柱撑粘土分子筛的红外光谱研究

用红外光谱法测定了混合金属羟基配合物柱撑粘土的表面酸性和表面羟基振动。结果表明，粘土和柱撑粘土均具有Ｌｅｗｉｓ酸和Ｂｒｏｎｓｔｅｄ酸（分别简称Ｌ酸和Ｂ酸）中心，且以Ｌ酸为主；不同柱剂交联的柱撑粘土的表面酸性也有所不同；层间柱是柱撑粘土酸性的重要来源，焙烧后它可转变成氧化物柱并释放出质子而产生Ｌ酸和Ｂ酸中心；柱撑粘土分子筛的羧基谱带主要来自六配位铝，其强度随焙随焙烧温度升高而下降；层间柱的稳定对其表     

NMR研究超稳Y分子筛水热老化过程中结构与酸性的变化

利用固体核磁共振（NMR）结合探针分子技术，探讨了超稳Y分子筛在水热老化过程中酸中心结构和酸性的变化规律.结果表明，水热老化初期，大量的骨架铝脱出最终形成了非骨架五配位铝，使得丙酮探测到的Brønsted酸（B酸）酸量随着老化时间的增加而减少.而非骨架五配位铝会向表面迁移并形成多聚铝，使得分子筛中Lewis酸（L酸）酸量也随老化时间的增加而减少.在老化过程的前3 h内，酸量的变化幅度较大.整体硅/铝原子比相等的分子筛，其B酸酸量的变化幅度与新鲜剂的晶胞大小呈正比；随着老化时间的继续增加，不同配位的铝物种的含量趋于稳定，B酸和L酸的酸量变化幅度很小.在整个水热老化过程中，超稳Y分子筛中B酸和L酸的协同效应一直存在，由协同效应产生的一种酸性增强的B酸位的稳定性最好.     

Assessment of surface acidity in mesoporous materials containing aluminum and titanium

The surface acidity of mesoporous molecular sieves of aluminum and titanium was evaluated using four different techniques: n-butylamine volumetry, cyclohexylamine thermodesorption, temperature-programmed desorption of ammonia and adsorption of pyridine. The nature, strength and concentration of the acid sites were determined and correlated to the results of a probe reaction of anthracene oxidation to 9,10-anthraquinone (in liquid phase). In general, the surface acidity was highly influenced by the nature, location and coordination of the metal species (Al and Ti) in the mesoporous samples. Moderate to strong Brönsted acid sites were identified for the Al-MCM-41 sample in a large temperature range. For mesoporous materials containing Ti, the acidity was represented by a combination of weak to moderate Brönsted and Lewis acid sites. The Ti-HMS sample exhibits a higher acidity of moderate strength together with a well-balanced concentration of Brönsted and Lewis acid sites, which enhanced both conversion and selectivity in the oxidation reaction of anthracene.     

H and P solid-state NMR of trimethylphosphine adsorbed on heteropolytungstate supported on silica

Trimethylphosphine (TMP) has been used as an NMR probe in order to determine the acidity of Keggin-type 12-tungstophosphoric heteropolyacid (HPW), pure and supported on silica, dehydrated at 473 K. Adsorption of TMP on pure dehydrated HPW leads to the formation of trimethylphosphonium ions (TMPH⁺) characteristic of the presence of strong Brönsted acid sites. TMP replaces the water molecules lost by dryness and allows the Keggin secondary structure to recover.Silica interacts with TMP by two kinds of acid sites: with weak acid support sites through the isolated silanol groups and with strong Brönsted acid, which lead to the formation of TMPH⁺, through the hydrogen-bonded silanol groups. Silica only interacts with HPW through its isolated silanol groups.     

Stable nitrogen isotopes in essential versus non-essential amino acids of different plankton size fractions

The stable nitrogen isotope values (delta(15)N) of the essential amino acid (EAA) leucine and the delta(15)N values of six non-essential amino acids (NEAAs) from plankton size fractions from the South China Sea (SCS) were analysed. Data from the SCS were collected during two cruises in July 2003 and 2004 onboard of RV Nghien Cuu Bien. The delta(15)N values of alanine, aspartic acid, glutamic acid and leucine increased with size at all sites. The delta(15)N of glycine did not increase with size, the delta(15)N of tyrosine increased with size only at offshore stations and the delta(15)N of proline increased with size only at inshore stations. We found highly significant correlations between the delta(15)N ratios of leucine to the delta(15)N ratios of glutamic acid, proline, alanine, tyrosine and aspartic acid at oligotrophic sites of enhanced nitrogen fixation. In contrast thereto these correlations were less distinct or absent at more eutrophic sites of low nitrogen fixation. A comparison with an independent data set from the tropical North Atlantic revealed intriguing similar patterns. We interpret these patterns as result of the connected metabolism of EAA and NEAA in zooplankton at sites of nitrogen limitation.     

