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The CO2 phase change absorbent, CPCA, as a novel alternative absorbent, has attracted great attention recently. In this work, the CPCAs composed of MDEA/C4–C6 alcohol/H2O were developed by means of the cosolvent effect. The cosolvent effect of MDEA on the solubility of C4–C6 alcohols in H2O was verified. The CPCAs composed of MDEA/1-butanol/H2O were further examined including the species distributions, absorption rate, cycling capacity and regenerability. The initial absorption rates of all CPCAs were higher than that of 30% MDEA, and its maximum value was 2.5 times higher. A different behavior was shown for the CPCAs that an increase in the absorption rate was observed for a period of time when the CPCAs became turbid. The optimal CO2 cycling capacity of CPCA was 2.48 mol CO2 kg−1, which was 70% higher compared to 30 wt% MDEA.

By using the salting-out phenomenon to induce phase separation, the novel CO 2 phase change absorbents (CPCAs) composed of MEA/water-miscible alcohol/H 2 O were developed. The absorbents using 1-propanol, 2-propanol and tertiary butanol as the diluent were selected as CPCAs. The CPCAs composed of MEA/1-propanol/H 2 O were further examined include the species distributions in the two phases, physical properties, cyclic capacity and absorbent regenerability. In comparison to 30 wt% MEA/H 2 O, the optimal CO 2 cycle capacity of CPCA is 2.59 mol CO 2 /kg which increase 62% and the volume of CPCA sent to the stripper decreased over 67%. The developed CPCAs would benefit to reduce energy consumption of CO 2 capture.

Due to the high energy consumption in CO2 capture by amine absorbents, CO2 phase change absorbent, CPCA, has attracted a great attention in research institutes recently. Two phases are formed after CO2 absorption with CPCA as the absorbent, and only the CO2-rich phase goes to the stripper, which could potentially reduce the energy consumption. In this work, the CPCAs composed of MEA/1-propanol/H2O were developed based on the principles of aqueous two-phase systems. The effects of temperature, amine concentration, and total CO2 loading on the phase separation of CPCAs were studied. CO2 loading and 1-propanol distributions in two phases under different experimental conditions were measured. The results indicated that the total CO2 loading is the key factor affecting the distribution of components in two phases. Moreover, in comparison to traditional 30 wt % MEA, the initial absorption rates of all CPCAs were higher than that of MEA, and its maximum value was 5 times higher. The cyclic capacity of the CPCA w...

Activators such as piperazine (PZ) are widely used to increase the CO2 absorption rate of aqueous methyldiethanolamine (MDEA) solutions by accelerating reaction. However, a big difference (1 to 2 orders of magnitude) in the enhancement of absorption rate with the addition of PZ was obtained in different studies. In this work, it was proved that mass transfer is the rate-limiting step in the above process and in most cases enhancing mass transfer is quite essential. Some low-polar solvents were screened as “mass transfer promoters (MTPs)” to enhance mass transfer by inducing interfacial turbulence, which markedly improved the CO2 absorption performance of MDEA solutions. The individual addition of PZ and MTPs to the MDEA solution, which correspond to the reaction enhancement and the mass transfer enhancement, increased the absorption rate by 131% and 33%–319%, respectively. The co-effects of enhancing both reaction and mass transfer (in the presence of activators and MTPs) can lead to 2 to 10-fold increase in the absorption rate. Furthermore, MTPs could increase the CO2 cyclic loading and desorption rate by 27% and 100%, respectively, indicating that the MDEA/MTPs had significant advantages for reducing the energy consumption in CO2 capture applications.