Ni基催化剂在邻甲酚原位加氢反应中的催化性能

采用等体积浸渍法制备了一系列负载型Ni基催化剂,利用XRD、H₂-TPR、NH₃-TPD 等技术表征了催化剂的理化特性,考察了载体(CMK-3、SiO₂ZrO₂、MgO、Al₂O₃)、助剂(Cu、Ce、Fe)对Ni基催化剂理化特性的影响,测试了230 oC、0.1 MPa冷压下催化剂对邻甲酚原位加氢反应的性能．结果表明,在负载型镍基催化剂作用下,甲醇水相重整制氢反应可以与邻甲酚的原位加氢反应相耦合;以CMK-3为载体的催化剂活性明显优于其他三种载体,邻甲酚的转化率为45.35%;助剂的添加对催化剂性能影响显著,Fe 的引入使原位加氢体系的转化率降至40.49%,助剂Ce、Cu的加入提高了Ni/CMK-3催化剂的原位加氢反应性能,转化率分别提高至64.6%、66.8%,Cu的添加改变了产物的分布,在产物中出现了新产物甲苯;同时探讨原位加氢反应路径及反应机理．     

Experimental and Theoretical Study of Hydrogen Atom Abstraction from C2H6 and C4H10 by Zirconium Oxide Clusters Anions

使用配有团簇产生和化学反应源的飞行时间质谱装置,研究了锆氧阴离子团簇Zr_xOy^-与乙烷和丁烷的反应. 在反应中发现了Zr₂O₅H^-和Zr₃O₇H^-产物. 用密度泛函理论研究了乙烷在Zr₂O₅^-上的反应通道,发现乙烷脱氢反应可以发生,从而证明观察到的产物是源于脱氢反应. 该工作揭示了锆氧负离子团簇与烷烃反应中的新通道.     

焙烧温度对Ni/CuO-ZrO2-CeO2-Al2O3催化剂在甲烷自热重整反应中积炭行为的影响

以Na₂CO₃为沉淀剂,在pH=9时,采用并流沉淀法制备了Ni/CuO-ZrO₂-CeO₂-Al₂O₃催化剂,催化剂中活性组分Ni的负载量(质量分数)为10%．采用TPO、SEM和XPS等方法研究了载体焙烧温度对催化剂积炭行为的影响．结果表明,载体焙烧温度为800 oC制备的Ni/CuO-ZrO₂-CeO₂-Al₂O₃催化剂不存在高温烧炭峰,可以避免由于积炭而降低反应的活性．反应40 h后,催化剂表面出现表面碳酸盐和非活性丝状积炭,这些物种可能会导致催化剂活性降低．     

瞬态磷光发射光谱研究阿替洛尔与单线态氧反应的动力学

药物活性化合物阿替洛尔是一种β受体阻滞剂,若将其排放到地表水资源中会对人类健康和生态系统产生不利的影响. 受光驱动的直接光降解以及间接光降解法可以有效去除环境中的阿替洛尔. 在间接光降解方法中,¹O₂是降解阿替洛尔这类污染物的重要活性物种. 然而,关于阿替洛尔与¹O₂反应动力学的信息还比较缺乏,二者间的反应速率常数仍存在争议. 本文通过直接观察¹O₂在1270 nm处衰减动力学来研究阿替洛尔与¹O₂在不同溶剂中的反应速率常数：在重水中为7.0×10⁵ (mol/L)^-1·s^-1,在乙腈中为8.0×10⁶ (mol/L)^-1·s^-1,在乙醇中为8.4×10⁵ (mol/L)^-1·s^-1. 在极性强、给氢能力弱的溶剂中阿替洛尔与¹O₂的反应速率常数更大. 这些结果对光降解阿替洛尔等β受体阻滞剂提供相关动力学信息.     

焙烧温度对SiO2负载的Co3O4纳米粒子表面氧缺陷浓度和CO氧化催化性能的影响

以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co₃O₄/SiO₂催化剂．通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构．在所有的催化剂中,XRD和Raman光谱都只检测到了Co₃O₄晶相的存在．与Co₃O₄体相相比,XPS结果表明在200 oC焙烧的(Co₃O₄(200)/SiO₂)催化剂中Co₃O₄表面上存在着过量的Co²⁺．与XPS的结果一致,TPR结果表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄表面上存在氧缺陷, 并且XAFS结果也表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄具有更多的Co²⁺．提高焙烧温度使得过量的Co²⁺进一步氧化为Co³⁺,同时降低了表面氧缺陷浓度,从而得到计量比的Co₃O₄4/SiO₂催化剂．在所有的负载催化剂中Co₃O₄(200)/SiO₂催化剂表现出了最好的CO氧化催化性能,表明过量Co²⁺和表面氧缺陷的存在能够促进Co₃O₄催化CO氧化反应的活性.     

