二氧化碳间接转化制化学品的研究进展

二氧化碳直接利用较为困难, 因此先将其转化为环碳酸酯等二氧化碳衍生物, 进而间接转化为其它化学品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. 本文综合评述了二氧化碳转化为环碳酸酯继而间接利用的近期研究进展, 重点介绍了环碳酸酯的加氢反应、 醇解反应和氨解反应中的均相和多相催化体系, 对反应机理进行了阐述, 并展望了该领域仍待解决的问题和发展前景.     

Efficient Fixation of Carbon Dioxide by Electrolysis Facile Synthesis of Useful Carboxylic Acids

Electrochemical fixation of atmospheric pressure of carbon dioxide to organic compounds is a useful and attractive method for synthesizing of various carboxylic acids. Electrochemical fixation of carbon dioxide, electrochemical carboxylation, organic halides, organic triflates, alkenes, aromatic compounds, and carbonyl compounds can readily occur in the presence of an atmospheric pressure of carbon dioxide to form the corresponding carboxylic acids with high yields, when a sacrificial anode such as magnesium or aluminum is used in the electrolysis. The electrochemical carboxylation of vinyl bromides was successfully applied for the synthesis of the precursor of nonsteroidal anti-inflammatory agents such as ibuprofen and naproxen. On the other hand, supercritical carbon dioxide （scCO2） has significant potential as an environmentally benign solvent in organic synthesis and it could be used both as a solvent and as a reagent in these electrochemical carboxylations by using a small amount of cosolvent.     

Reforming of Carbon Dioxide to Methane and Methanol by Electric Impulse Low-Pressure Discharge with Hydrogen

Basic phenomena of the reduction of carbon dioxide to reusable organic materials including methane and methanol were investigated by using a radio frequency impulse discharge in a low gas pressure range without catalysis. The discharge took place under different discharge parameters such as voltage, gas flow rate, gas-mixing ratio, and gas residence time, where the carbon dioxide was mixed with hydrogen at total gas pressure of 1–10 Torr. Organic materials such as methane and methanol were observed. Carbon monoxide was a major product from carbon dioxide. Methane was the dominant organic species produced by the discharge. The concentration of methane increased with discharge voltage, and its volume fraction attained 10–20% of the products containing carbon that came from carbon dioxide. This fraction was also dependent on the mixing ratio of carbon dioxide and hydrogen. We also observed the formation of methanol, though its fraction was low, a few %, compared with methane.     

Formation of carbon oxides during tobacco combustion: Pyrolysis studies in the presence of isotopic gases to elucidate reaction sequence

During the combustion of tobacco, carbon monoxide is formed by the thermal decomposition of tobacco with primary products such as carbon dioxide and water. These three processes occur in parallel and are interdependent. The temperature ranges over which each process occurs, and their relative importance have been assessed by pyrolysing tobacco in the presence of various isotopically labelled gases. Non-isothermal pyrolyses were conducted at a heating rate of 1.6 K s^?1 up to 1000°C, with the products analysed by mass spectrometer.Pyrolysis in the presence of oxygen-18 indicates that combustion of tobacco starts at 180°C. Carbon dioxide and water are formed by combustion at 180°C, while carbon monoxide is not formed as a combustion product until 460°C. The quantities of carbon monoxide and dioxide formed by thermal decomposition of tobacco above 400°C are significantly reduced by the occurrence of combustion.Pyrolysis in the presence of carbon-13 dioxide or carbon dioxide-18 shows that its major reaction, endothermic reduction to form carbon monoxide begins at 450°C. Pyrolysis in an oxygen-18/carbon-13 dioxide atmosphere has shown that this endothermic reduction of carbon dioxide occurs in parallel with the strongly exothermic oxidising reactions. 30% of the total carbon monoxide formed was produced by thermal decomposition of the tobacco. 36% was produced by combustion of the tobacco, and at least 23% was produced via carbon dioxide. The remainder was produced by an interaction of the carbon dioxide reduction and the oxidation. Similar proportion would be expected inside the reaction zone of a burning cigarette.Pyrolysis in the presence of heavy water has shown that the major reaction of the water is to quantitatively produce carbon monoxide and hydrogen above 600°C. Considerable isotopic exchange reactions also occur. Pyrolysis in the presence of carbon monoxide-18 has shown that carbon monoxide reacts with tobacco to a small extent at temperatures above 220°C mainly to abstract oxygen combined in the tobacco and produce carbon dioxide.A sequence of general chemical steps for the production of the carbon oxides and water during tobacco combustion has been deduced. This is based on the present work together with considerations of previously published studies on graphite and coal reactions.     

