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1.
Ion-exchanged pillared clays (PILCs) were studied as catalysts for selective catalytic reduction (SCR) of NO by ethylene. Three most important pillared clays, Al 2O 3-PILC (or Al-PILC), ZrO 2-PILC (or Zr-PILC) and TiO 2-PILC (or Ti-PILC), were synthesized. Cation exchanges were performed to prepare the following catalysts: Cu–Ti-PILC, Cu–Al-PILC, Cu–Zr-PILC, Cu–Al–Laponite, Fe–Ti-PILC, Ce–Ti-PILC, Ce–Ti-PILC, Co–Ti-PILC, Ag–Ti-PILC and Ga–Ti-PILC. Cu–Ti-PILC showed the highest activities at temperatures below 370°C, while Cu–Al-PILC was most active at above 370°C, and both catalysts were substantially more active than Cu-ZSM-5. No detectable N 2O was formed by all of these catalysts. H 2O and SO 2 only slightly deactivated the SCR activity of Cu–Ti-PILC, whereas severe deactivation was observed for Cu-ZSM-5. The catalytic activity of Cu–Ti-PILC was found to depend on the method and amount of copper loading. The catalytic activity increased with copper content until it reached 245% ion-exchange. The doping of 0.5 wt% Ce 2O 3 on Cu–Ti-PILC increased the activities from 10% to 30% while 1.0 wt% of Ce 2O 3 decreased the activity of Cu–Ti-PILC due to pore plugging. Cu–Ti-PILC was found to be an excellent catalyst for NO SCR by NH 3, but inactive when CH 4 was used as the reducing agent. Subjecting the Cu–Ti-PILC catalyst to 5% H 20 and 50 ppm SO 2 at 700°C for 2 h only slightly decreased its activity. TPR results showed that the overexchanged (245%) PILC sample contained Cu 2+, Cu + and CuO. The TPR temperatures for the Cu–Ti-PILC were substantially lower than that for Cu-ZSM-5, indicating easier redox on the PILC catalyst and hence higher SCR activity. 相似文献
2.
针对目前空调用有机相变蓄冷材料热导率低的问题,将具有高导热性的纳米材料(MWNTs、Al 2O 3、Fe 2O 3)添加到所开发制备的二元复合有机蓄冷材料(质量比73.7:26.3的辛酸/肉豆蔻醇)中,从纳米材料的种类和浓度两方面,研究其对复合有机蓄冷材料热物性的影响。实验发现:对于MWNTs、Al 2O 3、Fe 2O 3 3种纳米材料,当其质量分数分别小于0.3%、0.4%、0.8%时,对应纳米复合材料热导率随纳米材料浓度的增加幅度较为明显;与原二元复合有机相变蓄冷材料相比,添加0.3%的MWNTs,热导率提高26.3%;添加0.4%的Al 2O 3,热导率提高13.1%;添加0.8%的Fe 2O 3,热导率提高32.1%;当在一定纳米材料质量分数(如0.7%)下,加入纳米颗粒的复合材料导热性能效果依次为Fe 2O 3>MWNTs>Al 2O 3。不同纳米粒子的添加对原蓄冷材料的相变温度和相变潜热影响很小,相变温度变化波动最大为0.4℃,相变潜热变化波动范围最大为1.4%。 相似文献
3.
