乙二胺四乙酸柱撑镁锌铝三元水滑石的制备与表征

采用共沉淀法合成了Mg2ZnAl-CO3水滑石;以其为前驱体,利用离子交换法进行插层组装得到Mg2ZnAl-EDTA三元柱撑水滑石;采用X射线衍射仪和傅立叶变换红外光谱仪对产物进行了表征.结果表明,合成的Mg2ZnAl-CO3水滑石纯度高、晶型良好,其层间CO32-可被乙二胺四乙酸(EDTA)阴离子取代形成Mg2ZnAl-EDTA三元柱撑水滑石;柱撑水滑石的层间距离明显增加,EDTA阴离子在层间倾斜排列.     

MgAl-PdCl4 水滑石的合成与表征

以MgAl-NO3水滑石为前驱体,用离子交换法将PdCl42-作为客体插入水滑石的层间,通过XRD、IR、DTA、比表面积等表征制备的水滑石,探讨了Pd含量、插层时间、Mg/Al摩尔比以及焙烧温度对制备水滑石结构的影响.结果表明,插层产物中PdCl42-与NO3-共存于层间,PdCl42-的引入,减小了水滑石的层间距,PdCl42-引入量越多,层间距减少的越多.Mg/Al摩尔比在2～4均可以形成MgAl- PdCl4-HLTcs,但是其值增大时,水滑石的层间距逐渐降低.插层交换时间延长有利于PdCl42-插入层间,但从制备水滑石的角度看,晶化时间8 h,即可得到结晶良好的水滑石化合物.DTA分析结果显示,在较高的PdCl42-引入量,或较高的Mg/Al摩尔比时层间PdCl42-失去Cl-转化成PdO的温度在370 ℃左右,层间NO3-的脱除温度在410 ℃附近;在低的PdCl42-引入量,或低的Mg/Al摩尔比两个脱除过程一起进行,在500 ℃左右完成.随着层间PdCl42-的分解及NO3-的脱除,400 ℃时MgO-Al2O3-PdO物相开始形成,600 ℃时基本形成完全,比表面积也达到最大,进一步提高焙烧温度至800 ℃,由于金属氧化物的晶粒变大及出现少量的MgAl2O4尖晶石物相,其比表面积有所下降.     

酸性黄25插层水滑石薄膜的制备及其性能研究

采用原位生长法在铝片基底表面制备了ZnAl-NO3-LDHs水滑石薄膜,以其为前驱体,在弱酸性条件下通过离子交换反应将酸性黄25阴离子插层至ZnAl-LDHs/Al薄膜层间,制备了酸性黄25插层水滑石薄膜,并采用XRD、SEM、FTIR、TG-DTA、UV-Vis和色差计等手段对薄膜进行了表征。XRD和FTIR表征结果表明,酸性黄25阴离子成功地插层到了水滑石薄膜层间,ZnAl-LDHs的层间距由0.87 nm增加到2.96 nm,NO3-阴离子在1 384 cm-1处的特征吸收峰消失,同时出现了酸性黄25阴离子的特征吸收峰。SEM照片显示,水滑石晶片主要以c轴平行于铝片基底生长。TG-DTA分析、UV-Vis分析、色差分析和紫外光老化结果表明,插层后酸性黄25阴离子的耐热性和耐光性均得到了提高。     

酸性橙插层锌铝水滑石的组装及其结构与性能

采用共沉淀法合成酸性橙阴离子插层锌铝水滑石(Zn/Al-AO7 LDHs),研究不同pH值及原料金属离子配比对产物结构的影响,利用X射线粉末衍射(XRD),热分析(TG-DTA),傅里叶变换红外(FT-IR)等表征手段,对插层产物的结构进行表征,确定了制备酸性橙插层锌铝水滑石的最适宜条件.用量子化学的B3PW91/6-31G(d,p)方法对Zn/Al-AO7 LDHs模型分子的空间几何构型进行了优化,通过结构组合得到的层间距为2.33 nm,接近XRD测试得到的层间距,从而说明了酸性橙离子在水滑石层板间的排列方式.进一步以甲酰胺为溶剂对水滑石层板进行剥离,得到澄清溶液,根据剥离产物的XRD谱可以确定剥离实验成功.     

