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1.
采用超临界干燥法制备ZrO2超细催化剂,用于一氧化碳加氢合成甲醇、异丁醇。考察了催化剂的焙烧温度、焙烧时间以及碱金属助剂对合成醇性能的影响,并结合N2吸附、TEM、XRD表征,研究催化剂的织构、体相结构与催化活性的关系。发现随着催化剂焙烧温度升高、焙烧时间的延长,ZrO2由四方晶型(tZrO2)向单斜晶型(mZrO2)转变;浸渍K2CO3在焙烧过程中能够稳定tZrO2,浸渍Na2CO3则促进四方晶型向单斜晶型的转变。微细颗粒四方晶型的ZrO2有利于异丁醇的生成。  相似文献   

2.
以合成为目的,研究了Mo_3S_4(dtp)_4(H_2O)(Ⅰ)、Mo_3OS_3(dtp)_4(H_2O)(Ⅱ)、W_2S_4(dtp)_2(Ⅲ)等为主的簇合物的反应及其产物。包括配基置换反应,加硫和脱硫反应,簇合反应,簇解和局部氧化反应。讨论了反应物的结构和试剂两个方面对反应的影响,由此总结了若干反应规律。本文还以Mo_4S_4(OAc)_2(dtp)_4和Mo_3XS_6(dtp)_3Y(X=S,O;Y=I,Cl)为例,阐述了设计合成的基本思路。  相似文献   

3.
采用超临界干燥法制备ZrO2超细催化剂,用于一氧化碳加氢合成甲醇,异丁醇。考察了催化剂的焙烧温度,焙烧时间以及碱金属助剂对合成醇性能的影响,并结合N2吸附,TEM,XRD表征,研究催化剂的织构,体相结构与催化活性的关系。发现随着催化剂焙烧温度升高,焙烧时间的延长,ZrO2由四方晶型向单斜晶型转变;浸渍K2CO3在焙烧过程中能够稳定t-ZrO2,浸渍Na2CO3则促进四方晶型向单斜晶型的转变。  相似文献   

4.
采用NMR方法考察了室温和低温(-78~-60℃)下Pd2X2(dpm)2(X=NCO-,CH3CO,SCN-和NO,dpm=Ph2PCH2PPh2)与H2S在CD2Cl2或CDCl3中的反应。结果表明,在X=NCO-和CH3CO的情况下,H2S优先与这些Pd配合物的阴离子作用生成相应的共轭酸HX和Pd2(SH)2(dpm)2,后者在H2S存在下又进一步转化为Pd2(SH)2(dpm)2(μ-S);当X=SCN-和NO时,反应则生成结构可能为[Pd2(H)(SH)(μ-SH)(dpm)2]+的双核Pd配合物。  相似文献   

5.
采用NMR方法考察了室温和低温(-78~-60℃)下Pd2X2(dpm)2(X=NCO^-,CH3CO^-2,SCN^-和NO^-3,dpm=Ph2PCH2PPh2)与H2S在CD2Cl2或CDCl3中的反应。结果表明,在X=NCO^-和CH3CO^-2的情况下,H2S优先与这些Pd配合物的阴离子作用生成相应的共轭酸HX和Pd2(SH)2(dpm)2,后者在H2S存在下又进一步转化为Pd2(SH)  相似文献   

6.
邹旭华  段雪 《分子催化》2000,14(3):171-174
采用有机金属配合物固载法,将金的有机配合物Au(PPh3)(NO3)沉积于刚制备出的Ni(OH)2沉淀上,与其表面的-OH基反应,再于注动空气中程序升温焙烧,制和轩出了颗粒度小,分散度高的金催化剂,改变制备条件,研究其对催化剂活性的影响。结果表明,以K2CO3作为制备Ni(OH)2的沉淀剂,金担载量为3%(质量分数),在焙烧温度为300℃的条件下,制备出的负载型金催化剂Au/NiO对CO的低温氧化  相似文献   