Etudes sur les composés organométalliques XIV. Réactivité du tétrabenzyltitane (lère communication)

The reactivity of tetrabenzyltitanium with acetone, benzophenone, butanal, acetyl chloride, butyl acetate, ethyl chloroformate, benzonitrile, propylene oxide, carbon dioxide has been investigated. The results show that tetrabenzyltitanium reacts like benzylmagnesium-chloride. The socalled ‘anomalous reaction’ is observed. Benzonitrile, propylene oxide and carbon dioxide, on the other hand, do not react.     

Contribution of the ligand to the electroreduction of CO2 catalyzed by a cobalt(II) macrocyclic complex

The electrochemical reduction of carbon dioxide using hexa-aza-macrocycles derived from the condensation of 1,10-phenanthroline and its Co(II) complex as an electrocatalyst dissolved in dimethylformamide has been studied by cyclic voltammetry and UV-visible spectroscopy. The ligand does not show catalytic activity and only generates hydrogen when it is reduced under carbon dioxide. The cobalt complex shows electrocatalytic activity toward the reduction of carbon dioxide, generating carbon monoxide and formic acid. Cyclic voltammetry and UV-visible spectroscopy show that the active site for the reduction is the metal center in oxidation state (I), although the reduced cobalt center alone is not enough to promote reduction of the carbon dioxide. Electrolysis at controlled potential shows that only at potentials corresponding to reduction of the ligand (second reduction) does carbon dioxide reduction occur. Cobalt(I) probably reacts with CO₂ forming a non-isolated intermediate which, when reduced, gives CO and formic acid. The second reduction that takes place on the ligand regenerates the catalyst and gives products, thus becoming the rate-determining step of the reaction.     

Evaluation of the transport properties of Poly(3-hydroxybutyrate) and its 3-hydroxyvalerate copolymers for packaging applications

Poly(3-hydroxybutyrate) (PHB) and ist 3-hydroxyvalerate containing copolymers form a family of fully biodegradable polyesters with many potential applications. In this work, the results obtained in our laboratory concerning carbon dioxide, water and organic solvent transport through PHB and three low 3-hydroxyvalerate copolymers are reviewed. Comparison established between the former results and some data taken from the literature, have revealed that PHB and the above mentioned copolymers show transport properties similar to other common thermoplastics such as PVC and PET, particularly in the case of carbon dioxide and water. Consequently, PHB and copolymers can be catalogued as good barrier materials against these penetrants. On the other hand, these biopolymers show a low barrier character against organic compound permeation. All these features conform a good balance of physicochemical properties for these polyhydroxyalkanoates, which may take them suitable for several applications, including its use in biodegradable packaging materials.     

二氧化碳电还原制草酸研究进展

近年来, 二氧化碳过量排放所引发的全球变暖等气候问题引起了全世界的广泛关注, 碳减排已成为人类社会可持续发展面临的共同挑战. 利用电化学方法将二氧化碳转化为高附加值化学品是实现碳减排和二氧化碳高附加值利用的理想途径之一, 但仍面临能耗高、 二氧化碳转化率低、 产物选择性差和难分离等问题. 本文以电还原二氧化碳制草酸为例, 从反应机理、 催化剂、 电解液、 催化电极及反应器等方面介绍该反应的研究进展, 对当前二氧化碳电还原制草酸存在的关键问题进行了分析, 并对其未来研究方向进行了展望.     

Fixed-bed adsorption of carbon dioxide/methane mixtures on silicalite pellets

The adsorption of carbon dioxide and methane on silicalite pellets packed on a fixed bed has been studied. Equilibrium and kinetic measurements of the adsorption of carbon dioxide and methane have been performed, and a binary adsorption isotherm for carbon dioxide/methane mixtures has been obtained. A model based on the LDF approximation for the mass transfer has been used to describe the breakthrough curves obtained experimentally. A PSA cycle has been proposed for obtaining methane with purity higher than 98% from carbon dioxide/methane mixtures containing 38% and 50% methane, and its performance has been simulated using the proposed model. The simulation results show that silicalite can be a suitable adsorbent for employment in a PSA separation process for carbon dioxide removal from coalseam and landfill gases.     

