[Mo2O2S2(S2)2][2-]的振动光谱研究

本文测定了原子簇化合物[Mo2O2S2(S2)2][2-]的红外和拉曼光谱,并在乙腈溶液中测得其共振拉曼光谱和退偏振比。利用X光晶体结构数据,对此阴离子的伸缩振动作了简化的正则坐标分析计算。所得结果可以帮助分析和归属一些Mo-Fe-S原子簇化合物的振动光谱。     

Na2WO4·2H2O-H2O2催化氧化苯甲醛制备苯甲酸

以30%H2O2为氧源,Na2WO4·2H2O催化氧化苯甲醛制备苯甲酸.考察了H2O2用量,反应时间,催化剂和酸性添加物(硫酸氢钠)对苯甲酸收率的影响和在非酸性环境下,表面活性剂对苯甲酸收率的影响.结果表明,加入非离子表面活性剂能有效的提高苯甲酸的收率,特别是添加β-环糊精,苯甲酸的收率达90.03%.     

2MgO·2B2O3·MgCl2·14H2O-MgCl2-H2O体系30℃相平衡

用相平衡方法研究2MgO@2B2O3@MgCl2@14H2O在30℃不同质量分数MgCl2水溶液中的溶解转化产物及其溶解度.结果表明,该复盐在MgCl2的质量分数0～2%浓度范围,发生不同步溶解并转化为多水硼镁石(2MgO@3B2O3@15H2O);在MgCl2的质量分数2%～13.8%浓度范围,转化为柱硼镁石(MgO@B2O3@3H2O),这一结果比文献报导的该硼酸盐的形成温度低了13℃,为盐湖硼酸镁矿物柱硼镁石形成的解释提供了物理化学依据;而在MgCl2质量分数大于13.8%时,同步溶解,不发生转化.提出了溶解相转化反应机理.     

PdC_2H_2和PtC_2H_2的键结构研究

关于过渡金属Pd,Pt对C_2H_2的吸附和氢化实验研究前人已作了不少工作,但有关Pd,Pt与C_2H_2之间成键问题的理论研究还尚不多见。为了了解Pd,Pt d轨道对炔键的活化行为和成键特性,本文以MC_2H_2(M=Pd,Pt)为模型,用赝势计算方法,对Pd,Pt与C_2H_2键的相互作用进行了研究。一、计算方法由于重原子的内层轨道对形成分子贡献很小,内层电子的相对论效应极为严重。本文采用Ps—HONDO程序,选取Hay的有效核芯势和价轨道Gaussian基组,对重原子Pd和Pt进行了价电子从头计算,对C和H进行了全电子从头算.部分地消除重原子内层电子相对论效应所引起的误差。     

O2 和 CO 在 Co2B2/TiO2 和 Co2B2Pt/TiO2 表面吸附的密度泛函研究

 采用密度泛函理论探讨了 TiO2 表面负载 Co2B2 和 Co2B2Pt 合金簇可能的负载构型. 结果表明, Co2B2 和 Co2B2Pt 合金簇倾向于以两个 Co 的形式负载在两个氧上. 态密度分析发现, 负载后, Co2B2 合金簇中部分 Co 原子和 B 原子成键加强, Co2B2Pt 合金簇中 Pt 原子和 B 原子成键也加强, 形成新的轨道. CO 和 O2 在 Co2B2/TiO2 和 Co2B2Pt/TiO2 表面吸附的结果表明, Co2B2Pt/TiO2 催化氧化 CO 性能的提高是由于 Pt 原子提高了 Co2B2 合金簇吸附 CO 和 O2 的能力.     

