The salt-based catalytic enhancement of CO₂ absorption by a tertiary amine medium

Abstract

The rise in atmospheric CO2 levels due to the effects of human activities poses a serious threat to the world's ecosystems because of global warming and climate change. Efficient methods are needed to limit the elevation of CO2 level in the atmosphere. Here, we propose an improved CO2 sequestration method that uses new catalysts, specifically a series of tertiary amine nitrate salts, in an aqueous tertiary amine medium. We synthesized the new catalysts and characterized them by using 1 H and 13 C NMR, single crystal X-ray spectroscopy, and FT-IR spectroscopy. The effects of the catalysts on CO2 absorption were assessed by using a stopped-flow spectrophotometer, and their heats of absorption and CO2 absorption capacities were measured with a differential reaction calorimeter (DRC) at high concentrations of the tertiary amine medium. The CO2 hydration rate constants were determined under basic conditions and the catalysts were found to exhibit higher absorption of CO2 (a highest value of 430 M -1 s -1 ) than the tertiary amine medium (133 M -1 s -1 ). The increased absorption of CO2 and the low heat absorption energies of the new catalysts suggest that they could be used in postcombustion processes.

Catalytic Characteristics of Metal Catalysts and Nitrate Salt of a Tripodal Ligand in a Basic Medium for Postcombustion CO2 Capture Process

“…However, previous research efforts on the addition of metal catalysts for CO 2 absorption rate enhancement in the tertiary amine media tended to be less active in highly concentrated amine media. Very recently, our group has shown that the CO 2 absorption rate of the tertiary amine can be improved using tridentate and tetradentate ligand-based metal catalysts. , In addition to that, the salt-based catalytic enhancement of CO 2 hydration rate (0.430 × 10 3 M –1 s –1 ) was also observed . However, the tridentate and tetradentate ligand-based metal catalysts were partially soluble and less active in the concentrated basic-aqueous medium, and the salt-based catalysts were less effective than the metal catalysts.…”

“…An interesting approach to improve the CO 2 absorption kinetics in tertiary amines is the addition of catalysts. , Carbonic anhydrase (CA) mimics and metal catalysts have been used to improve the CO 2 absorption rates in tertiary amine solvent. − The use of metal catalysts in strongly basic media (2.5 M) requires the catalysts to be soluble and highly active. However, previous research efforts on the addition of metal catalysts for CO 2 absorption rate enhancement in the tertiary amine media tended to be less active in highly concentrated amine media.…”

“…An interesting approach to improve the CO 2 absorption kinetics in tertiary amines is the addition of catalysts. 22,24 Carbonic anhydrase (CA) mimics and metal catalysts have been used to improve the CO 2 absorption rates in tertiary amine solvent. 25−27 The use of metal catalysts in strongly basic media (2.5 M) requires the catalysts to be soluble and highly active.…”

“…25,26 In addition to that, the salt-based catalytic enhancement of CO 2 hydration rate (0.430 × 10 3 M −1 s −1 ) was also observed. 24 However, the tridentate and tetradentate ligand-based metal catalysts were partially soluble and less active in the concentrated basic-aqueous medium, and the salt-based catalysts were less effective than the metal catalysts. To improve the CO 2 absorption rate in the concentrated aqueous tertiary amine medium, the tripodal-based metal catalysts have been combined and are highly soluble even in 2.5 M of tertiary amine medium.…”

Molecular Rh(III) and Ir(III) Catalysts Immobilized on Bipyridine-Based Covalent Triazine Frameworks for the Hydrogenation of CO2 to Formate

“…The burgeoning interest of CO 2 as an energy vector for renewable fuel storage and as a C 1 building block for chemical production has renewed attention on CO 2 hydrogenation into formic acid [1][2][3][4][5][6][7][8]. Formic acid and its salts are used as basic chemicals in various industries [9], and are regarded as a liquid form of hydrogen, which is strongly viewed as an ultimate renewable fuel by the scientific and technological community [10].…”