用水热法在铁铬铝合金片上原位合成MCM-22沸石膜

 采用水热法在铁铬铝合金片载体上原位合成了MCM-22沸石膜,并采用X射线衍射和扫描电子显微镜对沸石膜进行了表征,探讨了成膜的影响因素. 结果表明,载体预处理条件对合成沸石膜的品质有较大的影响. 载体仅经碱处理后合成的沸石膜稀疏而不连续; 载体先经碱处理再经酸处理后可得到连续致密的沸石膜,且晶片取向均一; 载体预先涂覆Al2O3胶过渡层后制得的MCM-22沸石膜经超声波清洗后不会脱落,表明沸石膜与载体间的结合力增强. 此外,增大晶化母液量有利于沸石膜的生长.     

A novel method for synthesis of mesoporous ZSM-5 from iron ore tailings

Mesoporous ZSM-5 was prepared from iron ore tailings (IOT) using a two-step process. Mesoporous MCM-41 was first synthesized using cetyltrimethylammonium bromide (CTAB) as mesoporous template and IOT as silica source. The CTAB in the as-synthesized MCM-41 was used as the mesoporogen to produce the mesoporous ZSM-5, by recrystallizing the amorphous walls of MCM-41 with tetrapropylammonium bromide (TPABr) as the structure-directing agent via solid-phase conversion. To evaluate the textural properties of mesoporous ZSM-5, the as-synthesized samples were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, ²⁹Si, ²⁷Al magic angle spinning nuclear magnetic resonance spectroscopy, and nitrogen adsorption. The results show that phase separation between the surfactant and zeolite crystals was avoided in the solid-phase conversion process, which transforms the as-synthesized MCM-41 to mesoporous zeolite. Therefore, the synthetic route presented herein provides a novel method for the synthesis of mesoporous ZSM-5 from IOT.

     

Delamination of layered zeolite precursors under mild conditions: synthesis of UCB-1 via fluoride/chloride anion-promoted exfoliation

New material UCB-1 is synthesized via the delamination of zeolite precursor MCM-22 (P) at pH 9 using an aqueous solution of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride at 353 K. Characterization by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption at 77 K indicates the same degree of delamination in UCB-1 as previously reported for delaminated zeolite precursors, which require a pH of greater than 13.5 and sonication in order to achieve exfoliation. UCB-1 consists of a high degree of structural integrity via (29)Si MAS NMR and Fourier transform infrared spectroscopies, and no detectable formation of amorphous silica phase via transmission electron microscopy. Porosimetry measurements demonstrate a lack of hysteresis in the N(2) adsorption/desorption isotherms and macroporosity in UCB-1. The new method is generalizable to a variety of Si:Al ratios and leads to delaminated zeolite precursor materials lacking amorphization.     

噻吩分子及其与异辛烷二元混合物在MCM-22分子筛中吸附的蒙特卡罗模拟

应用巨正则蒙特卡罗模拟方法研究了噻吩分子以及噻吩与异辛烷混合物在MCM-22分子筛中的吸附和分布. 通过模拟获得了噻吩分子在MCM-22分子筛中不同温度(298、363 和393 K)下的吸附等温线和等量吸附热, 以及298 K时噻吩和异辛烷分子二元混合物在MCM-22分子筛中的吸附及分布情况. 结果表明, 吸附温度和吸附压力对噻吩分子在MCM-22分子筛吸附都有影响, 但等量吸附热受温度和吸附量影响较小. 对于二元混合物的吸附, 噻吩和异辛烷在分子筛中存在竞争吸附过程, 噻吩能够大量吸附在MCM-22分子的十元环和超笼中, 而异辛烷主要吸附在MCM-22分子筛的超笼系统, 从而可以将噻吩分子与异辛烷分子分离开来.     

