Effect of Organic Solvents on Separation of Heat Stable Salts (HSSs)
Generated During Carbon Dioxide Absorption Using Amine Solution
Panupat Suppaibulsuka, Chintana Saiwana1,
Teeradet Supapb
aPetroleum
and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand
bInternational
Test Centre for CO2 Capture, University of Regina, SK, Canada S4S 0A2
Various solvents, i.e. 2-ethyl-1-hexanol, 1-octanol, 1-heptanol, 1-hexanol, and 1pentanol, were used as organic diluents in the liquid-liquid extraction of heat stable salts
(HSSs) in monoethanolamine (MEA) absorption solution of carbon dioxide. Each HSSs
consisted of 1,000 ppm of formate, acetate, oxalate, and glycolate in an aqueous solution with
and without MEA. An equal volume of 1 M of extractant solution and HSSs solution was
mixed for complete phase separation to reach equilibrium. After extraction, the aqueous
phase was separated and analyzed by high performance liquid chromatography with an ultra
violet detector to measure the HSSs concentration left in the aqueous solution. The results
revealed that the extractant in 2-ethyl-1-hexanol gave the most effective extraction of all
HSSs with 99.47 wt% of formate, 95.46 wt% of acetate, 99.87 wt% of oxalate, and 93.86
wt% of glycolate. For the same carbon chain length, 2-ethyl-1-hexanol had better extraction
efficiency than 1-octanol. The extractant in the longer chain alcohols performed noticeably
better than in the shorter chain alcohols, i.e. 2-ethyl-1-hexanol, 1-octanol, and 1-heptanol
yielded better extraction than 1-hexanol and 1-pentanol. The extractant in the extractant-HSSs
complex in diluents regenerated for repeated use by a caustic regenerant. The concentrations
of recovered HSSs in the regenerant were also measured by high performance liquid
chromatography method.
Keywords: Heat Stable Salts, CO2 Absorption, Organic Solvents, Alcohol, Extraction
* Corresponding author. Tel.: +662-218-4137; fax: +662-215-4459.
E-mail address: Chintana.sa@chula.ac.th.