Equilibrium in the System Methyl Alcohol-Hydrogen-Carbonic Oxide
Proceedings of the Royal Society A
About two years ago there was installed in the High Pressure Gas Research Laboratories at the Imperial College, apparatus which had been specially designed by Prof. Bone and his staff for the investigation of reaction velocities and equilibrium conditions in reversible catalytic systems ; and at his request we undertook to determine by means of it the equilibrium conditions of the system methyl alcohol-hydrogen-carbonic oxide at those temperatures at which the commercial production of pure
... uction of pure methyl alcohol from water gas is practicable. The present paper embodies our results up to date for the temperature range 280° to 340° C. and for pressures of about 100 atmospheres. Although the synthesis of methyl alcohol by the direct union of carbonic oxide and hydrogen has already reached a stage of development when large scale operations are being undertaken, no systematic work appears to have been carried out to determine the maximum possible yields under given temperature and pressure conditions. The value of a knowledge of equilibrium conditions in the system has not been overlooked, however, for a number of attem pts have been made to calculate them from existing physical data. It may be pointed out that, whilst in the initial stages of a research the results so obtained are of undoubted value for predicting the most favourable working limits of temperature and pressure, they are not sufficiently reliable to afford guidance at a later stage, and may even be misleading. In fact our experi mental results would rather indicate that a good deal of unnecessary work may have been done in striving after yields that are unattainable. The want of concordance amongst calculated results may be illustrated by a comparison of the values of the equilibrium constant at various temperatures as deduced by two alternative methods. Thus, for example, from existing free energy data and a knowledge of the heats of combustion of carbonic oxide and methyl alcohol, K. K. Kelley obtained the following equation to express the relationship between free energy change and temperature for the reaction under consideration:-AF = -21,300 + 32-2 T log T -0-00825 T2 -42-5 T. on July 20, 2018 http://rspa.royalsocietypublishing.org/ Downloaded from From the so ascertained free energy values the equilibrium constant wascalculated from the relation AF = -RT In Kp. Audibert and Ram eau, on the other hand, have used a method based upon Nernst's Heat Theorem from which they derive an equation for calculating the fraction, x, of carbonic oxide converted into methyl alcohol at any temperature and pressure, namely, log t1 3<5 j T + 2-99794 -2 log P. 8 a;(3 -2x)2 4-571 T 8 8 The values of Kp calculated by means of these two equations, at three temperatures, are compared in Table I.