基于氟碳表面活性剂插层水滑石的聚酰亚胺纳米复合材料的制备与性能

以氟碳表面活性剂全氟辛基磺酸钾为插层剂,通过离子交换制备插层水滑石,并以其为填料,通过原位插层聚合方法,制备了水滑石/氟碳表面活性剂/聚酰亚胺纳米复合材料.用X射线衍射、红外光谱和热失重等方法分析插层水滑石结构.结果表明,全氟辛基磺酸钾插层水滑石后,水滑石的层间距由0.76 nm增加到2.52 nm,在水滑石层间构建了氟碳链的微环境.这种氟化水滑石可剥离分散于聚酰亚胺基体中,改善了纳米复合材料的气体阻隔性能、介电性能和机械性能.这种影响不仅体现无机纳米片层的杂化效果,而且展示出氟碳链的特点.     

焦磷酸根嵌入后形成的交联水滑石的研究

合成了焦磷酸根交联水滑石，用XRD，FT－IR，DTA－TG，MASNMR等手段研究了焦磷酸根嵌入后形成的水滑后，提出了嵌入水滑石层间最多的离子为H2P2O7^2-，高温灼烧，P2O7^4-柱子交联到层上，且焦磷酸根离子链垂直位于水滑石层中，产物表面积为87m^2/g。     

过氧杂多阴离子型层柱化合物的合成、表征及催化活性

通过离子交换法,将含Zr过渡金属离子1,3取代钨硅、钨磷过氧杂多酸盐嵌入Zn2Al类水滑石中,获得了层柱化合物,并用XRD,IR,UV等手段对产物的结构进行了表征.结果表明过氧杂多阴离子进入水滑石层间后,水滑石的层间距从0.92增大到1.47 nm,且过氧链没被破坏.层柱化合物在酯化反应中显示优良的催化性能.     

层板剥离水滑石的制备及影响因素

采用阴离子表面活性剂N-月桂酰基谷氨酸(LG)为插层分子，研究了烷烃-LG-水(O/W)微乳液中烷烃量的变化对插层水滑石层间距的影响，同时研究了烷烃分子大小和水滑石层板阳离子不同对水滑石剥离难易程度的影响。实验表明，随着微乳液中烷烃含量的增加，制备得到了由插层到层板剥离的水滑石，并且烷烃的链长越长，水滑石的剥离越容易实现。层板化学组成对剥离难易程度也有影响，难易程度依次是Mg/Al-LDH，Zn/Al-LDH和Ni/Al-LDH。     

C/MgAl水滑石复合材料为前驱物所制催化剂在柠檬醛-丙酮缩合反应中的催化性能

在MgAl水滑石的合成体系中引入不同量的葡萄糖,得到了系列C/MgAl水滑石复合材料。该复合材料经550℃焙烧后,形成MgAl复合金属氧化物。该MgAl复合金属氧化物在含水的反应体系中可原位活化形成插层阴离子为OH-的MgAl水滑石催化剂(meixnerite)。采用XRD、N2吸附、元素分析和碱性能测试等手段对所制meixnerite催化剂的物化性能进行了表征。结果表明,以C/MgAl水滑石复合材料为前驱物所制备的meixnerite催化剂,较以常规的MgAl水滑石为前驱物所制催化剂具有较高的比表面和更多可接近的碱性位。这些特征使以C/MgAl水滑石复合材料为前驱物所制备的meixnerite催化剂在柠檬醛-丙酮缩合反应中的催化活性高于常规的以MgAl水滑石为前驱物所制备的催化剂。此外,本文还对合成体系中葡萄糖的引入量和反应条件对所制催化剂的催化性能的影响进行了考察。     

