有机物单层分散在相关材料制备中的应用

与无机氧化物和盐类在载体表面自发单层分散相类似, 许多有机物也可以在载体表面自发单层分散.有机物在载体表面单层分散行为和分散后的存在状态与有机物分子形状和结构特点及载体表面性质和孔结构有关. 利用有机物在载体表面的单层分散, 可以设计制备具有优异性能的材料. 本文简要综述了近年来这方面研究工作取得的相关进展, 主要介绍了有机物单层分散在碳/氧化物复合物、氧化物和薄壁中孔碳材料的制备和织构调控方面的一些应用实例. 单层分散的有机物热分解后可在载体表面形成均匀的薄碳层, 以无机多孔氧化物为载体可制备出包覆均匀碳薄层的碳/氧化物复合物, 这种碳/氧化物复合物在染料吸附、催化剂载体和光催化方面显现出好的性能. 以溶胶-凝胶法制备氧化物时, 分散的有机物可以隔离溶胶颗粒, 从而制备出高比表面积的氧化物并可对孔容进行调控, 以此方法制备的γ-氧化铝比表面积可达506 m²·g^-1. 在惰性气氛中加热上述碳/氧化物复合物, 碳层可抑制氧化物的相变; 而在氧气中, 碳层燃烧发热会促进相变, 由此可快速制备超细α-氧化铝. 包覆均匀碳薄层的氧化物载体对碳起支撑作用, 在将氧化物溶解去除后, 可便捷制得高比表面积、大孔容、高中孔率的薄壁中孔碳材料, 碳材料的形貌、孔径分布等可通过选用不同织构的氧化物载体进行调控.     

某些有机物在氧化物载体表面的自发单层分散

自发单层分散原理已在载负型催化剂制备、再生等方面得到越来越广泛的应用[1，2]．许多氧化物和盐类可以在载体表面形成单层分散或亚单层分散．有些分散物与载体混合后在低于其熔点的温度下处理，就可以自发分散到载体表面[1，3]．这一现象通过XRD、LRS、XPS、SIMS、ISS、EXAFS     

单层分散阈值和负载型催化剂的阈值效应

自发单层分散原理认为,许多负载型催化剂的活性组分可在载体表面自发分散。活性组分在载体表面的单层分散阈值可通过XRD相定量外推法等实验方法进行测定。通过单层分散阈值的测定可获取负载型催化剂表面结构、分散状态的有益信息,并为选择最佳的催化剂制备工艺条件提供依据。许多负载型催化剂活性组分的配比都可通过考察其单层分散阈值得以优化。负载型催化剂的许多物理化学性质突变值都与其单层分散阈值相联系,催化剂的阈值效应是明显的,阈值效应的提出为催化剂的研究提供了指导。     

盐类和氧化物在载体上自发单层分散研究新进展

 盐类和氧化物在载体上自发单层分散的现象和原理自被发现以来在国内外得到了广泛认同，国内外这方面的工作越来越多．我们从国内外同行近年发表的上百篇有关论文中，选择一部分内容加上我们的部分工作做一个简单的综述，介绍有关自发单层分散原理在基础研究和应用两个方面的新进展．     

MoO3在Al2O3薄膜表面扩散的研究

氧化物和盐类在高比表面载体上的单层分散现象已被大量实验所证实［１］．ＭｏＯ_３在γ－Ａｌ_２Ｏ_３等高比表面载体上的分散已经研究很多,近来的研究证实ＭｏＯ３等在α－Ａｌ２Ｏ３等小比表面载体上也能自发单层分散［２］,但是分散的过程仍然缺乏直接的观察研究．本工作通过多种表面分析方法首次研究了ＭｏＯ３在平整无定形的Ａｌ２Ｏ３薄膜上的扩散过程以及影响因素．发现除温度升高外、水汽的存在对该扩散过程也有促进作用．１实验部分１．１样品的制备采用ＳＳ－３２００真空磁控溅射镀膜机,通入Ａｒ－Ｏ２作为反应气,直流磁控…     

分子工程学

分子工程学以体系的功能为导向,在分子水平上进行结构设计与施工,探索功能、结构与合成三者之间的关系原理,发展合成、制备与组装方法学,研究结构基元本征性质和构效关系。本文讨论了建设分子工程学这一新学科的重要性,介绍了自发单层分散原理与CO吸附剂、纳米结构光电功能体系、金属纳米簇基催化剂、表面分子多孔网络的精确可控组装以及功...     

