复合模板剂下有序介孔TiO2的制备研究

在复合模板剂聚氧乙烯十二烷基醚(Brij35）和聚乙二醇（PEG)下，制备出有序介孔TiO2.用XRD、HRTEM、SEM、FT-IR和N2吸附脱附等方法进行表征；并通过对反应过程中电导率和粘度的连续监测，分析有序介孔TiO2形成过程.研究表明,介孔TiO2为规整的六方排列结构，在低于400 ℃焙烧，有序结构稳定性高，比表面积达252 m2•g－1，孔径3.4 nm，晶型为锐钛矿；经500 ℃焙烧，有序介孔结构破坏，并开始出现金红石型晶相.有序介孔TiO2形成过程是基于在高极性介质中非极性的碳氢链聚集成为胶束，同时钛酸丁酯（TBOT）在已形成的胶束上聚集，在酸作用下不断水解缩聚而形成有序介孔结构，有效控制水解和聚合过程是控制介孔材料结构形成的关键.     

萃取法脱除介孔磷酸镍模板剂的研究

采用溶胶-凝胶法, 以十六烷基三甲基溴化铵(CTAB)为模板剂合成了介孔磷酸镍NiPO-1和NiPO-2, 并采用溶剂萃取法进行了模板剂的脱除. 采用XRD, IR, CHN元素分析以及N₂吸附等手段研究了不同萃取剂体系、温度、萃取剂浓度及萃取次数对介孔磷酸镍(NiPOs)骨架结构和模板剂脱除率的影响. 结果表明: 在0.1 mol/L CH₃COONa/EtOH为萃取剂, 78 ℃下交换4次, 每次1 h 条件下, NiPO-1和NiPO-2中模板剂的去除率均超过97%. 萃取后介孔材料保持了较好的完整性和有序度. 萃取后样品的衍射峰强度增大, 主衍射峰d₁₀₀值亦增大主要是由于萃取过程中, 在较高的温度下NiPOs的纳米管簇结构在萃取剂中有溶胀作用|氮气吸附表明萃取后NiPO-1和NiPO-2的比表面可分别达309.5 m²•g^－1和263.9 m²•g^－1.     

复合模板制备介孔SiO2及对苯酚吸附研究

介孔SiO2是一种轻质纳米非晶固体材料,因具有比表面积大、密度小等特性,而被用作催化剂载体、高效绝热材料、气体过滤材料和高档填料等,尤其是单分散介孔SiO2在高科技领域和科学研究中有着非常重要的作用[1].目前制备介孔SiO2的方法很多,气相法、化学腐蚀法、沉淀法、微乳法、溶胶-凝胶法和水热法等[2-4].与传统的方法相比,水热法具有实验装置简单、操作容易、粒径可控、粒子分散性好等特点,是制备单分散介孔SiO2 的有效方法之一,而被广泛应用[5-7].     

模板法制备介孔材料的研究进展

从微孔到中孔或介孔材料的制备过程中．离子模板、乳液模板、液晶模板及至细菌模板得到广泛的应用．具有空间规整性的介孔材料就其介观结构所具有的空间群而言，有P6mm，P6 3／mmc，Pm3n，Ia3d；就其介观结构的形态而言．有二维六方，三维六方，双连续立方，La层状相，多层囊泡等．本文对MCM系列，SBA-n系列、MSU系列，以及那些较为单一的硅基品种FMS-16、HMS等的制备体系及其特点进行了综述．对介孔分子筛合成中常用的表面活性剂分子类型进行了归纳．本文针对的是单一表面活性剂作模板的类型，对那些混合型模板则未予详细介绍．     

原位合成的活性脲醛树脂作为模板剂制备二氧化硅介孔材料

利用酸性条件下正硅酸乙酯的水解和脲醛树脂的聚合反应同时一步原位进行的方法合成了二氧化硅复合粉体(包括核壳微球结构和网状结构)和块体凝胶材料. 液氮吸附BET分析结果证明复合材料焙烧后得到的二氧化硅孔径分布均匀, 大小在介孔范围内. 改变反应性单体尿素. 甲醛及正硅酸乙酯等的初始浓度可对二氧化硅块体材料的孔径大小进行调节. 扫描电子显微镜观测结果显示, 随着原料单体初始浓度的变化复合粉体材料的微米级形貌可以是多孔网状结构或核壳结构. 从红外光谱和差热分析的结果推测, 高甲醛/尿素摩尔比[n(甲醛)∶n(尿素)≥2]条件下形成的支链脲醛树脂可作为块体二氧化硅理想的孔结构导向剂.     

