CO2加氢制低碳醇CuFe基催化剂中的Mn助剂效应

采用共沉淀法制备了一系列Mn掺杂的CuFeZnK催化剂, 研究了Mn助剂对催化剂的结构及催化CO₂加氢制低碳醇合成性能的影响. 结果表明, 引入适量的Mn(质量分数2.1%)能有效提高低碳醇的选择性和时空收 率(STY), 在320 ℃和5 MPa的条件下, CO₂的转化率为29.4%, 低碳醇选择性(CO-free)达到23.2%, 时空收率达到41.1 mg·{\mathrm{g}}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-\mathrm{1}}·h^?1, 且低碳醇在总醇中的比例达到96.9%. 利用X射线衍射(XRD)、 N₂吸附-脱附实验、 X射线光电子能谱(XPS)、 透射电子显微镜(TEM)和氢气程序升温还原(H₂-TPR)等手段对制得催化剂进行表征, 结果表明, 适量Mn可以起到结构助剂的作用, 减小Cu颗粒尺寸的同时促进Fe₅C₂相的形成, 从而构建丰富的Cu-Fe₅C₂活性界面, 用于低碳醇合成. 而过量的Mn反而会堵塞催化剂的孔道, 覆盖活性位点, 降低了催化性能.     

Effect of Mn Promoter on Structure and Performance of K-Co-Mo Catalyst for Synthesis of Higher Alcohols from CO Hydrogenation

A series of Mn-doped K-Co-Mo catalysts were prepared by a sol-gel method. The catalyst structure was well characterized by X-ray diffraction, N₂ physisorption, NH₃ temperatureprogrammed adsorption, in situ diffuse reflectance infrared Fourier transform spectroscopy, and X-ray absorption fine structure spectroscopy. The catalytic performance for higher alcohol synthesis from syngas was measured. It was found that the Mn-doped catalysts exhibited a much higher activity as compared to the unpromoted catalyst, and in particular the C₂₊ alcohol selectivity increased significantly. The distribution of alcohol products deviated from the Anderson-Schulz-Flory law. The portion of methanol in total alcohol was suppressed remarkably and the ethanol became the predominant product. Characterization results indicated that the incorporation of Mn enhanced the interaction of Co and Mo and thus led to the formation of Co-Mo-O species, which was regarded as the active site for the alcohol synthesis. Secondly, the presence of Mn reduced the amount of strong acid sites significantly and meanwhile promoted the formation of weak acid sites, which had a positive effect on the synthesis of alcohol. Furthermore, it was found that the incorporation of Mn can enhance the adsorption of linear- and bridge-type CO significantly, which contributed to the formation of alcohol and growth of carbon chain and thus increased the selectivity to C₂₊OH.     

Multi-Walled Carbon Nanotubes as a Novel Promoter of Catalysts for CO/CO2 Hydrogenation to Alcohols

Multi-walled carbon-nanotubes (MWCNTs) are drawing increasing attention in recent years. This material possesses a series of unique features, such as its nanometer-sized channel, highly conductive graphitized tube-wall, sp ²-C-constructed surface, and excellent performance for adsorption and spillover of hydrogen, which make the MWCNTs full of promise to be a novel catalyst support or promoter. This article will review the recent progress in applied research of MWCNTs as a novel promoter in heterogeneous catalysis for active components, including metals and their oxides, with the emphasis on the study and development of MWCNT-promoted catalysts related to CO/CO₂ hydrogenation to alcohols and dimethyl ether based on the recent works carried out in our laboratory.     

