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1.
Investigations on Metal Catalysts. XXVIII. Activity and Selectivity of Supported Nickel Catalysts Titania and alumina supported nickel catalysts (with 1 and 10 wt.-% Ni, resp.) have been tested in ethane hydrogenolysis and conversion of cyclohexane. Titania supported nickel and nickel on high surface aluminas are characterized by small hydrogenolysis activities and high dehydrogenation selectivities. The behaviour of the Ni/Al2O3 catalysts is discussed in terms of an interaction between small nickel crystallites and unreduced nickel. In the case of the Ni/TiO2 catalysts the interpretation is based on the partial poisoning of the nickel surface by titanium cations. 相似文献
2.
Investigations on Metal Catalysts. XXVII. On the Influence of Several Carriers on the Dispersion of Nickel Nickel supported catalysts (carrier: η-, ?-, α-Al2O3, TiO2) were characterized by chemically determined degree of reduction, CO chemisorption, magnetic susceptibility measurements and FMR. The influence of interaction between carrier and active component in the unreduced state on the size and number of Ni crystallites is discussed. 相似文献
3.
On the Dispersion of Metals in Supported Catalysts. II. Small Angle X-ray Investigation. on Platinum/Alumina and Palladium/Alumina Catalysts The metal dispersion in 0.5% Pd/A12O3. 0.5°% Pt/Al2O3 abd 1.5% Pt/Al2O3 catalysts was investigated by small angle X-ray scattering, Using a Kratky camera the difference scattering curves catalyst-carrier were evaluated. The assumption was made that the scattering centres are globular and that there is no interparticular scattering. From the Guinier approximation the Guinier radii RG of the metal particles were determined. With the Pd catalyst always positive difference scattering curves were found, whereas negative values were found with the Pt catalysts at a scattering angle greater than 0.022 rad. Therefore only for the sample with 0.5% Pd the Porod invariant \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \tilde Q}$\end{document} and the Porod radius RP could be determined. From RG and RP the parameters of a two- and of a one-parametric distribution were calculated. The results are in good agreement with data from wide angle X-ray diffraction measurements. 相似文献
4.
Investigations on Metal Catalysts. XXXII. On Alloying and Dispersion of Nickel-Rhenium Catalysts Unsupported Ni? Re catalysts were prepared by reduction of mixtures from NiO and NH4ReO4 at 400°C with hydrogen (1st series), followed by a heat treatment at 650°C in flowing hydrogen (2nd series). The bimetallic powders were characterized by DTA investigations, X-ray measurements, N2 adsorption, and CO chemisorption. The degree of alloying and the changes in dispersion as a result of adding a second metal to a basic one is discussed. 相似文献
5.
Studies on Nickel Oxide Mixed Catalysts. XVI. Reduction Behaviour of Amorphous NiO? Al2O3/SiO2 Catalysts The reduction behaviour of NiO? Al2O3/SiO2 catalysts prepared by precipitationdeposition is influenced by the phase composition (amorphous nickel layersilicates and nickel alumino layersilicates, nickel spinels, nickel oxide) and the differences of the composition between surface and bulk. TPR measurements, determinations of the reduction degree, and the nickel particle sizes by static magnetic measurements showed that the reducibility of the NiO? Al2O3/SiO2 catalysts is enhanced and the nickel dispersity is decreased at low Al2O3 contents. The decrease of the reducibility at Al2O3 contents >5 mole% is caused by the formation of nickel spinels and the decrease of the NiII ion surface concentration. 相似文献
6.
Studies on Oxide Catalysts. XLI. Redox Behavior of Nickel in Zeolites NiNa? Y. 3. Reducibility of Ni2+ Ions and Properties of the Reduced Nickel in Acidic Zeolites NiNa? Y The reducibility of nickel ions in zeolites NiNa? Y and the properties of metallic nickel were evaluated by tpr measurements, oxygen chemisorption and conversion of cyclohexane. In NiNa? Y samples which contain NH4+(H+) and/or Al3+(H+) ions the reducibility of Ni2+ ions is decreased caused by increasing acidity and the metal dispersion is improved. The electronic interaction between the acidic support and the metallic nickel leads to a decrease of both dehydrogenation and hydrogenolysis activity whereas the dehydrogenation selectivity increases. 相似文献
7.
