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1.
Trimodal hierarchical yolk-shell materials consisting of TS-1 core and mesoporous carbon shell(YS-TS-1@MC) was successfully synthesized by using TS-1@mesosilica as hard template,sucrose as carbon source and organic base tetrapropylammonium hydroxide(TPAOH) as silica etching agent.The resultant YS-TS-1@MC contains the micropores(0.51 nm) in TS-1 core,the mesopores(2.9 nm) in carbon shell as well as a void or a stack pore between TS-1 fragcments(TS-1 intercrystal mesopores,~18.4 nm).Under the rigorous etching conditions,the crystalline structure of TS-1 core was well retained.The YS-TS-1@MC served as a good support for palladium nano-particles(Pd NPs) or Rh(OH)x species,giving rise to efficient bifunctional catalysts for the tandem reactions including one-pot synthesis of propylene oxide or amides.  相似文献   

2.
Synthesis of the titanium silicalite TS-1 was first reported by Taramasso et al[1]in 1983. TS-1 has received considerable interest during the last decade because of its unique catalytic properties in oxidation reactions involving H2O2 as the oxidant. It is accepted that the extraframework Ti species in TS-1 favor the decomposition of H2O2and should be avoided. But in the present study, it was observed that there was a kind of Ti species inactive in both the oxidation reaction and the decomposition of H2O2.  相似文献   

3.
The controllable synthesis of one-dimensional(1D) structural morphology of metal-organic frameworks(MOFs) is significant for its application in catalysis,sense and gas separation.In this communication,we report a simple and moderate synthetic strategy to obtain uniform HKUST-1 nanobelts(NBs) by using copper nanowires(Cu NWs) as a metal source as well as a template.The control experiments showed that synergy between metal dissolution rate and crystal formation plays a key role in the formation of nanobelts.Our study represents an attractive synthetic strategy of 1 D MOFs-based material for applications.  相似文献   

4.
A facile method for the shape-selective synthesis of silica nanostructures using a reversemicroemulsion -mediated template(RMMT) technique is reported.In this method,positive poly-Llysine (PLL) is selected as template due to its configuration diversity.By adjusting pH and concentration, PLL demonstrates various secondary structures containing random coil,α-helix andβ-sheet,which result in the formation of silica nanorods,silica nanospheres and silica nanotubes in the reversemicroemulsion system,respectively.Thus,the shape-selective synthesis of silica nanostructures might be achieved by using PLL as structural template in the reverse-microemulsion system.  相似文献   

5.
Cucurbit[n]urils (CB [n]),macropolycyclic compounds self-assembled from an acid-catalyzed condensation of glycoluril and formaldehyde1, can form inclusion complexes with a number of organic substrates in water2. Usually, CB [6] is used in the studies because of its easy synthesis, and the driving forces for its binding are considered to be the hydrophobic effect and dipole-dipole interactions. CB[n] 1Very recently, Kim et al reported the synthesis of CB [5], CB [7], and CB [8]3. They fou…  相似文献   

6.
碘甲烷在碳酸二甲酯直接合成中的作用   总被引:4,自引:0,他引:4  
江琦  李涛  刘峰  黄仲涛 《催化学报》1999,20(6):585-586
Dimethyl carbonate (DMC) is an environmentally friendly compound and a substitutive intermediate for highly toxic phosgene or dimethyl sulfate in carbonylation and methylation reactions as well as a promising octane booster. The common methods for its preparation are the oxidative carbonylation of methanol catalyzed by a variety of transition metal ions and the transesterification of ethylene carbonate or propene carbonate with methanol[1]. The direct synthesis of DMC from carbon dioxide and methanol is a challenging route in which the most abundant carbon resources and a main greenhouse gas is used as feedstock. A new method for the direct synthesis of DMC catalyzed by the methoxide of main group metal has attracted more and more attention since it was reported[2~6] . However the lower conversion of the reaction has become the main obstacle for its application. In this letter, an efficient promoter for the direct synthesis of DMC is reported.  相似文献   

7.
合成钛硅分子筛TS-1的一种新方法   总被引:4,自引:0,他引:4  
In both conventional method[1] and modified method[2] ,organic Si and Ti alkoxides were used as Si source and Ti source respectively, and only strong organic base was used. So this system may be called as organic synthesis one (see Fig 1 )Thangaraj et al[3] reported that in the organic synthesis system only organic strong base TPAOH can be used.  相似文献   

