共查询到20条相似文献,搜索用时 78 毫秒
1.
Catalysts based on supported 12-molybdophosphoric acid 总被引:8,自引:0,他引:8
Catalysts preparation by equilibrium adsorption of 12-molybdophosphoric acid in water–ethanol solutions onto silica, titania,
carbon and alumina is studied. The solute/support interaction follows the decreasing order: alumina, carbon, silica and titania.
It is observed that the molybdophosphoric acid keeps its Keggin-type structure after being supported at room temperature on
all supports. This species is stable up to 500°C on silica, 400°C on titania or carbon and 250°C for alumina. The acidity
of the supported heteropoly acid decreases in the following order: silica>titania>carbon>alumina.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
以中和法、水热法、醇铝法和铝粉盐酸回流法合成的氧化铝前驱体为原料分别制备球形氧化铝载体(记为ZH、SR、ST和SOL),通过强度仪、X射线荧光光谱仪(XRF)、低温氮气吸附-脱附、扫描电镜(SEM)、氨程序升温脱附(NH3-TPD)等手段对氧化铝载体进行表征,以丙烷脱氢为探针反应研究了氧化铝的制备方法对催化剂(Pt-Sn-K/Al2O3)脱氢性能的影响。实验结果表明:不同方法合成的氧化铝前驱体均制备出高强度的球形氧化铝载体,其中水热法和醇铝法制备的载体还具有较大的孔容和适中的比表面积;前驱体的制备方法对催化剂的酸性影响较大,中和法制备的氧化铝载体制备的催化剂主要是弱-中强酸中心,其他方法制备的氧化铝载体制备的催化剂为弱酸中心,催化剂酸量由大到小的顺序为ZH-CAT、SOL-CAT、ST-CAT、SR-CAT;评价结果表明,醇铝法和水热法制备的载体应用于丙烷脱氢催化剂表现出良好的性能,相当于甚至优于工业剂水平。 相似文献
3.
4.
固相反应制备Pt/C催化剂 总被引:1,自引:0,他引:1
利用固相反应法制得具有较高催化活性的Pt/C催化剂,探讨了制备条件对催化剂性能的影响。结果显示:用水作浸渍介质、n(NaOH)/n(H2PtCl6)=6 4、固相还原剂为聚甲醛时,制得的Pt/C催化剂中Pt粒子的平均粒径为3 8nm。线性扫描伏安结果表明:在30℃、扫速为50mV/s时,制得的Pt/C催化剂在c(CH3OH)=0 5mol/L和c(H2SO4)=0 5mol/L混合溶液中,甲醇氧化的峰电流密度为11 3mA/cm2;而同样条件下,E TEK公司商品化的Pt/C催化剂为9 2mA/cm2。 相似文献
5.
Angela S. Rocha Arnaldo C. Faro Jr. Laetitia Oliviero Jacob Van Gestel Franoise Maug 《Journal of Catalysis》2007,252(2):321-334
The activity of NiMoS catalysts supported on niobia, alumina, and niobia/alumina was compared for the thiophene hydrodesulfurization (HDS) and 2,6-dimethylaniline (2,6-DMA) hydrodenitrogenation (HDN) reactions. To evaluate the acidity of the supports and identify the nature of the sulfide sites, adsorption of 2,6-dimethylpyridine, pyridine, and CO was performed and followed by IR spectroscopy. This study has shown that with niobia as a support, the activity of NiMoS catalysts in thiophene HDS and in HDN of 2,6-DMA was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. Moreover, it has been shown that on a niobia/alumina support, the formation of the NiMoS phase can be directly linked to the presence of alumina not covered by niobia. However, niobia is an interesting support for the HDN of 2,6-DMA, because it favors the formation of xylene through direct ammonia elimination involving low H2 consumption. The activity for xylene formation on niobia is linked to the electron-deficient nature of the Mo sulfide site, as demonstrated by CO adsorption followed by IR. 相似文献
6.
7.
8.
采用喷雾分散-油柱成型制备方法,以硅溶胶为硅源,制备不同含量SiO2掺杂改性的微球形氧化铝载体,研究SiO2含量对氧化铝载体结构及以其为载体的负载型催化剂性能的影响。研究表明,通过掺杂SiO2有效改善了氧化铝微球的热稳定性,且氧化铝载体的孔容、比表面积及酸中心数量均随SiO2含量的增加而增加,孔径随SiO2含量的增加而减小。Pd/SiO2-Al2O3催化剂结构表征及流化床蒽醌加氢性能评价结果表明,掺杂SiO2质量分数6%时,Pd/SiO2-Al2O3催化剂氢化效率大于12.5g·L^-1,选择性大于98.3%。 相似文献
9.
