Novel C-PDA adsorbents with high uptake and preferential adsorption of ethane over ethylene

In this work, a novel porous carbon-based material C-PDA(Carbonized Polydopamine Adsorbent) was prepared using one-step synthesis method for adsorption separation of C2H6/C2H4, and then characterized by N-2 adsorption at 77 K, FFIR, XPS and TG. The BET surface area and pore volume of C-PDAs can reach as high as 3291 m(2)/g and 1.97 m(3)/g, respectively. FTIR spectra suggested the presence of N/O functionalities in C-PDAs, and its contents decreased with the KOH/C ratio at which the samples were prepared. Adsorption capacity of C-PDAs for C2H6/C2H4 increased with the surface N and O contents of C-PDAs. More interestingly, it showed significantly preferential adsorption of C2H6 over C2H4. Its C2H6 adsorption capacity was up to 7.93 mmol/g at 100 kPa, and its C2H6/C2H4 adsorption selectivity was in the range of 1.9-7.94 at pressure below 100 kPa when the ratio of C2H6:C2H4 was 0.1:0.9 at 298 K, higher than most reported adsorbents possessing preferential adsorption of C2H6 over C2H4. The preferential adsorption mechanism of C2H6 over C2H4 on C-PDAs were revealed by DFT (Density functional theory) calculation. The isosteric heat of C2H6 and C2H4 adsorption on C-PDAs were much lower than the preferential adsorption affinity of olefin over pi-complexation sorbents. These excellent adsorption properties of C-PDAs make it a type of promising adsorbent for the effective separation of ethane/ethylene. (C) 2016 Elsevier Ltd. All rights reserved.