Selectivity in the Phase Transfer Catalytic Hydrogenation of Nitrobenzene by Transition VIII Metals

The phase transfer hydrogenation of nitrobenzene to p-aminophenol has been investigated for the catalysts Pt, Pd, Rh and Ru. The influence of factors such as surfactant concentration, sulfuric acid concentration, hydrogen pressure and temperature on the reaction was determined. It was found that the rate-determining step for the catalytic hydrogenation of nitrobenzene is the catalytic process by which the hydrogen atom is absorbed on the metal surface. A reaction model is suggested which accounts for the observed hydrogenation selectivity and explains how these factors affect product composition and yield. It is shown that Pt favors p-aminophenol production, while Pd favors aniline production.     

量子机器学习在催化化学研究中的应用

量子机器学习融合了量子化学与机器学习的优点,具有比传统密度泛函理论更快的计算速度和更高的准确性.量子机器学习可为复杂、多维、多尺度的催化化学提供更智能和有效的研究方式,通过训练可靠的数据及建立合理的模型和算法,快速、准确地预测最优的催化剂设计参数、最佳的催化剂材料的合成方法和反应条件、以及催化剂结构和性能之间的关系.作者就量子机器学习应用于催化材料的设计、催化反应性能和催化反应机理三方面的发展趋势进行了概述.     

Structural,textural and catalytic properties of pure and Li-doped NiO/Al2O3 and CuO/Al2O3 catalysts

Pure and Li-doped NiO/Al₂O₃ and CuO/Al₂O₃ catalysts were prepared to contain 2, 4 and 8 wt.% of Ni and Cu, respectively. The structural properties were determined using DTA, XRD and FTIR techniques, and the textural properties of the catalysts were determined from their adsorption–desorption isotherms of nitrogen at 77 K. The chemisorption of hydrogen at 473–823 K with the pre-reduced catalysts was measured. The data obtained allowed the determination of the metal surface area, S (m²/g); the percentage of metal distribution, R; and the diameter of metal crystallite, d (nm). The amount of surface acidity, measured in mmol/g, was determined from the amount of chemisorbed pyridine necessary to completely inhibit the catalytic dehydration (DHD) of isopropanol. The conversion of isopropanol at 533–623 K was investigated using the micro-catalytic pulse technique. DTA, XRD and FTIR indicated that NiO and CuO exist as separate phases with crystallite sizes too small to be detected. No evidence has been gathered to indicate the existence of an aluminate phase.With the increase of metal loading, the surface area decreased whereas the total pore volume and the mean pore radius increased. Conversion of iso-propanol to propene proceeded via (DHD) on surface acid sites, and conversion of isopropanol to acetone proceeded via dehydrogenation (DHG) on redox sites. DHD and DHG exhibited first-order kinetics, and the rates of both reactions increased with temperature, with the latter being more temperature-dependent.     

Catalytic Systems for the H<Subscript>2</Subscript>S Wet Oxidation at room Temperature

The catalytic wet oxidation process is the most attractive process for small-scale hydrogen sulfide (H₂S) removal from natural gas. The catalytic wet oxidation process is anticipated to be cost effective and simple so that it can be used for treating sour gases containing small amounts of H₂S and can be easily operated even in isolated sites. The development of effective catalyst is the key technology in the wet catalytic oxidation of H₂S. The scale of operation for the process has to be flexible so its use will not be limited by the flow rates of the gas to be treated. The heterogeneous catalytic wet oxidation of H₂S has been attempted on activated carbons, but the H₂S removal capacity still shows the low removal efficiency. The catalytic wet oxidation of H₂S was studied over Fe/MgO for an effective removal of H₂S. In order to develop a sulfur removal technology, one has to know what surface species of catalyst are the most active. This article discusses the following systematic studies: (i) the catalytic preparation to disperse Fe metal well on MgO support for enhancing H₂S removal capacity, (ii) the effect of the catalytic morphology on the activity of Fe/MgO for the H₂S wet oxidation, (iii) the influence of precursor and support on the activity of Fe/MgO for catalytic wet oxidation of H₂S to sulfur.     

Synthesis, crystal structures and catalytic abilities of new macrocyclic bis-pyridineamido Mn and Fe complexes

A new macrocyclic ligand H₂L (H₂L = 1,2-[bis(6′-pyridine-2′-carboxamido)-ethane]benzene) has been designed and synthesized by condensation of pyridine-carboxylic acid and diamine. Its Mn(III) and Fe(III) complexes, [Mn(L)Cl (DMF)] and [Fe(L)Cl], were prepared and respectively characterized by IR, UV-Vis, ESI-Mass, elemental analysis and X-ray single crystal diffraction. The catalytic abilities of them were examined, and up to 95% yield was achieved in epoxidation of styrene. The preliminary investigation of catalytic mechanism by manganese complex was carried out, suggesting the involvement of Mn(V) oxo species during catalysis.     

