共查询到20条相似文献,搜索用时 31 毫秒
1.
L. Chmielarz P. Kutrowski M. Michalik B. Dudek Z. Piwowarska R. Dziembaj 《Catalysis Today》2008,137(2-4):242
Vermiculites intercalated with alumina pillars and modified with transition metals (Cu, Fe) were studied as catalysts of selective reduction of NO with ammonia. Prior to the pillaring process, a raw vermiculite was treated with a solution of nitric acid and then citric or oxalic acid in order to reduce the overall charge of layers. This modification was necessary for a successful pillaring of the clay. Transition metals (Fe, Cu) were deposited on the surface of the modified vermiculites by an ion-exchange method. The obtained samples were characterized with respect to composition (EPMA), structure (XRD), texture (BET) and chemical nature of deposited transition metal species (UV–vis–DRS). The vermiculite based materials have been found to be active and selective catalysts of the DeNOx process. The Cu-containing samples were catalytically active at lower temperatures than the pillared clays modified with iron. A side reaction of ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature range. 相似文献
2.
Lucjan Chmielarz Piotr Kuśtrowski Marek Drozdek Małgorzata Rutkowska Roman Dziembaj Marek Michalik Pegie Cool Etienne F. Vansant 《Journal of Porous Materials》2011,18(4):483-491
SBA-15 mesoporous silicas modified with rhodium were studied as catalysts for the N2O decomposition reaction. Rhodium was deposited on SBA-15 by the Molecular Designed Dispersion (MDD) method using Rh(acac)3 as a precursor of active phase. The same method was used for the deposition of Cu, Fe, Al and Ti. The SBA-15 support modified
with metals were characterized with respect to metal loading (EPMA), structure (XRD), texture (BET), morphology (SEM), Rh
dispersion (oxygen chemisorption), surface acidity (pyridine adsorption) and chemical nature of introduced copper and iron
species (UV–vis-DRS). The rhodium-containing SBA-15 samples were found to be active catalysts for the N2O decomposition reaction. Deposition of Al on the Rh-loaded catalyst increased its activity. An opposite effect was observed
for the samples modified with Cu and Fe. 相似文献
3.
Alexander Moronta Tania Oberto Gabriela Carruyo Roger Solano Jorge Sánchez Eduardo González Lenin Huerta 《Applied Catalysis A: General》2008,334(1-2):173-178
A natural smectite clay (STx-1, USA) was ion-exchanged with Al, Fe or pillared with polyoxocations of the same metals. Samples were also prepared by combining these two treatments. The prepared solids were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), TPD of ammonia and N2 adsorption. The catalytic activity was evaluated by using the isomerization of 1-butene at 300 °C. XRF results showed an increase in the content of Al or Fe thus giving evidence that these metals were effectively exchanged or deposited over the starting material. Al- and Fe-pillared clays showed a significant increase of the surface area. Ion-exchanged clays showed similar surface areas to that of the starting clay. From XRD patterns only the Al-pillared clay gave an increase of the d-spacing. The synthesized pillared clays were superior catalysts for the isomerization of 1-butene than the ion-exchanged clays; the ion-exchanged/pillared clays showed a similar catalytic behavior as that of the parent pillared clays. The Al-pillared clay was the best catalyst for the reaction and its efficiency was related to the high acidity and high surface area. 相似文献
4.
Jeong Gil Seo Min Hye Youn Kyung Min Cho Sunyoung Park Sang Hee Lee Joohyung Lee In Kyu Song 《Korean Journal of Chemical Engineering》2008,25(1):41-45
An Al2O3-ZrO2 xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then
prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported
on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased
the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like
phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO2 in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support
to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the
Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG,
the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed
strong resistance toward catalyst deactivation. 相似文献
5.
In this study, the effect of annealing temperature and alumina particles on micro-hardness, corrosion, wear, and friction of Ni-P-Al2O3 composites coating is studied. The electroless nickel composite coating with various alumina particle content is deposited on a mild steel substrate. The corrosion behaviour and tribological behaviour (wear and friction) of the composite coated samples are investigated and compared with Ni-P coated samples. The micro-hardness, wear resistance, and corrosion resistance of the composite coating improved significantly after heat treatment (400 °C) and in the presence of alumina particles. The composite coating deposited with alumina particle concentration of 10 g/L in an electroless bath and heat treated at 400 °C shows excellent results compared to Ni-P, as-deposited Ni-P-Al2O3 coating and coatings heat treated at different annealing temperature (200 °C, 300 °C, and 500 °C). Microstructure changes and composition of the composite coatings due to incorporation of alumina particles and heat treatment are studied with the help of SEM (scanning electron microscopy), EDX (energy dispersive X-ray analysis and XRD (X-ray diffraction analysis). 相似文献
6.
