Promotion effect of adsorbed water/OH on the catalytic performance of Ag/activated carbon catalysts for CO preferential oxidation in excess H2

Activated carbon (AC) supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation (PROX) in excess H₂ was evaluated. Ag/AC catalysts, after reduction in H₂ at low temperatures (≤200 °C) following heat treatment in He at 200 °C (He200H200), exhibited the best catalytic properties. Temperature-programmed desorption (TPD), X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicated that silver oxides were produced during heat treatment in He at 200 °C which were reduced to metal silver nanoparticles in H₂ at low temperatures (≤200 °C), simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 °C. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H₂00 treatment displayed similar PROX of CO reaction properties to Ag/SiO₂. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.     

V2O5/TiO2催化剂活性组分与载体相互作用研究

制备了一系列负载型V-Ti-O催化剂, 运用现代分析测试手段如BET、TPD、NARP、XRD等进行表征. 研究发现负载于TiO_2上的V_2O_5由于相互作用而使其表面V=O物种选择外露, 载体TiO_2的晶体结构是决定它们之间相互作用的关键因素. 锐铁矿型TiO_2上获得最大V=O暴露的表面V_2O_5浓度显著低于金红石TiO_2载体上获得最大V=O暴露时的表面V_2O_5浓度. 而具有较大比表面及较强酸中心的TiO_2载体导致较强的相互作用. 即可获得较大的表面V=O暴露度.     

MnO_x-CeO_2上表面氧性质及其催化碳烟燃烧性能

运用TPO,XRD,BET,O2-TPD,H2-TPR,XPS等技术,研究了在CeO2中引入不同Mn含量对催化剂表面氧性质的影响,并重点探讨了吸附于氧空位上的原子吸附氧O-与催化碳烟燃烧活性的关联。结果表明:将Mn中引入CeO2后,MnOx-CeO2晶格中可形成较CeO2更多的氧空位,并有利于氧的活化和迁移,生成了较多原子吸附氧O-;MnOx(0.4)-CeO2在碳烟起燃温度区间有最多的原子吸附氧O-,其碳烟起燃活性最高,对应的起燃温度是346℃,比无催化剂时降低了111℃,比CeO2降低了35℃。     

Effect of promoters on the behavior and properties of VPO catalysts for the selective oxidation of n-butane to maleic anhydride

A series of vanadyl pyrophosphate (VPO) modified by several additives has been investigated with the aim to reveal the promotion mechanism of the additives for selective conversion of n-butane to maleic anhydride (MA). Catalyst performance and various physicochemical characterization including XPS, XRD, FT-IR, DTA and BET indicated that the properties of additives, such as electronegativity and ion radius, contributed much to the effect of the additives on the structure and surface characteristics of VPO catalysts, and then influenced the catalytic behavior. The remarkable effects of additives on the surface vanadium and oxygen species were discussed. It was shown that maximum MA selectivity could be found with a moderate V⁵⁺ /V⁴⁺ ratio, and the catalytic activity and selectivity were improved, respectively, with the increase of surface active oxygen species, as well as as their amount and stability.     

常温下 MnO2/Al2O3催化剂催化臭氧氧化甲苯反应

采用浸渍法制备了Al2O3负载的5种过渡金属氧化物催化剂,考察了它们在常温下催化臭氧氧化甲苯的性能,并运用程序升温还原、程序升温氧化、N2吸附-脱附和X射线光电子能谱对催化剂进行了表征.结果表明,NiO/Al2O3,CoO/Al2O3和MnO2/Al2O3催化剂上活性氧中心数量较少,臭氧与甲苯转化率较高;而Fe2O3/...     