8.
1 IntroductionFullerene has received considerable attention and a great researching interest due to its unique structure and interesting properties[1-3].Many functional groups have been introduced,often region-or stereo-selectively,for tuning the physical properties of C60 and for constructing supramolecular architectures[4-6].Among all kinds of C60 derivatives,the diseotic molecule-substituted C60 derivatives show interesting properties,especially,liquid crystal properties.Up to now,few C60 derivatives with discotic-molecular groups and their liquid crystal properties have been studied.In 1996,Deschenaux et al.[7]reported the first mesomorphic C60-ferrocene derivative.Tian et al.[8]synthesized a C60-perylene derivative in 2004.Nakanishi et al.[9]prepared a series of uncommon liquid C60derivatives with 2,4,6-tris(alkyloxy)benzal groups in 2006.Lately,Geerts et al.[10]described the synthesis of mesogenic phthalocyanine-C60.  相似文献   

9.
Since the discovery of ZSM-5 molecular sieves as a promising catalyst material, the synthesis of ZSM-5 has been investigated in great detail. In the first synthesis of ZSM-5,tetrapropylammonium(TPA) was used as the templating agent. However, the industrial manufacture and application of ZSM-5 molecular sieves arc limited because TPA, the templating agent, is expensive. In the attempt to search for a suitable substitute for TPA,  相似文献   

10.
Novel method for synthesis of titanium silicalite-1 (TS-1)   总被引:2,自引:0,他引:2  
Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3· H2O, HDA or TEAOH etc. as base sources. In this system, TPA cations (come from TPABr or TPAOH) served as tern-plating agents to direct the MFI structure. NH3H2O, TEAOH or HDA etc. provides the alkalinity necessary for crystallization. X-ray diffraction, UV-Vis, ER spectroscopies, SEM, 29 Si MAS NMR showed that the zeolites obtained possessed all the structural characteristics of TS-1, and titanium atoms were introduced into the framework in TS-1. This material was proved to have high crystallinity and high catalytic activity to allyl chloride epoxidation and propylene epoxidation. All the samples synthesized had similar catalytic properties with a standard TS-1 through compared inorganic reactant system with organic synthesis system using propylene epoxidation. The effects of silicon source and TPABr/SiO2 ratio were discussed.  相似文献   

11.
IntroductionSynthesisgas(HZ CO)isproducedfrommethanemoshybysteamrefonningwhichsuffersfromlimitationssuchasveryhighenergyrequirements,complicatedequipmentandinstallations,highHZ/COproductratioandpoorselectivityforcarbonmonoxide.Recently,manyresearchershave…  相似文献   

12.
The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM)have been investigated over ternary and binary metal oxide catalysts.The catalysts are prepared by doping MgO-and CeO2-based solids with oxides from alkali(Li2O),alkaline earth (CaO),and transition metal groups (WO3 or MnO).The presence of the peroxide (O2^2-)active sites on the Li2O2,revealed by Raman spectroscopy,may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts.The high reducibility of the CeO2 catalyst,an important factor in the CO2-OCM catalyst activity,may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobitity and oxygen vacancies in the CeO2 catalyst.raman and Fourier Transform Infra Red (FT-IR)spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks carresponding to the buld crystalline structures of Li2O,CaO,WO2 and MnO are detected.The performance of 5%MnO/15?O/CeO2 catalyst is the most potential among the CeO2-based catalysts,although lower than the 2%Li2O/MgO catalyst.The 2%Li2O/MgO catalyst showed the most promising C2 hydrocarbons selectivity and yield at 98.0%and 5.7%,respectively.  相似文献   

13.
The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may  相似文献   

14.
铁系催化剂一直是合成氨及制氢工业中一氧化碳变换反应最常用的催化剂。运用X射线衍射(XRD)、程序升温还原(TPR)及活性评价技术研究了添加金属氧化物对铁系催化剂的晶相结构、催化剂的稳定性和催化活性的影响。结果表明,不同的金属氧化物对催化剂结构的稳定作用和活性影响不同,其中CeO2和Bi2O3都能增强铁系催化剂的稳定性,提高催化剂的活性。  相似文献   

15.
The Catalytic performances for methane steam reforming reaction ofNi/Al_2O_3(commercial), Ni/Al_2O_3 (developed surface )and Ni/Al_2O_3-R_xO_y (R israre earth oxide) Catalysts were investigated by means of X-ray diffraction,TG, SEM/ X-ray analysis, pulse gas chromatography,BET and Mercuryporsiniter techniques. The distribution of rear earth oxides on the supports,themetal-support (additives) interaction and the influence of rare earth oxideadditives on the dispersion of active components,catulytic activities,variationof nickel crystallites size,CO chemisorption,formation of NiAl_2O_4 as well asthe reducibility of the catalysts were examined.The presence of rare earthoxides in the Ni/Al_2O_3 (developed surface) results in great improvement ofstubility through suppressing the growth of Ni crystallites,the oxidation of themetallic Ni and the formation of NiAl_2O_4. The effect of heavy rare earth oxidesis more distinct than that of the light ones.Strong metal support interaction(SMSI) exists in Ni/Al_2O_3- R  相似文献   