Nhu Ly Katharina Al-Shamery Carine E. Chan-Thaw Laura Prati Paolo Carniti Antonella Gervasini 《Catalysis Letters》2017,147(2):345-359
Abstract
Silica and three mixed silica oxides (silica–alumina, silica–niobia, and silica–zirconia) with nominally 5 wt% of the added element (Al, Nb and Zr) were prepared and used as supports for dispersing monometallic Pt-nanoparticles. The presence of the second oxide component on the silica surface influenced some properties of the final samples, like surface area and acidity. The samples acidity was measured in a recirculation adsorption line with 2-phenylethylamine probe, by performing the titrations both in cyclohexane and in methanol to gather the intrinsic and effective acidity, respectively. The acid site density of silica–alumina was the highest compared with the other oxides; in general, an important decrease of acid sites density was determined in methanol. The order of the effective acidity in methanol was different from that determined in cyclohexane only for silica–zirconia and silica–niobia, confirming the peculiar acidity of Nb-oxide compounds in polar liquids: Colloidal spherical platinum nanoparticles were synthesized and then deposited (1 wt%) on the oxide supports. The obtained metallic nanophases were studied in the reduction of 5-hydroxymethylfurfural (HMF) to valuable chemicals such as dimethylfuran, dimethyltetrahydro-furan, 2-hexanol. In particular, this study focused on the impact of the acidity of the oxide supports on reaction selectivity when 2-butanol is used as solvent. When Pt is not present, Nb-doped silica is the most effective catalyst to di-hydroxymethyl furan diether (DHMFDE) derived from Meerwein–Ponndorf–Verley reaction, maintaining its Lewis character also in protic medium. In the presence of Pt, Nb-doped silica, however, presents the higher selectivity to hydrogenolysis products, 5-methyl furan (5-MF).Graphical Abstract
10.
采用电化学沉积法制备FePt薄膜。将氯铂酸、氯化亚铁按一定比例混合成溶液100 mL,调pH值为2.5,倒入三口烧瓶中,调节脉冲电源参数制备FePt薄膜,并通过XRD、SEM、VSM等研究薄膜的微观结构以及宏观磁性能。XRD分析表明,所制备的FePt薄膜具有面心立方(fcc)结构,在550℃热处理后转变为面心四方(fct)结构;SEM观察显示,薄膜表面颗粒呈类球形,其厚度约为5μm;VSM测试表明,所制备的FePt薄膜矫顽力趋近于0,呈现超顺磁性,热处理后其矫顽力为150 Oe,饱和磁化强度为30.78 emu/cm3。 相似文献
11.
R. Silva-Rodrigo F. Hernndez-Lpez K. Martinez-Juarez A. Castillo-Mares J.A. Melo Banda A. Olivas-Sarabia J. Ancheyta M.S. Rana 《Catalysis Today》2008,130(2-4):309-319
Ni–Mo/Al2O3–MCM-41 supported catalysts have been investigated for modification of MCM-41 by using sol–gel alumina incorporation method. Different catalysts were synthesized with variation of Si/Al molar ratios of 10, 50, 100 and 200. High specific surface area ordered meso-porous solid (MCM-41) was synthesized by using organic template method. In order to modify the low acidity of silica solid, the surface of MCM-41 was modified by incorporation of alumina. The surface acidity of solids modified significantly with variation of alumina content in the supports. The sol–gel method of alumina incorporation was used, which does not modify extensively the pore characteristics of MCM-41 material during the preparation of Al2O3–MCM-41. The X-ray diffraction intensities indicated that alumina as well as MCM-41 were present in the synthesized supports. Additionally, the hydrothermal stability of the Al2O3–MCM-41 materials was maintained up to 873 K using sever conditions like 100% water vapor stream. The catalytic activity of the catalysts was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). Selectivity was oriented mainly to the production of biphenyl (BP) and for high Si/Al ratios toward cyclohexylbenzene (CHB) and showed a higher conversion and better selectivity to hydrogenation (cyclohexylbenzene). 相似文献
12.
The acidity and surface properties of alumina modified with sulfate (A1-S) and phosphate (Al-P) were characterized by IR,
NH3TPD and 1-butene isomerization reaction. The Point of Zero Charge (PZC) of modified alumina and the amount of Mo anion adsorbed
on modified alumina were measured. The PZC of modified alumina and the amount of Mo anion adsorbed on modified alumina decreased
with increasing modifier content. Non-linear relationship between the PZC and Mo uptake in modified alumina was observed in
Al-S and Al-P. The bonding mode of sulfate on alumina changed with increasing sulfate content. The Bronsted acid site appeared
in alumina modified with sulfate of 10 wt%. 相似文献
13.
