费托合成铁基催化剂浆态床反应性能的研究

为了获得工艺参数对铁基催化剂费托合成产品分布的影响规律,在浆态床反应器中考察了反应温度、反应压力、氢碳比、空速对铁基催化剂费托合成反应性能的影响。结果表明,温度升高时,催化剂活性、CO_2和CH_4选择性均升高,产物向轻组分分布;压力增大时,催化剂活性和CO_2选择性升高,CH_4选择性下降,产物向重组分分布;随氢碳比的增加,催化剂活性和CH_4选择性升高,CO_2选择性下降,C_(5+)呈下降趋势;随空速增加,催化剂的活性和CO_2选择性下降,CH_4选择性上升,C_(5+)向轻质烃分布。选择合适的工艺条件,可有效改善铁基催化剂的费托合成反应性能,控制碳链长度和产物的分布,提高费托合成反应的经济性。     

New controlling method for product distribution in Fischer-Tropsch synthesis reaction

Addition of a small amount of heavy 1-olefin into a supercritical-phase or liquid-phase FT reaction medium could significantly promote the carbon-chain growth and greatly enhance the selectivity of waxy products, with increased CO conversion while suppressing methane selectivity. The phenomenon was not observed in the gas-phase reaction.     

掺氮碳基材料在费托合成反应中的应用

氮掺杂是一种对碳材料结构和性质进行修饰的重要方法。本文主要介绍了碳基材料掺氮的主要方法(即直接合成法和后处理法)及所得掺氮碳基材料的性质。重点综述了近年来掺氮碳基材料在制备费托合成钴基和铁基催化剂领域中的应用,进一步阐述了掺氮碳基材料作为新型费托合成催化剂载体所具有的主要优点:载体表面含氮基团具有锚定作用可提高金属活性组分分散度,同时,氮的掺杂不仅能够有效地提高催化剂还原度,而且富电子的氮物种可促进CO解离,从而有利于提高催化剂费托合成反应性能。在此基础上,本文也分析了掺氮碳基材料的合成和催化应用方面所存在的问题。     

浆态床反应器中费-托合成的综述

A brief review of Fischer-Tropsch synthesis specially in slurry reactors is presented, covering reaction kinetics, activity and selectivity of catalysts, product distribution, effects of process parameters, mass transfer and solubility of gas. Some important aspects of further research axe proposed for improving both theories and production.     

微反应器中费托合成的研究进展

目前费托合成常用的固定床、浆态床和流化床三种反应器存在不同程度的传质和传热问题,同时反应物/产物与催化剂难以分离,而微反应器因其可在接近等温和很小压降条件下进行反应,从而有望改善费托合成的反应性能,提高所用催化剂的活性和选择性。本文首先介绍了微反应器的结构和特性,然后从催化剂种类及其在微反应器中颗粒装填式和器壁涂覆式两种形式简述了微反应器中费托合成的实验研究,并从计算流体力学和动力学研究等方面简述了微反应器中费托合成的模拟计算。     

Fischer-Tropsch合成钴基催化剂研究进展

综述了近年来钴基催化剂在费托合成反应中的研究进展.重点评述了钴源、负载量、载体、助剂、制备方法、焙烧和还原条件等因素在负载型钴基催化剂制备过程中对催化剂活性、选择性控制等方面的影响,概述了钴基催化剂在费托合成反应中的催化机理,并对今后催化剂的研究提出了一点建议.     

Catalyst and process scale-up for Fischer-Tropsch synthesis

Liquid-phase Fischer-Tropsch technology was demonstrated in a bubble column at DOE's Alternative Fuels Development Unit. The 19-day run demonstrated the technology at a pilot scale and addressed scale-up issues such as catalyst activation, catalyst performance and hydrodynamics. The catalyst performance and reactor hydrodynamics were in line with expectations throughout the run.     