非表面活性剂合成CeO2介孔材料

以非表面活性剂三乙胺(TEA)和聚乙二醇(PEG)为模板剂,合成了具有立方莹石晶相结构的介孔CeO2材料,通过XRD,HRTEM,BET,FTIR和选区电子衍射(SAED)等手段对介孔CeO2进行了表征。考察了模板剂在CeO2介孔结构的形成过程中所起的作用及其对比表面、孔径分布、热稳定性的影响,并对模板剂的作用机制进行了分析。结果表明,三乙胺在CeO2介孔结构的形成中起关键作用,聚乙二醇对介孔结构热稳定性有明显的改善作用,经600℃焙烧3h的样品仍能保持较好的介孔结构,其介孔呈直通型的六方型孔道,比表面积>200m2·g-1,孔分布呈双孔型分布,其中介孔孔径约为5nm左右,微孔孔径在1～2nm之间,介孔占较大比例,并且微孔数量随焙烧温度的升高逐渐减少,直至600℃消失。     

以葡萄糖、丙烯酰胺和硝酸铈铵为原料制备介孔CeO_2

以葡萄糖、丙烯酰胺和硝酸铈铵为原料, 采用水热法制备出大比表面的介孔CeO2. 研究了铈离子价态、原料组成、 水热处理温度和时间以及原料的加入方式等条件对样品性能的影响, 并运用XRD, FT-IR, N2吸脱附和TG-DTG等手段对样品进行了表征. 结果表明, 铈离子价态由三价到四价可使介孔CeO2的比表面有较大的增加. 单独采用葡萄糖(或丙烯酰胺)和硝酸铈铵为原料所制样品的比表面较小, 而当原料组成为葡萄糖、丙烯酰胺和硝酸铈铵时可制得比表面较大的介孔CeO2, 水热处理时间和原料的加入方式对介孔CeO2的性能有一定的影响, 150 ℃水热处理2 d可获得比表面为162 m2 · g-1 的介孔CeO2.     

电解质诱导聚集初级粒子制备介孔SiO_2材料

在无模板剂的条件下,通过在Stber合成过程中引入外加电解质成功地制备了具有介孔结构的SiO2粒子.实验结果表明,通过电解质的加入可以诱导Stber过程中初级SiO2粒子的聚集,从而得到了具有介孔结构和较强表面吸附能力的SiO2粒子.     

介孔TiO2的水热法制备及其光催化性能

以二钛酸钾(K2Ti2O5)经离子交换得到的无定形水合二钛酸(H2Ti2O5·xH2O)为原料,与葡萄糖溶液在220℃下进行水热反应,再在空气中520℃焙烧,制备出介孔TiO2.用扫描电子显微镜(SEM)、X射线衍射(XRD)、N2吸附、透射电子显微镜(TEM)等技术对样品进行了表征.结果表明,该介孔TiO2具有微米级棒状或针状形貌,晶粒大小为12.3 nm,比表面积为106 m2·g-1,孔容为0.31 cm3·g-1,孔径为8.06 nm,焙烧处理后晶型仍是锐钛矿相.水热生成的碳抑制了晶粒的团聚生长和晶型的转变,提高了介孔TiO2的热稳定性.甲基橙降解实验评价了介孔TiO2的光催化性能,结果发现其活性与商用TiO2催化剂P25相当,而其较大的粒径更容易回收再利用.以碘化钾为探针反应,表明介孔TiO2的光催化机制以光生空穴氧化为主.     

