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1.
采用浸渍法制备了系列H-β分子筛修饰的Pd/Al_2O_3催化剂,通过XRD、低温N2吸附、NH_3-TPD等分析表征技术和以油酸甲酯为模型化合物的加氢反应体系,探索了H-β分子筛的加入方式和含量对催化剂催化性能的影响。结果表明,由于加入方式不同,Pd-Al_2O_3-BEA催化剂组成要素之间的相互作用呈现较大差异,从而使其催化性能呈现较大不同。在Pd/(BEA-Al_2O_3)中,随着H-β分子筛加入量的增加,催化剂的比表面积、孔容、强酸酸量呈增大趋势,弱酸酸量呈先增大后减小趋势,平均孔径呈减小趋势。由于Pd/(45%BEA-Al_2O_3)催化剂具有合适的微孔孔分布、适中的强酸酸量、最大的弱酸酸量,使其呈现出最大的航空燃油烃类选择性,异构烷烃选择性和一定比例的环烷烃和芳香烃产物。  相似文献   

2.
在CeO2-ZrO2中加入La2O3对改善单Pd三效催化剂性能的作用   总被引:5,自引:0,他引:5  
浸渍法制备了CeO2-ZrO2-La2O3复合氧化物,用XRD、热分析(TG-DTA,DSC)、BET表面积、H2-TPR等对合成样品进行表征,研究了La2O3的加入对CeO2-ZrO2和单钯Pd/CeO2-ZrO2/γ-Al2O3/蜂窝陶瓷催化剂性能和热稳定性的影响。结果表明,在CeO2-ZrO2-La2O3中,La的存在能促进CeO2-ZrO2固溶体的还原,提高贮氧能力;在Pd/CeO2-ZrO2/γ-Al2O3中加入La有利于提高催化剂的耐热稳定性,阻止γ-Al2O3在高温下的晶相转变,进一步稳定Al2O3的结构,保持其高的表面积。在贵金属Pd的负载量为1 g·L-1的条件下,测定了Pd/CeO2-ZrO2-La2O3/γ-Al2O3/蜂窝陶瓷催化剂对CO、C3H8和NOx的三效催化净化活性。结果表明,在Pd/CeO2-ZrO2/Al2O3/蜂窝陶瓷催化剂中加入La2O3后,能明显地改善催化剂的低温活性和三效催化性能,经1 000 ℃老化10 h后,CO、C3H8和NOx净化的起燃温度(T50)分别为330 ℃、350 ℃和380 ℃。  相似文献   

3.
通过使用聚乙烯吡咯烷酮作为稳定剂,合成了磁性Pd/Fe3O4纳米颗粒催化剂。对该催化剂进行粉末X射线衍射、透射电子显微镜、感应耦合等离子体和磁性表征。将Pd/Fe3O4催化剂用于Heck反应,检测其催化性能。测试结果表明Pd纳米颗粒负载在Fe3O4纳米颗粒上,而且催化剂的尺寸<20 nm,并在Heck反应中表现了极好的催化性能。此外,催化剂可以通过磁场回收利用, 且催化活性没有显著的降低。  相似文献   

4.
H2SO4处理的Nb2O5/γ -Al2O3催化剂表面酸性与催化性能研究   总被引:3,自引:0,他引:3  
用Hammett指示剂法、红外光谱(IR)、示差扫描量热-热重法(DSC-TG)和微型催化反应装置等研究了H2SO4处理的负载型Nb2O5/γ-Al2O3催化剂表面酸性和催化异丁烯(IB)与异丁醛(IBA)反应生成2,5-二甲基-2,4-己二烯(DMHD)的催化性能。结果表明随所用H2SO4浓度增加,Nb2O5/γ-Al2O3催化剂表面酸性增强,B酸量增加,L酸量先增加后下降。经H2SO4处理的Nb2O5/γ-Al2O3催化剂的催化活性明显增加,但当H2SO4浓度超过0.05 mol·L-1时催化活性又急剧下降,这可能是因为在H2SO4处理的催化剂表面形成的强酸中心上,产物分子进一步转化为积炭且封闭催化剂活性表面,导致催化活性下降。  相似文献   

