Preparation of the BaTiO3–SiO2 hybrid particles for the catalyst of methane steam reforming process

BaTiO₃ nano-coated SiO₂ (BaTiO₃–SiO₂) hybrid particles were prepared by liquid phase deposition and sol–gel process. The obtained BaTiO₃–SiO₂ hybrid particles have relatively high surface area (20 m² g⁻¹) at 600 °C annealing temperature. Ni component was impregnated to the obtained BaTiO₃–SiO₂ hybrid particles, and the obtained catalyst was used for the methane steam reforming process to consider the effect of the surface area on the catalytic activity. The catalytic activity of the Ni/BaTiO₃–SiO₂ catalyst was approximately three times as large as that of the reported Ni/BaTiO₃ catalyst, even in the lower process temperature. However, the limitation temperature for methane steam reforming process of this hybrid material was 600 °C, because of the diffusion of the Ba component.     

Influence of kaolinite crystalline structure in the production of γ-Al2O3 by alkaline lixiviation

The main uses of γ-Al₂O₃ of high surface and thermal stability, as catalyst and catalyst support, has originated several production methods such as the selective dissolution of siliceous components of kaolinite thermally amorphised. A high crystallinity degree of the raw kaolinite thermally treated between 750 and 1100 °C allows to obtain γ-Al₂O₃, with the desired characteristics, whatever the alkali concentration used. The specific surface of γ-Al₂O₃ obtained seems to be related to the alkali concentration utilised. A further calcination at 1250 °C generated α-Al₂O₃ of high surface and crystallinity.     

γ-Al2O3载体研究进展

氧化铝催化剂载体领域中,γ-Al2O3应用最为广泛.综述了γ-Al2O3载体的主要研究方向方面的进展:制备工艺低成本化、孔结构控制、提高载体稳定性和制备超细γ-Al2O3,并指出结合制备方法的改善,开发出大比表面积、适宜孔径分布及热稳定性和抗水合性良好的γ-Al2O3载体,同时发展纳米γ-Al2O3以满足实际生产的需要.     

在氧气中焙烧C/γ-Al2O3复合物快速制备α-Al2O3微粉

提出了一种快速制备α-Al₂O₃微粉的方法, 以淀粉为碳源、γ-Al2O₃为前体制备了C/γ-Al₂O₃复合物, 然后在800℃、氧气氛中焙烧制备α-Al₂O₃微粉. N₂物理吸附及SEM分析结果表明, 所制得的α-氧化铝颗粒细小, 约为2μm. 该方法具有焙烧温度低、焙烧时间短的优点, 同时, 淀粉及γ-Al₂O₃均为廉价的工业原料, 且该方法所需淀粉量较少, 最少仅需0.3g/g γ-Al₂O₃, 对应的C/γ-Al₂O₃复合物碳含量约为6wt%, 因而极具工业化应用前景.     

Adhesion Properties of Milled CuO-CeO2/γ-Al2O3 on Metallic Substrate for Automotive Catalytic Converter

Adhesion properties of CuO-CeO₂/γ-Al₂O₃ layers on FeCrAl metallic substrate was investigated, where the hybrid preparation method between suspension and sol-gel is further combined with the mechanical milling process of the slurry. Poor coating adhesion was observed when the slurry is vigorously stirred, where the milled powders are agglomerated, and the stirring process hardly reduces the particle size. The combined method was found to significantly improve the adhesion property between the milled CuO-CeO₂ catalytic layer and the γ-Al₂O₃ washcoat, compared with the vigorous stirring of the slurry. The so-called “over-milling” phenomenon was also exhibited, where the elongated large particles are observed after sintering of the longer-milled powders, leading to the lowered adhesion quality.     

