Effect of Fe content on FeMn catalysts for light alkenes synthesis

The effect of Fe content on FeMn/MgO catalysts for light alkenes synthesis through CO hydrogenation was investigated. Catalysts were prepared by a conventional co-impregnation method, characterized using BET, X-ray powder diffraction (XRD) and Temperature-programmed reduction (H₂-TPR) techniques. High activity was obtained over the catalyst with 9 wt-% Fe content, over which CO conversion and the selectivity of C₂ ⁻-C₄ ⁻ reached 91.36% and 58.48%, respectively. With the increase of Fe content, both the conversion and the selectivity were improved within a certain range and then decreased. The results show that the surface area of the catalyst played an important role in the catalytic reaction. With the increase of Fe loading, the interaction action between Fe and Mn was enhanced and FeMn solid solution was formed. __________ Translated from _{Natural Gas Chemical Industry}, 2007, 32(6): 17–20 [译自: 天然气化工]     

Effect of redox additives over Ni/Al2O3 catalysts on syngas production via methane catalytic partial oxidation

Alumina-supported nickel catalysts modified with redox (Mo, Mn and Sn) oxides were tested in the catalytic partial oxidation (CPO) of methane and the wet catalytic partial oxidation (wet-CPO) of methane for syngas production. The influence of different reaction parameters on the performance of these systems was studied for both reactions. Certain insights on catalyst surface structure were revealed by means of X-ray photoelectron spectroscopy (XPS) and thermal programmed reduction (TPR). The joint analysis of all the results led to certain correlations between the structure of the catalysts and catalytic activity, indicating that the redox additives to some extent modify the stability of the active nickel phase by altering the nickel–alumina interface interaction.     

生物质合成气甲烷化机理及催化体系研究进展

天然气的供需矛盾促使人们寻找新的天然气资源,其中利用生物质合成天然气（Bio-SNG）的替代技术受到了全世界的关注。在整个工艺过程中,生物质合成气制取甲烷是关键技术,而甲烷化催化剂是其核心要素。简述了近年来生物质合成气甲烷化机理及其催化体系的研究进展,重点讨论了合成气中CO甲烷化、CO₂甲烷化反应机理,以及甲烷化催化剂中活性金属、助剂和载体对CO甲烷化、CO₂甲烷化以及CO与CO₂共存条件下甲烷化反应性能的影响,分析了目前仍存在的主要问题,并指出了进一步研究的发展方向。     

ZrO2-Al2O3复合载体负载Ni基催化剂COx甲烷化性能

采用浸渍和粉末压片的方法制备了两种ZrO₂-Al₂O₃复合载体并用于负载Ni基催化剂,并利用氮气等温物理吸附、X射线粉末衍射（XRD）、H₂程序升温还原（H₂-TPR）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等分析手段对催化剂物化性质进行表征,考察了ZrO₂-Al₂O₃复合载体制备方法及ZrO₂的引入对Ni基催化剂在CO、CO₂和CO-CO₂共存的3种体系下甲烷化反应活性的影响。材料表征和活性测试结果表明,在CO甲烷化体系中,与单一Al₂O₃载体相比,引入ZrO₂的复合载体能有效提高催化剂中Ni物种的分散度从而增强CO甲烷化过程中催化剂活性,且粉末压片法较浸渍法制备的复合载体能有效提高催化剂的还原度,降低还原温度,但前者会大大降低催化剂的比表面积;在CO₂甲烷化体系中,当载体形貌和制备方法相同时,载体的变化对催化剂活性的影响较小,CO₂转化率主要受到制备方法不同引起的物理性质如比表面积变化的影响;在CO-CO₂共存体系中,由于CO在竞争吸附中比CO₂更容易占据活性位点,所以呈现出优先进行CO甲烷化再进行CO₂甲烷化、CO₂的含量先增多后减少的规律。     

A new supported Fe-MnO catalyst for the production of light olefins from syngas. I. Effect of support on the catalytic performance

CO-TPD and H₂-TPD and CO/H₂-TPSR were used to study the effect of the support on the performance of Fe-MnO catalysts in CO hydrogenation for the production of light olefins. It was found that a Fe-MnO/MgO catalyst (based on a basic support) is capable of strongly adsorbing CO and H₂ favorable for the production of light olefins and CO conversion. A Fe-MnO/ Al₂O₃ catalyst (based on an acidic support) only showed strong adsorption of H₂, but weaker adsorption of CO, and so, it was a poor catalyst for light olefins from syngas.     

