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硅钨系列三元杂多阴离子柱撑水滑石的合成、表征及其酸碱催化性能 总被引:5,自引:0,他引:5
从NO_3-LDH出发,通过直接交换反应合成了具有Keggin结构的杂多阴离子SiW_(11)M·(H_2O)O (M为第一系列过渡金属)柱撑水滑石,用元素分析、XRD、IR和DTA对产物的组成和结构进行了表征。结果表明,杂多阴离子进入水滑石层间,使水滑石的层间距从0.92nm增加到1.47nm,且热稳定性有所提高。柱撑产物在异丙醇反应中表现出酸碱双功能催化作用,但酸催化占明显优势。 相似文献
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以硝酸根型水滑石作交换前驱体,通过离子交换法合成了过渡金属离子一、三钛取代的Keggin结构过氧钨硅杂多阴离子柱撑水滑石Zn2Al(OH)6-[SiW11(TiO2)O39]及Zn2Al(OH)6-[SiW9(TiO2)3O37],用元素分析、XRD、IR、XPS、化学分析等手段对产物的组成和结构进行了表征。结果表明,过氧杂多阴离子进入水滑石层间,使水滑石的层间距从0.92nm增加到1.47nm。 相似文献
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Keggin结构磷钨钒杂多阴离子柱撑水滑石的合成、表征与热稳定性研究 总被引:10,自引:1,他引:10
采用水浴液中阴离子直接交换法合成了具有不同钒含量的Keggin结构磷钨钒杂多阴离子PW(12-n)VnO(40)(n=1—5)柱撑水滑石,用元素分析、XRD和IR对柱撑产物的组成和结构进行了表征.XRD结果给出柱撑产物的底面间距达1.47M.DTA结果表明柱撑产物的热稳定性高于水滑石前驱体,且与杂多阴离子中V含量相关.由不同温度下焙烧样品的XRD和IR研究可知,柱撑产物的热分解过程为:<250℃时脱除物理吸附水和层间水;250~400℃范围内脱羟基(同时伴随着层间Keggin离子结构的破坏);400℃以上生成WO3和Mg2V2O7,后者在750℃以上分解为MgO和V2O5. 相似文献
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用水热合成和离子交换方法合成了新的柱撑阴离子粘土Zn2Al-SiW9Mn3,通过XRD,IR,DTA,元素分析等手段对其进行了表征。研究表明,合成的杂多阴离子柱撑粘土的通道高度为1.00nm,红外光谱显示了Keggin结构阴离子的特征振动、柱撑产物的热稳定性高于其前驱体,在马来酸环氧化反应中显示了较高的催化活性。 相似文献
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采用水热合成与离子交换方法,将中心原子为过渡金属(Fe)的钨系过渡金属取代型杂多阴离子FeW_(11)NiO_(39)(H_2O) ̄(7-)(缩写为FeW_(11)Ni)嵌入ZnAl型阴离子层状结构粘土间,获得了大层间距、通道高度达1.32nm的新型层柱微孔化合物。通过XRD、IR及ESR等手段进行了表征。以ZnAl-Few_(11)Ni为催化剂合成邻苯二甲酸二辛酯(DOP),选择性大于99%,转化率由嵌入前的12%提高到近50%,催化活性明显提高。 相似文献
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三元P—Cu—W杂多阴离子柱撑水滑石的制备 总被引:3,自引:1,他引:2
用微波法制备了杂阴离子柱撑水滑石,经XRD,IR,ESR和DTA表征,证明制备的样品具有良好的层柱结构,其热稳定性比相应的杂多酸盐提高约40℃。杂多阴离子中Cu^2^+并非处于标准的八面体场中,而是处于一种近似于五配位的立方锥场,并随嵌入层间后更趋势于民位。 相似文献
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CdS/Rectorite nanocomposites were prepared through hydrothermal method by using Cd[NH2CSNH2]2Ac2 complex as precursor of CdS which was derived from cadmium acetate and thiourea. The obtained nanocomposites were characterized by X-ray diffraction (XRD), Fourier transfer infrared spectra (FTIR), diffusion reflection spectra (DRS), transmission electron microscopy (TEM) and the selected area electron diffraction (SAED) patterns. Experimental results indicate that CdS exist in at least three forms: CdS adsorbed at surface, CdS pillared in montmorillonite-like layers of Rectorite and CdS pillared in the new layered structure formed during the hydrothermal process. Those CdS crystals are hexagonal symmetry. The photoactivity and photostability of the obtained CdS/Rectorite nanocomposites are improved significantly compared to that of the reference Rectorite and pure CdS. 相似文献
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三元P-Cu-W杂多阴离子柱撑水滑石的制备 总被引:2,自引:0,他引:2
用微波法制备了杂多阴离子柱撑水滑石,经XRD、IR、ESR和DTA表征,证明制备的样品具有良好的层柱结构,其热稳定性比相应的杂多酸盐提高约40℃,杂多阴离子中Cu2+并非处于标准的八面体场中,而是处于一种近似于五配位的立方锥场,并随嵌入层间后更趋于五配位。 相似文献
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P-Cu-Mo杂多阴离子柱撑水滑石的制备 总被引:1,自引:0,他引:1
杂多阴离子柱撑水滑石作为一类新型的催化材料,近年来日益受到人们的关注。但由于杂多化合物对碱不稳定及水滑石在酸性条件下层结构易被破环,故文献中仅有制得钨硅系杂多阴离子柱水滑石的报道。作者将过渡金属引入钼磷酸的Keggin结构骨架中,提高了其溶液稳定性,并在微波场中快速地制得了P-Cu-Mo杂多阴离子柱撑水滑石。 相似文献
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Two Mo/SiO2 samples have been prepared by impregnation of silica gel with aqueous solution of molybdophosphoric heteropoly acid or ammonium heptamolybdate. The catalysts were studied by ESR and IR spectroscopy, X-ray diffraction, and XPS. Their activity was measured in the reaction of thiophene hydrodesulfurization. The silica-supported P–Mo heteropoly acid, with a preserved Keggin structure of the heteropoly anion and sulfided by H2S, exhibited two times higher steady conversion in comparison with ammonium heptamolybdate supported on silica at pH=11 and calcined and sulfided at 500°C. 相似文献
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I. C. Chisem S. D. Cosgrove W. Jones 《Journal of Thermal Analysis and Calorimetry》1997,50(5-6):757-766
