A synthesis gas conversion process and system are disclosed. Fresh syngas from a methane reformer is used as a sweep zone gas feed which is caused to flow across a water permselective membrane in a membrane reactor. The water permselective membrane is adjacent a synthesis gas conversion reaction zone in which synthesis gas is contacted with a catalyst and converted to effluent including water. Water is removed from the reaction zone through the membrane and passes out of the reactor with the sweep zone gas. The water is then removed from the sweep zone gas forming a modified gas feed which is fed to the reaction zone. The modified gas feed has a preferred H2/CO ratio to feed into the reaction zone.