The gas-phase oxidative dehydrogenation of ethylbenzene to styrene was carried out by using as catalyst a series of metal phosphates (Al, Fe, Ni, Ca and Mn) and stoichiometric (Al/Fe = Al/Ca = 1) mixed systems: FeAl(PO 4) 2 and Ca 3Al 3(PO 4) 5, that were prepared by an ammonia gelation method. Their amorphous character was determined through several physical methods: nitrogen adsorption, DRIFT and XRD patterns. These results were compared to those obtained with 24 commercial inorganic solids (several metal oxides, sulfates and phosphates). Reactions were also carried out without oxygen, under non-oxidative conditions, where the catalytic activity was always appreciably lower than under oxidative conditions. Experimental results indicated that the oxidative gas-phase dehydrogenation of ethylbenzene to styrene could be related to the total number of acid and basic sites of catalysts, so that this reaction probably needs selected acid–basic pairs for coke formation, where the oxidative dehydrogenation process is developed. The main practical conclusion of the catalyst screening was that the best results were obtained with the synthesized amorphous AlPO4, where 43% ethylbenzene conversion and 99.7% styrene selectivity were achieved. A very reduced number of commercial inorganic solids like Al2(SO4)3, Cr2(SO4)3, Fe2(SO4)3, NiSO4, Al2O3 and Fe2O3 were also able to obtain an acceptable catalytic behavior, with conversions ranging between 18 and 23% and selectivity in the 95–100% range. Among the other synthesized solids, Ni3(PO4)2-A-450 was the only metal phosphate exhibiting results in such a range. All the other catalysts studied were rather inactive and/or selective. Additional experiments carried out at longer times on stream (3.5 h) and longer contact times (W/F 0.254 and 0.654) confirmed the superior catalytic behavior of amorphous AlPO4. Consequently, this solid could be a good candidate for application as a catalyst in the industrial oxydehydrogenation of ethylbenzene to styrene. 相似文献
4.
Both iron oxide (Fe 2O 3) and iron carbide catalysts are active for the dehydration of tertiary alcohols; the oxide catalyst is not reduced nor is the bulk carbide oxidized by the steam generated during the dehydration reaction. Secondary alcohols are selectively converted to ketones plus hydrogen by both the iron oxide and carbide catalyst. Fe 2O 3 is reduced to Fe 3O 4 during the conversion of secondary alcohols. Both iron carbide and oxide catalysts dehydrogenate a primary alcohol (C n) to an aldehyde which undergoes a secondary ketonization reaction to produce a symmetrical ketone with 2 n−1 carbons. These results plus those of our earlier 14C-tracer studies suggest that dehydration of alcohols to produce olefins makes a minor, if any, contribution during Fischer–Tropsch synthesis with an iron catalyst at low and intermediate pressure conditions. 相似文献
5.
Hydropyrolysis of a mixture of Alberta coal and Athabasca bitumen was carried out in a batch reactor using calcium oxide as an alternate catalyst and the results were compared with those of widely used iron oxide and well-known NiMo/Al 2O 3 catalysts. Most of the reactions were done at temperatures of 500–540°C, residence time of 1 min and hydrogen pressure of 3.4 MPa. Maximum distillable oil (below 523°C) yield of 55 wt% and pitch conversion of 62 wt% were obtained in the presence of CaO or Fe 2O 3 and these values were higher than those without catalyst, although NiMo/Al 2O 3 catalyst gave much higher oil yield and pitch conversion. Catalyst concentration (above 2 wt%) has no consequence upon the distribution of various product fractions. In another study, addition of 15% toluene to the feed in the absence of catalyst led to higher distillable oil yield (68 wt%) and pitch conversion (72 wt%) in the hydroconversion of coal and bitumen mixture. Increase in toluene concentration from 15 to 50 wt% had no positive effect on the product yields. 相似文献
6.
本文以Fe 2O 3、l 2O 3粉体为原料,在室温进行高能球磨,然后热压烧结制备(Fe,Al) 2O 3单相固溶体。对单相固溶体在H 2气氛下进行热处理,使固溶的Fe选择性还原析出为分散于Al 2O 基体中的金属颗粒。利用XRD、TEM分析还原产物,研究还原产物的物相,并观察还原后铁在氧化铝基体中的分布情况。 相似文献
7.
考察了分别采用15%NH 4Cl+35%ZnCl 2、25%NH 4Cl+25%ZnCl 2和20%NH 4Cl+30%ZnCl 2助镀时,304不锈钢热浸镀Al-x%Si-0.5%RE(x=1,3,6,9)镀层的厚度与截面形貌。结果表明,采用25%NH 4Cl+25%ZnCl 2助镀后,镀铝层厚度最大且均匀,与基体的结合面较平直,无分层和不连续现象。经X射线衍射分析,镀层的外表层由Al 2O 3、SiO 2和α-Al组成,次外层由Al 2O 3、SiO 2以及FeAl 2、FeAl、Fe 2Al 5组成,内层主要由Fe 2Al 5和FeAl3组成。 相似文献
8.
