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1.
Roman Bulánek Alena Kalu?ová Michal Setni?ka Arnošt Zukal Pavel ?i?manec Jana Mayerová 《Catalysis Today》2012,179(1):149-158
The comparative study of catalytic performance of V-containing high-surface mesoporous siliceous materials (HMS, SBA-16, SBA-15 and MCM-48) in oxidative dehydrogenation of propane and n-butane (C3-ODH and C4-ODH, respectively) was carried out. The aim of study was to investigate effect of silica support texture on the speciation of vanadium complexes and its impact on catalytic behavior in both above mentioned reactions is reported. Prepared catalysts were characterized by XRF for determination of vanadium content, XRD, SEM and N2-adsorption for study of morphology and texture, and H2-TPR and DR UV-vis spectroscopy for determination of vanadium complex speciation. All prepared materials were tested in propane and n-butane ODH reaction at 540 °C and obtained catalytic results were correlated with their structural and surface characteristics. On the basis of obtained data we conclude that the structure of mesoporous silica support plays decisive role in the case of application of catalysts in n-butane ODH reaction, whereas catalytic performance of investigated catalysts in propane ODH reaction is comparable for all investigated structures. Catalytic performance of investigated materials in C3-ODH and C4-ODH can be correlated with population of all tetrahedrally coordinated VOx complexes and only isolated monomeric VOx complexes, respectively. 相似文献
2.
Raquel Ramos M. Pilar Pina Miguel Menndez Jesús Santamaría Gregory S. Patience 《加拿大化工杂志》2001,79(6):891-901
The reaction kinetics of the oxidative dehydrogenation of propane to propene over a V/MgO catalyst were studied. Both propane and propene oxidation kinetics were measured independently to quantify the rates of the parallel and consecutive reactions to propene and carbon oxides. Specific experiments to evaluate reaction products effects showed that water inhibited reaction rates but co‐feeding CO2 or propene had no measurable effect on selectivity or conversion. Kinetic data generated under integral reactor conditions and over an inert membrane reactor have also been used to estimate the kinetic parameters. Selectivity decreased as the oxygen partial pressure increased; however, propene yield was relatively insensitive to oxygen concentration. A dual site Mars‐van Krevelen model characterizes the reaction kinetics well. The role of lattice oxygen was established by alternating pulses of propane and oxygen. This redox model is able to predict the experimental tendencies observed in the three types of reactor studied. 相似文献
3.
J. Gascón 《Chemical engineering science》2006,61(19):6385-6394
The kinetics of n-butane oxidation for the production of maleic anhydride (MA) over a commercial VPO catalyst has been investigated under aerobic and anaerobic conditions and at a temperature range of 400-. A kinetic model that can be applied under both aerobic and anaerobic conditions is presented. The model considers three types of oxygen: adsorbed oxygen, surface lattice oxygen and sub-surface lattice oxygen. Both adsorbed and surface lattice oxygen are considered active for the production of maleic anhydride and COx. 相似文献
4.
Oxidative dehydrogenation of n-butane on V/MgO catalysts. Influence of the type of contactor 总被引:2,自引:0,他引:2
J. Soler J.M. López Nieto J. Herguido M. Menéndez J. Santamaría 《Catalysis Letters》1998,50(1-2):25-30
A comparative study of the catalytic performance of a selective V-Mg-O catalyst in the oxidative dehydrogenation of n-butane
is presented using three different types of reactor: (i) an adiabatic fixed-bed reactor; (ii) a fluidized-bed reactor; and
(iii) an in situ redox fluidized-bed reactor. The results obtained indicate that the in situ redox fluidized-bed reactor outperforms
the conventional fixed- and fluidized-bed reactors, especially at high n-butane conversions. Thus, a selectivity to C4 olefins of 54% at n-butane conversions of 60% was achieved at 550°C using an in situ redox fluidized-bed reactor while selectivities
to C4-olefins lower than 43% were obtained on the other reactor types under the same reaction conditions (isoconversion and reaction
temperature).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Ilya V. Mishakov Aleksey A. Vedyagin Alexander F. Bedilo Vladimir I. Zaikovskii Kenneth J. Klabunde 《Catalysis Today》2009,144(3-4):278
VOx/MgO aerogel catalysts were synthesized using three different preparation methods: by mixing the aerogel MgO support with dry ammonium vanadate, by vanadium deposition from a precursor solution in toluene, and by hydrolysis of a mixture of vanadium and magnesium alkoxides followed by co-gelation and supercritical drying. The latter aerogel technique allowed us to synthesize mixed vanadium–magnesium hydroxides with the surface areas exceeding 1300 m2/g. The synthesized catalysts were studied by a number of physicochemical methods (XRD, Raman spectroscopy, XANES and TEM). A common feature of all synthesized samples is the lack of V2O5 phase. In all cases vanadium was found to be a part of a surface mixed V–Mg oxide (magnesium vanadate), its structure depending on the synthesis method. The VOx/MgO mixed aerogel sample had the highest surface area 340 m2/g, showed higher catalytic activity and selectivity in oxidative dehydrogenation of propane compared to the catalysts prepared by impregnation and dry mixing. The addition of iodine vapor to the feed in 0.1–0.25 vol.% concentrations was found to increase to propylene yield by 40–70%. 相似文献
7.
