Covalent grafting of polyacrylamide onto mesoporous MCM-41 silica via free radical polymerization

MCM-41 mesoporous silicas were covalently modified with polyacrylamide (PAAm) by a novel grafting strategy. The effect of various parameters such as monomer concentration, reaction time, and temperature on the content of PAAm onto MCM-41 silicas were studied. Modified silicas were characterized by X-ray diffraction (XRD), infrared spectroscopy, FT-IR, thermogravimetric analysis, nitrogen adsorption–desorption analyses, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy which confirmed the grafting process. According to XRD, SEM and TEM results, PAAm-modified MCM-41 silica did not show changes in its morphology and mesostructure by comparing with pristine MCM-41. Nitrogen adsorption–desorption studies showed that the attaching of PAAm onto MCM-41 silica decreased the values of pore size, pore volume and surface area.     

Influence of the reaction conditions on the thermal stability of mesoporous MCM-48 silica obtained at room temperature

The thermal stability of MCM-48 silicas synthesized at room temperature under basic conditions using cetyltrimethylammonium bromide (CTAB) as template was evaluated as a function of the reaction time, CTAB/TEOS and H₂O/ethanol molar ratios and ammonium hydroxide (NH₄OH) concentration in the initial gel composition. Samples were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analyses, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that synthesis conditions affect the structural and thermal properties of the MCM-48 silicas. These silicas exhibited a size from 200 to 500 nm with spherical morphology.     

Adsorption performance of mesoporous silicas towards a cationic dye. Influence of mesostructure on adsorption capacity

The dye adsorption performance of four mesoporous silicas with different structure and textural properties, MCM-41, MCM-48, SBA-15 and mesocellular silica foam (MCF), was studied and compared by using toluidine blue O (TBO) as dye model in aqueous solution. These materials were characterized by X-ray diffraction (XRD), small-angle X-ray scattering, nitrogen adsorption-desorption analyses, and transmission electron microscopy (TEM). The effect of some parameters such as adsorbent dosage, contact time, temperature, and pH on the TBO removal in aqueous solution was studied. Results showed that adsorption capacity raised when adsorbent dosage, contact time and pH solution were increased while an increase in temperature decreased the adsorption of TBO. Langmuir, Freundlich and Temkin isotherm models were employed to elucidate the adsorption mechanism while the adsorption rate data were analyzed according to the pseudo-first and second-order kinetic models. Results showed that adsorption of TBO onto MCM-48, SBA-15, and MCF fitted well the Freundlich isotherm model while the kinetic studies showed that adsorption process could be better described by the pseudo-second-order model for all mesoporous silicas. Finally, some solvents were evaluated to carried out dye desorption from the TBO-loaded mesoporous silicas founding that acetic acid was the most efficient.     

介孔SiO2薄膜的制备与表征

采用浸涂法,以载玻片为基底,十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,丙三醇为成膜干燥控制剂,制备出有序的介孔SiO2薄膜.利用X射线衍射仪(XRD)、红外光谱(IR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对其结构进行表征.XRD测试结果表明,合成的薄膜具有MCM-41介孔结...     

石蜡/MCM-41复合相变材料的结构及热性能

以石蜡为相变材料、SiO2介孔分子筛MCM-41为载体,采用溶液浸渍法制备了石蜡/MCM-41复合相变储能材料。应用SEM与TEM测试了复合材料的微观结构,利用TG-DSC测定了复合材料的相变温度、相变潜热及相变可逆性,通过FTIR对复合材料的兼容性进行了表征。实验表明,复合材料表面孔结构改善了相变可逆性,复合相变储能材料中石蜡的适宜质量分数为40%,相变温度为66.6℃,相变潜热为135.3 J/g。石蜡与MCM-41间是简单的嵌合关系,复合材料具有良好的热稳定性和兼容性。     

Modification of silica nanoparticles with hydrophilic sulfonated polymers by using surface-initiated redox polymerization

