Dispersity of Al2O3?SnO2 supported platinum from hydrogen pulse chemisorption

This study is concerned with the effect of various amounts of Sn species in modifying the dispersity of Al₂O₃–SnO₂ supported platinum catalysts by application of hydrogen chemisorption in a pulse chromatographic system, as well as determination of activity in water-gas shift reaction (WGS).     

Two-stage catalytic system of Sn/Al2O3 and Pt/Al2O3for NO reduction by propene in lean conditions

The Pt/Al₂O₃, Sn/Al₂O₃catalysts were prepared by the single sol-gel method. The two-stage Sn/Al₂O₃and Pt/Al₂O₃catalyst in series for NO reduction with propene were investigated. The coexistance of water vapor enhanced the activity at medium temperature of 300-400^oC, and the NO conversion was above 50% at 225 to 500^oC even in the presence of water vapor and SO₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Selective catalytic reduction of NO over metal oxide or noble metal-doped In2O3/Al2O3 catalysts by propene in the presence of oxygen

The activities of metal oxide CuO, SnO₂, CoO, Ag₂O, ZnO or noble metal Pt, Pd, Rh-doped In₂O₃/Al₂O₃ catalysts for selective catalytic reduction of NO by propene were investigated. The temperature windows for NO reduction over noble metal-doped In₂O₃/Al₂O₃ catalysts were shifted and broaden slightly compared with single component catalyst alone. This revised version was published online in June 2006 with corrections to the Cover Date.     

Selective Catalytic Reduction of NO with Propene over Au/Fe2O3/Al2O3 Catalysts

A series of Au/Fe₂O₃/Al₂O₃ catalysts were prepared by the homogeneous deposition-precipitation method. The catalytic activity of the catalyst samples for selective catalytic reduction of NO by propene under oxygen-rich atmosphere was evaluated. The results showed that 2%Au/10%Fe₂O₃/Al₂O₃ exhibited good low-temperature activity. The maximum of NO conversion reached 43% at 300 °C, while it was only 21% over the 2%Au/Al₂O₃ catalyst at the same temperature. The addition of 2% steam to the feed gas had little effect on the catalytic activity. X-ray diffraction results indicated that both Au and Fe₂O₃ particles were highly dispersed over Al₂O₃. H₂-temperature-programmed reduction results indicated that there was strong interaction between Au and Fe₂O₃, which made the reduction of Fe₂O₃ easy. The synergistic effect between Au and Fe₂O₃ was probably responsible for the good catalytic performance of the Au/Fe₂O₃/Al₂O₃ catalyst at low temperature.     

Synthesis and characterization of SnOx/Al2O3 derived gel catalysts

SnO_x/Al₂O₃ catalysts were prepared by the sol-gel method using as starting reactants aluminium-tri-s-butoxide and (i) tetrabutyltin, (ii) tin tetrachloride and (iii) tin tetra-t-amyloxide. The gel derived catalysts show acidities of 0.72, 1.08 and 1.05 mol NH₃/m² and BET areas of 91, 112 and 189 m²/g. The activity and selectivity pattern for isopropanol decomposition were found to depend strongly on the tin precursor used.     

过渡金属修饰Fe2O3/Al2O3氧载体的Redox性能研究

采用冷冻干燥法分别制备了经Cu、Co、Mn、Ni修饰的Fe₂O₃/Al₂O₃氧载体。利用化学吸附仪,通过程序升温还原(H₂-TPR)和程序升温氧化(TPO)来研究经不同过渡金属修饰的Fe₂O₃/Al₂O₃与H₂和O₂的反应性能。实验发现,在Fe₂O₃/Al₂O₃中加入Cu、Co、Ni以后,氧载体与H₂的反应性都有提高,但是当在Fe₂O₃/Al₂O₃中加入Mn以后,氧载体的反应性和载氧能力反而下降。经Cu修饰的Fe₂O₃/Al₂O₃与H₂的反应性最高,且具有很好的反应稳定性,适合用于化学链燃烧。     