5.
以九水合硝酸铝(Al(NO33·9H2O)与正硅酸乙酯(TEOS)为前驱盐,采用溶胶-凝胶法制备一系列不同Al2O3含量的SiO2-Al2O3复合氧化物,并通过浸渍硝酸氧锆引入ZrO2,制备ZrO2/SiO2-Al2O3复合氧化物催化剂,考察催化剂在肉桂醛(CAL)MPV转移加氢中的催化性能,并结合N2物理吸附、X射线粉末衍射(XRD)、傅里叶变换红外光谱(FTIR)、NH3-程度升温脱附(NH3-TPD)、Py-原位红外(Py-IR)等技术,研究催化剂结构、织构以及表面性质与其催化性能间的构效关系.研究表明,所制备的催化剂均以L酸为主,并含有少量B酸中心,这使得加氢产物以肉桂醇(COL)为主,并含有少量1-苯丙烯-2-丙基醚(CPE).Al2O3含量不仅影响催化剂表面的酸中心数量,而且对催化剂的织构参数有较大影响.随Al2O3含量的增加,催化剂表面L酸与B酸中心均有所增加,而孔径则持续变小,这使得催化反应呈现CAL转化率先增加后减少、目标产物COL选择性先稍有减小后有所增加的趋势.在Si/Al比为2时,催化剂具有最优的催化性能,优化反应条件下,CAL转化率达96%,目标产物COL选择性达90%.  相似文献   

6.
以Al2O3为基质,添加ZrO2和La2O3,制成La2O3-ZrO2-Al2O3复合载体,然后采用SO42-进行改性,再负载上Cu2+,制备了铜基SO42-改性的复合载体催化剂(Cu/SO42-/La2O3-ZrO2-Al2O3)。考察了它在富氧条件下对丙烯选择还原NO的催化性能,并借助XRD、SEM、TG、Py-IR、NH3-TPD、FTIR和TPR等方法研究了Cu/SO42-/La2O3-ZrO2-Al2O3的结构和性能的关系。结果表明,ZrO2的加入主要有利于提高催化剂的低温活性;La2O3的加入则主要有利于提高催化剂的热稳定性和还原性能;SO42-能够与Zr形成螯合双配位结构,大幅度促使催化剂表面酸量增加并且酸性增强;因此,有效地提高了Cu/SO42-/La2O3-ZrO2-Al2O3在富氧条件下对丙烯选择还原NO的催化活性和水热稳定性。在无水条件下,Cu/SO42-/La2O3-ZrO2-Al2O3能使NO的最大转化率高达84.3%,即使在275 ℃ 10%水蒸气存在的情况下,仍能使NO的转化率高达81.2%。  相似文献   

7.
以γ-Al2O3为载体,采用等体积浸渍法,制备了不同K2CO3含量的Ni-Cu-Mn-K/Al2O3水煤气变换催化剂,采用低温N2吸附、XRD、TPD和TPR,考察了K2CO3含量对催化剂结构和性能的影响。结果表明:K2CO3的加入使催化剂的还原温度有所提高,适量的K2CO3能增加活性组分的电子密度,从而增强其给电子活化CO的能力,提高催化剂的活性。但过量的K2CO3使得催化剂比表面积和孔容降低,且导致催化剂对CO吸附过强,催化活性降低。当Ni-Cu-Mn-K/γ-Al2O3催化剂中K2CO3的添加量为7.5%时,且催化剂经530 ℃耐热15 h后,在350 ℃时水煤气变换反应中CO转化率达62.29%。  相似文献   

8.
为了提高苯乙炔加氢反应中的苯乙烯选择性, 本文采用“胶体-等体积浸渍”两步法制备了Pd-Cu/γ-Al2O3双金属催化剂. 利用高分辨率透射电镜(HRTEM)、X射线光电子能谱(XPS)、CO脉冲化学吸附、N2物理吸附、电感耦合等离子体原子发射光谱(ICP-AES)等技术表征了Pd-Cu/γ-Al2O3的结构性质, 考察了Cu/Pd 摩尔比、Pd负载量以及金属引入顺序对Pd-Cu/γ-Al2O3催化苯乙炔选择性加氢性能的影响. 结果表明, 与Pd/γ-Al2O3单金属催化剂相比, Pd-Cu/γ-Al2O3的苯乙烯选择性大幅度提高, 尤其是当Pd负载量为0.3%(w), 且Cu/Pd摩尔比为0.6时, Pd-Cu/γ-Al2O3表现出优异的加氢选择性; 在0.1 MPa和40 ℃下, 当苯乙炔转化率为90%时, 双金属催化剂的苯乙烯选择性可达95%; 当转化率达到99%以上时, 苯乙烯选择性仍保持在82%左右. 分析表明, Pd-Cu/γ-Al2O3中形成了Pd-Cu合金, 但是两种金属间不存在电子转移, Cu对Pd的几何效应才是导致Pd-Cu/γ-Al2O3苯乙烯选择性增加的主要原因.  相似文献   

