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.     

Kinetics of Fischer-Tropsch selectivity

The kinetic model of Fischer-Tropsch chain growth as a non-trivial surface polymerization is developed and applied to discuss olefin/paraffin selectivity. The probability of the olefin chemidesorption-reaction, which controls primary olefin selectivity, is derived from experimental data as a function of temperature and total pressure. Secondary olefin hydrogenation and olefin double bond shift are identified in the system as interrelated reactions.     

The Fischer-Tropsch Synthesis in the Liquid Phase

Abstract

The hydrogenation of carbon monoxide by the Fischer-Tropsch (F-T) process [1] forms saturated and unsaturated compounds of the homologous hydrocarbon series. It permits the synthesis of hydrocarbons ranging from methane to high-melting paraffins with molecular weights above 20,000, depending on the catalyst, temperature, and type of process employed. By-products such as alcohols, aldehydes, ketones, acids, and esters are formed on a smaller scale. Small amounts of aromatic compounds are formed at high temperatures by secondary dehydrocyclization reactions from the primary hydrocarbons formed.     

The Fischer-Tropsch Synthesis in the Liquid Phase

The hydrogenation of carbon monoxide by the Fischer-Tropsch (F-T) process [1] forms saturated and unsaturated compounds of the homologous hydrocarbon series. It permits the synthesis of hydrocarbons ranging from methane to high-melting paraffins with molecular weights above 20,000, depending on the catalyst, temperature, and type of process employed. By-products such as alcohols, aldehydes, ketones, acids, and esters are formed on a smaller scale. Small amounts of aromatic compounds are formed at high temperatures by secondary dehydrocyclization reactions from the primary hydrocarbons formed.     

Nickel and Fischer-Tropsch Synthesis

Nickel has been reviewed as a catalyst and promoter in the Fischer-Tropsch synthesis (FTS). The main obstacle to its industrial application is the formation of volatile carbonyls, causing deactivation and loss of active phase, as well as a somewhat lighter product than from Co or Fe catalysts. Presented are both experimental and theoretical work pointing to suitable techniques for catalyst preparation, its composition and activation, as well as operating conditions where Ni is capable of producing long chain hydrocarbons in the FTS. Some important perspectives are also provided based on thermodynamic calculations and suggestions for further work are included.     

Effect of Sulfur on the Fischer-Tropsch Synthesis

One of the principalcauses of present concern is the current unavailability of alternative sources of fuels for transporation. Other fuel imensive sectors, such as electric power generation, can depend on coal or nuclear fuel to provide the energy if petroleum-based fuels become scare. The transporation sector, on the other hand, is projected to need liquid fuels. Due to the relevant abundance of coal in the United States, it isimperative to find ways of converting coal to liquid fuels. Products from coal liquefaction processes contain a high aromatic content. Though this is a desirable comporent isgasoline, it is a very undersirable one in jet and diesel fuels (Table 1). In even higher boiling materials such as gas oils, the high aromatic content makes it quite difficult to produce gasoline by normal rednery processess. Fischer-Tropsch (FT)synthesis, in which carbon produces mainly straight chain aliphatic hydrogen obtained from coal gastfication are reacted over a caralyst, is the only develped coal-derived process which produces mainly straight chain aliphatic hydrocarbons. Although such aliphatic hydrocarbons are not very desirable on motor gasolines due to their low octare number, diesel and jet fuels containing such aliphatic, hydrocarbons are considered high quality materials. In addition, the higher boiling gas oil traction from the FT process is easily converted to gasoline and diesel fuel by conventional refining technology     

无机膜在费托合成工艺中的应用

费托合成是将煤炭和天然气间接液化制备液体燃料和化学品的一种重要方法,是目前国内外研究的一个热点课题。无机膜作为一种效率高、稳定性好的分离材料,在费托合成中有许多相关的应用研究。讨论了费托合成反应器单元中无机膜的应用研究进展,旨在为费托合成的研究提供一些参考。     

费托合成沉淀铁催化剂性能的研究进展

费托合成（F-F合成）是实现煤间接液化技术的重要环节之一,其关键是开发高活性、选择性和稳定性的催化剂。目前应用的费托合成催化剂主要有铁基和钴基催化剂。铁基催化剂因价格低廉、催化活性和水煤气变换反应（WGS）活性高以及助剂效果明显,而在费托合成催化剂中占有重要的地位。本文对近几年铁基催化剂的特点和发展状况进行了评述,着重分析了催化剂制备过程、助剂和还原活化对其活性和选择性的影响。     

