Patent GB-682954-A (GB)
Title: Improvements in or relating to the production of alcohols
IPC: C07C29/152
Filed: 1949-05-11
Abstract: Alcohols, especially methanol, are made from CO and H2 the process being effected in apparatus which is not resistant to CO and which is made of iron or lowly alloyed steel at a partial pressure of CO which is so low in all the colder parts of the apparatus which are at temperatures of up to 250 DEG  C. and which are exposed to attack by CO that in practice only a negligible quantity of iron carbonyl is formed, for example at a partial pressure of CO of up to 20 atmos. in the case of a total pressure of 300 atmos., while a higher partial pressure of CO, e.g. 30 atmos., is used in hotter parts of the apparatus.  Diagrams are provided which show the effect of temperature and partial pressure of CO on the production of iron carbonyl.  It is stated that at temperatures of up to 250 DEG  C. and pressures of 300-600 atmos. damaging of apparatus is prevented if partial pressures of CO of 15-20 atmos. are used but that if products whose iron content is as low as those obtained from CO resistant apparatus are to be obtained then still lower partial pressures than these should be used.  Synthesis gas, which is rich in CO, or a major portion thereof is added at a hot part of the circuit, e.g. immediately before and/or straight into the catalyst chamber.  In a preferred embodiment the catalyst is divided into layers and the synthesis gas is delivered to the second and further layers of the catalyst and temperature control of the catalyst zone may be achieved by adding fresh synthesis gas to the first contact layers and cold circuit gas or cold mixtures of these two gases to succeeding layers. Thorough mixing of freshly supplied and circuit gases should be effected.  Catalyst soiling is minimized by arranging that the highest temperature of the chamber is in a layer which is in front of the first position of supply of fresh gas which may have accumulated iron carbonyl in the preheating chamber and consequently it is only this layer which is soiled by iron because of carbonyl decomposition. Fresh gas is advantageously purified, e.g. with activated charcoal, from carbonyl formed in the compressor, and inlet pipes for fresh and cold circuit gases together with mixing devices may be made of CO resisting metals. Apparatus normally used for the high pressure synthesis of benzine or ammonia may be used.  In an example 50,000 cubic metres per hour of preheated circuit gas containing 5 per cent of CO is supplied to the first layer of the catalyst chamber at 325 DEG  C. and leaves at 370 DEG  C. when it is mixed with 9500 cubic metres per hour of fresh gas containing 30 per cent CO before passing to the second layer which it leaves at 350 DEG  C., a temperature which is maintained at succeeding layers by the addition of 10,000 cubic metres per hour of cold circuit gas containing 5 per cent CO or by means of a change in the point of addition of fresh gas and methanol is separated from the cooled products.  There are six layers of catalyst the latter being 75 per cent zinc oxide and 25 per cent chromium oxide.  Part of the recycle gas is vented to prevent an excessive build-up of methane.