NOVELTY - Molecular hydrogen from a high pressure gaseous mixture containing carbon dioxide and the hydrogen, is separated by exposing a dense vanadium based membrane to the gaseous mixture at 300-440degreesC and a source side pressure of 250-500 psia; maintaining a hydrogen partial pressure gradient across the membrane from a hydrogen source side to a hydrogen permeate side which provides a hydrogen partial pressure on the permeate side of 0.02-2 psia; and removing molecular hydrogen from the permeate side, where a high hydrogen flux rate is maintained through the membrane.    USE - The inventive method is used for separating molecular hydrogen from a high pressure gaseous mixture containing at least carbon dioxide and the hydrogen.    ADVANTAGE - The inventive method exhibits surprisingly high proton flux rates as well as physical stability under elevated pressures, or provides a high dissociated hydrogen flux rate through the membrane without physical failure of the membrane due to the high hydrogen partial pressure differential maintained across it. It allows for the elimination of low-temperature water-gas-shift (WGS) reactors and pressure swing adsorption steps now used in the production and purification of hydrogen.    DETAILED DESCRIPTION - Separation of molecular hydrogen from a high pressure gaseous mixture containing at least carbon dioxide and the hydrogen, includes:    (A) providing a dense vanadium based membrane containing 0 up to 10 atomic% nickel based on the total membrane, and having a hydrogen source side and a hydrogen permeate side;    (B) exposing the membrane to the gaseous mixture at 300-440degreesC and a source side pressure of 250-500 psia;    (C) maintaining a hydrogen partial pressure gradient across the membrane from the source side to the permeate side which provides a hydrogen partial pressure on the permeate side of 0.02-2 psia; and    (D) removing molecular hydrogen from the permeate side, where a high hydrogen flux rate is maintained through the membrane.    The membrane has a palladium coating on at least the source side, and a thickness of 75-500 microns.