A. Iriondo V. L. Barrio J. F. Cambra P. L. Arias M. B. Güemez R. M. Navarro M. C. Sánchez-Sánchez J. L. G. Fierro 《Topics in Catalysis》2008,49(1-2):46
Hydrogen production from glycerol reforming in liquid (aqueous phase reforming, APR) and vapor (steam reforming SR) phase over alumina-supported nickel catalysts modified with Ce, Mg, Zr and La was studied. Characterization of catalysts by temperature programmed reduction and XPS analyses revealed important structural effects: (i) the intercalation of Mg between nickel and alumina that inhibited the alumina incorporation to nickel phases, (ii) the close contact between Ni and Zr phases and, (iii) the close surface interaction of La and Ce ions with NiO phases. The catalytic activity of the samples studied in this work clearly indicated the different catalyst functionalities necessary to carry out aqueous-phase and vapor-phase steam reforming of glycerol. For aqueous phase reforming of glycerol, the addition of Ce, La and Zr to Ni/Al2O3 improves the initial glycerol conversions obtained over the Ni/Al2O3 supported catalyst. It is suggested that the differences in catalytic activities are related with geometric effects caused by the decoration of Ni phases by Ce and La or by the close interaction between Ni and Zr. In spite that nickel catalysts showed high APR activities at initial times on stream, all samples showed, independently of support, important deactivation rates that deactivate the catalysts after few hours under operation. Catalysts characterization after APR showed the oxidation of the active metallic Ni during reaction as the main cause of the observed deactivation. In the case of the glycerol steam reforming in vapor phase, the use of Ce, La, Mg and Zr as promoters of Ni based catalysts increases the hydrogen selectivity. Differences in activity were explained in terms of enhancement in: surface nickel concentration (Mg), capacity to activate steam (Zr) and stability of nickel phases under reaction conditions (Ce and La). 相似文献
7.
Jong-Soo Bae Joo-Won Park Jae-Ho Kim Jae-Goo Lee Younghun Kim Choon Han 《Korean Journal of Chemical Engineering》2010,27(5):1458-1461
The concept of “waste-to-wealth” is spreading awareness to prevent global warming and recycle the restrictive resources. To
contribute towards sustainable development, hydrogen energy is obtained from syngas (CO and H2) generated from waste gasification, followed by CO oxidation and CO2 removal. In H2 generation, it is key to produce more purified H2 from syngas using heterogeneous catalysts. In this respect, we prepared Pt/Al2O3 catalyst with nanoporous structure using precipitation method, and compared its catalytic activity with commercial alumina
(Degussa). Based on the results of XRD and TEM, it was found that metal particles did not aggregate on the alumina surface
and showed high dispersion. Optimum condition for CO conversion was 1.5 wt% Pt loaded on Al2O3 support, and pure hydrogen was obtained after removal of CO2 gas. 相似文献
8.
S. A. Kurta 《Catalysis in Industry》2011,3(2):136-143
Selecting the best catalyst for large-scale industrial processes of the oxychlorination of ethylene (OCE) is a practical task
of great importance. In such processes, even a slight reduction in selectivity results in considerable losses of raw materials.
The enhancement of selectivity requires knowledge of the structure of the catalysts’ surfaces and the mechanism of the process
of oxidative chlorination of ethylene into 1,2-dichloroethane (1,2-DCE). The structure of active sites of copper chloride
catalysts on the surface of alumina was studied by physicochemical methods of IR spectroscopy and DTA. The structure was described
for the active sites of catalysts for the oxidative chlorination of ethylene into (1,2-DCE) of two types, CuCl2 and CuCl on γ-Al2O3: H1 (Harshow, United States) and OXYMAX-B (MEDC-B) (Sǜd-Chemie Catalysts, Germany). It was ascertained that complex compounds
with [CuCl4]−2 and [CuCl2]−1 are formed upon interaction between the active phase of the catalyst (copper chlorides CuCl2 or CuCl), and the surface groups of the support γ-Al2O3 (≡Al-OH) (this observation does not fall into the known theory of their structure). In accordance with the results from our
study, a method was elaborated for synthesizing a catalyst with the optimum properties for OCE, and a pilot setup for the
detailed investigation of this process was built. The possibility of cutting ethylene losses in half during deep oxidation
and eliminating the formation of side products by a factor of 1.5–2 was demonstrated by the industrial production of 1,2-DCE
and vinyl chloride at OOO Karpatnaftokhim in Kalush. The method for producing 1,2-DCE is protected by a Ukranian patent. 相似文献
9.