Cl_2 2HI=2HCl I_2反应机理的理论研究

分别在MP2/3-21G!!、CCSD(T)/3-21G!!//MP2/3-21G!!和B3LYP/3-21G!!3种水平上,计算研究了气相反应Cl2 2HI=2HCl I2的机理,求得一系列四中心和三中心的过渡态.通过比较六种反应通道的活化能大小,得到了相同的结论:双分子基元反应Cl2 HI"HCl ICl和ICl HI"I2 HCl的最小活化能小于Cl2、HI和ICl的解离能,从理论上证明了反应Cl2 2HI=2HCl I2将优先以分子与分子作用形式分两步完成.用内禀反应坐标(IRC)验证了MP2/3-21G!!方法计算得到的过渡态.     

五元体系K2+2,Mg2+∥Cl2-2,SO2-4-CO(NH2)2-H2O及其边界四元体系MgSO4-MgCl2-CO(NH2)2-H2O在25 ℃时的等温溶度研究

报道了五元体系K2+2, Mg2+∥Cl2-2,SO2-4-CO(NH2)2-H2O在脲不饱和区及其边界四元体系MgSO4-MgCl2-CO(NH2)2-H2O在25 ℃时的等温溶度研究结果, 绘制了体系等温溶度的盐分组成图、水量图以及饱和溶液的折光率-组成图. 五元体系在脲的参与下, 交互反应K2Cl2+MgSO4→K2SO4+MgCl2向有利于生成硫酸钾和软钾镁矾K2SO4*MgSO4*6H2O(pic.)的方向进行, 这两者的相区较无脲时明显增大.     

Rh2CO2/Al2O3上H2吸附及CO和H2共吸附

CO加氢反应机理一直是许多化学工作者感兴趣的课题．Rh催化剂因其优良的性能而被用于 CO加氢机理研     

Na2O2与NO2不反应吗

通过实验验证,指出了一些期刊涉及Na2O2吸收CO2和NO混合气体的规律性等文章的知识性错误,认为习题训练中应回避此类问题,或是以此问题对学生置疑,引导学生实验探究,进行批判性教学。     

均相催化剂催化氧气氧化生物质制备甲酸

甲酸是一种重要的化工原料,以可再生生物质为原料,通过催化氧气氧化制备甲酸具有重要意义。对于不溶于水的生物质原料的转化,采用可溶于水的均相催化剂体系证明是有效的。本文总结了均相催化剂体系(包括含钒杂多酸、含钒杂多酸+H₂SO₄、含钒杂多酸基离子液体、NaVO₃+H₂SO₄、VOSO₄、NaVO₃-FeCl₃+H₂SO₄、FeCl₃+H₂SO₄等)在催化氧气氧化生物质(包括生物质模型化合物、纤维素、木材、秸秆和玉米芯等)制备甲酸方面的研究,分析了其转化的过程和机理。最后,指出了目前催化氧化生物质制备甲酸存在的问题和挑战。     

