Liquid adsorption of linear and branched paraffins onto microporous adsorbents: Influence of adsorbent structure and Si/Al molar ratio

Liquid phase adsorption (298 K, batch technique) of linear and branched paraffins (tetradecane, 3-methylpentane, 2,3-dimethylpentane and 2,2,4-trimethylpentane) has been studied onto several microporous adsorbents with different structures and Si/Al molar ratios: H-Beta (BEA), H-ZSM-5 and S-1 (MFI) and SAPO-11 (AEL). MFI samples showed no adsorption of the geminal paraffin due to molecular sieve effect, as well as a preferential adsorption of the linear paraffin. A competitive adsorption between the mono- and dibranched paraffins was observed onto MFI samples, showing an increase in adsorption capacity for 3-methylpentane at higher Si/Al molar ratios. AEL and BEA samples adsorbed significant amounts of all adsorptives.A mixture of C13 isomers containing different amounts of tridecane, monomethyldodecanes, dimethylundecanes, trimethyldecanes, ethylundecanes and other polimethyl paraffins was also tested onto commercial H-ZSM-5, pure (Si/Al = 13, 16, 54) and agglomerated (Si/Al = 24, 45, 200), as well as onto two commercial pure silicalites. Only dimethyl, monomethyl and linear paraffins were significantly adsorbed. Adsorption capacities of the five monomethyl isomers increased following the sequence 6M–C12 > 5M–C12 > 4M–C13 > 3M–C12 > 2M–C12, specially at low Si/Al molar ratios.