Kinetics modelling of Fischer-Tropsch synthesis over an industrial Fe-Cu-K catalyst

The kinetic experiments of Fischer-Tropsch synthesis (FTS) over an industrial Fe-Cu-K catalyst are carried out in a micro-fixed-bed reactor under the conditions as follows: temperature of 493-542 K, pressure of 10.9-30.9 bar, H₂/CO feed ratio of 0.98-2.99, and space velocity of 4000-10?000 h⁻¹. The effects of secondary reactions of olefins are investigated by co-feeding C₂H₄ and C₃H₆. A detailed kinetics model taking into account the increasingly proven evidence of the olefin re-adsorption mechanism is then proposed. In this model, different sites are assumed for FTS reactions and water gas shift (WGS) reaction, respectively. Rate expressions for FTS reactions are based on the carbide polymerisation mechanism, in which olefin re-adsorption is considered to be a reverse step of olefin desorption reaction. Rate expression for WGS reaction is based on the formate mechanism. An integral reactor model considering both FTS and WGS kinetics is used to describe the reaction system, and the simultaneous estimation of kinetic parameters is conducted with non-linear regression procedure. The optimal model shows that the rate determining steps in FTS reactions proceed via the desorption of hydrocarbon products and the adsorption of CO and the slowest step in WGS reaction is the desorption of gaseous carbon dioxide via formate intermediate species. The activation energies of FTS reactions and WGS reaction are in good agreement with literature values.     

费托合成催化剂的研究进展

介绍了费托合成的研究现状,分析了费托合成催化剂的组成,重点评述了恬性组分、载体、助剂等因素在催化剂制备过程中对催化剂的活性、选择性等方面的影响,并对费托合成催化剂研究领域存在的问题进行了探讨。     

Fischer-Tropsch Synthesis over Modified Cobalt Catalysts

The catalysts of Co/Zr-SiO2 were prepared by precipitation and the promoter of Pt was supported by impregnation. The reducibility of the cobalt oxide and the other physicochemical properties of the catalysts were characterized by TPR, TPD, BET and XPS. With the evaluation of the reduction temperature, the reduction degree increased but the surface area of the catalysts and the adsorption property for reactant CO distinctly decreased; The addition of Pt resulted in the improvement of the reducibility by decreasing the reduction temperature of cobalt oxide species. The FT-synthesis has been performed in a quartz fixed-bed reactor, and the experimental results showed that the best activity for promoted catalyst has been found at the reduction temperature of 400℃, in spite of its uncompleted reduction.     

Bubble Column Reactors and Fischer-Tropsch Synthesis

Three-phase slurry bubble column reactors have been used extensively in a number of chemical, petrochemical, and biochemical process engineering applications. For the success of these operations and their large scale industrial exploitation, it is essential that their transport and chemical characteristics be adequately understood on a mechanistic basis so that appropriate design criteria and optimum operating conditions can be established. It is the purpose of this review to present such available knowledge in relation to chemical catalytic operations. The mass transfer characteristics, catalytic activity, and mixing patterns of different phases necessitate a detailed understanding of the hydrodynamic behavior and catalyst dispersion in slurry bubble column reactors. The current status of these aspects is presented, discussed, and assessed in this review. Chemical and biochemical reactions are exothermic in nature and hence efficient heat removal devices must be installed in the reactor to preserve its isothermal behavior and chemical catalytic activity by avoiding temperature runaway. Extensive work recently conducted from this heat transfer viewpoint is reviewed and appraised. The bubble dynamics, and slurry mixing and movement characteristics of such baffled bubble columns are significantly different from those of unbaffled bubble columns. Very limited information is available on baffled bubble column operations and this is reviewed and critically examined. An important application of the slurry bubble column is in the synthesis of fuel gases on suspended catalyst particle surface to produce chemicals. One such example is the Fischer-Tropsch synthesis of hydrogen and carbon monoxide in what is referred to as indirect coal liquefaction technology. Pilot plant efforts of this nature and their successes are briefly mentioned. Mathematical details and models developed from time to time to characterize catalytic bubble column operations are briefly described and discussed. In the context of available information and its integration presented here, the specific needs for future experimental and theoretical research work are pointed out.     