催化剂表面Cu0含量对二氧化碳加氢合成C2+醇性能的影响

通过在空气气氛下焙烧Cu@Fe-MIL-88B MOF材料制备了CuFe组分均匀分散的催化剂前驱物, 该前驱物经过不同温度下的预还原制得表面具有不同Cu和Fe价态分布的系列催化剂. 将所制备的催化剂用于固定床反应器上CO₂加氢合成C₂₊醇的性能研究, 并结合催化剂的X射线衍射(XRD)、 X射线光电子能谱(XPS)、 氢气程序升温还原(H₂-TPR)、 氮气吸附-脱附、 扫描电子显微镜(SEM) 和高分辨率透射电子显微镜(HRTEM)等表征结果发现, 较高的还原温度增加了催化剂表面低价态的Cu和Fe的含量; 当还原温度为350 ℃时, 催化剂表面Cu⁰/(Cu⁺+Cu⁰)摩尔比为73.9%, 单质Fe摩尔分数为0.40%, 催化效果最好, CO₂转化率达到6.82%, 总醇选择性为39.4%, 其中C₂₊醇的摩尔比达到95.1%.     

Ni/K2CO3/MoS2低碳醇催化剂的表面结构和电子效应

制备了不同含量Ni改性的K2CO3/MoS2(ADM)低碳醇催化剂, 通过XRD、BET、XPS等表征技术考察了模型催化剂的表面结构和电子特征, 结果表明在ADM催化剂中Ni助剂主要以Ni-Mo-S配位结构和独立的NiSx两种形式存在. 在nNi/nMo＜1/3时, Ni-Mo-S配位结构为主要存在形式, 催化剂表面Ni含量低于体相. 随着Ni含量的提高, Ni与MoS2配位逐渐饱和, NiSx独立相逐步形成并导致Ni的表面富集, 同时Ni的富集导致ADM催化剂形成富含S和K的表面化学环境. 作为供电子助剂, Ni-Mo-S结构对应于强的电子作用, 而独立NiSx与MoS2之间的电子作用较弱. 随Ni含量的增加Ni与MoS2之间的电子作用呈现由强变弱的规律, 反映了Ni与MoS2配位饱和与独立NiSx相的形成过程.     

Water‐Enhanced Synthesis of Higher Alcohols from CO2 Hydrogenation over a Pt/Co3O4 Catalyst under Milder Conditions

The effect of water on CO₂ hydrogenation to produce higher alcohols (C₂–C₄) was studied. Pt/Co₃O₄, which had not been used previously for this reaction, was applied as the heterogeneous catalyst. It was found that water and the catalyst had an excellent synergistic effect for promoting the reaction. High selectivity of C₂–C₄ alcohols could be achieved at 140 °C (especially with DMI (1,3‐dimethyl‐2‐imidazolidinone) as co‐solvent), which is a much lower temperature than reported previously. The catalyst could be reused at least five times without reducing the activity and selectivity. D₂O and ¹³CH₃OH labeling experiments indicated that water involved in the reaction and promoted the reaction kinetically, and ethanol was formed via CH₃OH as an intermediate.     

Photo-Induced Switching of CO2 Hydrogenation Pathway towards CH3OH Production over Pt@UiO-66-NH2(Co)

It is highly desired to achieve controllable product selectivity in CO₂ hydrogenation. Herein, we report light-induced switching of reaction pathways of CO₂ hydrogenation towards CH₃OH production over actomically dispersed Co decorated Pt@UiO-66-NH₂. CO, being the main product in the reverse water gas shift (RWGS) pathway under thermocatalysis condition, is switched to CH₃OH via the formate pathway with the assistance of light irradiation. Impressively, the space-time yield of CH₃OH in photo-assisted thermocatalysis (1916.3 μmol g_cat⁻¹ h⁻¹) is about 7.8 times higher than that without light at 240 °C and 1.5 MPa. Mechanism investigation indicates that upon light irradiation, excited UiO-66-NH₂ can transfer electrons to Pt nanoparticles and Co sites, which can efficiently catalyze the critical elementary steps (i.e., CO₂-to-*HCOO conversion), thus suppressing the RWGS pathway to achieve a high CH₃OH selectivity.     