Cu修饰的Fe2O3/Al2O3氧载体的循环反应稳定性研究

采用冷冻干燥法制备了经Cu修饰（10%）的Fe₂O₃/Al₂O₃氧载体。利用热重分析仪分别在850、900和950 ℃等温环境下,使氧载体交替接触还原气体和氧化气体,来模拟氧载体在化学链燃烧中的循环过程。结果表明,经Cu修饰的Fe₂O₃/Al₂O₃氧载体在850和900 ℃下的等温循环过程中反应性能都很稳定,在950 ℃时的循环反应前期有微量烧结,但在循环后期反应性能也很稳定。随着反应温度的升高,氧载体氧化速率增大,还原速率和载氧率先减小后增大。与未经修饰的Fe₂O₃/Al₂O₃氧载体相比较,在900 ℃下作等温循环实验,经Cu修饰的Fe₂O₃/Al₂O₃氧载体具有较高的载氧能力和还原速率,但氧化速率较低;两者都具有较好的循环稳定性。     

TPR studies on steam reforming of 2-propanol on Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3

Reaction pathways for steam reforming of 2-propanol (isopropyl alcohol, IPA) on Rh/Al₂O₃, Ru/Al₂O₃ and Pd/Al₂O₃ have been studied by temperature-programmed reactions (TPRs) of IPA and acetone in the presence of steam. The results of TPRs suggest that that of IPA on Rh/Al₂O₃ and Ru/Al₂O₃ proceeds via acetone, while the steam reforming of IPA on Pd/Al₂O₃ takes place via propene from acetone. This revised version was published online in August 2006 with corrections to the Cover Date.     

Direct synthesis of hydrogen peroxide from H2/O2 using Pd/Al2O3 catalysts

Pd/Al₂O₃ catalysts were prepared by the impregnation method and were used for the direct formation of hydrogen peroxide from H₂ and O₂. The H₂O₂ concentration and selectivity were strongly dependent on the solubility of hydrogen in the reaction medium. The modification of the support by halogenate has a beneficial effect on the selectivity. The state of the active Pd on Pd/Al₂O₃ catalysts was studied using X-ray photoelectron spectroscopy, and Pd(0) was found to be active.     

Al2O3/SnO2 Co-Nanoparticle Modified Grafted Collagen for Improving Thermal Stability and Infrared Emissivity

Al2O3/SnO2 co-nanoparticles were prepared with a modified sol-gel technique followed by a thermal treatment process. With these co-nanoparticles the grafted collagen-Al2O3/SnO2 nanocomposites were obtained using a supersonic dispersion method. X-ray diffraction, FT-IR analysis, transmission electron microscopy, TGA/DTA and infrared emissivity test were performed to characterize the resulting nanoparticles and nanocomposites, respectively. The Al2O3/SnO2 co-nanoparticles showed a narrow distribution of size between 20-40 nm and could be uniformly absorbed on the tri-helix scaffolds of the grafted collagen without any aggregation. The nanocomposites possessed better thermal stability and substantially lower infrared emissivity than the grafted collagen and Al2O3/SnO2 co-nanoparticles with an increase of degradation temperature from 39 to 210 ℃ and a decrease of infrared emissivity from 0.850 of the grafted collagen and 0.708 of the Al2O3/SnO2 co-nanoparticles to 0.424, which provided a potential application of the nanocomposites to areas such as photoelectronics.     

超声改性的CuO/Al2O3-MgO催化剂结构 及其超低浓度甲烷催化燃烧性能

采用普通浸渍和超声改性的方法分别制备了CuO/Al₂O₃-MgO催化剂,用于超低浓度甲烷的催化燃烧,并利用SEM、XRD、XPS、H₂-TPR等技术对催化剂进行表征,研究了超声改性作用对催化剂的结构和性能的影响.结果表明,与普通浸渍法制备的催化剂相比,在超声改性的CuO/Al₂O₃-MgO催化剂上,甲烷的转化率得到提高,燃烧特征温度降低.随着超声时间的延长和超声功率的增加,催化剂的催化活性均呈现先增大后减小的趋势;催化剂制备的最佳超声工况为功率150 W、时间20 min.超声改性可使催化剂的比表面积和孔容积增大,表面催化活性较高的Cu⁺浓度增加,活性组分CuO由晶相向非晶相转变、分散度增大,晶粒粒径变小、分布更均匀;这使得甲烷催化燃烧的表观活化能下降、催化剂活性得到增强.     

