Polymeric Gas-Separation Membranes for Petroleum Refining

Table 16

Summary of gas separation processes in the refinery and advantages of using membranes.

Process	Separation	Applications	Current technologies	Advantages of membranes	Membrane materials
Hydrogen sulfide separation	CH4/H2S	NG sweetening	Amine scrubbing; PEG absorption; K2CO3 absorption; Methanol absorption; PSA	(i) Does not need a solvent.; (ii) Can treat feeds with wider range of H2S.; (iii) Low NG processing cost for feeds with <1 mol% H2S.	Cellulose acetate (UOP); Polyether-block-amide; Polyamide; Polyether-urethane-urea
Carbon dioxide capture	CO2/CH4; CO2/N2	NG sweetening; Treatment of off-gases	Amine scrubbing; Water absorption; PEG absorption; K2CO3 absorption; Methanol absorption; PSA; Cryogenic distillation	(i) Can separate CO2 with other impurities such as H2S and H2O.; (ii) Can be operated continuously for more than 5 years.; (iii) Low NG processing cost for feed with <10 mol% CO2.	Cellulose triacetate (Cynara); Cellulose acetate (UOP); Polyimide (UBE); Polyether-block-amide; Polysulfone; Polyamide; Polyether-urethane-urea
Hydrogen recovery	H2/CH4; H2/CO; H2/N2	H2 recovery from NG; Syngas adjustment; Ammonia purge gas	Cryogenic distillation; PSA	(i) Ability to treat feeds with wider range of H2.; (ii) Better turndown.; (iii) Higher reliability.	Cellulose acetate (Separex); Polysulfone (PRISM); Polyimide (UBE); Polyetherimide
Air separation	O2/N2	Oxygen enrichment	Cryogenic distillation; PSA	(i) Can be operated at ambient temperature.; (ii) Does not need regeneration.; (iii) Low capital and operating costs.	Cellulose acetate; Polysulfone (UOP); Poly(4-methyl-1-pentene) (GENERON); Polydimethylsiloxane (PRISM); Polyimide; Polyamide; Polyetherimide
Water removal	H2O/CH4	NG dehydration	TEG absorption; Silica bed; Activated alumina; Zeolite molecular sieve	(i) Can be run for more than 7 years without interruption.; (ii) Ability to remove H2S, CO2, and C3+ compounds.	Polydimethylsiloxane (PRISM); Cellulose acetate; Polysulfone; Polyether-block-amide; Polyimide
VOC recovery	VOC/air; VOC/N2	Treatment of off-gases; Recovery of solvents	Thermal oxidation; Catalytic oxidation; Activated carbon	(i) Works at ambient temperature.; (ii) Better chemical stability.	Polydimethylsiloxane (GKSS); Polyimide (Upjohn)
LPG	(C3-C4)/CH4	Recovery of LPG from NG	Cryogenic distillation and gas expansion	(i) Process integration to reduce energy requirement.	Polydimethylsiloxane; Poly[1-(trimethylsilyl)-1-propyne]

NG: natural gas.