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1.
Ji Chul Jung Howon Lee Heesoo Kim Young-Min Chung Tae Jin Kim Seong Jun Lee Seung-Hoon Oh Yong Seung Kim In Kyu Song 《Research on Chemical Intermediates》2008,34(8-9):827-833
Multicomponent bismuth molybdates were prepared by a co-precipitation method for use in the oxidative dehydrogenation ofn-butene to 1,3-butadiene. The effect of divalent and trivalent metals on the catalytic performance of multicomponent bismuth molybdate catalysts was investigated. It was found that the metal ratio of Fe/Bi/Mo=3∶1∶12 was favorable for the reaction. The successful formation of Ni X Co8?X Fe3Bi1Mo12O50 (X=0?8) catalysts was well confirmed by XRD and ICP-AES measurements. The multicomponent bismuth molybdate catalysts showed a better catalytic performance than the pure γ-Bi2MoO6 catalyst. Among the Ni X Co8?X Fe3Bi1Mo12O50 (X=0?8) catalysts, Ni3Co5Fe3Bi1Mo12O50 showed the highest yield of 1,3-butadiene. 相似文献
2.
Duc Truong Duc Hanh Nguyen Ha Rasmus Fehrmann Anders Riisager Minh Thang Le 《Research on Chemical Intermediates》2011,37(6):605-616
Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (??-Bi2Mo2O9) were studied to provide a better understanding about the distribution of active sites, and to elucidate the role of lattice oxygen in the reaction. The catalyst containing 50 wt% of beta bismuth molybdate on SiO2 was found to possess good distribution of active sites and sufficiently high lattice oxygen, which resulted in an extraordinary increase of the catalytic activity. 相似文献
3.
Jung-Hyun Park Hyeryeung Noh Ji Won Park Kyong Ho Row Kwang Deog Jung Chae-Ho Shin 《Research on Chemical Intermediates》2011,37(9):1125-1134
A series of BiMoFe0.65P
x
oxide catalysts with varying phosphorous contents from 0.0 to 0.6 mol ratio were prepared by a co-precipitation method, and
oxidative dehydrogenation (ODH) was carried out to produce 1,3-butadiene (BD) from n-butenes. The physico-chemical properties of the oxide catalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy,
N2 sorption, and NH3 and 1-butene temperature-programmed desorption (TPD). Among the catalysts studied here, BiMoFe0.65P0.1 oxide catalyst showed the highest conversion and selectivity to BD. From the result of 1-butene TPD, the higher catalytic
activity is related to the amount of weakly bounded intermediate and the desorbing temperature of strongly bounded intermediates.
Also, the higher catalytic activity likely originates from the acidity of the BiMoFe0.65P0.1 oxide catalyst; its acidity was higher than that of phosphorous-free oxide catalyst and further contained other oxide catalysts.
BiMoFe0.65P0.1 oxide catalyst is stable and no significant deactivation for 100 h ODH reaction was shown. 相似文献
4.
M. Hartmanova M. T. Le M. Jergel V. Šmatko F. Kundracik 《Russian Journal of Electrochemistry》2009,45(6):621-629
The investigated bismuth vanadate, BiVO4, bismuth vanadomolybdate, Bi0.85V0.55Mo0.45O4, and pure bismuth molybdate, Bi2Mo3O12, oxides prepared by novel spray drying technique having the scheelite structure were found to be monoclinic in the case of
BiVO4 and Bi2Mo3O12, whereas Bi0.85V0.55Mo0.45O4 is body-centered tetragonal. The distribution of intergranular porosity across polycrystalline samples is inhomogeneous,
being larger parallel to the flat compression of the powder samples. The high polarizability of Bi3+ cations with their lone-pair electrons influences stability of the disordered oxygen sublattice. All as-prepared systems
undergo a slight structural change of the oxygen arrangement during the sample heating in the temperature region of 340–390°C,
probably due to an order ⇆ disorder transition, resulting in a decrease of lattice oxygen ion mobility and decrease of electrical
conductivity. The total bulk electrical conductivity of both vanadate systems is essentially ionic at low temperatures and
high oxygen partial pressures. Diffusion of the lattice oxygen ions in the Bi1−x/3V1−x
Mo
x
O4 scheelite structure is indirectly related to the introduction of cation vacancies. The highest conductivity was observed
in the multicomponent oxide Bi0.85V0.55Mo0.45O4, both as-prepared and thermally treated. Above 350°C the conductivity of BiVO4 and partially also Bi0.85V0.55Mo0.45O4 oxides is affected by the n-type electron contribution.
Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 6, pp. 659–667.
The article is published in the original.
Published by report at IX Conference “Fundamental Problems of Solid State Ionics”, Chernogolovka, 2008. 相似文献
5.
1,3-Butadiene, an important raw material for a variety of chemical products, can be produced via the oxidative dehydrogenation (ODH) of n-butenes over multicomponent oxide catalysts based on bismuth molybdates and ferrites. In this review, the basic concept, reaction mechanism, and catalysts typically used in an ODH reaction are discussed. 相似文献
6.
The formation ofβ-phase Bi2Mo2O9 catalyst from a precursor precipitate has been studied using thein situ combined XRD/QuEXAFS technique and DSC during calcination. Accordingly the precursor was observed to undergo a number of
changes in both the molybdenum (VI) coordination and long-range ordering during this heating. Initially the two other forms
of bismuth molybdate (α-andγ-phases) were observed to form from the poorly crystalline precursor at about 230°C, however, theβ-phase eventually crystallised after prolonged heating at 560°C.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
7.
The texture of Cr2O3-K2O/Al2O3catalysts containing oxides of rare earth elements (REE) was studied. The catalysts are used for the synthesis of 2-methylthiophene by the reaction of H2S with n-pentane or piperilene. The heterocyclization of n-pentane is a consecutive reaction involving a step of dehydrogenation of initial hydrocarbon. At this step the texture of the catalyst affects the yield of 2-methylthiophene. The yield of 2-methylthiophene obtained from piperilene and I2S is independent of the catalyst texture. 相似文献
8.
Tae-Sun Chang Dong-Koo Lee Deug-Hee Cho Sock-Sung Yun 《Reaction Kinetics and Catalysis Letters》2003,78(1):35-40
The effect of compositions of silica-alumina support on multicomponent bismuth phosphate catalyst (MBP) was investigated for
the propylene ammoxidation. It is appears that small amounts of Al2O3 cause retardation of the ammoxidation reaction, which would be due to activation of the selective oxidation pathway. It is
understood from such results that the catalytic action of the MBP is essentially different with that of the multicomponent
bismuth molybdate catalyst (MBM), which is generally used as propylene ammoxidation catalyst.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
10.
采用水热法一步合成二氧化铈/钼酸铋复合材料,进一步探究了不同酸碱性反应体系溶液中二氧化铈与钼酸铋的组成、结构和光催化性能的关系。运用X射线衍射分析仪、扫描电子显微镜、傅里叶变换红外光谱仪、紫外-可见漫反射光谱仪等对样品进行表征。研究发现CeO_2的加入与钼酸铋在不同酸碱性合成体系合成产物的形态、组成、结构及光催化性能息息相关。未加Ce~(3+)前,在酸性条件下反应生成的是Bi_2MoO_6;在碱性条件下的反应产物是Bi_(3.64)Mo_(0.36)O_(6.55)/Bi_2MoO_6复合材料。当合成的反应溶液体系中引入CeO_2之后,在酸性条件下反应生成的Bi_2MoO_6催化性能最好;在碱性条件下,反应生成的是Bi_(3.64)Mo_(0.36)O_(6.55)。因此,在碱性条件下,CeO_2的加入能够促进Bi_2MoO_6转化Bi_(3.64)Mo_(0.36)O_(6.55)。 相似文献
11.
El-Sayed A. El-Sharkawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(12):1487-1498
Summary. The textural characteristics, including surface area, mean pore diameters, and total pore volume of Cr2O3–CuO/Al2O3 solid catalysts were determined from the low temperature adsorption of N2 at 77 K. The structural properties were investigated using XRD. The surface acidity of calcined samples was determined using
two comparable methods, including the non-aqueous titration of acidic groups with n-butylamine and dehydration/dehydrogenation activity of cyclohexanol.
XRD patterns assigned a crystalline CuO and γ-Al2O3 for 723 K calcinations products of lower Cr2O3 content. The gradual increase of calcinations temperature promoted the crystallinity of Cr2O3 and resulted in solid–solid interaction of CuO and Cr2O3 forming CuCr2O4. The textural parameters varied with both calcinations temperature and catalyst composition. The surface acid density (DAS)
increased with the increase of chromia content up to 0.132 mole% Cr2O3, while the rise of calcinations temperature led to a decrease of surface acidity.
The dehydration/dehydrogenation of cyclohexanol as well as n-butylamine titration succeeded in characterizing of surface acidity.
