Catalytic-CO₂-Desorption Studies of DEA and DEA–MEA Blended Solutions with the Aid of Lewis and Brønsted Acids

Abstract

Heat-duty reduction is the major challenge in CO 2 desorption and amine regeneration. The use of a combination of heterogeneous catalytic desorption with improved amine solvents is a novel approach to address this issue. We studied CO 2 -desorption tests of noncatalytic diethylamine (DEA) solvents as a benchmark and focused on five blended amines (DEA−monoethanolamine, MEA; 4.5:0.5 to 2.5:2.5 M) with three types of catalysts (γ-Al 2 O 3 , H-ZSM-5, and 2:1 blended γ-Al 2 O 3 −H-ZSM-5) to explore the synergy effects of DEA-based amine blends with solid catalysts. The heat duty and CO 2 production of each case scenario were tested for six sets of solutions with initial loading of 0.5 mol of CO 2 per mole of amine at 363−378 K and were compared with those of 5 M DEA solvents. The results showed that the three catalyst conditions (blended catalyst, H-ZSM-5, and γ-Al 2 O 3 ) followed different trends at rich and lean loadings. Finally, both 5 M DEA and 4.5:0.5 M DEA−MEA with blended catalysts exhibited very low heat duties of 151.2 and 168.0 kJ per mole of CO 2 at loadings of 0.50− 0.20 mol per mole of amine at 378 K among the six solutions. Both approaches proved to be the most-energy-efficient amine solutions whereas the blended amine with blended catalysts was the best strategy that was applicable in the CO 2 desorber.

Study of Catalytic CO2 Absorption and Desorption with Tertiary Amine DEEA and 1DMA-2P with the Aid of Solid Acid and Solid Alkaline Chemicals

“…An open recirculation-process (Figure S2) vessel equipped with an electrometer [9,26,37] was adopted to conduct the CO 2 desorption tests under atmosphere to extract DEEA and 1DMA-2P solvents at 1.0 mol/L, 1.5 mol/L and 2.0 mol/L, and two types of solid acid catalyst were used as γ-Al 2 O 3 and H-ZSM-5 representing Lewis acids and Brønsted acids [9,26]. The acidic catalytic conditions were 5.0 g, 7.5 g and 10.0 g, This CO 2 desorption process was similar to that of others in the literature [9,26]. In this study, 250 mL of the amine solvent was put into the flask with a volume of 500 mL.…”

“…The experimental procedures were similar to those in our previous study [26]. The process was stirred and heated to 363 K. Based on the analysis of the CO 2 loading of samples at 0−4 h, the catalytic effects on CO 2 desorption were evaluated.…”

“…The catalytic effects were verified of CaCO 3 and MgCO 3 toward MEA (19) and DEA (20) on CO 2 absorption, and also (γ-Al 2 O 3 and H-ZSM-5) to MEA [9,21,22,23] and DEA [26] on CO 2 desorption. These catalytic effects toward tertiary amines were the purpose of this study.…”

“…The role of Lewis acid (γ-Al 2 O 3 ) and BrØnsted acid for CO 2 desorption with MEA and DEA has already been discussed repeatedly [9,21,26].…”

“…However, the effects of both solid bases onto a tertiary amine have rarely been discussed either. The effects of solid acid catalysts (γ-Al 2 O 3 , H-ZSM-5, TiO(OH) 2 , and transition metal oxides V 2 O 5 , MoO 3 , WO 3 , TiO 2 , and Cr 2 O 3 ) to MEA [9,21,22,23,24,25] and DEA [26] have also been studied and proven to be effective in the reduction of heat duty. Some studies have been completed to investigate the effects of solid acid catalysts (H-ZSM-5, MCM-41 and SO 4 2− /ZrO 2 ) with blended amine solvents of 5 + 1.0 mol/L MEA-DEEA and MEA-1DMA-2P [9].…”