WO3/Nb2O5-supported samples prepared by impregnation are characterised by X-ray diffraction (XRD), Raman spectroscopy and X-ray absorption spectroscopy (XAS) at the W–L3 absorption edge, as well as temperature programmed reduction (TPR) and FT-IR monitoring of pyridine adsorption. Results are compared with those obtained for WO3/Al2O3 samples prepared in the same conditions, showing that niobia is able to disperse tungsta better than alumina does. Formation of a crystalline WO3 needs larger tungsten contents on niobia than on alumina, since tungsten solution into niobia is easier than into alumina. Raman and XAS spectra recorded under ambient conditions suggest that similar WOx species are formed on both supports at tungsten contents 0.5–1 theoretical monolayers; however, TPR results for the low tungsten loaded samples indicate that, when reduction starts (always at temperatures higher than 700 K under H2/Ar flow) there is a larger concentration of tetrahedral [WO4] species on alumina, than on niobia. Samples with low tungsten loading have been tested in isopropanol decomposition and ethylene oxidation, following both processes by FT-IR of adsorbed species up to 673 K. Results show that adsorption of ethylene on WO3/Nb2O5 yields acetaldehyde and acetate at 473 K, while this adsorption is non-reactive either on the supports or on WO3/Al2O3. Isopropanol adsorbs dissociatively on both supports, leading to acetone and propene formation on tungsta–niobia, but only propene on tungsta–alumina, probably due to the larger reducibility of the tungsten-containing phases. 相似文献
14.
针对第六阶段汽油国家(国Ⅵ)标准大幅度降烯烃同时保辛烷值的生产需要,本文通过改变氧化铝基质类型,制备了系列催化裂化(FCC)轻汽油芳构化催化剂,并对催化剂酸性质和织构性质进行调变。采用X射线衍射(XRD)、N2吸附脱附、扫描电子显微镜(SEM)、红外光谱(IR)和吡啶红外光谱(Py-IR)等手段对催化剂的物理性质进行表征,并以工业FCC轻汽油为原料对催化剂芳构化性能进行评价。实验结果表明,不同类型氧化铝的引入未对ZSM-5分子筛晶型产生影响,但可以显著调变ZSM-5分子筛的表面酸性,增加L酸中心数量。具有均一和相对较小比表面积和孔容的氧化铝材料更有利于轻汽油芳构化性能,轻汽油产品中,烯烃大幅下降(体积分数减少18.18%),异构烷烃(体积分数提高10.51%)和芳烃(体积分数提高2.75%)增幅较为明显,辛烷值损失(-5.1)较小并且可控。 相似文献
15.
Fenton试剂-活性炭吸附处理焦化废水的研究 总被引:4,自引:0,他引:4
对Fenton试剂-活性炭吸附联用技术处理焦化废水进行了研究。首先考察了pH值、H2O2投加量、[Fe^2+]/[H2O2]等因素对Fenton试剂氧化处理效果的影响以及Fenton试剂氧化阶段H2O2投加量对活性炭吸附效果的影响;然后考察活性炭投加量、吸附时间、pH值等因素对活性炭吸附阶段处理效果的影响。结果表明,Fenton试剂-活性炭吸附工艺处理焦化废水的最佳操作条件为:Fenton试剂氧化阶段H2O2投加量为55mmol/L,[Fe^2+]/[H2O2]=1:10,初始pH=3;活性炭吸附阶段活性炭投加量为2.5g/L,pH=3,吸附时间30min。在此操作条件下,焦化废水COD去除率达97.5%。 相似文献
16.
17.
离子交换纤维作为有潜力的吸附剂被应用,不仅在于其吸附速度,而且在于其解吸性能和重复实用性。主要以硫酸、氨水作为解吸剂,对吸附在强碱性离子交换纤维上的金属氰配合物的解吸性能进行了初步研究。实验结果表明:6%的硫酸20 m in就可使80%的Zn(CN)42-顺利地从纤维上洗脱下来,但对Cu(CN)42-的洗脱效果却不明显;氨水30 m in洗脱纤维上的Cu(CN)42-的洗脱率也达到85%以上,酸化后氰的回收率也可达85%以上,氨水解吸后,纤维上的活性基团为OH-,因此洗脱后的纤维不需要再生,直接进入后续吸附过程。离子交换纤维的解吸实验表明,离子交换纤维可有效处理含氰废水。 相似文献
18.
19.
Y. Zhang Q. Su Z. Wang Y. Yang Y. Xin D. Han X. Yang H. Wang X. Gao Z. Zhang 《化学工程与技术》2008,31(12):1856-1862
The beta zeolite on cordierite ceramic monolith was synthesized by an in situ crystallization method and characterized by XRD, N2 adsorption/desorption, SEM and NH3‐TPD techniques. Toluene adsorption/desorption was used as probe test for the control of cold‐start emissions and treatment of volatile organic compounds. The presence of beta on the supports was confirmed by XRD, SEM, and N2 adsorption/desorption measurements. The zeolite crystals grow both into the cordierite macropores and on the surface of the monolith channels, which form an integrated network ensuring a strong adherence. The highly dispersed beta on supports, demonstrated by larger surface area and adsorption capacity of N2, resulted in a significant increase of the total acidity, and thus a greater adsorption capacity for toluene. Furthermore, it could trap larger amounts of toluene to higher temperature and show considerable activity for toluene cracking and oxidation. These are attributed to the greater acidity and stronger acid sites of in situ synthesized beta. 相似文献