Successively separating C3H6 and C2H4 from C2H4/C2H6/C3H6/C3H8 mixture in tandem fixed beds involving two zeolites LTA well-regulated via low transition-metal doping

[Display omitted] •Zeolites Ag/Cd-4A and Ni-5A were well-regulated via low transition-metal doping.•Separation of C3H6 and C2H4 from C2H4/C2H6/C3H6/C3H8 mixture is achieved.•Deformation of C2H4 and C3H6 occurs during passing through the 8MR of Ag/Cd-4A.•Ag/Cd-4A and Ni-5A adsorption beds can be well desorbed via using CO2 purging. There is great interest in adsorptive separation of light olefins from alkanes with the same carbon number. However, previous investigations mainly focused on binary olefin/alkane mixtures or always produced mixed olefin from multiple components. Adsorptive separation of single-component olefins from mixtures containing multiple olefins is of practical importance but still a big challenge in industry. Present work provides an approach to the successive separation of C3H6 and C2H4 from a mixture of C2H4/C2H6/C3H6/C3H8 using tandem twin fixed beds filled with two well-regulated zeolites LTA. The adsorbents of Ni-5A and Ag/Cd-4A were post-synthesized via low transition-metal doping into zeolites LTA and employed to separate the C3H6 and C2H4 from the quaternary mixture. The Ni-5A attains a C3H6 uptake of 2.25 mmol/g and a C3H6/C2H4 Henry selectivity of 10.4, while the Ag/Cd-4A exhibits a C2H4 adsorption capacity of 3 mmol/g and a C2H4/C2H6 Henry selectivity of 1015.5. Furthermore, the molecule sieving of C2H4 is mainly determined by the micropore size of adsorbent, and the selective adsorption of C3H6 over C2H4 is largely attributed to the strong guest – host interactions with the metal sites. In addition, both the Ag/Cd-4A and Ni-5A adsorption beds can be well desorbed via CO2 purging. The DFT calculations reveal the molecular deformation of C2H4 and C3H6 during passing through the 8MR of Ag/Cd-4A and the competitive adsorption affinity of Ni-5A towards C3H6. The present process of tandem fixed beds coupled with well-regulated zeolite adsorbents provide an efficient strategy for the adsorptive separation of the mixtures of olefins and alkanes.