Ion Chromatography Of Cations Research Articles

Phase separation behavior and thermal degradation analysis of DETA/DEA/DMAC biphasic absorbent

Thermal stability is crucial for maintaining the efficient performance and low regeneration energy of biphasic absorbents, while the synergistic degradation reactions and condition fluctuations could significantly influence the thermal degradation process of biphasic solutions. In this research, a typical amide-based biphasic absorbent diethylenetriamine(DETA)/diethanolamine(DEA)/N, N-dimethylacetamide(DMAC) with low regeneration energy, was applied in a thermal degradation investigation. The thermal stability of active amine in DETA/DEA/DMAC was superior to 30 wt% MEA, 7 M DETA solution, and other biphasic absorbents, with a 19.9 % lower amine degradation ratio compared to 7 M DETA. The primary thermal degradation products in DETA/DEA/DMAC with and without CO2 were analyzed using Cation Ion Chromatography (IC) and 13C Nuclear Magnetic Resonance (NMR). A series of synergistic reactions between DETA and DMAC, with DMAC being an inducer, was revealed in thermal degradation of DETA/DEA/DMAC, leading to accelerated DETA degradation and DEA formation. Various operational conditions including CO2 loading and degradation temperature were considered to build a systemic impact mechanism on thermal degradation for biphasic absorbents. Before phase separation, CO2 absorption and increasing temperature significantly exacerbated DETA degradation. However, phase separation behavior was found to effectively prevent the synergistic degradation reactions in the solution, leading to a 27.4 % reduction in the DETA degradation ratio of the aqueous phase after phase separation. Moreover, it achieved a 24.1 % reduction of the DETA degradation ratio caused by rising temperature in the solution after phase separation. Therefore, it is essential to ensure the completion of phase separation for biphasic solvents before entering the stripper in applications. After thermal degradation, the regeneration rate and cyclic capacity of DETA/DEA/DMAC were strengthened, which was 84.9 % and 63.3 % higher than that of 30 wt% MEA, respectively.

Oxidative degradation of aqueous PZ solution and AMP/PZ blends for post-combustion carbon dioxide capture

Aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) appear to be commercially attractive solvents for post-combustion CO2 capture by absorption/stripping. An experimental study on the oxidative degradation of aqueous PZ solutions and AMP/PZ blends was carried out. The oxidative degradation experiments were performed in a 200mL glass batch reactor with an oxygen partial pressure of 250kPa, and at the temperatures of 80–120°C. The amine loss was determined by cation ion chromatography (IC) while the degradation compounds were identified and quantified by gas chromatography–mass spectrometry (GC–MS), cation IC and anion IC. Possible chemical pathways of PZ oxidative degradation are proposed to account for the observed degradation products. As compared to oxidative degradation of single AMP and PZ solvents, no new product was observed in partially degraded AMP/PZ blends. However, PZ degraded faster in the blends than it degraded individually at identical degradation conditions.

Oxidative Degradation of Aqueous 2-Amino-2-methyl-1-propanol Solvent for Postcombustion CO2 Capture

2-Amino-2-methyl-1-propanol (AMP) and the blends of AMP with other amines appear to be commercially attractive solvents for postcombustion CO2 capture by absorption/stripping. Oxidative degradation experiments involving AMP aqueous solutions were performed in a 200 mL glass batch reactor with initial AMP concentrations of 5 mol·kg–1, oxygen partial pressures of 250–350 kPa, and at temperatures of 100–140 °C in order to elucidate the degradation mechanistic pathways. The amine loss was determined by cation ion chromatography (IC), while the degradation compounds were identified and quantified by gas chromatography–mass spectrometry (GC–MS) and anion IC. The possible chemical pathways of AMP oxidative degradation are proposed on the basis of the identified and quantified products and the context of the current amine degradation schemes. The role of O2 in the proposed pathways is much more explicit than the previously proposed MEA oxidation mechanisms.

Successive non-suppressed ion chromatography of common cations and anions using dual columns with single eluent.

A successive non-suppressed ion chromatography (IC) system for the determination of common cations (Na+, K+, Mg2+, Ca2+) and anions (Cl-, Br-, NO3-, SO4(2-)) was developed, using two separation columns and a single eluent. 5-Sulfoisophthalic acid eluent was very suitable for such separations with a commercially available cation-exchange column for the mono- and di-valent cations and with an ODS column coated with cetyltrimethylammonium for the anions. Both cations and anions were detected with conductimetrically high sensitivity without any suppressor. After injecting an aliquot of sample solution, the solvent front from the cation-exchange column, including most of the anionic species, was firstly accumulated into the additional 2 ml accumulation loop for 60 s, while the cation IC was performed. Subsequently, the accumulated fraction was introduced into the anion-exchange column and chromatographed. Relative standard deviations (RSDs) of retention times and conductimetric area responses for common cations were within 6% and within 4%, respectively. The linear relationships between molar concentration and detector response ranged from 0.01 to 1.00 mM with r2 of 0.9994 for Na+, 0.9992 for K+, 0.9993 for Mg2+, and 0.9988 for Ca2+. The successive anion IC through the accumulating process was also quantitative, with 95% recovery or over for each analyte. The linear ranges were between 0.01 and 1.00 mM with r2 of 0.9996 for Cl-, 0.9997 for Br-, 0.9993 for NO3-, and 0.9984 for SO4(2-). The method was applied to the determination of common cations and anions in several mineral waters and a hot spring water.

New development in the ion chromatography of cations

New development in the ion chromatography of cations