Experimental and Theoretical Study of Hydrogen Atom Abstraction from Ethylene by Stoichiometric Zirconium Oxide Clusters

使用配有团簇产生和化学反应源的飞行时间质谱装置,研究了锆氧阳离子团簇Zr_xO_y⁺和乙烯的反应. 在这个反应中,发现了产物(ZrO₂)_xH⁺ (x=1～4). 使用密度泛函理论研究了乙烯在Zr₂O₄⁺上的反应通道,发现除了通常的氧转移反应外,乙烯脱氢反应也可以发生,从而支持观察到的产物(ZrO_{2相似文献}   

锰氧化物团簇正离子与硫化氢反应的实验与理论研究 (cited: 2)

采用激光溅射法制备了同位素标记的氧化锰团簇正离子Mn_m¹⁸O_n⁺,并研究了其在快速流动反应管中与硫化氢在热碰撞条件下的反应,氧化锰团簇正离子与硫化氢反应前后的质量分布与强度变化由飞行时间质谱仪检测．实验表明,绝大多数氧化锰团簇正离子可与硫化氢发生氧-硫交换反应产生水分子,反应通式为：Mn_m¹⁸O_n⁺+H₂S→Mn_m¹⁸O_n-1S⁺+H₂¹⁸O．通过密度泛函理论计算了氧化锰团簇正离Mn₂O₂⁺、Mn₂O₃⁺和Mn₂O₄⁺与H₂S反应的机理,结果显示,在这些反应体系中氧-硫交换反应通道同时具有热力学和动力学优势,印证了实验中观察到的现象．气相团簇研究发现的氧-硫交换反应与相关凝聚相体系反应结果一致     

Cr2O3催化合成气转化至甲醇的微观动力学研究

Cr₂O₃是双功能催化合成气转化的重要氧化物组分,其可将合成气转化为重要的中间物种甲醇. 结合密度泛函理论计算和微观动力学模拟,本文系统研究了干净Cr₂O₃(001)和(012)表面,以及氢覆盖或含有氧空位的还原(012)表面的结构及催化合成气转化至甲醇的活性. 本文探讨了合成气转化为甲醇的分步或协同反应路径,并确定CO或CHO氢化是决速步骤. 微观动力学分析表明,Cr₂O₃(001)表面难以催化合成气转化为甲醇,在673 K 时,两个还原性(012)表面的反应速率(25∽28 s^-1)比干净的(012)表面(4.3 s^-1)高出约五倍. 计算结果表明了Cr₂O₃表面还原性对催化活性的重要性,或许可以为双功能催化体系中氧化物组分的设计提供参考.     

Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

利用沉积沉淀法制备出了La改性Al₂O₃催化剂,研究不同焙烧温度对La改性Al₂O₃催化剂用于乙炔气相氢氟化合成氟乙烯反应性能的影响．利用NH₃-TPD、Pyridine-FTIR、XRD和Raman等技术对不同温度焙烧的催化剂进行表征,发现焙烧过程能改变催化剂结构的同时也能调变催化剂表面的酸量．经400 °C焙烧的催化剂显示出最高的乙炔转化率(94.6%)、最高的氟乙烯选择性(83.4%)和较低的积炭选择性(0.72%)．催化剂的高活性与其表面的高酸量有关,同时积炭的选择性也与其表面的酸中心数量有关．     

分级多孔Cafe2O4/C的合成及其微波催化活性

以天然木棉为模板,利用造孔及纳米颗粒自组装两步法合成了分级多孔的Cafe₂O₄/C复合催化剂. Cafe₂O₄/C复合催化剂保留了木棉模板的中空纤维形貌,且该中空纤维是由碳及均匀分布在碳表面的Cafe₂O₄纳米颗粒组成. 该复合催化剂具有较强的甲基紫微波催化降解活性. 研究了Cafe₂O₄负载量、微波功率、催化剂用量、甲基紫的初始浓度和pH值对微波诱导甲基紫降解的影响. 结果表明,Cafe₂O₄/C微波降解甲基紫的催化反应具有较高的反应速率和较短的反应时间. 其降解反应符合一级动力学模型. Cafe₂O₄/C 高的催化活性得益于催化反应和吸附特性之间的协同作用.     