7.
用于燃料电池的Bi2O3基稀土固体电解质的研制   总被引:2,自引:0,他引:2  
合成了(Bi2O3)0.75(Y2O3)0.25和(Bi2O3)0.65(Gd2O3)0.35固体电解质陶瓷材料;测试了其晶体结构,XPS谱及在500 ̄800℃的离子电导率随温度的变化;组装了镀有ZrO2-Y2O3保护膜的Bi2O3基稀土固体电解质燃料电池。  相似文献   

8.
在无水乙醇介质中合成了2,6-二甲酸吡啶氮氧化物(H2PdCO)和稀土硝酸盐形成的配合物[RE(PdCO)·NO3·2H2O](RE=La-Na,Sm,Eu,Tb,Ho,Er,Y)。通过元素分析,摩尔电导,红外光谱,紫外光谱,1H核磁共振谱及热重-差热分析等对该系列配合物进行了表征,并研究了Eu(Ⅲ),Tb(Ⅲ)配合物荧光性质。  相似文献   

9.
分别用X-光电子能谱,X-射线衍射,氢氧滴定及红外光谱对催化剂Pd/α,δ-Al2O3进行了表征。结果表明:催化剂的活性组份Pd是以氧化钯PdO和氯氧化钯Cl-Pd-O-Al两种形式存在,当催化剂经800℃高温焙烧后,绝大部分Cl-Pd-O-Al转化为PdO高温促进PdO烧结,活性中心减少,从而解释了催化剂Pd/α,δ-Al2O3经高温焙烧后活性降低的原因。  相似文献   

10.
SO4^2—TiO2—Hβ—Al2O3催化剂的制备及催化性能研究   总被引:1,自引:0,他引:1  
以Hβ沸石为,通过TiO2改性及硫酸铵处理制备了SO4^2--TiO2-Hβ-Al2O3催化剂,并由XRD、XPS、NH3-TPD、FTIR及化学吸附等手段考察了不同焙烧温度对该催化剂表面性质、酸性及催化性能的影响。结果表明;适宜的焙烧温度使SO4^2--TiO2-Hβ-Al2O3的酸量大幅度增加,强酸比例增大,并产生部分增强酸中心,高强度的酸性中心中,以L酸中心为主;550℃焙烧的样品能使沸石表  相似文献   

11.
嵌入Y型分子筛中钯簇合成与结构的研究   总被引:2,自引:0,他引:2  
Pd clusters encaged in Y-zeolite (Pd0Y) have been prepared by means of exchanging zeolite HY with [Pd(NH3)4]2+ under microwave radiation. The product formed was deaminized by heating, washed sufficiently with de-ionized water and reduced with hydrogen. The crystal phase diffraction of Pd was not found in the XRD spectrogram of Pd0y. According to polycrystal X-ray diffraction data. Radial Electron Distribution Function (REDF) of Pd0Y was calculated to elucidate the structure of Pd cluster. The results show that the Pd clusters are of the Al type closely packed arrangement. The dimension of them is about 12 Å. They are encaged in the supercage of zeolite Y. Their occupancy on the supercage is as small as 0.06 so that the framework structure of zeolite Y is unchanged. Therefore, the high dispersing Pd cluster aggregating in supercage exhibit strong catalytic effect. The CO-conversion of Pd0Y with Pd 0.72% and 6.13% (in mass fraction) is 67 % and 100 % (in volume fraction) respectively. Evaluation conditions:
mixed gas containing 0.02% CO and air,
space velocity 3000 h-1,
reaction temperature 0 ℃.  相似文献   

