Abstract: Ethers suitable for use as high octane oxygenate additives for motor fuels are produced by a catalytic distillation process wherein a mixture of C.sub.4 -plus isoolefin(s) and an alcohol are recovered from a catalytic distillation zone as an overhead stream and charged to a packed liquid-phase reaction zone containing an etherification catalyst before being recycled to one or more portions of the overall catalytic distillation zone. The process is useful in the coprocessing of a mixture of isobutylene and isoamylene and in other hydrocarbon conversion processes such as hydration and alkylation.