有序介孔二氧化硅对正丁醛的吸附性能

合成了一系列具有不同孔结构与性质的有序介孔二氧化硅材料SBA-15、MCM-41、SBA-16、KIT-6,同时通过改变水热温度制备了不同孔径大小的SBA-15,并利用小角X射线散射、透射电镜、扫描电镜和氮气吸附-脱附等手段,对其介孔结构进行了表征.以正丁醛为探针分子,考察了其对有机醛的吸附,并与Y-沸石的吸附性能做了对比.结果表明,材料的介孔比表面积与其对正丁醛的吸附量成正比,吸附等温线符合Langmuir模型,属于单层吸附,具有最大介孔比表面积的MCM-41对正丁醛的吸附量最大(484 mg·g-1).最后将SBA-15添加到卷烟滤嘴中,实验结果表明,SBA-15能显著降低卷烟烟气中巴豆醛的释放量.     

介孔材料氨基表面修饰及其对CO2的吸附性能

采用接枝方法在介孔材料MCM-41和SBA-15的孔道内表面进行氨基化修饰, XRD、29Si-NMR、FT-IR、TGA、BET等测试结果表明, 氨丙基三乙氧基硅烷(APTS)和氨乙基氨丙基甲基二甲氧基硅烷(AEAPMDS)都分别接枝在介孔材料的孔道内, 表面氨基修饰量约为1.5-2.9 mmol·g-1. 表面修饰后介孔材料的孔道仍高度有序, 但比表面积减小. 表面修饰前后介孔材料对CO2的吸附性能发生显著变化, 由于物理吸附转化为以氨基为活性中心的化学吸附, 吸附量从修饰前的0.67 mmol·g-1提高到2.20 mmol·g-1.     

巯基功能化介孔材料高效锚定钯负载型催化剂的制备及其苯酚加氢催化性能

以含巯基官能团有机硅烷修饰的介孔材料MCM-41和SBA-15为载体, 采用浸渍-氢气还原法制备了高分散和高活性的负载型Pd催化剂. X射线衍射、N₂吸附-脱附和透射电子显微镜表征结果显示, 所制Pd催化剂Pd-SH-MCM-41和Pd-SH-SBA-15具有很好的长程有序结构、分布均匀的孔径、高比表面积及高度分散的Pd颗粒. 苯酚加氢反应结果表明, 以Pd-SH-MCM-41和Pd-SH-SBA-15为催化剂时, 在80℃, 1.0MPa反应1h, 苯酚转化率达99%以上, 环己酮选择性为98%. 它们的催化活性为商业Pd/C催化剂的5倍, Pd/MCM-41和Pd/SBA-15催化剂的3倍. 这可归因于介孔材料表面修饰的巯基官能团对Pd的锚定作用, 避免了Pd颗粒的团聚, 使其高度分散在介孔材料上.     

孔道型微孔和介孔分子筛的改性及超级绝热性能

在水热体系中合成了具有规则孔道结构的微孔分子筛ZSM-5和介孔分子筛MCM-41,SBA-15,MAS-5,通过改变材料表面的电性对介孔材料进行了化学修饰.采用X射线衍射(XRD)和扫描电子显微镜(SEM)对样品的结构、形貌进行了表征;通过氮气吸附-脱附测试了产物的比表面积,采用BJH法计算孔分布和孔容;将制得的样品压制成绝热材料后,进行导热性质测定.常温(25℃)常压下,有序介孔分子筛MCM-41的导热系数为0.038 W·m-1·K-1,具有少量微孔结构的MAS-5的导热系数为0.035W·m-1·K-1,二者均为超级绝热材料.材料经改性后,绝热性能有所提高:MCM-41的导热系数降至0.028 W·m-1·K-1,MAS-5的导热系数降至0.017 W·m-1·K-1.结合纳米介孔材料导热理论模型进行分析,发现纳米孔绝热材料的孔径越小,孔隙率越大,绝热性能好;介孔分子筛的导热系数与其孔壁厚度、孔径大小以及孔隙率有关.     

