Ni-Fe-B/MCM-41非晶态合金的合成与表征

用化学还原沉积法制备了Ni-Fe-B／MCM-41负载型非品态合金催化材料。通过XRD,FT-IR,TPR,SEM,TG及BET研究了非晶态合金对介孔分子筛载体结构的影响及非晶态合金负载后性质和形态的变化。结果表明：非晶态合金没有破坏介孔分子筛的结构,Ni-Fe-B／MCM-41的热稳定性和氧化能力与Ni-Fe-B相比,均有一定提高。     

Metastability of MCM-41 and Al-MCM-41

The apparent stability of MCM-41 and Al-MCM-41 in water was appraised in a series of solubility experiments. MCM-41 is a siliceous, mesoporous material of hexagonal symmetry and exceptionally high surface area first synthesized in 1992. The dissolution experiments were carried out at several solid/water ratios: 1/200, 1/100, and 1/75. Results indicated that MCM-41 and Al-MCM-41 are more soluble than amorphous silica at ambient temperatures. Using standard thermodynamic data, a minimum Gibbs free energy of formation of -847.9 kJ/mol for MCM-41 was calculated compared to -848.85 kJ/mol for amorphous silica and -856.3 kJ/mol for quartz. X-ray diffraction (XRD) analyses of recovered solids indicated a progressive loss of crystallinity in MCM-41 and Al-MCM-41 over the 79 day dissolution experiment. BET nitrogen surface area analyses of recovered solids revealed no appreciable change in the surface area of either material after 79 days of reaction in water. Field emission scanning electron microscope (SEM) images taken of the 79 day MCM-41 sample showed some degradation of the initial structure-fine, worm-like particles.     

辅助有机胺对介孔分子筛MCM-41合成及其性质的影响

采用阳离子表面活性剂十六烷基三甲基溴化铵为模板剂、硫酸铝为铝源、硅溶胶为硅源，分别使用中等链长的有机胺和正己烷作为辅助添加剂，用水热晶化法在碱性介质中合成了介孔分子筛MCM-41，通过XRD、N2吸附-脱附、SEM测试手段对得到的样品进行了对比表征分析。实验结果表明，除三乙胺外，向反应体系中加入适量的三正丙胺、三正丁基胺、三正辛胺和二异丁胺后，均能够使介孔 MCM-41的d100值和孔径增大，且具有较大的BET表面积（>1 000 m2/g）和孔容（>1 cm3/g）；加入正己烷后，也可以使得MCM-41孔径变大，但是和加入有机胺相比较，合成的样品具有较小的BET表面积（887.3 m2/g）和孔容（0.81 cm3/g）。     

Capillary condensation in mesoporous silica with surface roughness

We construct an atomistic silica pore model mimicking templated mesoporous silica MCM-41, which has molecular-level surface roughness, with the aid of the electron density profile (EDP) of MCM-41 obtained from X-ray diffraction data. Then, we present the GCMC simulations of argon adsorption on our atomistic silica pore models for two different MCM-41 samples at 75, 80, and 87 K, and the results are compared with the experimental adsorption data. We demonstrate that accurate molecular modeling of the pore structure of MCM-41 by using the experimental EDP allows the prediction of experimental capillary evaporation pressures at all investigated temperatures. The experimental desorption branches of the two MCM-41 samples are in good agreement with equilibrium vapor–liquid transition pressures from the simulations, which suggests that the experimental desorption branch for the open-ended cylindrical pores is in thermodynamic equilibrium.     

以离子液体为结构导向剂合成有序超微孔二氧化硅

在酸性条件下, 以1-十六烷基-3-甲基溴化咪唑为表面活性剂合成了具有有序超微孔结构的二氧化硅材料, 所合成的材料具有较高的比表面积和二维六方有序的孔结构, 样品的孔径尺寸为1.8 nm.     

