首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 167 毫秒
1.
以煤气为还原气,以Fe为主活性金属,稀土为助剂催化还原冶炼烟气中SO2制取硫磺,研究了不同稀土、不同稀土含量及不同催化剂制备方式对稀土-过渡金属催化剂催化还原SO2制硫磺活性的影响,并考察了其反应机制.结果表明:不同稀土对Fe/Al2O3催化剂有不同的改性作用,Sm和Dy的加人大大提高了催化剂的活性,在360 ℃时,smFe/Al2O3的硫产率增大到86.62%,比同温度下Fe/Al2O3的提高了40.5%;在400℃时,DyFe/Al2O3的硫产率增大到91.62%.比同温度下Fe/Al2O3的提高了26.4%;REFe/Al2O3催化剂的活性与稀土含量有一定的关系,对SmFe/Al2O3催化剂,稀土Sm的最佳含量为1.0%;不同方式制备的稀土催化剂活性不同,对硫产率来说其大小顺序为:钐铁溶液混浸>先浸钐后浸铁>先浸铁后浸钐;煤气还原SO2的反应机制为中间产物机制.  相似文献   

2.
采用浸渍 -还原法 ,制备了 Al2 O3、 Ti O2 、 Zr O2 担载铁催化剂 ,并在温度 6 2 3K、压力 1.5 MPa、空速80 0~ 10 0 0 h- 1、原料气组成 CO2 /H2 为 1∶ 2等实验条件下 ,考察了不同还原温度的催化剂在 CO2 加氢制低碳(C2 ~ C5 )烃中的反应活性 .结果表明 ,以 CO2 转化率计 ,各催化剂均存在最佳还原温度 (Fe/Al2 O3:873K;Fe/Ti O2 :773K;Fe/Zr O2 :72 3K) .将此温度与催化剂表面 Fe- O键强度相关联 ,发现在相同条件下 ,与载体 M-O键长有关的 Fe- O键越强 ,催化剂越容易被还原 ,最佳还原温度越低 ,反应活性越好 .  相似文献   

3.
采用浸渍法制备了NiO/MgO催化剂,用TPR、XRD、BET、H2(O2)化学吸附等技术对催化剂进行了表征,对催化剂在甲烷空气部分氧化与CO2重整耦合制合成气反应中的催化性能进行了评价。结果表明,在800 ℃焙烧的催化剂中,NiO完全与MgO形成NixMg1-xO固溶体。与低温焙烧的NiO/MgO催化剂相比,虽然NixMg1-xO固溶体催化剂的还原度较低,但可以获得较高的金属分散度和较小的金属粒径,能有效抑制积炭的生成,在反应过程中显示出良好的活性稳定性。对于900 ℃焙烧的催化剂,由于形成了更多难还原的体相固溶体,催化剂的初活性较低。  相似文献   

4.
以MgO,Al2O3,SiO2,TiO2和ZrO2为载体,采用浸渍法制备了负载型Cu-Mn-Ce(CMC)三元复合氧化物催化剂,并用TG,XRD,BET和H2-TPR对催化剂进行了表征,以甲苯和丙酮催化燃烧为模型反应,考察了该催化剂的催化活性。结果表明,纯CMC催化剂的铈基固溶体结构表现出优良的催化活性,当CMC负载在SiO2和Al2O3上后,其大比表面积和表面羟基均不利于CMC活性固溶体结构的形成,另外Mn,Cu等过渡金属与MgO载体发生相互作用而破坏了CMC的活性结构。TiO2和ZrO2则较好地保持了CMC活性固溶体的结构,并显著提高了CMC催化剂的高温热稳定性。  相似文献   

5.
采用过氧化钠和氢氧化钠高温熔融铬矿石样品,以盐酸溶解熔块,合并溶液后用电感耦合等离子体原子发射光谱法测定样品中硅、铝、镁和铁的含量。选择212.412,308.215,285.213,238.204 nm分别作为硅、铝、镁、铁的分析谱线。用铬矿石标准样品配制标准溶液,对标准溶液的贮存方法进行了研究,对影响标准曲线稳定性的因素进行了讨论。SiO2、Fe2O3、Al2O3和MgO的线性范围依次为0.61%~14.64%,13.62%~27.74%,9.29%~15.17%和9.87%~21.49%。采用该法对铬矿石样品进行30d的连续测定,SiO2、Fe2O3、Al2O3和MgO测定值的相对标准偏差分别在0.51%~1.3%,0.45%~2.0%,0.50%~2.5%和1.4%~2.3%之间。  相似文献   

