HMCM-22/MCM-41的制备及其在甲苯碳酸二甲酯烷基化中的催化性能

以自制的HMCM-22作为原料,与中孔分子筛MCM-41的凝胶在水热条件下进行组装得到HMCM-22/MCM-41中微孔复合分子筛,采用XRD、N2吸附-脱附及NH3-TPD等方法对合成样品进行表征。结果表明,合成的样品同时具有中孔分子筛MCM-41与微孔分子筛HMCM-22的特点。采用固定床微型连续流反应器对HMCM-22/MCM-41复合分子筛催化甲苯与碳酸二甲酯(DMC)的烷基化反应性能进行了评价,考察了反应温度、甲苯与DMC摩尔配比及空速对烷基化反应的影响。实验发现,HMCM-22/MCM-41催化甲苯DMC烷基化反应的产物中,对二甲苯的选择性远高于间位和邻位异构体的选择性,表现出良好的催化活性和选择性。     

Characterisation and catalytic properties of MCM-41 and Pd/MCM-41 materials

Pure silica MCM-41 mesoporous molecular sieve material was synthesised and characterised by in situ synchrotron XRD, TEM, TGA/DTA and DRIFTS techniques. In situ energy dispersive XRD (EDXRD) confirmed the exact nature of the pore diameter of MCM-41 and the change in crystal structure on calcination. The IR band at 1057 cm^-1 of as-synthesised MCM-41 was shifted by 14 cm^-1 on heating to 673 K due to increased condensation of silanol groups to form Si-O-Si bridges. Calcined MCM-41 materials were used to support Pd, and the catalytic activities for 1-hexene and benzene selective hydrogenation were investigated. The Pd/MCM-41 catalyst showed high activity in hydrogenation of 1-hexene at an inlet reaction temperature of 298 K, but did not show any activity in hydrogenation for benzene. TEM results for the reduced Pd/MCM-41 catalysts revealed that the average Pd particle size was around 2-2.5 nm and these particles were located in the pores of MCM-41 and showed good distribution. TPR measurements showed that about 70% of palladium oxide (PdO) loading in the calcined catalysts was reduced at sub-ambient temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

ZSM-5/MCM-41复合分子筛的微波合成及催化性能

用微孔沸石硅源法微波合成ZSM-5/MCM-41复合分子筛,采用XRD、BET和NH₃-TPD技术对合成分子筛进行表征。结果表明,复合分子筛具有类MCM-41 的典型六方介孔结构,同时具有中孔和微孔结构,复合分子筛的总酸量介于HMCM-41酸量与HZSM-5酸量之间。利用脉冲微反装置考察合成分子筛的邻二甲苯异构化催化性能。结果表明,ZSM-5/MCM-41复合分子筛具有高于同硅铝比的MCM-41、ZSM-5和ZSM-5/MCM-41的机械混合物的催化活性。     

WO3-ZSM-5/MCM-41催化剂的合成 及其催化氧化脱硫研究

以氢氧化钠溶液处理微孔沸石ZSM-5来提供硅铝源,合成了ZSM-5/MCM-41复合结构型分子筛。采用XRD、N2吸附脱附、TEM等方法对其进行了表征,考察了其水热稳定性。实验结果表明,碱处理合成的ZSM-5/MCM-41同时具有微孔孔道和介孔孔道结构,并具有优于介孔MCM-41分子筛的水热稳定性。以ZSM-5/MCM-41为载体负载三氧化钨后应用于噻吩/正辛烷模拟油体系,双氧水为氧化剂,催化氧化脱硫,WO3-ZSM-5/MCM-41（三氧化钨质量分数为10%）表现出良好的催化性能,脱硫率可达到93.6%。     

Characterization and catalytic performance of mesoporous molecular sieves Al-MCM-41 materials

Mesoporous Al-MCM-41 materials of different Si/Al ratios have been synthesized and characterized by X-ray powder diffraction, ²⁷Al and ²⁹Si MAS NMR, differential thermogravimetric analysis, N₂ adsorption measurements, FT-IR and catalytic cracking of alkanes. The experimental results show that the incorporation of aluminium into the framework of MCM-41 has a great effect on the degree of long-distance order, the surface acidities and the mesoporous structures of the materials. With increase of the aluminium content, the amounts of tetrahedral framework aluminium and the acid sites on the samples increase, but the acid strength decreases. Al-MCM-41 materials exhibit high activity for n-C₁₆ ⁰ cracking and good selectivity for producing low carbon alkylenes, particularly for i-C₄ ⁼.     