高温对浆态床中Fe-Cu-K-Si催化剂费托合成反应性能的影响

为了研究高温对费托铁基催化剂性能的影响,在浆态床反应器中考察了高温对Fe-Cu-K-Si费托合成催化剂反应活性及选择性的影响。催化剂评价结果表明,与265℃相比,320℃下搅拌釜内浆液高度降低22%,但液面高度保持平稳;CO转化率提高了20%,CO_2选择性降低了2%左右。提高反应温度后,CH_4和C_2~C_4选择性分别提高了4.7%和11.72%,C_2~C_4的烯烷比提高了1.99;C_3的烯烷比从4.27提高到7.64,C_2的烯烷比从3.00提高到3.87,但是C3的烯烷比提高幅度明显高于C_2。升高温度可提高费托合成的CO转化率、C_1~C_4低碳烃选择性及烯烷比,但也降低了C_(5+)的选择性。因此,工业生产中要根据烃类产品分布的实际需要来控制反应温度。     

F-T合成Co基催化剂研究进展

由于日趋严重的石油危机,寻找一种石油替代品显得尤其重要。F-T合成反应是将含碳资源转化成液体燃料的核心技术,关键是开发活性高、选择性高和稳定性好的催化剂。而Co基催化剂被认为是F-T合成最有前途的催化剂。综述了近年来Co基催化剂F-T合成反应的研究进展,重点介绍Co基催化剂的载体、助剂、制备方法和前驱体等方面对催化剂活性和选择性的影响,认为未来Co基催化剂的发展方向是增加催化剂活性和对重质烃的选择性,减少甲烷和 CO₂ 排放,研究趋势将是催化剂的复合化和多功能化。     

微通道下费托合成催化剂层涂覆厚度的数值研究

采用COMSOL-Multiphysics软件, 针对Fe基催化剂费托合成反应动力学特性, 建立了耦合流动、传热、传质、化学反应多物理场的二维数值计算单元模型, 研究微通道内的费托合成反应。重点研究了催化剂涂层厚度、冷却介质流速对微通道内传热传质、费托反应产物分布的影响规律。模拟结果表明:沿反应通道轴向方向, 催化剂涂层温度呈先升高后降低的趋势;随着催化剂涂层厚度的增加, 温度峰值出现的位置逐渐远离出口, CO转化率提高, CH₄的选择性增大, 而C₅₊的选择性逐渐减小;提高冷却介质流速有利于实现较好的温度控制, 显著降低CH₄的选择性, 提高C₅₊选择性;对于截面尺寸为0.6×0.6mm²、长度为200mm的微通道结构, 较佳的催化剂涂层厚度为0.1mm, 随着冷却侧冷却能力的增强, 较佳的催化剂涂层厚度变大。     

Production of hydrocarbons in Fischer-Tropsch synthesis with Fe-based catalyst: Investigations of primary kerosene yield and carbon mass balance

The Fischer-Tropsch synthesis (FTS) of syngas was carried out using Fe-based catalysts in order to produce hydrocarbons (HCs) equivalent to kerosene, which is used as an alternative aviation fuel. The FTS was conducted in a downdraft continuous-flow-type fixed-bed reactor under a temperature of 533-573 K and a pressure of 3.0 MPa. The effects of reduction gases and time of the Fe-based catalyst, reaction temperature and the chemical species included in the Fe-based catalyst on the FTS were studied by focusing on primary kerosene yield and the carbon mass balance. The carbon mass balances in the study were almost 100%. In C6 + HCs, the selectivity of CO to the C11−C14 HCs equivalent to kerosene was found to be the second highest, the highest being its selectivity to C20 + HCs equivalent to wax. The amount of primary kerosene produced was maximum under the following conditions: the prepared Fe catalyst did not contain other chemical species, the feed ratio of the reduction gases H₂:CO:N₂ was 2:1:3, the catalyst reduction time was 8 h, and the FTS reaction temperature was 553 K.     

Mass transfer limitations on fixed-bed reactor for Fischer-Tropsch synthesis

Mass transfer limitations on fixed-bed for Fischer-Tropsch synthesis were investigated by changing synthesis gas superficial velocity, catalyst pellet size, and catalyst amount. To study external mass transfer limitation, synthesis gas superficial velocity was changed from 8.47 × 10^− 4 m s^− 1 to 3.39 × 10^− 3 m s^− 1. As a result, the synthesis gas superficial velocity of 3.39 × 10^− 3 m s^− 1 was most suitable for hydrocarbon chain growth resulting to liquid hydrocarbon formation. In case of internal mass transfer limitations, the effects of catalyst pellet size and catalyst amount (W_cat/F) were discussed. The large catalyst pellet showed higher C₅₊ selectivity and a lower α value compared to the small pellet because of more severe internal mass transfer limitations of α-olefin and long-chained hydrocarbons in the large pellet, respectively. Catalyst amount (W_cat/F) was inversely proportional to the internal mass transfer limitation because increased catalyst amount gave more time for liquid hydrocarbon products to diffuse from the catalyst pellet and, therefore, the catalyst amount of 4.5 g (W_cat/F = 45 g_cat min L^− 1) was most appropriate for liquid hydrocarbon formation.     

