Carbon monoxide conversion process and reactor

A process for isothermal shift conversion of a carbon monoxide containing feed gas comprising the steps of:

• introducing the feed gas in a reaction unit into reactor tubes with a fixed bed of a shift conversion catalyst in a reaction zone;
• contacting the feed gas with the catalyst at conditions being effective in carbon monoxide shift conversion reaction with steam reactant to hydrogen and cooling the reaction by indirect heat exchange with a cooling agent by circumferentially distributing the cooling agent by providing grooves in at least an upper portion of a reactor tube wall and by providing the cooling agent through perforations in a sleeve surrounding each reactor tube to form a falling film along shell-side of the reactor tubes and removing heated cooling agent from the falling film;
• passing hydrogen when it is formed by the shift conversion reaction through a hydrogen selective membrane to a permeate zone;
• and
• withdrawing hydrogen from the permeate zone and carbon monoxide depleted feed gas from the reaction zone.