Present address: Chemistry Department, College of Science, King Faisal University, Al-Hofuf 31982, Saudi Arabia 相似文献
12.
In Situ IR Spectroscopic Studies on Molybdenum Nitride Catalysts: Active Sites and Surface Reactions
Recent IR spectroscopic studies on the surface properties of fresh Mo2N/-Al2O3 catalyst are presented in this paper. The surface sites of fresh Mo2N/-Al2O3, both Mo+ (0<<2) and N sites, are probed by CO adsorption. Two characteristic IR bands were observed at 2045 and 2200 cm-1, due to linearly adsorbed CO on Mo and N sites, respectively. The surface N sites are highly reactive and can react with adsorbed CO to form NCO species. Unlike adsorbed CO on reduced passivated one, the adsorbed CO on fresh Mo2N/-Al2O3 behaves similarly to that of group VIII metals, suggesting that fresh nitride resembles noble metals. It is found that the surface of Mo nitrides slowly transformed into sulfide under hydrotreating conditions, which could be the main reason for the activity drop of molybdenum nitride catalysts in the presence of sulfur-containing species. Some surface reactions, such as selective hydrogenation of 1,3-butadiene, isomerization of 1-butene, and hydrodesulfurization of thiophene, were studied on both fresh and reduced passivated Mo2N/-Al2O3 catalysts using IR spectroscopy. The mechanisms of these reactions are proposed. The adsorption and reaction behaviors of these molecules on fresh molybdenum nitride also resemble those on noble metals, manifesting the unique properties of fresh molybdenum nitride catalysts. Mo and N sites are found to play different roles in the adsorption and catalytic reactions on the fresh Mo2N/-Al2O3 catalyst. Generally, Mo sites are the main active sites for the adsorption and reactions of adsorbates; N sites are not directly involved in catalytic reactions but they modify the electronic properties of Mo sites. 相似文献
13.
O. V. Udalova D. P. Shashkin M. D. Shibanova O. V. Krylov 《Kinetics and Catalysis》2005,46(4):535-544
The role of various components of a multiphase oxide catalytic system in the partial oxidation of propylene to acrolein is investigated. Catalytic activity is studied for the Co6–8Mo12Fe2–3Bi0.5–0.75Sb0.1K0.1Ox catalyst, which is taken to be the reference, and for catalysts in which the amount of some component is progressively reduced down to zero. The results obtained provide insights into the role of the components of the catalyst.CoMoO4 forms the structural framework of the catalyst. Iron molybdate can be stabilized on CoMoO4 as β-phase. As its content is increased, the catalyst gains activity but its selectivity declines. Bismuth molybdate is responsible for the selectivity of the process. When present in small amounts, MoO3 raises the selectivity, binds free oxides, and converts reduced molybdates into their oxidized forms. Excess molybdenum trioxide causes a dramatic fall in the catalytic activity. Potassium and antimony decrease the catalytic activity, but even small amounts of these elements raise the selectivity of the catalyst. Chromium can substitute for iron atoms in the multicomponent catalyst. Ni, Mn, and Mg substitute for Fe in iron molybdate to decrease the catalytic activity.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 569–579.Original Russian Text Copyright © 2005 by Udalova, Shashkin, Shibanova, Krylov. 相似文献
14.
15.
Elka Kraleva Alla Spojakina Rumiana Edreva-Kardjieva Kveta Jiratova Lacezar Petrov 《Reaction Kinetics and Catalysis Letters》2007,92(1):111-119
HDS catalysts were prepared by loading H3PMo12O40 or H4PMo11V1O40 polyoxometallates on TiO2 (0.5 and 1.0 mmol (Mo+V)). Activity of the catalysts was tested in the HDS of thiophene. The activity of catalysts of low
concentration was 2–3 times higher than the activity of those of high concentration. Temperature programmed reduction (TPR)
and IR spectroscopy were used to determine the properties of the catalyst. TPR measurements proved that vanadium promotes
and stabilizes HDS activity due to an increase in the Mo5+/Mo4+ ratio. 相似文献
16.
