Fluid Fischer-Tropsch synthesis

Holtkamp, W. C. A., Kelly, F. T., and Shingles, T. 1977. Circulating fluid bed catalytic reactor for the Fischer-Tropsch synthesis at Sasol II. ChemSA, March, pp. 44—45. 

Supercritical fluids (SCFs) offer several advantages as reaction media for catalytic reactions. These advantages include the ability to manipulate the reaction environment through simple changes in pressure to enhance solubility of reactants and products, to eliminate interphase transport limitations, and to integrate reaction and separation unit operations. Benefits derived from the SCF phase Fischer-Tropsch synthesis (SCF-FTS) involve the gas-like diffusivities and liquid-like solubilities, which together combine the desirable features of the gas- and liquid-phase FT synthesis routes. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

The summary withdrawal of Indiana s support was all the more galling to Mr. Kellogg because it meant Indiana had selected a rival company, Hydrocarbon Research, Inc., to be its partner in development, design, and construction of a hydrocarbon synthesis facility. Mr. P. C. ( Dobie ) Keith had founded Hydrocarbon Research for the specific purpose of developing an American version of Germany s Fischer-Tropsch synthesis. Keith s Hydrocol Process would use bubbling fluid bed reactors. 

The production of gasoline from methanol is a parallel process to the Fischer-Tropsch synthesis of hydrocarbons from syngas (Section 4.7.2). A shape-selective zeolite (ZSM-5) was the catalyst of choice in the process put on stream in 1987 by Mobil in New Zealand however the plant was later closed. The zeolite was used at ca. 400°C in a fluid catalyst reactor, which allows prompt removal of the heat of reaction. 

The Fischer-Tropsch synthesis produces hydrocarbons from Hj and CO. Fluid beds were applied to it in the Hydrocol process using ordinary turbulent beds and in the Kellogg process using fast beds (Fig. 1). Development of the Hydrocol process has been reported by Grekel et al. (G15) and Hall and Taylor (HI). The main difficulties in scale-up of these fluidized beds were incomplete fluidization and low conversion. 

Bubble columns, in which the liquid is the continuous phase, are used for slow reactions. Drawbacks with respect to packed columns are the higher pressure drop and the important degree of axial and radial mixing of both the gas and the liquid, which may be detrimental for the selectivity in complex reactions. On the other hand they may be used when the fluids carry solid impurities that would plug packed columns. In fact, many bubble column processes involve a finely divided solid catalyst that is kept in suspension, like the Rheinpreussen Fischer-Tropsch synthesis, described by Kolbel [1], or the former I. G. Farben coal hydrogen process, or vegetable oil hardening processes. Several oxidations are carried out in bubble columns the production of acetaldehyde from ethylene, of acetic acid from C4 fractions, of vinylchloride from ethylene by oxychlorina-tion, and of cyclohexanone from cyclohexanol. 

When a fluid is compressed and heated above the critical conditions (or to supercritical conditions, sc), the differences between gas and liquid disappear. For carbon dioxide, this occurs for temperatures above 31 °C and pressures above 7.3 MPa. For reactions (such as alkylations, aminations, hydroformylations, hydrogenations and Fischer Tropsch synthesis) occurring in supercritical fluids, the reaction rate is often increased dramatically because of improved desorption of heavy molecules minimizing the oxygen and hydrogen solubility limitations, improved heat transfer, and improved selectivity by a catalyst by minimizing pore diffusion limitations. 

Fan L, Fujimoto K. Fischer-Tropsch synthesis in supercritical fluid characteristics and application. Appl. Catal. A Gen. 1999 186 343-354. 

Elbashir NO, Bukur DB, Durham E, Roberts CB. Advancement of Fischer-Tropsch synthesis via utilization of supercritical fluid reaction media. AIChE J. 2010 56 997-1015. 

Fluidized bed reactors (FBRs) are chemical reactors in which (catalytic) particles interact with a gas stream that is fed from the bottom, such that the mixture (emulsion phase) behaves as a fluid. This type of reactors is often used in the chemical and process industries, where they have gained their popularity due to their excellent heat and mass transfer characteristics. FBRs are used for instance for gas-phase polymerization reactions for polyolefin production (polyethylene, polypropylene), chemical looping combustion or reforming processes, and gas-phase Fischer—Tropsch synthesis. 

Sankaranarayanan K, Shan X, Kevrekidis IG, Sundaresan S. Analysis of drag and virtual mass forces in bubble suspensions using an implicit formulation of the Lattice Boltzmann method, J. Fluid Mech., in press, 2002. Saxena SC. Bubble column reactors and Fischer-Tropsch synthesis. Catal Rev Sci Eng 37 227-309, 1995. 

Shin, M.-S., Park, N., Park, M.-J., Jun, K.-W., and Ha, K.-S. (2013) Computational fluid dynamics model of a modular multichannel reactor for Fischer-Tropsch synthesis maximum utilization of catalytic bed by microchaimel heat exchangers. Chem. Eng. J., 234,23-32. 

For its relevance, propene is one of the most important olefins. Propene is obtained mainly from naphtha steam cracking as a coproduct with ethene, and also as a coproduct from fluid catalytic cracking (FCC) units at refineries. Relatively small amounts are produced by propane dehydrogenation and by Fischer-Tropsch synthesis. Because of the strong global demand for polypropene, acrylonitrile, 0x0 alcohol, and acrylic acid products, present propene supply from conventional sources cannot fulfill the market needs. An alternative route to propene is by applying the metathesis reaction for the conversion of a mixture of ethene and 2-butene into propene (Equation [16.2]). 

K Yokota, Y Hanakata, K Fujimoto. Supercritical phase Fischer-Tropsch synthesis reaction. 3. Extraction capability of supercritical fluids. Fuel 70 989-994, 1991. 

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