中孔硅酸盐材料MCM-41的合成与表征研究(英文)

以十六烷基三甲基溴化铵为模板剂,硅酸钠为硅源,铝酸钠为铝源,在水热条件下成功地合成出了ＭＣＭ－４１中孔硅酸盐材料。采用ＸＲＤ、低温Ｎ２吸附脱附等测试手段对合成的ＭＣＭ－４１样品进行了表征。通过优化合成条件,合成出孔径３.２ ｎｍ、比表面９０４ｍ２／ｇ和孔壁厚约１.４６ ｎｍ的ＭＣＭ－４１分子筛。催化活性测定采用微反应活性实验来评价其活性和选择性。     

PtSn/Al2O3/MCM-41催化剂的丙烷脱氢催化性能

用微型催化反应装置评价, 并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3, PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能. 发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性. 实验结果表明, 纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原, 导致铂金属分散度和催化剂的丙烷脱氢活性较低. 用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用, 提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性. 并且, 积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度, 故具有较高的丙烷脱氢反应稳定性. PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能可能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关, 而且与Al2O3/MCM-41载体的介孔结构有关.     

杂原子介孔Co-MCM-41分子筛的制备及其吸附脱氮性能

采用水热法合成了介孔MCM-41和Co-MCM-41分子筛,并利用XRD、FT-IR、低温N₂吸附-脱附和NH₃-TPD等方法对合成的分子筛进行了表征。考察了晶化时间、晶化温度、陈化时间对合成介孔Co-MCM-41分子筛的影响,确定较适宜的合成条件为陈化时间1 h,晶化温度110 ℃,晶化时间2 d。XRD 和FT-IR表征结果说明,Co原子已经进入MCM-41的骨架。MCM-41和Co-MCM-41的平均孔径均为2.82 nm,BET比表面积分别为986.42和 637.69 m²/g,孔容分别为0.762 1和0.537 2 m³/g。NH₃-TPD的表征结果表明,MCM-41和Co-MCM-41的酸性都较弱,但Co-MCM-41的酸性明显强于MCM-41。在此基础上,利用合成的MCM-41和Co-MCM-41吸附脱除氮含量为1 737.35 μg/g的模拟燃料中的喹啉。喹啉分子尺寸的模拟结果为0.711 6 nm × 0.500 2 nm,说明其可以很容易地进入MCM-41和Co-MCM-41的介孔孔道中。Co-MCM-41分子筛的氮脱除率明显高于MCM-41,这是由于其较强的酸性及与喹啉之间的化学吸附,而且,Co-MCM-41吸附脱氮具有较好的再生性能。     

AlMCM-41介孔分子筛的合成及表征

以拟薄水铝石为铝源、水玻璃为硅源、十六烷基三甲基溴化铵为模板剂,在110℃时水热晶化合成了含Al的MCM-41介孔分子筛.采用X射线衍射(XRD)、N2吸附-脱附、固体29Si、27Al魔角旋转核磁共振技术(MASNMR)、扫描电镜(SEM)及吡啶吸附傅里叶变换红外(FTIR)光谱技术对AlMCM-41分子筛进行了表征.结果表明:AlMCM-41分子筛具有六方排列的孔道结构,同时具有很高的相对结晶度、比表面积和孔容,且孔分布单一;AlMCM-41分子筛中Si原子在骨架内键合的程度更高,使AlMCM-41分子筛具有更好的骨架晶化程度;同时具有四配位骨架铝,使AlMCM-41介孔分子筛具有适当的酸性.     

Density functional theory model of adsorption on amorphous and microporous silica materials

We present a novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity. Within QSDFT, solid atoms are considered as quenched component(s) of the solid-fluid system with given density distribution(s). Solid-fluid intermolecular interactions are split into hard-sphere repulsive and mean-field attractive parts. The former are treated with the multicomponent fundamental measure density functional. Capabilities of QSDFT are demonstrated by drawing on the example of adsorption on amorphous silica materials. We show that, using established intermolecular potentials and a realistic model for silica surfaces, QSDFT quantitatively describes adsorption/desorption isotherms of Ar and Kr on reference MCM-41, SBA-15, and LiChrosphere materials in a wide range of relative pressures. QSDFT offers a systematic approach to the practical problems of characterization of microporous, mesoporous, and amorphous silica materials, including an assessment of microporosity, surface roughness, and adsorption deformation. Predictions for the pore diameter and the extent of pore surface roughness in MCM-41 and SBA-15 materials are in very good agreement with recent X-ray diffraction studies.     

