Fischer-Tropsch type synthesis

The catalytic hydrogenation of fatty oils, the desulfurization of liquid petroleum fractions by catalytic hydrogenation, Fischer-Tropsch-type synthesis in slurry reactors, and the manufacture of calcium bisulfite acid are familiar examples of this type of process, for which the term gas-liquid-particle process will be used in the following. 

The mass of data and material published during the past twenty-five years on the general subject of the synthesis of hydrocarbons by the catalytic reduction of carbon monoxide with hydrogen has been reviewed adequately by others (18). The object of this paper is to describe the highlights of the development of the Fischer-Tropsch type synthesis, prior to World War II, which have contributed to the present synthesis of liquid fuels from natural gas process and to dwell at greater length on certain of the work done by Hydrocarbon Research, Inc., in this field since the war. 

Fig. 7. Mass spectrum of porphyrin-like pigment, made from CO, Dj, and ND3 by a Fischer-Tropsch-type synthesis (Hayatsu et al., 1972). It resembles porphyrins in optk and chemical characteristics, but lacks the expected peak at mass 290 from the doubly-charged molecular ion...

We assume in the modern world that photosynthesis is balanced with respiration (see also Chapter 2.3.5.3). The reaction (2.42) is of Fischer-Tropsch type synthesis. This is also known from inorganic nature under conditions deep within the earth (Eq. 2.5 and 2.21) and in the upper atmosphere (Eq. 2.35), but under extreme... 

Rushdi Al, Simoneit BR (2001) Lipid formation by aqueous Fischer-Tropsch-type synthesis over a temperature range of 100 to 400 degrees C. Grig Life Evol Biosph 31 103-118. doi 10.1023/A 1006702503954... 

Chemical reactions similar to the Fischer-Tropsch synthesis have been discussed for some years in connection with prebiotic chemistry they are described as Fischer-Tropsch type reactions (FTT). In its technically optimized form, the FIT... 

The physical processes by which natural gas liquids are recovered include phase separation, cooling, compression, absorption, adsorption, refrigeration, and any combination of these. Obviously the definition already stated excludes refinery light volatiles produced by the destructive decomposition of heavy petroleum fractions and it also excludes liquids that may be produced synthetically from natural gas. These distinctions are of economic importance in considering our basic energy reserves. Both the refinery volatiles and the synthetic liquids represent conversion products from other hydrocarbons and the conversion is usually attended by a considerable loss. Thus it has been stated that only about 47% (17) of the energy of natural gas is realized in the liquid hydrocarbon products of the Fischer-Tropsch type of synthesis. 

Dr. Anderson. Part of the hydrocarbons in petroleum could have been formed by a Fischer-Tropsch type reaction at say 200°C., at a different place from that in which the petroleum, which contains porphyrins and other thermally labile compounds, is currently found. The broadest interpretation of the similarity between isomers in petroleum and in the Fischer-Tropsch synthesis is that this result suggests that petroleum is produced by radical reactions rather than carbonium ion mechanisms. 

Hydrocarbon distributions in the Fischer-Tropsch (FT) synthesis on Ru, Co, and Fe catalysts often do not obey simple Flory kinetics. Flory plots are curved and the chain growth parameter a increases with increasing carbon number until it reaches an asymptotic value. a-Olefin/n-paraffin ratios on all three types of catalysts decrease asymptotically to zero as carbon number increases. These data are consistent with diffusion-enhanced readsorption of a-olefins within catalyst particles. Diffusion limitations within liquid-filled catalyst particles slow down the removal of a-olefins. This increases the residence time and the fugacity of a-olefins within catalyst pores, enhances their probability of readsorption and chain initiation, and leads to the formation of heavier and more paraffinic products. Structural catalyst properties, such as pellet size, porosity, and site density, and the kinetics of readsorption, chain termination and growth, determine the extent of a-olefin readsorption within catalyst particles and control FT selectivity. 

Fischer-Tropsch Technology FTS can be carried out in several different reactor types fixed bed, fluidized bed, or slurry phase and at different temperatures. The high-temperature Fischer-Tropsch (HTFT) synthesis runs at 320°C-350°C, at which temperatures typically all products are in the gas phase [22], HTFT is operated in fluidized-bed reactors, with iron catalysts. Selectivities correspond to chain-growth probabilities in the range of 0.70-0.75 and are ideal for gasoline production, but olefins and oxygenates are formed as well and are used as chemicals. 

Fischer-Tropsch (FT) synthesis is accompanied by an extremely large heat evolution (exothermic). To improve the characteristics of heat transfer, liquid phase synthesis using a slurry-type reactor has been developed. Although liquid phase synthesis has been operated using pulverized catalysts (ref. 1), it is interesting to use a catalyst of smaller particles, so-called ultrafine particle (UFP), for the purpose of enhancing the gas-liquid-solid interface contact. 

The synthesis of fatty acids by a Fischer-Tropsch-type process as described in this chapter required the use of a catalyst (meteoritic iron) and a promoter. Potassium carbonate and rubidium carbonate were the only compounds evaluated which unambiguously facilitated the production of fatty acids. These catalytic combinations (meteoritic iron and potassium carbonate or rubidium carbonate) also produced substantial amounts of n-alkenes (in excess of n-alkanes) and aromatic hydrocarbons. A comprehensive study of the nonacidic oxygenated compounds produced in Fischer-Tropsch reactions (20,21) was not made. However, in the products analyzed (all promoted by potassium carbonate), long-chain alcohols and aldehydes were detected. 

