金属改性硅基介孔材料及其加氢脱硫研究进展

硅基介孔材料具有孔径分布均一、孔道结构独特、比表面积高等优点,其在石油产品加氢脱硫(HDS)催化剂载体中的应用成为近年来研究的热点。但在实际应用过程中硅基介孔材料的耐硫性差、路径选择性低等局限性也逐渐显现出来,针对此类问题,近年来的研究集中在硅基材料的改性工作上。本文综述了近年来金属改性的硅基介孔材料应用于油品加氢脱硫的研究现状,重点讨论了铝、钛、锆等金属的引入对硅基介孔材料基本结构(比表面积、孔容和孔径)、酸性和HDS催化活性的影响。分析总结了经金属改性的硅基介孔材料作为HDS催化剂载体的优点和不足,并展望了其未来的应用前景。     

Direct imaging of surface topology and pore system of ordered mesoporous silica (MCM-41, SBA-15, and KIT-6) and nanocast metal oxides by high resolution scanning electron microscopy

We report here a detailed study on the surface topology of well-known ordered mesoporous silica (SBA-15, MCM-41, and KIT-6) and a series of nanocast Co 3O 4, Co 3O 4/CoFe 2O 4 composites by high resolution scanning electron microscopy (HR-SEM). Images of the MCM-41 structure were obtained at a resolution of the pore size, as well as a real space image of the gyroid silica surface of KIT-6 for two different aging temperatures, clearly revealing the differences of the aging procedures. By using the low voltage HR-SEM technique with extremely high resolution, we could very clearly show the influence of the template properties on the structure of the nanocast metal oxides.     

载体性质对Pd催化剂加氢脱硫性能的影响

以Si O2、全硅MCM-41(Si-MCM-41)、通过机械混合Si-MCM-41与ZSM-5得到的Z-MCM-41-M以及通过在ZSM-5外部包覆MCM-41制备得到的Z-MCM-41四种材料为载体,制备了四种负载型Pd催化剂。采用XRD、HRTEM、N2吸附-脱附、NH3-TPD手段对Pd催化剂进行了表征;以二苯并噻吩(DBT)为模型化合物,在固定床反应器上对四种催化剂的加氢脱硫(HDS)活性、加氢路径选择性和加氢裂化活性进行了考察,研究了不同类型载体对Pd催化剂加氢脱硫性能的影响。结果表明,载体的性质会显著影响负载型Pd催化剂的加氢脱硫性能。载体的比表面积对负载型Pd催化剂加氢脱硫活性影响不大,但是HYD路径的选择性与载体的孔道结构有关;具有介孔孔道结构有利于加氢路径选择性的提高。酸性载体负载的Pd催化剂表现出较好加氢脱硫活性和加氢选择性,这与氢溢流有关。介孔材料的孔道结构与微孔沸石的酸性有机结合,所得到的Z-M CM-41复合材料是是潜在的贵金属Pd加氢脱硫催化剂优良载体,可有效提升其加氢脱硫活性。     

Influence of the activation temperature on structural and textural properties of NiMo/Al2O3 hydrodesulfurization catalysts

Investigations of a commercial NiMo/Al₂O₃ hydrodesulfurization (HDS) catalyst are directed towards optimization of the activation procedure of HDS catalyst concerning active phase formation and thermal stability. Structural and textural data obtained with XRD, IR-FTIR, XPS and LTNA reveal that the optimal temperature for the formation of active species on the catalyst surface and an appropriate pore structure is 300°C.     

Ordered mesoporous alumina-supported metal oxides

The one-pot synthesis of alumina-supported metal oxides via self-assembly of a metal precursor and aluminum isopropoxide in the presence of triblock copolymer (as a structure directing agent) is described in detail for nickel oxide. The resulting mesoporous mixed metal oxides possess p6 mm hexagonal symmetry, well-developed mesoporosity, relatively high BET surface area, large pore widths, and crystalline pore walls. In comparison to pure alumina, nickel aluminum oxide samples exhibited larger mesopores and improved thermal stability. Also, long-range ordering of the aforementioned samples was observed for nickel molar percentages as high as 20%. The generality of the recipe used for the synthesis of mesoporous nickel aluminum oxide was demonstrated by preparation of other alumina-supported metal oxides such as MgO, CaO, TiO 2, and Cr 2O 3. This method represents an important step toward the facile and reproducible synthesis of ordered mesoporous alumina-supported materials for various applications where large and accessible pores with high loading of catalytically active metal oxides are needed.     

