Methanol Directly Synthesized from CO and

CO in the synthesis gas mixture for the methanol synthesis does not seem to take part directly in the reaction, but it does influence the process through two effects First the water-gas shift reaction and, secondly, through its effect on the surface morphology (and possibly also composition). For thermodynamic reasons, however, it would be desirable if CO could be hydrogenated directly via Eq (18) instead of going through two coupled equations (3) and (19), since it would yield a higher equilibrium concentration of methanol at the reactor exit. 

consider the direct formation of methanol from CO and H2, If x is the mole fraction of H2 and t is the mole fraction of methanol (Tab. 8.3 gives the other mole 

Po is the standard pressure and px is the partial pressure of component X. Rearrangement of Eq. (56) leads to a third-order equation in t, which can be solved iteratively. Notice that the pressures used in Eq. (55) should actually be replaced by activities, implying that they should be corrected by their respective fugacity coefficients, which are of importance when dealing with methanol and water. We leave it as an exercise for the reader to judge the influence of such effects, utUizing the relation between pressure and activity given in Eq. (39) of Chapter 2. 

When methanol is produced from a mixture of CO2, CO and H2, the reverse water-gas shift reaction complicates the system, since it competes with the methanol synthesis. 

We use the same procedure as shown above where x again denotes the mole fraction of H2, Y is the mole fraction of CO, and t is the mole fraction of methanol and of water produced in this reaction. The total mole fraction after reaction is again (1 -2t) and the normalized mole fractions after reaction are given in Tab. 8.4. 

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