Concentrated sulfuric acid has strong water absorption, and is often used to dry neutral gases and acidic gases in the laboratory, but it cannot dry basic gases (NH3) and reducing gases (such as H2S) at room temperature. Now some people think that ethylene can be dried with concentrated sulfuric acid. Is this correct?

The reason for this statement may be based on the principle of ethylene production.

The author thinks that drying ethylene is to remove water from ethylene, and the principle of impurity removal is: no addition or reduction, that is, no new impurities are added or the purified substances are reduced. So is it consistent with this principle to dry ethylene with concentrated sulfuric acid? The temperature of concentrated sulfuric acid for preparing ethylene is 170℃, and the concentrated acid for drying ethylene is room temperature. It can be said that concentrated sulfuric acid is hot when preparing ethylene, and hot concentrated sulfuric acid does not react with ethylene (does not absorb ethylene), but it cannot be considered that concentrated sulfuric acid (relatively cold) does not absorb ethylene at room temperature.

Many university organic chemistry textbooks think that cold concentrated sulfuric acid can react with ethylene to generate new substances:

CH2=CH2+H2SO4 (concentrated) → CH3 H2O SO3H

It can be seen from the above analysis that concentrated sulfuric acid can not be used to dry ethylene, but can be used to remove olefins from the mixture (just connect several washing tanks filled with concentrated sulfuric acid).

Therefore, I don't think concentrated sulfuric acid can be used to dry ethylene. For high school students, alkaline lime is better.