介孔硅材料及其负载型催化剂去除挥发性有机物的最新进展

介孔硅材料由于具有大的比表面积,均一的孔结构和大的孔径,常被用于分离、吸附和催化等领域.本文综述了近年来国内外介孔硅材料及其负载型催化剂去除各类挥发性有机物(VOCs)的研究进展,主要包括烃类、甲醇、甲醛、丙酮、苯、甲苯、萘、乙酸乙酯等.讨论了介孔硅材料的结构对VOCs吸附过程的影响;介绍了不同催化剂消除各类VOCs的催化性能及反应机理,并重点评述了甲苯在不同催化剂上的研究进展.分析结果表明,介孔硅材料的表面环境、孔道结构以及宏观形貌是影响VOCs分子在介孔硅材料上吸附的主要因素;贵金属催化剂的应用需要提高其抗中毒性以及降低成本;过渡金属的研究应着重于研发高活性的负载型过渡金属复合氧化物催化剂.最后对国内外介孔硅材料及其负载型催化剂的发展进行了展望,今后催化剂的设计可以从“氧化硅载体”和“介孔孔道”两个方面展开,这将为设计合适的催化剂处理各类VOCs污染物提供一定参考.     

加氢脱硫反应后催化剂β-Mo2N0.78的研究

在对βMo2N0.78催化剂加氢脱硫催化性能进行考察的基础上,对反应使用后催化剂的组成、结构变化、以及反应后催化剂再处理对活性的影响等几方面进行了研究。结果表明,在噻吩加氢脱硫条件下,βMo2N0.78 催化剂的氮含量下降,表层被硫化,而且钝化过程中产生的氮氧化物被消耗,但体相结构没有发生变化,表现了较强的抗硫化性能;脱硫反应前后催化剂的氢还原处理不能改善催化剂的活性,但预硫化催化剂在反应起始的活性与钝化催化剂在反应稳定时活性相近,加氢脱硫反应后催化剂的再次氮化处理,可以较大程度的恢复催化剂的初始活性。     

Gas diffusion and microstructural properties of ordered mesoporous silica fibers

Pore and surface diffusion of carbon dioxide (CO(2)) and ethylene (C(2)H(4)) in the nanopores of ordered mesoporous silica fibers about 200 microm in length was measured by the transient gravimetric method. The experimentally determined pore diffusivity data, coupled with the porosity, pore size, and fiber length, are used to obtain the actual length of the nanopores in silica fibers. These measurements reveal a structure of the ordered nanopores whirling helically around the fiber axis with a spiral diameter of about 15 microm and a pitch value of 1.6 microm. At room temperature the surface diffusion contributes about 10% to the total diffusional flux for these two gases in the nanopores of the ordered mesoporous silica fibers. The surface diffusion coefficients for the ordered mesoporous silica fibers are about 1 order of magnitude larger than the non-ordered mesoporous alumina or silica with similar pore size.     

Ni-Al类水滑石的制备及其Ni/Al2O3加氢脱硫研究

采用共沉淀方法合成了不同Ni/Al比的镍铝类水滑石,将其作为催化剂前驱体,制备了Ni/Al2O3加氢脱硫催化剂.通过X射线衍射法(XRD),程序升温还原(H2-TPR),热重分析(TG),傅里叶变换红外光谱(FT-IR)等技术对催化剂进行了表征.利用10 mL固定床装置在不同温度,压力,体积空速和氢油比条件下对Ni/Al2O3催化剂的加氢脱硫活性进行了评价.结果表明,XRD图和FT-IR图中均出现了Ni-Al类水滑石的特征峰,TG图呈现出两个明显阶段的失重,在Ni-Al2O3-HT的XRD图中最强的衍射角对应单质金属Ni粒子的(111)晶面.脱硫结果显示Ni-Al类水滑石作为前驱体在适当的条件下,FCC汽油的硫含量降至10 ppm以下.类水滑石作为前驱体的Ni/Al2O3加氢脱硫活性很好,说明类水滑石作为前驱体在加氢脱硫领域有好的应用前景.     