In reverse water gas shift (RWGS) reaction CO 2 is converted to CO which in turn can be used to produce beneficial chemicals such as methanol. In the present study, Mo/Al 2O 3, Fe/Al 2O 3 and Fe-Mo/Al 2O 3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, inductively coupled plasma atomic emission spectrometer (ICP-AES), temperature programmed reduction (H 2-TPR), CO chemisorption, energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. Kinetic properties of all catalysts were investigated in a batch reactor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/Al 2O 3 catalyst enhances its activity as compared to Fe/Al 2O 3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/Al 2O 3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fe 2(MoO 4) 3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fe 2(MoO 4) 3 phase has low reducibility, therefore the Fe 2(MoO 4) 3 phase signifificantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al 2O 3 catalyst. Overall, this study introduces Fe-Mo/Al 2O 3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction. 相似文献
9.
The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 °C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl 2O 4·10H 2O converted to Ca 3Al 2(OH) 12 and amorphous aluminum hydroxide. Ca 2Al 2O 5·8H 2O transformed via the intermediate phase Ca 4Al 2O 7·13H 2O to Ca 3Al 2(OH) 12 and gibbsite, Al(OH) 3. The phase Ca 4Al 2O 7·19H 2O reacted via the same intermediate phase to Ca 3Al 2(OH) 12 and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported. 相似文献
10.
Ag-based catalysts supported on various metal oxides, Al 2O 3, TiO 2, and TiO 2–Al 2O 3, were prepared by the sol–gel method. The effect of SO 2 on catalytic activity was investigated for NO reduction with propene under lean burn condition. The results showed the catalytic activities were greatly enhanced on Ag/TiO 2–Al 2O 3 in comparison to Ag/Al 2O 3 and Ag/TiO 2, especially in the low temperature region. Application of different characterization techniques revealed that the activity enhancement was correlated with the properties of the support material. Silver was highly dispersed over the amorphous system of TiO 2–Al 2O 3. NO 3− rather than NO 2− or NO x reacted with the carboxylate species to form CN or NCO. NO 2 was the predominant desorption species in the temperature programmed desorption (TPD) of NO on Ag/TiO 2–Al 2O 3. More amount of formate (HCOO −) and CN were generated on the Ag/TiO 2–Al 2O 3 catalyst than the Ag/Al 2O 3 catalyst, due to an increased number of Lewis acid sites. Sulfate species, resulted from SO 2 oxidation, played dual roles on catalytic activity. On aged samples, the slow decomposition of accumulated sulfate species on catalyst surface led to poor NO conversion due to the blockage of these species on active sites. On the other hand, catalytic activity was greatly enhanced in the low temperature region because of the enhanced intensity of Lewis acid site caused by the adsorbed sulfate species. The rate of sulfate accumulation on the Ag/TiO 2–Al 2O 3 system was relatively slow. As a consequence, the system showed superior capability for selective adsorption of NO and SO 2 toleration to the Ag/Al 2O 3 catalyst. 相似文献
11.
Water–gas shift reaction was studied over two nanostructured Cu xCe 1−xO 2−y catalysts: a Cu 0.1Ce 0.9O 2−y catalyst prepared by a sol–gel method and a Cu 0.2Ce 0.8O 2−y catalyst prepared by co-precipitation method. A commercial low temperature water–gas shift CuO–ZnO–Al 2O 3 catalyst was used as reference. The kinetics was studied in a plug flow micro reactor at an atmospheric pressure in the temperature interval between 298 and 673 K at two different space velocities: 5.000 and 30.000 h −1, respectively. Experimentally estimated activation energy, Eaf, of the forward water–gas shift reaction at CO/H 2O = 1/3 was 51 kJ/mol over the Cu 0.1Ce 0.9O 2−y, 34 kJ/mol over the Cu 0.2Ce 0.8O 2−y and 47 kJ/mol over the CuO–ZnO–Al 2O 3 catalyst. A simple rate expression approximating the water–gas shift process as a single reversible surface reaction was used to fit the experimental data in order to evaluate the rate constants of the forward and backward reactions and of the activation energy for the backward reaction. 相似文献
12.