Direct synthesis and superior catalytic performance of V-containing SBA-15 mesoporous materials for oxidative dehydrogenation of propane

V-containing SBA-15 mesoporous materials have been directly synthesized in an acidic and peroxidic medium. Compared to V/SBA-15 and V/SiO₂ samples prepared by impregnation method, the materials thus synthesized show larger surface areas, higher dispersion and reducibility of VO _x species, and superior catalytic performance for oxidative dehydrogenation of propane.     

环己烷催化氧化制环己酮的MCM-41催化剂研究

以十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,采用水热合成法制备纯MCM-41分子筛和掺杂不同金属离子的MCM-41分子筛,并采用等体积浸渍法将一定量的金属离子负载在纯MCM-41分子筛内表面上,制备了负载型和掺杂型2类不同的MCM-41分子筛催化剂.分别考察了负载和掺杂的金属种类、金属Cr负载和掺杂量等对环己烷氧化制环己酮中的催化活性和选择性的影响.研究表明:采用掺杂制备的MCM-41分子筛催化剂活性明显高于负载型MCM-41分子筛催化剂;Cr掺杂量增加,虽然环己烷氧化转化率增加,但产物选择性下降;掺杂Cr的MCM-41分子筛催化剂,用于环己烷氧化制环己酮,在Si与Cr摩尔比为50以下、反应温度75℃、H2O2与环己烷摩尔比为1.2的条件下,环己烷的转化率可达60%左右,环己酮和环己醇的总选择性可达94%以上.     

Conductivity of nanostructured mesoporous MCM-41 molecular sieve materials

MCM-41 molecular sieve materials have been investigated by means of impedance spectroscopy. Dielectric response of water confined in MCM-41 molecular sieve materials showed a power law dispersion, which was assigned to ac conductivity. This process, which occurs at temperatures close to room temperature, was found in all our investigated samples with the pore diameters ranging from 2.0 to 3.7 nm. Obtained values of the imaginary part of the complex dielectric permittivity were much larger than that of the bulk water. Such a phenomenon can be explained by the electrical response characteristic of the microstructural electrical network formed by water and hosting mesoporous silica material. The real part of conductivity has been calculated, and the influence of the pores size to electric conductivity and its mechanisms are discussed.     

Mo/MCM-41-Type mesoporous materials doubly promoted with Fe and Ni for hydrotreating reactions

A Si-MCM-41-type material was synthesized and impregnated with a Mo solution in order to get a 15% MoO₃ by weight. Then, it was doubly promoted with Ni and Fe in different proportions. Information on the structure of the precursors was revealed by XRD, TPR and surface area techniques. XRD results showed that the mesoporous materials were not affected for the successive impregnations carried out; while, their specific surface areas was partially blocked. These solids were tested for vanadyl octaethyl porphyrin hydrodeporphirinization (HDP), and individual and competitive reactions of dibenzothiophene (DBT) hydrodesulfurization (HDS) and 2-methyl naphthalene (2MN) hydrogenation (HYD).The DBT HDS activity was higher than 2MN HYD, and the presence of Fe in the catalysts did not produce a synergetic effect for this reactions. However, HDP activities of doubly promoted catalysts were superior to the monopromoted ones.     

