Development of carboxyl-layered double hydrotalcites of enhanced CO2 capture capacity by K2CO3 promotion
- Citation data:
Adsorption, ISSN: 0929-5607, Vol: 23, Issue: 2-3, Page: 239-248
- Publication Year:
- Chemistry; Chemical Engineering; Physics and Astronomy
Layered double hydroxides have been comprehensively studied as adsorbent precursors for COcapture at 250–500 °C. Layered double hydroxides take advantages of partial reversibility by pressure change of adsorbate and good selectivity to COcontributed by active basic sites. However, they suffer from comparatively lower COcapture capacity, commonly 0.28–0.70 mmol/g in previous studies, compared with typical physical adsorbents like zeolites or chemical sorbents such as calcium oxide. In this paper, KCOpromoted n-caprylate (CH(CH)COO) LDH and KCOpromoted stearate (CH(CH)COO) LDH were synthesized by combining long carbon-chain carboxylic anion intercalation and KCOpromotion. KCOsurface promotion raised COcapacity to 1.36 mmol/g for K-promoted magnesium–aluminum n-caprylate LDH and 1.97 mmol/g for K-promoted magnesium–aluminum stearate LDH respectively. Thermal gravimetric analysis was used to test COuptake up to 1000 kPa. It was found that adsorption kinetics fitted Elovich equation. X-ray diffraction was deployed to detect the crystal patterns of both precursors and adsorbents. In situ fourier transformation infrared spectroscopy and temperature programmed desorption were used to monitor the bonding between surface basic sites and adsorbate during adsorption and desorption process, in order to illustrate the adsorption mechanism of COon LDHs only by changing the partial pressure of COat the same operation temperature. Both novel LDHs show good potential for PSA application.