This invention is directed to a reactor and process for producing methanol. The reactor includes utilizes a plurality of beds of methanol synthesis catalyst in series to form methanol product from synthesis gas (syngas). A liquid layer continuously flows across the top of each catalyst bed, with one or more conduits (e.g., downcomers) that collect the flowing liquid and flow the collected liquid by gravity down to the next bed of catalyst in series. The downcomers are sealed so that vapor does not pass upwardly through the downcomers.