硅源对MCM-22分子筛合成及物化性质的影响

在动态水热条件下,研究了硅溶胶、白炭黑、硅酸及硅胶为硅源时对MCM-22分子筛合成及物化性质的影响。以硅溶胶、白炭黑、硅酸三种硅源均可合成出高结晶度且无杂晶的片状MCM-22分子筛,其平均粒径分别为190、220和750 nm。硅源影响分子筛的聚集形态,三种硅源分别形成晶粒分散、晶粒半分散及晶粒聚集形态。三组样品的酸强度分布基本一致,都具有较多的中强酸分布,由硅溶胶和硅酸所得MCM-22分子筛在中强酸范围具有更高的B/L酸比值,以白炭黑合成的分子筛总酸量最高。NMR结果表明,样品中的铝以骨架铝为主,不存在明显的非骨架铝。由于硅胶对合成体系中游离水的吸附作用,水热反应难以发生,不能得到MCM-22分子筛,硅胶作为分子筛合成硅源时需要选择合适的反应条件。     

Alkylation of benzene with propylene over MCM-36: A comparative study with MCM-22 zeolite synthesized from the same precursors

Pillared layered MCM-36 zeolite was prepared from MCM-22 precursor with polymeric silica as pillaring agent. Both MCM-36 and MCM-22 zeolites are very active for the alkylation of benzene with propylene, and MCM-36 shows higher selectivity to cumene compared with MCM-22 zeolite.     

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.     

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.     

MCM-36分子筛的合成及其苯与丙烯烷基化性能研究

分别从MCM-22和MCM-49前驱体出发合成了MCM-36分子筛, 在液-固固定床反应器上对MCM-36分子筛的苯与丙烯液相烷基化反应性能进行了评价. 由MCM-22前驱体出发合成的MCM-36(A) 结晶度良好, 比MCM-22具有更高比表面积和介孔孔容, 酸量明显下降. 由MCM-49前驱体出发合成的MCM-36(B)的比表面积和介孔孔容增加, 小角XRD特征衍射峰强度低于MCM-36(A), 与MCM-49相比酸量下降幅度较小. 在苯与丙烯液相烷基化反应中MCM-36(A)的活性与MCM-22相当, 丙烯的转化率大于99.5%, 异丙苯的选择性比MCM-22提高了7%. MCM-36(B)的反应活性高于MCM-36(A), 而异丙苯的选择性低于MCM-36(A). MCM-36分子筛上苯与丙烯液相烷基化反应活性的提高归因于有效酸性位的增加,异丙苯选择性的提高则主要归因于B酸量的降低.     

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.     

混合胺体系中 MCM-49/ZSM-35 复合分子筛的晶化过程

 采用 X 射线衍射、N2 吸附-脱附、扫描电镜和傅里叶变换红外光谱等技术, 研究了 MCM-49/ZSM-35 复合分子筛在 Na2O-SiO2-Al2O3-CHA (环己胺)-HMI (六亚甲基亚胺)-H2O 合成体系中, 先在低温 80 ?C 老化 4 h, 再经 160 ?C 晶化不同时间的演变过程. 结果表明, 在该混合胺体系中, 首先生成 MCM-49 分子筛, 随着晶化时间的延长, 形成 ZSM-35 含量逐渐增加的 MCM-49/ZSM-35 复合分子筛, 最后生成纯 ZSM-35 分子筛; ZSM-35 的生成是以 MCM-49 分子筛的消耗为代价的.     

Physicochemical and catalytic properties of micro-mesoporous zeolite materials

Micro-mesoporous zeolite materials differing in their content of micro- and mesopores are obtained by the recrystallization of modernite zeolite. Using physicochemical methods such as scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction analysis, small-angle X-ray scattering analysis, low-temperature adsorption of nitrogen, temperature-programmed desorption of NH3, and IR spectroscopy, it is shown that recrystallization leads first to the formation of mesopores with sizes of 20–30 Å in zeolite crystals, then to the appearance of zeolite/MCM-41 nanocomposite, and finally to the complete conversion of zeolite into mesoporous MCM-41. During this process, the concentration of strong Brønsted acid sites accessible to pyridine bases first increases then drops. The catalytic properties of the synthesized materials are studied in the reaction of alkylation of benzene by dodecene-1. It is shown that the creation of transport pores and the increase in the accessibility of acid sites due to recrystallization under soft conditions facilitate the alkylation reaction.     

