Swedish, magnetite

Still following the macro-structural hypothesis which we favored at that time, we abondoned the idea of a specific favorable influence of flux promoters and assumed instead that the cause for the success of the magnetite experiment was the compact porous structure of the iron sponge which was formed in the test oven by the reduction of the Swedish ore. An apparent support of this idea was that contrary to the favorable action of the dense iron sponge obtained from magnetite, catalysts of a looser structure such as, e.g., iron asbestos preparations had always been particularly ineffective. 

At first this new assumption seemed confirmed by the enhanced activities of catalysts which were obtained by pressing loose powders of iron oxide into dense tablets. Soon, however, it was found that magnetites of another origin than the Swedish specimen yielded no ammonia, or only negligible amounts, in spite of the dense structure of their reduction products. 

Another type of economically important Fe ore occurs in so-called shams. Skarn is an old Swedish name for a gangue formation from the Archean age produced by me-tasomatic replacement of carbonate rocks by solutions. If rich in Fe, these solutions led to the precipitation of Fe ores containing hematite and magnetite as the main Fe oxides. 

HALLEFI.INTA. A Swedish term for hard, dense, mciamorphic rocks composed chielly of microscopic crystals of quartz and feldspar with occasional phenocry.sls. Accessory minerals may he hornblende, chlorite, hematite nr magnetite. The Icxlurc and composition of hAllcfiinta suggests ihai ii is die metamorphosed equivalent of acid lava Hows or luffs. 

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 ... 

TABLE 10.2. Analysis of a Pure Swedish Magnetite (Malmberget A). 

Natural magnetites with low impurity levels are now used to produce ammonia synthesis catalysts. A typical catalyst analysis is shown in Table 10.4. The significance of promoters in the catalyst was only understood by Mittasch when he tested catalysts made from a Swedish magnetite. Later on, other companies... 

---