具有三维贯通多级孔道结构大孔氧化铝的制备与表征

采用铝溶胶晶种引入、结合相分离的方法制备了具有三维贯通多级孔道结构的大孔氧化铝材料。采用扫描电镜（SEM）、X射线衍射（XRD）、N₂吸附-脱附、压汞、核磁共振波谱（NMR）等测试方法对所得材料进行了表征。结果表明,该氧化铝材料具有200-600 nm的均匀分布且贯通的连续大孔孔道,经550℃焙烧即可得到结晶态γ-氧化铝。大孔氧化铝比表面积达到366 m²/g,具有以5 nm及400 nm为中心的较为集中的介孔-大孔多级孔道分布。焙烧后的样品中,铝具有四、六两种配位状态。制备过程中,聚环氧乙烷（PEO）作为诱导剂引发固-液两相分离,形成具有三维贯通多级孔道结构大孔氧化铝,而凝胶中引入铝溶胶时,AlOOH晶粒与铝交联水合物均相伴生,在凝胶过程诱导铝交联水合物转变为AlOOH,最终使大孔氧化铝在较低的焙烧温度即可转化为γ-氧化铝。     

六棱柱状多晶γ-Al2O3的制备、表征及其形成机制研究

以AlCl₃·6H₂O为前驱物,在氨水介质中用水热法制备了具有新颖形貌特征的六棱柱状多晶γ-Al₂O₃颗粒。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)及N₂物理吸脱附等方法对所制备的γ-Al₂O₃颗粒进行了表征,并对其形貌形成机制进行了分析。结果表明,铝前驱物在氨水介质中通过水热处理后,经焙烧可以形成形貌规整的六棱柱状γ-Al₂O₃颗粒,其边长与长度分别约为0.3 μm和2.5 μm。TEM图片显示,六棱柱颗粒是由尺寸在10 nm左右的粒子聚集而成,因而具有多晶γ相特征。所制备的γ-Al₂O₃材料具有发达的孔隙结构,比表面积为274 cm²/g,孔容为0.51 cm³/g,孔径集中分布在5.5 nm周围。研究发现,γ-Al₂O₃六棱柱形貌的形成机制与AlOOH二次粒子在NH₄⁺正电荷作用下发生的最稳态排列形式具有密切的关联。     

乙二胺和聚乙二醇在纳米介孔氧化铝制备中的协同导向作用

以无机铝盐Al(NO₃)₃为原料, 以乙二胺和聚乙二醇为协同模板导向剂, 与氨水反应, 经过“沉淀-超声-煅烧”等过程, 制得介孔纳米氧化铝. 用TEM, XRD, N₂吸附-脱附等测试技术对样品进行了测试和表征. 研究结果表明, 所得样品具有相当高的比表面积(510 m²•g^－1)、较大孔容(1.13 cm³•g^－1)和较为集中的孔径(5.8 nm)分布. 根据乙二胺和氧化铝表面的溶液化学反应及在不同pH条件下的溶液组分分布, 探讨了它们在介孔氧化铝制备过程中的协同模板作用机理.     

高比表面积等级孔γ-Al2O3的金属醇酯一步水解法制备及性能

采用金属醇酯一步水解法, 在不同含水有机溶剂反应介质中在常温条件下制备了具有特殊形貌及等级孔道结构的超高比表面积γ-Al₂O₃材料. X射线衍射(XRD)、 N₂吸附-脱附、 扫描电子显微镜(SEM)和透射电子显微镜(TEM)等表征结果证明, 通过调节反应介质中水含量和溶剂类型可以精确控制仲丁醇铝的水解缩合反应过程和副产物醇分子的扩散行为, 进而优化产物的孔道结构. 研究结果表明, 在水/乙腈体系下制备的γ-Al₂O₃材料整体呈现出由大孔直孔道和三维介孔孔道构成的等级孔道结构, 且随着水含量的增加, 大孔孔壁依次出现光滑状、 片状和褶皱状的特定形貌; 在饱和水的丁醇溶液体系下制备的材料则展现出由厚度约为10 nm的片状γ-Al₂O₃堆积而成的三维介孔结构, 比表面积高达517 m ²/g. 选取水含量为3 mL的水/乙腈体系下的大孔-介孔γ-Al₂O₃材料作为载体制备负载型Pt基催化剂. 负载后载体等级孔结构基本保持完好, 金属Pt纳米颗粒均匀分散在载体上, 该催化剂在渣油脱金属催化反应中的脱金属性能比商用薄水铝石为载体制备Pt基催化剂更加优异. 脱Ni率和脱V率分别提高11.62%和10.83%.     