MCM-41分子筛担载纳米TiO2复合材料光催化降解罗丹明B

采用溶胶-凝胶法将TiO2担载在介孔MCM-41分子筛上, 制备了不同TiO2含量的系列TiO2/MCM-41复合材料, 利用X射线衍射、N2吸附、紫外-可见光谱和透射电镜等方法对其进行表征. TiO2的晶型为锐钛矿相, 复合材料的比表面积和孔体积随其中TiO2担载量(复合材料中TiO2与MCM-41的质量比)的增加而减小, TiO2的平均粒径随其担载量的增加而增大. 以罗丹明B的光催化降解为探针反应, 评价了TiO2/MCM-41复合材料的光催化降解活性. 结果表明, 在紫外光照射下, 罗丹明B在该复合材料上的光催化降解反应遵循一级反应动力学, 复合材料对罗丹明B的光催化降解活性明显高于商用TiO2 (P-25), 复合材料的光催化降解活性由复合材料的吸附能力和所含TiO2的光催化活性共同决定.     

Influence of cross profile of PE fibers on thermal properties of materials

Molecular sieves MCM-41 were synthesized from rice husk ash (RHA) as alternative sources of silica, called RHA MCM-41. The material was synthesized by a hydrothermal method from a gel with the molar composition 1.00 CTMABr:4.00 SiO₂:1.00 Na₂O:200.00 H₂O at 100 °C for 120 h with pH correction. The cetyltrimethylammonium bromide (CTMABr) was used as a structure template. The material was characterized by X-ray powder diffraction, FTIR, TG/DTG, and surface area determination by the BET method. The kinetics models proposed by Ozawa, Flynn–Wall, and Vyazovkin were used to determine the apparent activation energy for CTMA⁺ species decomposition from the pores of MCM-41 material. The results were compared with those obtained from the MCM-41 synthesized with silica gel. The synthesized material had specific surface area, size, and pore volume as specified by mesoporous materials developed from conventional sources of silica.     

Physico-chemical characterization of MCM-41 silica spheres made by the pseudomorphic route and grafted with octadecyl chains

This work reports on the first comprehensive characterization of octadecyl (C(18)) modified MCM-41 silica spheres, prepared via the pseudomorphic route, followed by grafting with mono- or trifunctional octadecyl (C(18)) alkyl chains and endcapping with hexamethyldisilazane. Small angle X-ray scattering (SAXS), nitrogen adsorption-desorption and scanning electron microscopy (SEM) measurements were performed to obtain information about the MCM-41 pore structure, surface properties and morphological features. The degree of grafting and cross-linking of the silanes were determined by (29)Si magic angle spinning NMR spectroscopy, while FTIR and (13)C NMR were employed to study the conformational behavior of the surface-immobilized alkyl chains. The SAXS pattern proved the existence of a hexagonal mesopore arrangement for both the ungrafted and the grafted MCM-41 silica spheres. In addition, there is evidence of some long-range distortion in the pore structure. SEM measurements revealed the same morphological features for the parent silica and the MCM-41 silica spheres before and after C(18) grafting. The achieved surface loading for the MCM-41 material is rather low. It was also shown that a substantial amount of the accessible surface silanol groups is endcapped by trimethylsilane which in turn results in a very low surface coverage due to the octadecyl chains. The nitrogen sorption studies provided values for the surface area, total pore volume and pore diameter which are very typical for mesoporous materials. The reduction in surface area and total pore volume upon surface grafting is related to the binding of trimethylsilane in the interior of the pores, while due to the spatial restrictions octadecyl chains are primarily attached near the pore entrance. The experimental FTIR and (13)C NMR data point to a very low conformational order of the C(18) chains which is in accordance with the observed low surface coverage and the resulting spatial freedom for these surface-immobilized alkyl chains.     

苄基磺酸接枝MCM-41介孔分子筛的合成与表征

在采用溶胶-凝胶法合成纯硅MCM-41基础上，经过两步后合成处理，在纯硅MCM-41上接枝苄基磺酸，并通过X射线衍射、低温氮气吸附、红外光谱、元素分析、热重分析和酸度滴定，对所得样品进行了表征。结果表明，经过苯甲醇、氯磺酸两步接枝处理，苄基及磺酸成功地接入MCM-41上，并保持MCM-41的介孔结构，接枝后的磺酸型MCM-41比表面积和孔容均减小，分别为 976 m²·g^-1和0.42 cm³·g^-1，酸量为4.2 mmol·g^-1。     