磷酸镁铝分子筛的交换与催化性能研究

用红外与程序升温脱附氨法考察了磷酸镁铝分子筛的酸性,测定了94℃时Ni~(2+)与其进行离子交换的等温线,并在不同温度考察交换上Ni~(2+)后分子筛的催化加氢、裂解活性。     

Investigated aerobic oxidation of aminochlorophenol catalyzed by phthalocyanine complexes

The synthesis of 9-Octadecenamide substituted Fe(II) phthalocyanine (ODAFePc) and Ni(II) phthalocyanine (ODANiPc) complexes from Fe(II) tetracarboxylic acid phthalocyanine (FeTcPc) and Ni(II) tetracarboxylic acid phthalocyanine (NiTcPc) with 9-Octadecenamide. These complexes have high molecular weight and soluble in organic solvents. The complexes have been confirmed by FTIR, Mass spectroscopy, UV–Visible X-ray diffraction, and thermogravimetric analysis. The synthesized complexes exhibit excellent stability and are catalytically active in 2-amino-4-chlorophenol (ACP) oxidation. The new method was used for the determination of the oxidation of phenol by applying different experimental parameters like concentration, catalytic quantity, temperature, and pH to get a good yield and catalytic activity of ODAFePc and ODANiPc were studied. ACP was oxidized by dissolved oxygen with ODAFePc and ODANiPc as a catalyst and immediately combined with 4-aminoantipyrine (4-AAP) to form a pink dye and was determined by appearance of absorption intensity at 580 ​nm. All the experimental results show that ODAFePc and ODANiPc complexes exhibit good catalytic behavior on oxidation of 2-amino-4-chlorophenol.     

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics,efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al₂O₃ was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O₂^–, and ¹O₂), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al₂O₃ catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ～ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ～ 0.032$/m³, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al₂O₃ exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.     

异质哑铃型纳米颗粒合成中的关键因素(英文)

哑铃型纳米颗粒由一种包含强相互作用的异质结构成,它两端是不同物质的纳米颗粒.这两种不同功能的纳米颗粒紧密相连,形成一种哑铃形的外观.这种结构的纳米颗粒在电子、磁性、光学及催化等方面有着不同于单一组分纳米颗粒的独特性质,因此受到人们广泛关注.哑铃型纳米颗粒的这些独特性质是由两种物质交界面处的电子转移引起的,得益于较强的界面相互作用,两种物质都可以通过界面处的电子转移得到改良,使得这种结构的催化剂在较低温度下催化氧化有机废气时活性很高.以CO氧化反应为例,Au纳米颗粒通常情况下对该反应没有催化活性,但是被负载到金属氧化物上面以后,却表现出了很高的催化活性.这正是氧化物载体与Au纳米颗粒之间电子传输的结果.通常在核壳结构中,核心物质以及两种物质的交界面都被外壳所包裹,而哑铃型结构当中的两种物质的功能面以及它们之间活泼的交界面均可以充分地暴露在反应物中,从而极大提升了其催化效果.这种独特的结构优势也在疾病诊断与治疗中的多功能探针上得到了广泛应用.由于哑铃型结构的两种物质的纳米颗粒相对位置是固定的,当用作催化剂时可以发挥出很好的抗烧结性能,还可使这两种物质更协调地均匀分布.因此哑铃型结构催化剂不仅催化活性更高,而且在较高温度下具有较高的稳定性.哑铃型结构可以看作是独立纳米颗粒与核壳型纳米颗粒之间的一种中间状态,它通常是由一种物质的纳米颗粒在另一种种子颗粒上面经过外延生长得到的.这与核壳结构纳米颗粒的合成很相似,但是必须准确地控制成核过程,使得成核可以各向异性地发生在种子颗粒的某一个晶面上.而在核壳结构的合成中,这一成核过程是均匀分布的.所以在制备哑铃型结构纳米颗粒时,很重要的就是要促进非均质成核,同时抑制均相成核.由于哑铃型纳米颗粒的特殊结构,在制备时想要准确控制上述成核条件是非常困难的,所以到目前为止,仅有很少种类的物质可以被制成哑铃型结构,比如Au(Ag,Pt,Pd)-Fe3O4(Co3O4),Au-PbS(PbSe),FePt-CdS和Cu-Ag等,这些物质中大多数都是由贵金属纳米颗粒和磁性纳米粒子组成的.哑铃型纳米颗粒由于受限于物质种类,它在催化氧化方面的应用也被局限在了很少一部分气体上,如CO.而通过其它很多种催化剂已经可以在较低温度(甚至零下数摄氏度)下实现CO催化氧化.因此,哑铃型结构的优势在CO催化氧化中并不能得到很好利用和体现,而用于甲烷等一些在较低温度下更难氧化的气体的催化氧化尚未见报道.这正是由合成多种多样的哑铃型纳米颗粒的巨大困难所致.因此,找到合成哑铃型纳米颗粒的困难所在以及合成过程中的一些重要影响因素非常有意义,这将帮助我们使用更多的物质合成出一些新的哑铃型纳米颗粒,进而利用其高催化活性,使得更多难以氧化的气体在较低温度下被氧化.本文总结了合成哑铃型纳米颗粒时的多种影响因素,并介绍了相关的一些合成方法.种子颗粒的尺寸以及两种颗粒之间的尺寸比例可以影响制备过程中外延生长的可控性,颗粒尺寸以及两种颗粒的尺寸差别越小,反应越容易控制.反应温度和反应时间需要根据反应物的性质进行精确控制才可以得到合适的尺寸以及较好的粒径分布.而两种不同的物质最终能不能形成哑铃型结构则是由很多种因素决定的,比如反应溶剂的极性、两种物质之间的晶格错配度以及反应中所用乳化剂的含量.除此之外,合适的前驱体、氧化还原剂以及操作环境等都可以影响哑铃型纳米颗粒的合成结果     

Combustion of volatile organic compounds over mixed-regime catalytic membranes

Catalytic membranes operating in a mixed permeation regime (i.e., with significant Knudsen and laminar contributions) have been developed. The membranes prepared had wide pores and presented a low pressure drop. After the addition of γ-Al₂O₃ and Pt, the resulting catalytic membranes were active for the combustion of VOCs. Their performance was compared with that of similar catalytic membranes operating under the Knudsen diffusion regime.