三维贯通大孔Al_2O_3载体及其渣油加氢脱金属催化性能

采用相分离技术制备了具有三维贯通大孔结构的Al_2O_3载体,载体的大孔尺寸为250 nm,比表面积174 m~2/g,具有21 nm及250 nm集中的双重孔分布,抗压强度达到16.5 N/mm。采用该载体制备的渣油加氢脱金属催化剂仍然保持与载体接近的双峰孔分布、三维贯通大孔结构及较大的抗压强度等特性,Ni、Mo金属组分在载体表面分散均匀。催化剂的片层状活性相的长度为3-10 nm,堆垛层数1-7层,其中,大于4层的活性相分布约占40%,形成非均匀形态的活性相结构。与现有工业催化剂相比,三维贯通大孔渣油加氢脱金属催化剂的脱金属率、脱硫率及脱残炭率分别提高6.2%、6.0%及6.8%,孔结构、表面性质、活性相结构及其协同作用是三维贯通大孔催化剂具有优异催化性能的主要原因。     

RbCl和CsCl水溶液结构的X射线散射及经验势结构精修模拟

采用X射线散射法研究了RbCl和CsCl水溶液的结构,利用基于经验势的结构精修(EPSR)方法获得了溶液中的水合Cl^-、Rb⁺、Cs⁺、离子缔合及本体水的对径向分布函数、配位数分布及空间密度分布(3D结构)等结构信息。在水溶液中,Cl^-具有相对稳定的6水合结构,其水合距离为0.321 nm,外加阳离子对其水合作用的影响不明显。7.3 ± 1.4个水分子与Rb⁺水合,其特征水合距离为0.297 nm,8.4 ± 1.6个水分子与Cs⁺水合其水合距离为0.312 nm。Cs⁺不具有第二水合层,而Rb⁺表现出了更强的水合能力,具有较明显的第二水合层。Cl^-、Rb⁺及Cs⁺常被认为是“结构破坏”型离子。从微观角度来看这种所谓的“结构破坏”主要体现在破坏了本体水分子的第二水合层保持四面体构型的趋势。RbCl和CsCl水溶液中部分存在着Rb-Cl和Cs-Cl直接接触离子对,在1.0 mol·dm^-3的溶液中Rb-Cl及Cs-Cl的特征距离分别为0.324和0.336 nm,溶剂分割离子对的距离则都在0.6 nm左右。相对于Cs⁺,Rb⁺与Cl^-离子之间表现出了更强的缔合能力。     

载体焙烧温度对Rh-Mn-Li/SBA-15催化CO加氢性能的影响

SBA-15分别于550、700、800和900℃进行焙烧,然后以等体积共浸渍法将Rh、Mn和Li负载其上。催化剂的性能用CO加氢反应进行评价。催化剂分别用N₂物理吸附、X射线衍射、透射电子显微镜、H₂化学吸附和傅里叶变换红外光谱进行表征。即使在900℃下进行焙烧,SBA-15的结构仍得到保持。但是,当焙烧温度从550℃升高到900℃,SBA-15的比表面积、孔径和总孔容分别从842.6 m²·g^-1、9.57 nm和1.18 cm³·g^-1降到246.4 m²·g^-1、5.62 nm和0.34 cm³·g^-1。此外,Rh颗粒的尺寸都在1.5-4.0 nm范围内,并且随着载体的焙烧温度增加而增加。另外,Rh颗粒更倾向位于高温焙烧载体的介孔内,这可能是因为经过高温焙烧,载体微孔下降。所以,H₂和CO更易与负载在高温焙烧后的载体上的Rh颗粒接触。因此,当载体焙烧温度达到900℃时,Rh-Mn-Li/SBA-15催化剂有非常高的C₂₊含氧化合物的活性和选择性。     