McCollom, T.M. Ritter. G. Simoneit, B.R.T. Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions. Orig. Life Evol. Biosph. 1999, 29, 153-166. 

Indeed, the WGS is used to produce hydrogen and is commonly associated with steam reforming of hydrocarbons (natural gas, petroleum gas, naphtha, gasoline, coals, and various types of biomass) (Haring, 2008). The main role of the WGS in industrial processes is to increase the level of hydrogen in the feed for the production of bulk chemicals such as methanol, ammonia, and hydrocarbons by Fischer—Tropsch (FT) synthesis (Grenoble, Estadt, Ollis, 1981). 

Two novel routes to triethylborane have been reported. Irradiation of bromoethane and aluminium powder with ultrasound gives ethyl aluminium sesquibromide which on treatment with triethoxyborane gives triethylborane in good yields and a laser initiated gas phase reaction between diborane and ethene gives yields of upto 91%. Allylic boranes have been prepared from allylpotassiiim derivatives and chloroboranes. Hydrolysis leads to the Isomerised olefin and the technique has been used to transform (+)-a-pinene into (+)-3-pinene. Condensation reactions between allylboranes and acetylenes have been developed into a convenient method for the synthesis of bicyclo[3.3.l]nonane derivatives. Mainly linear alkyl derivatives of 9-BBN have been synthesised from the, reaction of iron carbonyls and the organoborane in a Fischer-Tropsch type reaction. ... 

Medium Pressure Synthesis. Pressures of 500—2000 kPa (5—20 atm) were typical for the medium pressure Fischer-Tropsch process. Cobalt catalysts similar to those used for the normal pressure synthesis were typically used at temperatures ranging from 170 to 200°C ia tubular "heat exchanger" type reactors. 

The Fischer-Tropsch reaction is highly exothermic. Therefore, adequate heat removal is critical. High temperatures residt in high yields of methane, as well as coking and sintering of the catalyst. Three types of reac tors (tubular fixed bed, fluidized bed, and slurry) provide good temperature control, and all three types are being used for synthesis gas conversion. The first plants used tubular or plate-type fixed-bed reactors. Later, SASOL, in South Africa, used fluidized-bed reactors, and most recently, slurry reactors have come into use. 

The use of this type of operation for Fischer-Tropsch synthesis or similar large-scale processes has been referred to in Section II. 

Jacobs G., Ji Y., Davis B.H., Cronauer D., Kropf J., and Marshall C.L. 2007. Fischer-Tropsch synthesis Temperature programmed EXAFS/XANES investigation of the influence of support type, cobalt loading and noble metal promoter addition to the reduction behaviour of cobalt oxide particles. Appl. Catal. A Gen. 333 179-91. 

The potential of carbon nanomaterials for the Fischer-Tropsch synthesis was investigated by employing three different nanomaterials as catalyst supports. Herringbone (HB) and platelet (PL) type nanofibers as well as multiwalled (MW) nanotubes were examined in terms of stability, activity, and selectivity for Fischer-Tropsch synthesis (FTS). 

Concerning the Fischer-Tropsch synthesis, carbon nanomaterials have already been successfully employed as catalyst support media on a laboratory scale. The main attention in literature has been paid so far to subjects such as the comparison of functionalization techniques,9-11 the influence of promoters on the catalytic performance,1 12 and the investigations of metal particle size effects7,8 as well as of metal-support interactions.14,15 However, research was focused on one nanomaterial type only in each of these studies. Yu et al.16 compared the performance of two different kinds of nanofibers (herringbones and platelets) in the Fischer-Tropsch synthesis. A direct comparison between nanotubes and nanofibers as catalyst support media has not yet been an issue of discussion in Fischer-Tropsch investigations. In addition, a comparison with commercially used FT catalysts has up to now not been published. 

Temperature-programmed reduction combined with x-ray absorption fine-structure (XAFS) spectroscopy provided clear evidence that the doping of Fischer-Tropsch synthesis catalysts with Cu and alkali (e.g., K) promotes the carburization rate relative to the undoped catalyst. Since XAFS provides information about the local atomic environment, it can be a powerful tool to aid in catalyst characterization. While XAFS should probably not be used exclusively to characterize the types of iron carbide present in catalysts, it may be, as this example shows, a useful complement to verify results from Mossbauer spectroscopy and other temperature-programmed methods. The EXAFS results suggest that either the Hagg or s-carbides were formed during the reduction process over the cementite form. There appears to be a correlation between the a-value of the product distribution and the carburization rate. 

The aim of this work was to apply combined temperature-programmed reduction (TPR)/x-ray absorption fine-structure (XAFS) spectroscopy to provide clear evidence regarding the manner in which common promoters (e.g., Cu and alkali, like K) operate during the activation of iron-based Fischer-Tropsch synthesis catalysts. In addition, it was of interest to compare results obtained by EXAFS with earlier ones obtained by Mossbauer spectroscopy to shed light on the possible types of iron carbides formed. To that end, model spectra were generated based on the existing crystallography literature for four carbide compounds of... 

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