冀以萤烛末光增辉日月——庆祝物理化学家谢有畅先生九十华诞

<正>2023年，欣逢我国著名物理化学家、北京大学化学与分子工程学院教授谢有畅先生九十华诞。上世纪80年代前后，谢有畅先生在实验中发现自发单层分散现象，总结出自发单层分散原理，随后展开研究，发表数十篇相关论文。1990年应邀在Advances in Catalysis杂志上发表单层分散总结性论文，单篇被引用800多次。该项基础研究成果获1986年国家教委科技进步一等奖。     

一氧化碳高效吸附剂CuCl／分子筛

利用自发单层分散原理，将ＣｕＣｌ分散在载体表面制备高效的ＣＯ吸附剂，将ＣｕＣｌ与γ－Ａｌ２Ｏ３，４Ａ，１３Ｘ，ＮａＹ，ＣｕＹ分子筛等高比表在载体混合，在３５０℃焙烧数小时，ＸＲＤ和ＥＸＡＦＳ研究证明ＣｕＣｌ可在载体表面达到原子水平的分散由于Ｃｕ＾＋可与ＣＯ生成配位键。由此可制得对ＣＯ有高吸附容量和选择性的吸附剂，其中ＣｕＣｌ／ＮａＹ和ＣｕＣｌ／Ｃｕ＾＋Ｙ吸附剂的吸附容量在２０℃，ＣＯ分压为６０ｋＰ     

有机酸在γ-Al2O3表面自发单层分散及苯甲酸-γ-Al2O3表面结构的研究

有机酸如苯甲酸,水杨酸,邻-或对-苯二甲酸,酒石酸均可在γ-Al~2O~3表面自发单层分散,分散的临界温度取决于有机酸分子中极性基团的数目和极性的强弱。XRD,Raman,FT-IR,UV-vis和TG对苯甲酸-γ-Al~2O~3体系的表征结果表明,苯甲酸在室温下即可在γ-Al~2O~3表面自发单层分散;分散后,苯甲酸分子间的氢键缔合结构垮塌;苯甲酸的羧基与γ-Al~2O~3表面羟基发生相互作用并缩水形成类似羧酸盐的结构;分子中的苯环与载体表面没有直接的相互作用。XRD相定量测得的分散阈值为1.1mmol苯甲酸/100m^2γ-Al~2O~3,与按苯环垂直表面计算所得的最大分散容量1.2mmol/100m^2相近。     

新型环状六烷基胍盐室温离子液体的合成及相转移催化性质研究

离子液体是由一个大的有机阳离子和一个较小的无机或有机阴离子组成的在室温或近于室温下呈液态的熔盐体系.它对大部发有机物和部分无机物具有很好的溶解性能、无毒没有蒸气压、处于液体范围广、可以调节阳离子和负离子的结构来调节离子液体的各项性质、可重复利用等性能.近几年来,由于其独特的性质得到了世界各国化学工作者的广泛关注[1].     