Sn、Ti掺杂改性γ-Fe2O3催化剂结构及NH3-SCR脱硝活性研究

采用共沉淀-微波热解法,制备一系列Sn、Ti掺杂改性γ-Fe₂O₃催化剂样品(γ-Fe_0.95Ti_0.05O_z、γ-Fe_0.95Sn_0.05O_z、γ-Fe_0.95Sn_0.025Ti_0.025O_z),研究Sn、Ti掺杂对γ-Fe₂O₃催化剂SCR脱硝活性的影响,借助XRD、N₂吸附-脱附、EDS及SEM等手段对催化剂晶相、孔结构、表面元素及微观形貌等进行表征分析。结果表明,Sn、Ti掺杂后以无定形态高度分散于γ-Fe₂O₃晶格中,与Fe形成固溶体;单一助剂Ti掺杂制得的γ-Fe_0.95Ti_0.05O_z 最高脱硝效率达98.3%,且在250~400 ℃脱硝效率保持90%以上;Ti掺杂可以细化γ-Fe₂O₃晶粒,优化2~100 nm孔径孔隙结构,抑制α-Fe₂O₃的生成,促使γ-Fe₂O₃形成细致、均匀、独立的球状颗粒,对SCR反应有利;Sn掺杂则使催化剂出现严重烧结现象,导致2~6 nm孔径孔结构贫乏,对SCR脱硝反应不利;在Sn、Ti协同作用下,催化剂表面氧铁原子物质的量比由1.83降至1.33,表面晶格氧显著下降,一定程度上限制了SCR反应速率的提高。     

二次纳米自组装大孔氧化铝贯穿孔道的NSA形成机理

采用纳米自组装法合成的大孔氧化铝催化材料FA-06,具有1.39 mL·g^-1的孔容、297 m²·g^-1的比表面积、32.4 nm的最可几孔径和81.85%的孔隙率,孔道集中分布于10~30 nm和30~60 nm的比例分别占35.61%和40.88%。GPC结果表明,对于形成反相超增溶胶束的高聚物RHP,可通过改变聚异丁烯马来酸酐(PIBSA)的量来控制其分散度和相对分子量,进而控制大孔氧化铝的孔道结构。TEM及SEM结果表明,纳米自组装氢氧化铝棒长600~800 nm,直径为250~300 nm,经550.0℃焙烧后,形成直径为150~300 nm,长度为400~600 nm的纳米氧化铝棒。从焙烧后的纳米自组装氢氧化铝的XRD结果证明了3种γ-Al₂O₃的前躯体完全转化为γ-Al₂O₃。结合TG的结果,表明在605.0℃时,拟薄水铝石完全转化为γ-Al₂O₃,总失重可达61.88%。基于以上实验结果,模拟了反向超增溶胶束、氢氧化铝及大孔氧化铝的分子自组装和纳米自组装的形成过程,并提出了纳米自组装大孔氧化铝贯穿孔道的NSA(Nano Self-Assembly)形成机理。     

NaY分子筛的改性及吸附脱氮性能

采用离子交换法用NH⁺₄、Zn²⁺、Cu²⁺、Cr³⁺阳离子改性NaY分子筛,并利用XRD、FT-IR和低温N₂吸附-脱附等方法对改性的分子筛进行了表征。XRD 和FT-IR表征结果表明,改性后的分子筛骨架完好。Cr改性Y分子筛(CrY)的比表面积、孔体积及平均孔径均较小,但存在部分介孔。研究了改性分子筛对含喹啉模拟燃料的吸附脱氮,喹啉分子尺寸的模拟结果为0.711 6 nm×0.500 2 nm,说明其并不易进入Y型分子筛0.74 nm的微孔。吸附脱氮结果表明,CrY的脱氮效果最好,CuY和ZnY次之,NH₄Y效果最差,改性分子筛的吸附脱氮性能与金属离子的价态有关,同价金属离子改性后的分子筛,吸附时间对其影响趋势相同,且金属离子价态越高,改性分子筛的吸附脱氮性能越好。吸附温度对CrY和NH₄Y分子筛吸附脱除喹啉的影响不大,可在室温下使用,但高温有利于CuY和ZnY吸附脱氮。XRD表征结果表明,焙烧后CrY分子筛骨架已完全塌陷失去了绝大部分吸附脱氮性能。     

Hydrothermally stable silica–alumina composite membranes for hydrogen separation

A thin layer (30–40 nm) of a dual-element silica–alumina composition was deposited on a porous alumina support by chemical vapor deposition (CVD) in an inert atmosphere at high temperature. Prior to CVD, an intermediate layer of γ-alumina was coated on the macroporous alumina support. The intermediate layer was prepared by the dip-coating and calcination of boehmite sols of different sizes to give a graded structure that was substantially free of defects. The resulting supported composite membrane had high permeance for hydrogen in the order of 2–3 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 873 K with selectivities of H₂ over CH₄, CO and CO₂ of 940, 700 and 590, respectively. The membrane operated by a hopping mechanism involving jumps of permeating molecules between solubility sites. The presence of aluminum improved the hydrothermal stability of the membranes for periods in excess of 500 h at 873 K in 16% steam, allowing the permeance to remain above 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹, although with decreased selectivities.     