萘在介孔分子筛MCM-41与SBA-15上的吸附特性研究

对低浓度气相萘在两种常见介孔分子筛MCM-41和SBA-15上的吸附特性进行研究。得到了萘在两种吸附剂上的吸附等温线和不同初始浓度下的穿透曲线,并分别与吸附等温线模型(Langmuir、Freundlich、D-R)和恒定浓度波动力学模型进行了拟合。结果表明, Langmuir模型能很好描述低浓度气相萘的吸附等温线(R²均在99%以上);具有微孔结构的SBA-15对萘的吸附能力要优于仅具备介孔结构的MCM-41。动力学模型在初始浓度较低时能较好地预测萘在吸附剂上的穿透曲线,且在SBA-15上的相关系数高于MCM-41;萘在2.76 mol/L时具有较大介孔的SBA-15的总传质系数K_a更高,表明萘在SBA-15上的总传质阻力更低,更能较快达到传质平衡。     

氨基功能化SBA-15的直接合成及其对CO_2的吸附性能研究

通过直接法合成了氨基功能化SBA-15介孔材料。使用X-射线粉末衍射法(XRD),N2吸-脱附,透射电子显微(TEM)等技术对氨基功能化材料进行了表征。实验结果表明:当反应原料中nAPTES/(nAPTES+nTEOS)≤0.20时,APTES功能化的材料都具有典型的介孔SBA-15结构;但当nAPTES/(nAPTES+nTEOS)≥0.225时,由于氨基对SBA-15结构的副作用导致SBA-15介孔结构坍塌。在氟离子辅助合成下可以获得高含量氨基(反应原料中nAPTES/(nAPTES+nTEOS)的比值为0.25)功能化的SBA-15材料,且此材料中的介孔孔径和BET比表面积都较大。CO2吸附结果表明,随着反应原料中APTES含量提高,所合成的材料对CO2的吸附量相应增加,同时在101kPa和25℃下,通过氟离子辅助合成的材料对CO2的吸附量远远优于无氟离子辅助合成材料的。本研究还对后嫁接法和直接合成法获得氨基功能化SBA-15介孔材料的优缺点进行了讨论。     

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。     

氨基改性介孔二氧化硅的制备及其吸附性能研究

合成了一种具有较大孔径的氨基改性介孔二氧化硅材料(m-MCF)。通过XRD、TEM、低温氮吸附、TGA、FTIR以及原子吸收光谱(AAS)等表征方法对产物的结构和性能进行的分析表明:利用三甲基苯为扩孔剂制备得到的介孔材料具有较大的孔径，有利于功能基团对孔内表面的改性。当氨基改性介孔材料后，该材料仍然保留较大的孔径(22 nm)和较高的比表面积(444 m²·g^-1)。研究发现:与改性而未扩孔的介孔二氧化硅SBA-15相比，该材料对铜离子的吸附能力提高了2倍。     

铈掺杂的介孔分子筛的水热合成与结构性能

以硅酸钠、硝酸铈铵为原料,十六烷基三甲基溴化铵为模板剂,通过水热法合成铈掺杂的介孔分子筛CeMCM-41.分别采用X射线粉末衍射(XRD)、透射电子显微镜(TEM)、红外光谱(FT-IR)、紫外-可见分光光度计(UV-Vis)和N2吸附-脱附等技术对产物的晶相、结构、形貌、比表面积和孔径进行表征.同时研究硅铈物质的量比对合成材料结构性能的影响.实验结果表明:水热条件下成功合成出铈掺杂的MCM-41介孔分子筛,其比表面积为480.5～1 295.2m2/g,平均孔径在2.70～6.29 nm之间.随着稀土元素铈的掺杂量的增加,CeMCM-41介孔分子筛的比表面积和孔体积变小,介孔有序性变差.     

以离子液体为模板剂合成MCM-41的研究——不同扩孔剂对介孔分子筛MCM-41孔径结构的影响

以离子液体为模板剂, 正硅酸乙酯为硅源, 研究了扩孔剂三甲苯, 癸烷, 以及三甲苯与癸烷1∶1的混合物对介孔分子筛MCM-41结构的影响, 采用XRD以及氮吸附-脱附分析技术对合成的介孔分子筛MCM-41进行了表征.结果表明: 三种扩孔剂中以三甲苯与癸烷1∶1的混合物效果最优, MCM-41的孔径可达到4.5 nm, 并且可以提高介孔分子筛的比表面积与结晶度.扩孔剂的最佳添加量为: 扩孔剂与模板剂之比等于1.0;最佳晶化温度120 ℃.     

