THE SYNOL PROCESS
1. General Introduction.
The synol process has been developed by I.G. Farben at Leuna under the direction of Dr. Herold. It is a new process for the production of oxygenated compounds, mainly alcohols. The hydrogenation of CO to form alcohols at high pressure is an established process (methanol synthesis and isobutanol synthesis). The synol process is one attempt to continue this series and produce higher boiling alcohols with the OH group in the terminal position, thereby alcohols of the isobutyl synthesis. differing from the a alkyl-alcohol of the oxo-synthesis and the branched chain alcohols of the isobutyl synthesis.
The overall equation of the synthesis may be written as
follows:
28 CO+23 H2→ CH3 (CH2)8 - OH +
C8 H16+ 11 CO2 + 5 H2O
This result, the direction of the synthesis towards the production of alcohols, was obtained by operating at intermediate pressures over iron catalysts, and at the lowest possible temperatures, 180°-200° C. This in turn is made possible by a special reduction of the catalyst.
The development of the process was carried out mostly during the war. A series of patents, covering the essential features, were applied for in Germany only. Towards the end of the war it was decided to build a 300,000 ton/year plant at Leuna, but the project was still in the paper stage when the war ended.
The basic patent (see reference II/2, II/3 and II/4 at end of this section) applied for in September 1942 makes the following claim:
A process for the production of alcohols from CO and H2 over Fe catalyst at elevated pressure, characterized by the operation at temperatures substantially lower than those required for the production of hydrocarbons over the same catalyst.
The patent further discloses the use of excess hydrogen in the preparation of the catalyst and the importance of keeping any trace of oxygen from the catalyst during and after reduction.
In another patent application, dated March 1943, the use of gas recycle, with intermediate removal of the product, is disclosed as a means to increase the percentage of alcohols in the product to 70% and more. This is the same principle as the “Kreislauf” process for the increase of olefins.