provided an unusually high yield—a yield unmatched by an exhaustive study of
other magnetites. Using his array of newly designed Haber-Le Rossignol
reactors, Mittasch began a systematic study to determine which additions to the
basic iron catalyst were most effective. Sodium and potassium hydroxides were
the earliest tested additions, and this led to the first BASF patent regarding
‘mixed catalysts’ (DRP 249 447), filed on 09 January 1910 by Bosch, Mittasch,
Stern and Wolf.
2 Eventually, Mittasch concluded that the presence of other
elements acted as ‘promoters’ of the ammonia reaction and he soon developed a
mixed catalyst of magnetite and bauxite, together with oxides of potassium,
calcium and magnesium which according to Bosch was ‘relatively fast acting,
technically perfect, easily manipulable, stable and inexpensive.’
1 At the time,
these catalysts were of a completely new type but even today the composition of
the mixed catalysts in an ammonia plant remains virtually the same as Mittasch
and his co-workers originally discovered. By January 1910 the search for a
catalyst was effectively over and the BASF wrote to Haber with their findings
(Chap. 10).
11.2 Nitrogen and Hydrogen
The supply of raw materials however proved more difficult. By 1909,
nitrogen of sufficient purity to prevent catalytic ‘poisoning’ was available from
the Linde process, but the procurement of hydrogen of an equivalent purity
represented a prime cost, especially so since the efficiency of the high-pressure
conversion of the gas mixture into ammonia was such that its cost was a
minor factor. None of the known hydrogen producing processes at the time
(Chap. 8) were suitable, and given the BASF’s access to vast quantities of coal,
Bosch decided
1 that the source of hydrogen had to be ‘water gas’, a mixture of
hydrogen and carbon monoxide obtained by passing steam over red hot coke
according to;
CðsÞ þ H 2 OðgÞ COðgÞ þ H 2 ðgÞ þ 118:7 kJ mole
À1
This gas mixture contained about 50% hydrogen, 40% carbon monoxide,
and 5% each of nitrogen and carbon dioxide. A cryogenic process was initially
used to remove the carbon monoxide at –200 °C and *25 atm, but as the
yields from the ammonia synthesis increased Bosch looked for a better
solution. By summer 1911, Wilhelm Wild, one of Nernst’s pupils working
for the BASF, had perfected a cheaper method of hydrogen production from
214
D. Sheppard
other magnetites. Using his array of newly designed Haber-Le Rossignol
reactors, Mittasch began a systematic study to determine which additions to the
basic iron catalyst were most effective. Sodium and potassium hydroxides were
the earliest tested additions, and this led to the first BASF patent regarding
‘mixed catalysts’ (DRP 249 447), filed on 09 January 1910 by Bosch, Mittasch,
Stern and Wolf.
2 Eventually, Mittasch concluded that the presence of other
elements acted as ‘promoters’ of the ammonia reaction and he soon developed a
mixed catalyst of magnetite and bauxite, together with oxides of potassium,
calcium and magnesium which according to Bosch was ‘relatively fast acting,
technically perfect, easily manipulable, stable and inexpensive.’
1 At the time,
these catalysts were of a completely new type but even today the composition of
the mixed catalysts in an ammonia plant remains virtually the same as Mittasch
and his co-workers originally discovered. By January 1910 the search for a
catalyst was effectively over and the BASF wrote to Haber with their findings
(Chap. 10).
11.2 Nitrogen and Hydrogen
The supply of raw materials however proved more difficult. By 1909,
nitrogen of sufficient purity to prevent catalytic ‘poisoning’ was available from
the Linde process, but the procurement of hydrogen of an equivalent purity
represented a prime cost, especially so since the efficiency of the high-pressure
conversion of the gas mixture into ammonia was such that its cost was a
minor factor. None of the known hydrogen producing processes at the time
(Chap. 8) were suitable, and given the BASF’s access to vast quantities of coal,
Bosch decided
1 that the source of hydrogen had to be ‘water gas’, a mixture of
hydrogen and carbon monoxide obtained by passing steam over red hot coke
according to;
CðsÞ þ H 2 OðgÞ COðgÞ þ H 2 ðgÞ þ 118:7 kJ mole
À1
This gas mixture contained about 50% hydrogen, 40% carbon monoxide,
and 5% each of nitrogen and carbon dioxide. A cryogenic process was initially
used to remove the carbon monoxide at –200 °C and *25 atm, but as the
yields from the ammonia synthesis increased Bosch looked for a better
solution. By summer 1911, Wilhelm Wild, one of Nernst’s pupils working
for the BASF, had perfected a cheaper method of hydrogen production from
214
D. Sheppard