to 80 of the sodium ions is exchanged with barium ions can be manufactured by preparing a zeolitic molecular sieve agglomerate including na x zeolite and the above mentioned binder followed by partially exchanging the sodium ions of the resultant na x zeolite agglomerate with barium ions the na x zeolitic molecular sieve agglomerate can be prepared in any conventional manner e g by mixing the na x zeolite with the binder followed by drying and calcining the formed mixture at elevated temperatures e g 150 u00b0 c to 300 u00b0 c and 550 u00b0 c to 700 u00b0 c respectively the resultant na x zeolitic molecular sieve agglomerate can be treated with the above mentioned solution containing barium ions the resultant barium exchanged molecular sieve agglomerate is then dried and activated at a temperature of for example 200 u00b0 c to 550 u00b0 c the molecular sieve agglomerates including as a main constituent the barium exchanged crystalline zeolite having the above mentioned general formula i have excellent thermal stability and thermal deterioration resistance and can be effectively used in the separation and purification of gas mixtures especially the present molecular sieve agglomerates can be advantageously used in the separation of carbon monoxide and nitrogen in the separation of nitrogen and oxygen or in the removal of water vapor and carbon dioxide from air containing the same the present invention now will be further illustrated by but is by no.