Iron catalyst synthesis

K. Fischer, Comparison of I. G. Work on Eischer Synthesis, Technical OilMission Repod, Reel 13, Library of Congress, Washington, D.C., July 1941. H. Pichler, Medium Pressure Synthesis on Iron Catalyst, (Pat. Appl), Technical OilMission Report, Reel 100, Library of Congress, Washington, D.C., 1937-1943. 

A. Nielsen, M Investigation on Promoted Iron Catalysts for the Synthesis ofAmmonia,] A. GjeUemps Eodag, Copenhagen, Denmark, 1968, p. 12. 

In 1974 a 1000 t/d ammonia plant went into operation near Johaimesburg, South Africa. The lignitic (subbituminous) coal used there contains about 14% ash, 36% volatile matter, and 1% sulfur. The plant has six Koppers-Totzek low pressure, high temperature gasifiers. Refrigerated methanol (—38° C, 3.0 MPa (30 atm)) is used to remove H2S. A 58% CO mixture reacts with steam over an iron catalyst to produce H2. The carbon dioxide is removed with methanol (at —58° C and 5.2 MPa (51 atm)). Ammonia synthesis is carried out at ca 22 MPa (220 atm) (53) (see Ammonia). 

A. Nielsen, Nn Investigation on Promoted Iron Catalyst for the Synthesis ofNmmonia, 3rd ed., Jul. GjeUemps Fodag, Denmark, 1968, pp. 16—17. 

If bromine is used in equation 8, carbon tetrabromide [558-13-4] is formed. With a minor amount of iodine present, and in the absence of iron catalyst, carbon disulfide and chlorine react to form trichioromethanesulfenyl chloride (perchloromethyl mercaptan [594-42-3]), CCI3SCI, which can be reduced with staimous chloride or tin, and hydrochloric acid to form thiophosgene (thiocarbonyl chloride [463-71-8], CSCI2, an intermediate in the synthesis of many organic compounds (see Sulfurcompounds). 

Hydrocarbons from Synthesis Gas and Methanol. Two very important catalytic processes in which hydrocarbons are formed from synthesis gas are the Sasol Eischer-Tropsch process, in which carbon monoxide and hydrogen obtained from coal gasification are converted to gasoline and other products over an iron catalyst, and the Mobil MTG process, which converts methanol to gasoline range hydrocarbons using ZSM-5-type 2eohte catalysts. 

Fig. 13. Flowsheet of medium pressure synthesis, fixed-bed reactor (Lurgi-Ruhrchemie-Sasol) having process conditions for SASOL I of an alkaline, precipitated-iron catalyst, reduction degree 20—25% having a catalyst charge of 32—36 t, at 220—255°C and 2.48 MPa (360 psig) at a fresh feed rate of...

For the synthesis of ammonia, Nj -i- 3H2 —> 2NH3, over an iron catalyst, develop the rate expression for the following mechanism... 

Single-wall tubes. Following the synthesis studies of stuffed nanocapsules, single-wall (SW) tubes were discovered in 1993(9,10]. SW tubes are found in chamber soot when iron[9] and cobalt[10] were used as catalysts, and for nickelfl 1,40] they grow on the surface of the cathode slag. For iron catalyst. 

Basically, tliere are two classes of anunonia converters, tubular and multiple bed. The tubular bed reactor is limited in capacity to a maximum of about 500 tons/day. In most reactor designs, the cold inlet synthesis gas flows tlirough an annular space between the converter shell and tlie catalyst cartridge. This maintains the shell at a low temperature, minimizing the possibility of hydrogen embrittlement, which can occur at normal synthesis pressures. The inlet gas is then preheated to syntliesis temperature by the exit gas in an internal heat e.xchaiiger, after which it enters tlie interior of the anunonia converter, which contains tlie promoted iron catalyst. 

Remaining trace quantities of CO (which would poison the iron catalyst during ammonia synthesis) are converted back to CH4 by passing the damp gas from the scmbbers over a Ni methanation catalyst at 325° CO -t- 3H2, CRt -t- H2O. This reaction is the reverse of that occurring in the primary steam reformer. The synthesis gas now emerging has the approximate composition H2 74.3%, N2 24.7%, CH4 0.8%, Ar 0.3%, CO 1 -2ppm. It is compressed in three stages from 25 atm to 200 atm and then passed over a promoted iron catalyst at 380-450°C ... 

Shortly after World War I, Badische Amlin patented the catalytic conversion of synthesis gas to methanol, and Fischer and Tropsch (F-T) announced a rival process in which an iron catalyst converted synthesis gas into a mixture of oxygenated hydrocarbons. Later,... 

Diy, M. E. (1990). Fischer-Tropsch Synthesis over Iron Catalysts, Spring 1990 A.I.Ch.E. Meeting, Orlando, Florida. March 18-22, 1990. 