水滑石层间碘酸根离子的还原性机理研究

通过X射线衍射(XRD)和傅里叶变换红外(FTIR)光谱仪表征发现,经水合肼(N2H4·H2O)和亚硫酸钠(Na2SO3)两种还原剂处理碘酸根插层水滑石的产物分别为碘离子插层的水滑石(ZnAl-I LDHs)和硫酸根离子插层水滑石(ZnAl-SO4LDHs)。进一步研究表明,N2H4·H2O和水滑石的反应为D7模型的核外层扩散反应,N2H4·H2O在水滑石微球界面和IO3-发生反应。而Na2SO3则先进入了水滑石层间,然后与层间的IO3-反应,其模型符合D11动力学模型。     

Mg-Al水滑石催化甘油与碳酸二甲酯的酯交换反应简

报道了温和条件下甘油和碳酸二甲酯在一系列不同Mg/Al比（0.5-6）的Mg-Al水滑石催化下合成碳酸甘油酯（GC）的反应. 发现,Mg-Al水滑石对该反应具有很高的GC选择性,其中Mg/Al=2经400℃处理所得水滑石催化效率最高：70 ℃反应3 h甘油转化率达66.9%时,GC选择性维持在97%以上. 表征结果表明,水滑石样品的比表面积、孔径、结晶度和表面碱性对其催化活性影响很大.     

Preparation of supported metal catalysts starting from hydrotalcites as the precursors and their improvements by adopting “memory effect”

Hydrotalcite-like compounds (HTlcs) can be used as the catalysts as it is since they contain various transition metal cations as the catalytically active species well dispersed on the basic support materials. Moreover, increasing numbers of the applications of HTlcs after the heat treatment have been found since the oxides with very small crystal size, stable to thermal treatments, are obtained after the calcination. The oxides possess interesting properties such as high surface area, basic properties and further form small and thermally stable metal crystallites by reduction. Moreover, the calcined oxides show a unique property, i.e., “memory effect,” which allows the reconstitution of the original hydrotalcite structure. We have developed the catalytic applications of hydrotalcites as it is and moreover the mixed oxides derived from hydrotalcites for various catalytic reactions, i.e., oxidation, dehydrogenation and reforming of hydrocarbons, and even for the reforming of methanol and the CO shift reaction. Aerobic oxidation of alcohols, Baeyer−Villiger oxidation of ketones and O₃ oxidation of oxalic acid have been successfully carried out with the Mg−Al hydrotalcites containing Ni, Fe and Cu, respectively, as the catalysts in liquid phase. In the O₃ oxidation of oxalic acid, the catalytic activity was enhanced by the “memory effect,” i.e., Mg(Cu)–Al hydrotaclite was reconstituted on the surface of Mg(Cu,Al)O periclase particles and oxalic acid was incorporated as anions in the hydrotalcite layer, resulting in an enhanced oxidation of oxalic acid. As the catalysts in the vapor phase reactions, Mg/Fe/Al mixed oxides prepared from Mg–Al(Fe) hydrotalcites and effectively catalyzed the dehydrogenation of ethylbenzene. Supported Ni metal catalysts have been prepared from Mg(Ni)–Al hydrotalcites and successfully used in the steam reforming and the oxidative reforming of methane and propane. Moreover, the Ni catalysts have been improved by combining a trace amount of noble metals by adopting the “memory effect” and used in the production of hydrogen for the PEFC under the daily startup and shutdown operation. Also starting from aurichalcite or hydrotalcite precursor as the precursor, Cu/Zn/Al catalysts with high Cu metal surface area have been prepared and successfully applied in the steam reforming of methanol and dimethyl ether, and moreover in the CO shift reaction.     