Nitrogen adsorption on silica surfaces of nonporous and mesoporous materials

We present an accurate comparative analysis of N 2 adsorption at 77 K on nonporous silica and the pore wall surface of MCM-41 materials. The analysis shows that in the low-pressure region of N 2 adsorption obeys a peculiar mechanism governed by short-ranged forces, which makes the surface curvature effect on the N 2 adsorption in mesopores nearly negligible. We used this observation to define more exactly compared to the BET technique the specific surface area of the reference adsorption isotherm on nonporous silica basing on XRD data and linear sections of t-plots. Calculation of the capillary evaporation and condensation pressures seems to confirm our previous finding that the capillary condensation pressure corresponds to the equilibrium transition rather than spinodal condensation at least for pore sizes less than 7 nm. It allowed us to provide more reliable pore size distribution (PSD) analysis of mesoporous silica materials. For example, the PSDs of MCM-41 samples do not show artificial peaks in the micropore range that we obtained in our earlier publications.     

中孔沸石新材料MCM－41──Ⅰ．合成、酸性及稳定性

中孔沸石新材料ＭＣＭ－４１──Ⅰ．合成、酸性及稳定性赵修松，王清遐，徐龙伢，谢紊娟（中国科学院大连化学物理研究所，大连１１６０２３）李新生（中国科学院大连化学物理研究所催化基础国家重点实验室，大连１１６０２３）关键词ＭＣＭ－４１沸石，合成，酸性，稳定...     

YOx -MCM-41介孔分子筛的合成与表征

以十六烷基三甲基溴化铵为模板剂,偏硅酸钠为硅源,硝酸钇为钇源,用水热法合成了YOx-MCM-41介孔分子筛,经X射线粉末衍射法,FT-IR,热重分析,紫外漫反射法及N2吸附-脱附法表征。结果表明,该分子筛具有热稳定性好、比表面积大、孔道均一等典型的MCM-41介孔分子筛的特征。     

The Synthesis and Characteristics of Vanadoaluminosilicate MCM-41 Mesoporous Molecular Sieves

A series of vanadoaluminosilicate MCM-41 mesoporous molecular sieves with various compositions have been hydrothermally synthesized. Hexadecyltrimethylammonium bromide was used as a surfactant in the synthesis. The samples were characterized with nitrogen sorption, X-ray diffraction, differential thermal analysis, thermogravimetric analysis, Fourier transform-Infrared spectroscopy, UV-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, and solid state NMR. The solid products had the MCM-41 structure and contained only atomically dispersed vanadium and aluminum consistent with framework vanadium and aluminum. The samples were hydrophobic and contained large amount of surfactant in the as-synthesized samples. The surfactant could be removed upon calcination at 450°C. N₂ sorption measurements and TEM demonstrate the high mesoporosity of [V, Al]-MCM-41. The incorporation of vanadium and aluminum into MCM-41 decreased the surface area to some extent. The morphologies of all the samples were the agglomerate of plates. ²⁹Si MAS NMR shows that the pore wall is amorphous. ²⁷Al MAS NMR shows that all of aluminum species were tetrahedrally coordinated even after calcination at 550°C.     

Nanoporous carbons as promising novel methane adsorbents for natural gas technology

Nanoporous carbons were synthesized using furfuryl alcohol and sucrose as precursors and MCM-41 and mordenite as nanoporous templates.The produced nanoporous carbons were used as adsorbent for methane storage.The average pore diameter of the samples varied from 3.9 nm to 5.9 nm and the BET surface area varied from 320m2/g to 824m2/g.The volumetric adsorption experiments revealed that MCM-41 and sucrose had better performance compared with mordenite and furfuryl alcohol,correspondingly.Also,the effect of precursor to template ratio on the structure of nanoporous carbons and their adsorption capacities was investigated.The nanoporous carbon produced from MCM-41 mesoporous molecular sieve partially filled by sucrose shows the best methane adsorption capacity among the tested samples.     

共缩聚法制备有序介孔氧化硅纳米螺旋纤维

在传统球状介孔氧化硅合成工作的基础上,以正硅酸乙(TEOS)和γ-巯丙基三甲氧基硅烷(MPTMS)为硅源,在水体系下利用共缩聚法一步合成出具有介孔分子筛结构特征的纳米纤维,并通过扫描电子显微镜(SEM)、小角X射线衍(XRD)、透射电子显微镜(TEM)和氮气吸附-脱附实验对样品进行了表征与分析.