Ni-Cu/Al_2O_3·SiO_2催化剂上乙醇水蒸气重整制氢———燃料电池氢源技术

本文研究了Cu的含量对Ni-Cu/Al2O3.SiO2催化剂上乙醇水蒸气重整制氢性能的影响。活性测试表明：Cu含量为5%时,催化剂的性能最好,400℃时的氢气选择性为61.2%,600℃时的氢气选择性达到92.0%。TPR显示：随着Cu含量的增加,载体与NiO之间的相互作用变弱。XRD得出：含5%Cu的催化剂中Cu组分的分散度好,有助于提高催化剂的性能。     

Catalytic hydrogenation of CO over the doped perovskite oxide YBa2Cu3O7-x catalysts

Perovskite oxide structured YBa₂Cu₃O₇-x(YBCO) has been first prepared by carbonate precipitation and then modified with palladium or ruthenium by impregnation on the perovskite oxide, while cobalt was co-precipitated simultaneously in the same pH range with perovskite oxide. After characterization the catalysts were used in the temperature range 300–450°C, in the pressure range 1–9 atmospheres and for H₂/CO ratios in the range 1–4 in a differential plug flow reactor for the hydrogenation of carbon monoxide to give hydrocarbons. The perovskite oxide (YBCO) 20% (w/w) and doped 2% (w/w) cobalt oxide catalyst were prepared by the wet chemical method from their nitrate solutions and oxidized at 950°C. Perovskite oxide (Dursun, G. & Winterbottom, J. M., J. Chem. Technol Biotechnol. 63 (1995) 113–16) was also doped with palladium and ruthenium metal by impregnation followed by oxidation at 250°C. The catalysts prepared were characterized by using TemperatureProgrammed Reduction (TPR) to observe the reduction temperature and also to measure total and metal surface area. The modified perovskite oxide on alumina, ruthenium- and cobalt-doped catalysts, has been shown to give a better conversion and also selectivity towards saturated hydrocarbons compared with palladium-doped catalyst. The temperature effect of these catalysts is more consistent, giving a steady increase of conversion with increasing temperature. Although increase of pressure increases the conversion, it causes very little change in product distribution. The activation energy of palladium- and ruthenium-doped, and cobalt co-precipitated catalysts for the reaction has been measured to be 55 kJ mol⁻¹, 75 kJ mol⁻¹ and 50 kJ mol⁻¹ respectively. A general rate equation of the form r=k[H₂]^m[CO]ⁿ has been observed and found to be applicable at the pressures and temperatures used for the catalytic system studied and found to be m≌1·0 for palladium-doped, m≌1·2 for ruthenium-doped and m≌0·95 for cobalt co-precipitated catalysts as n becomes zero or negligibly less than zero. The mechanism of reaction to produce hydrocarbons from syngas has been deduced from the results. It appeared that the carbon monoxide insertion mechanism has been more evident for palladium-doped catalysts whereas the carbide mechanism plays the main role for the ruthenium-doped and cobalt co-precipitated catalysts. © 1998 Society of Chemical Industry     

Carbon monoxide hydrogenation over Fe/HZSM-5 catalysts. Effect of SiO2/Al2O3 zeolite ratio

Iron catalysts supported on ZSM-5 zeolites of a wide range of silica-to-alumina ratios (29-) have been prepared and tested in carbon monoxide hydrogenation. The crystalline phases of the catalysts were characterized by X-ray diffraction and their acidity by infrared spectroscopy of adsorbed pyridine. The catalytic tests were conducted at 533 K, an overall pressure of 21 bar and a feed ratio CO/H₂ close to 1. It was found that the selectivity to light olefins (C₂–C₄) increases in parallel with the increase of the Si/Al ratio of the zeolite. This was explained in terms of the decrease in Brønsted acidity of the catalysts. As a consequence, very high olefin selectivities can be achieved by decreasing the number of strong acid sites in the zeolite structure, but at the expense of high oxygenate formation.     

