First ammonia synthesis catalyst

In 1951, A102 catalyst, the first ammonia synthesis catalyst in China, was developed and manufactured by Nanjing Chemical Industry Corporation. A106 and A109 catalysts were developed in 1956 and 1967, respectively, and were widely used in industry, but their activity were low and running temperatures were high. 

Carbon monoxide, which is formed in the steam reforming reaction, deactivates the ammonia synthesis catalyst and must be removed by means of the exothermic water-gas shift reaction, which also maximises hydrogen production. To this end, CO is converted first to more easily removable CO2 ... 

TVA Process (Refs 85, 93 102). In 1933 the Tennessee Valley Authority inherited a World War I plant designed to produce ammonia by a roundabout and obsolete method in the following steps first the manuf of lime and subsequently Ca carbide, then Ca cyanamide, ammonia, nitric acid and finally AN. In 1940 a modern high-pressure ammonia plant was constructed, in which there were used an improved ammonia synthesis catalyst and a water-gas conversion catalyst. During WW II, the TVA produced 29000 tons of anhydrous ammonia, 10000 t of AN liquor, 64000 t of AN crysts and over... 

Around 1900 Fritz Haber began to investigate the ammonia equilibrium [11] at atmospheric pressure and found minimal ammonia concentrations at around 1000 °C (0.012 %). Apart from Haber, Ostwald and Nernst were also closely involved in the ammonia synthesis problem, but a series of mistakes and misunderstandings occurred during the research. For example, Ostwald withdrew a patent application for an iron ammonia synthesis catalyst because of an erroneous experiment, while Nernst concluded that commercial ammonia synthesis was not feasible in view of the low conversion he found when he first measured the equilibrium at 50 - 70 bar [12] - [14],... 

Ammonia has been produced commercially from its component elements since 1909, when Fritz Haber first demonstrated the viability of this process. Bosch, Mittasch and co-workers discovered an excellent promoted Fe catalyst in 1909 that was composed of iron with aluminium oxide, calcium oxide and potassium oxide as promoters. Surprisingly, modem ammonia synthesis catalysts are nearly identical to that first promoted iron catalyst. The reaction is somewhat exothermic and is favoured at high pressures and low temperatures, although, to keep reaction rates high, moderate temperatures are generally used. Typical industrial reaction conditions for ammonia synthesis are 650-750 K and 150-300 atm. Given the technological importance of the... 

Alwin Mittasch joined BASF in 1904 as a co-worker of Carl Bosch and started the search for suitable ammonia synthesis catalysts soon afterward. These efforts were considerably intensified after Haber s successful experiments but, at first, only with limited success. He mentioned (4) In particular iron failed, despite wide variations of the preparation conditions and admixtures. The breakthrough was obtained by accident A sample of Swedish magnetite left over from other experiments was investigated on November 6, 1909, by Mittasch s collaborator Dr. Wolf and exhibited remarkably high ammonia yields. The decisive patent application of January 9, 1910, says the following ... 

The in situ XRD results of Fe304-based ammonia synthesis catalyst are shown in Fig. 7.36. ° It summarizes the evolution of diffracted intensities of three main iron reflections with increasing temperature. First of all, from Fig. 7.36 it can be seen clearly that the growth of the reflections of a-iron is asymmetric, at the end of the reduction the intensity ratio of the first three iron reflections (110), (200) and... 

There is little doubt about the experimental observation of characteristic line broadening in ammonia synthesis catalysts. Accurate measurements were first made by Hosemann et al and these have been confirmed recently. However, all of the arguments cited in favor of the molecular dispersion of the promoter oxide thesis also hold for a different distribution of the promoters. It was pointed out in the conclusion of the work by Borghard and Boudart that there are several... 

The effects of water-vapor and ammonia pretreatment on the initial rate of ammonia synthesis over Fe, Al O /Fe, and K/Al O /Fe surfaces can be summarized as follows. The presence of aluminum oxide promotes the restructuring of iron during the water-vapor pretreatment, but it inhibits the ammonia-induced restructuring. The presence of potassium shows no effect in the ammonia pretreatment and it inhibits water-vapor-induced restructuring of iron. These results suggest that to form the most active ammonia synthesis catalyst, the iron should first be restructured in ammonia before aluminum oxide is added. After aluminum oxide is added the surface should be treated in water vapor, and finally potassium should be added to serve as a promoter at high ammonia synthesis reaction conversions. 

A commercially available ammonia synthesis catalyst is usually supplied with the iron phase in the form of magnetite, which first must be reduced to metallic iron before the catalyst is used. The reduction time is typically from three to five days, although the actual time required is dependent on the plant design and on limitations of equipment, such as the start-up heater. The general principles of reduction are outlined below. More detailed information to suit a specific plant can be obtained from catalyst suppliers. The principal factors governing a plant reduction are the water content of the circulating gas, the gas flowrate, the reduction pressure, and the reduction temperature. 

Oxygen-containing molecules cannot be tolerated in the ammonia synthesis, primarily because they form iron oxide that blocks the active surface. First the CO2 is removed, through a scrubber, by reaction with a strong base. The remaining CO (and CO2) is then removed by the methanation reaction, converting the CO into methane and water. Finally the water is removed by, for example, molecular sieves. Methane does not present problems because it interacts weakly with the catalyst surface. The gas mixture (Tab. 8.6) is compressed to the roughly 200 bar needed for ammonia synthesis and admitted to the reactor. 

Silvery, shiny, and hard. Unique metal, gives off an odor as it forms volatile 0s04 on the surface (oxidation states 81). Osmium is the densest element (22.6 g cm3 record ). Was replaced in filaments (Osram) by the cheaper tungsten. Used in platinum alloys and as a catalyst. Haber s first catalyst in ammonia synthesis was osmium, which fortunately could be replaced by doped iron. The addition of as little as 1 to 2 % of this expensive metal increases the strength of steel (e.g. fountain-pen tips, early gramophone needles, syringe needles). 

---