Deviations of Fischer-Tropsch products from an Anderson-Schulz-Flory distribution

Negative deviations from an Anderson-Schulz-Flory distribution have been observed for the product of the Fischer-Tropsch synthesis. The catalyst was a complex-derived iron-calcium catalyst promoted with cesium sulphate, therefore, neither carrier acidity nor shape selectivity can explain the deviations. This is the first time that chemical modifications of the catalyst are observed to result in negative ASF deviations.     

The Kinetics of the Fischer-Tropsch Synthesis

The literature on Fischer-Tropsch synthesis can be divided into two broad categories: The major portion falls into the category of empirical product distribution studies done with catalyst improvement in mind, while a smaller body of data has been slowly accumulated with the intention of understanding the fundamentals of the reaction. Of this smaller body of mechanistic and kinetic work, only part deals with the quantitative formulation of rate and product distribution phenomena. A vigorous effort has also been made in recent years to contribute to this understanding by surface studies. This approach, however, has at best offered tantalizing views of the various adsorbed species without leading to a quantitative formulation of the kinetics of observable phenomena at reaction conditions.     

The Kinetics of the Fischer-Tropsch Synthesis

The literature on Fischer-Tropsch synthesis can be divided into two broad categories: The major portion falls into the category of empirical product distribution studies done with catalyst improvement in mind, while a smaller body of data has been slowly accumulated with the intention of understanding the fundamentals of the reaction. Of this smaller body of mechanistic and kinetic work, only part deals with the quantitative formulation of rate and product distribution phenomena. A vigorous effort has also been made in recent years to contribute to this understanding by surface studies. This approach, however, has at best offered tantalizing views of the various adsorbed species without leading to a quantitative formulation of the kinetics of observable phenomena at reaction conditions.     

高温固定流化床费托合成技术及其产物加工路线

与采用低温费托合成主产油品技术相比,产品更为多元化和高值化的高温费托合成技术在目前市场环境下显示出非常明显的优势。本文综述了高温费托合成技术的发展历程及其最新进展,重点介绍了高温费托合成过程中的核心问题,主要包括高温费托合成工艺、固定流化床反应器、费托合成催化剂;介绍了高温费托合成产物分布与特性,讨论了高温费托合成产物的加工路线,并对高温费托合成煤间接液化的工业应用前景和产业化方向进行了展望。结果表明：高温费托合成技术具有产物附加值高、兼顾油品和化学品、技术发展成熟等优势,产物中轻组分含量高、碳数分布较窄、高附加值的α-烯烃含量高;精细化、高端化、差异化加工是实现高温费托合成产物高值化利用的关键。     

F—T合成产物分布的数理统计处理

F-T合成是一结构敏感的表面聚合反应,其产物分布比较复杂,许多模型只能近似地描述F-T合成反应的产物分布规律。本文系统总结了近几年用数理统计法对F-T合成产物分布的处理结果,这些方法的共同假设是F-T合成的三类主要产物——烷烃、烯烃和含氧有机物——是经由同一中间体形成的,只是链终止的方式不同。详细介绍了T-W模型和Basini模型,以及对ASF分布的深入分析。     

On interpreting ft product distribution data

It is shown that a CSTR is essential for the correct evaluation of kinetic parameters in the Fischer-Tropsch (FT) synthesis. Furthermore, a rather complicated expression is required in order to extract the correct growth probability at low carbon number in cases where a “break” is observed in the Anderson-Schulz-Flory (ASF) distribution. It is shown that if product molecules can readsorb and continue to grow on a variety of locations where competing processes occur, the linearities of the ASF plot are preserved but the slopes of the plot no longer have a simple interpretation in terms of processes governing chain growth on the surface. Finally, results obtained using an integral Plug Flow Reactor (PFR) are shown to yield “growth probabilities” which have no fundamental significance and are a function of the level of conversion and of the input H₂/CO ratio.     

Production of clean transportation fuels and lower olefins from Fischer-Tropsch Synthesis waxes under fluid catalytic cracking conditions: The potential of highly paraffinic feedstocks for FCC

The potential of Fischer-Tropsch Synthesis (FTS) waxes as a feedstock for fluid catalytic cracking (FCC) has been evaluated with a once-through microriser reactor operating under realistic conditions. The highly paraffinic feedstock has a high reactivity and can be converted under industrial conditions to a high extent (>90 wt%). The product distribution can be optimised by the process parameters and catalyst formulation. A high gasoline fraction (70 wt%) with a very low aromatics concentration can be obtained. As a result of the formation of i-paraffins, n-olefins and i-olefins the gasoline is expected to possess an acceptable octane number. The reaction scheme derived predicts that the degree of branching in the paraffinic diesel-range product is lower than that of the gasoline-range product and that a relatively good diesel is expected. Due to the absence of sulfur and nitrogen in the feed extremely clean transportation fuels are obtained. The addition of ZSM-5 to an equilibrium catalyst allows the production of significant amounts of light olefins, in particular propene (16 wt%) and butenes (15 wt%).     