Photodegradation of 2,4-D over PdO/Al2O3-Nd2O3 photocatalysts prepared by the sol-gel method

The photocatalytic activity of 1.0 wt% PdO supported on Al₂O₃-Nd₂O₃ binary oxides prepared by the sol-gel method was studied in the photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The photocatalysts were characterized by N₂ physisorption, XRD and UV-vis spectroscopy. PdO supported on γ-Al₂O₃ photo-degrades the 2,4-D, however the addition of Nd₂O₃ to γ-Al₂O₃ notably improves the photocatalytic activity. As the concentration of Nd₂O₃ in the binary oxide increases from 2 to 10 wt%, the photodegradation of 2,4-D is highly enhanced. The catalytic test for PdO supported on pure Nd₂O₃ showed scarce photocatalytic activity. Total organic carbon (TOC) analysis showed that the 2,4-D has been completely destroyed on the PdO/Al₂O₃-Nd₂O₃ photocatalysts after 6 h under irradiation.     

Preparation of MoO3/g-Al2O3 catalyst by the reaction of a-boehmite with MoO3/H2O slurry - dual role of MoO3 as active phase and texture stabilizer during calcination

Summary Catalyst MoO₃/g-Al₂O₃ was prepared by the reaction of a-boehmite with molybdic acid in slurry MoO₃/H₂O followed by calcination. The deposited MoO₃ functioned as thermal stabilizer and inhibited sintering of Al₂O₃ phase during calcination. After calcination at 550 and 650^oC the surface area of Al₂O₃ obtained from a-boehmite was 207 and 172 m² g^-1, respectively, and of MoO₃/Al₂O₃ obtained from MoO₃/a-boehmite was 323 and 285 m² g^-1, respectively. On the other hand, molybdic acid did not work as peptization agent and the mechanical strength of MoO₃/Al₂O₃ was not higher than of Al₂O₃. The catalyst was sulfided and its activity in thiophene hydrodesulfurization was tested; it exhibited about the same activity as reference industrial MoO₃/Al₂O₃ catalyst.     

MgFe0.1Al1.9O4 的合成及其催化乙苯与 CO2 的氧化脱氢反应

 以柠檬酸为络合剂, 采用溶胶-凝胶法制备了具有尖晶石结构的 MgFe_0.1Al_1.9O₄ 催化剂, 并将其用于催化乙苯与 CO₂ 氧化脱氢反应. 运用 X 射线衍射、X 射线能量色散光谱分析、红外光谱、热重-差热、N₂ 吸附-脱附和 H₂ 程序升温还原等技术对催化剂进行了表征. 结果表明, 在 650 ºC 以上焙烧即可制得结构确定、组成均一的 Mg-Fe-Al-O 复合氧化物催化剂, 其中 Fe 物种主要以同晶取代的形式存在于尖晶石骨架中. 随着焙烧温度的升高, 尖晶石结晶度提高, Fe 物种还原能力下降, 催化剂晶粒度增大, 比表面积降低. 700 ºC 焙烧制备的 MgFe_0.1Al_1.9O₄ 具有较好的催化乙苯与 CO₂ 氧化脱氢反应活性和稳定性.     

The support and characterization of C60 and MoO3 on Al2O3

A new type of catalyst from supporting C₆₀ on MoO₃ and Al₂O₃ has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO₃ on C₆₀/Al₂O₃ and calcined in N₂, there is a stronger interaction between C₆₀, MoO₃ and Al₂O₃, but when supporting C₆₀ on MoO₃/Al₂O₃, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C₆₀–O–Al, is formed.     

乙醇辅助的化学沉积法制备硫化型Mo/γ-Al2O3加氢脱硫催化剂

以硫代乙酰胺为硫源,钼酸钠为钼源,乙醇为分散剂,采用化学沉积法制备了MoS₃/Al₂O₃催化剂前驱体,再用H₂高温处理得到高分散硫化型MoS₂/γ-Al₂O₃催化剂,运用N₂吸附-脱附、X射线光电子能谱以及高分辨透射电子显微镜等技术对MoS₂/γ-Al₂O₃催化剂进行了表征,并以二苯并噻吩作为模型化合物评价了催化剂的加氢脱硫(HDS)活性.结果表明,与浸渍法相比,所制催化剂具有更大的比表面积和孔体积、更高的活性金属分散度、更佳的Mo物种硫化度以及更短的MoS₂片层长度和更高的堆积度,因而在二苯并噻吩HDS反应中表现出远优于浸渍法所制催化剂的活性.乙醇可通过S?H-O氢键吸附至MoS₃纳米粒子表面,可有效防止其生长和团聚,起到分散剂的作用.     