Non-Interacting Ni and Fe Dual-Atom Pair Sites in N-Doped Carbon Catalysts for Efficient Concentrating Solar-Driven Photothermal CO2 Reduction

Solar-to-chemical energy conversion under weak solar irradiation is generally difficult to meet the heat demand of CO₂ reduction. Herein, a new concentrated solar-driven photothermal system coupling a dual-metal single-atom catalyst (DSAC) with adjacent Ni−N₄ and Fe−N₄ pair sites is designed for boosting gas-solid CO₂ reduction with H₂O under simulated solar irradiation, even under ambient sunlight. As expected, the (Ni, Fe)−N−C DSAC exhibits a superior photothermal catalytic performance for CO₂ reduction to CO (86.16 μmol g⁻¹ h⁻¹), CH₄ (135.35 μmol g⁻¹ h⁻¹) and CH₃OH (59.81 μmol g⁻¹ h⁻¹), which are equivalent to 1.70-fold, 1.27-fold and 1.23-fold higher than those of the Fe−N−C catalyst, respectively. Based on theoretical simulations, the Fermi level and d-band center of Fe atom is efficiently regulated in non-interacting Ni and Fe dual-atom pair sites with electronic interaction through electron orbital hybridization on (Ni, Fe)−N−C DSAC. Crucially, the distance between adjacent Ni and Fe atoms of the Ni−N−N−Fe configuration means that the additional Ni atom as a new active site contributes to the main *COOH and *HCO₃ dissociation to optimize the corresponding energy barriers in the reaction process, leading to specific dual reaction pathways (COOH and HCO₃ pathways) for solar-driven photothermal CO₂ reduction to initial CO production.     

聚酰胺生产新技术—苯不完全加氢制环己烯的开发研究

本文介绍并评述了由苯不完全加氢制环已烯这一聚酰胺生产的全新技术路线.通过与现存的工艺进行对比分析,阐述了它在工业生产上的巨大应用前景.对其关键步聚苯不完全加氢生成环己烯,从反应工艺、催化剂制备、反应机理及环己烯的分离与应用等几个方面,综述了其历史、现状和未来发展趋势.     

Selective Oxidation of n-Butane over VPO Catalyst Modified by Different Additives

A series of vanadyl pyrophosphate catalyst （VPO） modified by different additives have been prepared with the aim to study the performance for selective conversion of n-butane to maleic anhydride（MA）. The addition of various promoters improved the catalytic performance remarkably on both activity and selectivity. The correlation of activity and selectivity of the catalysts with their structure has been discussed. The increase in BET surface areas and surface redox sites leads to an enhanced activity. However, good selectivity can only be obtained on those surfaces with suitable surface acid sites.     

Immobilizing ultrafine bimetallic PtAg alloy onto uniform MnO_2 microsphere as a highly active catalyst for CO oxidation

Herein, a facile glycol reduction route is successful employed to synthesize bimetallic Pt Ag alloys with homogeneous distribution of sizes and elements. Experimental studies reveal that the ultrafine Pt Ag alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO_2 microsphere,which remarkably enhances the catalytic performances for CO oxidation. Importantly, quasi in-situ X-ray photoelectron spectroscopy(XPS) result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O_2 molecules, and the oxygen vacancy sites could be replenished and excited by gas-phase O_2.     

反应气氛中二氧化硫存在下La_(0.8)K_(0.2)Mn_(0.95)Cu_(0.05)O_3催化剂对碳烟的氧化

利用La0.8K0.2Mn0.95Cu0.05O3氧化模拟碳烟,考察预硫化处理及程序升温氧化中SO2对催化剂性能的影响。采用H2-TPR,FTIR和XPS等方法对催化剂性能进行了表征。XPS表明催化剂在0.02%SO2气氛中400℃下进行4 h的预硫化后OI(O2-)转化为OII(O-),催化剂活性增加;TPO反应中低浓度SO2(0.01%)促进了催化剂的活性,可能是较高温度下高活性K的存在,有效阻止了硫酸盐的生成及积累,对O-的消耗减少。催化剂在0.02%SO2气氛中300℃下预硫化超过1 h以后活性明显降低,预硫化1.5 h后催化剂表面的O2-几乎消耗完全,O-大大减少,二者都转化为O(O2-);可能是较低温度下硫酸盐逐渐积累,加快了O2-的消耗,导致可用的氧源枯竭,催化剂活性降低。