobium(V)-containing oxide catalysts are synthesized. Their
catalytic properties are studied in oxydehydrogenation of ethane and ethylbenzene to styrene, oxidation dehydrocyclization
of octane into ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to ketone (octane-(2)-one). It is ascertained
that ethane transformation into ethylene is highly a selective highly process (92–97%) at low temperatures (450–500°C) in
the presence of a niobium-containing catalyst; the catalyst is appreciably efficient in ethylbenzene transformation to styrene
and dehydrocyclization of n-octane to ethylbenzene and styrene, and in oxydehydrogenation of secbutanol to octane-(2)-one. All the catalysts studied
operate stably in OD reactions; no decrease in their activity or selectivity was detected after 50 h operation. 相似文献
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The oxydehydrogenation of ethylbenzene to styrene over a P−Ni−Mn catalyst, has been studied in the range of 650–770 K. The
kinetic behavior of the main reaction can be described by a redox type model and the oxidation of styrene with a power law.
The model predictions are in good agreement with the experimental observations. 相似文献
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镧-镍复合氧化物纳米微粒的固相合成及其催化性能 总被引:4,自引:0,他引:4
The La-Ni complex oxide catalyst was prepared by solid state reactions under microwave. The structure and reducibility of the catalyst were characterized by using TG-DTA, XRD, TEM and TPR methods. At the same time the catalytic activity of oxidative dehydrogenation of ethylbenzene to styrene with carbon dioxide over the complex oxide nanoparticle was investigated.The Results show that the product is K2NiF4 nanoparticles,and the size is 13nm.The complex oxide sample had high activity for the oxidative dehydrogenation of ethylbenzene to styrene. 相似文献
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神华煤流化床气化带出细粉的粒径分离及分离后细粉的CO气化特性研究 《燃料化学学报》2016,44(1):44-52
按粒径将神华煤流化床气化带出细粉(简称细粉)依次筛分为七个组分。采用工业分析仪、元素分析仪、热重分析仪、X射线粉末衍射仪、物理吸附仪等对各组分细粉的基本物化特性、CO2恒温和程序升温气化行为进行了考察。在此基础上,对气化活性差异及其原因进行初步探索。结果表明,细粉经历部分气化后,由于挥发分的析出,细粉的固定碳含量较原煤高,但较相应半焦低。细粉的粒径分布范围较宽,呈近似"M"形分布。随细粉粒径减小,灰分含量增大,而含碳量减少。CO2恒温气化与程序升温气化获得的气化反应活性顺序一致:均随细粉粒径的减小先逐渐降低而后又逐渐升高。不同细粉气化反应活性的差异与其自身的石墨化程度及灰分含量有关,而在研究实验条件下与孔径结构关系不大。 相似文献
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Monodispersed copolymer microspheres consisting of styrene and glycidyl methacrylate have been prepared by dispersion polymerization.
The effects of various polymerization parameters on the particle size and size distribution were systematically investigated.
The initial solubility parameter of the system had a significant effect on the final particle size and size distribution.
With decreasing initial solubility parameter, the particle size increased and the size distribution broadened. The particle
size decreased with increasing stabilizer concentration, the amount of styrene in the monomer mixture, and decreasing initiator
concentration.
Received: 30 September 1998 Accepted in revised form: 10 December 1998 相似文献
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Particle size in kaolinite intercalation showed an inverse reactivity trend compared with most chemical reactions: finer particles had lower reactivity and some of the fine particles cannot be intercalated. Although this phenomenon was noted in the early 1960s and several hypotheses have been reported, there is no widely accepted theory about the unusual particle size response in the intercalation. We propose that structural stress is a controlling factor in the intercalation and the stress contributes to the higher reactivity of the coarser particles. In this study, we checked the structural deformation spectroscopically and indirectly proved the structural stress hypothesis. A Georgia kaolinite was separated into nine size fractions and their intercalations by hydrazine monohydrate and potassium acetate were investigated with X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses. The apical Si-O band of kaolinite at 1115 cm(-1) shifted to 1124 cm(-1) when the mineral was intercalated to 1.03 nm by hydrazine monohydrate, and its strong pleochroic properties became much weaker. Similar reduction in pleochroism was observed on the surface OH bands of kaolinite after intercalation. Both the bending vibrations of the inner OH group at 914 cm(-1) and of the surface OH group at 937 cm(-1) shifted to 903 cm(-1) after intercalation by hydrazine. A new band for the inner OH group appeared at 3611 cm(-1) during the deintercalation of the 1.03 nm hydrazine kaolinite complex. Pleochroism change in the apical Si-O band suggested the tetrahedra had increased tilt with respect to the (001) plane. The tilt of the Si-O apical bond could occur only if the octahedra had also undergone structural rearrangement during intercalation. These changes in the octahedral and tetrahedral sheets represent some change in the manner of compensation for the structural misfit of the tetrahedral sheet and octahedral sheet. As the lateral dimensions of a kaolinite particle increases, the cumulative degree of misfit increases. Intercalation breaks the hydrogen bonds between layers and allows for the structure to reduce the accumulated stress in some other manner. The reversed size effect on intercalation probably was not caused by crystallinity differences as reported in the literature, because the Hinckley and Lietard crystallinity indices of the four clay fractions were very close to each other. Impurities, such as dickite- or nacrite-like phases are not significant in the studied sample as suggested by the XRD and IR results, they are not the main reasons for the lower reactivity of the finer particles. 相似文献