C. Sepulveda R. Garcia N. Escalona D. Laurenti L. Massin M. Vrinat 《Catalysis Letters》2011,141(7):987-995
Abstract
Rhenium sulfide based catalysts were prepared by the incipient wetness impregnation method over alumina and silica supports and evaluated for 4,6-dimethyldibenzothiophene hydrodesulfurization in a high-pressure stirred-tank reactor. The catalyst prepared over silica was about six times more active for hydrodesulfurization than the corresponding catalyst prepared over alumina and a NiMo/Al2O3 industrial reference catalyst. This surprising and positive SiO2 support effect was explained by a metallic character of the supported sulfide, which was demonstrated using a kinetic approach of competitive hydrogenations and by XPS characterization. 相似文献10.
Jun-Keun Kim Younghun Kim Joo-Won Park Jong-Soo Bae Do-Young Yoon Jae-Goo Lee Jae-Ho Kim Choon Han 《Korean Journal of Chemical Engineering》2009,26(1):32-35
The water gas shift (WGS) reaction has been investigated widely in fuel cell technologies due to the potential for high fuel
efficiency and lower emissions during the production of pure hydrogen. Industrially, the WGS reaction occurs in one of the
following two ways: (a) high-temperature in the range of 310–450°C with Fe-Cr catalyst, (b) low-temperature in the range of
210–250°C with Cu-ZnO-Al2O3. In this study, a mesoporous catalyst was prepared, with a large surface area and uniformity in both pore size and distribution,
by using a one-pot synthesis method. The prepared CuO-CeO2-Al2O3 brought high CO conversion (82%), and was suitable for WGS reaction at low temperature (250 °C).
This article is dedicated to Professor Chang Kyun Choi for celebrating his retirement from the School of Chemical and Biological
Engineering, Seoul National University. 相似文献
11.
A. Katsaounis 《Journal of Applied Electrochemistry》2008,38(8):1097-1110
The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion
was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y2O3–stabilized–ZrO2 (YSZ), an O2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase
and electrochemically, as O2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives
two adsorbed atomic oxygen species desorbing at about 300 °C (state β1) and 340–500 °C (state β2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures
(Tads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times,
indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak
of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover Oads and
according to the reaction:
The formation of the spillover oxygen species is an intermediate stage before the formation of the atomic adsorbed oxygen, Oads. Mixed gaseous and electrochemical adsorption was carried out in order to simulate the Electrochemical Promotion conditions.
The initial surface coverage with oxygen from the gas phase plays a very important role on the high or low effect of polarization.
In general mixed adsorption leads to much higher oxygen coverages compare with that observed either under gaseous or electrochemical
adsorption. The binding strength of the atomic adsorbed oxygen (state β2) was investigated as a function of applied potential. It was found that the binding energy decreases linearly with increasing
catalyst potential and work function. Similar behavior has been observed for oxygen adsorption on Pt, Ag and Au deposited
on YSZ in previous studies. 相似文献
12.
Wenbing Li Dong Wan Guanghua Wang Kun Chen Qin Hu Lulu Lu 《Korean Journal of Chemical Engineering》2016,33(5):1557-1564
A novel catalyst, Fe3O4 nanoparticle decorated Al-Fe pillared bentonite (Fe3O4/Al-Fe-P-B), was prepared by in situ precipitation oxidization method. The catalyst was characterized by SEM, XRD and Raman spectroscopy. The Fe3O4 nanoparticles mainly exist on the surface or enter into the pore of bentonite, with better dispersing and less coaggregation. The catalytic activity of Fe3O4/Al-Fe-P-B was investigated in the degradation of Orange II (OII) by heterogeneous Fenton-like process. The effects of initial concentration of hydrogen peroxide, catalyst loading, temperature and initial pH on the degradation of OII were investigated. The Fe3O4/Al-Fe-P-B showed higher degradation efficiency of OII than bare Fe3O4 or Al-Fe-P-B in the degradation experiment. The enhanced catalytic activity of Fe3O4/Al-Fe-P-B in heterogeneous Fenton system was due to the synergistic effect between Al-Fe-P-B and Fe3O4. The novel catalyst can achieve solid-liquid separation easily by sample magnetic separation and has a good reusability and stability. 相似文献
13.
