Isoprene Synthesis From Isobutylene and Methylal (Sun Oil Process)

In this process, methylal (dimethoxymethane) is used instead of formaldehyde. The advantage of using methylal over formaldehyde is its lower reactivity toward 1-butene than formaldehyde, thus allowing mixed feedstocks to be used. Also, unlike formaldehyde, methylal does not decompose to CO and H₂.

The first step in this process is to produce methylal by the reaction of methanol and formaldehyde using an acid catalyst.

The second step is the vapor phase reaction of methylal with isobutene to produce isoprene. 2-Butene in the C₄ mixture also reacts with methylal but at a slower rate to give isoprene. 1-Butene reacts slowly to give 1,3-pentadiene.