Pd-Cu/γ-Al2O3催化苯乙炔选择性加氢反应

为了提高苯乙炔加氢反应中的苯乙烯选择性, 本文采用“胶体-等体积浸渍”两步法制备了Pd-Cu/γ-Al₂O₃双金属催化剂. 利用高分辨率透射电镜(HRTEM)、X射线光电子能谱(XPS)、CO脉冲化学吸附、N2物理吸附、电感耦合等离子体原子发射光谱(ICP-AES)等技术表征了Pd-Cu/γ-Al₂O₃的结构性质, 考察了Cu/Pd 摩尔比、Pd负载量以及金属引入顺序对Pd-Cu/γ-Al₂O₃催化苯乙炔选择性加氢性能的影响. 结果表明, 与Pd/γ-Al₂O₃单金属催化剂相比, Pd-Cu/γ-Al₂O₃的苯乙烯选择性大幅度提高, 尤其是当Pd负载量为0.3%(w), 且Cu/Pd摩尔比为0.6时, Pd-Cu/γ-Al₂O₃表现出优异的加氢选择性; 在0.1 MPa和40 ℃下, 当苯乙炔转化率为90%时, 双金属催化剂的苯乙烯选择性可达95%; 当转化率达到99%以上时, 苯乙烯选择性仍保持在82%左右. 分析表明, Pd-Cu/γ-Al₂O₃中形成了Pd-Cu合金, 但是两种金属间不存在电子转移, Cu对Pd的几何效应才是导致Pd-Cu/γ-Al₂O₃苯乙烯选择性增加的主要原因.     

Selective hydrogenation of phenylacetylene on Pd/Al2O3: Effect of the addition of Pt and particle size

Phenylacetylene hydrogenation on Pd, Pt and Pd–Pt/Al₂O₃ catalysts has been studied. In all catalysts activity was found not to depend on particle size. However, selectivity to styrene was found to depend on Pd/Al₂O₃ catalysts. Carbon deposition in both metal and support explains such a behavior. Nevertheless, in small Pd particles a longer residence time of styrene may control the selectivity.     

Influence of Pd-Ce interaction and chlorine ion on hydrodesulfurization reaction: The activity and sulfur tolerance of the Pd-Ceo2/Al2O3 catalyst

CeO₂ promoted palladium catalysts supported on Al₂O₃ were prepared using the impregnation (IM) and the deposition-precipitation (DP) methods. The activities and sulfur tolerance of the catalysts for hydrodesulfurization (HDS) were detected with thiophene HDS as probe reaction. H₂ adsorption, XRD, FTIR, NH₃-TPD, XPS were used to characterize the catalysts. The Pd-CeO₂/Al₂O₃ (IM) catalyst was highly active for the HDS reaction, and it had much stronger sulfur tolerance than the Pd/Al₂O₃ catalyst. Pd-CeO₂/Al₂O₃ (DP) showed excellent sulfur tolerance while its initial activity decreased. It was observed that with the chlorine bridge, the interfacial structure of Pd-Cl⁻¹-Ce³⁺ was responsible for the high activity of the Pd-CeO₂/Al₂O₃ (IM) catalyst, at the same time the interaction of Pd with Ce was weakened by Cl₋₁ ions. The enhanced sulfur tolerance over the Pd-CeO₂/Al₂O₃ (IM) catalyst was attributed to the weakened Pd-S bond caused by the competitive adsorption of H₂S on Ce³⁺ ions. As to the Pd-CeO₂/Al₂O₃ (DP) catalyst, a strong interaction of Pd with Ce put Pd at an electron-deficient state, the creation of sulfided palladium was therefore inhibited.     

乙烷氧化脱氢用Ni/Al2O3催化剂中活性镍物种前驱体（英文）

Ni/Al2O3 catalysts for oxidative dehydrogenation(ODH) of ethane were prepared by impregnation of Al2O3 with nickel acetate or nickel nitrate,and by mechanical mixing of NiO and Al2O3.The Ni-based catalysts were characterized by N2 adsorption-desorption,X-ray diffraction,diffuse reflectance UV-visible diffuse reflectance spectroscopy,and temperature-programmed reduction of hydrogen.The results showed that formation of crystalline NiO particles with a size of < 8 nm and/or non-stoichiometric NiO species in the Ni/Al2O3 catalysts led to more active species in ODH of ethane under the investigated reaction conditions.In contrast,tetrahedral Ni species present in the catalysts led to higher selectivity for ethene.Formation of large crystalline NiO particles(22-32 nm) over Ni/Al2O3 catalysts decreased the selectivity for ethene.     