16.
考察了稀土系列氧化物作为CO同步还原SO2和NO催化剂的活性,结果表明,氧化钐和氧化钕表现了最高的活性,在475℃,SO2和NO的转化率同时超过95%,实验发现稀土氧化物是活性相,通常脱硫活性高的样品同样具有高的脱氮活性,但CeO2表现了不同的行为,其脱硫性虽低,但脱氮活性却较高,文中还对同步反应的机理作了探讨,发现COS不仅是还原SO2的中间物,同时也是还原NO的中间物。结合活性相和反应机理对不同稀土氧化物的活性差异作了讨论。  相似文献   

17.
Co-M(M=La,Ce, Fe,Mn, Cu,Cr)复合金属氧化物催化分解N2O   总被引:1,自引:0,他引:1  
薛莉  贺泓 《物理化学学报》2007,23(5):664-670
通过共沉淀法制备了一系列Co-M(M= La, Ce, Fe, Mn, Cu, Cr)复合金属氧化物及纯Co3O4催化剂, 考察了其催化分解N2O 的活性. 结果表明在研究的系列催化剂中, Co-Ce 复合氧化物催化剂具有最好的催化分解N2O的活性; 其活性与Ce/Co 摩尔比有直接的关系, 当Ce/Co 摩尔比为0.05 时(CoCe0.05 催化剂)催化活性最佳; 当有NO 和O2共存时, 可能在催化剂活性中心上形成表面硝酸盐或亚硝酸盐吸附物种而使其活性受到较大影响. 通过对Co-M 催化剂的XRD、BET、O2-TPD及H2-TPR 等表征结果的分析, 发现作为主要活性位的Co2+的氧化还原能力是影响催化剂活性的主要原因. 这是因为根据反应机理, N2O 的表面分解步骤与Co2+氧化成Co3+的能力相关, 而吸附氧的脱附与Co3+还原成Co2+的能力相关. 在所研究的催化剂中, 添加除CeO2之外的其它过渡金属氧化物时, 催化剂中Co3+/Co2+的氧化还原能力降低, 因此其催化性能降低. 另外, 添加不同过渡金属氧化物也改变了N2O 催化分解反应的速控步骤.  相似文献   

18.
采用共沉淀法制备了不同锆铈摩尔比的Ce1-xZrxO2(x=0,0.1,0.3,0.5,0.7,0.9和1.0)氧化物,并以改性的浸渍法制备了金担载量为1%(质量分数)的Au/Ce1-xZrxO2催化剂.考察了催化剂在低温CO氧化和水煤气变换反应中的催化性能.应用氮物理吸附、X射线衍射、透射电镜和H2程序升温还原等技术对氧化物载体及其负载金催化剂进行了表征,并与其催化性能进行了关联.结果表明,与纯CeO2和ZrO2相比,Ce1-xZrxO2的比表面积增大而孔径减小,孔分布更加集中.Zr的加入使表面Ce4 的还原更加困难,使体相Ce4 的还原更加容易.活性组分金的加入有利于铈锆氧化物的还原.ZrO2载体较大的孔径使金在载体表面分散均匀而粒子较小,因此与Au/CeO2和Au/Ce1-xZrxO2相比,Au/ZrO2具有更好的低温CO氧化活性和水煤气变换活性,而Au/CeZrO在高温下的水煤气变换反应中表现出更好的催化性能.  相似文献   

19.
在考察了多种金属氧化物在微波场下升温性能的基础上,制备了用于烹饪油烟催化净化的非贵金属催化剂.实验表明,VB族、V族、B族和B族元素氧化物在微波中升温效果明显,其中Co、Ni和V三种元素氧化物的升温效果最好.涂覆氧化铝的蜂窝堇青石负载V2O5的催化剂具有较稳定的吸波升温性和高油烟催化净化活性.添加La2O3后负载型V2O5催化剂活性明显增加,在微波条件下,含有1%La2O3的负载型V2O5催化剂在150℃可使油烟净化率达到88%以上.  相似文献   

20.
以γ-Al_2O_3为载体,用浸渍法负载碱金属和碱土金属氧化物制备了一系列羰基硫水解催化剂。采用微反-色谱联用装置考察了45—100℃低温区内的活性变化规律。结果表明,催化剂活性与金属氧化物组分及含量有着密切关系。在考察各催化剂在不同温度下水解反应速度常数(K)的变化中,发现指前因子(A)与活化能(E)之间存在着补偿效应,活化能增大时指前因子也随之增大。补偿效应参数(K_0)和能量分布指前因子(1/b)均与负载的金属离子半径(d_m)有关。求得了各催化剂的等动力学温度(T),讨论了羰基硫水解反应中存在补偿效应的原因。  相似文献   

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