用于氧化反应的改性介孔分子筛MCM-41研究进展

主要从金属掺杂、杂多酸负载和有机官能化等方面详细介绍了改性的MCM-41分子筛作为催化剂在氧化反应中的应用情况,分析了其优缺点。今后的研究重点将是进一步提高改性材料MCM-41分子筛的活性,解决活性组分溶脱现象以及水热稳定性等问题。     

Acidity study of Nb-containing MCM-41 mesoporous materials. Comparison with that of Al-MCM-41

The acidity of Nb-MCM-41 molecular sieves as well as their hydrogen forms was studied using FTIR spectroscopy with pyridine and 2,6-dimethylpyridine as probe molecules and in test reactions (isopropanol and cumene decomposition). The number of Lewis acid sites (LAS) and Brønsted acid sites (BAS) was estimated from the intensity of IR bands at 1450 and 1549 cm^-1 respectively. The acidity of niobium-containing materials was compared with that of Al related molecular sieves. The parent Al- and Nb-MCM-41 mesoporous materials studied in this work did not show Brønsted acidity which only appeared after ammonium exchange followed by calcination. The number and the strength of BAS was much higher on H,Al-containing material than that on H,Nb-containing molecular sieves. H,Nb-MCM-41 exhibited a higher concentration of LAS than H,Al related material.     

Co掺杂对Ce/MCM-41和Ce/SBA-15催化剂催化氧化甲苯性能的影响

以分子筛为载体,采用等体积浸渍法制备Ce/SBA-15、Ce/MCM-41、Ce Co/SBA-15和Ce Co/MCM-41催化剂。用N2吸附-脱附、X射线衍射、扫描电子显微镜、H2程序升温还原、X射线光电子能谱和傅立叶变换红外光谱等对载体和催化剂进行表征,并考察催化剂催化氧化甲苯的活性。结果表明,与载体相比,随着Ce和Co的浸渍,催化剂的比表面积和孔容下降,但仍然保持了载体的有序介孔结构。引入的Ce和Co没有进入分子筛骨架,而是以立方相固溶体形式存在于分子筛表面和孔道中。催化剂催化氧化甲苯活性顺序依次为:Ce Co/SBA-15>Ce Co/MCM-41>Ce/MCM-41>Ce/SBA-15。共浸渍Ce和Co的催化剂活性明显优于只浸渍Ce的催化剂,活性与其还原性能直接相关,Ce Co/SBA-15催化剂具有最低的还原温度和最好的供氧能力,从而表现出最优的催化性能。     

苯加氢催化剂Pd/MCM—41催化性能的研究

对负载型催化剂Pd/MCM—41进行了透射电镜及N2吸附表征。结果表明,金属Pd主要以纳米粒子的形式负载在分子筛表面,MCM—41的基本结构未被破坏。将Pd/MCM—41用于苯加氢反应,研究了反应温度和反应压力对催化活性的影响。结果表明,随着反应温度、反应压力的增加,苯的转化率得到有效提高。     

Near-infrared luminescent mesoporous MCM-41 materials covalently bonded with ternary thulium complexes

Two β-diketones 4,4,4-trifluoro-1-2-thenoyl-1,3-butanedione (Htta) and 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (Htfnb), which contain trifluoroalkyl chain, were selected as the main sensitizer for synthesizing Tm(L)₃phen (L = tta, tfnb) complexes. The two near-infrared (NIR) luminescent thulium complexes have been covalently bonded to the ordered mesoporous material MCM-41 via a functionalized 1,10-phenanthroline (phen) group 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) [The resultant mesoporous materials are denoted as Tm(L)₃phen–MCM-41 (L = tta, tfnb)]. The Tm(L)₃phen–MCM-41 (L = tta, tfnb) mesoporous materials were characterized by small-angle X-ray diffraction (XRD) and N₂ adsorption/desorption, and they show characteristic mesoporous structure of MCM-41. Luminescence spectra of the Tm(L)₃phen–MCM-41 (L = tta, tfnb) mesoporous materials were recorded and the corresponding luminescence decay curves were obtained. After ligand-mediated excitation, the emission spectra of the Tm(L)₃phen–MCM-41 (L = tta, tfnb) mesoporous materials show the characteristic NIR-luminescence of the Tm³⁺ ion. The full width at half maximum (fwhm) of the 1474-nm emission band are 96 and 100 nm for Tm(tta)₃phen–MCM-41 and Tm(tfnb)₃phen–MCM-41, respectively. The good luminescent performances enable these NIR-luminescent mesoporous materials to have potential applications in optical amplification [broadening amplification band from C band (1530–1560 nm) to S⁺ band (1450–1500 nm)]. Furthermore, the comparison of the luminescence behavior for Tm(tta)₃phen–MCM-41 and Tm(tfnb)₃phen–MCM-41 mesoporous materials was investigated. It shows that Tm(tfnb)₃phen–MCM-41 is somewhat superior to Tm(tta)₃phen–MCM-41 as optical amplifier.     