9.
刘利  崔文权  邱发礼 《化学学报》2010,68(3):211-216
采用高温固相法合成了铈掺杂的K2La2Ti3O10催化剂, 利用X射线衍射(XRD)、紫外-可见漫反射(UV-vis DRS)、透射电镜(TEM)和X射线光电子能谱(XPS)对催化剂进行了表征. 考察了催化剂的可见光催化分解甲醇水溶液制氢的活性, 并对可见光催化机理进行了分析. 研究表明, 铈的掺杂没有改变K2La2Ti3O10的微晶结构, 并使催化剂粒径有所减小. 紫外可见漫反射分析表明禁带宽度为2.3 eV左右, 对可见光具有较高吸收. XPS表明La和Ti为+3和+4价, 而Ce则是+3和+4的混合价态. 担载2 wt% Pt后, 在可见光下光催化活性大大提高, 当铈的掺杂量为0.5 mol%(即Ce取代La的摩尔百分量)时, 光催化活性达到最大, 产氢速率为0.05 mmol/h; 光照5 h后产氢量为0.22 mmol, 而纯K2La2Ti3O10的产氢量只有0.037 mmol.  相似文献   

10.
在磁性SiO2@Fe3O4纳米微球表面原位合成包覆不同含量的Y-MOF,从而制备出新型磁性Y-MOF@SiO2@Fe3O4催化剂。采用XRD、TEM、FT-IR、VSM和N2吸附-脱附测试等手段对催化剂的结构进行表征,并且评价了催化剂对苯胺和丙烯酸甲酯的Aza-Micheal加成反应性能。结果表明Y-MOF能均匀包覆在磁性SiO2@Fe3O4纳米微球表面,形成具有核壳结构的磁性Y-MOF@SiO2@Fe3O4催化剂,催化剂具有良好的超顺磁性。Y-MOF含量为43.3%(w/w)的Y-MOF@SiO2@Fe3O4催化剂,在苯胺和丙烯酸甲酯的Aza-Micheal加成反应表现出最好的催化性能,丙烯酸甲酯的转化率为88.3%时,N-(β-甲氧碳酰乙基)苯胺的选择性可达99.8%。反应后的催化剂可以通过外磁场容易回收,并且重复使用5次其转化率和选择性没有明显下降。  相似文献   

11.
phase diagrams of KCl-KBO2-K2CO3, K2MoO4-KBO2-K2CO3, and K2WO4-KBO2-K2CO3 ternary systems were studied by a calculation-experimental method and differential thermal analysis (DTA). The coordinates of ternary eutectics were determined to be E 1: 622°C, 8.5 mol % KBO2, 56.5 mol % KCl, and 35 mol % K2CO3; E 2: 710°C, 23 mol % KBO2, 43 mol % K2CO3, and 34 mol % K2MoO4; E 3: 710°C, 23 mol % KBO2, 43 mol % K2CO3, and 34 mol % K2WO4. The specific heats of melting of the eutectics were determined.  相似文献   

12.
The phase relations in the cross-section of the K2W2O7-K2WO4-KPO3 containing 15 mol% Bi2O3 were undertaken using flux method. Crystallization fields of K6.5Bi2.5W4P6O34, K2Bi(PO4)(WO4), Bi2WO6, KBi(WO4)2 and their cocrystallization areas were identified. Novel phase K6.5Bi2.5W4P6O34 was characterized by single-crystal X-ray diffraction: sp. gr. P−1, a=9.4170(5), b=9.7166(4), c=17.6050(7) Å, α=90.052(5)°, β=103.880(5)° and γ=90.125(5)°. It has a layered structure, which contains {K7Bi5W8P12O68} layers stacked parallel to ab plane and sheets composed by potassium atoms separating these layers. Sandwich-like {K7Bi5W8P12O68} layers are assembled from [W2P2O13] and [BiPO4] building units, and are penetrated by tunnels with K/Bi atoms inside. FTIR-spectra of K2Bi(PO4)(WO4) and K6.5Bi2.5W4P6O34 were discussed on the basis of factor group theory.  相似文献   

13.
K3InF6 is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K3InF6 by decomposition at high temperature. The crystal structure of K3InC12O14H4F18 is characterized by complex anions [In(CF3COO)4(OHx)2](5−2x)− and isolated [CF3COOH2−x](x−1)− molecules with x=2 or 1, surrounded by K+ cations. The crystal structure of K3InC12O12F18 is only constituted by complex anions [In(CF3COO)6]3− and K+ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K2InC10O10H6F9 and K3InC12O12F18 were also performed at room temperature on pulverized crystals.  相似文献   