Sol-gel preparation and thermal stability of Pd/γ-Al2O3 catalysts

A series of Pd/-Al₂O₃ catalysts with a designed loading of 1 wt % were prepared by the sol-gel method using boehmite (AlOOH) sols and various palladium compounds. These materials were developed for later use as inorganic membranes. The samples were calcined at 400 °C in flowing O₂ to decompose the Pd complex and change the phase of the support to -Al₂O₃. H₂ pulse chemisorption was used to determine the average Pd particle sizes, while particle size distributions were obtained from TEM micrographs. XRD was used to determine the crystallinity of the -Al₂O₃ support after extended treatments at 650 °C in O₂ and H₂ atmospheres. The physical properties of the support were studied using nitrogen adsorption-desorption at 77 K. Initial BET surface areas were about 350 m²/g. Pore size distributions were very narrow and centered at 3.6 nm, but broadened and became bimodal during the 650 °C treatments. An ion-exchanged sample prepared by traditional methods was used as a basis for comparison to the sol-gel samples.     

Preparation of NiMo/γ-Al2O3 catalysts with large pore size for vacuum residue hydrotreatment

γ-Al₂O₃ supports with large pore size were prepared by using rod-like ammonium aluminum carbonate hydroxide (AACH) as precursors. The textural properties of supports are dependent on the different crystallinity of the as-prepared AACH. For investigating their catalytic performance, NiMo/γ-Al₂O₃ hydrotreating catalysts were prepared by loading NiMo oxides on the supports and tested by using vacuum residue as reactant, and the results show that both pore structure and surface acid property of catalysts have significant influences on the catalytic activities for the hydrogenation and the removal of heteroatoms.     

Pd/γ-Al2O3复合膜的制备工艺研究

本文研究了采用Sol-Gel法制备用于H2分离的Pd/γ-Al2O3复合膜的工艺过程, 将含Pd2+的源物质直接加入到稳定、pH适宜的勃姆石(γ-AlOOH)溶液中, 用直接浸取的方法在多孔α-Al2O3衬底上成膜. BET测试表明, 复合膜的平均孔径为2.54.0nm. 分析了Pd的含量和工艺参数对复合膜的形貌和结构的影响, 并对膜材料进行了SEM、XRD和N2透气性能研究.     

Pd/γ-Al2O3复合催化膜的热稳定性

由溶胶凝胶法制备出Ｐｄ/γ－Ａｌ２Ｏ３催化膜及镧掺杂改性的Ｌａ/Ｐｄ/γ－Ａｌ２Ｏ３膜,研究了镧的掺杂对Ｐｄ/γ－Ａｌ２Ｏ３膜热稳定性的影响．用ＤＴＡ、ＸＲＤ、ＢＥＴ分别对膜的晶相和微孔结构(包括比表面积、孔径和孔容)进行了研究,结果发现:镧的掺杂明显提高了α－Ａｌ２Ｏ３的相变温度和高温下Ｐｄ/γ－Ａｌ２Ｏ３催化膜的热稳定性．Ｐｄ/γ－Ａｌ２Ｏ３经１１００℃处理５ｈ后,其比表面积、孔径和孔容分别为４．４６ｍ２/ｇ、３５．１ｎｍ和０．０５１ｃｍ３/ｇ,而经镧掺杂改性的Ｌａ/Ｐｄ/γ－Ａｌ２Ｏ３膜的比表面积、孔径和孔容分别为５１．６ｍ２/ｇ、７．２ｎｍ和０．１３８ｃｍ３/ｇ．     

Fe2O3/γ-Al2O3催化剂的制备表征及其催化活性的研究

采用浸渍法制备用于常温常压下催化湿式过氧化氢氧化工艺(CWPO)的负载型Fe2O3/γ-Al2O3催化剂,采用BET,SEM,XRD,XPS和XRF对其进行了表征,并以偶氮染料酸性橙为特征污染物,考察了Fe2O3/γ-Al2O3催化剂的催化活性和稳定性.研究表明,Fe2O3/γ-Al2O3催化剂中的活性组分Fe是以α-Fe2O3的形式存在,且Fe的负载量为1.907%(质量分数).对于初始浓度为500mg/L的酸性橙模拟废水,当Fe2O3/γ-Al2O3催化剂和H2O2氧化剂的投加量分别为30g/L和330mg/L时,处理3h时染料的脱色率、COD去除率和TOC去除率可分别达到82.10%,80.14%和74.2%.与传统Fenton试剂法相比,以Fe2O3/γ-Al2O3为催化剂的CWPO工艺具有矿化程度高和催化剂易回收再用的优点.     