The rate of removal and uptake of guests into layered and porous materials is important in many areas of materials chemistry. Here we report on the use of atmospheric thermogravimetry linked to a mass spectrometer (TG-MS) to investigate the thermal characteristics of three different solids. We show that (i) the desorption of cyclohexylamine from the surface of a pillared acid activated smectite clay occurs in two stages, indicating two possible acidic binding sites, (ii) TG-MS is an extremely sensitive technique for probing progressive anion exchange of lithium aluminium layered double hydroxides, (iii) on heating, the perhydrate 4Na2SO4·NH4Cl·2H2O2 releases H2O2 intact.We are very grateful to Miss J. Bovey for supplying us with the acid activated clay and for very helpful comments. We would like to thank Rheometric Scientific Ltd. and Leda Mass Ltd. for their advice and co-operation in designing and fitting the transfer line. Financial assistance from the EPSRC through a Quota award to ICC and a CASE award with Solvay Interox Ltd. to SDC is also appreciated. 相似文献
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柱撑化合物Zn2Al-PW11Z的结构模型及酯化活性 总被引:1,自引:1,他引:1
杂多化合物是性能优异的酸型和氧化型或双功能催化剂[1-4],而通式为的阴离子粘土通常具有减催化或还原催化性能[5,6].因此,从在分子及原子水平上设计催化剂,调控催化性能观点出发,人们期望将体积较大的杂多阴离子嵌入阴离子粘土层间,合成大层间距的新型柱撑微孔材料.1988年Pinnavaia等人[7]首次报导了Zn2Al-V10O28是具有2.0nm孔径分布的中微孔材料.最近,笔者将单取代型Keggin结构杂多阴离子GeW11O39Z(H2O)6-(其中Z=Ni2 和Cu2 )和缺位Keggin结构的GeW11O嵌入Zn2Al-NO3层间,合成了通道高度为0.9nm的新型柱撑… 相似文献
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Heteropolyblueisthereducedproductofthepoly oxometalates.Ithasattractedmuchattentionbecauseofitsnovelstructure ,uniquepropertiesandpotentialap plicationsinthefieldsofcatalysis ,pharmaceuticalchemistryandfunctionalmaterials .1 3 Atearlystage ,heteropolybluewa… 相似文献
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IntroductionTheanionicclayisalsocaledlayereddoublehydroxide(notedasLDH),itsuniquebasiccatalyticfunction,interesting“memoryefe... 相似文献
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Sofronia Bouariu Laura Dartu Gabriela Carja 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1263-1271
New inorganic ensembles type layered double hydroxides enriched with silver ions were investigated in terms of thermal behavior and structural evolution by means of TG-FTIR analysis. The studies were focused on two classes of layered precursors, actually distinguished only by the nature of the divalent metal ions, in order to correlate the influence of the clay structure with the thermal behavior of the silver-anionic clay ensembles. The understanding of the thermal degradation mechanism, which is essential to advance the potential applications, requires supplementary characterization techniques such as XRD and FTIR analyses. The thermal analysis performed at three different heating rates revealed the three thermal degradation stages typical for LDHs structure, but different from sample to sample as a consequence of the different interactions between the clay layers and the interlayer anions. The interpretation of the 3D FTIR spectra of the gaseous species resulting in each stage of the thermal degradation process, by means of standard IR spectra, indicates CO2 and H2O as main evolved gasses. Moreover, the evolution curves of the gaseous species released by the thermal degradation in air of the studied anionic clays point out that the two gaseous components are eliminated into the temperature ranges corresponding to those given by TG–DTG. The comparative study of the silver-LDH ensembles from the perspective of the structural evolution during the controlled heating suggest a better response from the ensemble with structure consisting of magnesium as divalent cation in the clay network, meaning a better thermal stability. 相似文献