Alumina–titania supports containing 5–50 wt.% of TiO 2 were prepared by coprecipitation method using inorganic precursors (sodium aluminate and titanium chloride). DTA-TGA, XRD, SEM, TPD NH3, and IR spectroscopy were used to characterise these materials. The study shows that the promoting effect of nickel on the HDS activity of molybdenum catalysts supported on Al 2O 3TiO 2 is significantly lower than that for molybdenum catalyst supported on Al 2O 3, and depends on the TiO 2 content. The SEM results show that in the case of rich Al support (20 wt.% of TiO 2) molybdenum was aggregated on the external surface of the catalyst, whereas it was uniformly dispersed on the external surface of alumina. Results also show that molybdenum is preferably supported on aluminum oxide. Application of Al 2O 3TiO 2 oxides enhances the HDN activity of nickel–molybdenum catalysts. The highest HDN efficiency was obtained for the NiMo/Al 2O 3TiO 2 catalyst containing 50 wt.% of TiO 2. HDN activity was found to depend on protonic acidity and anatase content. 相似文献
13.
包覆型Fe 2O 3/SiO 2颜料由于包覆完整性并不理想,该颜料高于800 ℃时呈色会产生变黑、变暗的问题。采用溶胶-凝胶法制备包覆型Fe 2O 3/SiO 2颜料,研究催化剂浓度、反应温度、硅/铁质量比等因素对包覆型Fe 2O 3/SiO 2颜料呈色性能的影响。在此基础上,通过掺加Zn 2+,进行了Zn 2+掺加的包覆型Fe 2O 3/SiO 2颜料的呈色性能研究。研究表明,当催化剂(氨水)浓度为0.75 mol/L,反应温度为40 ℃,硅/铁质量比 m(SiO 2)/ m(Fe 2O 3)为0.20,铁/锌摩尔比 n(Fe)/ n(Zn)为4时,制备得到的Zn 2+掺加的包覆型Fe 2O 3/SiO 2颜料的呈色耐热性能获得明显提升,样品在850 ℃煅烧后仍然呈现出明亮的红橙色色调。 相似文献
14.
Mechanochemical synthesis has been applied for many novel material preparations and gained more and more attention due to green and high-efficiency recently. In order to explore the influences of iron precursors on structure and performance of iron molybdate catalyst prepared by mechanochemical route, three typical and cheap iron precursors have been used in preparation of iron molybdate catalyst. Many characterization methods have been employed to obtain the physical and chemical properties of iron molybdate catalyst. Results indicate that iron precursors have the significant impact on the phase composition, crystal morphology and catalytic performance in the conversion of methanol to formaldehyde. It is hard to regulate the phase composition by changing Mo/Fe mole ratios for Fe_2(SO_4)_3 as iron precursor. In addition, as for Fe_2(SO_4)_3, the formaldehyde yield is lower than that from iron molybdate catalyst prepared with Fe(NO_3)_3·9H_2O due to the reduction in Fe_2(MoO_4)_3 phase as active phase. Based on mechanochemical and coprecipitation method, the solvent water could be a key factor for the formation of MoO_3 and Fe_2(MoO_4) for FeCl_3·6H_2O and Fe_2(SO_4)_3 as precursors. Iron molybdate catalyst prepared with Fe(NO_3)_3·9H_2O by mechanochemical route, shows the best methanol conversion and formaldehyde yield in this reaction. 相似文献
15.
The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al 2O 3) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir–Hinshelwood (L–H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al 2O 3 catalysts) on the initial reaction rate. The L–H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al 2O 3 catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al 2O 3 or the presulphided NiMo/Al 2O 3 catalyst. 相似文献
16.
To investigate the correlations between the structural transformations of calcium aluminates and luminescent properties, Eu doped Ca–Al–O system phosphors were synthesized by solid-state reaction process in H 2 atmosphere with CaCO 3, Al 2O 3, Eu 2O 3, and a flux, H 3BO 3 as starting materials. Various phases such as CaAl 2O 4, CaAl 4O 7, Ca 3Al 2O 6, and Ca 12Al 14O 33 were achieved depending on firing temperature, flux amounts, and the mixing ratio of CaO to Al 2O 3. Among various phases, only CaAl 2O 4 contributed to a strong blue emission at 440 nm with an excitation wavelength of 330 nm. 相似文献
17.