丙三醇水蒸气重整制氢M/Al2O3催化剂

以Al2O3为载体,采用浸渍法制备了Cu、Co、Ni、Pt/Al2O3四种单一组分催化剂(M/Al2O3)。研究了M/Al2O3催化剂对丙三醇水蒸气重整制氢反应的适用性及反应行为;考察了制备条件及还原条件,通过活性、稳定性及抗积炭性进行了催化剂的活性评价,并对催化剂进行了TPR、XRD表征。研究发现M/Al2O3催化剂用于丙三醇水蒸气重整制氢均表现出一定活性;其中Cu/Al2O3催化剂具有一定的抗积炭性;Pt/Al2O3催化剂表现出较好的抗积炭性、高温活性,但稳定性较差;Co/Al2O3催化剂表现出较好的稳定性;Ni/Al2O3催化剂表现出较好的低温活性。     

Catalytic decomposition of light alkanes, alkenes and acetylene over Ni/SiO2

The decomposition of different hydrocarbons (CH₄, C₂H₆, C₂H₄, C₂H₂, C₃H₈, and C₃H₆) over Ni (5 wt.%)/SiO₂ catalysts was carried out. The initial rates of decomposition of the hydrocarbons, the kinetic curves of the decomposition and the kinetic curves of the hydrogenation of deposited carbon into methane depended on the types of hydrocarbons. In addition, the catalytic life of the Ni/SiO₂ catalyst was also dependent on the types of hydrocarbons, i.e. the life was longer according to the order, alkanes>alkenesacetylene.

The carbons deposited on the catalyst were characterized by SEM and Raman spectroscopy. The appearances of the deposited carbons were different among alkanes, alkenes, and acetylene, i.e. a zigzag fiber structure from methane, and a rolled fiber structure from alkenes and acetylene. From Raman spectra of the deposited carbons, it was found that the degree of graphitization of deposited carbon was higher in the order, alkanes>alkenes>acetylene. These results suggest that the mechanism of decomposition of hydrocarbons and the growth mechanism of carbon fibers on the catalyst were different among alkanes, alkenes and acetylene.     

V2O5-MoO3/TiO2 催化剂的NOx选择性催化还原及SO2氧化活性

采用浸渍法以TiO₂为载体制备V₂O₅-MoO₃/TiO₂ 选择性催化还原催化剂,研究V₂O₅和MoO₃负载量对于催化剂选择性催化还原反应及SO₂氧化活性的影响,并考察氧含量、氨氮物质的量比和反应空速对3%V₂O₅-6%MoO₃/TiO₂催化剂选择性催化还原脱硝活性的影响。结果表明,随着催化剂中V₂O₅负载质量分数增加,V₂O₅-MoO₃/TiO₂ 催化剂的选择性催化还原活性和SO₂氧化活性均呈上升趋势。MoO₃的负载对催化剂的SO₂氧化活性有明显抑制作用。MoO₃负载质量分数超过9%,制备的催化剂既保持较高的低温选择性催化还原活性,又使选择性催化还原反应中的SO₂转化率小于1%。     

Dehydrogenation of ethylbenzene to styrene over Fe2O3/Al2O3 catalysts in the presence of carbon dioxide

An Fe₂O₃ (10 wt%)/Al₂O₃ (90 wt%) catalyst prepared by a coprecipitation method was found to be effective for dehydrogenation of ethylbenzene to produce styrene in the presence of CO₂ instead of steam used in commercial processes. The dehydrogenation of ethylbenzene over the catalyst in the presence of CO₂ was considered to proceed both via a one-step pathway and via a two-step pathway. CO₂ was found to suppress the deactivation of the catalyst during the dehydrogenation of ethylbenzene. This revised version was published online in July 2006 with corrections to the Cover Date.     