Catalytic conversion of greenhouse gases (CO2 and CH4) to syngas over Ni-based catalyst: Effects of Ce-La promoters

Dry reforming of methane (DRM) is an emerging technology as it can simultaneously serve as a prospective alternative energy source and mitigate greenhouse gases (e.g. CH₄ and CO₂). However, the industrial applications of DRM remain restricted due to the poor prospect of catalyst deactivation. In this study, the effects of adding CeO₂ and La₂O₃ as promoters on the catalytic performance of Ni/Al₂O₃ catalyst were assessed. Catalysts such as Ni/Al₂O₃, Ni/Al₂O₃-La₂O₃, and Ni/Al₂O₃-CeO₂ were synthesized at nano level using the sol-gel method. Citric acid was added to improve the reactivity of catalysts before the application of DRM. Various characterisation techniques were used to characterise synthesized catalysts, including Brunauer-Emmett-Teller (BET) analysis, temperature-programmed reduction (TPR), field emission scanning microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results revealed that the BET surface area of the synthesized catalyst slightly decreased when CeO₂ and La₂O₃ were added due to the deposition on the porous structure of the support. Meanwhile, the XRD results demonstrated the increase in reducibility and dispersion of Ni using CeO₂ promoter and the inhibited development of the non-active phase of Ni/Al₂O₃ using La₂O₃ promoter (i.e. NiAl₂O₄), resulting in the carbon formation and reduced efficiency of the catalyst. The catalytic performance in DRM at 800 °C showed that Ni/Al₂O₃-CeO₂ catalyst exhibited higher catalytic performance in terms of CH₄ and CO₂ conversion with 89.6% and 91.2% respectively. While Ni/Al₂O₃-La₂O₃ was found to play a substantial role in the stability of the chemical reaction during the 8 h reaction time-on-stream.     

稀土对二氧化碳加氢合成低碳烯烃催化剂活性的影响

以Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ作为铁－海泡石催化剂的催化剂，用于地中氢反应，合成低碳烯烃，得到了良好的结果。稀土元素的加入影响产物的分布与二氧化碳的转化率，其中，以含２５％钕的化剂及选择性最佳。     

CuAl2O4尖晶石结构对浆态床一氧化碳加氢性能的影响

采用固相法、 共沉淀法、 柠檬酸法和溶胶-凝胶法制备了CuAl₂O₄尖晶石, 在浆态床反应器上对其进行一氧化碳加氢反应活性评价, 并对CuAl₂O₄尖晶石的结构进行了表征. 研究发现, 不同方法制备的CuAl₂O₄尖晶石在织构参数、 表面富集程度和分解还原性能上存在明显差异, 进而影响其催化性能. 固相法所制尖晶石的孔径和孔容大, CuAl₂O₄表面富集程度最高, 致使尖晶石分解不完全, 但是其分解释放的CuO全部被还原, 且Cu⁺/Cu⁰占比相当高, 有利于提高产物中C₂₊OH选择性(达到31.1%). 而表面富集程度相对低的其它3种尖晶石分解完全, 但部分CuO未被还原, 且还原产物中Cu⁰占比提高, Cu⁰和γ-Al₂O₃发生协同作用促进二甲醚的生成, 其选择性最高可达72.9%.     

New Advances in Catalytic Systems for Conversion of CH4 and CO2

One of the main goals for developing the C1 chemical industry is the direct conversion of methane and carbon dioxide to useful products. To realize this goal, researches on new catalytic systems are being globally focused. The exploration has been evolved from traditional heterogeneous catalysis into homogeneous catalysis. Coordinate complexes, biochemical and bionics, and photo- and electrochemical catalysis have been extensively studied in recent years. Tests in laboratories have verified for the direct conversion of CH4 to CH3OH that single-pass converstion of CH4 can reach over 70% in both Hg(Ⅱ) salt and Pt(Ⅱ) complex systems. The main problem of these systems is the obstacles involving reaction kinetics, so they must be solved before moving to pilot tests. Other catalytic systems discussed in the present article include explorations in the early stage. Among them, features of photo and enzymatic catalyst systems, such as mild reaction conditions, better selectivity and environmentally friendliness have been explored, and these researches are significant both in theory and in practical application.     

