Why do we use calcium oxide $\ce{CaO}$ in soda lime decarboxylation?

$$\ce{\underset{sodium acetate}{CH3COONa} + \underset{sodium hydroxide}{NaOH} ->[\Delta][CaO] \underset{methane}{CH4} + \underset{sodium carbonate}{Na2CO3}}$$

It seems as if it is dehydrating agent to keep NaOH dry), but why is the dehydrating agent required if the heat would be enough to dehydrate the container as the temperature is very high (expected to be over 100 °C)?

  • 2
    $\begingroup$ If you dehydrate with P205 you get the anhydride. Sodalime first forms the sodium salt. Sodalime is used in preference to sodium hydroxide for ease of handling chemguide.co.uk/organicprops/acids/decarbox.html $\endgroup$
    – Waylander
    Dec 21 '20 at 13:52
  • $\begingroup$ @Waylander I am working with sodium salt already $\endgroup$
    – user99515
    Dec 21 '20 at 14:20
  • $\begingroup$ @Poutnik it feels no difference the reaction i provided is just one step ahead $\endgroup$
    – user99515
    Dec 21 '20 at 14:25
  • $\begingroup$ @Poutnik sorry i didn't catch that $\endgroup$
    – user99515
    Dec 21 '20 at 14:39
  • $\begingroup$ Calcium oxide is the typical catalyst used for this reaction. Caesium salts also catalyze this reaction. wikipedia - sodium acetate $\endgroup$
    – Poutnik
    Dec 21 '20 at 14:40

Calcium oxide is not necessary for carrying out this reaction. It only prevents NaOH from touching the glass of the container where the reaction is done. If a solid mixture of sodium acetate and NaOH is heated to high temperature, some NaOH will attack the glass before reacting with acetate, and make the glass melt down. If NaOH is intimately mixed with CaO, this trouble is avoided. The glassware is saved.


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