Effect of H2S-uptake on the conversion of cyclohexene on Ru- and Pd-promoted molybdena-alumina catalysts

The effect of H₂S on the activity and selectivity of catalysts (Ru/Al₂O₃, Pd/Al₂O₃ and Ru and Pd promoted molydena-alumina) was different (on differnt catalysts and different conversions of cyclohexene). Ru-containing catalysts showed higher sulfur sensitivities than the Pd-containing ones. The sequence of catalysts by their H₂S uptake related to mass of catalyst was PdMo/Al₂O₃RuMo/Al₂O₃Mo/Al₂O₃>Pd/Al₂O₃Ru/Al₂O₃.     

Temperature-programmed desoprtion of H2 from the surfaces of pd/support and Pd-Ag/support catalysts (support = Al2O3, SiO2)

Thermal desorption of H₂ from the surface of Pd/support and Pd-Ag/support (support = Al₂O₃, SiO₂) catalysts has been investigated. Two wide desorption peaks can be observed for the 5% Pd/support catalyst. The presence of these peaks in the thermogram indicates that several adsorption states exist, which is the result of occurrance of different adsorption centers of specific bond strengths for hydrogen. The addition of silver to the palladium catalysts causes a considerable decrease in the size of the high temperature desorption peak. It is also worth noting that the temperature of the maximum of the desorption rate remains practically constant for all bimetallic catalysts studied. This means that the activation energy of the hydrogen desorption process does not change after the introduction of silver to the palladium catalyst.     

Pd(111), Pd(100)及Pd(110)表面H2和O2直接合成H2O2的密度泛函理论研究

采用周期性密度泛函理论研究了H₂和O₂在Pd(111),Pd(100)及Pd(110)表面上直接合成H₂O₂的反应机理,对反应的主要基元步骤进行了计算和分析.结果表明,Pd(111)表面对H₂O₂直接合成的催化选择性最好,表面原子密度较低的Pd(100)表面和Pd(110)表面上含有O-O键的表面物种解离严重,不利于H₂O₂的生成.H₂O₂的选择性与含有O-O键表面物种的O-O键能和表面物种的结合能有关.含有O-O键的表面物种在表面的结合能越大,越容易发生解离,不利于形成H₂O₂.     

Ethylcyclopentane ring opening reaction over PtGe/Al2O3 catalysts prepared by controlled surface reaction

Platinum-germanium catalysts supported on a non-acidic Al₂O₃ have been prepared by adding Ge in amounts corresponding nominally to 1/8 (PtGe1/8/Al₂O₃); 1/2 (PtGe1/2/Al₂O₃); 1 (PtGe1/Al₂O₃) and 2 (PtGe2/Al₂O₃) monolayers by controlled surface reaction of Ge(n-C₄H₉)₄ to Pt/Al₂O₃. These catalysts were characterized by electron microscopy (TEM), FTIR of CO adsorption and H₂ chemisorption. The ring opening of ethylcyclopentane (ECP) was studied as a test reaction between 543 and 633 K. PtGe1/8/Al₂O₃ catalyst produced the most ring opening products (ROP) in the whole temperature range. A good agreement with statistical values of ROP was observed at low temperature, but at higher temperature, the opening became selective, producing mostly heptane. Bimetallic catalysts PtGe1/Al₂O₃ and PtGe2/Al₂O₃ led to a nonselective hydrogenolysis, similar to the monometallic platinum catalyst Pt/Al₂O₃. The catalysts PtGe1/Al₂O₃ and PtGe2/Al₂O₃ produced ROP with the lowest selectivity; instead, much aromatics and fragments were formed, in increasing amounts above 600 K.     