离子液体介导CO2化学转化研究进展

The efficient utilization of carbon dioxide (CO₂) as a C1 feedstock is of great significance for green and sustainable development. Therefore, the efficient chemical conversion of CO₂ into value-added products has recently attracted a lot of research attention in recent years. The transformation of CO₂ generally requires high-energy substrates, specific catalysts, and harsh reaction conditions due to its high thermodynamic stability and kinetic inertness. Consequently, several efforts have been dedicated toward the development of high-performance catalysts and new reaction routes for CO₂ conversion over the last few decades. To date, many routes of convert CO₂ into value-added chemicals have been proposed, together with the development of heterogeneous and homogeneous catalysts. Among the advanced catalysts reported to date, ionic liquids (ILs) have been widely investigated and show great potential for the efficient, selective, and economical conversion of CO₂ into highly valuable products under mild conditions, even under ambient conditions. Some task-specific ILs have been designed with unique functional groups (e.g., —OH, —SO₃H, —NH₂, —COOH, and —C≡N), which can act as the solvent, absorbent, activating agent, catalyst, or cocatalyst to realize the transformation of CO₂ under metal-free and mild conditions. In addition, a variety of catalytic systems composed of ILs and metal catalysts have also been reported for the transformation of CO₂, in which the combination of the IL and metal catalyst is responsible for CO₂ conversion with high efficiency. In this review article, we summarize the recent advances in IL-mediated CO₂ transformation into chemicals prepared via C—O, C—N, C—S, C—H, and C—C bond forming processes. ILs that can chemically capture CO₂ with high capacity are first introduced, which can activate CO₂ via the formation of IL-based carbonates or carbamates, thus realizing the transformation of CO₂ under metal-free and mild conditions. Recent progress in IL-mediated CO₂ transformations to form carbonates and various kinds of N- and S-containing compounds (e.g., oxazolidinones, ureas, benzimidazolones, formamides, methylamines, benzothiazoles, and other chemicals) as well as CO₂ hydrogenation to give formic acid, methane, acetic acid, low-carbon alcohols, and hydrocarbons has been summarized in this review with a focus on the reaction routes, catalytic systems, and reaction mechanism. In these reactions, ILs can simultaneously activate the substrate via strong H-bonding in addition to activating CO₂, and the cooperative effects among the ionic and molecular species and metal catalysts accomplish the reactions of CO₂ with various kinds of substrates to afford a wide range of value-added chemicals. Finally, the shortcomings and perspectives of ILs are discussed. In short, IL-mediated CO₂ transformations provide green and effective routes for the synthesis of high-value chemicals, which may have great potential for a wide range of applications.     

过渡金属催化CO2/H2参与的羰基化研究进展

Ever-increasing energy demands due to rapid industrialization and urban population growth have drastically reduced petroleum reserves and increased greenhouse-gas production, and the latter has consequently contributed to climate change and environmental damage. Therefore, it is highly desirable to produce fuels and chemicals from non-petroleum feedstocks and to reduce the atmospheric concentrations of greenhouse gases. One solution has involved using carbon dioxide (CO₂), a main greenhouse gas, as a C1 feedstock for producing industrial fuels and chemicals. However, this requires high energy input from reductants or reactants with relatively high free energy (e.g., H₂ gas) because CO₂ is a highly oxidized, thermodynamically stable form of carbon. H₂ can be generated through water photolysis, making it an ideal reductant for hydrogenating CO₂ to CO. In situ generation of CO such as this has been developed for various carbonylation reactions that produce high value-added chemicals and avoid deriving CO from fossil fuels. This is beneficial because CO is toxic, and when extracted from fossil fuels it requires tedious separation and transportation. This combination of CO₂ and H₂ allows for functional molecules to be synthesized as entries into the chemical industry value chain and would generate a carbon footprint much lower than that of conventional petrochemical pathways. Based on this, CO₂/H₂ carbonylations using homogeneous transition metal-based catalysts have attracted increasing attention. Through this process, alkenes have been converted to alcohols, carboxylic acids, amines, and aldehydes. Heterogeneous catalysis has also provided an innovative approach for the carbonylation of alkenes with CO₂/H₂. Based on these alkene carbonylations, the scope of CO₂/H₂ carbonylations has been expanded to include aryl halides, methanol, and methanol derivatives, which give the corresponding aryl aldehyde, acetic acid, and ethanol products. These carbonylations revealed indirect CO₂-HCOOH-CO pathways and direct CO₂ insertion pathways. The use of this process is ever-increasing and has expanded the scope of CO₂ utilization to produce novel, high value-added or bulk chemicals, and has promoted sustainable chemistry. This review summarizes the recent advances in transition-metal-catalyzed carbonylations with CO₂/H₂ and discusses the perspectives and challenges of further research.     

