Solubility of benzene in copolymer aqueous solutions for the design of gas absorption unit operations

Abstract

In this work, an amphiphilic block copolymer (ABC) aqueous solution is proposed as innovative green liquid for benzene recovery from polluted gas. This ABC has been selected among four commercially available copolymers, two thermosensitive ABC containing poly-ethylene oxide and poly-propylene oxide blocks–Pluronic®L62 and Pluronic®P123 – one non-thermosensitive ABC – poly(vinyl pyrrolidone)-polystyrene (PVP-PS) and one non-ionic surfactant – polyoxyethylene sorbitol monooleate (Tween 80®). For each copolymer aqueous solution, benzene Henry's constant (H) has been experimentally calculated and the effects of temperature (4–90°C) and copolymer concentration (4–20%) have been investigated. Experimental results at 20°C and 4% copolymer concentration showed that the H values are in the range 50–280atm, with a ranking PVP-PS<P123<Tween 80<L62. A consistent increase in benzene solubilisation, with respect to pure water, is observed when micellar structures are formed. Benzene solubility is likely to be dependent on the hydrophobic block of the copolymer molecule and its length, and it can be further increased by increasing copolymer concentration. A considerable increase in benzene H value (>1100atm) has been measured in P123 aqueous solution at 90°C, corresponding to its critical point (i.e. phase separation and no micelles presence). As a result of its benzene H values, the P123 aqueous solution was found to be the most promising liquid for benzene recovery among those investigated, being effective for both operations of gas absorption (at low temperature) and solvent regeneration by thermal stripping (at high temperature).