A. Martínez-de la Cruz S. Obregón Alfaro S. M. G. Marcos Villarreal 《Research on Chemical Intermediates》2010,36(8):925-936
Nanoparticles of α-Bi2Mo3O12 were prepared by the Pechini method. The process of formation of the bismuth molybdate was followed by simultaneous thermogravimetric and differential thermal analysis (TGA/DTA). Different samples of α-Bi2Mo3O12 were obtained at 400, 450, and 500 °C, and characterized by X-ray powder diffraction (XRD), nitrogen physisorption (BET), and scanning electron microscopy (SEM). When observed by SEM, the morphology of the sample obtained at the lowest temperature consisted of semi-spherical particles with an average diameter of 150 nm. On the other hand, the highest calcination temperature led to the formation of sintered particles of 500–600 nm. The photocatalytic activity of α-Bi2Mo3O12 was tested by photodegradation of the organic dyes rhodamine B (rhB) and indigo carmine (IC) under visible-light irradiation. The bismuth molybdate nanoparticles were able to bleach aqueous solutions of both organic dyes. The sample obtained at 400 °C was the best photocatalyst with half-lives, t 1/2, of 108 and 154 min for rhB and IC, respectively. 相似文献
17.
Yingxin Liu Zuojun Wei Jiyan Zhang Wei Yan 《Reaction Kinetics and Catalysis Letters》2007,92(1):121-127
Ni-La2O3-SiO2 catalysts were prepared by wetness impregnation and sol-gel method followed by conventional drying and supercritical drying,
respectively. Their physico-chemical properties and activity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine were investigated by BET, XRD, TPR, H2-TPD and activity tests. The results showed that the structural and catalytic properties of the Ni-La2O3-SiO2 catalysts obviously depended on the preparation method and the drying mode. The catalyst prepared by the sol-gel method in
combination with conventional drying exhibited the highest catalytic activity among the catalysts tested, attributable to
its well-dispersed nickel particles and larger active nickel surface area. 相似文献
18.
Nanostructured cobalt molybdate catalysts supported on mesoporous silica SBA-15 with different loadings were prepared by citric acid coordination-impregnation method and characterized by XRD, TEM, and BET techniques. The characterization results showed that high loading of well-dispersed crystalline CoMoO4 may be achieved using citric acid coordination-impregnation method and the mesoporous structure of the support remained intact. The catalytic activity of these catalysts in the oxidative dehydrogenation of propane was investigated. The catalysts of nanostructured cobalt molybdate supported on mesoporous silica SBA-15 showed better catalytic performance than the corresponding bulk composite oxide and nanostructured CoMoO4 supported on SBA-15 with loading of 13% (mass fraction, w) displayed propene yield of 16.8% at 823 K. 相似文献
19.
Highly dispersed molybdena-titania catalyst can be prepared by an equilibrium adsorption method. In this method, molybdate
anions adsorb onto the positively charged titania surfaces via electrostatic attraction by controlling the pH of the impregnating
solution and they increase as an inverse function of the pH. 95Mo-NMR and UV spectroscopic studies of impregnating solution show that the polymeric species like Mo7O24
6-ions are adsorbed on titania in the acidic impregnating solution. XRD, Raman, and XPS data of the calcined samples show that
mono-layer coverage of molybdenum oxide over-layer possesses a highly distorted MoO6 group with a molecular geometry resembling the distorted square pyramid.
The catalytic oxidation of methanol over the surface molybdate species on titania possesses higher turnover numbers and higher
selectivities of partial oxidation products than the catalysts supported on alumina, silica, zirconia, or magnesia. Changes
of the surface properties either after reduction and sulfiding treatment over monolayer catalyst on titania have also been
investigated. The NO chemisorption and XPS studies show that two types of active sites appeared after reduction treatment:
one site is active for hydrogenation of 1,3-butadiene and the other site is active for metathesis of propene. A higher degree
coordinative unsaturations of MO is required for hydrogenation than metathesis. After sulfiding treatments of the catalyst,
hydrogenation of 1,3-butadiene also requires triply coordinative unsaturation, and hydrogenolysis of thiophene requires the
ensemble of doubly or triply coordinative unsaturations. 相似文献
20.
用沉积沉淀法合成两种不同系列的CeO2-ZrO2-La2O3混合氧化物(ZrO2和La2O3沉积CeO2粒子(标记为A-x)以及CeO2和La2O3沉积ZrO2粒子(标记为B-x)),并用作Rh催化剂的载体。XRD、拉曼、TPR、XPS和O2脉冲等表征结果显示出不同的沉积顺序将导致不同的结构和氧化还原性能,且B-x具有更高的氧迁移性、储氧能力和表面Ce浓度。当其负载Rh后,Rh/B-x催化剂具有更高的NO和CO转化率及N2选择性,且Ce的最佳含量为50at%。这可能归因于Rh负载于富铈表面形成更多有利于NO分解的表面Ce3+活性位。 相似文献