Laser-Induced Fluorescence of Base Adsorbed on Surface Sites in Solid Catalysts

The interaction of quinoline with the surface of Nafion-H and Nafion-H (13 wt%)/silica gel composites, silica gel itself, HY zeolite, dealuminated or not, and two types of alumina is studied by laser-induced fluorescence. Strong Brønsted acid sites interact with quinoline to form the quinolinum, that ion being revealed by a band peaking at 390 nm. When Lewis acid sites are present, a complex formed between these sites and quinoline is observed. A dimeric species and the diffusion of the adsorbates on the surface of the Nafion-H polymer are discussed.     

Study of the structural modifications in activated clays by Mössbauer spectroscopy and X-ray diffractometry

In this work we study the changes induced on the structure of a smectite clay by chemical acid activation with HCl using X-ray diffractometry (XRD) and transmission Mössbauer spectroscopy (TMS) techniques. By XRD we were able to determine the mineralogical composition of the clay samples and measure the changes in the interplanar distance associated to the structural modifications in the clays. We measured a reduction in the interplanar distance and reflection intensity as the acid concentration in the activation process increased. TMS allowed us identify and characterize the structural sites occupied by ferric and ferrous iron cations. In addition, we were able to monitor the effects caused by the chemical acid activation on the valence state of the iron cations that occupy these structural sites in the clay. For the treatment at low acid concentration, keeping time and temperature of activation constant, our results showed a strong effect on the ferrous and ferric iron sites, reducing and increasing their adsorption relative areas respectively.     

SO2-4/TiO2固体酸的红外和拉曼光谱研究

用ＩＲ、Ｒａｍａｎ光谱研究了ＳＯ＾２－４／ＴｉＯ２固体酸在不同烧温度下的结构、晶相转变和表面酸中心。结果表明,ＳＯ＾２－４与ＴｉＯ２表面的结合为螯合式双配结构。当烧结温度小于５００℃时,ＳＯ＾２－４／ＴｉＯ２样品具有较高的结构稳定性,晶相结构以锐钛矿为主,表面Ｂ酸位数目约是Ｌ酸位数目的２倍,当烧结温度大于５００℃时,随着烧结晶度的升高,表面结合的ＳＯ＾２－４逐渐流失,晶相从锐钛矿转变为金红石,表面Ｂ酸位减少并消失。     

FT-IR study of the acid sites on the surface of silica supported ruthenium oxide

FT-IR spectra of adsorbed CO, pyridine and acetone indicate that on the surface of RuO₂/SiO₂ are present Brønsted and Lewis acid sites and different reduced metal sites.     

Investigation of ethene adsorption on Hmordenite and modified Hmordenite by frequency response method

The frequency response (FR) technique has been applied to study adsorption mechanism of ethene in parent Hmordenite (HMor) and the HMor (CuO/HMor, Cs⁺/HMor) which were modified by CuO and Cs⁺. The FR spectra of ethene in HMor, CuO/HMor and Cs⁺/HMor were recorded at temperatures between 252 and 273 K under the pressure of 0.2-30.0 Torr, and then those FR spectra were investigated. The results showed that two parallel adsorption processes exist in ethene/HMor system. Those two processes were attributed to adsorption process of ethene on proton acid sites (low frequency adsorption) and on hydrogen cation sites (high frequency adsorption); meanwhile the number of sites available for adsorption of ethene is 0.692 and 0.828 mmol g⁻¹, respectively. The number of adsorption sites in low frequency is increased by the introduction of CuO which is located among the proton acid sites but covered the hydrogen ion sites in high frequency. Chemical adsorption of ethene is the main sorption process in CuO/HMor. The number of adsorption sites in low frequency is decreased by the introduction of Cs⁺ which counteracted proton acid sites in low frequency. Physical adsorption is the main sorption process in Cs⁺/HMor channels. The optimum content of CuO for modification is 5% (weight/weight). Combining the FR spectra and other methods such as isotherms and Langmuir model, a thorough understanding of the ethene adsorption processes on zeolites can be achieved.     