Catalyst design of hydrotalcite compounds for efficient oxidations

Various Mg-Al type hydrotalcites were examined as catalysts for the epoxidation of olefins and N-oxidation of pyridines using hydrogen peroxide. The catalytic activity of hydrotalcites increased with increasing the basicity of their surface. Adding cationic surfactants, e.g., n-dodecyltrimethylammonium bromide, to the above system remarkably accelerated the reaction rate. The hydrotalcites, into which were introduced both Ru and Co cations in the Brucite layers, were found to be good catalysts for the oxidation of various alcohols in the presence of molecular oxygen. Moreover, these hydrotalcites could smoothly catalyze also the oxygenation of diphenylmethane, fluorene, and xanthene at benzylic position with excellent yields. The hydrotalcite catalysts could be easily separated from the reaction mixture and reused with retention of their high catalytic performance for the above oxidations.     

Structure and base properties of calcined hydrotalcites

Five hydrotalcites with Mg/Al molar ratio range of 3-15 were prepared. The structure and basicity of Mg-Al mixed oxides (Mg(Al)O) transformed from hydrotalcites were investigated by TPD, XPS, XRD, FT-IR and NMR techniques. The results of elemental analysis and XPS indicate that Al is enriched in the surface regions of Mg(Al)0, and its amount increases with the Mg/Al molar ratio and the calcination temperature. 27Al-MAS-NMR results show that Al exists in two chemical environments: tetrahedral aluminium (Al(t)) and octahedral aluminium (Al(o)) in Mg(Al)O. The amount of Al(t) increases with the Mg/Al molar ratio and the calcination temperature. It is assumed that Al(t) may be mainly from the surface Al. Temperature-programmed desorption (TPD) of CO2 shows that the number of basic sites of Mg(Al)O samples increases with the Mg/Al molar ratio, and the maximum number of basic sites is obtained for hydrotalcite calcined at 773 K. Infrared spectra of adsorbed CO2 and B(OCH3)3 reveal that there are two kinds of     

载Ni双功能碱性沸石催化剂的研究

采用分步浸渍法制备了负载Ni和KOH的NaX沸石催化剂 ,用XRD、TPR、CO2 TPD和XPS等手段对样品的结构、表面碱性、金属组分的可还原性、表面Ni物种的形态等进行了表征 ,对金属组分和碱性组分间的相互作用进行了研究 ,并揭示了这种作用的本质.同时结合丙酮一步法合成甲基异丁基酮的反应 ,探讨了反应性与样品碱性、金属性的关系 ,阐明了该反应中双功能催化剂上金属组分与碱性组分必须匹配合宜的原因     

Cu(Al)O复合物表面酸碱性质的微量吸附量热研究

673K分解Cu/AI物质的量比分别为0．5、1和2的Cu-AI水滑石转化为Cu(AI)O复合物。XRD测定仅显示CuO物相,表明组成成分较均一。微量吸附量热法测定Cu(AI)O复合物表面酸碱中心的强度和数量,给出了吸附分子CO2／NH3的吸附曲线。量热结果展示,样品的酸中心强度顺序是：0．5CAO＞CAO＞2CAO,而碱中心强度顺序是：0．5CAO＜CAO＜2CAO。显然,样品的酸性（碱性）随着AI(Cu)含量的提高而逐渐增强。研究表明,样品的NH3和CO2起始吸附热与其Sanderson电负性线性相关。     

Toward optimized high-relaxivity MRI agents: thermodynamic selectivity of hydroxypyridonate/catecholate ligands

