K-RHO zeolite with high nitrogen selectivity for N2/CH4 separation by PSA process

Zeolite RHO, a microporous zeolite, has the great possibility for N 2 /CH 4 separation by regulating the size of the eight-membered ring window on the RHO framework. In this work, the ability of ion-exchanged RHO zeolites for N 2 /CH 4 separation is investigated, and a highly nitrogen selectivity adsorbents are developed. RHO samples were prepared by hydrothermal synthesis. Alkali metal cations (Na + , K + , Cs + ) was used for ion exchange. Adsorption equilibrium isotherms of N 2 and CH 4 were measured at normal temperature and fitted by the Langmuir equation. The adsorbent selection parameters ( S parameters) were calculated based on the working capacity and equilibrium selectivity of N 2 /CH 4 , which are used to comprehensively evaluate the selectivity of N 2 /CH 4 . The results indicate that the cations have effects on the regulation of the eight-membered ring window. In particularly, K-RHO no.2 sample which is obtained by ion exchange of K + cations exhibit the best N 2 /CH 4 separation performance, which is a potential nitrogen selective adsorbent. In addition, the product throughputs of RHO and the commercial adsorbent ETS-4 were compared by common PSA simulation process with essentially the same product purity and recovery. The results show that K-RHO no.2 has 36 % higher product throughput than ETS-4, which can compensate for the problem of low N 2 working capacity of ETS-4 in industrial application.