Ce改性Fe2O3/γ-Al2O3催化剂的表征及催化活性研究

采用浸渍焙烧法分别制备了Fe2O3/γ-Al2O3和Ce改性的Fe2O3/γ-Al2O3催化剂,采用BET、XRD、XPS和XRF对其结构进行了表征,并用于常温常压CWPO工艺中,考察了Ce的掺杂对Fe2O3/γ-Al2O3催化剂催化活性和稳定性的影响.结果表明,Ce的掺杂提高了活性组分在载体表面的分散度,在相同的CWPO工艺条件下,Ce的掺杂使得Fe2O3/γ-Al2O3催化剂处理偶氮染料废水的催化活性提高了10%左右.     

α-Al2O3/γ-Al2O3/Teflon AF2400中空纤维油气分离膜的制备及性能研究

快速检出变压器绝缘油中溶解气体含量可及时分析变压器的故障种类和程度。但传统油气分离膜的分离效率低,不满足最新标准和人工巡检要求。为了提高分离效率,制备了α-Al_2O_3/γ-Al_2O_3/Teflon中空纤维复合膜,并研究了γ-Al_2O_3及退火温度对复合膜界面性能和传输阻力分布的影响。结果表明,γ-Al_2O_3的加入对整体复合膜气体传输阻力的影响小,且能够有效改善有机/陶瓷复合膜的界面性能。并在330℃下退火,可进一步提高复合膜的界面强度。最终制备出的中空纤维分离膜具有更加低的气体传输阻力,可在1 h内使7种绝缘油中溶解气体均达到平衡,进一步提高了取气效率,为快速检测变压器绝缘油中溶解气体含量奠定了基础。     

Characterization of oxide Co-Mo/γ-Al2O3 hydrodesulphurization catalysts prepared by different methods

Three series of oxidic Co-Mo/-Al₂O₃ catalysts with different cobalt content and prepared by three different methods have been studied by X-ray diffraction, diffuse reflectance spectroscopy and magnetic techniques. The results show that the formation of Co and Mo surface species is affected by the method of catalyst preparation and that Mo enhances the dispersion of the cobalt species. The presence of Co₃ O₄ was clearly detected in cobalt-rich samples prepared by a two-step method, especially when Mo was incorporated by equilibrium adsorption. It also seems that in catalysts prepared by wet consecutive impregnation Co favours the formation of a Mo multilayer on the surface of Al₂O₃. However, in catalysts prepared by simultaneous impregnation the segregation of Co₃O₄ and the formation of a Mo multilayer occurs less extensively.     

高比表面积γ-Al2O3的制备研究进展

综述了近年来国内外高比表面积介孔γ-Al2O3的制备研究进展,介绍了模板法、超临界法、一步湿化学法、爆轰法等制备方法,分析了其制备过程中的影响因素及产品的性能;比较了各种高比表面积介孔γ-Al2O3合成方法,探讨了合成高性能产品的途径,同时展望了今后的研究方向.     

Ni-Fe/γ-Al2O3乙醇水蒸汽重整制氢催化剂研究

采用沉淀法制备了一系列不同Fe助剂含量的Ni-Fe/γ-Al_2O_3催化剂.采用XRD、TPR、SEM等手段对催化剂进行表征,发现Fe的加入可以有效地置换出NiAl_2O_4尖晶石中的Ni使之以NiO晶体形式存在.同时,降低了催化剂的还原温度,大大减轻催化剂的团聚现象.催化剂性能测试结果表明,15%Ni-10%Fe/γ-Al_2O_3表现出最好的氢气产率和选择性,650℃时分别为4.71%和68.78%.500℃时对15%Ni-10%Fe/γ-Al_2O_3催化剂进行30h稳定性测试,结果表明,整个阶段氢气的选择性在测试时间段内始终保持在65%左右,没有发现乙烯等副产物.     