CO2和He在阳泉煤CH4饱和基质煤柱中的渗流特性

利用自行设计的自约束渗透装置,采用热导检测器在线跟踪穿透实验过程中CO2或He的渗透信号,在40℃条件下,对比研究了CO2和He在阳泉煤CH4饱和基质煤柱(φ6×13mm)中的渗透行为,讨论了煤对气体的吸附或吸取作用及孔隙气压对渗透率的影响.研究表明,有别于煤对He的作用,在CO2和CH4交替渗透时,不同的CH4吹扫时...     

A computational study of CO2, N2, and CH4 adsorption in zeolites

The adsorption properties of CO₂, N₂ and CH₄ in all-silica zeolites were studied using molecular simulations. Adsorption isotherms for single components in MFI were both measured and computed showing good agreement. In addition simulations in other all silica structures were performed for a wide range of pressures and temperatures and for single components as well as binary and ternary mixtures with varying bulk compositions. The adsorption selectivity was analyzed for mixtures with bulk composition of 50:50 CO₂/CH₄, 50:50 CO₂/N₂, 10:90 CO₂/N₂ and 5:90:5 CO₂/N₂/CH₄ in MFI, MOR, ISV, ITE, CHA and DDR showing high selectivity of adsorption of CO₂ over N₂ and CH₄ that varies with the type of crystal and with the mixture bulk composition.     

CO加氢制C2含氧化合物Rh基催化剂中常见助剂的作用

由煤、天然气或生物质出发,经合成气制乙醇等C2含氧化合物具有重要意义,负载型Rh基催化剂是实现该过程最有效的催化剂。助剂的选择尤其重要,其中Fe、Mn、Li的助催化作用最为显著,人们对此进行了长期而有效的研究,有关观点也很难统一,但相关总结性的报道不多。因此,本文系统综述了这三种常见助剂催化作用的研究进展。结果表明,这些助剂的作用与其所处的催化体系、制备方法等密切相关,后者直接影响了助剂-金属-载体间相互作用,使得催化剂各种组分表现出不同存在状态,进而影响它们在CO加氢各基元步骤中的催化作用。本文可为人们全面认识这些常用助剂的作用提供有益的参考。     

Novel Porous Aromatic Framework with Excellent Separation Capability of CO2 in N2 or CH4

A novel porous aromatic framework, PAF-52, was obtained via the polymerization of tetrahedral mono- mer tetrakis（4-cyanodiphenyl） methane（TCDPM） with the aid of a facile ionothermal method. PAF-52 has a surface area of 1159 m2/g（BET）, and shows a considerable high separation ability of CO2 in N2 or CH4 respectively at room temperature, using gas-chromatography experiments as evidence,     

Photothermal Conversion of CO2 into CH4 with H2 over Group VIII Nanocatalysts: An Alternative Approach for Solar Fuel Production

The photothermal conversion of CO₂ provides a straightforward and effective method for the highly efficient production of solar fuels with high solar‐light utilization efficiency. This is due to several crucial features of the Group VIII nanocatalysts, including effective energy utilization over the whole range of the solar spectrum, excellent photothermal performance, and unique activation abilities. Photothermal CO₂ reaction rates (mol h^?1 g^?1) that are several orders of magnitude larger than those obtained with photocatalytic methods (μmol h^?1 g^?1) were thus achieved. It is proposed that the overall water‐based CO₂ conversion process can be achieved by combining light‐driven H₂ production from water and photothermal CO₂ conversion with H₂. More generally, this work suggests that traditional catalysts that are characterized by intense photoabsorption will find new applications in photo‐induced green‐chemistry processes.     