Hydrogenolysis of methylcyclopentane over the bimetallic Ir-Au/γ-Al2O3 catalysts

The gas-phase hydrogenolysis of methylcyclopentane (MCP) was investigated over the bimetallic Ir-Au/γ-Al₂O₃ catalysts. The bimetallic systems containing the atomic Au/Ir ratios in the range of 0.125-8 and a fixed total metal content of 8 wt.%, were prepared by the sequential impregnation (SI) and co-impregnation (CI) methods. The corresponding monometallic Ir/γ-Al₂O₃ and Au/γ-Al₂O₃ catalysts were also prepared. The materials were characterized by ICP, XRD, N₂ adsorption, TEM, and H₂ chemisorption. Highly dispersed Ir nanoparticles were obtained in all cases, while the size of Au nanoparticles increased (up to 50 nm) upon the increasing Au content in the catalyst. The monometallic gold catalyst did not adsorb H₂. The incorporation of Au increased the amount of irreversible adsorbed H₂ in the Ir-Au/γ-Al₂O₃ catalysts with respect to the monometallic ones. The products obtained in the MCP hydrogenolysis were 2-methylpentane (2-MP), 3-methylpentane (3-MP) and n-hexane (n-H). The initial rate (molecules of MCP reacted s⁻¹ g_Ir⁻¹) increased with the Au content. The deactivation was lower for bimetallic catalysts, particularly for the CI ones. The addition of Au played a significant effect on chemisorption and catalytic properties of Ir.     

利用多元醇共浸渍促进Ni/MCM-41催化剂的萘加氢活性

研究了利用乙二醇、甘油、木糖醇、山梨醇、葡萄糖多元醇共浸渍方法促进Ni负载在MCM-41载体上的萘加氢活性．和传统的浸渍方法比较,只要在硝酸盐的水溶液中添加适合量的多元醇即可以提高金属活性中心和载体表面的相互作用,导致5 nm以下超细NiO粒子的形成,以及高分散的催化活性中心和异常高的催化活性;零价Ni的纳米粒子从36.1 nm减少到5 nm以下,同时萘的加氢活性取决于零价Ni纳米粒子的大小．利用多元醇共浸渍制备的负载型催化剂表现出优异的催化活性,即使在55 oC的低温环境中亦表现出100%的萘转化率．     

NiAg Catalysts for Selective Hydrogenolysis of the Lignin C–O Bond

Several bimetallic NiAg catalysts for the lignin hydrogenolysis reaction are evaluated. NiAg catalysts are either prepared by wet chemical reduction, in which a mixture of AgNO₃ and Ni(NO₃)₂ or a mixture of AgOAc and Ni(OAc)₂ is reduced by NaBH₄ and stabilized by polyvinylpyrrolidone in water, or by the decomposition–precipitation method to obtain NiAg/SiO₂. These three catalysts exhibit distinct performances in hydrogenolysis of a lignin β‐O‐4 model compound. For colloidal catalyst from co‐reduction of AgOAc and Ni(OAc)₂, separate growths of Ag and Ni nanoparticles (NPs) are observed, and the system exhibits an undesired selectivity of 31.5% toward dimer products. On the other hand, NiAg NPs are dominant after the reduction of nitrate precursors, although the NP size is not sufficiently small (6.7 nm), resulting in high selectivity but a low reaction rate (12.6% conversion with 12.1% monomers yield). Bimetallic NiAg active phase with excellent dispersion (≈1.5 nm) is obtained on NiAg/SiO₂, which enables 72.7% substrate conversion and 65.6% yield of target monomer compounds. From these results, NiAg bimetallic catalyst is indeed superior to monometallic Ni in lignin hydrogenolysis, however, the formation of bimetallic NiAg catalyst is highly sensitive to the preparation conditions—proper selection of precursors, reductant, and support/stabilizer are all crucial.     

Highly Efficient Bifunctional Catalyst of NiCo2O4@NiO@Ni Core/Shell Nanocone Array for Stable Overall Water Splitting

Electrochemical splitting of water is an efficient way to produce clean energy for energy storage and conversion devices. Herein, 3D hierarchical NiCo₂O₄@NiO@Ni core/shell nanocone arrays (NAs) are reported on Ni foam for stable overall water splitting with high efficiency. The architecture and composition of the 3D catalysts are particularly tuned. The outstanding structural and component features of the as‐prepared 3D catalysts are characterized by the vertically grown NiCo₂O₄ nanocone/NiO nanosheet core/shell structure and Ni decorated 3D‐conductive networks, which largely prompt the catalytic performance. The hybrid catalyst with core/shell nanocone array structures exhibits superior bifuncational activities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with an overpotential of 240 and 120 mV at a current density of 10 mA cm^?2, respectively. The Tafel slope of the optimal 3D electrode is about 43 and 58 mV dec^?1 in an alkaline electrolyte for OER and HER, respectively. An alkaline electrolyzer constructed by two symmetric NiCo₂O₄@NiO@Ni electrodes delivers splendid activity toward overall water splitting with a current of 10 mA cm^?2 at only ≈1.60 V and almost no deactivation after 10 h. This work provides a promising strategy to design ternary core/shell electrodes as high performance Janus catalysts for overall water splitting.     

