An experimental study on the degradation of aqueous solutions of alkanolamine blends, under the presence of carbon dioxide and hydrogen sulfide, was carried out. The studied alkanolamines were: diethanolamine (DEA), methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP). Degradation experiments were carried out at a temperature of 200 C. The mass fraction of DEA and MDEA in the studied aqueous solutions was 10% and 35%, respectively. AMP was incorporated into the MDEA-DEA aqueous solutions, with concentrations of (0-8) mass fraction. Partially degraded alkanolamine aqueous solutions were analyzed, after about 90 hours, by gas chromatography.It was found that in all the studied alkanolamine aqueous solutions the MDEA degrades more slowly than DEA under the same experimental conditions. Degradation of both alkanolamines was found to be almost independent of the AMP concentration. AMP exhibits an intermediate stability; it is more resistant to degradation than DEA but less than MDEA. In addition, thermal degradation of DEA and MDEA is minimal up to 200 C.
Water under subcritical conditions (250 • C, 4100 kPa) was used to extract polycyclic aromatic hydrocarbons (PAHs) from a Mexican hydrocarbon-contaminated soil. Extraction was carried out by continuously circulating the solvent through the sample contained in an extraction cell. After extraction, the non-extracted PAHs were eluted from the soil and then analyzed by high performance liquid chromatography. The elution and subsequent analysis were carried out by directly coupling the extraction cell, through a switching valve system, to a liquid chromatograph. The elution and analysis process takes place in a closed system that allows a fast, precise, and highly sensitive quantification of the studied compounds. Additional extraction experiments with spiked samples (silicon dioxide and nonpolluted soil) were carried out in order to asses the performance of the method. Extraction recoveries ranged from 95 to 100% with an average uncertainty of ±1.2%.
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