Sulfonated polymer/silica hybrid nanoparticles were prepared by free radical polymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid (PAMPS-g-SN) and styrene sulfonic acid sodium salt (PSSA-g-SN), initiated on the surfaces of aminopropyl-functionalized silica nanoparticles (ASN). Ce(IV) ammonium nitrate/nitric acid and sodium dodecyl sulfate were used as redox initiator and stabilizer, respectively. ASN Nanoparticles were synthesized by a covalently attached 3-aminopropyltriethoxysilane onto the surface of silica nanoparticles. Sulfonated monomers (AMPS or SSA) were then grafted onto the ASN nanoparticles, ultrasonically dispersed in water, using redox initiator system at 40?°C. ASN, PAMPS-g-SN and PSSA-g-SN nanoparticles were characterized by Fourier transform infrared (FTIR), thermogravimetry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. FTIR and TGA results indicated that both AMPS and SSA monomers were successfully grafted onto the silica nanoparticles. The grafted amounts of sulfonated polymers onto the silica nanoparticles were estimated from TGA thermograms to be 46 and 22?% for PAMPS and PSSA, respectively. From SEM and TEM micrographs, the average-diameters of the polymer-grafted silica nanoparticles were measured to be <50?nm with a (semi)spherical morphology, in which several silica nanoparticles were able to form a core with PAMPS or PSSA existing around the silica nanoparticles.     

Characteristics of vanadium-substituted mesoporous silica with wormhole framework structure: effects of vanadium content

Vanadium-substituted wormhole framework structure (V-WMS) mesoporous silicas (V-WMS) with various Si/V ratios in the range of 15 and 200 were prepared at ambient temperature by neutral surfactant templating pathway. The materials were synthesized by using dodecylamine as a template and tetraethylorthosilicate as a silicon source. They were characterized by energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), N₂ adsorption–desorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared absorption spectroscopy (FT-IR) and ultraviolet-visible absorption spectroscopy. V-WMS samples shown characters of larger framework wall thickness, small crystallite domain sizes, and complementary textural mesoporosities in comparison with M41S materials. These mesoporous V-WMS samples exhibited irregularly shaped mesoscale fundamental particles which aggregated into larger particles. They also demonstrated better thermal stability than MCM-41. An absorption band of FT-IR at ca. 960 cm⁻¹ was assigned to the vibration of Si–O–V linkages. These samples also showed one strong UV–visible absorbance with overlapping maxima at about 255 nm. The results show that vanadium was incorporated into the structure of wormhole mesoporous silica (WMS). However, for V-WMS with high vanadium content (Si/V < 25), a broad shoulder in XRD pattern was observed at about 3–4°, suggesting the presence of impurity phase of vanadium species in the sample. The efforts in preparing V-WMS specimens by neutral-template synthesis route had led to new mesoporous silica molecular sieves with catalytically active vanadium centers.     

HEC-g-P4VP的pH值诱导胶束化行为

采用硝酸铈铵（CAN,Ce4+）自由基引发聚合合成了羟乙基纤维素接枝聚4-乙烯基吡啶（HEC-g-P4VP）聚合物。并用FTIR、1H NMR确证了共聚物结构。将这种纤维素接枝改性聚合物溶解在不同pH值的水溶液中,研究了它的胶束化行为。利用扫描电镜（SEM）和透射电镜（TEM）相结合,对胶束化行为进行了观察,结果表明HEC-g-P4VP能够形成清晰的核壳结构。在不同pH值条件下,所形成的核壳结构有所变化。说明HEC-g-P4VP在溶液中具有一定的pH值诱导胶束化行为。最后,采用滴体积法对HEC-g-P4VP在水溶液中的表面张力进行了研究,随着接枝率的提高,其表面张力有降低的趋势。     

Gas transport behavior of DMDCS modified MCM-48/polysulfone mixed matrix membrane coated by PDMS

Mesoporous MCM-48 silica was synthesized by templating method and the structure of particles was characterized by XRD, TEM and N₂ adsorption techniques. The surface modification of particles in order for introducing into PSF matrix was performed by dimethyldichlorosilane (DMDCS) silylation agent. SEM images of as-synthesized and modified MCM-48/PSF MMMs indicate that in the modified MCM-48 silica particles adhered well to the PSF matrix and that the synthesized MMMs were defect free. The incorporation of MCM-48 particles in to the PSF matrix and also surface coating of these MMMs by polydimethylsiloxane (PDMS) were performed. The quality of surface coating was investigated by SEM images and permeability tests. For all gases tested (N₂, CO₂, CH₄ and O₂), the permeabilities increased in proportion to the weight percent of MCM-48 present in the film and the calculated CO₂/CH₄ and O₂/N₂ selectivities of PDMS coated membranes showed enhancement in ideal and actual selectivities both.     