以浸渍法制备VMo/γ-Al2O3和VMoMg/γ-Al2O3催化剂,考察其催化丙烷氧化脱氢制丙烯的反应活性,采用XRD、UV-Vis DRS和In suit IR对催化剂进行表征。结果表明,V负载质量分数为3%、Mo负载质量分数为7%时的3V7Mo/γ-Al2O3催化剂表现出较好的催化性能;添加Mg后催化剂的催化性能有所改善,反应温度500 ℃时,丙烷转化率为18.19%,丙烯选择性74.76%。丙烷和丙烯在3V7Mo/γ-Al2O3和3V7Mo4Mg/γ-Al2O3催化剂上吸附后,C—H键的H与催化剂活性中心的晶格氧发生作用形成H—O键,且3V7Mo4Mg/γ-Al2O3催化剂上出现C—O键的温度比3V7Mo/γ-Al2O3催化剂高,表明加入Mg有利于提高丙烯选择性。 相似文献
8.
研究了铜锰系催化剂并流共沉淀法的制备条件对二乙醇胺催化脱氢反应性能的影响。结果表明,在铜锰原子比为1、溶液浓度0.4 mol·L-1、沉淀pH为12、沉淀温度70 ℃、焙烧温度550 ℃和还原温度210 ℃时,催化剂性能最好。在反应温度150 ℃和压力0.8 MPa,催化剂用量为二乙醇胺质量10%的反应条件下反应 5 h,亚氨基二乙酸盐收率可达93.2%。 相似文献
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研究了沉淀方式对铜锰催化剂二乙醇胺脱氢反应性能的影响,并采用XRD和H_2-TPR分别对催化剂结构和还原性能进行了表征。结果表明,分步沉淀法制备的催化剂对二乙醇胺脱氢具有更高的活性(91.9%)和亚氨基二乙酸选择性(96.2%),有利于改善锰溶出的影响,催化剂重复使用率高。H_2-TPR研究发现,分步沉淀法制备的催化剂具有更好的还原性能;XRD测试表明,分步沉淀法有利于催化剂中CuO的分散。 相似文献
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The effect of magnesia loading and preparation procedure of vanadia on
titania catalysts on the physicochemical characteristics and the
performance in propane oxidative dehydrogenation were investigated. A
series of magnesia promoted vanadia catalyst (5 wt% V2O5) with varying amounts of MgO (1.9--10 wt%) were synthesized by
synchronous and sequential deposition on titania support. The catalysts
were characterized using several techniques (BET, XRD, H2-TPR and NH3)-TPD). Both MgO loading and preparation procedure affect the catalyst surface properties and the behavior in the oxidative
dehydrogenation of propane. Magnesia addition results in drastic
increase in propene selectivity, while the effect on activity is
negative. The activity is inversely related with the magnesia loading.
Deposition of V2O5 on previously prepared MgO/TiO2 presents a beneficial effect in the activity of the sample. The role of acidity and reducibility is explored. There is no correlation between
reducibility and activity of the catalysts, whereas the acidity seems to influence the catalytic performance. Catalyst containing 5 wt% V2O5 and 1.9 wt% MgO prepared by sequential deposition of
V2O5 on already doped with MgO titania exhibits the most interesting results. 相似文献
15.
R. Grabowski B. Grzybowska A. Kozłowska J. Słoczyński K. Wcisło Y. Barbaux 《Topics in Catalysis》1996,3(3-4):277-288
The effect of alkali metal additives Li, K, and Rb to V2O5/TiO2 catalyst on the rate of catalyst reduction with propane and reoxidation with oxygen, sorption of propene, and the electron work function has been examined. The results have been correlated with the catalytic performance in oxidative dehydrogenation, ODH, of propane. It has been found that the rates of reduction, reoxidation and the ODH of propane decrease in the order: VTi>LiVTi>KVTi>RbVTi. The activation energies of the reduction and reoxidation are not, however, affected by the presence of the alkali metals. The same sequence has been observed for the work function values of the catalysts. It is argued that alkali metal poisons the centres of the hydrocarbon activation. The yield and selectivity to propene in the ODH of propane increase, however, for the promoted catalysts, following the above sequence. This effect is ascribed to the decrease in the heat of the propene adsorption, which is due to the increase in the basicity and decrease in acidity on the promoted catalysts. 相似文献
16.