Physicochemical characterization of the retardation of aqueous Cs+ ions by natural kaolinite and clinoptilolite minerals

The aim of this study was to carry out kinetic, thermodynamic, and surface characterization of the sorption of Cs+ ions on natural minerals of kaolinite and clinoptilolite. The results showed that sorption followed pseudo-second-order kinetics. The activation energies were 9.5 and 13.9 kJ/mol for Cs+ sorption on kaolinite and clinoptilolite, respectively. Experiments performed at four different initial concentrations of the ion revealed that the percentage sorption of Cs+ on clinoptilolite ranged from 90 to 95, compared to 28 to 40 for the kaolinite case. At the end of a 1 week period, the percentage of Cs+ desorption from clinoptilolite did not exceed 7%, while it amounted to more than 30% in kaolinite, indicating more stable fixation by clinoptilolite. The sorption data were best described using Freundlich and D-R isotherm models. Sorption showed spontaneous and exothermic behavior on both minerals, with deltaH(0) being -6.3 and -11.4 kJ/mol for Cs+ uptake by kaolinite and clinoptilolite, respectively. Expanding the kaolinite interlayer space from 0.71 to 1.12 nm using DMSO intercalation, did not yield a significant enhancement in the sorption capacity of kaolinite, indicating that the surface and edge sites of the clay are more energetically favored. EDS mapping and elemental analysis of the surface of kaolinite and clinoptilolite revealed more intense signals on the surface of the latter with an even distribution of sorbed Cs+ onto the surfaces of both minerals.     

Equilibrium,kinetic, and thermodynamic studies of lead ion adsorption from mine wastewater onto MoS2-clinoptilolite composite

This work explored the potential of clinoptilolite, molybdenum sulphide (MoS₂), and MoS₂-clinoptilolite composite in lead (Pb) removal from aqueous medium and industrial mining wastewater. MoS₂-clinoptilolite composite was successfully prepared by a hydrothermal method. The surface properties, structure, and composition of the synthesized composite and the parent compounds were analyzed by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The removal efficiency of lead from aqueous solution was studied in batch-mode experiments. The MoS₂-clinoptilolite was used for the removal of Pb ions (50 mg/L) from an aqueous solution: ~100% of the Pb was removed with a MoS₂-clinoptilolite dose of 0.075 g, pH 6 at 328K within 90 min. The adsorption capacities of Pb onto MoS₂-clinoptilolite were found to be higher than those onto clinoptilolite. Metal ion adsorption behavior was well explained by the Freundlich model, that is, multilayer adsorption of Pb molecules occurred on the heterogeneous surface of adsorbents in case of clinoptilolite, while in the case of MoS₂-clinoptilolite, the Langmuir model was suitable, that is, the adsorption occurred on a monolayer surface. The rate of Pb adsorption was explained by pseudo-second-order model suggesting that the adsorption process is presumably chemisorption. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° were calculated, which indicated that the adsorption was spontaneous and exothermic in nature. The selectivity of each adsorbent for Pb was also tested by adding the adsorbents to real gold mine water which contains competitive metal ions.     

Ammonium sorption from aqueous solutions by the natural zeolite Transcarpathian clinoptilolite studied under dynamic conditions

The scope of this study is ammonium-ion uptake from synthetic aqueous solutions onto raw and pretreated forms of the natural zeolite Transcarpathian clinoptilolite under dynamic conditions. Hydrogen ions displaced exchangeable cations on the clinoptilolite in distilled water (sodium ions) and hydrochloric acid (sodium, potassium, and calcium ions) and destroyed the zeolite framework structure in the last case. Ammonium uptake onto the zeolite occurs by exchange with Na(+), Ca(2+), and K(+) ions. Although Na(+) ions were observed to be more easily exchanged for both hydrogen and ammonium ions, the role of Ca(2+) ions increased with zeolite saturation by NH(+)(4) ions. The maximum sorption capacity of the clinoptilolite toward NH(+)(4) ions, estimated under dynamic conditions, is significantly higher than that measured under static conditions; proximity of the values of a distribution coefficient and a retardation factor for different conditions (215-265 dm(3)/kg and 979-1107, respectively) allows us to use these parameters to model ammonium uptake onto the clinoptilolite. Slowing down or interruption in filtration resulted in the improvement of ammonium sorption properties of the zeolite. The ammonium removal improves with use of the finer fractions of the clinoptilolite up to 0.35 mm. A recycling study results confirmed the importance of external diffusion for ammonium sorption by the clinoptilolite. Preliminary treatment of the sorbent confirmed the predominant importance of the ion-exchange mechanism. The advantage of prior NaCl treatment of the clinoptilolite in improvement of ammonium removal over the other techniques was shown.     