12.
Design and preparation of highly active hydrodesulfurization (HDS) catalysts is very important for the removal of air pollution. Herein, we report an extraordinarily active HDS catalyst, which is synthesized by loading of Pd on mesoporous zeolite Y (Pd/HY-M). The mesoporous zeolite Y is successfully synthesized using a water glass containing N,N-dimethyl-N-octadecyl-N-(3-triethoxysilylpropyl) ammonium [(C(2)H(5)O)(3)SiC(3)H(6)N(CH(3))(2)C(18)H(37)](+) cation as a mesoscale template. Compared with mesoporous Beta and ZSM-5 supported Pd catalysts (80.0% and 73.4% for Pd/HBeta-M and Pd/HZSM-5-M, respectively) as well as commercial catalyst of γ-Al(2)O(3) supported Pd catalyst (31.4%), Pd/HY-M catalyst exhibited very high activity in HDS of 4,6-dimethyldibenzothiophene (4,6-DM-DBT, 97.3%). The higher activity of Pd/HY-M than that of Pd/HBeta-M and Pd/HZSM-5-M is assigned to the larger micropore size of zeolite Y compared to that of Beta and ZSM-5. Theoretical simulation and adsorption experimental data show that 4,6-DM-DBT has difficulty entering the micropores of ZSM-5 and Beta zeolites, but the micropores of Y zeolite are accessible.  相似文献   

13.
Palladium catalysts based on A, X, Y, chabazite, erionite, mordenite, TsVM, and TsVK zeolites are studied by the methods of temperature-programmed reduction and hydrogen desorption. Palladium is shown to be located in zeolite pores in all catalysts except Pd/mordenite for which 24 % of the palladium is located on the external surface of the zeolite. The dispersity of the palladium on the zeolites is determined by the amount of H2 evolved in the decomposition of the -phase of PdH and by the value of the O/Pd ratio obtained by palladium oxidation in the 100 to 500 °C temperature range. According to the O/Pd ratio, the catalysts are divided into two groups: samples based on X, Y, chabazite, erionite, and mordenite (O/Pd=0.4 to 0.7), and catalysts containing A, TsVM, and TsVK zeolites (O/Pd=0.2 to 0.3). The catalysts of the first group are weakly active in the oxidative acetoxylation of propylene, while all of the catalysts of the second group except Pd/NaA are very active. The conclusion is drawn that the oxidation of palladium is not the limiting stage in the oxidative acetoxylation of propylene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 642–648, April, 1995.  相似文献   

14.
Pd/NaZSM-5负载型催化剂上CO完全氧化研究   总被引:7,自引:2,他引:5  
毕玉水  刘建福  吕功煊 《化学学报》2002,60(9):1624-1629
采用浸渍法制备了一系列Pd/NaZSM-5负载型催化剂。考察了焙烧温度、反应温 度、Pd含量及预还原等对CO氧化性能的影响。结果表明:制备条件和反应条件对催 化活性均有较大影响,催化剂的活性随着焙烧温度的增加而降低,随反应温度及 Pd含量的增加而增加。XRD,TEM结果表明催化剂中Pd组分处于高分散状状;表面 XPS分析证实催化剂表面Pd物种PdO_2和PdO在反应过程中发生明显的表面化学变化 ,高价Pd物种随反应的进行逐步被CO还原为低价Pd物种,催化剂活性下降与Pd物种 被还原有关。H_2预还原作用也导致催化剂活性有所下降。  相似文献   

15.
1前言早在70年代末80年代初,就有文献报道在载体上的金属Pd的某些性能,并注意到将其作为催化剂在甲醇合成上有很高的活性和选择性[1~3],然而并没有继续进行系统研究.80年代末,Sachtler等人开始在这一领域进行更广泛、更细致、更深入的研究[4~8].他们不仅研究了载在分子筛上的Pd,也研究了Pd与其他过渡金属所形成的合金的性能.它们的催化性质研究包括对CO加氢、新戊烷和氢解和异构化以及甲基环戊烷的开环和扩环反应[4~9].对Pd的其他性质的研究,还包括采用TPR、TPD、TPO和TPMS等技术,分析了Pd或其合金等金属原子在NaY分子…  相似文献   