6.
我们以商业预还原的维氏体(Fe1-xO)氨合成催化剂为载体,采用Fe(NO)3 ·9H2O和H2C2O4·2H2O进行原位室温固相反应制备纳米铁或微米铁修饰的铁基氨合成催化剂,并通过XRD、SEM、TG-DTG、H2-TPR等进行了表征.结果表明:Fe(NO)3·9H2O和H2C2O4·2H2O室温固相反应完全生成产物Fe2(C2O4)3·5H2O,且产物分散于载体维氏体催化剂表面.通过纳米铁-微米铁的修饰,催化剂的氨合成活性有很大提高且稳定性好.催化剂活性随着Fe负载量的增加先增加后降低,负载量5%时催化活性最好,反应器出口氨浓由450℃(12.4%)、425℃(11.0%)、400℃(9.4%)分别提升至450℃(15.6%)、425℃(14.8%)、400℃(13%).通过一步简单的修饰,维氏体催化剂的氨合成活性提高约25% ~38%.由于焙烧和还原,生成的Fe1xO或铁粒子与铁催化剂表面发生强相互作用,因此,反应过程中纳米铁或微米铁粒子能稳定存在,催化剂有较高的稳定性.  相似文献   

7.
使用原位穆斯堡尔谱研究了非担载铁氧化物和不同担载量的铁/活性炭催化剂在不同温度下的还原,详细分析了活性炭载体上高分散超顺磁铁物类的穆斯堡尔谱。还原前铁/活性炭催化剂中的铁物类为结构松散的α-Fe_2O_3和没有充分脱水的氧化铁,铁的担载量不很小时可经Fe_3O_4还原到金属态,但活性炭载体可稳定Fe~(3+)使之难以还原,在500℃氢气中大部分铁才还原为金属。铁的担载量很小时,其还原以Fe~(2+)为中间产物,0.2%Fe/AC氢气化剂在500℃氢气还原18小时生成磁分裂金属铁和超顺磁金属铁(δ=0.37mm/s,△=0,H=0),其正的同质异能移表示了铁-活性炭间的电荷转移。  相似文献   

8.
掺杂Fe作为第二种金属组分的V-HMS催化剂的苯羟基化反应   总被引:1,自引:0,他引:1  
冯素姣  岳斌  汪玉叶  林贺  鹤勇 《物理化学学报》2011,27(12):2881-2886
采用浸渍法在V-HMS中引入第二种金属组分(Fe、Al、Cu、Ni、Co、Mo、Cr)以提高催化剂在H2O2为氧化剂的苯羟基化反应中的催化性能.筛选发现,Fe在所研究的金属组分中最为有效.进一步采用共合成法制备了一系列FexVy-HMS催化剂.采用粉末X射线衍射、N2物理吸附、透射电子显微镜、NH3程序升温脱附、H2程序升温还原等手段对催化剂的结构和性质进行表征,结果表明,HMS仍保持介孔结构,Fe的加入在催化剂中产生了新的酸性位和更强的氧化还原性.在苯羟基化反应中,钒物种是反应活性物种,铁物种起助剂作用,其中Fe0.04V0.06-HMS具有最高的催化活性,苯酚收率由不含Fe的Fe0.00V0.06-HMS的13.1%提高到18.1%.提出了Fe、V参与反应过程的可能机理.  相似文献   

9.
使用原位穆斯堡尔谱考察了非担载铁-锰氧化物和铁-锰/活性炭(Fe-Mn/AC)催化剂在不同温度下的还原。还原前Fe-Mn/AC催化剂中存在的为超顺磁α-(Fe_1-_xMn_x)_2O_3和没有充分脱水的铁-锰氧化物。铁的还原同时受铁-锰和铁-活性炭相互作用的影响,载体活性炭使F~(3+)相对稳定而难以还原,锰则促进铁还原到Fe~(2+)并形成相对稳定的FeO-MnO固溶体而难以还原到Fe~0。对4%Mn-8%Fe/AC催化剂,即使在500℃氢气中处理,仍有相当数量的Fe~(3+)和Fe~(2+)不能还原。  相似文献   

10.
以穆斯堡尔谱为主要手段研究了铁/活性炭催化剂的还原特性。发现铁在活性炭上有两种还原方式,相应地生成两种最终还原产物α-Fe和Fe(x)(δ=-0.10mm/s,△=0,H=0)。实验指出,Fe(x)是一种高分散的(d<25A)还原态铁物类,它的生成反映了铁/活性炭间较强的相互作用,这种相互作用的实质是铁与活性炭表面含氧(?)能团间的化学作用。  相似文献   