ZtO2晶相形式对Ni-B/ZrO2催化剂CO选择性甲烷化性能的影响

Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B catalysts were obtained by thermal treatment in 5%H2-N2 stream at different temperature.The effect of ZrO2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated,and the catalysts were characterized by N2 physisorption,Powder X-ray diffraction(XRD), Temperature-Programmed Desorption(CO-TPD and H2-TPD),and Differential Scanning Calorimeter(DSC).The treatment temperature affected strongly the crystalline structure of ZrO2,and the CO methanation activity and selectivity of the Ni-B/ZrO2 catalysts were significantly influenced by the crystalline phase of ZrO2.Of the three forms of ZrO2 polymorphs(amorphou-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2),the amorphous-ZrO2 supported nickle catalyst showed highest CO methanation activity,attributing in large part to the largest specific surface area and the optimum CO/H2 absorption intensity of the Ni-B/amorphous-ZrO2 catalyst.     

Fe2O3对V2O5-WO3/TiO2催化剂表面性质及其性能的影响

催化剂是选择性催化还原(SCR)脱硝技术的核心,研究Fe对钒钛系SCR催化剂脱硝活性及SO₂/SO₃转化率的影响具有重要意义。采用等体积浸渍法制备了不同Fe/V质量比的Fe₂O₃-V₂O₅-WO₃/TiO₂催化剂,并进行表征,研究Fe对钒钛系SCR催化剂脱硝活性及SO₂/SO₃转化率的影响,并讨论Fe对于钒钛系SCR催化剂表面性质的影响。结果表明,随着催化剂表面Fe₂O₃含量增加,催化剂的脱硝效率及二氧化硫氧化率均是先上升后下降,当Fe/V质量比为3.0时,催化剂的脱硝效率和二氧化硫氧化率均达到最大值91.78%、1.01%。XPS及H₂-TPR结果表明,随着Fe₂O₃含量增加,催化剂表面钒活性组分的相对含量及V⁴⁺/V⁵⁺比减小,催化剂表面吸附氧(O_α)浓度增加,催化剂的氧化能力增强。NO-TPD结果表明,随着Fe₂O₃含量增加,催化剂表面吸附NO的能力增强。     

加料方式对共沉淀法制备的Cu/MnO/Al2O3催化剂性能的影响

采用共沉淀法制备Cu/MnO/Al₂O₃催化剂,运用N₂吸附-脱附、XRD、XRF和H₂-TPR等对其进行表征,并用于乙酸甲酯加氢制乙醇反应,考察共沉淀加料方式对催化剂结构及其催化性能的影响。结果表明,共沉淀时采用的加料方式显著影响制备的Cu/MnO/Al₂O₃催化剂的织构性质、CuO晶粒大小、还原性能和化学组成,这些因素共同作用决定了催化剂在乙酸甲酯加氢反应中的催化性能。其中,反加法制得的催化剂Cu和Mn组分含量相对比值接近理论值,且具有较高的比表面积和较佳的还原性能,因而表现出最佳的催化性能,在反应温度200 ℃、压力6.5 MPa、空速0.6 h^-1和氢酯物质的量比50条件下,乙酸甲酯转化率和乙醇选择性分别达98.9%和98.1%。     

K2O影响Cu/ZnO催化剂CO2加氢反应性能的原因分析

运用活性评价、XRD、TPR、CO2-TPD、CO-TPD等手段,分析了K₂O影响Cu/ZnO催化剂CO₂加氢反应性能的原因。试验结果表明,甲醇收率大幅度降低的原因是CuO-ZnO催化剂经K₂O改性后,催化剂还原难度增加;提高了金属Cu的电子密度,促进了CO的歧化反应;催化剂还原后,对CO₂的吸附量大为减少。     

