A study on the selection of the effective cycle base on 4 – step and 6 – step pressure swing adsorption processes for nitrogen gas production. Vietnam j. catal. adsorp. [Internet]. 2019 Sep. 30 [cited 2025 Jul. 4];8(3):25-31. Available from: https://jca.edu.vn/index.php/jca/article/view/550