还原工艺对费托合成铁基催化剂反应性能的影响

为获得还原参数对铁基费托合成反应性能的影响规律,利用铁基催化剂,在固定床反应器中考察还原氢碳比、温度、空速和压力对催化剂物理性能以及费托合成反应性能的影响。结果表明,在不同的还原工艺下,还原后的铁基催化剂比表面积下降,平均孔径增大;还原氢碳比和还原压力的升高抑制了催化剂的活性,CH_4和CO_2的选择性及C_2~C_4含量升高,C_(5+)含量下降,烃分布向轻质烃分布;还原温度和还原空速的增加有利于提高催化剂活性,还原温度的提高促使烃分布向轻质烃分布,还原空速的提高对产品分布影响不大。     

微反应器技术在Fischer-Tropsch合成中的应用进展

微反应器可以通过改善传质和传热而强化反应过程,为Fischer-Tropsch 合成技术的发展提供了新的机遇。 本文简要回顾了微反应器的研究及发展过程,从微反应器的本质特点着手,介绍了微反应器技术在 Fischer-Tropsch 合成中的应用进展。Fischer-Tropsch 合成微反应器结构经历了从单通道、多通道、复合通道结构 的研究过程,催化剂也开发有填充型和涂覆型两类。根据微反应器的特点,催化剂开发也取得了显著进步,与 传统催化剂相比,微通道催化剂的活性可以达到固定床的8～10 倍。反应器模型和数值模拟工作可以辅助实验 研究,提供温度、浓度、压力等分布参数,有利于反应器设计。最后介绍了目前微反应器Fischer-Tropsch 合成 技术的中试及工业应用情况。通过对上述内容的总结,对微反应器Fischer-Tropsch 合成研究和发展进行了展望。     

超临界条件下甲醇合成的气液传质系数测定

以液体石蜡为惰性液相载体,正己烷为超临界介质,合成气制甲醇为研究体系,测定了超临界条件下三相浆态床中甲醇合成的气液传质系数。在反应温度238℃、合成气分压3.7 MPa、气体空速2744 h^-1条件下,通过不断增加催化剂浓度提高气液传质阻力和反应阻力的相对大小,采用外推法获得完全处于气液传质控制下的气液传质系数。计算结果表明：催化剂浓度对CO的气液传质系数的影响较大,而对CO₂的气液传质系数的影响较小;液相条件下CO、CO₂的气液传质系数分别是0.161、0.03 s^-1,而超临界三相甲醇合成中CO、CO₂的气液传质系数分别是0.199、0.042 s^-1,说明三相浆态床甲醇合成中引入超临界流体利于气液传质,验证了超临界介质中三相甲醇合成的优越性。     

Highly effective cobalt catalyst for wax production in Fischer-Tropsch synthesis

Fischer-Tropsch synthesis (FTS) was carried out in a fixed bed reactor with a highly effective cobalt catalyst for wax production. The procedure for reducing the inactive cobalt oxide to the active cobalt catalyst was examined by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results showed that 300 ml/min H₂ at 350 °C for 16 h was suitable for reducing the inactive Co oxides to active metallic Co sites. In the case of the powder and pellet type cobalt catalysts with a reactant (H₂/CO = 2:1) flow rate of 15 g_cat min L⁻¹, catalyst deactivation occurred as a result of mass transfer limitations of the hydrocarbon and water produced on the catalyst. On the other hand, the pellet type cobalt catalyst with a reactant flow rate of 45 g_cat min L⁻¹ showed activity not only for liquid hydrocarbon (C₅₊) formation but also for gas product (CH₄ and CO₂) formation. In particular, the methane yield reached almost 20% due to heat transfer limitation in the catalyst. Considering the heat and mass transfer limitations in the cobalt catalyst, a Co-foam catalyst with an inner metallic foam frame and an outer cobalt catalyst was developed. SEM-EDS Co-mapping revealed the cobalt atoms to be distributed equally over the surface of the Co-foam catalyst. The Co-foam catalyst was highly selective toward liquid hydrocarbon production and the liquid hydrocarbon productivity at 203 °C was 52.5 ml  h⁻¹, which was higher than that by the Co-pellet. In addition, the chain length probability, α, by the Co-foam catalyst was 0.923 and wax formation was especially favored.     