Molecular structure determination of solid carbon dioxide phase IV at high pressures and temperatures based on Møller-Plesset perturbation theory

Carbon dioxide has attracted considerable attention owing to its physics and abundant polymorphs. Despite decades of extensive experiments and theoretical simulations, the structure and properties of carbon dioxide under extreme pressures and temperatures are yet to be properly understood. Particularly, the intermediate phase IV of solid carbon dioxide, which separates the molecular phases at low pressures from the non-molecular phases at high pressures, has not been fully investigated, and its structure remains controversial. Here, based on the second-order Møller-Plesset perturbation (MP2) theory and the embedded fragment method, we study the crystal structure, equation of state, and Raman spectra of solid carbon dioxide phase IV at high pressures and temperatures. We demonstrate that the solid carbon dioxide phase IV is a molecular structure that remains in a molecular state rather than the bent state shown in other literature works, which is consistent with the experimental work by Datchi et al and denies the observed results by Park et al. The proposed work is of great significance in determining the structure of the high-pressure phases of carbon dioxide and further exploring the new phase of molecular crystals.     

Thermodynamics and kinetics of CO2, CO, and H+ binding to the metal centre of CO2 reduction catalysts

In our developing world, carbon dioxide has become one of the most abundant greenhouse gases in the atmosphere. It is a stable, inert, small molecule that continues to present significant challenges toward its chemical activation as a useful carbon end product. This tutorial review describes one approach to the reduction of carbon dioxide to carbon fuels, using cobalt and nickel molecular catalysts, with particular focus on studying the thermodynamics and kinetics of CO(2) binding to metal catalytic sites.     

Studies on the Adsorption and Dissociation of Methane and Carbon Dioxide on Nickel

The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalysts were extensively investigated by TPSR, TPD, XPS and pulse reaction methods. These studies showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic Cα, carbonaceous Cβ and carbidic clusters Cγ surface carbon species formed by the decomposition of methane demonstrated different surface mobility, thermal stability and reactivity. Carbidic Cα is a very active and important intermediate in carbon dioxide reforming with methane, and the carbidic clusters Cγ species might be the precursor of surface carbon deposition. The partially dehydrogenated Cβ species can react with H2 or CO2 to form CH4 or CO. On the other hand, it was proven that CO2 can be weakly adsorbed on supported nickel catalysts, and only one kind of CO2 adsorption state is formed. The interaction mechanism between the species dissociated from CH4 and CO2 during reforming was then hypothesized.     

Comparison of eluents in supercritical fluid chromatography as based on density and free volume

A comparative study of chromatographic properties of different supercritical eluents has been performed by considering the retention at equal density or at equal free volume for different mobile phases. At equal density, the temperature dependence of the capacity ratios of aromatic hydrocarbons is the same for different alkane mobile phases, whereas significant deviations are observed when carbon dioxide is employed as the mobile phase. At equal free volume, a comparison of the capacity ratios measured in carbon dioxide and in alkane eluents showed a pronounced similarity for the different mobile phases when the free volume was low, i.e., at high densities. With increasing free volume, the chemical differences of the alkanes on the one hand and carbon dioxide on the other become more apparent in their elution behavior. Furthermore, it is demonstrated that the free volume can also be used as a reference basis for the data of solvatochromic shift experiments.     

Preparation of perlite-based carbon dioxide absorbent

A new highly efficient carbon dioxide absorbent consisting of sodium hydroxide, expanded perlite and acid-base indicator was prepared. The absorption efficiency, absorption capacity, flow resistance and color indication for the absorbent were tested and compared with some commercial products. The absorbent can reduce the carbon dioxide content in gases to 3.3 ppb (v/v) and absorbs not less than 35% of its weight of carbon dioxide. Besides its large capacity and sharp color indication, the absorbent has an outstanding advantage of small flow resistance in comparison with other commercial carbon dioxide absorbents. Applications in gas analysis and purification were also investigated.     

Determination of Carbon Dioxide in Finely Dispersed Diopside Using IR Spectroscopy

It has been shown that carbon dioxide can be determined in finely dispersed diopside using IR spectroscopy. For the concentrations of absorbed CO₂ from 1 to 20 wt %, the ratio of the logarithms of corresponding absorption bands depends linearly on its concentration. This linear relationship can be used for the determination of carbon dioxide.     

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work,the use of sepiolite for the removal of carbon dioxide from a carbon diox- ide/methane mixture by a pressure swing adsorption(PSA)process has been researched.Adsorption equilibrium and kinetics have been measured in a fixed-bed,and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained.A model based on the LDF approxima- tion has been employed to simulate the fixed-bed kinetics,using the Langmuir equation to describe the adsorption equilibrium isotherm.The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied.The experimental results were compared with the ones predicted by the model adapted to a PSA system.Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle.These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.     

Kinetics of chemical absorption of carbon dioxide into aqueous calcium acetate solution

Increasing energy demand in the world leads to more electricity generation mainly at fossil fuel power plants. Greenhouse gases are thus produced and mostly emitted to the atmosphere directly, resulting in global warming and climate change. Carbon dioxide is believed to be a main pollutant among greenhouse gases responsible from global warming. Conventional systems using mostly amine solutions to capture carbon dioxide at the source have some disadvantages, and alternatives are constantly being searched. In this work, a benign system of aqueous calcium acetate solution was investigated for this purpose. Calcium acetate is easy to produce, relatively cheap, environmentally friendly, nonhazardous, and noncorrosive. These properties make it a great alternative for use in capturing carbon dioxide. This absorption process is accompanied by chemical reaction. Therefore, the reaction kinetics needs to be investigated before its use in absorbers. A stirred cell reactor was used in the experiments using aqueous calcium acetate solution of different concentrations (2-20% w/w) and different carbon dioxide concentrations in gas mixtures (4.5-100% v/v dry carbon dioxide) at temperatures ranging from 286 to 352 K. The Gibbs free energy change for the overall reaction between carbon dioxide and aqueous calcium acetate solution was found to be –2.75 kJ/mol that shows the reaction is exergonic and occurs spontaneously. It was also found out that the reaction is pseudo–first order with respect to carbon dioxide which was also proven by calculating the Hatta number. Activation energy and Arrhenius (frequency) constant were also determined experimentally.     

非胺类CO2吸收剂的研究进展

针对CO₂所带来的全球气候变化问题,本文综述了可用于捕集CO₂的非胺类吸收剂类型,认为氨基酸盐、氨基酸-碳酸钾体系、离子液体、生物型吸收剂、钙基吸收剂分别具有较高的CO₂循环吸收负荷、低毒性、热稳定性好、较优的生物相容性、钙源易获取的优势,可以弥补胺类吸收剂在吸收-解吸CO₂时腐蚀性强、再生能耗高、对环境产生二次污染等方面的不足。氨基酸盐、氨基酸-碳酸钾体系可应用于具有一定规模的CO₂捕集工业中;离子液体可应用于精准、绿色环保去除CO₂工业中;生物型吸收剂可用于规模小、CO₂浓度低的工业中;钙基吸收剂可运用于CO₂浓度高的工业中。上述吸收剂皆具有一定的工业前景。     

Carbon dioxide hydrogenation: Efficient catalysis by an NHC-amidate Pd(II) complex

The utilization of carbon dioxide as a carbon source has long been a challenge in modern organic chemistry due to its low reactivity, yet high abundance. Herein we demonstrate the highly efficient hydrogenation of carbon dioxide into formic acid in the presence of an NHC-amidate Pd(II) complex. Excellent turnover number was observed when the catalyst was used under heterolytic conditions. This catalytic system provides a new and efficient carbon dioxide hydrogenation method.     

Carbon dioxide supercritical fluid chromatography-Fourier transform infrared spectrometry

Summary The coupling of carbon dioxide supercritical fluid chromatography with Fourier transform infrared spectrometry (SFC-FTIR) is a powerful tool for the separation and on-line identification of non-volatile compounds. The IR transparency of carbon dioxide in the Fermi resonance bands region versus its density has been studied. Functional groups with stretching vibrations outside the transparent window of carbon dioxide are examined. SFC-FTIR separations allow Gram-Schmidt reconstruction chromatograms or IR window chemigrams with high quality spectra to be obtained. This SFC-FTIR lightpipe (flow cell, beam condensing optics, narrow band detector) has allowed detection limits of 250ng for benzonitrile and 70ng for methyl benzoate to be reached. The feasibility of very rapid SFC-FTIR separations is shown along with the subsequent peak spectra.