简单的配体改变调控钌配合物催化还原CO2的活性：硼基配体的对位效应和Ru―H键的性质

开发高效的催化剂用于催化还原CO₂转化为甲酸和它的盐类已经成为研究的热点,是因为将CO₂转化为C1产物不仅可以解决CO₂的含量升高带来的环境问题,还可以解决化石能源燃烧日趋严重的问题。贵金属配合物催化CO₂转化为甲酸和甲酸盐类是目前这类反应最有效的方式,尤其是Ru、Ir和Rh等贵金属。我们之前的研究结果表明Ir(Ⅲ), Ru(Ⅱ)类配合物催化还原CO₂转化为甲酸盐的活性是由配合物Ru―H键的成键性质决定的。它们能高活性的催化CO₂是由于它们都含有同一种特点的Ru―H键,是由Ru的sd²杂化轨道和H的1s轨道杂化而成的,而且这一特点可以被活性氢的对位配体显著影响。鉴于硼基配体具有强的对位效应,我们基于高活性的均相催化剂Ru(PNP)(CO)H₂ (PNP = 2, 6-二(二叔丁基磷甲基)-吡啶)设计了Ru-PNP-HBcat和Ru-PNP-HBpin,并计算了二者催化还原CO₂的活性。Bcat和Bpin配体是实验上常用的硼基配体。我们的计算结果表明Ru-PNP-HBcat和Ru-PNP-HBpin有比Ru-PNP-H₂更长的Ru―H键、亲核性更强的活性氢,其Ru―H键中的Ru原子的d轨道杂化成分的贡献也比Ru-PNP-H₂的更少。相应地Ru-PNP-HBcat和Ru-PNP-HBpin活化CO₂的能垒比Ru-PNP-H₂低。而且Ru-PNP-H₂、Ru-PNP-HBcat和Ru-PNP-HBpin催化CO₂转化为甲酸盐的能垒分别为76.2、67.8、54.4 kJ∙mol^-1,表明Ru-PNP-HBpin具有最高的催化活性。因此,钌配合物催化还原CO₂的活性可由硼基配体强的对位效应和Ru―H键的成键性质来调控。     

基于单原子催化剂的二氧化碳选择性转化

Industrial revolution has led to increased combustion of fossil fuels. Consequently, large amounts of CO₂ are emitted to the atmosphere, throwing the carbon cycle out of balance. Currently, the most effective method to reduce the CO₂ concentration is direct CO₂ capture from the atmosphere and pumping of the captured CO₂ deep underground or into the mid-ocean. The transformation of CO₂ into high-value chemicals is an attractive yet challenging task. In recent years, there has been much interest in the development of CO₂ utilization technologies based on electrochemical CO₂ reduction, photochemical CO₂ reduction, and thermal CO₂ reduction, and CO₂ valorization has emerged as a hot research topic. In electrochemical CO₂ reduction, the cathodic reaction is the reduction of CO₂ to value-added chemicals. The anodic reaction should be the oxygen evolution reaction, and water is the only renewable and scalable source of electrons and protons in this reaction. There is a plethora of research on the use of various metals to catalyze this reaction. Among these, Cu-based materials have been demonstrated to show unique catalytic activity and stability for the electrochemical conversion of CO₂ to valuable fuels and chemicals. Moreover, the solar-driven conversion of CO₂ into value-added chemical fuels has attracted great attention, and much effort is being devoted to develop novel catalysts for the photoreduction of CO₂, especially by mimicking the natural photosynthetic process. The key step in the photocatalytic process is the efficient generation of electron-hole pairs and separation of these charge carriers. The efficient separation of photoinduced charge carriers plays a crucial role in the final catalytic activity. Compared with CO₂ reduction via electrocatalysis and photocatalysis, thermal reduction is more attractive because of its potential large-scale application in the industry. Heterogeneous nanomaterials show excellent activity in the electrocatalytic, photocatalytic, and thermal catalytic conversion of CO₂. However, nanostructured materials have drawbacks on the investigation of the intrinsic activity of the active sites. In recent years, single-site catalysts have become popular because they allow for maximum utilization of the metal centers, show specific catalytic performance, and facilitate easy elucidation of the catalytic mechanism at the molecular level. Accordingly, numerous single-site catalysts were developed for CO₂ reduction to produce value-added chemicals such as CO, CH₄, CH₃OH, formate, and C₂₊ products. Value-added chemicals have also been synthesized with the aid of amines and epoxides. This review summarizes recent state-of-the-art single-site catalysts and their application as heterogeneous catalysts for the electroreduction, photoreduction, and thermal reduction of CO₂. In the discussion, we will highlight the structure-activity relationships for the catalytic conversion of CO₂ with single-site catalysts.     

