Coal-fired flue gas is a major source of greenhouse gas CO 2 . Phase-change absorbents can be used to reduce energy consumption associated with regeneration during CO 2 capture. In this study, N,N-dimethylbutylamine (DMBA) and N,N-dimethylbutylamine (DEEA) were mixed to develop phase-change absorbents, and the reaction kinetics of CO 2 absorption in the absorbents were examined. A bubbling device was used to prepare phase-change absorbents with different CO 2 loading levels. The physico-chemical parameters of the absorbents under different conditions were specified, and the changes in the CO 2 loading of the upper and lower layers of the absorption solutions after a liquid–liquid separation were analyzed. A wetted-wall column was subsequently used to investigate the effects of temperature, CO 2 loading, gas flow rate, and DMBA/DEEA composition ratio on CO 2 absorption rate. This study determined that the flow velocity, reaction temperature, and CO 2 loading affected the CO 2 absorption rates to a certain extent. In addition, comparing the reactive properties of the 4M DMBA + 2M DEEA and 2M DMBA + 4M DEEA absorbents under the same experimental conditions revealed that the 4M DMBA + 2M DEEA absorbent exhibited higher absorption rate and reaction stability. A kinetics model also indicated that the CO 2 absorption of the phase-change absorbents used in this study was mainly affected by the liquid film diffusion process. This study contributes theoretically to the development of CO 2 absorption technologies.
The absorption amount ( m ) and loading ( α ) of CO 2 in 2-(ethylamino)ethanol (EAE) activated 3-(dimethylamino)propan-1-ol (3DMA1P) aqueous solution were measured. The temperatures ranged from 303.2 K to 323.2 K. The mass fractions of 3DMA1P and EAE respectively ranged from 0.3 to 0.5 and 0.01 to 0.03. The effects of temperature ( T ) and mass fractions of amines ( w ) on the absorption performance were illustrated. It’s impressive that the addition of very small amounts of EAE into 3DMA1P aqueous solution significantly enhanced the absorption performance. Moreover, comparison showed that 3DMA1P-EAE aqueous solution appeared much higher CO 2 absorption capacity than the widely used MDEA-MEA aqueous solution. Tray towers with different plates ( N p = 6, 8 and 10) were used to verify the removal efficiency of CO 2 ( η CO 2 ) and the effects of gas flow rate ( G ), absorbent flow rate ( L ), w , absorbent feed temperature ( T ) and N p on η CO 2 were illustrated. Our results showed that when composed of 30% to 50% (mass percent) 3DMA1P and 3% EAE, the absorbents achieved η CO 2 higher than 90%, which met the efficiency requirement specified in a power plant, thus leading to a promising industrial application in the CO 2 capture process.
The synthesis of SAPO-34 hollow fiber membranes employs the ball-milling assistant method to enhance membrane yield and quality. These membranes are then combined with CrO x /Al 2 O 3 catalyst to create a packed bed membrane reactor (PBMR) for propane dehydrogenation (PDH). The study investigates the impact of operating temperatures, weight hourly space velocities (WHSV), and sweep gas flow rates on the SAPO-34 zeolite membrane reactor's performance, comparing it to a traditional packed bed reactor (PBR). The removal of hydrogen from the reaction side significantly improves propane conversion, surpassing thermodynamic equilibrium. In PBMR, propylene selectivity slightly exceeds that in PBR, influenced by side reactions like hydrogenolysis and cracking after hydrogen removal. Furthermore, the SAPO-34 zeolite membrane reactor undergoes a prolonged stability test with frequent regeneration using pure propane as feedstock to simulate industrial conditions. It exhibits consistent performance over 120 regeneration cycles within 240 h, maintaining similar H 2 permeability and H 2 /C 3 H 8 selectivity as the fresh membrane post long-term testing.
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