Regulating WOx coordination environment improves proton transfer for catalytic amine regeneration in CO2 capture

Catalyst-aided regeneration is a promising method for reducing the high regeneration energy consumption of amine-based CO 2 capture technologies. However, the intrinsic relationship between the properties of the acidic sites and their catalytic activity is controversial. In this study, a series of W-based catalysts supported by ZrTiO x were synthesised, and the effects of the intensity, distribution, and type of acid sites were systematically investigated by quantitatively regulating the acidic site properties. The results indicate stronger acidic sites play a more important role in the catalytic reaction. Moreover, the catalysts showed excellent performance only if the Brønsted acid sites (BASs) and Lewis acid sites (LASs) coexisted. During the catalytic reaction, the BASs facilitated deprotonation, and the LASs promoted the decomposition of carbamates. The ratio of BASs to LASs (B/L) was a critical factor for catalytic activity, wherein optimal performance was achieved when the B/L ratio was close to 1. The 10% HPW/ZrTiO x composite performed better than WO 3 /ZrTiO x and HSiW/ZrTiO x because it had a stronger acid intensity and a suitable B/L ratio. As a result, the relative heat duty was reduced by 47% compared to 30% aqueous MEA, and the maximum CO 2 desorption rate was increased by 83%. The Bader charge indicated that the W atoms of HPW/ZrTiO x lost more electrons (0.18) than those of WO 3 /ZrTiO x , which can weaken the O–H bond energy. Consequently, the calculated deprotonation energy is as low as 257 kJ/mol for HPW/ZrTiO x . • Strong Brønsted acid sites assist catalysts in efficiently desorbing CO 2 . • Synergistic desorption of CO 2 with an optimal ratio of strong Brønsted acid and strong Lewis acid. • Enhancement of catalyst acidic strength by increasing the electron loss of catalyst metal atoms. • Modulation of catalyst acid sites to increase and match tandem steps in the CO 2 desorption reaction to increase acid site utilization.