Catalytic upgrading of lignin derived bio-oil model compound using mesoporous solid catalysts

The catalytic upgrading of a lignin-derived bio-oil model compound, the hydrodeoxygenation of guaiacol, was performed using mesoporous solid catalysts. Platinum supported on silica and mesoporous silica (SBA-15 and KIT-6) were used as catalysts. The level of platinum incorporation and aluminum grafting did not alter the physical properties of the supports, such as surface area and pore size distribution. On the other hand, these treatments drastically affected the catalytic activities. A catalyst with platinum alone converted guaiacol to oxygenate compounds. In contrast, a series of catalysts with both platinum incorporation and aluminum grafting enhanced hydrodeoxygenation by converting guaiacol into hydrocarbons (cyclohexane and benzene). A comparison of the catalyst supports revealed the ordered mesoporous silica, SBA-15 and KIT-6, with high surface area, to have a higher hydrocarbon yield than conventional silica.     

规则中孔氧化铈的纳米铸型合成及作为高CO氧化活性金催化载体的应用

以有序的中孔炭材料CMK-3为模板,以硝酸铈为前体,利用纳米铸型法合成了具有规则结构的中孔氧化铈,考察了模板脱除温度对中孔氧化铈微结构的影响.热重、元素分析、X射线衍射、透射电镜和氮气物理吸附结果表明,炭模板的脱除温度可低至350℃,所得氧化铈具有二维六方规则结构,比表面积高达167 m~2/g,孔径分布集中在3～5nm.采用胶体沉积法将2-5nm的金溶胶粒子沉积到所得氧化铈表面制得了Au/CeO_2催化剂,考察了Au/CeO_2在CO氧化反应中的活性.结果表明,该催化剂的活性较常规氧化铈制备的金催化利有明显提高,这可能与载体的规则结构有关.     

Facile synthesis and characterization of novel mesoporous and mesorelief oxides with gyroidal structures.

In this paper, we bring forward an effective strategy, solvothermal postsynthesis, to prepare ordered mesoporous silica materials with highly branched channels. Structural characterizations indicate that the titled mesoporous materials basically have the cubic double gyroidal (space group Ia-3d) structure with small fraction of distortions. The mesopore sizes and surface areas can be up to 8.8 nm and 540 m2/g, respectively, when microwave digestion is employed to remove the organic templates. A phase transition model is proposed, and possible explanations for the successful phase transition are elucidated. The results show that the flexible inorganic framework, high content of organic matrix, and nonpenetration of poly(ethylene oxide) segments may facilitate the structural evolution. This new synthetic strategy can also be extended to the preparation of other double gyroidal silica-based mesoporous materials, such as metal and nonmetal ions doped silica and organo-functionalized silica materials. The prepared 3D mesoporous silica can be further utilized to fabricate various ordered crystalline gyroidal metal oxide "negatives". The mesorelief "negatives" (Co3O4 and In2O3 are detailed here) prepared by impregnation and thermolysis procedures exhibit undisplaced, displaced, and uncoupled enantiomeric gyroidal subframeworks. It has been found that the amount of metal oxide precursors (hydrated metal nitrates) greatly influence the (sub)framework structure and single crystallinity of the mesorelief metal oxide particles. The single crystalline gyroidal metal oxides are ordered both at mesoscale and atomic scale. However, these orders are not commensurate with each other.     

Facile Fabrication of Well‐Dispersed Pt Nanoparticles in Mesoporous Silica with Large Open Spaces and Their Catalytic Applications

In this paper, a facile strategy is reported for the preparation of well‐dispersed Pt nanoparticles in ordered mesoporous silica (Pt@OMS) by using a hybrid mesoporous phenolic resin‐silica nanocomposite as the parent material. The phenolic resin polymer is proposed herein to be the key in preventing the aggregation of Pt nanoparticles during their formation process and making contributions both to enhance the surface area and enlarge the pore size of the support. The Pt@OMS proves to be a highly active and stable catalyst for both gas‐phase oxidation of CO and liquid‐phase hydrogenation of 4‐nitrophenol. This work might open new avenues for the preparation of noble metal nanoparticles in mesoporous silica with unique structures for catalytic applications.     

