Fischer-Tropsch product

Fig. 4. Product compositions as a function of carbon number for the Shell middle distillate synthesis process (a) the Fischer-Tropsch product following...

During the past several decades, coal made hydrogen is mainly used in areas for the production of chemicals such as ammonia, methanol, methane, and Fischer-Tropsch products (Figure 3.2). 

The FTS was conducted at varying temperatures (from 483 to 513 K) over approximately 50 h of reaction time in order to investigate the reaction kinetics achieved with the respective catalysts. A typical conversion curve using the Co/ HB catalyst as an example is shown in Figure 2.3. After a short settling phase (caused by the pore filling of liquid Fischer-Tropsch products) of only about 4 h, steady-state conditions were reached. In the observed synthesis period of 50 h no deactivation of the catalysts was detected. However, industrially relevant experiments over several weeks are still outstanding. 

FIGURE 9.11 Ideal polymerization model of Fischer-Tropsch synthesis and ideal Fischer-Tropsch product composition. 

The carbon number distribution of Fischer-Tropsch products on both cobalt and iron catalysts can be clearly represented by superposition of two Anderson-Schulz-Flory (ASF) distributions characterized by two chain growth probabilities and the mass or molar fraction of products assigned to one of these distributions.7 10 In particular, this bimodal-type distribution is pronounced for iron catalysts promoted with alkali (e.g., K2C03). Comparing product distributions obtained on alkali-promoted and -unpromoted iron catalysts has shown that the distribution characterized by the lower growth probability a, is not affected by the promoter, while the growth probability a2 and the mass fraction f2 are considerably increased by addition of alkali.9 This is... 

With the exception of methane and the C2 fraction, the carbon number distribution of Fischer-Tropsch products can be well represented by superposition of two ASF distributions ... 

Henry s law was also used to calculate the H2, CO, and H20 concentrations in the liquid Fischer-Tropsch products (wax) at the entrance of the pore (z = 0) ... 

Zhan, X., Davis, B. H. 2002. Assessment of internal diffusion limitation on Fischer-Tropsch product distribution. Applied Catalysis A General 236 149-61. 

Schulz, H., Claeys, M. 1999. Kinetic modelling of Fischer-Tropsch product distributions. Appl. Catal. A 186 91. 

The primary product from Fischer-Tropsch synthesis is a complex multiphase mixture of hydrocarbons, oxygenates, and water. The composition of this mixture is dependent on the Fischer-Tropsch technology and considerable variation in carbon number distribution, as well as the relative abundance of different compound classes is possible. The primary Fischer-Tropsch product has to be refined to produce final products, and in this respect, it is comparable to crude oil. The primary product from Fischer-Tropsch synthesis can therefore be seen as a synthetic crude oil (syncrude). There are nevertheless significant differences between crude oil and Fischer-Tropsch syncrude, thus requiring a different refining approach.1... 

Olefins in the C3-320°C range had significant synthetic value, and additional olefins were produced by thermal cracking in some facilities. Acid-catalyzed and thermal olefin oligomerization were important technologies for the upgrading of Fischer-Tropsch products. 

The Arge Fe-LTFT syncrude (Table 18.8)29 was much heavier than the syncrude of the two German Co-LTFT processes (Table 18.2). The Arge Fe-LTFT syncrude exemplified a high a-value Fischer-Tropsch product with a significant linear paraffinic wax fraction. The syncrude (Table 18.8) from the Kellogg Fe-HTFT synthesis was very similar in carbon number distribution to that of Hydrocol Fe-HTFT synthesis (Table 18.5). 

Dancuart, L. P., De Haan, R., and De Klerk, A. 2004. Processing of primary Fischer-Tropsch products. Stud. Surf. Sci. Catal. 152 482-532. 

There are two main reasons for the economic importance of Fischer-Tropsch production in South Africa (a) the existence there of extremely large coal deposits which can be mined at low cost, and (b) that nation s wish to become independent of external oil supplies. 

B. M. Karandikar, B. I. Morsi, Y. T. Shah and N. L. Carr, Effect of water on the solubilities and mass transfer coefficients of gases in a heavy fraction of Fischer-Tropsch products, Can. J. Chem. Eng., 1987, 65, 973-981. 

Oxygenates from paraffin stream (Fischer Tropsch product) NaX, CaA [164]... 