Novel Ir-substituted hexaaluminate catalysts were developed for the first time and used for catalytic decomposition of high concentration of N 2O. The catalysts were prepared by one-pot precipitation and characterized by X-ray diffraction (XRD), N 2-adsorption, scanning electronic microscopy (SEM) and temperature-programmed reduction (H 2-TPR). The XRD results showed that only a limited amount of iridium was incorporated into the hexaaluminate lattice by substituting Al 3+ to form BaIr xFe 1−xAl 11O 19 after being calcined at 1200 °C, while the other part of iridium existed as IrO 2 phase. The activity tests for high concentration (30%, v/v) of N 2O decomposition demonstrated that the BaIr xFe 1−xAl 11O 19 hexaaluminates exhibited much higher activities and stabilities than the Ir/Al 2O 3-1200, and the pre-reduction with H 2 was essential for activating the catalysts. By comparing BaIr xFe 1−xAl 11O 19 with BaIr xAl 12−xO 19 ( x = 0–0.8), it was found that iridium was the active component in the N 2O decomposition and the framework iridium was more active than the large IrO 2 particles. On the other hand, Fe facilitated the formation of hexaaluminate as well as the incorporation of iridium into the framework. 相似文献
18.
以对甲基苯硫酚为模型底物,空气为氧化剂,来研究硫醇水相催化氧化偶联制备二硫醚。以活性炭为载体,采用等体积浸渍法制备了一系列负载型氧化物催化剂,并考察了其在对甲基苯硫酚氧化偶联制备对甲苯二硫醚反应中的催化性能。反应结果表明,活性炭负载的铁氧化物具有最佳催化性能。采用N 2物理吸附、X射线衍射、X射线光电子能谱和透射电镜等表征手段对活性炭负载的铁氧化物催化剂进行了表征。表征结果表明,铁氧化物为高度分散在活性炭上的Fe 2O 3物种。以Fe 2O 3/AC为催化剂,当催化剂焙烧温度为400℃,Fe负载量为5%,在50℃下反应30min时,对甲苯二硫醚的收率高达97.4%;该催化剂循环使用5次后活性无明显下降。 相似文献
19.
Moderate additions of Al 2O 3 to strontium ferrite-based mixed conductors, such as SrFe 0.7Al 0.3O 3−δ and La 0.2Sr 0.8Fe 0.8Ga 0.2O 3−δ with the composition close to the solid solution formation limits, make it possible to improve ceramics sinterability, to increase oxygen permeability and to decrease thermal expansion. These effects are associated with the segregation of alumina-rich phases, primarily SrAl 2O 4, and the formation of A-site cation-deficient perovskite. The improved properties of the SrFe 0.7Al 0.3O 3-based material were used to fabricate high-quality tubular membranes for methane conversion reactors. Similar enhancement in sinterability is also observed for another promising parent material of mixed-conducting membranes, La 0.5Sr 0.5FeO 3−δ. However, extensive dissolution of Al 3+ cations in the iron sublattice, creation of A-site vacancies and changing the La:Sr concentration ratio all lead to decreasing ionic transport in La 0.5Sr 0.5FeO 3−δ. As a result, additions of either Al 2O 3 or SrAl 2O 4 have a deteriorating influence on the oxygen permeation fluxes through La 0.5Sr 0.5FeO 3-based ceramics. 相似文献
20.
A novel TiO 2/Al 2O 3/cordierite honeycomb-supported V 2O 5–MoO 3–WO 3 monolithic catalyst was studied for the selective reduction of NO with NH 3. The effects of reaction temperature, space velocity, NH 3/NO ratio and oxygen content on SCR activity were evaluated. Two other V 2O 5–MoO 3–WO 3 monolithic catalysts supported on Al 2O 3/cordierite honeycomb or TiO 2/cordierite honeycomb support, two types of pellet catalysts supported on TiO 2/Al 2O 3 or Al 2O 3, as well as three types of pellet catalysts V 2O 5–MoO 3–WO 3–Al 2O 3 and V 2O 5–MoO 3–WO 3–TiO 2 were tested for comparison. The experiment results show that this catalyst has a higher catalytic activity for SCR with comparison to others. The results of characterization show, the preparation method of this catalyst can give rise to a higher BET surface area and pore volume, which is strongly related with the highly active performance of this catalyst. At the same time, the function of the combined carrier of TiO 2/Al 2O 3 cannot be excluded. 相似文献
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