纳米TiO2-SnO2介孔材料的制备及其对含氰废水的光催化降解性能

以TiCl4和SnCl4为原料,采用直接水解常压液相反应合成出了纳米TiO2-SnO2复合介孔材料.利用XRD和TEM及漫反射谱等对样品进行了表征,并研究了纳米TiO2-SnO2复合介孔材料对含氰废水的光催化降解性能.结果表明,纳米TiO2与SnO2复合后,导致材料的光谱响应拓宽;此种催化剂在日光灯下比在紫外灯下对废水中CN-的降解效果要好.     

Synthesis and photocatalytic activity of co-doped mesoporous TiO2 on Brij98/CTAB composite surfactant template

Using composite surfactant templates, polyoxyethylene (20) oleyl ether (Brij98) and cetyl trimethyl ammonium bromide (CTAB), as structure-directing agents, N and La co-doped mesoporous TiO₂ complex photocatalysts were synthesized successfully. The micromorphology of co-doped mesoporous TiO₂ samples was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR), energy-dispersive X-ray spectrometer (EDS) and N₂ adsorption-desorption measurements. The results indicated that the complex photocatalyst prepared with a molar ratio of Brij98:CTAB=1:1 showed a uniform pore size of ca. 7 nm and a high specific surface area (S_BET) of 279.0 m² g⁻¹, and exhibited the highest photocatalytic activity for degradation of papermaking wastewater under ultra-violet light irradiation. The chemical oxygen demand (CODc_r) percent degradation was about 73% in 12 h and chroma percent degradation was 100% in 8 h.     

炭化温度对模板法合成介孔炭性能的影响

以蔗糖为炭源和硅酸钠为硅源,采用原位共聚法制备了炭/氧化硅复合体,除去氧化硅得到介孔炭材料.采用N2吸附-脱附、透射电子显微镜和红外光谱对不同炭化温度获得的样品进行表征.结果表明,随着炭化温度升高,所得的介孔炭比表面积和孔容均下降,650℃ ～ 950℃的炭化温度下获得的样品BET比表面积在586m2/g ～728 m2/g之间,孔容在0.549cm3/g～0.696cm3/g之间,孔径分布5-15nm之间.经红外光谱检测所得的介孔炭样品均含有氢和氧的功能团.     

有序中孔炭的制备及电性能研究

采用微湿含浸法制备了一系列具有不同比表面积和孔径分布的超级电容器有序中孔炭材料,同时采用Al-SBA-15为模板剂制得具有六方排列的空心炭管CMK-5.所制得的有序中孔炭的BET比表面积随糠醇加入量的增加而减小.电化学性能测试结果表明,在1mA·cm-2的充放电电流密度下各中孔炭材料比电容的大小顺序与其BET比表面积的大小顺序相一致.在所有样品中AlSC-0.8由于具有最大的比表面积,因此其比电容最大,达87.8F·g-1.倍率性能测试结果表明,具有CMK-3结构的SC-2.0的倍率性能最好,在50mA·cm-2的放电电流密度下其放电比电容接近AlSC-0.8有序中孔炭的水平.     

Effect of the conditions of the matrix carbonization of sucrose on the structure and adsorption properties of mesoporous carbon materials

A study was carried out on the effect of the conditions of the matrix carbonization of sucrose in MCM-48 and SBA-15 silica mesoporous molecular sieves on the structure and adsorption properties of the resultant CMK-1 and CMK-3 mesoporous carbon molecular sieves. CMK-3 was found to be a structurally similar replica of SBA-15. An exact replica is not formed in the case of MCM-48. This failure is attributed to considerable deformation of the matrix during the carbonization process due to the bicontinuous pore system and thinner framework walls. This is probably related to transformation of the carbon material into a low symmetry product upon detemplating of the C/MCM-48 composite (dissolution of the silica). Mesoporous carbon materials were obtained with good adsorption structure features. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 365–370, November–December, 2008.     

