How to Obtain Pure Methanol

Abstract

As described already in Sect. 3.3.1 above, raw methanol contains not only water stemming essentially from the reaction of CO₂ with H₂ and, to a lesser extent, from the formation of dimethyl ether and higher alcohols according to the reactions

$$ 2C{H_3}OH \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} C{H_3}OC{H_3} + {H_2}O $$

$$ C{H_3}OH + nCO + 2n{H_2} \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} C{H_3}{(C{H_2})_n}OH + {H_2}O $$

but also a number of substances whose boiling points are in some instances lower and in some higher than that of methanol. They are usually termed low boilers and high boilers or light ends and tails and include mainly — dissolved gases from the synthesis loop

• dimethyl ether

• methyl formiate

• acetone (in very small quantities)

• C₅ to C₁₀ hydrocarbons (traces also up to C₃₀)

• ethanol

• higher alcohols up to C₅ (and traces of C₅ ⁺).