Process for producing an olefin by decomposition of the corresponding ether

A process for producing a tertiary olefin of the formula:

• ##STR11## by decomposition of the corresponding tertiary ether of the formula:
• ##STR12## wherein R.sub.1 and R.sub.3 are each independently an alkyl, arylalkyl, aryl or alkylaryl radical;
• and R.sub.2 and R are each independently a hydrogen atom or an alkyl, arylalkyl, aryl or alkylaryl radical, said process comprising the step of contacting said ether, in the presence of steam, the molar ratio H.sub.2 O/tertiary ether being from 2 to 8, with a catalyst consisting essentially of alumina having deposited thereon at least one modifying agent, said agent being titanium, zirconium or hafnium, as the elemental metal or a metal compound, the content of said metal or metal compound, expressed as the elemental metal, being 0.01-5% by weight with respect to the alumina, said alumina, after incorporation of the metal or metal compound, having a specific surface of 80-300 m.sup.2 /g;
• whereby the tertiary olefin is produced in high purity, and parasitic side-reactions which decrease the yields of tertiary olefin and of recovered alcohol are minimized.