A novel green template for the synthesis of mesoporous silica

Mesoporous pure silicas and functionalized silica with a narrow pore size distribution centered at 3.8 nm were prepared by a novel template, amphiphilic dendritic polyglycerol. The resulting silica materials were characterized by electron microscopy; nitrogen adsorption; (1)H, (13)C, and (29)Si solid-state cross-polarization magic-angle spinning NMR spectroscopy. It was shown that the template could be completely removed from the pure and functionalized silica in an environmentally friendly way by means of a simple water extraction procedure. Furthermore, it was shown that these materials could be easily functionalized, for example, by employing aminopropyl groups. Thus, a new environmentally friendly pathway to this fascinating class of silica material has been opened.     

以伯胺为模板剂合成含铁介孔分子筛FeHMS

以非离子型表面活性剂伯胺为模板剂合成了含铁介孔分子筛FeHMS,并对其结构和形态进行了表征。发现FeHMS的颗粒比SiHMS小,粒子表面更为光滑。除了2.5nm的介孔外,FeHMS还原10nm左右的孔。FeHMS介孔分子筛在脱除模板剂之前,铁主要处于四面体配位状态的骨架位,经焙烧脱除模板剂之后,部分铁由骨架位迁移到孔壁表面。用酸化的乙醇溶液抽提脱除模板剂,能更有效地让铁保留在四面体配位状态的骨架位上。高温脱除模板剂后,孔壁表面的铁物种处于一种高分散的状态。此外还研究了HMS类介孔分子筛材料的水热稳定性,发现铁的引入可改善介孔分子筛材料的水热稳定性。     

Structural and catalytic properties of lanthanide (La, Eu, Gd) doped ceria

Ce_0.9M_0.1O_2−δ mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO₂ (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F_2g Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce⁴⁺/Ce³⁺. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO₂, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area.     

Field of concentrations and conditions of template structure formation of a silica mesoporous molecular sieves of MCM-48 type

The region of composition and concentration of the reaction mixtures for template structure formation of silica mesomorphous molecular sieves of the MCM-48 type have been determined, the boundary concentrations of the reagents have been determined, and also the effects of synthesis conditions (in particular the ratio of the template and the skeleton-forming elements and the temperature factor) on the structure transformation in the CTAB-TEOS-NaOH-H₂O system. Reproducible methods have been developed for the synthesis of highly ordered MCM-48 with minimization of the amount of surfactant and without the use of additional organic substances. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 186–190, May–June, 2008.     

New method to synthesize mesoporous titania by photodegradation of surfactant template

Mesoporous titania has been successfully synthesized by photodegradation removal of cetyltrimethylammonium bromide as the surfactant, after slow hydrolyzation of titanium(IV) isopropoxide. Fourier transform infrared spectra proved that photodegradation has successfully decreased the peak areas of the alkyl groups from the template. The nitrogen adsorption analysis showed that the pore size and the specific surface area of the mesoporous titania were 3.7 nm and 203 m² g⁻¹, respectively, proving the mesoporosity of the titania obtained with the existence of the interparticle mesoporosity which was confirmed by transmission electron microscopy. Based on X-ray diffraction results, the mesoporous titania obtained was in the form of crystalline anatase phase. Furthermore, results from the diffuse reflectance ultra violet-visible spectra showed that the composition of tetrahedral titanium(IV) was more than the octahedral titanium(IV). When the mesoporous titania obtained was used as a catalyst in the oxidation of styrene, an improvement in the conversion of styrene (38%) was observed when compared to those obtained using Degussa P25 TiO₂ (14%) as the catalyst.     

Preparation of mesoporous aluminophosphate using poly(amido amine) as template

Mesoporous aluminophosphate was prepared by using G4.0 poly(amido amine)dendrimer as a template and characterized by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ adsorption/desorption methods. Results show that the title compound exhibits a typical mesoporous structure with the average pore size from 5 to 8 nm. The formation mechanism of the nanoporous structure using dendrimer as a template was also discussed. __________ Translated from Journal of Fujian Normal University (Natural Science Edition), 2007, 23(2): 67–70 [译自: 福建师范大学学报 (自然科学版)]