铁基费托合成催化剂研究进展

综述了近十年来铁基催化剂在费托合成反应中的研究进展,探讨了铁基催化剂活性组分的确定及影响铁基催化剂活性组分的因素,对比了3种催化剂制备方法（熔融法、沉淀法、负载法）和5种催化剂载体（氧化物、分子筛、碳材料、双孔材料和核壳材料）对费托合成反应性能的影响,从反应活性、选择性和反应稳定性3个方面阐述了助催化剂在费托合成反应中的作用。分析认为：碳化铁是铁基费托合成催化剂的活性组分;在铁基催化剂的制备过程中,选择适宜的制备方法、载体、助催化剂,可以达到提高费托合成反应活性、目的产物选择性和反应稳定性的效果。提出合成特定结构碳化铁、进一步研究铁基催化剂反应机理仍是未来研究的重点。     

Fischer-Tropsch diesel production over calcium-promoted Co/alumina catalyst: Effect of reaction conditions

The effects of reaction conditions on the Fischer-Tropsch activity and product distribution of an alkali-earth metal promoted cobalt based catalyst were studied. The influence of the promoter on the reducibility and cobalt particle size was studied by different techniques, including N₂ adsorption, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption and acid-base titrations. Experiments were carried out on a bench-scale fixed bed reactor and catalysts were prepared by incipient wetness impregnation. It was observed that addition of a small amount of calcium oxide as a promoter (0.6 wt.%) improved the cobalt oxide reducibility and reduced the formation of cobalt-aluminate species. A positive correlation between basicity and particle size was observed. In terms of FTS results, CO conversion and selectivity were found to be enhanced by the addition of this promoter. It was important to note that the addition of calcium shifted the distribution to mainly C₁₆-C₁₈ hydrocarbons fraction, which could be greatly considered for a diesel formulation. Furthermore, the variation of the reaction conditions seemed to influence product distribution in a lesser extent than unpromoted catalyst. Also, a displacement of hydrocarbon distribution to higher molecular weight with decreasing space velocity and temperature was observed. Moreover, the addition of calcium to the cobalt based catalyst was found to greatly maintain selectivity to for a wide range of H₂/CO molar ratios.     

EDTA辅助制备高活性费托合成催化剂

费托合成（FTS）对天然气、煤炭和生物质向清洁运输燃料和增值化学品的转化至关重要。传统上,用于FTS的负载型铁催化剂主要是以氧化铝和二氧化硅为载体。然而,金属与载体的相互作用阻碍了活性相碳化铁的形成,使得催化剂活性较低。本文通过乙二胺四乙酸（EDTA）络合浸渍制备了Fe/Al₂O₃催化剂,通过带正电荷的羟基（OH{}_{\mathrm{2}}^{+}）与[Fe(EDTA)]^-配合物阴离子之间的库仑相互作用来提高氧化铝载体上铁物种的分散度。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）、比表面积（BET）、原位红外（In-situ IR）等手段进行表征分析。结果表明,添加EDTA有助于增强Fe的抗烧结性。在煅烧络合浸渍制备样品的过程中,EDTA可以分解为具有还原性质的有机小分子,将催化剂中的铁物种还原为Fe²⁺,有利于催化剂的还原;更多活性中心增强了催化剂对CO的吸附量。原位红外实验表明,EDTA辅助制备的催化剂更容易富集活性物种,从而提高CO的转化率。调节体系中碱金属钠的含量改善了烃内产物分布。在较低的氢碳比（H₂/CO=1/1）下,EDTA络合制备的Fe-Na/Al₂O₃催化剂显示出高的CO转化率（88.5%）以及最大的C₂~C₄=和C₅~C₁₁选择性,总选择性达71.2%。