(FR2731163-A1)      Process for sepn. of a gaseous mixt. contg. an impurity comprises the following steps: (i) the gaseous mixt. is sent through the non-permeable side of a first membrane system (3, 3a); (ii) a fluid with a lower partial pressure at least for the impurity is sent through the permeable side of the first membrane system; (iii) the non-permeate of the first membrane system is recovered, with fewer impurities; (iv) the non-permeate is then sent through a second sepn. system (5, 5a) for final sepn. The separator for a gaseous mixt. as above, contains a first membrane system with means for sending the gaseous mixt. through the non-permeable side and a fluid with a lower partial pressure for at least the impurity through the permeable side; a second sepn. system and means for sending the non-permeate of the first system to the second system.    USE -   Removal of an impurity from a gaseous mixt., in partic., removal of a minor second reaction prod. from a first reaction prod.(claimed).    (EP758263-A1)      Process for sepn. of a gaseous mixt. contg. an impurity comprises the following steps: (i) the gaseous mixt. is sent through the non-permeable side of a first membrane system (3, 3a); (ii) a fluid with a lower partial pressure at least for the impurity is sent through the permeable side of the first membrane system; (iii) the non-permeate of the first membrane system is recovered, with fewer impurities; (iv) the non-permeate is then sent through a second sepn. system (5, 5a) for final sepn. The separator for a gaseous mixt. as above, contains a first membrane system with means for sending the gaseous mixt. through the non-permeable side and a fluid with a lower partial pressure for at least the impurity through the permeable side; a second sepn. system and means for sending the non-permeate of the first system to the second system.    USE -   Removal of an impurity from a gaseous mixt., in partic., removal of a minor second reaction prod. from a first reaction prod.(claimed).    (CN1150762-A)      Process for sepn. of a gaseous mixt. contg. an impurity comprises the following steps: (i) the gaseous mixt. is sent through the non-permeable side of a first membrane system (3, 3a); (ii) a fluid with a lower partial pressure at least for the impurity is sent through the permeable side of the first membrane system; (iii) the non-permeate of the first membrane system is recovered, with fewer impurities; (iv) the non-permeate is then sent through a second sepn. system (5, 5a) for final sepn. The separator for a gaseous mixt. as above, contains a first membrane system with means for sending the gaseous mixt. through the non-permeable side and a fluid with a lower partial pressure for at least the impurity through the permeable side; a second sepn. system and means for sending the non-permeate of the first system to the second system.    USE -   Removal of an impurity from a gaseous mixt., in partic., removal of a minor second reaction prod. from a first reaction prod.(claimed).