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采用等体积浸渍法制备了一系列不同Ni和Fe添加量的Ni-Fe/BaTiO3/γ-Al2O3双金属催化剂,并在固定床反应装置上考察了在873~1 073 K温度范围内催化剂对CO2和CH4重整反应的催化活性。实验结果表明:Ni、Fe负载质量分数均为5.0%的Ni-Fe/BaTiO3/γ-Al2O3催化剂活性最好。通过TPR、TPD和TPO表征并与单金属催化剂Ni/BaTiO3/γ-Al2O3相比,Ni-Fe/BaTiO3/γ-Al2O3催化剂具有更高的催化活性、脱附和抗积炭性能。 相似文献
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Ni/ZrO2/Al2O3催化剂在二氧化碳重整甲烷反应中,其催化活性和稳定性均优于Ni/ZrO2和Ni/Al2O3催化剂.XRD、TPD、TPR结果表明,在Ni/ZrO2/Al2O3催化剂上能形成较稳定的活性中心,负载型纳米ZrO2/Al2O3复合载体中,ZrO2以四方相形式出现,粒径为5 nm,微波和超声波的作用能诱导ZrO2和Al2O3产生新的碱性中心,有利于二氧化碳的吸附和提高活性组分的分散度.TG-DSC结果表明Ni/ZrO2/Al2O3催化剂上表面炭主要是活性较高的α炭,而Ni/ZrO2和Ni/Al2O3催化剂表面炭主要是活性较低的β炭和γ炭. 相似文献
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以γ-Al2O3为原料制备Ni-γ-Al2O3、Zn-γ-Al2O3和Al2O3载体,并采用等容浸渍法制备了钴基费-托合成用催化剂。结果表明:高温焙烧使氧化铝晶型和孔结构发生较大变化;镍添加后在载体表面形成高分散的氧化镍物种;而锌添加后与载体发生反应生成了铝酸锌;负载型催化剂中,四氧化三钴粒径大小主要取决于载体孔结构。CoPt/γ-Al2O3、CoPt/Zn-γ-Al2O3、CoPt/Ni-γ-Al2O3具有相近的费-托合成催化性能,而CoPt/Al2O3呈现出最高的催化活性和最低的甲烷选择性。表明,钴物种粒径和载体结构是影响催化剂费-托合成催化性能的主要因素。 相似文献
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以K/γ-Al2O3作催化剂,丙酸甲酯(MP)为原料高效合成了甲基丙烯酸甲酯(MMA),考察了反应温度、MP质量分数、甲醛来源、K负载量、原料摩尔比及催化剂煅烧温度对反应的影响。结果表明,反应的最佳工艺条件为:反应温度320℃,MP质量分数20%,三聚甲醛作甲醛来源,催化剂K负载量为12.5%,MP与甲醛的摩尔比为1∶1,催化剂煅烧温度为1100℃。在此条件下,MMA收率为39.2%,选择性为76.1%。进一步研究表明,随着焙烧温度的升高,Al2O3的晶型也发生转变,γ-Al2O3比α-Al2O3的活性高,K—O—Al键的生成有利于催化剂性能的提高。 相似文献
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甲烷部分氧化制合成气反应的研究 总被引:3,自引:0,他引:3
用粒度为5mm的α-Al2O3、β-Al2O3、γ-Al2O3为载体,用浸渍法制备了10%(质量)Ni基催化剂。在固定床流动反应器中,在反应温度500-850℃,大空速和不同的CH4/O2摩尔比下,测定了该催化剂用于甲烷部分氧化制合成气的活性和CO选择性。500℃用H2对催化剂还2h后,进行活性测试结果,10%Ni/β-Al2O3、Ni/γ-Al2O3对POM反应无活性,只有10%Niα-Al2O3对POM反应有活性。TPR测试结果表明,这是由于10%Ni/β-Al2O3和Ni/γ-Al2O3催化剂在700℃以下未被还原所致。另外,合成气的生成速率和CO选择尾均随反应温度和空速的增大而增大,并在CH4/O2摩尔比2时有最大值。 相似文献
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Ni对Cu-Ni/γ-Al_2O_3苯羟基化催化剂的影响 总被引:1,自引:0,他引:1
通过程序升温还原方法合成了Cu/γ-Al2O3和Cu-Ni/γ-Al2O3催化剂,使苯直接羟基化制苯酚。该反应过程中,温度和溶剂对Cu-Ni/γ-Al2O3催化剂的反应性能影响进行了探讨。采用H2-TPR、XRD、EDS等表征技术考察了Ni对催化剂结构和性质的影响。结果表明,Ni使催化剂前驱体还原温度增加、活性组分Cu单晶粒度降低、催化剂表面Cu原子数增加;当反应温度为70°C、以水作反应溶剂时,Cu-Ni/γ-Al2O3比Cu/γ-Al2O3催化剂有较高反应活性和选择性,苯转化率为32.4%,苯酚选择性为93.3%,苯酚收率为30.2%。 相似文献
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Pei Wang Chunming Wang Li Lin Yuexiang Zhu Youchang Xie 《Journal of the American Ceramic Society》2006,89(9):2744-2748
A simple method is described to prepare submicrometer α-alumina by burning carbon supported on the surface of γ-alumina in oxygen flow at a temperature of 800°C. The burning of carbon generates a large amount of heat and leads to a rapid increase in the local temperature inside the pores of alumina. When the temperature is high enough for the phase transformation, α-alumina is obtained in a very short time. It was found that, for carbon contents between 6 and 10 wt%, all the γ-alumina could transform into α-alumina after burning of carbon in oxygen for a short time, and the transformed particle sizes of α-alumina were mostly no more than 1 μm. 相似文献
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Pei Wang Li Lin Yuexiang Zhu Youchang Xie 《Journal of the American Ceramic Society》2007,90(2):402-406
