Iron oxide catalysts

This reaction is first conducted on a chromium-promoted iron oxide catalyst in the high temperature shift (HTS) reactor at about 370°C at the inlet. This catalyst is usually in the form of 6 x 6-mm or 9.5 x 9.5-mm tablets, SV about 4000 h . Converted gases are cooled outside of the HTS by producing steam or heating boiler feed water and are sent to the low temperature shift (LTS) converter at about 200—215°C to complete the water gas shift reaction. The LTS catalyst is a copper—zinc oxide catalyst supported on alumina. CO content of the effluent gas is usually 0.1—0.25% on a dry gas basis and has a 14°C approach to equihbrium, ie, an equihbrium temperature 14°C higher than actual, and SV about 4000 h . Operating at as low a temperature as possible is advantageous because of the more favorable equihbrium constants. The product gas from this section contains about 77% H2, 18% CO2, 0.30% CO, and 4.7% CH. ... 

Research in catalysts for ammonia manufacture is stiU going on, and though the use of supported metals such as mthenium may be two to three times as active as promoted iron oxide, catalysts 50—100 times more active than promoted iron oxide are required to affect process economics significantly. 

Liquefaction. Liquefaction of coal to oil was first accompHshed in 1914. Hydrogen was placed with a paste of coal, heavy oil, and a small amount of iron oxide catalyst at 450° and 20 MPa (200 atm) in stirred autoclaves. This process was developed by the I. G. Earbenindustrie AG to give commercial quaUty gasoline as the principal product. Twelve hydrogenation plants were operated during World War II to make Hquid fuels (see CoAL... 

The compressed synthesis gas is dried, mixed with a recycle stream, and introduced into the synthesis reactor after the recycle compressor. The gas mixture is chilled and liquid ammonia is removed from the secondary separator. The vapor is heated and passed into the ammonia converter. The feed is preheated inside the converter prior to entering the catalyst bed. The reaction occurs at 450-600°C over an iron oxide catalyst. The ammonia synthesis reaction between nitrogen, N2, and hydrogen, Hj, is... 

Most commercial liquid ammonia contains up to several ppm of colloidal iron compounds, possibly the iron oxide catalyst commonly used in manufacturing ammonia. Reduction converts these compounds to colloidal iron which strongly catalyzes the reaction between alcohols and sodium and potassium. The reaction of lithium with alcohols is also catalyzed by iron but to a markedly lesser degree. The data in Table 1-4 illustrate the magnitude of these catalytic effects. The data of Table 1-5 emphasize how less than 1 ppm... 

Fig. 1(b) represents the selectivity to styrene as a ftmcfion of time fijr the above catal ts. It is observed that the selectivity to styrene is more than 95% over carbon nauofiber supported iron oxide catalyst compared with about 90% for the oxidized carbon nanofiber. It can be observed that there is an increase in selectivity to styrene and a decrease in selectivity to benzene with time on stream until 40 min. In particrdar, when the carbon nanofiber which has been treated in 4M HCl solution for three days is directly us as support to deposit the iron-precursor, the resulting catalyst shows a significantly lows selectivity to styrene, about 70%, in contrast to more than 95% on the similar catalyst using oxidized carbon nanofiber. The doping of the alkali or alkali metal on Fe/CNF did not improve the steady-state selectivity to styrene, but shortened the time to reach the steady-state selectivity. 

Suppose you prepared an iron oxide catalyst supported on an alumina support. Your aim is to use the catalyst in the metallic form, but you want to keep the iron particles as small as possible, with a degree of reduction of at least 50%. Hence, you need to know the particle size of the iron oxide in the unreduced catalyst, as well as the size of the iron particles and their degree of reduction in the metallic state. Refer to Chapters 4 and 5 to devise a strategy to obtain this information. (Unfortunately for you, it appears that electron microscopy and X-ray diffraction do not provide useful data on the unreduced catalyst.)... 

CO conversion is carried out over chromium-promoted iron oxide catalyst employing two stages of catalytic conversion the plant also incorporates a saturator and desaturator operating with a hot water circuit. 

