Promoted iron catalyst

The feed to the shift converter contains large amounts of carbon monoxide which should be oxidized. An iron catalyst promoted with chromium oxide is used at a temperature range of 425-500°C to enhance the oxidation. 

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... 

For most catalysts it is generally observed that as the temperature is increased, the selectivity shifts towards the lighter products, the olefinity of the products decrease and less alcohols are formed. Table II illustrates these effects for an experimental iron catalyst promoted with an intermediate amount of alkali. 

In the original derivation of (305), it was supposed (40) that the nitrogen adsorption equilibrium on the catalyst follows the logarithmic isotherms (i.e., that the surface is evenly nonuniform). In this case y — 0 and, according to (143) and (164), m — a, n — / . Experiments with iron catalyst promoted with A1203 and K20 gave m = 0.5. This was interpreted as a = 0.5 (93). 

To date, the best results obtained for an iron catalyst in a slurry reactor have been reported by Kolbel with a precipitated iron catalyst promoted with potassium and copper.2 Current efforts in our laboratory have been aimed at developing a catalyst with activity and productivity superior to the catalyst used by Kolbel. Most research efforts have focused on precipitated and fused iron catalysts however, promising results have been reported for... 

Bulatnikov et al. (340) studied the effects of promoters on sulfur resistance of iron by measuring the amount of radioactive H2S adsorbed on iron catalysts promoted with A1203 and/or K20. They reported irreversible deactivation of Fe promoted with A1203, A1203 + K20, or KzO after 0.8, 1.5, and 5 monolayers of sulfur had been adsorbed. In other words, the presence of K20 was responsible for increasing sulfur adsorption capacity, although it was not clear upon which portion of the surface sulfur had adsorbed. It was also reported that A1203 was necessary to prevent volatilization of K20. 

From the early days of ammonia production to the present, the only catalysts that have been used have been iron catalysts promoted with nonreducible oxides. Recently, a ruthenium-based catalyst promoted with rubidium has found industrial application. The basic composition of iron catalysts is still very similar to that of the first catalyst developed by BASF. 

The ammonia synthesis catalyst problem could be considered solved when the catalytic effectiveness of iron in conversion and its onstream life were successfully and substantially improved by adding reduction-resistant metal oxides [232] (Table 15). The iron catalysts promoted with aluminum and potassium oxides proved to be most serviceable [238]. Later, calcium was added as the third activator. Development work in the United States from 1922 can be found in [239]. 

Hydropyrolysis process gives the higher degree of mixture conversion and higher yield of light liquids as compare to pyrolysis in an inert atmosphere. Observed in some cases non-additive effects indicate that the interaction between wood and plastic derived products takes place during mixture thermal treatment. The more pronounced synergistic effects were detected for hydropyrolysis process. Iron catalysts promote the formation of liquid hydrocarbons from biomass/plastic mixtures and influence on their coit sition. 

The selective synthesis of lower olefms(C2 - C4) by the CO2 hydrogenation over Iron catalysts promoted with Potassium and supported on ion exchanged(H, K) Zeolite-Y... 

Formally, ammonia synthesis is closely related to Fischer-Tropsch synthesis. Industrial operation involves the use of an iron catalyst promoted with calcium and potassium oxides. However, the reason we consider this process here is not directly in connection with alkali promotion of the catalyst. We are concerned with a remarkable achievement reported by Yiokari et al. [15], who use a ton-conducting electrolyte to achieve electrochemical promotion of a fully promoted ammonia synthesis catalyst operated at elevated pressure. Specifically, they make use of a fully promoted industrial catalyst that was interfaced with the proton conductor CaIno.iZro.903-a operated at 700K and 50 bar in a multipellet configuration. It was shown that under EP the catalytic rate could be increased by a factor of 13 when... 

Four iron catalysts promoted with varying amounts of potassium were reacted at 215°C in synthesis gas for 24 h and then tested using TPSR. The results of the experiments are shown in Figure 6, which tabulates the quantities of amorphous CHx carbon, carbidic, and graphitic carbon found on each catalyst. The most graphite formed on the unpromoted iron... 

From a study of the mechanism of the poisoning action of water vapors mill oxygen on iron ammonia catalysts 21 and by making certain assumptions, Almquistsu has been able to calculate that in pure iron catalysts about one atom in two thousand is active toward ammonia synthesis, whereas in iron catalysts promoted by alumina about one atom in two hundred is active. This shows the remarkable added activity obtainable by the use of promoters. That the effect is complicated beyond any simple explanation is evidenced further by some of the results of Almquist and Black, These workers have shown that whereas an iron-alumina catalyst shows greater activity toward ammonia synthesis at atmospheric pressure than an iron catalyst containing both alumina and potassium oxide, the hitter catalyst is 50 per cent more active when the pressure is raised to 1(X) atmospheres. 

Fischer s experiments with iron catalysts promoted with alkalies showed that they increased in efficiency with the strength of the base, with the exception of caesium. Working with catalysts prepared by calcining steel turnings with potassium hydroxide, Frolich and Lewis 1J7 showed that with a gas containing 40 per cent carbon monoxide passed into the reactor at a space velocity of 1250 at 200 atmospheres and 325° to 335° C. the best yields were obtained when the base comprised 2.2 per cent of the catalysts (calculated as K20). From this it appears that a strong base present in small amount with iron as the catalyst enables the best yields of liquid products to be obtained. This conclusion has been confirmed by the work of Audibert and Raineau. 

The reaction does not occur at 550° C. without a catalyst and at 400° C. requires an active catalyst for good conversion. The reaction goes readily at 500° C. in the presence of iron catalysts promoted with alumina... 

C. carbon monoxide is quickly chemically adsorbed by the surface of a pure iron catalyst in amounts sufficient to cover the entire surface (4). Accordingly, it seemed reasonable to conclude that whenever the volume of CO chemisorption on an iron catalyst promoted with AljOa and KjO was smaller than the volume of nitrogen required to form a monolayer over the entire catalyst, one had an indication that part of the surface was being covered up by promoter molecules that were concentrating preferentially in the surface layer. For the doubly promoted catalyst, such measurements... 

Metallic iron itself has very low FTS activity. Although, under operational conditions the activity of metallic iron gradually increases over time. To improve the FTS activity and tune the product selectivity of iron catalysts, promoters such as alkali metals, transition metals and other additives are incorporated into the catalyst structure. Typical promoters and additives include copper, potassium and silica. Copper acts to enhance the rate of catalyst activation, silica improves the dispersion of catalytically active iron species, while alkali metals aid carbon-monoxide dissociation from surface iron. ... 

As mentioned previously, ammonia synthesis is commonly carried out at 400 -450°C, using an iron catalyst promoted with potassium and alumina. The gas entering the converter consists mainly of gas circulated in the loop with a relatively small amount of fresh synthesis gas called makeup gas. The gas entering the converter contains N2 and H2 in a 1 3 ratio plus 10%-14% inerts" and about 2% NH3. The "inerts consist mainly of meth-... 

During their initial studies about the airmionia synthesis catalysts, Bosch et alA found that the catalysts obtained from the reduction of natural magnetite are better than the catalysts from other iron compoimds. Almquist et alA studied the relation between the activity of iron catalyst and the oxidization degree before its reduction and found that those catalysts, of which the ratio of Fe +/Fe + is closer to be 0.5 and compositions closer to magnetite, has the highest activity. Bridger et alA further studied the fused iron catalysts promoted with binary promoters AI2O3-K2O,... 

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