16.
Thermal stability and its influence on the catalytic activity in CO oxidation of Cu, Pd and Pd-Cu zeolite systems were investigated. The increasing of catalytic activity in the first cycle of reaction is connected with the thermal decomposition of complexions and consequently with the changing of metal state in catalyst in the case of Cu/ZSM-5catalyst. This activity does not relate to initial zeolite with complex ions, but to the metal ions with the decreasing ligands number in the coordination sphere of metal ion. According to the EPR spectrum the copper ions form clusters in zeolite channels due to the spin changed interaction. It was established ESR method that 1.8% Cu/ZSM-5 catalyst in a reduced form has copper (I and II) ions by. The Pd/ZSM-5 catalysts with different metal content have high catalytic activity below the temperature decomposition in contrary to Cu-containing zeolites. On the one hand, it may be connected with the partial reduction of Pd ions during CO oxidation and, on the other hand, with the ability of Pd ions to form the respective label complexes with reagents as additional ligands. The same character of relation between thermal stability and catalytic activity for Pd-Cu/ZSM-5 catalyst was observed. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

17.
在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.  相似文献   

18.
Reduction of Pd° and decomposition of palladium oxide supported on γ-alumina were studied at atmospheric pressure under different atmospheres (H(2), CH(4), He) over a 4 wt% Pd/Al(2)O(3) catalyst (mean palladium particle size: 5 nm with 50% of small particles of size below 5 nm). During temperature programmed tests (reduction, decomposition and oxidation) the crystal domain behaviour of the PdO/Pd° phase was evaluated by in situ Raman spectroscopy and in situ XRD analysis. Under H(2)/N(2), the reduction of small PdO particles (<5 nm) occurs at room temperature, whereas reduction of larger particles (>5 nm) starts at 100 °C and is achieved at 150 °C. Subsequent oxidation in O(2)/N(2) leads to reoxidation of small crystal domain at ambient temperature while oxidation of large particles starts at 300 °C. Under CH(4)/N(2), the small particle reduction occurs between 240 and 250 °C while large particle reduction is fast and occurs between 280 and 290 °C. Subsequent reoxidation of the catalyst reduced in CH(4)/N(2) shows that small and large particle oxidation of Pd° starts also at 300 °C. Under He, no small particle decomposition is observed probably due to strong interactions between particles and support whereas large particle reduction occurs between 700 and 750 °C. After thermal decomposition under He, the oxidation starts at 300 °C. Thus, the reduction phenomenon (small and large crystal domain) depends on the nature of the reducing agent (H(2), CH(4), He). However, whatever the reduction or decomposition treatment or the crystal domain, Pd° oxidation starts at 300 °C and is completed only at temperatures higher than 550 °C. Under lean conditions, with or without water, the palladium consists of reduced sites of palladium (Pd°, Pd(δ+) with δ < 2 or PdO(x) with x < 1) randomly distributed on palladium particles.  相似文献   

19.
NaLaX, NaX + Co, and NaPdX catalysts are synthesized by modification of NaX zeolite with transition metals (La, Co, Pd). The activity of the prepared materials in catalytic ethanol oxidation is studied in the temperature range of 423–723 K. It is shown that NaPdX and NaX + Co accelerate the reactions of partial and complete oxidation of ethanol as the temperature rises. NaLaX accelerates both intramolecular and intermolecular dehydration of alcohol. It is shown that the NaPdX (1.0% Pd) sample has the highest activity in the complete oxidation of alcohol with the formation of CO2.  相似文献   

20.
采用固态离子交换法制备了系列一价铜改性的ZSM-5催化剂,结合多种表征手段,研究了一价铜改性对碳烟氧化反应催化活性的影响。结果表明,采用固态离子交换法可以制备出高负载量的一价铜改性Cu/ZSM-5分子筛催化剂,而不会破坏ZSM-5分子筛原有微孔结构;随催化剂中一价铜比例的增加,低温还原峰和高温还原峰均向低温段移动,且低温还原峰面积增加。改性催化剂对碳烟氧化反应的催化活性随改性元素比例变化先增加后降低;当铜改性比例超过11%后,铜物种的分散性及催化剂对碳烟氧化反应的催化活性均恶化。同时研究还发现,反应气氛中通入NO可以改善催化剂对碳烟氧化反应的催化效果。  相似文献   

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