Isoalkanes can also be synthesized by using two-component catalyst systems composed of a Fischer-Tropsch catalyst and an acidic catalyst. Ruthenium-exchanged alkali zeolites288 289 and a hybrid catalyst290 (a mixture of RuNaY zeolite and sulfated zirconia) allow enhanced isoalkane production. On the latter catalyst 91% isobutane in the C4 fraction and 83% isopentane in the C5 fraction were produced. The shift of selectivity toward the formation of isoalkanes is attributed to the secondary, acid-catalyzed transformations on the acidic catalyst component of primary olefinic (Fischer-Tropsch) products. 

Similor Compositions of Alkones from Cool, Petroleum, Natural Gas, and Fischer-Tropsch Product... 

Possible inter relationships of natural substances are important. Similarities of the low molecular weight alkane isomers from crude oil and Fischer-Tropsch synthesis product have been reported. A similar composition for high temperature coal carbonization has been found. The C4 to C7 alkane isomers from these sources can be calculated quantitatively with equations developed for Fischer-Tropsch products. A reversal of the concentrations of the monomethyl isomers from CG (2 Me > 3 Me) to C7 (3 Me > 2 Me) occurs in all three products comparisons at higher carbon numbers indicate some dissimilarities. Naphthene isomers for crude oil and high temperature coal carbonization also have similar compositions. Aliphatic hydrocarbons from low temperature coal processes are considerably different. The C1 isotopic composition of pure compounds from the various sources are being compared in order to provide information on their origin. 

Crude Oils. Part a of Table I compares branched alkanes observed in Fischer-Tropsch products with those observed in a representative crude oil. Part b predicts Fischer-Tropsch product along with the relative concentrations of isomers in terms of a and /, and part c predicts crude oil compositions. In this last portion of Table I comparisons are given for branched isomers for / = 0.176. The comparison of observed and predicted normal Ce and C is not very similar with f = 0.176 however, as noted in the footnote, a change of / value to 0.1 produces a very close comparison for the normal compounds. 

Fischer-Tropsch and Crude Oil. Other similarities between crude oil and Fischer-Tropsch products should be mentioned. First, polynuclear condensed aromatics are produced in syntheses involving catalytic hydrogenation of carbon monoxide as shown in the Fischer-Tropsch work of Weitkamp (3). The catalysis group in our laboratory attempted catalytic hydrogenations at elevated temperatures and found production of considerable amounts of aromatics as large as pyrene. This evidence is cited to indicate that the aromatics in petroleum could possibly be derived from catalytic syntheses of the Fischer-Tropsch type. Another similarity has been shown by the product obtained from... 

The data recently published by Ouchi and Imuta (15) on a chloroform extract of Yubari coal also indicates similarities to petroleum. Branching is greater at the low carbon numbers and drops off at higher carbon numbers as in crudes (II) and Fischer-Tropsch product (17). The other similarity to crude oil is noted in the odd-even alternation of normal alkanes from Cm to C25 with the odd carbon number alkanes predominating. 

Other data on analyses of coal products have been given by Girling (9). A list of alkanes found, but not quantitatively determined, from C through C7, indicates that the normals and monomethyl isomers predominate. This again is similar to crude oil and Fischer-Tropsch product. 

Milton Denekas. The implication of the relation of crude oil composition to a Fischer-Tropsch product is that oil has been produced by a synthetic process (building-up) rather than by a degradative process. Can you assume that the products from coal pyrolysis are also produced by a synthetic building-up) process rather than by degradation ... 

This is the well-known Anderson-Flory-Schultz (ASF) distribution. Figure 5.4.4 shows how the Fischer-Tropsch product distribution depends on the chain-growth probability, a. 

Figure 5.4.4 Fischer-Tropsch product distributions in terms of interesting hydrocarbon fractions as a function of the chain-growth probability, a, as calculated with Equation (23). The insert shows a few ASF plots according to Equation (24).

The presence of oxygenates, even at low concentrations, and in particular the presence of carboxylic acids and methyl alkyl ketones in the Fischer-Tropsch product obtained by catalysis on iron, is a strong indication that CO insertion can occur (Figure 5). 

The addition of OH has also been proposed to lead to oxygenates in the Fischer-Tropsch product (65), but the variety of oxygen-containing products cannot be explained solely by OH addition (e.g., the formation of methyl alkyl ketones would not be explainable). Moreover, on cobalt, the coverage with OH is known to be low (29), and hence, addition of OH is an unlikely reaction. 

Assuming BEP-type relationships to be valid, we can make a prediction of the selectivity of fhe Fischer-Tropsch reaction as a function of the M—C bond energy. In Figure 10, a schematic representation is given of the relative rates of production of particular groups of Fischer-Tropsch products as a function of fhe M—C interaction energy. Four types of reaction are compared coke or carbide formation, hydrocarbon chain growth, CH4 formation, and CO dissociation. 

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