基于固体核磁共振技术的固体酸结构、酸性及活性分析

固体酸是工业烃转化和生物质精炼中应用最广泛的非均相催化剂之一，了解它们的局部结构和酸性等性质有利于合理设计高效绿色固体酸催化剂，从而提高目标反应的活性和稳定性.近年来，固体核磁共振波谱在定性和定量表征固体酸的局部结构和酸性方面已显示出巨大的应用潜力，甚至可作为一种标准方法.二维固体核磁共振波谱的应用可以进一步揭示固体酸表面位点的结构对称性和不同位点的空间构效关系，从而加深对“催化剂结构-酸性-活性关系”的理解.在这篇综述中，我们总结了用于固体酸表征的固体核磁共振波谱方法和常规实验操作流程，并着重阐述了在使用和不使用探针分子的情况下，固体核磁共振波谱应用于固体酸局部结构和酸性性质研究的进展.     

Further experimental evidences of thermal spreading of tungsten oxide on zirconia

The effects brought about by the time of thermal treatment as well as the water content in the gas phase during the thermal spreading of WO₃ on zirconia were investigated. Diffuse reflectance UV-vis spectroscopy evidenced the thermal spreading phenomenon and revealed the formation of polymeric tungsten dispersed species. Neither the thermal treatment time nor the water content showed to influence the nature of the dispersed species, which reveal to present thermodynamically preferential molecular structures. Infrared spectroscopy analysis of adsorbed pyridine evidenced that the polytungstate species lead to the generation of Brönsted acid sites. Lewis acid sites stronger than those naturally present on zirconia could also be detected in addition to weaker Lewis sites, which were associated to the WO₃ still present in the catalysts as showed by X-ray diffraction.     

改性高岭土的制备、表征及其光催化性能

通过焙烧和H₂SO₄浸渍制备了改性高岭土。利用热重-差热(TG-DTA)、扫描电镜(SEM)结合能谱(EDS)、X射线衍射(XRD)、紫外-可见光吸收光谱(UV-Vis)及BET比表面积测定等手段对所获得样品进行了表征。以甲基橙为模型反应物,评价了样品的光催化活性。同未经酸改性的焙烧高岭土相比,改性高岭土的UV-Vis光谱吸收边带产生明显红移。样品具有更高的光吸收效率,促进了其光催化活性。吡啶吸附红外光谱(Py-IR)分析显示,改性高岭土表面具有酸性。当酸浸过程的H₂SO₄溶液浓度高于30%时,得到的样品同时具有Brnsted和Lewis酸位。光谱分析结果结合光催化评价结果表明,样品的酸性是影响其光催化性能的主要因素。     

杭锦2#土的光谱特征及非均相Fenton反应机理

杭锦2#土是内蒙古鄂尔多斯杭锦旗地区发现的层状含铁天然矿物,利用Ｘ射线衍射、吡啶吸附红外光谱及Ｘ射线光电子能谱技术对样品的性质进行了表征。X射线光电子能谱表明杭锦2#土骨架结构中Si和Al原子结合能与标准硅氧四面体和铝氧八面体中Si和Al结合能相比明显增加,表面存在Lewis酸位和Brönsted酸位,且杭锦2#土中铁物种以Fe(Ⅲ)和Fe(Ⅱ)形式存在于骨架结构中;非均相Fenton反应中杭锦2#土的Fe(Ⅱ)可与H₂O₂反应生成自由基(·OH)与Fe(Ⅲ),但反应速率慢且难以循环。酸活化后杭锦2#土中Si和Al的结合能进一步增加,铁物种部分转变为非结构铁并以Fe3+与Fe2+转移到样品表面;X射线光电子能谱、吡啶红外和氨气程序升温表征表明酸活化杭锦2#土表面Lewis酸位和Brönsted酸位增多;非均相Fenton反应中,酸活化杭锦2#土表面Fe3+与Fe2+可与H₂O₂循环反应,不断生成·OH并对甲基橙进行降解,且活化杭锦2#土表面Brönsted酸能够提供质子将H₂O₂包围,抑制其分解生成HO-₂并提供更多的·OH,Lewis酸能增加杭锦2#土表面吸附氧（O_ad）含量,而Fe2+可被O_ad氧化为Fe3+,促进Fe2+/Fe3+之间的循环,同时在氧化过程中电子转移到O_ad形成O·-₂,O·-₂能够与Brönsted酸提供的质子反应形成·OH,·OH与O·-₂均为氧化性自由基,能够提升活化杭锦2#土非均相Fenton反应活性。此外,X射线衍射表明酸活化使杭锦2#土中CO2-₃转化为对Fenton反应负面影响更小的SO2-₄进而提升其非均相Fenton反应活性。     