14.
Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.  相似文献   

15.
The phase diagrams of the NaBO2-NaCl-Na2CO3, NaBO2-Na2CO3-Na2MoO4, NaBO2- Na2CO3-Na2WO4, and NaBO2-NaCl-Na2WO4 ternary systems were studied by a calculation-experimental method and differential thermal analysis. The coordinates of ternary eutectics were determined: E 1: 612°C, 16 mol % NaBO2, 42 mol % NaCl, and 42 mol % Na2CO3; E 2: 568°C, 12 mol % NaBO2, 28 mol % Na2CO3, and 60 mol % Na2MoO4; E 3: 575°C, 12 mol % NaBO2, 32 mol % Na2CO3, and 56 mol % Na2WO4; E 4: 628°C, 8 mol % NaBO2, 20 mol % NaCl, and 72 mol % Na2WO4; and E 5: 655°C, 9 mol % NaBO2, 53 mol % NaCl, and 38 mol % Na2WO4.  相似文献   

16.
马修臻  胡斌 《化学通报》2018,81(10):939-943,938
本文用高精度数字式振荡管密度计测定了288K至318K温度范围内Li2SO4 + Na2SO4 + H2O和 Li2SO4 + K2SO4 + H2O三元体系的密度。混合溶液的离子强度范围从0.1到4.5 mol.kg–1,混合溶液中Na2SO4和K2SO4的离子强度分数为0.2,0.4,0.6和0.8。用密度实验值拟合得到了不同温度下Pitzer离子相互作用模型混合参数θV和 ψV,模型的计算值与实验值的偏差在±0.002 g.cm3以内。用Pitzer模型计算了不同离子强度下三元体系的混合体积。  相似文献   

17.
Two compounds of formula La7A3W4O30 (with A=Nb and Ta) were prepared by solid-state reaction at 1450 and 1490 °C. They crystallize in the rhombohedric space group R-3 (No. 148), with the hexagonal parameters: , and , . The structure of the materials was analyzed from X-ray, neutron and electronic diffraction. These oxides are isostructural of the reduced molybdenum compound La7Mo7O30, which are formed of perovskite rod along [111]. An order between (Nb, Ta) and W is observed.  相似文献   

18.
The structural, electronic, and vibrational characteristics and energies of the isolated polyoxide clusters B20O30, Al20O30, V20O50, Si20O30H20, and Si20O30F20 and their complexes with the H ion and ammonia complexes Al20O30 · nNH3 have been calculated by the density functional theory B3LYP method with different basis sets. The computation results show that the symmetric closo structure I h with oxygen bridges located above the centers of the faces of an empty [M20] dodecahedron is more favorable for V20O50, Si20O30H20, and Si20O30F20. For B20O30, the cage closo isomer is also more favorable than the other isomers, but its structure is severely distorted as compared to a dodecahedron and has a symmetry close to C 3 . For Al20O30, the I h structure corresponds to a high-lying local minimum of the potential energy surface. For Al20O30, a set of unusual puckshaped isomers of symmetry C i , with different numbers of four-coordinate atoms IVAl and three-coordinate atoms IIIO, was localized; these structures are more than 90 kcal/mol more favorable than the dodecahedron I h . The most favorable isomer of Al20O30 contains twelve four-coordinate atoms IVAl and four five-coordinate atoms VAl. The energies of dissociation of the most favorable M20O30 clusters into the M2O3 (C 2v ) and M4O6 (T d ) fragments and, in the case of Al20O30, also into the Al8O12 (O h ) and Al12O18 (D 3d ) fragments, have been estimated. The conclusion has been drawn that these clusters can, in principle, exist and can be experimentally detected in the isolated state. Analogous calculations have been performed for ammonia complexes Al20O30 · nNH3 with n varying from 1 to 20. The effect of solvation on the relative stability of the dodecahedral and puckshaped isomers of the Al20O30 cluster is observed. The isomers with ammonia molecules in their first coordination sphere become much closer to one another on the energy scale; however, the dodecahedron remains a considerably less favorable intermediate. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 624–635.  相似文献   

19.
SnSbBiS4-SnS and SnSbBiS4-Sn2Sb6S11 sections were studied by physicochemical methods (DTA, X-ray powder diffraction, microstructure observation, and microhardness measurements). These sections were found to be eutectic quasi-binary sections of the SnS-Sb2S3-Bi2S3 ternary system. Solid solution regions based on the initial components were found on either side of the sections. Alloys in the solid solution region are p-type semiconductors.  相似文献   

20.
We have studied the preparation and crystallographic structure of three perovskite-type compounds: Sr3Cr2WO9, cubic, the lattice parameter of which is a = 7.812Å; Ca3Cr2WO9, tetragonal, the lattice parameters of which are a = 5.408 Å and c = 7.635Å; and Ba3Cr2WO9, hexagonal, the lattice parameters of which are a = 5.691 Å and c = 13.957Å. We have compared these three structures and shown the relationship between the dimensions of the alkaline-earth metal and the existence of the different structures.  相似文献   

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