8.
Studies on Oxide Catalysts. XXXVIII. On the Bifunctional Action of Metal Sites and Acid Sites in Metal/HNaY Zeolite Catalysts The catalytic activity and selectivity of HNaY zeolites containing nickel were investigated in the isomerization of n-hexane. In order to characterize independently the catalytic properties of the supported metal, the catalytic behaviour of these samples was determined in the dehydrogenation reaction of cyclohexane and in the hydrogenolysis of ethane. The catalytic properties of the metal in metal/HNaY zeolite catalysts are strongly modified by acid sites of the zeolite. This modification of the catalytic properties is attributed to electronic interactions between metal and zeolite. 相似文献
9.
Investigations on Metal Catalysts. XVIII. Phase Shaping, Dispersity, and Surface Composition of Ni? Cu? Re Catalysts Catalysts of the system Ni? Cu? Re reduced at 500°C consist of the following phases: only one f.c.c. phase in Ni? Cu samples, in Ni? Cu? Re samples with ≥10 at.-% Re there is an additional h.c.p. phase (pure Re). The greatest solubility in regard to rhenium (but never > 10 at.-%) was observed in the case of catalysts with a Ni:Cu ratio of 1:1. Ni? Cu? Re samples show considerably higher surface areas than the nickel sample. The catalyst Ni 45 Cu 45 Re 10 exhibits the maximum surface area. The surface layer of the crystallites is enriched with copper. 相似文献
10.
In the reaction of catalytic oxidation of CH4, CO2 with O2 to synthesis gas, carbon-deposition is an important factor for deactivation. By adding different oxides to Ni/Al2O3 catalyst, its resistance to carbon-deposition was improved. The experimental results indicate that the order of resistance
to carbon-deposition is as follows: Ni/CaO-Al2O3>Ni/MgO-Al2O3>Ni/ TiO2-Al2O3 > Ni/CeO2-Al2O3>Ni/La2O3-Al2O3>Ni/Y2O3-Al2O3>Ni/Fe2O3-Al2O3>Ni/Al2O3. The catalysts were characterized by CO2-TPD, O2-TPD and XPS methods. Here the relation between the order of resistance to carbon-deposition and performance of catalyst is
discussed. 相似文献
11.
The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present
review mainly focuses on CDR to produce synthesis gas over Ni/MOx/Al2O3 (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La2O3, MgO, and CaO have been found. The addition of promoters to Al2O3-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent
on the loading amount of promoters. For example, the highest CH4 and CO2 conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La2O3/Al2O3 catalyst, the highest CH4 conversion (96%) and CO2 conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al2O3 catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH4 conversion (91%) and CO2 conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al2O3 catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH4 conversion (89%) and CO2 conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al
for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic
performance of Al2O3-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization
of metal oxide on Al2O3 and the basic property of metal oxide to prevent carbon formation. 相似文献
12.
A New Aluminum/Nickel/Oxo‐Cluster: [Ni(acac)OAl(OtBu)2]4 When bis(tert‐butoxy)alane (tBu‐O)2AlH is allowed to react with nickeldiacetylacetonate at elevated temperature a new nickel/aluminum/oxo cluster [Ni(acac)OAl(OtBu)2]4 is formed together with aluminum acetylacetonate Al(acac)3 and some other products. The metal/oxo cluster is isolated by crystallization and structurally fully characterized by X‐ray diffraction analysis. The molecule [Ni(acac)OAl(OtBu)2]4 contains an eight membered Al4O4 cycle, to which eight mutually edge sharing NiO2Al cycles are fused. The overall point symmetry of the metal/oxo cluster is almost S4. While the aluminum atoms are tetrahedrally surrounded by oxygen ligands (mean distances Al‐O in‐between 1, 730(6) and 1, 789(6) Å)), the nickel atoms are in a square pyramidal coordination sphere of oxygen atoms (Ni‐Oaxial = 1.938(6) Å, Ni‐Obasal = 2.056(9) Å; all polyhedra are distorted). The nickel atoms have a d8 high spin electron configuration (μeff = 3.32 B.M.). 相似文献
13.