Vapor phase hydrofluorination of acetylene to vinyl fluoride over La2O3-Al2O3 catalysts

A series of La-doped Al₂O₃ catalysts were prepared and tested for the vapor phase hydrofluorination of C₂H₂ to vinyl fluoride (CH₂CHF, VF). It was found that the La-doped catalyst gave a stable catalytic performance and a higher selectivity to the desired VF and a lower selectivity to coke deposition compared with the pure Al₂O₃ catalyst. The enhancement in VF selectivity on the La-doped catalyst was due to the elimination of acidic sites on the Al₂O₃ surface by the addition of La₂O₃, evidenced by NH₃-TPD results, which could also explain the declined selectivity to coke deposition on the catalyst. Raman result indicated there were two different vibration forms of CH distortion and CC expansion for the coke deposition.     

过渡金属改性的Pd/TS-1催化氢、氧直接合成H_2O_2的性能

利用等体积浸渍法制备了M-Pd/TS-1(M=Ce,La,Pt,Fe,Co,Ni,Cr,Mn,Zn,Cd,Cu)系列催化剂,并将制得的催化剂用于常压下氢、氧直接合成过氧化氢的反应。考察了M的类型及负载量对M-Pd/TS-1催化剂催化性能的影响。结果表明,M选Ce时,催化剂的性能最好。Ce的最佳掺入量,n_(Ce)/(n_(Ce)+n_(Pd))=0.5%。对Ce改性与未改性的催化剂进行了TEM及静态化学吸附分析,结果表明,掺入Ce可使Pd在TS-1分子筛表面的粒度及分散度得到改善。考察了n_(O_2)/n_(H_2)比,气体流量,反应时间等反应条件对H_2转化率、H_2O_2选择性及收率的影响。在相对优化的工艺条件下,即n_(O_2)/n_(H_2)=3,气体流量为25 mL·min~(-1),反应时间为3 h时,H_2O_2,的收率可达到25.7%,TOF值为18.7 mol·mol~(-1)·h~(-1),此时溶液中H_2O_2的质量百分数为0.8%。     

Effect of LaFeO3 Decoration and Ozone Treatment on Thermal Stability of Au/Al2O3 for CO Oxidation

The 1.1%Au/LaFeO_x/Al₂O₃ catalysts were prepared by the iso-volume impregnation method and activated with H₂ or O₃. The catalytic performance for CO oxidation at room temperature was investigated by accelerated deactivation tests in 1.0% CO reactant stream at 550 °C. The introduction of La and Fe enhanced the thermal stability of Au/Al₂O₃ with a decrease in initial activity, probably due to the formation of LaFeO₃ perovskite on the Al₂O₃ surface. The 1.1%Au/2%LaFeO₃/Al₂O₃ catalyst activated by H₂ can transform 65% CO into CO₂ at room temperature after pretreatment in 1.0% CO reactant stream at 550 °C for 2 h, whereas 1.1%Au/Al₂O₃ activated by H₂ totally loses its activity. O₃ activation can always make 1.1%Au/LaFeO₃/Al₂O₃ more active than that of H₂ activation during the pretreatment process in 1.0% CO. After pretreatment for 10 h, 1.1%Au/2%LaFeO₃/Al₂O₃ activated by O₃ still shows 40% conversion of 1.0% CO at room temperature, whereas those activated by H₂ become inactive completely. The better thermal stability of the catalysts activated by O₃ may be due to that O₃ activation leads to the formation of partially oxidized state of Au in Au/FLA-O₃, which may reinforce the interaction between the metal and support.     

P改性对Mo-Ni/Al2O3煤焦油加氢脱氮性能的影响

在磷含量1.34%下,采用分步浸渍法按磷添加顺序不同制备了3种改性催化剂:MoP-Ni/Al₂O₃、Mo-NiP/Al₂O₃、Mo-Ni/PAl₂O₃.通过X射线衍射(XRD)、程序升温脱附(NH₃-TPD)、程序升温还原(H₂-TPR)、氮气吸附等技术对催化剂进行了表征.以新疆中低温煤焦油为原料,考察了不同磷改性方式对催化剂加氢脱氮(HDN)性能的影响.结果表明,适宜的磷添加方式能够改变催化剂的酸性分布,提高10~13 nm加氢脱氮有效孔的比例,并且减弱活性组分与载体的相互作用,同时使得活性组分更易被还原,进而提高催化剂加氢脱氮性能.加氢脱氮活性顺序为Mo-Ni/PAl₂O₃(74.36%)>Mo-NiP/Al₂O₃(72.74%)>Mo-Ni/Al₂O₃(71.72%)>MoP-Ni/Al₂O₃(56.13%).     

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.     

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.     