低温费托合成蜡油加氢裂化精制技术的研究进展

低温费托合成技术因具有产品质量性好、反应耗能低、生产能力大且催化剂种类广泛等优点在煤化工领域备受关注,低温费托合成的蜡油产品可通过加氢裂化精制获取高品质清洁油品,具有巨大的应用价值。本文首先阐述了费托合成的产物特性,分析了加氢裂化过程的反应特点、双功能催化剂的碳正离子反应机理及蜡油主要反应历程。在此基础上,着重综述了蜡油加氢裂化双功能催化剂的研究进展,讨论了活性金属组分、载体以及助剂对加氢裂化过程的影响,分析表明活性金属的负载量、载体的酸量和孔道结构对催化性能有极大影响,合理优化和平衡加氢金属活性位和裂解酸性位是确保蜡油加氢裂化催化剂活性的关键。更为重要的是,基于分子筛载体的择形效应,实现载体多级孔结构和活性位的理性集成无疑会促进蜡油加氢产物的合理分布。     

Peaked distribution ethoxylates-Their preparation,characterization and performance evaluation

A peaked ethylene oxide distribution alcohol ethoxylate can be produced using new catalyst systems. The mechanism of ethoxylation is discussed. Such Novel™ ethoxylates are markedly different from a conventional ethoxylate in physical properties and performance characteristics. Performance and formulation studies show several advantages for the peaked distribution in typical household product formulations. Presented at the AOCS meeting in Dallas, May 1984. Deceased.     

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.     

The effects of catalyst surface heterogeneity on the fischer-tropsch synthesis

We find that the surface energetic heterogeneity of Fischer-Tropsch catalysts is either not important kinetically or may be masked by the effect of increasing molecular size, so that the classical Anderson-Schulz-Flory distribution is routinely observed in product distributions. The anomalous yields of C₁ and C₂ observed in many cases may also be due to surface heterogeneity but can in practice be readily, and more conveniently, accounted for by assigning individual rate constants to their formation. The “break” sometimes observed in ASF distributions cannot be explained by surface heterogeneity and is best explained by the presence of two distinct modes of product formation.     

基于Aspen模拟费托合成与CO_2再利用系统

建立了集成费托合成与碳还原反应系统的模型,采用Aspen软件进行仿真分析和计算,重点分析碳气化反应过程及费托合成的产物分布。在煤气化联合循环发电系统中集成该模块,CO2与焦炭发生还原反应得到CO,与来自煤气化单元的H2在费托合成反应器里合成液体燃料,未反应完的合成气用于燃气轮机联合循环发电。针对碳还原反应器和费托合成反应器两部分进行了模拟分析,研究了反应条件对产物的影响。分析结果表明回收CO2制取具有高附加值的液体燃料是CO2再利用的一条有效途径。     

Influence of the hydrocarbons distribution on the heat produced during Fischer-Tropsch synthesis

The heat produced during Fischer-Tropsch synthesis has been calculated, considering a base case in which a typical Anderson-Schulz-Flory (ASF) distribution is followed by the paraffinic hydrocarbons produced. An equation has been obtained, which allows us to calculate the enthalpy of reaction, using the probability of chain growth as the variable. The effect of a deviation from the ASF distribution has been considered, through the example of a higher methane selectivity than in the base case. The correction due to the condensation of higher hydrocarbons has also been evaluated. In order to be able to perform energy balance calculations, the physical state of water at the reactor outlet has been checked.     

Diesel production in coal-based high-temperature Fischer-Tropsch plants using fixed bed dry bottom gasification technology

Gas-to-liquids (GTL) and also coal-to-liquids (CTL) Fischer-Tropsch plants using high-temperature (entrained flow) gasification all face the same refining challenge, which is meeting the EN590 density specifications of 820 kg m⁻³ at 15 °C for the produced distillate. Fischer-Tropsch distillates can, however, be blended with high density distillates originating from sources such as crude oil, direct coal liquefaction or coal pyrolysis products, in an effort to conform to those diesel density requirements. Fixed bed dry bottom (FBDB) gasification technology can in combination with high-temperature Fischer-Tropsch (HTFT) synthesis provide a way to produce final on-specification CTL transportation fuels. Hydroprocessing FBDB gasification tar results in a distillate with high density whereas a hydrotreated HTFT distillate corresponds to a highly paraffinic product with high cetane number but low density. Both distillates can be blended to produce a market-ready final diesel which is of particular industrial importance for CTL applications in countries which have no oil but low-rank coals instead and viable options for carbon capture and storage (CCS).     