一步制备高比表面积介孔Co3O4-CeO2及其表征(英文)

以有序介孔二氧化硅KIT-6为硬模板,硝酸钴、硝酸铈为金属源,分别在真空辅助条件和普通搅拌条件下制备了介孔CoCeO_x复合氧化物。采用XRD、SEM、TEM、N₂吸脱附等技术表征了复合氧化物的物化性质,并评价其氧化甲苯的性能。结果表明,在真空辅助和搅拌条件下制备的CoCeO_x氧化物是由Co₃O₄和CeO₂组成的介孔Co₃O₄-CeO₂复合氧化物,其比表面积分别为141和89 m²·g^-1,平均孔径分别为8.7和9.6 nm。真空辅助纳米复制过程有利于金属盐的前驱体充分填充到模板的孔隙中,去除模板后,可以得到有序的介孔复合金属氧化物。所制备介孔钴铈复合氧化物具有孔道有序性好、比表面积大的特点,在挥发性有机化合物的氧化去除方面具有一定的应用前景。     

Synthesis and characterization of nanocast silica NCS-1 with CMK-3 as a template

Nanocast silica (NCS-1) was synthesized by a casting process by employing the mesoporous carbon CMK-3 (the replica of SBA-15) as a template, tetraethoxysilane (TEOS) as the silica source, and hydrochloric acid (HCl) as the catalyst. The ordered carbon template was removed by employing different methods, such as calcination, thermal treatment followed by calcination, and controlled combustion. According to XRD and TEM characterization, NCS-1 exhibits an ordered structure with hexagonal symmetry and retains the morphology of the original SBA-15 used for the synthesis of CMK-3 over two replication steps on the nanometer scale. This demonstrates the well-connected porosity in CMK-3 type carbon, which can be used as a mold to synthesize mesostructured materials. The nitrogen adsorption isotherms generally show type IV shape, indicating mesoporous characteristics. The structure of NCS-1 is strongly influenced by variables of the nanocasting process, such as the loading amount of silica, hydrolysis temperature, and carbon removal methods. The surface area, pore size, and pore volume of NCS-1 can be tuned to a certain range by varying these parameters.     

氮掺杂有序介孔碳负载超小尺寸铂纳米颗粒催化硝基苯类化合物选择加氢

氮掺杂有序介孔碳材料不仅具有高的比表面积、大的孔容和均一可调的孔径等优点,其骨架中丰富的氮原子还可以对材料的物理化学性质、配位金属电荷密度等进行调控,是一类优异的催化剂载体.本文利用软模板(嵌段共聚物F127为模板),以间氨基苯酚为碳源和氮前体,制备出较高含氮量(9.58 wt%)和比表面积(417 m2/g),以及规则孔径分布的介孔碳材料.结果表明,制备的材料具有三维立方相结构.以该碳材料作为载体,使用传统浸渍氢气还原的策略负载纳米铂颗粒.发现氮掺杂的载体能够有效控制金属纳米颗粒的尺寸,可实现超小尺寸Pt纳米颗粒的有效负载(1.0±0.5 nm),且纳米颗粒均匀分布于介孔碳材料的孔道中.相比而言,使用相同负载方法的情况下,以不掺氮的介孔碳材料为载体,纳米粒子的尺寸较难控制(4.4±1.7 nm)且会发生孔道外颗粒聚集的情况.研究表明,骨架中的氮原子与金属间弱的相互作用对纳米粒子有稳定作用.这对制备超小尺寸的金属纳米粒子催化剂具有一定的指导意义.此外,由于纳米粒子的尺寸将大大影响催化剂活性中心的暴露程度,进而影响催化剂活性.因此,我们以硝基苯类化合物的氢化反应来评价该催化剂的催化性能.在室温和1 MPa H2的温和条件下,氮掺杂的介孔碳负载催化剂表现出了优异的催化性能.反应0.5 h,对氯硝基苯可完全转化,且选择性高达99%.相比而言,商业化的Pt/C催化剂上反应的转化率和选择性分别为89%和90%.其它传统催化剂的比较,如Pt/SiO2,Pt/TiO2,同样表明,氮掺杂介孔碳负载的催化剂具有更优异的催化性能.在相同反应条件下,Pt/SiO2催化剂只能得到46%的转化率和93%的选择性,而Pt/TiO2催化剂虽然能够实现完全转化,但选择性也仅为91%.由此可见,氮掺杂的负载催化剂可大大提高反应活性和选择性,能有效抑制脱氯现象的发生.这种高的催化性能可能与催化剂的介孔结构、氮功能化载体以及超小尺寸的Pt纳米粒子的稳定有关.由于氮原子和介孔孔道的限域作用,氮掺杂介孔碳负载的催化剂也具有良好的催化稳定性,循环使用10次后,催化活性和选择性几乎没有下降.结果表明,循环使用后的催化剂金属粒子尺寸变化不大,进一步表明氮掺杂介孔碳载体对金属纳米颗粒的稳定作用.     