Prearation of Highly Ordered Mesoporous Silica Materials and Application as Enzeme Supports

An enzyme, horseradish peroxidase (HRP), was adsorbed in the manner of single immersion method on the silica mesoporous materials, FSM-16, MCM-41 and SBA-15 with various pore diameters from 27 to 92 and their enzymatic activity in an organic solvent and the thermal stability were studied. FSM-16 and MCM-41 showed larger amount of adsorption of HRP than SBA-15 or silica gel,when the pore sizes were larger than the spherical molecular diameter of HRP (ca 64×37). The increased enzyme adsorption capacity may be due to the surface characteristics of FSM-16 and MCM-41, which would be consistent with the observed larger adsorption capacity of cationic pigment compared with anionic pigment for these materials. The immobilized HRP on FSM-16 and MCM-41 with pore diameter above 50 showed the highest enzymatic activity in an organic toluene and thermal stability in aqueous solution at the temperature of 70℃. The immobilized enzymes on the other mesoporous materials including large or small pore sized FSM-16 showed lower enzymatic activity in an organic solvent and the thermal stability. Both surface character and size matching between pore sizes and the molecular diameters of HRP were important in achieving high enzymatic activity in organic solvent and high thermal stability.     

NSAID naproxen in mesoporous matrix MCM-41: drug uptake and release properties

Hexagonally ordered mesoporous silica material MCM-41 (S_BET?=?1090?m²/g, pore size?=?31.2 ?) was synthesized and modified by 3-aminopropyl ligands. The differences in an uptake and subsequent release of anti-inflammatory drug naproxen from unmodified and amino modified MCM-41 samples were studied. The prepared materials were characterized by high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), nitrogen adsorption/desorption, Fourier-Transform Infrared Spectroscopy (FT-IR), Small-angle X-ray scattering (SAXS), thermoanalytical methods (TG/DTA) and elemental analysis. The amount of the drug released was monitored with thin layer chromatography (TLC) with densitometric detection in defined time intervals. The amounts of the released naproxen from mesoporous silica MCM-41/napro and amine-modified silica sample A-MCM-41/napro were 95 and 90% of naproxen after 72?h. In this study we compare the differences of release profiles from mesoporous silica MCM-41 and mesoporous silica SBA-15.     

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.     

Hydrogen bonding of water confined in mesoporous silica MCM-41 and SBA-15 studied by 1H solid-state NMR

The adsorption of water in two mesoporous silica materials with cylindrical pores of uniform diameter, MCM-41 and SBA-15, was studied by 1H MAS (MAS=magic angle spinning) and static solid-state NMR spectroscopy. All observed hydrogen atoms are either surface -SiOH groups or hydrogen-bonded water molecules. Unlike MCM-41, some strongly bound water molecules exist at the inner surfaces of SBA-15 that are assigned to surface defects. At higher filling levels, a further difference between MCM-41 and SBA-15 is observed. Water molecules in MCM-41 exhibit a bimodal line distribution of chemical shifts, with one peak at the position of inner-bulk water, and the second peak at the position of water molecules in fast exchange with surface -SiOH groups. In SBA-15, a single line is observed that shifts continuously as the pore filling is increased. This result is attributed to a different pore-filling mechanism for the two silica materials. In MCM-41, due to its small pore diameter (3.3 nm), pore filling by pore condensation (axial-pore-filling mode) occurs at a low relative pressure, corresponding roughly to a single adsorbed monolayer. For SBA-15, owing to its larger pore diameter (8 nm), a gradual increase in the thickness of the adsorbed layer (radial-pore-filling mode) prevails until pore condensation takes place at a higher level of pore filling.     

Electron microscopy study of novel Pt nanowires synthesized in the spaces of silica mesoporous materials.

Structures of Pt-nanowires, synthesized in channels of silica mesoporous materials MCM-41, SBA-15 and MCM-48, were investigated by transmission electron microscopy. One dimensional (1D) Pt-nanowires were formed inside the channels of the MCM-41, and were single crystals with a length of several tens to several hundreds nanometers and a diameter of ca. 3 nm pt-nanowires synthesized in SBA-15 formed a new 3D-network following 3D-pore geometry of SBA-15; that is, the main 1D-channels are interconnected to each other through randomly distributed tunnels. These Pt-nanowires showed a well single crystalline. MCM-48 has two non-intersecting chiral channels, and Pt-networks were mostly formed in one of the two channels. Therefore the networks were also chiral; however, the chirality of Pt-networks remained to be determined. It was shown that all Pt-nanowires were formed following the channel geometries of silica mesoporous materials used.     