11.
The large‐scale industrial production of acetic acid (HAc) from carbonylation of methanol has enabled intense research interest from direct hydrogenation of HAc to acetaldehyde (AA). Herein, a series of cerium‐iron oxide solid solution supported metallic cobalt catalysts were prepared by modified sol‐gel method and were applied in gas‐phase hydrogenation of HAc to AA. A synergistic effect between the hydrogenation metal cobalt and Ce‐Fe oxide solid solution is revealed. Specifically, oxygen vacancies provide the active sites for adsorption of HAc, while highly uniformly dispersed metallic Co adsorbs H2 and activates the reduction of HAc into AA. Moreover, the metallic Co can also assist the cyclical conversion between Fe3+/Fe2+ and Ce3+/Ce4+ on the surface of Ce1‐xFexO2‐δ supports. The unique effect substantially enhances the ability of the support material to rapidly capture oxygen atoms from HAc. It is found that the catalyst of 5% Co/Ce0.8Fe0.2O2‐δ with the highest concentration of oxygen vacancy presents the best catalytic performance (i.e. acetaldehyde yield reaches 49.9%) under the optimal reaction conditions (i.e. 623 K and H2 flow rate = 10 mL/min). This work indicates that the Co/Ce‐Fe oxide solid solution catalyst can be potentially used for the selective hydrogenation from HAc to AA. The synergy between the metallic Co and Ce1‐xFexO2‐δ revealed can be extended to the design of other composite catalysts.  相似文献   

12.
The Ga2O3-Al2O3-ZnO (GAZ) multi-component spinel powders with incorporated Cu2+, Co2+, Fe2+, Ni2+, Mn2+ and In2+ metal cations were synthesized by co-precipitation method from a mixed solution of nitrate salts. Spinel crystal structure of each composition was confirmed by XRD measurements. The multi-component oxide powders were tested in the reduction of nitrogen oxide (NO) under lean conditions. Among the catalysts tested, In2O3-containing GAZ with a pure spinel phase structure showed promising catalytic activity in the NO reduction in the presence of 10% H2O vapor. In addition, the effect of H2O vapor and SO2 on the selective reduction of NO over In2O3-GAZ/cordierite and In2O3-GAZ/metal honeycombs catalysts has been investigated.  相似文献   

13.
A method was developed for introducing gallium into Mg-Al hydrotalcites—precursors of oxide catalysts for oxidative dehydrogenation of alkanes. Samples of oxide catalysts were synthesized that contained gallium oxide and also oxides of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. The catalytic properties of the produced catalysts were studied in the oxidative dehydrogenation of ethane, propane, isobutane, and hexane. It was established that the addition of gallium to catalysts increases the ethylene and propylene yields in the oxidative dehydrogenation of ethane and propane. New hydroxo salts with a layered structure of the hydrotalcite type were synthesized: ternary magnesium gallium aluminum hydroxonitrate of variable composition [Al1 ? n Ga n Mg m (OH)3 + 2m ? 1][NO3 · nH2O] and quaternary magnesium gallium chromium aluminum hydroxonitrate of the composition [AlGaCrMg1.8(OH)11.6][NO3 · nH2O]; these salts were found to be isostructural.  相似文献   

14.
磁性纳米固体酸催化剂Zr(SO4)2/Fe3O4的制备及催化性能研究   总被引:12,自引:0,他引:12  
本文提出将磁性和固体酸进行组装从而合成磁性纳米固体酸催化剂的思路,首先制备了纳米级磁性前体-磁基体(Fe3O4);然后筛选出超声波法制备了不同配比的磁性纳米固体酸催化剂Zr(SO4)2/Fe3O4,对其进行了初步表征。并将其作为乙酸丁酯合成反应的催化剂,酯化转化率最高达到84%,利用其磁性即可将催化剂进行分离。  相似文献   

15.
The trivalent metal cations Al3+, Cr3+, and Fe3+ were each introduced, together with Sc3+, into MIL‐100(Sc,M) solid solutions (M=Al, Cr, Fe) by direct synthesis. The substitution has been confirmed by powder X‐ray diffraction (PXRD) and solid‐state NMR, UV/Vis, and X‐ray absorption (XAS) spectroscopy. Mixed Sc/Fe MIL‐100 samples were prepared in which part of the Fe is present as α‐Fe2O3 nanoparticles within the mesoporous cages of the MOF, as shown by XAS, TGA, and PXRD. The catalytic activity of the mixed‐metal catalysts in Lewis acid catalysed Friedel–Crafts additions increases with the amount of Sc present, with the attenuating effect of the second metal decreasing in the order Al>Fe>Cr. Mixed‐metal Sc,Fe materials give acceptable activity: 40 % Fe incorporation only results in a 20 % decrease in activity over the same reaction time and pure product can still be obtained and filtered off after extended reaction times. Supported α‐Fe2O3 nanoparticles were also active Lewis acid species, although less active than Sc3+ in trimer sites. The incorporation of Fe3+ into MIL‐100(Sc) imparts activity for oxidation catalysis and tandem catalytic processes (Lewis acid+oxidation) that make use of both catalytically active framework Sc3+ and Fe3+. A procedure for using these mixed‐metal heterogeneous catalysts has been developed for making ketones from (hetero)aromatics and a hemiacetal.  相似文献   