MCM-41-HY介孔-微孔复合分子筛的水热合成

以微孔分子筛HY浆液为母液,合成介孔-微孔复合分子筛MCM-41-HY。通过XRD、NH_3-TPD和N_2吸附-脱附等手段对复合材料进行了表征,并对复合分子筛的水热稳定性进行了考察。结果表明,复合分子筛MCM-41-HY具有中孔分子筛MCM-41和微孔HY型沸石的特点,并且与纯MCM-41分子筛相比,复合分子筛的酸强度明显增强,水热稳定性提高。     

Acidity and catalytic activity of the mesoporous aluminosilicate molecular sieve MCM-41

The acidity and catalytic properties of aluminosilicate mesoporous molecular sieves with the MCM-41 structure and bulk Si/Al ratios in the 10–60 range have been investigated. The incorporation of 4-coordinate aluminium into the structure of MCM-41 generates both BrØnsted and Lewis acid sites in amounts increasing with the degree of incorporation. However, the BrØnsted/Lewis acid population ratio is independent of the content of aluminium. The number and strength of acid sites generated are comparable to those of a pillared acid-activated clay and lower than in zeolite H-Y with Si/Al=3.65. Aluminosilicate MCM-41 is a moderate catalyst for the conversion of cumene which proceeds predominantly via catalytic cracking to propene and benzene. The sample of MCM-41 with the highest content of framework aluminium (Si/Al=10) has the largest number of BrØnsted acid sites and exhibits highest catalytic activity.     

ZSM-5/MCM-41复合分子筛的制备及对乙醇脱水的催化活性

以微孔ZSM-5分子筛为母体,采用NaOH溶液对其进行预处理,再在水热条件下以十六烷基三甲基溴化铵（CTMAB）为模板剂制备了ZSM-5/MCM-41介微孔复合分子筛,考察了预处理温度、晶化温度等因素对复合分子筛结构和形貌的影响。进一步考察了该复合分子筛催化剂在乙醇脱水反应中的催化活性。结果表明,ZSM-5分子筛在2.0 mol/L NaOH溶液中于110℃预处理20 h,再于110℃水热晶化20 h制备的分子筛具有良好的介微孔复合结构;该复合分子筛经NH4NO3溶液离子交换制备的氢型催化剂在乙醇脱水催化反应中表现出良好的性能。当乙醇WHSV=0.5 h-1时,最佳反应温度为240～255℃,乙醇转化率〉99%,乙烯选择性〉96%。     

High loading of C60 in nanochannels of mesoporous MCM-41 materials

Very high loadings of C₆₀ and C₆₀⁻ anions in MCM-41 mesoporous materials have been achieved by modifying the channel surface with amino-functional group. Detailed physical properties of these mesoporous materials containing C₆₀ were characterized by EPR, NMR, XRD, FTIR and UV–vis spectroscopic techniques. The surface area and pore size of mesoporous materials were further determined by N₂ adsorption–desorption isotherms. The mesopores of MCM-41 show sieving behavior in excluding the larger sized C₁₂₀O while absorbing the smaller C₆₀ as indicated in the EPR studies.     

Rapid syntheses of ultrafine LaMnO3 nano-crystallites with superior activity for catalytic oxidation of toluene

Supercritical water (sc-H₂O) reaction environment was evidenced with the capability to dramatically facilitate the solid-state reaction between hybrid oxides. This led to one-step and rapid (within several seconds) syntheses of ultrafine LaMnO₃ nano-crystallites (at ca. 6 nm) with no need of additional heat-treatment (literaturelly need to be heat-treated at 600–800 °C for 4–6 h in static air). The ultrafine LaMnO₃ was shown with remarkable surface area and distinct oxygen mobility and reducibility, which yielded an activation energy (Ea) in toluene oxidation at only ca. 54.3 kJ/mol, comparable to some noble metal catalysts.