Tianze Liu,Xiaobin Liao,Xinna Lin,Jing Yu,Huan Qi,Zhibin Jiang,Jing Zou,Qingsong Li
This study was to evaluate the feasibility of controlling carcinogenic nitrosodiethylamine (NDEA) formation from greenhouse gas adsorbent 3-diethylaminopropylamine (DEAPA) by pre-O 3 in subsequent chlorination/chloramination processes. The result indicated that the NDEA yields (0.4 %) during chlorination was 1.3 times of that during chloramination (0.3 %); pre-oxidation with 4 mg/L O 3 significantly cut down its formation; the reduction rates were up to 67.5 and 48.5 %, respectively. OH scavenger greatly augmented the final NDEA amount from 1.86 to 5.05 μg/L during ozonation , while its roles on subsequent processes differed with disinfection methods as well as O 3 (g) dosages. Most of co-existed substances inhibited NDEA generation, except NO 2 − , CO 3 2− and SO 4 2− , which slightly promoted during ozonation. Basing on Gaussian calculation, GC/MS and UPLC-Q-TOF-MS analysis, the influencing mechanisms of pre-O 3 on NDEA formation in subsequent disinfection processes were proposed. In addition, the calculated toxicity analysis as well as the whole toxicity was applied to evaluate the possibility of pre-O 3 on risk control.
This work has investigated CO2 absorption using 3-(diethylamino)propylamine (DEAPA), a diamine that contains one primary and one tertiary amine in the same molecule. The results are compared with those for the blended amine system of monoethanolamine and methyldiethanolamine (MEA–MDEA), a mixed amine solvent with an equal number of moles of primary and tertiary amine. The 2 M DEAPA, 2 M MEA, and 4 M MEA–MDEA (1:1 mole ratio) were tested for their CO2 absorption performance. The experimental results show that the intramolecular tertiary amino group of DEAPA can promote the CO2 absorption rate of the intramolecular primary amino group and enhance its CO2 absorption capacity. The results using 13C nuclear magnetic resonance also showed that the intermolecular tertiary amine in the MEA–MDEA system was more favored for the promotion of the primary amine in the blend to form bicarbonate at an earlier CO2 equivalent loading stage and produced less carbamate than the intramolecular tertiary amino group of DEAPA did with respect to its primary amine. Furthermore, the CO2 equilibrium solubility of DEAPA was measured at different temperatures with various CO2 partial pressures, and then an empirical model based on these experimental data was developed. The results predicted by this model were fitted well with the experimental results. The Gibbs–Helmholtz equation was used to estimate the CO2 absorption heat of the DEAPA system, and the results showed that DEAPA has a CO2 absorption heat (−36.4 kJ/mol) lower than those of MEA, MDEA, and DEA. The results demonstrate that DEAPA has the potential to be an alternative solvent with a high absorption rate, a high CO2 capacity, and a low heat of absorption in CO2 capture processes.
The main issue for the development of CO2 capture in industry is its high energy cost. In this work, the regeneration of the chemical solvent 3-(diethylamino)propylamine (DEAPA) with or without catalyst was studied to further reduce the energy consumption. Three different catalysts (SAPO-34, MCM-41, and SO42–/TiO2) were applied into the DEAPA system to enhance the energy efficiency by lowering the heat cost per mole of CO2 released in a CO2 stripping process. The results show that solely DEAPA (without catalyst) can increase the CO2 desorption rate by 37.28%, increase the cyclic capacity by 38.02%, and reduce the heat duty by 14.85% compared to 5 M monoethanolnamine (MEA). In addition, for the catalyst–DEAPA systems, DEAPA-SAPO-34, DEAPA-MCM-41, and DEAPA-SO42–/TiO2 could lower the heat duty by 33.08%, 27.79%, and 22.41%, respectively, relative to 5 M MEA. The SAPO-34 catalyst also shows a better efficiency for increasing the CO2 desorption rate and cyclic capacity compared to the other two catalysts used. Moreover, a possible catalytic mechanism for CO2 desorption from the DEAPA–catalyst system is proposed based on the results from catalyst characterization. Through comparing the parameters of each catalyst, it can be inferred that the mesopore surface area (MSA) and the total acid sites (TAS) are the critical factors for an efficient catalyst. The combination of MAS*TAS could especially act as a key value to evaluate the performance of a catalyst for catalytic CO2 desorption.
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