16.
 采用不同浸渍顺序制备了三种 Ir-Fe 催化剂, 其 CO 选择氧化 (PROX) 反应活性差别很大, 其中共浸渍的 Ir-Fe 催化剂活性最高. 吸附量热研究表明, 三种催化剂的 H2 和 CO 吸附存在差别. 通过对三种催化剂还原后、再氧化和反应后准原位 57Fe 穆斯堡尔谱的研究, 得到各种 Fe 物种信息. 结果表明, 三种制备方法影响催化剂中 Ir-Fe 相互作用强度, 导致催化剂中 Fe 物种的氧化还原性能不同. 催化剂中 Fe2+(a) 的含量与 CO 转化率呈正比关系, Fe2+(a) 是 PROX 反应过程中活化氧的活性中心. 浸渍顺序改变了 Ir-Fe 间相互作用强度, 从而改变 Fe2+(a) 物种含量, 影响 PROX 反应活性. Ir-Fe 间的相互作用可以稳定活化氧的 Fe2+(a) 物种, 为今后研究金属-金属间的相互作用提供借鉴.  相似文献   

17.
Studies of reactions between oxide and Fe2+ ions in molten LiCl+KCl eutectic have shown that ferrous oxide is stabilizedin the form of a solid solution FeOLiFeO2. Potentiometric titrations with an yttria-stabilized zirconia electrode(indicator of pO2?) and an iron electrode have first given for y, corresponding to the solid solution composition Fe1-yLiyO, a value between 0 and 0.1, and secondly shown the formation of non-stoichiometric ferrous oxide. We have alsosuggested a mechanism for the formation of the solid solution Fe1-yLiyO.  相似文献   

18.
For the first time, a method was developed for introducing indium into Mg-Al hydrotalcites—precursors of oxide catalysts for oxidative dehydrogenation of alkanes. Samples of oxide catalysts were synthesized that contained indium oxide and also oxides of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. The catalytic properties of the produced catalysts were studied in the oxidative dehydrogenation of ethane, propane, and isobutane. It was established that the introduction of indium into catalysts increases the selectivity and the yields of desired products. New hydroxo salts with a layered structure of the hydrotalcite type were synthesized: [Al1 ? n In n Mg m (OH)3 + 2m ? 1][(NO3) · nH2O] and quaternary magnesium indium chromium aluminum hydroxonitrate of the composition [Al0.5In0.5Cr0.5Mg2.5(OH)8.5][(NO3) · nH2O]; these salts were found to be isostructural. The obtained compounds were studied as catalyst precursors.  相似文献   

19.
Systematic access to metal‐functionalized polyoxometalates has thus far been limited to lacunary tungsten oxide and molybdenum oxide clusters. The first controlled, stepwise bottom‐up assembly route to metal‐functionalized molecular vanadium oxides is now presented. A di‐vacant vanadate cluster with two metal binding sites, (DMA)2[V12O32Cl]3? (DMA=dimethylammonium) is formed spontaneously in solution and characterized by single‐crystal X‐ray diffraction, ESI mass spectrometry, 51V NMR spectroscopy, and elemental analyses. In the cluster, the metal binding sites are selectively blocked by hydrogen‐bonded DMA placeholder cations. Reaction of the cluster with transition metals TM (Fe3+, Co2+, Cu2+, Zn2+) gives access to mono‐functionalized vanadate clusters (DMA)[{TM(L)}V12O32Cl]n? (L=ligand). Metal binding is accomplished by significant distortions of the vanadium oxide framework reminiscent of a pincer movement. Cluster stability under technologically relevant conditions in the solid‐state and solution is demonstrated.  相似文献   

20.
The influence of synthesis conditions on the phase composition and texture of porous nickel supports as plates with a magnesium oxide underlayer were investigated by X-ray diffraction, low-temperature nitrogen absorption, and electron microscopy combined with X-ray microanalysis. Nickel catalysts supported on these plates were studied. Thermal treatment of Mg(NO3)2 in nitrogen yields a magnesium oxide underlayer with a small specific surface area (support I). The replacement of nitrogen with hydrogen leads to a larger surface area (support II). The formation of MgO is accompanied by the incorporation of Ni2+ cations from the oxide film into the underlayer. Upon subsequent reduction with hydrogen or under the action of the reaction medium, these cations form fine crystallites of nickel. The supports having an oxide underlayer show a higher activity in methane steam reforming than the initial metallic nickel. Nickel catalysts on supports I and II show similar activities. The activity of the catalysts was stable throughout 50-h-long tests; no carbon deposits were detected by TEM.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号