106.    ---------------. [AUDIBERT, E] [Synthetic of Methanol.]  Ann. combust. liquides, vol. 6, 1931, pp. 655-709; Brennstoff-Chem., vol. 13, 1932, pp. 92-93; Chem. Abs., vol. 26, 1932, p. 1235.

                 Commercial synthesis of MeOH, particularly with regard to the heat of reaction, the use of pressure and low temperatures and the influence of the catalyst, and the H₂:CO ratio and the temperature upon the speed of the reaction, is discussed.  The economy of the proceeds depends upon the extent of the side reactions.  Beside increasing the consumption of synthesis gas they add to the difficulties of converter regulation since they give rise to excessive temperature increases.  They are of 2 types:  A primary, in which only the H₂ and the CO take part, and a secondary, in which the reaction products undergo further conversion.  The primary reaction is exemplified in formation of CH₄ (2CO+2H₂=CO₂+CH₄+61kcal.).  The quotient of y/x (y is that portion converted into CO₂ and CH₄, x that converted into MeOH) is independent of the space velocity but depends on the chemical composition of the catalyst and the operating temperature.  A rise in temperature of about 100° increases the extent of this side reaction with a Cu-Th catalyst about 60-fold and with a Zn-Cr catalyst about fourfold.  Certain measures to be taken against the occurrence of these side reactions are offered.  Formation of high-molecular substances can be curtailed by avoiding the presence of alkali and by correctly choosing the H₂:CO ratio.  The MeOH must be removed before its concentration becomes too great.  Ch₄ formation and overheating must be opposed by the efficient removal of heat through a cooling system or by addition of inert constituents to the reaction gas.  Catalysts prepared the wet way are very susceptible to overheating.  The injury produced thereby depends upon the chemical composition.  The best catalysts are Cu and Zn oxides.  As promoter for ZnO, Cr₂O₃ is suitable and for Cu a large number of additives are available.  The activity with Cu-containing catalysts at 300° and 100 atm. is about 8-fold greater than with Cu-free catalysts and with at least equal resistivity toward overheating.  With Cu-free catalysts the temperature must be at least 400° and the pressure 400 atm. to attain the same space-time yield.  The Cu-containing catalysts require a thorough purification of the raw gas from S compounds, particularly COS.  Even with this, the advantage is with them since the cost of gas purification per kg. of MeOH and down 1.25 Mg. S per m.³ is only 10-12 centimes.  Extreme care is necessary in preparing the catalysts.  The precipitation factors, such as concentration of the solutions, excess of alkali, precipitation temperature, etc., greatly influence the activity.  The volume shrinkage during the operation, amounting after 600 hr. to 60%, could be reduced to 20% by means of previous compression.