Nanoporous silica membrane without any pinholes and cracks was synthesized by organic templating method. The tetrapropylammoniumbromide
(TPABr)-templating silica sols were coated on tubular alumina composite support ( γ-Al2O3/ α-Al2O3 composite) by dip coating and then heat-treated at 550 °C. By using the prepared TPABr templating silica/alumina composite
membrane, adsorption and membrane transport experiments were performed on the CO2/N2, CO2/H2 and CH4/H2 systems. Adsorption and permeation by using single gas and binary mixtures were measured in order to examine the transport
mechanism in the membrane. In the single gas systems, adsorption characteristics on the α-Al2O3 support and nanoporous unsupport (TPABr templating SiO2/ γ-Al2O3 composite layer without α-Al2O3 support) were investigated at 20–40 °C conditions and 0.0–1.0 atm pressure range. The experimental adsorption equilibrium
was well fitted with Langmuir or/and Langmuir-Freundlich isotherm models. The α-Al2O3 support had a little adsorption capacity compared to the unsupport which had relatively larger adsorption capacity for CO2 and CH4. While the adsorption rates in the unsupport showed in the order of H2> CO2> N2> CH4 at low pressure range, the permeate flux in the membrane was in the order of H2≫N2> CH4> CO2. Separation properties of the unsupport could be confirmed by the separation experiments of adsorbable/non-adsorbable mixed
gases, such as CO2/H2 and CH4/H2 systems. Although light and non-adsorbable molecules, such as H2, showed the highest permeation in the single gas permeate experiments, heavier and strongly adsorbable molecules, such as
CO2 and CH4, showed a higher separation factor (CO2/H2=5-7, CH4/H2=4-9). These results might be caused by the surface diffusion or/and blocking effects of adsorbed molecules in the unsupport.
And these results could be explained by surface diffusion.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
14.
S. F. Tikhov Yu. N. Bespalko V. A. Sadykov A. N. Salanov S. I. Reshetnikov 《Combustion, Explosion, and Shock Waves》2016,52(5):535-543
The activity of plates of CuO/Al2O3/FeAlO/FeAl structured cermet catalysts is compared by varying their alumina content. The catalysts were prepared by impregnation of cermet supports obtained by mechanochemical activation of powder mixtures of an alumina precursor [20–50% (wt.)], iron, and aluminum, followed by hydrothermal treatment and calcination. It is shown that increasing the content of the alumina precursor (product of thermal activation of gibbsite) increases the specific surface area of the support and the mesopore and macropore volumes and reduces its mechanical strength. The content of the active component (CuO) also increases, resulting in an increase in the specific activity of catalyst despite a reduction in the effectiveness of using the active component. The activity of catalysts with a moderate concentration of alumina is sufficient to initiate methane oxidation. 相似文献
15.
The electrochemical promotion of the CO2 hydrogenation reaction on porous Rh catalyst–electrodes deposited on Y2O3-stabilized-ZrO2 (or YSZ), an O2− conductor, was investigated under atmospheric total pressure and at temperatures 346–477 °C, combined with kinetic measurements
in the temperature range 328–391 °C. Under these conditions CO2 was transformed to CH4 and CO. The CH4 formation rate increased by up to 2.7 times with increasing Rh catalyst potential (electrophobic behavior) while the CO formation
rate was increased by up to 1.7 times with decreasing catalyst potential (electrophilic behavior). The observed rate changes
were non-faradaic, exceeding the corresponding pumping rate of oxygen ions by up to approximately 210 and 125 times for the
CH4 and CO formation reactions, respectively. The observed electrochemical promotion behavior is attributed to the induced, with
increasing catalyst potential, preferential formation on the Rh surface of electron donor hydrogenated carbonylic species
leading to formation of CH4 and to the decreasing coverage of more electron acceptor carbonylic species resulting in CO formation. 相似文献
16.
A series of phosphotungstic acid (HPW)/SiO2 materials with hierarchical meso/macroporous structure were synthesized by evaporation-induced self-assembly method (EISA), using nonionic surfactant (P123) and polystyrene (PS) spheres as templates. SEM images displayed uniform macropores with an average pore size of 210 nm. TEM, small-angle XRD and N2 adsorption–desorption isotherms confirmed the existence of the ordered mesoporous structures, embedded in the wall of macropores. The wild-angle XRD and FT-IR spectra proved Keggin-type HPW dispersed homogeneously in the silica framework. With the amount of added PS spheres, the density of the macropores increased, the hierarchically ordered porous HPW/SiO2 possessed two-dimensional (2D) hexagonal (p6mm) mesostructures and uniform periodic macropores. The ODS catalytic activity of these samples were tested, the result showed that the meso/macroporous HPW/SiO2 catalyst with proper PS beads usage displayed much higher catalytic activity than other catalysts. In addition, the reusability of the meso/macroporous HPW/SiO2 catalyst was investigated, the activity of catalyst has not obviously decreased even after eight times. 相似文献
17.
