Insight of catalytic desorption of CO2-rich amine solution over dealuminated HZSM-5 modified with metal oxides

Amine-based solution absorption as the most promising and commercialized CO 2 capture method, attracted the increasing attention. However, its key lies in improving the CO 2 desorption performance while reducing the energy consumption in desorption. In this paper, HZSM-5 was dealuminated by sulfuric acid, further loaded by Fe 2 O 3 , Co 3 O 4 , NiO and ZnO via impregnation method and used in catalytic desorption of the blended amine solution of N-methyl-diethanolamine and piperazine. Results indicated that sulfuric acid leaching increased the number of acid sites and mesoporous surface area. When sulfuric acid reached 0.8 mol/L, the resultant catalyst (0.8H 2 SO 4 -HZ) improved the amount of the desorbed CO 2 by 10.26% and decreased the heat duty to 2128 kJ/mol CO 2 , with a reduction of 17.01% compared to non-catalytic system. The loading of metal oxides on 0.8H 2 SO 4 -HZ decreased surface area and changed acidity of catalysts. CO 2 desorption amount under catalysis of metal oxide modified M /0.8H 2 SO 4 -HZ followed the order of Fe/0.8H 2 SO 4 -HZ > Zn/0.8H 2 SO 4 -HZ > Ni/0.8H 2 SO 4 -HZ > Co/0.8H 2 SO 4 -HZ, whereas the relative heat duty was in order of Zn/0.8H 2 SO 4 -HZ > Co/0.8H 2 SO 4 -HZ > Ni/0.8H 2 SO 4 -HZ > Fe/0.8H 2 SO 4 -HZ. Fe/0.8H 2 SO 4 -HZ exhibited excellent catalytic performance, along with 12.82% increase in amount of CO 2 desorbed and reduction in heat duty to 2039 kJ/mol CO 2 , with a 20.49% decrease. Meanwhile, Fe/0.8H 2 SO 4 -HZ showed good stability after ten cycles and the addition of Fe/0.8H 2 SO 4 -HZ promoted CO 2 absorption. Suitable pore structure and abundant acid sites of the modified catalyst contributed to proton transfer and decomposition of carbamate. A possible mechanism for catalytic desorption over modified HZSM-5 was proposed. The work indicates that catalytic desorption by modified HZSM-5 catalyst is a promising way to decrease the energy consumption of amine solution regeneration.