Theoretical and experimental investigations on the structures of purified clay and acid-activated clay

The purified and acidified montmorillonite clay were characterized by XRD, BET and TPD. These results show that acidified clay is provided with more surface area and acid sites. For NH₃-TPD, molecular NH₃ desorption on purified clay and acidified clay occurs at temperatures with 873 and 1000 K, respectively. It is shown for the existence for strong acid sites. By two reactions of the tetrahydropyranylation of n-propanol and the esterification of cyclo-2-pentene with acetic acid, it is shown that the acidified clay displays better catalytic activity for above two organic reactions. By density-functional theory (DFT) method, we have analyzed the structures of different substituted montmorillonite and the effect sorption behavior of Na⁺ in different montmorillonite models. The result shows that the process of substitution will occur apart from octahedral aluminums. The adsorption of NH₃ on clay surfaces have been investigated using TPD and DFT. This is shown that acid sites locate at round the octahedral aluminums, and substitution of Al³⁺ for tetrahedral Si will be favorable to NH₃ adsorption.     

SSZ-13分子筛上甲醇转化过程中甲氧基物种的生成与活性研究

本文使用固体核磁共振（NMR）技术研究了SSZ-13分子筛上甲醇制烯烃反应过程中表面甲氧基物种的生成以及反应活性.通过二维¹³C-²⁷Al HMQC NMR方法确证了甲醇在分子筛骨架Brønsted酸位上生成的甲氧基物种,以及在Lewis酸位上生成的另外一种表面甲氧基物种.¹³C NMR结合气相色谱-质谱（GC-MS）实验结果表明,这两种甲氧基物种在甲醇制烯烃反应中均具有较高的反应活性,既可以导致烃池物种的生成,也可以参与烃池反应生成碳氢化合物.     

Probing the evolution of water clusters during hydration of the solid acid catalyst H-ZSM-5

A technique developed recently for in situ solid-state ¹H NMR studies of adsorption processes has been used to probe hydration of the solid acid catalyst H-ZSM-5, yielding information on the interaction between the adsorbed water molecules and Brønsted acid sites on the H-ZSM-5 host material. Quantitative analysis of the results from the in situ experiment allows the average size of water clusters associated with the Brønsted acid sites to be determined directly, and suggests that there is a preference to form clusters comprising five–six water molecules. The in situ ¹H NMR data also provide insights into kinetic aspects of the adsorption process.     

改性VOx/Al2O3催化剂催化氧化甲醇的固体核磁共振研究

采用固体核磁共振研究了NaOH 和HNO₃改性的VO_x/Al₂O₃上甲醇选择性催化氧化反应. 实验结果表明: 在甲醇的氧化反应中, 酸位对二甲氧基甲烷的生成起了重要作用. 与VO_x/Al₂O₃催化剂相比, 酸改性的VO_x/Al₂O₃上的强的Bronsted酸位对二甲氧基甲烷的选择性较高, 没有Bronsted酸位的碱改性的VO_x/Al₂O₃上生成的不是二甲氧基甲烷而是甲酸盐.     

Effect of nano clay platelets and DNA on controlling the H-dimer of oxazine 4 perchlorate (OX4) in LbL film

Oxazine 4 perchlorate (OX4) forms dimer even in aqueous solution. In layer-by-layer (LbL) film of OX4, dimeric sites predominate over monomeric sites. This results in the quenching of fluorescence intensity. This communication reports a study of the control of H-dimer of OX4 in LbL film by incorporating nano clay platelets. Influence of deoxyribonucleic acid molecules in controlling the H-dimeric sites of Ox4 in the LbL film has also been studied. UV–Vis absorption spectroscopic technique has been employed to study this effect. Atomic force microscopic image confirms the presence of nano clay platelets in the LbL film.