In situ observation of Ni–Mo–S phase formed on NiMo/Al2O3 catalyst sulfided at high pressure by means of Ni and Mo K‐edge EXAFS spectroscopy

To obtain direct evidence of the formation of the Ni–Mo–S phase on NiMo/Al₂O₃ catalysts under high‐pressure hydrodesulfurization conditions, a high‐pressure EXAFS chamber has been constructed and used to investigate the coordination structure of Ni and Mo species on the catalysts sulfided at high pressure. The high‐pressure chamber was designed to have a low dead volume and was equipped with polybenzimidazole X‐ray windows. Ni K‐edge k³χ(k) spectra with high signal‐to‐noise ratio were obtained using this high‐pressure chamber for the NiMo/Al₂O₃ catalyst sulfided at 613 K and 1.1 MPa over a wide k range (39.5–146 nm^?1). The formation of Ni–Mo and Mo–Ni coordination shells was successfully proved by Ni and Mo K‐edge EXAFS measurement using this chamber. Interatomic distances of these coordination shells were almost identical to those calculated from Ni K‐edge EXAFS of NiMo/C catalysts sulfided at atmospheric pressure. These results support the hypothesis that the Ni–Mo–S phase is formed on the Al₂O₃‐supported NiMo catalyst sulfided under high‐pressure hydrodesulfurization conditions.     

Hydrogen-Water Deuterium Exchange Reaction Over Mixed Oxide Supported Nickel Catalysts

Three series of catalysts, Ni/Al₂O₃-SiO₂, Ni/Al₂O₃-Cr₂O₃ and Ni/SiO₂-Cr₂O₃, were prepared by co-precipitation. In all samples the nickel content was kept constant at 70 at.% Ni, while the support composition was varied. The nickel surface areas, which are required to measure the specific catalytic activities, were determined by hydrogen chemisorption. In the case of the single oxide supported nickel catalysts, the order of the specific catalytic activity values was: Ni/Cr₂O₃<Ni/Al₂O₃<Ni/SiO₂. The specific catalytic activity of the Ni/Al₂O₃-SiO₂ samples, as a function of the support composition, follows approximately the weighted sum of the specific activities of the single oxide supported nickel catalysts. The specific catalytic activity value of the Ni/Al₂O₃-Cr₂O₃ and Ni/SiO₂-Cr₂O₃ samples more closely resembled that of Ni/Cr₂O₃ catalyst. The presence on chromia surface of the chromic anhydride and its tendency to spread onto are supposed to be the cause of this behaviour. Due to their enhanced activity, the Ni/Al₂O₃-Cr₂O₃ catalysts can be used for the production and detritiation of heavy water.     

二氧化硅改性分子筛催化生物质基多元醇制备对二甲苯

本文证明了在二氧化硅改性的分子筛催化作用下,生物质基多元醇(如山梨醇、木糖醇、赤藓糖醇、甘油和乙二醇)可以经过催化裂解、烷基化和异构化等反应,生成高附加值的化学品(对二甲苯).与HZSM-5分子筛催化剂相比,二氧化硅改性的分子筛降低了分子筛催化剂的外表面酸和孔径,从而显著的提高对甲苯的选择性和产率.本文详细讨论了催化剂、甲醇添加剂、反应温度和不同类型多元醇原料对对二甲苯选择性和产率的影响.甲醇的添加促进多元醇催化裂解中的烷基化反应,提高了二甲苯的产率.在15%SiO_2/HZSM-5催化剂作用下,对二甲苯的产率最高可达到10.9 C-mol%,对二甲苯在二甲苯中选择性达到91.1%.本文通过研究相关重要反应和催化剂特性,揭示了生物质基多元醇催化裂解制备对二甲苯的反应路径.     

Peak overlaps and corresponding solutions in the X-ray photoelectron spectroscopic study of hydrodesulfurization catalysts

Al₂O₃-SiO₂-based Co(Ni)-Mo(W)-S catalysts are widely investigated hydrodesulfurization (HDS) catalysts in recent decades. XPS is a suitable technique to detect the surface properties of HDS catalysts. Typical overlapping spectra in the XPS analysis of HDS catalysts, such as Mo3d and S2s, Si2p and bremsstrahlung-induced Al KL₂₃L₂₃ using nonmonochromatic AlKα source, W4f and W5p_3/2, as well as the disturbance of Auger lines on Ni2p and Co2p, are carefully studied in the present paper. Besides, effective methods to overcome the influence of peak overlaps are illustrated. These results would provide basic and important information in interpreting XPS results of HDS catalysts.