低碳烷烃烯烃在超微孔柔性Cu(Qc)2上的吸附行为

采用实验研究与分子模拟相结合的方法研究了低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附热力学、动力学和吸附分离机理。用常温合成方法制备了超微孔金属-有机骨架材料Cu(Qc)₂,测定了低碳烷烃烯烃（CH₄/C₂H₄/C₂H₆/C₃H₆/C₃H₈）在Cu(Qc)₂上的吸附相平衡和吸附动力学。使用Materials Studio中的Fortcite模块模拟低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附机理以及材料的结构形变。结果表明Cu(Qc)₂具有优良的C₂H₆ /C₂H₄吸附选择性和吸附动力学,而对C₃H₈ /C₃H₆的吸附选择性很低。273 K和0.1 MPa下,C₂H₆/C₂H₄在Cu(Qc)₂上的IAST选择性达4.6。298 K和0.05 MPa下C₂H₆/C₂H₄在Cu(Qc)₂上的扩散时间常数分别达1.42×10^-3和1.48×10^-3_{s^-1,扩散活化能分别为16.62 和16.43 kJ/mol。应用装填Cu(Qc)2的固定床可在常温条件下实现C2H6 /C2H4二元混合气的完全分离。模拟结果显示Cu(Qc)2为二维堆叠结构,材料会由于吸附不同分子而发生不同程度的结构形变。甲烷易从变大的层间扩散脱附,导致其在材料上的吸附量很低;C2H6/C2H4两者都能稳定吸附在层中的孔道中,其分离推动力主要来源于两种气体在材料上明显的吸附热差异;C3H8/C3H6会分别吸附在两种不同的环境,吸附热差异小导致Cu(Qc)2对C3H8 /C3H6的吸附选择性低。}     

The effect of La2O3 on dynamic OSC over the Pd/OSC/Al2O3-based catalysts

In this study, fresh and aged Pd/(OSC–Al₂O₃) and Pd/(Al₂O₃–OSC–La₂O₃) metallic monoliths (OSC material Ce_0.75Zr_0.25O₂) were used to find out the effect of La₂O₃ on the catalyst behaviour in dynamic oxygen storage capacity (OSC) measurements. In addition, the interaction of CO, NO and O₂ reaction compounds over the studied catalysts was investigated in order to understand the effect of La₂O₃ in the oxidation and reduction reactions in lean automotive exhaust gas conditions. A FT-IR gas analyser was used to analyse the product gas composition. The presence of La₂O₃ on fresh and aged catalysts had negative effect on both the dynamic OSC and the activity of the catalyst. The reason for this is the different washcoat compositions between the studied catalysts which could explain the differences in BET surface areas.     

富氢气体中CO优先氧化催化剂研究进展

介绍了富氢气体中CO优先氧化贵金属与非贵金属催化剂的研究进展,包括Pt催化剂、Au催化剂和Cu催化剂等,综述了载体、助剂、预处理和制备方法等对优先氧化性能的影响,重点评述改善Pt催化剂低温活性的方法.     

制备方法对V_2O_5-WO_3/TiO_2选择性催化还原催化剂性能的影响

采用共沉淀法、溶胶-凝胶法和浸渍法制备了V2O5质量分数4%和WO3质量分数6%的V2O5-WO3/TiO2选择性催化还原催化剂,对比了3种方法制备的催化剂选择性催化还原NO性能。采用X射线衍射、热重、N2吸附-脱附和程序升温还原等对制备的V2O5-WO3/Ti O2催化剂的结构和性质进行表征,结果表明,共沉淀法制备的V2O5-WO3/TiO2催化剂具有更好的选择性催化还原NO活性和更大的比表面积,影响共沉淀法选择性催化还原NO活性的主要因素是催化剂的热稳定性、表面羟基数量、比表面积、粒径分布以及V、W与Ti之间的内在作用。