Study of adsorption phenomena ongoing onto clinoptilolite with the immobilized interfaces

The development of innovative clean-up technologies remains a challenge as current procedures have many limitations, such as being expensive, concentration or pollutant specific, and many others. Natural zeolite of clinoptilolite type was beneficiated with surfactant octadecylammonium and alginate biopolymers using the sol-gel method. Carbonization process in pyrolysis chamber combusted organic waste materials and reaching the maximum temperature of 700°C was used for the surface carbonization, respectively. Resulted zeolite based products were analyzed by FTIR, TG, DTA and examined on the selected aqueous pollutants removal using the conventional laboratory adsorption experiments. The ability of ODA and alginate linked zeolite of clinoptilolite type to form complexes with anions (such as nitrate, sulphate, chloride and phosphate) and to remove them from contaminated waters was validated. Carbon deposition onto clinoptilolite surface originated from the pyrolytic carbon-rich waste combustion simulated the new zeolite based hybrid to active coke, adsorption efficiency of which towards phenol was approved. Thermogravimetric analyses of the advanced zeolite-based adsorbents were accomplished to find out how temperature resistant are the novel zeolite based materials in respect to the original, untreated one. While the native clinoptilolite indicated according to DTA analysis one broad endothermic response around 100–130°C, resulted from the loss of adsorbed water, by the ODA-modified clinoptilolite was except this DTA peak, the broad exothermic response started from 370 up to 560°C observed. This DTA profile is assumed to record a slowly breakdown of attached ODA surfactant and sequential loss of mass due to continual heating of sample under elevated temperature.     

Distribution threshold values of CaCl<Subscript>2</Subscript> onto the 10X-zeolite and macro-pore silica gel

The calcium chloride used for adsorption separation of ammonia is promising for its large adsorptive capacity and lower desorption temperature, but difficult to develop because of the liable expansion, lump and chip in the adsorption/desorption process. Composite adsorbents made by monolayer dispersion of calcium chloride onto carriers with high surface areas exhibit better adsorptive capacity and stability. Several models were developed to confirm the maximum monolayer dispersion capacity of calcium chloride onto the carriers (the distribution threshold value), and the closely packed monolayer dispersion model was considered the most suitable for this study. The distribution threshold values given by this model were 0.60 g CaCl₂/(g 10X-zeolite) and 0.38 g CaCl₂/(g SiO₂). When the divalent salt was dispersed onto the carriers, however, anions were separated into two types, causing that the entropy of the system tended to increase and the system was not stable. To minimize the entropy, a new model was put forward as the modified closely packed monolayer dispersion model. Based on this model, the distribution threshold values are 0.52 g CaCl₂/(g 10X-zeolite) and 0.33 g CaCl₂/(g SiO₂), respectively. The distribution threshold values were also gained experimentally by XRD quantitative phase analysis: 0.61 g CaCl₂/(g 10X-zeolite) and 0.31 g CaCl₂/(g SiO₂). Comparison between experimental values of distribution threshold with theoretical ones based on two different model showed that the closely packed monolayer dispersion model fits the monolayer dispersion of calcium chloride onto micro-pore carrier —10X-zeolite, and the modified closely packed monolayer dispersion model is more suitable for the bigger aperture carrier —macro-pore silica gel. Supported by the National Natural Science Foundation of China (Grant No. 20576080)     