Effects of supercritical CO2 exposure on diffusion and adsorption kinetics of CH4, CO2 and water vapor in various rank coals

The physico-chemical effects caused by supercritical CO₂ (ScCO₂) exposure is one of the leading problems for CO₂ storage in deep coal seams as it will significantly alter the flow behaviors of gases. The main objective of this study was to investigate the effects of ScCO₂ injection on diffusion and adsorption kinetics of CH₄, CO₂ and water vapor in various rank coals. The powdered coal samples were immersed in ScCO₂ for 30 days using a high-pressure sealed reactor. Then, the diffusion and adsorption kinetics of CH₄, CO₂ and water vapor in the coals both before and after exposure were examined. Results indicate that the diffusivities of CH₄ and CO₂ are significantly increased due to the combined matrix swelling and solvent effect caused by ScCO₂ exposure, which may induce secondary faults and remove some volatile matters that block the pore throats. On the other hand, the diffusivities of water vapor are reduced due to the elimination of surface functional groups with ScCO₂ exposure. It is concluded that density of the surface function groups is the controlling factor for water vapor diffusion rather than the pore properties. The unipore model and pseudo-first-order equation can simulate the diffusion and adsorption kinetics of CH₄ and CO₂ very well, but the unipore model is not capable of well describing water vapor diffusion. The effective diffusivity (D_e), diffusion coefficient (D) and adsorption rates (k₁) of CH₄ and CO₂ are significantly increased after ScCO₂ exposure, while the values of water vapor are decreased notably. Thus, the injection of ScCO₂ will efficiently improve the transport properties of CH₄ and CO₂ but hinder the movement of water molecules in coal seams.     

金属-载体相互作用对CH4/CO2重整反应中Rh基催化剂抗积炭性能的影响

考察了Rh/Al2O3,Rh/SiO2和Rh/CeO2催化剂上金属-载体间相互作用对CH4/CO2重整反应抗积炭性能的影响,并与反应前后催化剂的程序升温还原和程序升温氧化(TPO)测试结果相关联.实验发现,Rh与Al2O3和SiO2载体间的相互作用越强,催化剂还原后Rh的分散度越高,晶粒越小,高分散的Rh表面生成的碳物种CHx越多,其作为活泼的反应中间体越易与CO2反应生成CO和H2.而游离态的Rh还原后晶粒较大,生成的碳物种与CO2反应能力较低,从而导致催化剂失活.TPO和CO2脉冲实验结果表明,反应过程中Rh/CeO2催化剂上反应生成的CHx物种比Rh/Al2O3和Rh/SiO2上的CHx物种更活泼.同时由于Rh-CeO2间独特的相互作用,部分CeO2还原后生成CeO2-x和氧空位,促进CO2分子的活化解离,导致生成的表面氧容易与CHx反应,从而抑制催化剂积炭.     

Reactions in a Mixture of CH4 and CO2 under the Aciton of Microwave Discharge at Atmospheric Pressure

Reactions between CH4 and CO2 under the action of continuous microwave discharge at atmospheric pressure were studied in a special homemade reactor,The main products were CO and H2,while acetylene and ethylene were also found in the products.Experimental results show that conversions of CH4 and CO2 could be higher than 90% without the presence of any catalyst,Effects of CO2/CH4 molar ratio and total flow rate of the feed gas on the reaction were also investigated.     

The Effects of CO2 Additional on Flame Characteristics in the CH4/N2/O2 Counterflow Diffusion Flame

The effects (chemical, thermal, transport, and radiative) of CO₂ added to the fuel side and oxidizer side on the flame temperature and the position of the flame front in a one-dimensional laminar counterflow diffusion flame of methane/N₂/O₂ were studied. Overall CO₂ resulted in a decrease in flame temperature whether on the fuel side or on the oxidizer side, with the negative effect being more obvious on the latter side. The prominent effects of CO₂ on the flame temperature were derived from its thermal properties on the fuel side and its radiative properties on the oxidizer side. The results also highlighted the differences in the four effects of CO₂ on the position of the flame front on different sides. In addition, an analysis of OH and H radicals and the heat release rate of the main reactions illustrated how CO₂ affects the flame temperature.