Calcining carbon-covered alumina (CCA) samples at 800°C in an oxygen flow is an efficient method to prepare α-alumina powders. It is found that the pore size distribution of CCA samples, which depends on the carbon content and the pore size distribution of the precursor alumina used, is one of the key factors for the total conversion of γ-alumina to α-alumina and the complete combustion of carbon in the pores of alumina. No matter how high the carbon content, total conversion does not occur for CCA samples prepared from alumina possessing the most probable pore size of about 5.2 nm. Using γ-alumina with the most probable pore size of 6.1 nm as the precursor of CCA samples, total transformation occurs when the carbon content of CCA ranges from 11.9 to 17.3 wt%, but the color of as-prepared α-alumina is not pure white but light gray. Polyethylene glycol (PEG 20 000), added to the sucrose/γ-alumina system, can expand the pores of CCA samples after carbonization, and calcining of thus-prepared CCA results in a complete transformation of γ-alumina to pure white α-alumina with a particle size of about 1 μm when the carbon content of CCA is between 6 and 19 wt%. 相似文献
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《分离科学与技术》2012,47(14):2124-2134
Palladium doped titania nanoparticles supported on carbon-covered alumina (CCA/Pd-TiO2) impregnated polysulfone (PS) membranes were prepared by the phase inversion technique. The nano-sized CCA/Pd-TiO2 nanoparticles were uniformly dispersed in 18 wt% PS casting solution to synthesize CCA/Pd-TiO2 polysulfone membranes (PS/CCA/Pd-TiO2). The amount of the CCA/Pd-TiO2 was varied between 0.25% and 0.5% to form two types of membranes. These were casted on a non-woven fabric. The nanoparticles were added in order to enhance the photodegradation potential of the PS membranes under visible light. Raman, XRD, SEM, TGA, TGA-FTIR was used to characterize the membranes. The mechanical strength of the membranes was determined with an Instron tensile tester. The SEM results suggested that these membranes had a high degree of porosity and the nanoparticles were distributed on and within the PS membrane. The Raman analysis revealed the presence of the nanoparticles within the membrane matrix while the XRD results exposed the probability of interactions between the polymer and the nanoparticles. The two membranes were then tested for their capability to photodegrade Rhodamine B under visible light illumination. The 0.5% PS/CCA/Pd-TiO2 membrane photodegraded 80.4% of the dye while the 0.25% PS/CCA/Pd-TiO2 membrane degraded 70.8% of Rhodamine B over a 270 min period. The photodegradation followed a pseudo first-order reaction rate and the apparent rates were 0.00597 and 0.00448 min?1 for 0.5% PS/CCA/Pd-TiO2 membrane and 0.25% PS/CCA/Pd-TiO2, respectively. 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively.
There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized.
High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without
the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of
fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to
achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic
SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve
F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender
particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing,
and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing
or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually
preserves suspension stability during freezing.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago,
IL. Tied for first place in The John A. Gordon Best Paper Competition. 相似文献
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