Development of carboxyl-layered double hydrotalcites of enhanced CO2 capture capacity by K2CO3 promotion

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Adsorption, ISSN: 0929-5607, Vol: 23, Issue: 2-3, Page: 239-248

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Shuang Li; Yixiang Shi; Hongyu Zeng; Ningsheng Cai
Springer Nature
Chemistry; Chemical Engineering; Physics and Astronomy
article description
Layered double hydroxides have been comprehensively studied as adsorbent precursors for CO capture at 250–500 °C. Layered double hydroxides take advantages of partial reversibility by pressure change of adsorbate and good selectivity to CO contributed by active basic sites. However, they suffer from comparatively lower CO capture 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, KCO promoted n-caprylate (CH(CH)COO) LDH and KCO promoted stearate (CH(CH)COO) LDH were synthesized by combining long carbon-chain carboxylic anion intercalation and KCO promotion. KCO surface promotion raised CO capacity 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 CO uptake 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 CO on LDHs only by changing the partial pressure of CO at the same operation temperature. Both novel LDHs show good potential for PSA application.