The propellant mixture in each solid rocket booster of the Space Shuttle contains ammonium perchlorate ( the oxidizer, 69.6% by weight), aluminum ( the fuel, 16% by weight), an iron oxide catalyst (0.4% by weight), a polymeric binder that... 

In the cracker, HRO is cracked over iron oxide catalyst at 540°C in the presence of steam with the production of gas, liquid products, coke (12-16%), and hydrogen (by reaction of wustite with steam)... 

Fukase, S. and Suzuka, T., Residual oil cracking with generation of hydrogen Deactivation of iron oxide catalyst in the steam-iron reaction, Appl. Catal. A General, 100,1,1993. 

Dictor, R.A., and Bell, A.T. 1986. Fischer-Tropsch synthesis over reduced and unreduced iron oxide catalysts. J. Catal. 97 121-36. 

Hua, J., Wei, K., Zheng, Q., and Lin, X. 2004. Influence of calcination temperature on the structure and catalytic performance of Au/iron oxide catalysts for water-gas shift reaction. Appl. Catal. A Gen. 259 121-30. 

Adkins-Peterson The oxidation of methanol to formaldehyde, using air and a mixed molybdenum/iron oxide catalyst. Not an engineered process, but the reaction which formed the basis of the Formox process. 

Claus A process for removing hydrogen sulfide from gas streams by the catalyzed reaction with sulfur dioxide, producing elementary sulfur. The process has two stages in the first, one third of the hydrogen sulfide is oxidized with air to produce sulfur dioxide in the second, this sulfur dioxide stream is blended with the remainder of the hydrogen sulfide stream and passed over an iron oxide catalyst at approximately 300°C. The resulting sulfur vapor is condensed to liquid sulfur. 

The steam also reacts with coke deposits on the iron oxide catalyst, forming CO2, giving the catalyst a longer, more active lifetime. The onstream factor of the styrene plant is extended by reducing the shutdown frequency for catalyst regeneration or replacement. 

The degradation of the B02 was conducted by using iron oxide catalyst supported on cerium oxide as a heterogeneous Fenton catalyst in the presenee of H2O2. The effect of the... 

Hsueh, C-L Huanga, Y-H Wang, C-C Chena, C-Y. Photoassisted Fenton degradation of nonbiodegradable azo-dye (Reactive Black 5) over a novel supported iron oxide catalyst at neutral pH. Journal of Molecular Catalysis A Chemical, 2006 245, 78-86. 

Fig. 4.1 outlines the Haber process to make ammonia. The reaction of nitrogen and hydrogen gases was first studied by Haber with Nemst and Bosch in the period 1904-1916. The two gases are adjusted to a 3 1 H2 N2 mixture and compressed to 2,000-10,000 psi (150-600 atm). The mixture is filtered to remove traces of oil, joined to recycled gases, and is fed to the reactor at 400-600°C. The reactor (Fig. 4.2) contains an iron oxide catalyst that reduces to a porous iron metal in the H2 N2 mixture. Ruthenium on... 

One of the simplest examples for such effects is the oxidation of ammonia with iron oxide-bismuth oxide as a catalyst. Here, the addition of bismuth oxide results in the formation of nitrous oxides as the main product whereas an iron oxide catalyst without bismuth oxide yields nitrogen almost exlcusively. Selectively guiding catalysts become increasingly important in the synthesis of organic compounds, e.g., in the hydrogenation of carbon monoxide where the type of obtainable product can be varied, within wide limits, by the kinds of catalysts and promoters which are employed. 

The oxide surface has structural and functional groups (sites) which interact with gaseous and soluble species and also with the surfaces of other oxides and bacterial cells. The number of available sites per unit mass of oxide depends upon the nature of the oxide and its specific surface area. The specific surface area influences the reactivity of the oxide particularly its dissolution and dehydroxylation behaviour, interaction with sorbents, phase transformations and also, thermodynamic stability. In addition, specific surface area and also porosity are crucial factors for determining the activity of iron oxide catalysts. 

Tab. 19.3 Industrial synthesis reactions involving iron oxide catalysts.

B. (1998) A study of the structural and catalytic effect of sulphation on iron oxide catalysts prepared from goefhite and ferrihydrite precursors for methane oxidation. Catalysis Letters 53 7—13... 

---