以Al2O3为载体,采用等体积浸渍法制备了负载型高分散氧化钒催化剂(12%V2O5/Al2O3),并选择Sn作为助剂对12%V2O5/Al2O3催化剂的表面性质进行调控,采用XRD、N2等温吸脱附、NH3-TPD、H2-TPR、XPS、TEM和Raman光谱等方法对催化剂进行表征,结合活性评价实验,研究了催化剂表面物种分散状态、酸性和活性物种价态的变化与异丁烷脱氢活性和稳定性之间的关系。表征结果显示,Sn对V2O5/Al2O3表面的酸性和V物种在催化剂表面的分布和价态具有一定的调节作用,当Sn质量分数为1%时,氧化锡在催化剂表面分散均匀,对表面积和孔结构影响较小,同时,表面酸性变化较小,表面低价态的钒物种增多。活性评价结果表明,该催化剂在临氢反应条件下保持了最佳的脱氢活性及稳定性,异丁烷脱氢反应480min后,异丁烷转化率为46.8%,异丁烯收率为39.8%。 相似文献
17.
F. Barbieri D. Cauzzi F. De Smet M. Devillers P. Moggi G. Predieri P. Ruiz 《Catalysis Today》2000,61(1-4):353-360
One-step non-hydrolytic condensation reactions, starting from VO(OiPr)3 and NbCl5, have been used for the first time to prepare Nb-V oxide catalysts. Different materials containing the NbVO5 phase at different purity levels have been obtained, after thermal treatments, depending on the experimental conditions. The synthetic procedure has also been applied to prepare ternary Nb-V-Si oxide systems. From preliminary catalytic reaction studies it appears that the catalysts so prepared are promising with respect to their interesting performances in the oxidative dehydrogenation (ODH) of propane. It has also been found that -Sb2O4, physically blended with the Nb-V oxide materials, could act as an appropriate promoter to improve the catalytic performances of these systems. 相似文献
18.
A.N. Zagoruiko 《Chemical engineering science》2008,63(20):4962-4968
The model simulation study has shown that the anaerobic process of oxidative dehydrogenation of propane under periodic alteration of feeding between propane and air may be realized in adiabatic catalyst beds in a stable continuous cyclic mode in a two-reactor scheme. In the case of an appropriate choice of process parameters (cycle duration and feeding flow rates) the process appears to be autothermal, i.e. it does not require any inlet gas preheating for stable operation. Compared with a similar steady-state adiabatic process, the proposed process is characterized with much lower maximum catalyst temperatures, giving the way to process pure propane without diluting it with inert gases, thus simplifying the downstream procedure of product separation. Predicted propylene yield is competitive with the one for the steady-state adiabatic process, while sufficient technological benefits of the new technology are expected (decrease in energy consumption and minimization of heat-exchange environment, process safety improvement, suppression of coke formation and efficient coke incineration). 相似文献
19.
采用共沉淀法制备铁酸锌催化剂,考察改性元素Mg、B、Zr、Ce、La对铁酸锌催化剂结构和丁烯氧化脱氢性能的影响。采用XRD、TEM和N_2吸附-脱附对镧改性铁酸盐催化剂进行金属元素组成的优化研究,确认镧元素在催化剂中存在的形态和作用。结果表明,La改性铁酸锌催化剂晶粒粒径(20~50) nm,具有较大的比表面,主要活性组分是α-Fe_2O_3和ZnFe_2O_(4,)催化剂的活性随着Fe含量的升高而升高,n(Fe)∶n(Zn)∶n(La)=4∶1∶1催化剂具有最高的催化活性,反应温度380℃时,其TOF值2.1×10~(-3) mol_(butene)·mol_(surface-Fe)·s~(-1)。 相似文献
20.
Fan Fang Zhen-shan Li Ning-sheng Cai Xiao-yu Tang Hai-tao Yang 《Chemical engineering science》2011,(6):1142
The nucleation, growth and arrangement of MgSO4 product layers during the reaction of single-crystal MgO with SO2 and O2 were investigated via atomic force microscopy (AFM). The morphology of the single-crystal MgO surface after reacting with SO2 and O2 consisted of three-dimensional cone-shaped MgSO4 product islands. Most of the islands appeared at locations with terraces, steps and kinks. With increasing reaction time, small product islands grew to large islands, finally coalescing into continuous islands. The nucleation, growth and arrangement of the solid products on the reactant surface are controlled by thermodynamics and kinetics. The morphology of the MgSO4 product islands is governed by the competition between the intrinsic chemical reaction rate and the product molecular diffusion rate, which are both significantly affected by the reaction temperature. As the reaction temperature increases, the mean size of the MgSO4 islands increases while the island density decreases. The nucleation, growth and arrangement of the solid product layers and the product layer morphology on the solid reactant surface directly affect the mechanism of the gas–solid reaction. 相似文献