硼氢化试剂在二氧化碳还原官能化反应中的研究进展

二氧化碳(CO₂)是一种储量丰富、 廉价易得、 安全的可再生资源, 通过化学转化实现对CO₂的资源化利用, 获得高附加值的能源、 材料及化工产品是达成“二氧化碳减排战略”的重要组成部分. 然而, CO₂在其化学转化中常表现为热力学稳定性和动力学相对惰性, 使其转化效率不高. 因此, CO₂活化转化具有很大的挑战性. 近几年来, 利用CO₂的还原官能化反应制备高附加值的化学品取得了长足的进步. 本文对硼氢化试剂在CO₂分子还原官能团化构筑C—N, C—C, C—O以及C—S键, 合成有用的精细化学结构单元并获得高附加值化学品的研究进行了总结. 硼氢化试剂廉价易得, 对环境污染小, 在使用过程中易于操作, 对CO₂分子的还原效率以及获得的产物纯度和产率都较高.     

Supported bimetallic catalyst Pt-Pb/SiO2 for selective conversion of nitrobenzene to p-aminophenol in pressurized CO2/H2O system

Various supported Pt-Pb bimetallic catalysts were prepared and applied for the catalytic conversion of nitrobenzene to p-aminophenol in the environmentally benign pressurized CO_2/H_2O system.Among the bimetallic catalysts prepared,Pt-Pb/SiO_2 is the best and nitrobenzene could be converted to paminophenol with a selectivity as high as 82% when the reaction was carried out using this catalyst at110 ℃ under 5 MPa CO_2 and 0.2 MPa H_2.     

基于纳米金属的增强效应在CO2电还原反应中的应用进展

将二氧化碳通过电化学方法转化为化工原料再利用,不仅可以有效缓减温室效应,而且可以实现自然界的碳循环,对绿色化学与可持续发展意义重大. 本文简要地介绍了二氧化碳电还原的优势及其基本反应原理并综述了近年来基于纳米金属催化剂的一系列活性增强策略的研究进展. 重点探究了合金效应、界面工程、协同效应、缺陷工程以及载体效应等对纳米金属电催化还原二氧化碳性能的影响及相关反应机理. 基于以上策略,提出未来开发面向工业化应用的二氧化碳电还原催化剂面临的挑战与前景.     

多相催化剂催化二氧化碳加氢合成甲醇的研究进展

近年来,随着空气中二氧化碳含量的不断升高,二氧化碳的催化转化在科研界和工业界受到了广泛关注.非均相催化的二氧化碳加氢合成甲醇是实现二氧化碳资源化利用的重要手段之一,具有良好的应用前景.本文系统概述了非均相催化二氧化碳加氢合成甲醇反应的近期研究进展,重点介绍了金属催化剂和金属氧化物催化剂,对反应机理进行了阐述,并对该领域仍待解决的问题和发展前景进行了展望.     

等离子体技术对CO2甲烷化用Ni/SiO2催化剂的改性作用

采用浸渍法制备了Ni/SiO₂催化剂,应用等离子体技术对催化剂进行改性处理。以CO₂甲烷化为模型反应对催化剂进行活性评价,通过H₂程序升温还原(H₂-TPR)和CO₂程序升温脱附(CO₂-TPD)技术对催化剂进行表征。研究了等离子体技术强化处理对催化剂吸附性能和还原性能的影响。结果表明,与常规焙烧的催化剂相比,等离子体技术改性处理提高了催化剂活性组分的分散度,增加反应活性位并调变了活性位对吸附物种的吸附强度,改进了催化剂的还原性能,CO₂甲烷化反应活性和甲烷的时空产率显著提高。