Kyung Won La Heesoo Kim Ji Chul Jung Joohyung Lee Dong Ryul Park Sang Hee Lee In Kyu Song 《Korean Journal of Chemical Engineering》2008,25(4):710-713
Spherical carbon (SC) with a diameter of ca. 9 μm was synthesized by a hydrothermal method using sucrose as a carbon precursor.
The spherical carbon was then modified to have a positive charge, and thus, to provide a site for the immobilization of H5PMo10V2O40 (PMo10V2) catalyst. The PMo10V2 catalyst was immobilized on the surface-modified spherical carbon by taking advantage of the overall negative charge of [PMo10V2O40]5−. The PMo10V2 catalyst immobilized on the spherical carbon (PMo10V2/SC) was applied to the vapor-phase 2-propanol conversion reaction. In the catalytic reaction, the PMo10V2/SC catalyst showed a higher 2-propanol conversion than the unsupported PMo10V2 catalyst. Furthermore, the PMo10V2/SC catalyst showed enhanced oxidation catalytic activity (formation of acetone) and the suppressed acid catalytic activity
(formation of propylene and isopropyl ether) compared to the unsupported PMo10V2 catalyst. The enhanced oxidation activity of PMo10V2/SC catalyst was due to the fine dispersion of [PMo10V2O40]5− on the spherical carbon formed via chemical immobilization. 相似文献
18.
S. T. Aruna V. K. William Grips K. S. Rajam 《Journal of Applied Electrochemistry》2010,40(12):2161-2169
Electrodeposited Ni–Al2O3 composite coatings were prepared using alumina powders synthesized from solution combustion method, precipitation method
and a commercial source. Solution combustion synthesized alumina powder yielded α-phase; precipitation method yielded purely
γ-phase; commercial alumina powder was a mixture of α-, δ- and γ-phases. A nickel sulfamate bath was used for electro-codeposition.
The current densities (0.23 A dm−2 for 20 h, 0.77 A dm−2 for 6 h, 1.55 A dm−2 for 3 h and 3.1 A dm−2 for 1.5 h) and bath agitation speeds (100, 200, 600 and 1000 rpm) were varied. The pH variations of the bath were higher
during the electrodeposition of combustion synthesized alumina. The effect of different forms of alumina particles on the
microhardness and microstructure of the nickel composite coating was studied. Composite coating containing combustion synthesized
alumina particles was found to have higher microhardness (550 HK). It was found that at lower agitation speed (100 rpm), bigger
particles were incorporated and at higher agitation speed (1000 rpm), smaller particles were incorporated. The area fraction
of alumina particles incorporated in nickel matrix was highest for commercial alumina (24%). This study shows that it is not
suffice to take just the current density and stirring speeds into account to explain the properties of the coatings but also
to take into account the source of particles and their properties. 相似文献
19.
L. Chmielarz P. Kuśtrowski R. Dziembaj P. Cool E.F. Vansant 《Microporous and mesoporous materials》2010,127(1-2):133-141
SBA-15 mesoporous silica was modified with metal (Al, Ti, Cu, Fe) oxides by the molecular designed dispersion (MDD) method using acetylacetonate complexes of metals as precursors of the catalytically active components. The modified mesoporous silicas were characterized with respect to texture (BET), composition (EPMA), coordination and aggregation of transition metal species (UV–vis-DRS), reducibility of the deposited transition metals (TPRed) and surface acidity (FT-IR). Deposition of aluminium and titanium species on the SBA-15 surface significantly increased its acidity, mainly by generation of strong Lewis acid sites. Copper and iron deposited on the surface of pure SBA-15 were present nearly exclusively in the form of mononuclear cations. Deposition of Fe or Cu on the SBA-15 supports modified with alumina or titania resulted in a formation of significant amounts of oligomeric metal oxide clusters. The SBA-15 based samples have been found to be active and selective catalysts of the DeNOx process. The modification of the silica surface with titanium or aluminium prior to the deposition of iron or copper significantly improved the activity of the SBA-15 based catalysts. 相似文献
20.