Preparation of amino functionalized titanium oxide nanotubes and their incorporation within Pebax/PEG blended matrix for CO2/CH4 separation

[Display omitted] •TiNT-TEPA was synthesized as filler particles for blended Pebax/PEG600 nanocomposite membrane based on DOE and RSM methods.•Adsorption capacity of as-synthesized and functionalized nanotubes investigated.•Nanocomposite membranes’ CO2 permeability and CO2/CH4 selectivity considerably increased compared with neat membrane.•Effect of operating temperature and transmembrane pressure were studied for single and mixed gases. Raw and tetraethylene pentamine (TEPA) functionalized titanium oxide nanotubes (TiNTs) were used as filler particles to prepare nanocomposite membranes. Polyethylene glycol (PEG) was blended with the Pebax-1657 as matrix and incorporated by TiNT-TEPA to prepare Pebax-1657/PEG/TiNT-TEPA nanocomposite membranes based on Response Surface and Central Composite Design methods of experimental design. The TiNT-TEPA and the Pebax/PEG/TiNT-TEPA were characterized using TEM, FESEM, SEM, FTIR or ATR-FTIR, XRD (EDS) and mechanical strength analysis. CO2 adsorption capacity of TiNTs and TiNT-TEPA-70% were found as 0.71 and 4.2mmol/g, respectively. CO2 permeability and ideal selectivity of optimum (in term of separation performance) membrane, as Pebax (7wt.%) /PEG (7.5wt.%)/TiNT-TEPA (3wt.%), were increased by 67.7 and 11.7%, respectively, compared with the neat Pebax membrane. The optimum membrane’s CO2 permeability and CO2/CH4 ideal selectivity were investigated at operating temperatures of 20–45°C and reveled 18.5 and −9% changes, respectively. Its transmembrane pressures increment form 4 to 10bar for single and CO2 (50)/CH4 (50) mixed gas resulted in CO2 permeability and CO2/CH4 ideal selectivity enhancements by 19 and 20%, respectively. The optimum membranes’ mixed gas separation performance were found lower than that of single pure gases at the same operating condition.