Catalytic hydrogenation of C60 fullerene

Catalytic hydrogenation of C₆₀ with H₂ or by hydrogen transfer reactions using Pd/SiO₂, Rh/Al₂O₃ and Ru/Al₂O₃ has been studied. The final products containing partially hydrogenated C₆₀ fullerence C₆₀H₄₂–C₆₀H₄₆ were characterized by FTIR, UV and NMR methods.     

浸渍法制备的Pd-MnO_x/γ-Al_2O_3催化剂及不同载体对地表O_3降解的影响(英文)

在γ-Al2O3载体上用等体积浸渍法浸渍Pd、MnOx活性组分,然后涂覆于堇青石基体上制备Pd-MnOx/γ-Al2O3整体式催化剂.分别用X射线衍射(XRD)、H2-程序升温还原(H2-TPR)、低温N2吸附-脱附及X射线光电子能谱(XPS)对制备的催化剂进行表征.研究了Pd、MnOx浸渍顺序对催化剂活性、氧化还原性能及织构性质的影响.实验结果表明,Pd、MnOx共浸渍较分别浸渍制备的催化剂活性好,Pd和MnOx之间存在一定的协同作用.考察了不同载体如La-Al2O3、SiO2、γ-Al2O3和Zr-Al2O3对催化剂活性、氧化还原性能、织构性质及表面电子性能的影响.研究表明,以La-Al2O3或SiO2为载体的催化剂活性最好,即,14°C时O3转化率为82%,完全转化温度为36°C.γ-Al2O3载体次之,Zr-Al2O3载体较差.不同载体制备的催化剂中MnOx的氧化还原性能顺序为:PdMnOx/SiO2Pd-MnOx/La-Al2O3Pd-MnOx/γ-Al2O3Pd-MnOx/Zr-Al2O3.     

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.     

ZrO4/SiO2-Al2O3催化肉桂醛MPV转移加氢性能

以九水合硝酸铝（Al（NO₃）₃·9H₂O）与正硅酸乙酯（TEOS）为前驱盐,采用溶胶-凝胶法制备一系列不同Al₂O₃含量的SiO₂-Al₂O₃复合氧化物,并通过浸渍硝酸氧锆引入ZrO₂,制备ZrO₂/SiO₂-Al₂O₃复合氧化物催化剂,考察催化剂在肉桂醛（CAL）MPV转移加氢中的催化性能,并结合N₂物理吸附、X射线粉末衍射（XRD）、傅里叶变换红外光谱（FTIR）、NH₃-程度升温脱附（NH₃-TPD）、Py-原位红外（Py-IR）等技术,研究催化剂结构、织构以及表面性质与其催化性能间的构效关系.研究表明,所制备的催化剂均以L酸为主,并含有少量B酸中心,这使得加氢产物以肉桂醇（COL）为主,并含有少量1-苯丙烯-2-丙基醚（CPE）.Al₂O₃含量不仅影响催化剂表面的酸中心数量,而且对催化剂的织构参数有较大影响.随Al₂O₃含量的增加,催化剂表面L酸与B酸中心均有所增加,而孔径则持续变小,这使得催化反应呈现CAL转化率先增加后减少、目标产物COL选择性先稍有减小后有所增加的趋势.在Si/Al比为2时,催化剂具有最优的催化性能,优化反应条件下,CAL转化率达96%,目标产物COL选择性达90%.     

Reducibility of Mo species in Pt/MoO3 and PtMo/Al2O3 catalysis

Recucibility of Mo species in Pt/MoO₃ and PtMo/Al₂O₃ has been investigated by temperature-programmed reduction (TPR), temperature-programmed desorption of hydrogen (H₂-TPD) and temperature programmed electronic conductivity (TPEC) techniques. In Pt/MoO₃ at H₂ atmosphere, it was found by TPEC and TPR that, a slight amount of Pt could activate the transfer of the species and H atoms between H₂ and MoO₃, and thus accelerate the reduction of MoO₃. In PtMo/Al₂O₃, TPR and H₂-TPD revealed that the reduction of surface Mo species could also be facilitated by Pt. Two kinds of hydrogen molybdenum species were proposed on the surface of the catalyst after prereduction.     

Fischer-Tropsch synthesis over Ru/Al2O3 catalysts

Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al₂O₃ catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature, synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al₂O₃ was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction.