金属催化剂光热催化CO2还原的研究进展

CO2的过量排放导致温室效应对环境的影响越来越严重,通过电催化、光催化、热催化、光热催化或光电催化将CO2还原成高附加值的化学品是解决CO2排放的有效途径.其中, CO2的光热催化转化是当前的主要研究领域之一.我们对光热催化进行了总结分类:热助光、光助热、光驱热和光热协同催化,并详细介绍相应的催化机理,总结了金属催化剂用于光热催化CO2还原的最新研究进展,最后提出了光热催化面临的挑战与展望.     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

负载型CuO/TiO2催化剂催化CO2加氢制甲醇

采用浸渍法制备了CuO/TiO_2负载型催化剂,并将其用于CO2加氢制甲醇反应。重点考察了铜的负载量对催化剂性能的影响,并对其物化性能和催化性能之间的关系进行了讨论。结果发现,随着铜负载量的增加,催化剂中金属铜的比表面先增加后减小,当铜的负载量为10%(质量百分数)时达到最大值。催化剂的表面碱性位数量随铜含量的增加持续减小,中等碱位和强碱位的强度下降。当铜的负载量不高于10%时,CO2的转化率与铜的比表面积呈线性关系。甲醇选择性与催化剂的表面碱位性质有关,过强的碱性位会降低甲醇选择性。     

不同载体负载的Cr基催化剂催化CO2氧化异丁烷脱氢制异丁烯

制备了介孔分子筛MSU-1,γ-A12O3,AC(活性炭)和MgO负载的CrOx催化剂,并考察了其催化CO2氧化异丁烷脱氢制异丁烯反应性能.结果表明,各催化剂活性的顺序为:CrOx/MSU-1 ＞CrOx/A12O3＞ CrOx/AC＞ CrOJMgO.其中在CrOx/MSU-1催化剂上,异丁烷的转化率和异丁烯的收率分...     

负载型CuO/TiO2催化剂催化CO2加氢制甲醇

采用浸渍法制备了CuO/TiO₂负载型催化剂,并将其用于CO₂加氢制甲醇反应。重点考察了铜的负载量对催化剂性能的影响,并对其物化性能和催化性能之间的关系进行了讨论。结果发现,随着铜负载量的增加,催化剂中金属铜的比表面先增加后减小,当铜的负载量为10%（质量百分数）时达到最大值。催化剂的表面碱性位数量随铜含量的增加持续减小,中等碱位和强碱位的强度下降。当铜的负载量不高于10%时,CO₂的转化率与铜的比表面积呈线性关系。甲醇选择性与催化剂的表面碱位性质有关,过强的碱性位会降低甲醇选择性。     

In基二氧化碳氧化丙烷脱氢催化剂的研究

二氧化碳氧化丙烷脱氢增产丙烯是提高丙烷脱氢单程转化率与二氧化碳资源化利用的重要途经,探究高效的非贵金属环保型催化剂对工业界和科学界均有重要意义。采用不同合成方法制备了系列In基催化剂,通过X射线衍射、拉曼、H2-程序升温还原、扫描电镜观测了In活性位结构。关联活性数据得出,具有InO6结构的InOx团簇或In2O3颗粒在CO2氧化丙烷脱氢气氛中能够发生氧化还原循环,从而驱动CO2及丙烷分子的活化,而水热法合成样品中不含该InO6结构,因此不具备CO2活化能力。此外,十元环MFI型Silicalite-1沸石相比十二元环的Si-Beta沸石载体能够促进CO2的吸附,也提高了CO2对丙烷分子活化的促进作用。     

Fe—Zn—M／HZSM—5复合催化剂上CO2加氢性能的研究

研究了380℃、5.0MPa条件下,在Fe-Zn-M/HZSM-5(M=Cr、Al）复合催化剂上进行的CO2催化加氢的反应,考察了Fe-Zn-M中Fe含量、分子筛的硅铝比及Fe-Zn-M/HZSM-5的比率对CO2转化率和产物选择性的影响。结果表明,随着Fe含量的增加,复合催化剂的活性增强、目的产物选择性降低;Fe-Zn-M与HZSM－5间有适宜的配比;分子筛的硅铝比影响到复合催化剂的活性和选择性,随着分子筛硅铝比的降低,复合催化剂的活性增强,目的产物选择性提高。     

VOCs催化燃烧催化剂抗SO2中毒研究进展

在VOCs催化氧化过程中, 二氧化硫易与反应物在催化剂活性位点上产生竞争吸附行为, 且能够与活性物种或载体反应生成硫酸盐使催化剂中毒, 严重影响了催化氧化反应的效率. 我们总结了催化剂的SO₂中毒行为, 概括了目前在贵金属、非贵金属催化剂的设计中应用较为广泛的抗SO₂中毒措施, 如助剂掺杂、双金属体系构建、载体改性、核壳结构设计等, 剖析了催化剂酸性位的增强、结构的稳固、壳层保护等抵御SO₂吸附与反应的原理, 并对VOCs领域内抗SO₂中毒催化剂的设计进行了总结与展望.     

光催化CO2转化为碳氢燃料体系的综述

传统化石能源燃烧产生CO₂引起的地球变暖和能源短缺已经成为一个严重的全球性问题. 利用太阳光和光催化材料将CO₂还原为碳氢燃料, 不仅可以减少空气中CO₂浓度, 降低温室效应的影响, 还可以提供碳氢燃料, 缓解能源短缺问题, 因此日益受到各国科学家的高度关注. 本文综述了光催化还原CO₂为碳氢燃料的研究进展, 介绍了光催化还原CO₂的反应机理, 并对现阶段报道的光催化还原CO₂材料体系进行了整理和分类, 包括TiO₂光催化材料, ABO₃型钙钛矿光催化材料, 尖晶石型光催化材料, 掺杂型光催化材料, 复合光催化材料, V、W、Ge、Ga基光催化材料及石墨烯基光催化材料. 评述了各种材料体系的特点及光催化性能的一些影响因素. 最后对光催化还原CO₂的研究前景进行了展望.     

Intermolecular forces for D2, N2, O2, F2 and CO2

The intermolecular potentials for D₂, N₂, O₂, F₂ and CO₂ are determined on the basis of the second virial coeffincients, the polarizabilities parallel and perpendicular to the molecular axes, and the electric quadrupole moment. The repulsive parts of the potentials are taken from the corresponding Kihara core-potentials. Effects of the octopolar induction are taken into consideration in a unique way. The potential depends on relative orientations of the two molecules as well as the distance r between the molecular centers. This dependence is shown in graphs. A measure of the anisotropy of the potential depth is 0.72 for CO₂ 0.36 for D₂, and smaller than 0.27 for N₂ O₂ and F₂. The remarkable anisotropy for CO₂ and D₂ is due to strong electrostatic quadrupole interactions.     

卟啉网状结构材料负载单原子的光催化CO2还原

基于刚性、多孔性和多功能性,以及模块化优化、合理的设计和集成、可调谐和光化学性能等优点,卟啉网状结构材料已被证明是金属单原子锚定的优良载体,并在CO₂光催化还原领域拓展了一种新的载体.我们主要总结了近5年来以反应卟啉网状结构材料为载体的单原子催化剂光催化CO₂还原反应的最新研究进展,提出并探讨了该多相催化剂光催化CO₂还原的应用前景以及面临的挑战.     

CO/H2 and CO2/H2 reactions with amorphous carbon-metal catalysts

By metal impregnation of selected naturally occurring organic materials followed by controlled carbonization, metal semicoke catalysts can be readily prepared. These catalysts have been tested in the synthesis of hydrocarbons and alcohols from CO/H₂ and CO₂/H₂ mixtures. Fe and Co preparations have been used. Relatively high temperatures are required when using these catalysts, which are quite active for synthesis using CO₂ and H₂. The pressure (5150 kPa) is very favorable both for the synthesis of liquid hydrocarbons (C₅–C₃₀) and alcohols (C₁–C₅).

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. CO/H₂ CO₂/H₂. Fe Co. , CO₂ H₂. 5150 ) (C₅–C₃₀) (C₁–C₅).

     

Effect of CO2 on O2 photo-adsorption on anatase

The presence of CO₂ on TiO₂ affects the process of oxygen photo-adsorption depending on the hydroxylation state of the surface. In dehydroxylated samples CO₂ blocks the formation of O ₃ ^– and O ₂ ^– . On H₂O₂/TiO₂ samples pretreated in the range of 150–200°C it leads to CO₂–O ₂ ^– species.

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, Cu(II). . .

     

Studies on catalysts ofanti-carbon deposition for CH4 reforming with CO2

The nature of high temperature carbon states at Pt(110) has been studied by X-Ray Photoelectron Spectroscopy. The formation of diamond-like carbon (DLC) is reported for the first time. The kinetics and temperature-programmed reactions of DLC were numerically simulated.     

Hydrogenation of CO2

The hydrogenation of CO₂ has been studied on three different series of catalysts: Fe/MgO, Ni/Ti, Cr/Zn doped with potassium. Reaction was carried out in a conventional flow microreactor system at 15 bar at 250–350°C. Three independent competing reactions: Reverse gas-water shift (RGWS), Fischer-Tropsch (FT) and methanol synthesis were observed.

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CO₂ : Fe/MgO, Ni/Ti, Cr/Zn . 15 250–350°C. : RGWS, F.T. .

     

Reactions of CO2 with H, H2 and deuterated analogues

Combining a temperature variable 22-pole ion trap with a cold effusive beam of neutrals, rate coefficients k(T) have been measured for reactions of CO₂⁺ ions with H, H₂ and deuterated analogues. The neutral beam which is cooled in an accommodator to T_ACC, penetrates the trapped ion cloud with a well-characterized velocity distribution. The temperature of the ions, T_22PT, has been set to values between 15 and 300 K. Thermalization is accelerated by using helium buffer gas. For reference, some experiments have been performed with thermal target gas. For this purpose hydrogen is leaked directly into the box surrounding the trap. While collisions of CO₂⁺ with H₂ lead exclusively to the protonated product HCO₂⁺, collisions with H atoms form mainly HCO⁺. The electron transfer channel H⁺ + CO₂ could not be detected (<20%). Equivalent studies have been performed for deuterium. The rate coefficients for reactions with atoms are rather small. Within our relative errors of less than 15%, they do not depend on the temperature of the CO₂⁺ ions nor on the velocity of the atoms (k(T) lays between 4.5 and 4.7 × 10⁻¹⁰ cm³ s⁻¹ with H as target, and 2.2 × 10⁻¹⁰ cm³ s⁻¹ with D). For collisions with molecules, the reactivity increases significantly with falling temperature, reaching the Langevin values at 15 K. These results are reported as k = α (T/300 K)^β with α = 9.5 × 10⁻¹⁰ cm³ s⁻¹ and β = −0.15 for H₂ and α = 4.9 × 10⁻¹⁰ cm³ s⁻¹ and β = −0.30 for D₂.     

The reaction of (SO2)2 and (CO2)2 with Ba

The reactions of (CO₂)₂ and (SO₂)₂ with Ba have been investigated using a crossed beam arrangement and the laser-induced fluorescence technique. Internal energy in the BaO product was probed in order to study differences between monomeric and dimeric reactions. The reaction cross section for the dimers of CO₂ was found to be between four and eightfold larger than that of the monomers. This can be explained by the change in the reaction mechanism due to the positive electron affinity of the dimers versus the negative electron affinity of the monomers. The product BaO from the dimeric reactions is much colder rotationally than in the monomeric case. This phenomenon can be explained based on the kinematics.     

Hydrocondensation of CO2: Reaction of CO2(CO)/H2 on CuO/ZnO contact masses

The hydrocondensation of CO₂ and CO with and without added MeOH, HCHO and (CH₃)₂CHOH has been studied on CuO/ZnO contact masses in a static reactor at different pressures and reaction times.

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CO₂ CO MeOH, HCHO (CH₃)₂CHOH CuO/ZnO .

     

Valence-shell photoabsorption by CO2 and its connections with electron-CO2 scattering

Photoabsorption cross sections and photoelectron asymmetry parameters, calculated with the multiple-scattering model (MSM), are reported for the 4σ_g, 3σ_u, 1π_u and 1π_g valence levels of CO₂. The results are discussed in the context of photoabsorption and electron energy-loss measurements and other theoretical calculations. Further comparisons are made with previously reported MSM calculations of elastic electron-CO₂ scattering. The close connection between the sets of shape resonances in the electron-scattering and photoabsorption by CO₂ is emphasized with plots of continuum eigenchannel wavefunctions for shape-resonant and non-resonant eigenchannels of σ_u symmetry.     

Gas hydrate equilibria for CO2-N2 and CO2-CH4 gas mixtures—Experimental studies and thermodynamic modelling

In this paper, a set of experimental data on the phase equilibrium of gas hydrates in the presence of binary gas mixtures comprising CO₂ is presented. The procedure established allows for the determination of both the composition of the gas phase as well as the hydrate phase without the need to sample the hydrate. The experimental results obtained in these measurements have been described by means of the classical model of van der Waals and Platteeuw. The values of internal parameters of the reference state and the Kihara parameters have been re-discussed and their interdependency is pointed. Finally the new set of parameters is validated against experimental data from other sources available in the literature, or invalidated against other sources. Finally, we conclude on the difference of experimental data between laboratories. The differences are not on the classical (pressure, temperature, gas composition) data which appear equivalent between laboratories. The difference stands on the measurement composition of the hydrate phase.