Metallic nickel supported on mesoporous silica as catalyst for hydrodeoxygenation: effect of pore size and structure

Catalytic hydrodeoxygenation (HDO) of anisole, a methoxy-rich lignin-derived bio-oil model compound, was carried out over a series of Ni-containing (5, 10, 20, and 30 wt%) catalysts with commercial silica and ordered mesoporous silica SBA-15 as support. Both supports and catalysts were characterized by N₂ adsorption–desorption isotherms, X-ray diffraction, CO chemisorption, and transmission electron microscopy (TEM). Catalytic reaction was performed at 250 °C and 10 bar H₂ pressure. Depending on the catalyst support used and the content of active metal, the catalytic activity and product distribution changed drastically. Increase of the nickel loading resulted in increased anisole conversion and C₆ hydrocarbon (benzene and cyclohexane) yield. However, loading more Ni than 20 wt% resulted in a decrease of both conversion and C₆ yield due to agglomeration of Ni particles. In addition, Ni/SBA-15 samples exhibited much stronger catalytic activity and selectivity toward C₆ hydrocarbon products compared with Ni/silica catalysts. The differences in catalytic activity among these catalysts can be attributed to the effect of the pore size and pore structure of mesoporous SBA-15. SBA-15 can accommodate more Ni species inside channels than conventional silica due to its high pore volume with uniform pore structure, leading to high HDO catalytic activity.     

Kinetics of thiophene hydrodesulfurization over a supported Mo–Co–Ni catalyst

In this study, the kinetics of thiophene (TH) hydrodesulfurization (HDS) over the Mo–Co–Ni-supported catalyst was investigated. Trimetallic catalyst was synthesized by pore volume impregnation and the metal loadings were 11.5 wt % Mo, 2 wt % Co, and 2 wt % Ni. A large surface area of 243 m²/g and a relatively large pore volume of 0.34 cm³/g for the fresh Mo–Co–Ni-supported catalyst indicate a good accessibility to the catalytic centers for the HDS reaction. The acid strength distribution of the fresh and spent catalysts, as well as for the support, was determined by thermal desorption of diethylamine (DEA) with increase in temperature from 20 to 600 °C. The weak acid centers are obtained within a temperature range between 160 and 300 °C, followed by medium acid sites up to 440 °C. The strong acid centers are revealed above 440 °C. We found a higher content of weak acid centers for fresh and spent catalysts as well as alumina as compared to medium and strong acid sites. The catalyst stability in terms of conversion as a function of time on stream in a fixed bed flow reactor was examined and almost no loss in the catalyst activity was observed. Consequently, this fact demonstrated superior activity of the Mo–Co–Ni-based catalyst for TH HDS. The activity tests by varying the temperature from 200 to 275 °C and pressure from 30 to 60 bar with various space velocities of 1–4 h^?1 were investigated. A Langmuir–Hinshelwood model was used to analyze the kinetic data and to derive activation energy and adsorption parameters for TH HDS. The effect of temperature, pressure, and liquid hourly space velocity on the TH HDS activity was studied.     

过渡金属硫化物催化剂催化加氢作用机理

负载型过渡金属(Co、Mo、Ni、W)硫化物催化剂广泛应用于石油炼制催化加氢过程。为了开发高性能的加氢催化剂,过渡金属硫化物催化剂催化活性相的结构与加氢脱硫性能的关系一直以来是催化研究的热点之一。本文从过渡金属硫化物催化剂的活性相结构和反应物在催化剂表面活性位上的吸附-催化反应机理两个方面阐述了过渡金属硫化物催化剂的催化作用研究进展,并对过渡金属硫化物催化剂催化机理研究存在的争议和未来的研究方向进行了分析。     

Ordered porous metal oxide semiconductors for gas sensing

This review gives a comprehensive summary about the porous metal oxides with focus on the synthesis methods, structure related properties, as well as the modification strategies for gas sensing improved performances.