Effects of calcination temperature on the pore size and wall crystalline structure of mesoporous alumina

In this paper, mesoporous alumina with different pore sizes and wall crystalline structures was synthesized at calcination temperatures over 550 degrees C. The characterization of the samples calcined at 550, 800, 1100, and 1300 degrees C, respectively, was performed using TEM, XRD, FTIR, TG/DTA, and N2 adsorption/desorption techniques. The correlation between pore size and wall crystalline structure on calcination temperature was systematically investigated.     

大孔吸附树脂对肿瘤坏死因子吸附性能的研究

选用NK-110、碳化树脂和MET-10043种大孔吸附树脂,通过对树脂吸附量的测定,吸附动力学曲线和吸附等温线的描述等方法,研究了3种大孔吸附树脂对血浆中TNFα的吸附性能,结果表明NK-110和MET-1004对TNFα的吸附量较高,其中又以MET-1004的吸附速率最快     

Morphology Control and Catalytic Dehydrogenation Performance of Zeolitic Imidazolate Frameworks-8北大核心CSCD

Zeolitic imidazolate frameworks-8（ZIF-8）is a kind of porous material with large specific surface area and strong stability,which is widely used in gas storage,separation,catalysis and other fields. In this work,the effect of different reaction conditions,such as the molar ratio of Zn2+ to 2-methylimidazole,the amount of surfactant and the reaction solvents,on the size and morphology of ZIF-8 were reported. Among these conditions,the molar ratio of Zn2+ to 2-methylimidazole is the key factor affecting the size and morphology of ZIF-8. The synthesized ZIF-8 nanoparticles were characterized by SEM,BET and XRD. The size of ZIF-8 decreases gradually from 1500 nm to 850 nm then to 250 nm,and the morphology changes from truncated hexahedron to truncated dodecahedron and finally to dodecahedron. The specific surface area of ZIF-8 nanoparticles with a particle size of 250 nm is 1730 m2/g,and the pore size and pore volume are 1. 5 nm and 0. 6 cm3/g,respectively. Therefore,it can be seen that ZIF-8 nanoparticles with a particle size of 250 nm have excellent carrier characteristics. The impregnation method was further adopted to synthesize the supported catalyst,and boron ammonia was used as the reducing agent. The ZIF-8（250 nm）nanoparticles were loaded with metals/precious metal nanoparticles in situ,the component optimization and catalytic performance were further studied. The obtained catalyst ZIF-8/Pt0. 002@Ni0. 2 shows excellent performance in hydrogen generation from aminoborane. © 2022, Science Press (China). All rights reserved.     

Synthesis of γ-Al2O3 with High Surface Area and Large Pore Volume by Reverse Precipitation-azeotropic Distillation Method

γ-Al₂O₃ with high surface area and large pore volume combined with high thermal stability was synthesized by a reverse precipitation-azeotropic distillation method. The effects of azeotropic distillation on the characteristics of γ-Al₂O₃ were studied by means of X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, transmission electron microscopy(TEM) and N₂ adsorption-desorption. The results show that γ-Al₂O₃ dried by azeotropic distillation has excellent structure characteristics with a high surface area of 426 m²/g and a large pore volume of 2.56 cm³/g. After calcination at 1100℃, the surface area of γ-Al₂O₃ was still 92 m²/g with a large pore volume of 1.00 cm³/g, indicating the potential application in catalyst and petroleum industry.     

Facile synthesis of mesoporous WO3@graphene aerogel nanocomposites for low-temperature acetone sensing

Ordered mesoporous tungsten oxide@graphene aerogel (mWO3@GA) nanocomposites were synthesized via an interface-induced co-assembly process, which show a high selectivity and great response to acetone at low temperature.     

Preparation of Ultrafine Ceramic Powder Used for Making PTCR Ceramics by Sol-gel Method

Amorphous gel powder containing Ba, Sr, Ca, Ti, Si, Mn, Li and Y elements has been prepared by a modified sol-gel method, the ultrafine PTCR (Positive Temperature Coefficient of Resistance) powder was obtained through calcination for 2 h at 800℃ in air. According to XRD, DSC, BET and SEM. it can be concluded that it's crystal structure is cubical perovskite phase at room temperature, it's average crystallite size is about 28.4nm (using the Debye-Scherrer formula) or about 40 nm (using BET) or about 50nm(using SEM), it's specific surface area is 24.80 m²/g, and which is two twice as much as that of the sample prepared by old sol-gel method^[l,2], it's particle size displays normal distribution with average particle size of 437.2nm.