硬脂酸/MCM-41复合相变材料研究

以硬脂酸为相变材料,介孔分子筛MCM-41为载体,采用溶液浸渍法制备了硬脂酸/MCM-41复合相变储能材料。应用SEM和TEM测试了复合材料的微观结构,利用TG-DSC分析了复合材料的相变温度、相变潜热及相变可逆性,通过FT-IR对复合材料的兼容性进行了表征。结果表明,复合材料表面具有多孔结构,改善了复合材料的相变可逆性,复合相变储能材料中硬脂酸的最大质量分数为50%,相变温度为57.8℃,相变潜热为276.4 J/g。分析表明,硬脂酸与MCM-41间是简单的嵌合关系,复合材料具有良好的热稳定性和兼容性。     

A high CO2 permselective mesoporous silica/carbon composite membrane for CO2 separation

Ordered mesoporous silica/carbon composite membranes with a high CO₂ permeability and selectivity were designed and prepared by incorporating SBA-15 or MCM-48 particles into polymeric precursors followed by heat treatment. The as-made composite membranes were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and N₂ adsorption, of which the gas separation performance in terms of gas permeability and selectivity were evaluated using the single gas (CO₂, N₂, CH₄) and gas mixtures (CO₂/N₂ and CO₂/CH₄, 50/50 mol.%). In comparison to the pure carbon membranes and microporous zeolite/C composite membranes, the as-made mesoporous silica/C composite membranes, and the MCM-48/C composite membrane in particular, exhibit an outstanding CO₂ gas permeability and selectivity for the separation of CO₂/CH₄ and CO₂/N₂ gas pairs owing to the smaller gas diffusive resistance through the membrane and additional gas permeation channels created by the incorporation of mesoporous silicas in carbon membrane matrix. The channel shape and dimension of mesoporous silicas are key parameters for governing the gas permeability of the as-made composite membranes. The gas separation mechanism and the functions of porous materials incorporated inside the composite membranes are addressed.     

Textural/structural,stability and morphological properties of mesostructured silicas (MCM-41 and MCM-48) prepared using different silica sources

A series of MCM-41 and MCM-48 samples have been synthesized under hydrothermal and static conditions using different silica sources (fumed silica, silica sol and ethyl silicate) and characterized by powder XRD, scanning electron microscopy and N₂ adsorption. The silica source reactivity trend observed was as: ethyl silicate > fumed silica > silica sol. However, the extent of contraction caused by calcination, magnitude of the wall thickness and stability were found to depend not only upon the type of silica source used but also on the type of structure formed. Noticeable morphological differences were observed in case of only MCM-41 when silica sources were varied.     

Ce-MCM-48分子筛的合成与吸附动力学研究

以硅溶胶为硅源、十六烷基三甲基溴化铵( CTAB)为模板剂,采用物质的量配比为Ce2O3:SiO2:CTAB:H2O:NaOH =0.015:1:0.45:60:0.48,静态水热合成了Ce-MCM-48分子筛,采用XRD、SEM (EDS)、TEM等方法对其进行了表征,并对其进行了吸附动力学研究.结果表明,本文成功合成了Ce-MCM-48介孔分子筛,其拟一级吸附动力学方程为lg(qe-q)=-0.4365-0.01026t,R2=0.9289,拟二级吸附动力学方程为t/qt =0.4027+0.27818t,R2=0.9999,相对拟一级反应模型,这个结果相关性更好,更能真实地反映分子筛吸附亚甲蓝溶液的反应机理.     

以阳离子Gemini表面活性剂为模板合成介孔氧化硅

以阳离子Gemini表面活性剂——双十六烷基三甲基溴化铵[C16H33N+(CH3)2(CH2)2N+(CH3)2C16H33].2Br-(G16-2-16)为模板剂,正硅酸乙酯为硅源,在n(SiO2)∶n(G16-2-16)∶n(NH3)∶n(H2O)=1∶0.1∶9∶110的条件下,在弱碱性环境中用水热法合成了平均孔径3.1 nm、比表面积906.71 m2/g、孔容0.93 cm3/g、具有二维六角结构且高度有序的介孔氧化硅MCM-41。采用小角XRD、高分辨透射电镜(HRTEM)、N2吸附-脱附分析和热重-微分热重法(TG-DTG)对其结构进行了考察,分析了不同模板剂浓度对材料结构有序度的影响。结果表明,n(G16-2-16)/n(TEOS)=0.1时,合成的材料有序度最高。     

Nano Composite from Coal Modified Novolac Resin

Coal-modified novolac/clay nanocomposites were synthesized using clay as reinforcing materials. It was found that coal-modified novolac resin based silica nano-composites showed improved tensile strength compared to that of neat novolac resin. The structure of the nanocomposites was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Scanning electron microscopy (SEM) studies have also been undertaken to see the morphology of the nanocomposites prepared. The results obtained are being reported.     