Catalytic Combustion of Ethyl Acetate over Al2O3- Ce0.5Zr0.5O2 Supported Metal Oxide Catalysts

The catalysts for the combustion of ethyl acetate were prepared using Fe, Co, Cu, Cr, and Mn metal oxide as active components supported on Al₂O₃-Ce_0.5Zr_0.5O₂ mixed oxides and characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), oxygen storage capacity measurement, BET surface area, XPS measurement, and activity test. According to the results of characterization, it was found that Cu/Al₂O₃-Ce_0.5Zr_0.5O₂ (1:2, mass ratio) and Mn/Al₂O₃-Ce_0.5Zr_0.5O₂ (1:2) catalysts presented excellent activity for the catalytic combustion of ethyl acetate, because of the more reducible species and high reducibility of the catalysts. For ethyl acetate oxidation, more than 99% conversion was achieved at 245 °C over catalysts Cu/Al₂O₃-Ce_0.5Zr_0.5O₂ (1:2) and Mn/Al₂O₃-Ce_0.5Zr_0.5O₂ (1:2, mass ratio), indicating that the catalysts had great potential for wide use.     

Study of Ce0.7Sn0.3O2 supported PdO catalysts for CO oxidation

Palladium supported by Ce_0.7Sn_0.3O₂ has been prepared by an impregnation method, and used for low temperature carbon monoxide oxidation. They were characterized by means of XRD and H₂-TPR techniques. For PdO/Ce_0.7Sn_0.3O₂ catalyst, three reduction peaks (α, β and γ) are observed. The β peak contributes to the reduction of PdO species and Sn⁴⁺ species on the surface of Ce_0.7Sn_0.3O₂; β peak to the reduction of bulk SnO₂ and surface Ce⁴⁺and the γ peak to the reduction of bulk CeO₂. The increase of Pd loading from 0 to 0.75% enhances oxidation of CO, further increase of the Pd content affects the catalytic activity but slightly. XRD and TPR results show that highly dispersed Pd on the surface of the support is the active species for CO oxidation. This revised version was published online in June 2006 with corrections to the Cover Date.     

柠檬酸添加方式对Mo-Ni-P/Al_2O_3催化剂加氢活性的影响

以Mo、Ni为活性组分,Al_2O_3为载体,采用不同柠檬酸添加方法制备了Mo-Ni-P/Al_2O_3催化剂.通过氢气程序升温还原(H2-TPR)、X射线衍射(XRD),透射扫描电镜(TEM)、XPS等表征方法研究催化剂的物化性质.结果表明:催化剂经柠檬酸的后处理,改善了载体氧化铝表面羟基基团的分布,促使Mo物种以八面体配位多核聚钼酸的形态存在,有效地减弱了载体与活性金属之间的强相互作用,提高了Mo物种的分散度与硫化度,使得催化剂形成更多"Mo-Ni-S"加氢活性相,提高了催化剂的加氢活性.与其他处理方法相比,柠檬酸后处理的催化剂对VGO具有更高的加氢脱硫、脱氮与芳烃饱和性能.     

Rapid Synthesis of Nanocrystalline TiO2/SnO2 Binary Oxides and Their Photoinduced Decomposition of Methyl Orange

A rapid and simple method, the so-called stearic acid method (SAM) was developed to prepare nanostructured TiO₂/SnO₂ binary oxides by combustion of stearic acid precursors. The preparative process was studied by Fourier transform infrared spectroscopy (FT-IR). During the preparative process, metal precursors were dispersed in stearic acid at molecular level. Microstructure of the samples was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET specific surface area measurement and the results were compared with those obtained by conventional sol-gel method. The photocatalytic decomposition of methyl orange was used as a model system to determine the relative influences of the preparation method and the concentration of SnO₂ on the photocatalytic activities. It was found that preparative methods affected the crystalline structure of TiO₂/SnO₂ powders and the anatase phase of TiO₂ was stabilized by the addition of SnO₂ in SAM. The samples prepared by SAM showed better dispersity, larger specific surface area and the TiO₂/SnO₂ (r=0.15, SAM) catalyst showed higher photocatalytic activity than Degussa P25.