A low temperature refrigeration process wherein a feed gas mixture comprising hydrogen or helium as major component and a minor component with normal boiling point above 170.degree. K and molecular weight of at least 28 is dynamically compressed at higher temperature and cooled to intermediate temperature for condensation and separation of the minor component. Pure major component is further cooled and work expanded at lower temperature and recycled for mixing with the condensed minor component during rewarming to form at least the major fraction of the feed gas mixture.