Fischer Tropsch synthesis is catalyzed by a variety of transition metals such as iron, nickel, and cobalt. Iron is the preferred catalyst due to its higher activity and lower cost. Nickel produces large amounts of methane, while cobalt has a lower reaction rate and lower selectivity than iron. By comparing cobalt and iron catalysts, it was found that cobalt promotes more middle-distillate products. In FTS, cobalt produces... 

Hydrogen cyanide reactions catalysts, 6,296 Hydrogen ligands, 2, 689-711 Hydrogenolysis platinum hydride complexes synthesis, 5, 359 Hydrogen peroxide catalytic oxidation, 6, 332, 334 hydrocarbon oxidation iron catalysts, 6, 379 reduction... 

The effect of alkali additives on N2 chemisorption has important implications for ammonia synthesis on iron, where alkali promoters (in the form of K or K20) are used in order to increase the activity of the iron catalyst. 

C.G. Yiokari, G.E. Pitselis, D.G. Polydoros, A.D. Katsaounis, and C.G. Vayenas, High pressure electrochemical promotion of ammonia synthesis over an industrial iron catalyst, /. Phys. Chem. 104, 10600-10602 (2000). 

The reactant is adsorbed on the catalyst s surface. As a reactant molecule attaches to the surface of the catalyst, its bonds are weakened and the reaction can proceed more quickly because the bonds are more easily broken (Fig. 13.36). One important step in the reaction mechanism of the Haber process for the synthesis of ammonia is the adsorption of N2 molecules on the iron catalyst and the weakening of the strong N=N triple bond. 

C-C and C-E (E = heteroatom) bond formations are valuable reactions in organic synthesis, thus these reactions have been achieved to date by considerable efforts of a large number of chemists using a precious-metal catalysts (e.g., Ru, Rh, and Pd). Recently, the apphcation range of iron catalysts as an alternative for rare and expensive transition-metal catalysts has been rapidly expanded (for recent selected examples, see [12-20, 90-103]). In these reactions, a Fe-H species might act as a reactive key intermediate but also represent a deactivated species, which is prepared by p-H elimination. 

Mossbauer spectroscopy is a specialist characterization tool in catalysis. Nevertheless, it has yielded essential information on a number of important catalysts, such as the iron catalyst for ammonia and Fischer-Tropsch synthesis, as well as the CoMoS hydrotreating catalyst. Mossbauer spectroscopy provides the oxidation state, the internal magnetic field, and the lattice symmetry of a limited number of elements such as iron, cobalt, tin, iridium, ruthenium, antimony, platinum and gold, and can be applied in situ. 

Figure4.17. Mossbauer spectra give detailed information on the state of iron in a Ti02-supported iron catalyst after different treatments. Here reduction was in H2 at 675 K for 18 h, and FTS stands for Fischer-Tropsch synthesis. [Adapted from A.M. van der Kraan, R.C.H. Nonnekens, F. Stoop and J.W. Niemantsverdriet, Appl. Catal. 27 (1986) 285.]...

Figure 7.22. NH3 concentration as a function of reactor length in the synthesis of ammonia with a potassium-promoted iron catalyst. The exit concentration is 19 % and corresponds to...

Bahome, M., Jewell, L., Hildebrandt, D., Glasser, D., and Coville, N. J. 2005. Fischer-Tropsch synthesis over iron catalysts supported on carbon nano tubes. Applied Catalysis A General 287 60-67. 

Niemantsverdriet, J. W., and van der Kraan, A. M. 1981. On the time-dependent behavior of iron catalysts in Fischer-Tropsch synthesis. J. Catal. 72 385-88. 

Luo, M., O Brien, R.J., Bao, S., and Davis, B.H. 2003. Fischer-Tropsch synthesis Induction and steady-state activity of high-alpha potassium promoted iron catalysts. Appl. Catal. A Gen. 239 111-20. 

Bukur, D.B., Mukesh, D.S., and Patal, A. 1990. Promoter effects on precipitated iron catalysts for Fischer-Tropsch synthesis. Ind. Eng. Chem. Res. 29 194—204. 

Fischer-Tropsch synthesis can be regarded as a surface polymerization reaction since monomer units are produced from the reagents hydrogen and carbon monoxide in situ on the surface of the catalyst. Hence, a variety of hydrocarbons (mainly n-paraffines) are formed from hydrogen and carbon monoxide by successive addition of C, units to hydrocarbon chains on the catalyst surface (Equation 12.1). Additionally, carbon dioxide (Equation 12.3) and steam (Equations 12.1 and 12.2) are produced C02 affects the reaction just a little, whereas H20 shows a strong inhibiting effect on the reaction rate when iron catalysts are used. 

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