The Contact State Related Phenomena of Hybrid Catalysts for the Modified Fischer-Tropsch Synthesis

Three-component hybrid catalyst comprised of Co/SiO₂, Pd/β-zeolite and CuO/ZnO/Al₂O₃ with different configurations was applied for the effective production of gasoline-range iso-paraffins from synthesis gas. In the case of the powdery mixture, a killing effect of CuO/ZnO/Al₂O₃ on Co/SiO₂ for the Fischer-Tropsch reaction was observed. On the contrary, individual functions of the above-mentioned components were successfully achieved when the hybrid catalyst with the same composition was prepared in a granular form. The reason is tentatively explained as the feasibility for the interfacial migration of the zinc component from CuO/ZnO/Al₂O₃ to Co/SiO₂.     

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.     

熔铁催化剂超临界相费托合成的研究

在固定床反应器上进行了熔铁催化剂在超临界介质存在条件下的费托合成,并与气相费托合成进行对比。结果表明,由于超临界介质具有类似气体的传质速率和类似液体的溶解能力和热容,减小了催化剂床层过热,减少了催化剂床层积炭,增加了合成气在催化剂表面浓度,促进了产物的脱附,使CO转化率提高,α-烯烃选择性和C5＋选择性增加,甲烷选择性减小。实验考察了温度、压力、合成气比例、合成气空速对超临界相费托合成反应的影响。发现当反应温度或压力低于介质的临界温度及压力时,反应性能迅速下降,说明介质仅在其临界点以上才表现出优良的超临界性能。其他反应条件对超临界相费托合成反应性能的影响类似气相费托合成。     

Nitrided Iron Catalysts for the Fischer-Tropsch Synthesis in the Eighties

About 1950, nitrided iron catalysts for the Fischer-Tropsch synthesis were developed at the Bureau of Mines [1, 2], The nitrided iron catalyst was one of only a few developments in Fischer-Tropsch catalysis that was not anticipated by German work in the period 1925-1945. Small-scale investigations have been summarized [3-6]. The present paper presents a brief review of small-scale work; describes the use of nitrides in pilot-plant units of the slurry [7], oil-circulation [8], and fluidized fixed-bed types [9]; and considers schemes for refining the product.     

费托合成工艺油水分离器的工艺设计

根据卧式油水分离器的特点,分析影响油水分离效果的因素。介绍油水分离器的工艺设计,并讨论其操作。     

钴基催化剂F-T合成的产物分布及稳定性研究

采用浸渍法制备了氧化锆改性γ-Al2O3负载Co-Ru双金属催化剂.在固定床反应器中考察了反应温度、压力、空速和合成气H2/CO比对烃产物分布的影响,进行了552 h的稳定性实验.结果表明,较低的反应温度、较高的压力和较低的空速有利于碳链增长,产物中柴油馏分C12～C18和蜡C19 的选择性高;原料气H2 / CO比提高,甲烷、C2～C4、C5～C11的选择性增加,C12～C18和C19 的选择性下降;在原料气H2/CO比1.58～2.0、反应温度453～513 K、压力1.0～2.5 MPa和空速500～1000 h(1催化剂具有较好的合成重质烃反应性能.在原料气H2 / CO比2.0、反应温度493K、压力1.5 MPa和空速800 h(1下,反应552 h,催化剂的稳定性较好,CO的转化率、C5 选择性分别大于80%和83%.运行时间对产物烃的分布影响不大,产物烃主要有烷烃组成,主要集中在C5～C18,选择性的平均值C1为6.94%,C2～C4 6.20%,C5～C11 33.04%,C12～C18 31.55%,C19 22.27%.     

浆态床FT合成反应器的工程放大

基于Rheinpreussen-Koppers示范装置和Sasol的浆态床Fischer-Tropsch(FT)合成反应器工程放大实践.指出针对目前使用的Fe催化剂而育,浆态床FT合成的总包反应过程以反应控制为主,为浆态床FT合成反应器的放大提供了有利因数.当量直径放大概念在Rheinpreussen-Koppers示范装置的成功应用,为浆态床FT合成反应器的放大和生产能力的扩大提供了实践的基础.Sasol浆态床FT合成反应器的工程放大成功是以其雄厚的固定流化床FT合成反应器的技术为基础的.简介了国内浆态床FT合成技术的工业化研究进展.