MCM-41介孔碳材料的合成及其电化学性能研究

该文以十六烷基三甲基溴化铵（CTAB）为模板剂,可溶性淀粉(Starch)为碳源,通过软模板法一步合成了高度有序的介孔碳材料。通过热重分析（TG）、X-射线衍射（XRD）、N2吸附-脱附和透射电子显微镜（TEM）等对材料的结构进行了表征。结果表明：当模板剂与可溶性淀粉质量比为m(CTAB):m(Starch)=1.0：1.5,650 ℃焙烧碳化3 h,并用氢氟酸去除二氧化硅后,所得到的MCM-41有序介孔碳材料（OMC-650）的比表面积为985 m2/g,平均孔径为孔径分布均匀,平均孔径为2.5 nm。XRD和TEM分析表明,OMC-650具有典型的MCM-41结构特征,有序性良好。以OMC-650作为工作电极,氧化汞为参比电极,铂为辅助电极,用6 M•L-1 KOH做电解液,测其比电容为150 F/g,且经过1000次循环后,其比电容仍为138 F/g,为原电容的92%,说明所合成的材料具有良好的电容稳定性。     

Grafting of vinyl acetate onto low density polyethylene—starch biodegradable films for printing and packaging applications

Starch‐based biodegradable low‐density polyethylene (LDPE) films were used for graft copolymerization of vinyl acetate with ceric ammonium nitrate (CAN) in aqueous acidic medium as redox initiator with nitric acid. The extent of grafting was examined by Fourier‐transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR) spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The objective behind the grafting of vinyl acetate onto the LDPE–starch biodegradable films is to make these suitable for printing and packaging applications without affecting the biodegradability of the original films. Copyright © 2004 Society of Chemical Industry     

苄基磺酸化MCM-41介孔分子筛的合成、表征及催化酯化性能

MCM-41介孔分子筛先后与苄基氯和氯磺酸接枝反应,得到苄基磺酸介孔分子筛(SBM)。通过X射线多晶衍射(XRD)、氮气吸附脱附、红外光谱(IR)、有机元素分析、扫描电镜(SEM)等方法对所得样品进行了表征。研究结果表明,MCM-41表面硅羟基与苄基氯反应,接枝量w(C)=6.68%;进一步磺化,接枝率w(S)=8.46%。XRD等分析结果表明,经过两步接枝反应,SBM仍然具有介孔结构特征,比表面积和孔容分别为366.9 m2/g、0.349 cm3/g。以SBM为催化剂,催化合成柠檬酸三丁酯;在n(酸)∶n(醇)=1.0∶9.0,w(催化剂)=3%,反应温度110℃,回流时间7 h的条件下,柠檬酸转化率可达93.2%;催化剂重复使用4次柠檬酸转化率为76.3%。     

纳米介孔分子筛用于吡格列酮长效缓释的研究

主要研究以CTAB（十六烷基三甲基溴化铵）为模板剂,TEOS（正硅酸乙酯）为硅源的二氧化硅介孔材料（MCM-41）作为药物盐酸吡格列酮输送体系的可能性,研究药物在这种介孔材料中的吸附/释放特性及其影响因素。采用粉末X射线衍射法（XRD）,傅里叶变换红外光谱法（FT-IR）和扫描电子显微镜（SEM）来表征吸附前后的介孔分子筛。将合成的分子筛用作吡格列酮药物的载体,实时检测制备药物在模拟胃液中的释放过程发现,在药物释放开始后的第1h内,吡格列酮释放速率非常快,1h后释放率达到17.93%,在9h后释放率达到37.88%,在释放34h后,释放率达到62.74%。     

Novel utilization of MCM-22 molecular sieves as supports of cobalt catalysts in the Fischer–Tropsch synthesis

Cobalt catalysts (2–10 wt% Co) supported on silica-rich MCM-22 zeolites have been prepared by impregnation with aqueous Co(NO₃)₂ solutions. The catalysts are characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), nitrogen adsorption, solid state nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The catalytic properties for the Fischer–Tropsch synthesis (FTS) at 280 °C, 12.5 bar and H₂/CO = 2 are evaluated. The catalysts supported on MCM-22 exhibit the highest selectivity to long-chain (C₅₊) hydrocarbons when MCM-22 supports are synthesized with the appropriate Si/Al ratio.