Investigation of Mg modified mesoporous silicas and their CO2 adsorption capacities

CO₂ adsorption properties on Mg modified silica mesoporous materials were investigated. By using the methods of co-condensation, dispersion and ion-exchange, Mg²⁺ was introduced into SBA-15 and MCM-41, and transformed into MgO in the calcination process. The basic MgO can provide active sites to enhance the acidic CO₂ adsorption capacity. To improve the amount and the dispersion state of the loading MgO, the optimized modification conditions were also investigated. The XRD and TEM characteristic results, as well as the CO₂ adsorption performance showed that the CO₂ adsorption capacity not only depended on the pore structures of MCM-41 and SBA-15, but also on the improvement of the dispersion state of MgO by modification. Among various Mg modified silica mesoporous materials, the CO₂ adsorption capacity increased from 0.42 mmol g⁻¹ of pure silica SBA-15 to 1.35 mmol g⁻¹ of Mg–Al–SBA-15-I1 by the ion-exchange method enhanced with Al³⁺ synergism. Moreover, it also increased from 0.67 mmol g⁻¹ of pure silica MCM-41 to 1.32 mmol g⁻¹ of Mg–EDA–MCM-41-D10 by the dispersion method enhanced with the incorporation of ethane diamine. The stability test by 10 CO₂ adsorption/desorption cycles showed Mg–urea–MCM-41-D10 possessed quite good recyclability.     

Gas adsorption in mesoporous micelle-templated silicas: MCM-41, MCM-48, and SBA-15

This paper reports a molecular simulation and experimental study on the adsorption and condensation of simple fluids in mesoporous micelle-templated silicas MCM-41, MCM-48, and SBA-15. MCM-41 is described as a regular cylindrical silica nanopore, while SBA-15 is assumed to be made up of cylindrical nanopores that are connected through lateral channels. The 3D-connected topology of MCM-48 is described using a gyroid periodic minimal surface. Argon adsorption at 77 K is calculated for the three materials using Grand Canonical Monte Carlo simulations. Qualitative comparison with experiments for nitrogen adsorption in mesoporous micelle-templated silicas is made. The adsorption isotherm for SBA-15 resembles that for MCM-41. In particular, capillary condensation and evaporation are not affected by the presence of the connecting lateral channels. In contrast, the argon adsorption isotherm for MCM-48 departs from that for MCM-41 having the same pore size. While condensation in MCM-41 is a one-step process, filling of MCM-48 involves two successive jumps in the adsorbed amounts which correspond to condensation in different domains of the porosity. The condensation pressure for MCM-48 is larger than that for MCM-41. We attribute this result to the morphology of the MCM-48 surface (made up of both concave and convex regions) that differs from that for MCM-41 (concave only). Our results suggest that the pore connectivity affects pore filling when the size of the connections is comparable to that of the nanopores.     

有机胺修饰具有较大孔径介孔材料的二氧化碳吸附性能

以非离子表面活性剂P123为模板剂,正硅酸甲酯为硅源,通过加入不同的扩孔剂制得具有较大孔径的SBA-15类介孔材料,并采用粉末X射线衍射(XRD)、低温氮气吸附-脱附、扫描电镜(SEM)、傅里叶变换红外(FTIR)光谱等手段对所得样品进行了表征.加入扩孔剂可以明显增大介孔材料的孔容和孔径,而异辛烷为扩孔剂的扩孔效果明显优于四氯化碳.经四乙烯五胺(TEPA)镀饰后,这些样品均表现出良好的CO2吸附性能.其中对于除去模板剂后再镀胺的样品,其CO2吸附能力与介孔材料孔道结构关系不大,而对于未除模板剂的原粉镀胺样品,CO2吸附能力则随孔道的变大而增强.此外,通过吸附等温线和CO2-程序升温脱附(TPD)手段比较了温度和压力对CO2吸附的影响,发现在较高温度下吸附时CO2的吸附能力随压力的变化存在显著差别,因而在这类TEPA修饰的介孔材料上可通过变压吸附的途径来实现对环境气流中CO2的吸附和分离.     

Investigation of confined ionic liquid in nanostructured materials by a combination of SANS, contrast-matching SANS, and nitrogen adsorption

Small-angle neutron scattering (SANS), contrast-matching SANS, and nitrogen adsorption have been utilized to investigate the confined ionic liquid (IL) [bmim][PF(6)] phase in ordered mesoporous silica MCM-41 and SBA-15. The results suggest that the pores of SBA-15 are completely filled with IL whereas a small fraction of the pore volume, the pore "core", of MCM-41 is empty. The contrast-matching SANS measurements confirm the enhanced solubility of water in IL. In addition, they provide strong evidence that water does not enter the empty pore core of MCM-41, possibly because of the preferred orientation of the IL molecules in the adsorbed layer.