A NEW PATHWAY OF GAS-TO-LIQUID CONVERSION USING CATALYTIC DIELECTRIC-BARRIER DISCHARGE

A new pathway of gas-to-liquid conversion, directly from methane and carbon dioxide, was established recently using a catalytic dielectric-barrier discharge (DBD) with zeolite. Direct fuel synthesis becomes possible at reaction conditions close to ambient ones. The products from such direct fuel synthesis include alkanes, alkenes, oxygenates and Syngas (CO + H2). The product distribution is similar to that from Fischer-Tropsch(F-T) synthesis but it does not follow the Flory-Schulz kinetics. The presence of zealots within discharge plasmas improves the selectivity of lighter hydrocarbons.     

超细粒子Fe-Mn工业催化剂F-T合成集总机理动力学(Ⅰ)反应机理与动力学模型描述式

为获得超细粒子Fe-Mn工业催化剂在F-T合成中CO转化的动力学模型描述式,为其工业放大过程中反应器设计提供依据,将F-T合成这样一个包括数百个反应的体系集总为F-T烃生成反应和水煤气转换（WGS）反应.这样,反应物CO的转化速率可近似地用烃生成速率与CO₂生成速率之和来表示.在碳化物机理基础上建立烃生成基元反应步骤,以决定烃“结构单元”CH^*₂生成的步骤为速控步骤建立动力学模型.同时,在甲酸盐机理基础上建立CO₂生成的基元反应步骤,以甲酸盐物种的生成步骤为速控步骤建立动力学模型.将二者组合,获得同时包括F-T烃生成反应和WGS反应的F-T合成集总动力学模型.     

过滤技术在油浆分离中的应用

在催化裂化、加氢裂化等催化反应过程中,产品油浆中催化剂细粉不仅会导致下游设备的腐蚀和堵塞,也限制和降低了其直接作为产品、副产品的应用领域和经济价值。而对于低温费托合成反应而言,将费托合成蜡从气液固三相的浆态床反应器内分离出来,是整个费托合成工艺的的技术难点和关键之一。由此看出,油浆分离和净化技术的选择关系到以上催化反应的稳定运行和产品质量。本文回顾了目前国内外油浆过滤技术的研究及工业应用现状,总结了以美国MOTT公司为代表的金属烧结粉末和Pall公司为代表的金属烧结丝网两种主流滤芯的机械加工特性和过滤精度等特点,从操作条件、分离效率、反冲洗方式等方面进行比较,分析了各种油浆过滤技术的工艺特点,以及过滤工艺与参数对过滤效果和过滤技术选择的影响,可以为传统石油化工油浆过滤以及费托合成浆态床过滤分离技术在滤芯和过滤工艺选择等方面提供参考。     

费托法合成液体燃料关键技术研究进展

综述了近年来费托合成液体燃料关键技术的研究进展,从催化剂、动力学机理和反应器方面进行了阐述.     

A comprehensive mathematical model for the Fischer-Tropsch synthesis in well-mixed slurry reactors

A new product distribution quasi-steady-state model was proposed for the Fischer-Tropsch (FT) synthesis in slurry reactors, being applicable to their transient simulation. It may consider two chain propagation mechanisms or sites and the possibility of 1-olefin readsorption with secondary reactions, recovering the Anderson-Schulz-Flory (ASF) model, the two superimposed ASF model and the 1-olefin readsorption model as particular cases. The hydrocarbon compounds were lumped according to the number of carbon atoms in their molecules for the paraffin and 1-olefin families. The phases were assumed to be well mixed in the reactor and transient mass balances were performed for each component, allowing simulation of operation in constant liquid level and no liquid withdrawal conditions. A rigorous calculation of the vapor-liquid equilibrium (VLE) through cubic equations of state was used to describe the phase behavior. Rate expressions for the FT and the water gas shift reactions are taken from the literature and expressed in terms of fugacities. Simulation results showed that the inclusion of both the olefin readsorption and the two chain propagation mechanisms may explain the anomalies present in experimental hydrocarbon product distribution. Moreover, the effect of phase-equilibrium modeling on product distribution simulation was shown to be slightly important in the conditions analyzed. Compositional lumping schemes for the hydrocarbons were investigated to speed up the simulations. Results showed that lumping can speed up computations up to 250 times with negligible loss of accuracy.     

Fischer-Tropsch synthesis catalyzed by iron catalyst supported on porous polymers. II. Catalytic results

Macroporous styrene-divinylbenzene and 4-vinylpyridine-divinylbenzene copolymers were used as supports for an iron Fischer-Tropsch catalyst. The catalytic systems were studied in batch reactions of uniformly supported catalysts, continuous reactions of uniformly supported catalysts and continuous reactions of fully heterogenised catalysts. We have shown that the particular distribution of products and selectivity observed for the corresponding homogeneous catalytic systems are in general conserved in the supported ones. The supported induces a better selectivity in alkene synthesis, and for the fully heterogenised system there is, depending on the rate of gas flow, a relatively important selectivity in the oxy product.