Studies on Nickel Oxide Mixed Catalysts. XI. Surface Chemical Properties of NiO/SiO2 Catalysts NiO/SiO2 catalysts with different composition prepared by precipitation have been investigated which are characterized by a nickel layersilicate-like structure. The determination of the surface chemical properties was carried out by infrared spectroscopy (before and after pyridine adsorption), 1H-NMR-measurements, chemisorption of ammonia, and titration with n-butylamine. It has been found three kinds of hydroxid groups which are assigned to Ni? OH and Si? OH groups with respect to investigations on definite nickel layersilicates. Furthermore, coordinatively unsaturated NiII surface sites were indicated. The number of the OH groups as well as the centers determined by chemisorption of bases increase with increasing NiO content. The obtained results allow the conclusion that the OH groups and the coordinatively unsaturated NiII surface sites are weakly acid. 相似文献
14.
Studies on Nickel Oxide Mixed Catalysts. XV. Surface Chemical Properties of NiO/Al2O3-SiO2 Catalysts Surface chemical properties of precipitated NiO/Al2O3? SiO2 catalysts different compositions and the corresponding Al2O3? SiO2 carriers have been investigated. Infrared spectroscopic measurements (before and after adsorption of pyridine and ammonia), 1H-n.m.r. and ammonia adsorption measurements showed that the number of the Lewis-acidic sites are increased mainly by incorporation of the nickel component on the X-ray amorphous Al2O3? SiO2 carriers, whereas the number of the hydroxide groups do not change significantly. With growing alumina content the number and the strength of the Lewis-acidic sites are increased where the part of the NiII surface sites decreases and those of the AlIII surface sites increases. Brönsted-acidic sites are detectable at high alumina contents. 相似文献
15.
Carbon dioxide reforming (CDR) of methane to synthesis gas over supported nickel catalysts has been reviewed. The present
review mainly focuses on the advantage of ceria based nickel catalysts for the CDR of methane. Nickel catalysts supported
on ceria–zirconia showed the highest activity for CDR than nickel supported on other oxides such as zirconia, ceria and alumina.
The addition of zirconia to ceria enhances the catalytic activity as well as the catalyst stability. The catalytic performance
also depends on the crystal structure of Ni–Ce–ZrO2. For example, nickel catalysts co-precipitated with Ce0.8Zr0.2O2 having cubic phase gave synthesis gas with CH4 conversion more than 97% at 800 °C and the activity was maintained for 100 h during the reaction. On the contrary, Ni–Ce–ZrO2 having tetragonal phase (Ce0.8Zr0.2O2) or mixed oxide phase (Ce0.5Zr0.5O2) deactivated during the reaction due to carbon formation. The enhanced catalytic performance of co-precipitated catalyst
is attributed to a combination effect of nano-crystalline nature of cubic Ce0.8Zr0.2O2 support and the finely dispersed nano size NiO
x
crystallites, resulting in the intimate contact between Ni and Ce0.8Zr0.2O2 particles. The Ni/Ce–ZrO2/θ–Al2O3 also exhibited high catalytic activity during CDR with a synthesis gas conversion more than 97% at 800 °C without significant
deactivation for more than 40 h. The high stability of the catalyst is mainly ascribed to the beneficial pre-coating of Ce–ZrO2 resulting in the existence of stable NiO
x
species, a strong interaction between Ni and the support, and an abundance of mobile oxygen species in itself. TPR results
further confirmed that NiO
x
formation was more favorable than NiO or NiAl2O4 formation and further results suggested the existence of strong metal-support interaction (SMSI) between Ni and the support.
Some of the important factors to optimize the CDR of methane such as reaction temperature, space velocity, feed CO2/CH4 ratio and H2O and/or O2 addition were also examined. 相似文献
16.
Studies on Oxide Catalysts. XIV. The catalytic Activity of some transient Forms of Alumina in the Dehydration of Isopropanol In order to give statements about the influence of the method of preparation of aluminum hydroxides and oxide hydroxides on the catalytic properties of alumina obtained from these compounds in the dehydration of ispropanol, bayerite, nordstrandite, and boehmite were prepared by several methods, carefully excluding impurity ions. Also, hydrargillite containing alkali was included in the investigations. By calcination in oxygen at 550 and 950°C, respectively, two groups of alumina were obtained. The catalytic properties of the oxides in the dehydration of isopropanol were examined by an apparatus working according to the dynamic principle. The specific activities of the different transient forms of alumina were found to vary according to the sequence η-;≈γ->?-≈δ->??(>??-)Al2O3. 相似文献
17.