Bright photoluminescent hybrid mesostructured silica nanoparticles

Bright photoluminescent mesostructured silica nanoparticles were synthesized by the incorporation of fluorescent cyanine dyes into the channels of MCM-41 mesoporous silica. Cyanine molecules were introduced into MCM-41 nanoparticles by physical adsorption and covalent grafting. Several photoluminescent nanoparticles with different organic loadings have been synthesized and characterized by X-ray powder diffraction, high resolution transmission electron microscopy and nitrogen physisorption porosimetry. A detailed photoluminescence study with the analysis of fluorescence lifetimes was carried out to elucidate the cyanine molecules distribution within the pores of MCM-41 nanoparticles and the influence of the encapsulation on the photoemission properties of the guests. The results show that highly stable photoluminescent hybrid materials with interesting potential applications as photoluminescent probes for diagnostics and imaging can be prepared by both methods.     

微介孔复合分子筛合成及其在汽车冷启动尾气控制中的应用

分别采用稀溶液和浓溶液双模板剂两步水热合成法,以二氧化硅微硅粉和铝酸钠为硅源和铝源,第一步获得β分子筛晶种,第二步以β分子筛晶种为结构单元组装形成兼具MCM-41分子筛和β分子筛结构特点的复合型分子筛β/M(其中β是指β分子筛,M是指MCM-41介孔分子筛).采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、氮气吸附(BET)和高分辨透射电镜(HRTEM)对样品的物相结构和微观形貌进行了表征,并对复合分子筛的合成过程进行了分析.结果表明:复合分子筛β/M的形成是微孔β结构和介孔MCM-41结构的竞争生长过程,β分子筛晶种的晶化时间和晶粒度大小对β/M复合分子筛的结构有重要影响.此外,我们以甲苯为探针分子,比较研究了三类分子筛β/M、MCM-41和β的原样以及经高温水热处理后样品的吸附性能,结果表明:β/M复合分子筛的热稳定性优于介孔分子筛MCM-41,其甲苯吸附容量比MCM-41和β分子筛的高,其中以浓溶液法合成的复合分子筛吸附容量最高.     

Synthesis of ITQ-2 zeolite under static conditions and its properties

Zeolite ITQ-2 can be synthesized by swelling the layers of MCM-22 precursor. It has a single delami-nated structure of MWW with thickness of 2.5 nm. It shows disordered properties in long range and ordered in short range, which is a promising catalytic ma…     

Unburned carbon as a low-cost adsorbent for treatment of methylene blue-containing wastewater

Fly ash, natural zeolite, and unburned carbon separated from fly ash have been employed as low-cost adsorbents for dye adsorption in methylene blue-containing wastewater. It is found that the unburned carbon exhibits a much higher adsorption capacity than raw fly ash and natural zeolite. The adsorption capacities of fly ash, natural zeolite, and unburned carbon for methylene blue are 2 x 10(-5), 5 x 10(-5), and 2.5 x 10(-4) mol/g, respectively. Investigation also indicates that adsorption is influenced by initial dye concentration, particle size, dye solution pH, and adsorption temperature. Adsorption on unburned carbon increases with the initial dye concentration, solution pH, and temperature, but reduces with the increasing particle size. Kinetic studies show that adsorption of methylene blue on fly ash, natural zeolite, and unburned carbon can be best described by the pseudo-second-order adsorption model and that adsorption is a two-step diffusion process. The apparent activation energies for methylene blue adsorption on unburned carbon in the first and second diffusion processes are 12.4 and 39.3 kJ/mol, respectively.     