Synthesis of chitosan/γ-Fe2O3/fly-ash-cenospheres composites for the fast removal of bisphenol A and 2,4,6-trichlorophenol from aqueous solutions

The chitosan/fly-ash-cenospheres/γ-Fe(2)O(3) (CTS/γ-Fe(2)O(3)/FACs) magnetic composites were prepared by microemulsion process. The resulting composites were characterized by XRD, FT-IR, SEM, TGA, DTG and VSM, and the results indicated that CTS/γ-Fe(2)O(3)/FACs exhibited magnetic property (M(s)=6.553 emu g(-1)) and thermal stability, and composed of chitosan wrapping magnetic γ-Fe(2)O(3) and fly-ash-cenospheres (thickness of the cross-linked chitosan was about 5.2 μm). Then the CTS/γ-Fe(2)O(3)/FACs were employed as adsorbents for the fast removal of bisphenol A (BPA) and 2,4,6-trichlorophenol (TCP) from aqueous solutions. The adsorption performances of CTS/γ-Fe(2)O(3)/FACs were investigated by batch mode experiments with respect to pH, temperature, initial concentration, contact time and binary solution system. The Langmuir isotherm model was fitted to the equilibrium data better than the Freundlich model, and the kinetic properties were well described by the pseudo-second-order equation. The effects of binary solution systems also demonstrated that BPA adsorption onto CTS/γ-Fe(2)O(3)/FACs was more affected by the simultaneous presence of competitive phenolic compound than that of TCP. In addition, the resulting composite reusability without obviously deterioration in performance was demonstrated by at least three repeated cycles.     

Fabrication and mechanical properties of α-Al2O3/β-Al2O3/Al/Si composites by liquid displacement reaction

Al₂O₃/metal composites were fabricated by heating three kinds of commercial mullite refractories in contact with Al, and their mechanical properties were investigated. Aluminum reacted with the mullite and SiO₂-glass constituting the mullite refractories and changed them into -Al₂O₃ and Si. Simultaneously, -Al₂O₃ was formed by the reactions among -Al₂O₃ and sodium and potassium oxides in the glassy phase. Also, Al penetrated into the -Al₂O₃/-Al₂O₃/Si composite by partly dissolving Si. Finally, the mullite refractories were changed into -Al₂O₃/-Al₂O₃/Al/Si composites. The phase contents, microstructures and mechanical properties of the resulting composites varied with the composition of the refractories. The content of -Al₂O₃ in the composite was lowest at the lowest Na₂O and K₂O contents in the refractories. Silicon in the composite had its highest content at the highest SiO₂ content. The composite fabricated from SiO₂/Al₂O₃ (in mol) (SAR)=1.85 consisted of 2–5 m Al₂O₃ grains embedded in metal, but that from SAR=1.05 showed a complicated microstructure with small and large grains. The bending strength of the composites fabricated from the refractories of SAR=1.85, 1.24, and 1.05 were 327, 405 and 421 MPa, respectively. Also, the corresponding fracture toughness values were 5.2, 6.1, and 5.5 MPam , respectively.     

A novel wet chemistry/two-step calcining process for the synthesis of ultrafine α-Al2O3 particles

Ultrafine α-Al₂O₃ particles have been synthesized via a wet chemistry/two-step calcining process. X-ray diffraction (XRD) analysis shows that the as-synthesized particles are of single-phase α-Al₂O₃. The grain size of the particles is examined by TEM analysis and is found to be around 80–100 nm. The study demonstrates a novel process for the synthesis of ultrafine α-Al₂O₃ particles.     

Effect of the starting Al2O3 and of the method of preparation on the characteristics of Li-stabilized β″-Al2O3 ceramics

The influence of the morphology and the size of the particles of various types of starting Al₂ O₃ material on the synthesis and characteristics of Li-stabilized'-Al₂O₃ ceramics have been investigated. The use of highly dispersed oxides makes it possible to attain higher densities in the fired ceramic bodies due to their higher reactivity. In the case of oxides obtained from ammonium alum, the degree of dispersion and the reactivity may be increased by raising the amount of-Al₂O₃ up to a certain limit. Alumina prepared from Al₂ (OH)₅ NO₃ by slurry solution spray-drying also gives satisfactory results despite its lower degree of dispersion. This is connected with the morphology of the particles. In the case of synthesized materials containing an insufficient amount ofAl₂O₃-NaAlO₂ eutectic, high densities may also be achieved by applying a two-step firing schedule at temperatures above the melting point of the eutectic.