Investigations on Metal Catalysts. XI. Investigations on Pt? η-Al2O3 Catalysts Modifieded by Iron, Cobalt, and Nickel Pt? Me? η-Al2O3 catalysts (M: Fe, Co, Ni) were characterized by magnetic investigations, reflectance spectra and determination of dispersity (chemisorption of CO, oxygen-hydrogen titration), respectively. The phase structure of platinum-rich catalysts is composed of a high degree by Pt3Fe super-structure. All the Pt? Fe? η-Al2O3 catalysts contained FeIII ions in octahedral symmetry. The dispersity of the metallic components is determined essentially by their phase structure. 相似文献
18.
Montes M. Getton F.P. Vong M.S.W. Sermon P.A. 《Journal of Sol-Gel Science and Technology》1997,8(1-3):131-137
Titania on silica samples have been prepared by: i) precipitation-deposition from a solution of TiCl3 onto the surface of a commercial silica, and ii) base catalysed hydrolysis-condensation of TEOS followed by reaction with
Ti isopropoxide. These samples were characterised by nitrogen and hydrogen adsorption, X-ray diffraction, FTIR, temperature
programmed reduction, transmission electron microscopy and catalytic activity in butane-hydrogen conversion. The sol-gel preparation
produced a better titania dispersion due to the formation of stabilising Ti-O-Si bonds. Upon these samples was then introduced
Ir. Strong metal-support interactions between Ir and titania have been observed after high temperature reduction, causing
a significantincrease in butane dehydrogenation activity relative to hydrogenolysis.It appears that using sol-gel chemistry useful supports for catalytic metals containing Si-O-Ti linkages can be produced and
in future may be optimised for other metal-oxygen metal pairs. 相似文献
19.
Dry Reforming of Methane on a Highly‐Active Ni‐CeO2 Catalyst: Effects of Metal‐Support Interactions on C−H Bond Breaking
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B. Sc. Zongyuan Liu Dr. David C. Grinter Dr. Pablo G. Lustemberg Dr. Thuy‐Duong Nguyen‐Phan Dr. Yinghui Zhou B. Sc. Si Luo Dr. Iradwikanari Waluyo Dr. Ethan J. Crumlin Dr. Dario J. Stacchiola Prof. Jing Zhou Dr. Javier Carrasco Prof. H. Fabio Busnengo Dr. M. Verónica Ganduglia‐Pirovano Dr. Sanjaya D. Senanayake Prof. José A. Rodriguez 《Angewandte Chemie (International ed. in English)》2016,55(26):7455-7459
Ni‐CeO2 is a highly efficient, stable and non‐expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal–support interactions activate Ni for the dissociation of methane. The results of density‐functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2?x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way. 相似文献
20.
SiO和AlO负载的Ni基催化剂在甲烷干重整中的催化性能差异 《燃料化学学报》2019,47(2):199-208
CH4与CO2干重整反应对于环境保护和天然气资源的合理利用具有重要意义。SiO2和Al2O3是适用于甲烷干重整反应的两种典型的催化剂载体。为了阐明这两种载体对催化剂性能的影响,本研究采用等体积浸渍法制备了Ni/Al2O3和Ni/SiO2催化剂,并利用BET、TEM、H2-TPR、XRD、TG和Raman等技术对还原和反应后的催化剂进行了表征。结果表明,由于载体的性质不同,Ni基催化剂在甲烷干重整中的催化性能也不同。Ni/SiO2催化剂的初始活性较高,但由于其金属-载体相互作用较弱,催化稳定性较差,在800℃下反应15h其催化活性急剧下降;较弱的金属-载体相互作用使得Ni/SiO2催化剂上的Ni颗粒较大,有利于积炭前驱物种的生成,导致催化剂快速失活。而对于Ni/Al2O3催化剂,金属-载体相互作用较强,Ni颗粒较小,但由于Ni与Al2O3生成了NiAlxOy物种,有效活性位减少,其催化活性相对较低,但催化稳定性较好,干重整反应进行50h其活性保持稳定;Ni与Al2O3之间较强的相互作用有利于形成小且稳定的Ni粒子,能减少积炭,因而具有优异的催化稳定性。 相似文献