基于MCM-41分子筛表面的镱离子印迹聚合物的制备及其性能

运用离子印迹技术,以3-氯丙基三乙氧基硅烷为锚定剂,将功能单体直链聚乙烯亚胺(PEI)接枝在MCM-41分子筛表面,选择镱离子作为模板离子,以环氧氯丙烷交联制备出基于MCM-41表面的镱离子印迹聚合物Yb(Ⅲ)-IIP-PEI/MCM-41,并以同样的方法制备非离子印迹聚合物(NIP-PEI/MCM-41)。 利用傅里叶变换红外光谱仪和扫描电子显微镜等技术手段对Yb³⁺印迹聚合物进行表征,采用静态吸附法确定了Yb(Ⅲ)-IIP-PEI/MCM-41对Yb³⁺的最佳吸附条件及选择性吸附性能。 结果表明,Yb(Ⅲ)-IIP-PEI/MCM-41和NIP-PEI/MCM-41的最大吸附量分别为229.93和99.27 mg/g;印迹材料对Yb³⁺的吸附符合Langmuir模型;吸附平衡在40 min的时候基本可以达到,可以利用准二级动力学模型来描述其吸附过程;Yb(Ⅲ)-IIP-PEI/MCM-41对Yb³⁺具有较强的选择性,同时也具有很好的重复使用性能。 成功地将MCM-41和离子印迹聚合物的优点结合起来,制备出一种对稀土Yb离子既有高吸附量又有高选择性的吸附材料,为进一步将其应用在处理实际废水,分离回收低浓度稀土废水中的稀土元素等方面打下了基础。     

Modifying MCM-41 as an efficient nitrosamine trap in aqueous solution

The attempt of preparing efficient adsorbent to capture nitrosamines in aqueous solution is reported in this paper, in order to develop new mesoporous functional materials for environment protection. Adsorption of nitrosamines in an aqueous solution containing the tobacco-extract, by zeolite and mesoporous silica was investigated in detail. The influence of structural parameters such as pore size, Si/Al ratio and cation on the adsorption of zeolite was examined. Emphatically, two modification methods, one-pot synthesis and solid state grinding were employed to incorporate aluminum in mesoporous silica MCM-41 since MCM-41 possesses the suitable pore size for the trap of tobacco specific nitrosamines (TSNAs) in solution. The resulting composites were characterized by XRD, N₂ adsorption at 77 K, FTIR and NH₃-TPD to inspect their property and function. The impact of modifier amount and preparative method on the actual adsorption of the Al-containing composite was investigated.     

An investigation of the roles of surface aluminum and acid sites in the zeolite MCM-22

Ammonia adsorption studies reveal that the observed Lewis acidity in the zeolite MCM-22 is derived from at least two types of framework aluminum sites (AlF), that is, octahedral AlF and three-coordinate AlF. Comparative ammonia or trimethylphosphine (TMP) adsorption experiments with MCM-22 confirm that octahedral Al species gives rise to the signal at delta(iso) approximately 0 in the 27Al NMR spectrum; this is a superposition of two NMR signals from the different Al species on the water-reconstructed zeolite surface. A sharp resonance assigned to framework Al reversibly transforms on ammonia adsorption to delta(iso)27Al approximately 55 from tetrahedral AlF, while the broad peak is assigned to nonframework aluminum which results from hydrothermal treatment. This study also demonstrates the effectiveness of 27Al magic angle spinning (MAS) and multiple quantum (MQ) MAS NMR spectroscopy as a technique for the study of zeolite reactions.     

Preparation of biomass-derived phosphorus-doped microporous carbon material and its application in dye adsorption and CO2 capture

Microporous P-doped carbon materials are synthesized by a pyrolysis method using MCM-22 as a template, sucrose as a precursor, and phosphoric acid as phosphorus sources. The results show that the pore structure of the carbon materials can be adjusted by changing the amount of phosphoric acid and template. When the P/C molar ratio is 0.075, the obtained P-doped microporous carbon material shows excellent specific surface area up to 621 m²/g and shows a high adsorption capacity of 199.40 mg/g for crystal violet dye, with a removal rate of 98.9%. When testing the CO₂ adsorption capacity, it was found that the maximum adsorption capacity reached 63 mg/g and remained stable after 10 adsorption and desorption cycles, with excellent cycle stability. The adsorption obeys pseudo-second-order kinetic model, and the adsorption isotherm follows the Langmuir model.