The thermodynamic selectivity for Gd(3+) relative to Ca(2+), Zn(2+), and Fe(3+) of two ligands of potential interest as magnetic resonance imaging (MRI) contrast agents has been determined by NMR spectroscopy and potentiometric and spectrophotometric titration. The two hexadentate ligands TREN-6-Me-3,2-HOPO (H(3)L2) and TREN-bisHOPO-TAM-EA (H(4)L3) incorporate 2,3-dihydroxypyridonate and 2,3-dihydroxyterephthalamide moieties. They were chosen to span a range of basicity while maintaining a structural motif similar to that of the parent ligand, TREN-1-Me-3,2-HOPO (H(3)L1), in order to investigate the effect of the ligand basicity on its selectivity. The 1:1 stability constants (beta(110)) at 25 degrees C and 0.1 M KCl are as follows. L2: Gd(3+), 20.3; Ca(2+), 7.4; Zn(2+), 11.9; Fe(3+), 27.9. L3: Gd(3+), 24.3; Ca(2+), 5.2; Zn(2+), 14.6; Fe(3+), 35.1. At physiological pH, the selectivity of the ligand for Gd(3+) over Ca(2+) increases with the basicity of the ligand and decreases for Gd(3+) over Fe(3+). These trends are consistent with the relative acidities of the various metal ions;- more basic ligands favor harder metals with a higher charge-to-radius ratio. The stabilities of the Zn(2+) complexes do not correlate with basicity and are thought to be more influenced by geometric factors. The selectivities of these ligands are superior to those of the octadentate poly(aminocarboxylate) ligands that are currently used as MRI contrast agents in diagnostic medicine.     

xK/MgAlO型催化剂催化碳烟燃烧的机理研究

通过等体积浸渍法制备了不同K掺杂量的镁铝水滑石复合氧化物(xK/MgAlO),利用X射线衍射光谱及暂态响应、扫描电子显微镜、傅里叶变换红外光谱、X射线光电子能谱及程序升温等技术比较了焙烧和未焙烧的MgAlO形貌结构和晶型的异同,在含硫气氛中研究了K对镁铝水滑石复合氧化物形貌结构和催化碳烟燃烧性能的影响,阐明了反应过程中K掺杂的xK/MgAlO型催化剂降低碳烟起燃温度的关键机制。结果表明,焙烧后的镁铝水滑石3R层状结构消失,出现了尖晶石相,层状结构坍塌变为球形颗粒状;掺杂钾后的催化剂(K/MgAlO)表面活性氧与晶格氧的比例增大,使得氧空位的数量增多,有效提高了催化剂的催化反应活性。在模拟烟气实验中发现掺杂量x=7的(7K/MgAlO)催化剂在含SO_2的混合气中使碳烟的起燃温度降低了127℃,且对NO_x的转化率显著增强。     

Reactivity of cyclohexene using ordered mesoporous materials based on calcined CoFeAl hydrotalcite-supported CoMo catalysts

Co²⁺, Fe³⁺ and Al³⁺ tertiary hydrotalcite-type solids were synthesized, calcined and impregnated with Mo (15 wt% MoO₃) and Co (3Mo:Co) in order to get different catalytic precursors: CoMo/CoFeAl. As-synthesized hydrotalcites and their catalytic precursors were characterized by different physicochemical techniques, such as: X-ray fluorescence, N₂ adsorption–desorption isotherms (BET specific surface area, BJH pore volume and diameter), Fourier transform infrared spectroscopy, X-ray diffraction and temperature-programmed desorption of carbon dioxide. These CoMo/CoFeAl catalytic precursors were previously pre-sulfided with CS₂ and tested in the cyclohexene hydrogenation reaction. Results indicated that these sulfide catalysts showed very low activity in comparison with the conventional CoMo/Al₂O₃ catalyst used as reference, possibly to their high basicity. These catalysts could have the advantage of retaining the octane number of gasoline, by low hydrogenation of olefins.     

Mg-Al hydrotalcites as the first heterogeneous basic catalysts for the Kornblum oxidation of benzyl halides to benzaldehydes using DMSO

Mg-Al hydrotalcites (Mg/Al = 2, 3, 5) act as efficient heterogeneous base catalysts for the conversion of benzyl halides to the corresponding benzaldehydes using DMSO as an oxidant.