Iodide adsorption on the surface of chemically pretreated clinoptilolite

The possibility to use the monoionic Ag⁺-form (eventually Hg⁺- and Hg²⁺- forms) of clinoptilolite of domestic origin for radioactive iodide elimination from waters has been studied. The capacity of the monoforms of clinoptilolite towards iodide exceeds many times that of the capacity of clinoptilolite in natural form. Due to the low solubility product of AgI, Hg₂I₂ and HgI₂ iodides generate precipitates on the zeolite surface. Rtg analyses of the silver form of clinoptilolite after sorption of iodide demonstrate the formation of new crystals on the zeolite surface. The influence of interfering anions on the adsorption capacity of silver clinoptilolite towards iodide was investigated, too. Kinetic curves of iodide desorption from the surface of silver and mercury clinoptilolite were compared. Simultaneously, adsorption isotherms for the systems aqueous iodide solution/Ag^–, Hg-clinoptilolite were determined.     

尿素在ZnO(1010)表面的吸附

运用VASP(Vienna ab-initio simulation package),采用基于密度泛函理论(DFT)的第一原理计算,研究了尿素在ZnO(101軈0)表面的吸附行为.计算结果表明:尿素分子在ZnO(101軈0)表面主要发生分子吸附,稳定的吸附产物通过尿素分子中的氮原子或氧原子与表面锌原子之间的键合作用而形成,吸附能分别为-1.48和-1.41eV;表面吸附的尿素分子也可以发生解离,生成表面吸附的异氰酸根、氨气和一个表面羟基,吸附能为-1.66eV.     

MoO3负载在新型TiO2/γ-Al2O3载体上的表面状态与性质

MoO_3担载在TiO_2或γ-Al_2O_3载体上是一类重要的工业催比剂, 其表面状态和表面性质国内外已有过许多报导, 本文报导~[1-5], MoO_3负载在我们所研制的新型TiO_2/γ-Al_2O_3载体(指以γ-Al_2O_3为骨架, 表面上铺以TiO_2物种的载体)上的表面状态与性质。     

Influence of Basic Red 1 dye adsorption on thermal stability of Na-clinoptilolite and Na-bentonite

Influence of physically adsorbed basic red 1 (BR1) dye on the physicochemical properties of natural zeolite (clinoptilolite) and clay (bentonite) was compared using adsorption, FTIR, and TG/DTA methods. A larger adsorption of the dye was observed for bentonite (0.143 mmol/g) than for clinoptilolite (0.0614 mmol/g) per gram of an adsorbent. However, the adsorption values are the same per surface unit (1.8 μmol/m²). The result (per gram) is due to location of dye molecules in interlayer and interparticle space of bentonite with much larger specific surface area than that of clinoptilolite. The dye adsorption leads to a decrease in the specific surface area and the pore volume of both minerals. The adsorption changes also a character of active sites and thermal stability. A TG study shows that the dye adsorption on bentonite changes adsorbed water amounts, weight loss, and decomposition temperature. In the case of zeolite, the dye adsorption insignificantly influences the thermal stability. The dehydration energy distributions calculated from the Q-TG and Q-DTG data demonstrate a complex mechanism of water thermodesorption and the influence of adsorbed dye on this process.     

MoO3和CuCl在γ-Al2O3表面分散速度和分散机理的研究

It has been shown that many oxides and salts can disperse spontaneously onto supports with large surface area~[1]. A typical example studied widely is the dispersion of MoO_3 on γ-Al_2O_3. However, the research work about the dispersion mechanism and kinetics is quite few.Knozinger etc.~[2] suggested that the dispersion of MoO_3 onto the surface of γ-Al_2O_3 may occur through a "gas phase transport" mechanism mainly by assuming an intermediate MoO_2(OH)_2(g), and the presence of water is necessary. Their conclusion was based on a fact that after heating a mixture of MoO_3 and γ-Al_2O_3 in the presence of H_2O vapour at 450 ℃, the characteristic peak at 950 cm~(-1) of monolayer dispersed MoO_3 in Laser Raman Spectrum (in situ) appears, but after heating the mixture in dry oxygen, it can not be observed...