Integrated CO 2 capture and utilization (ICCU) is an emerging technology to reduce CO 2 emissions by greatly simplifying the processes of conventional CO 2 capture and utilization. In particular, ICCU-methanation could directly convert the low-concentration CO 2 into CH 4 using hydrogen from new energy electricity, representing an efficient Power-to-Gas route. CO 2 adsorption/catalytic materials play a crucial role for the operation of ICCU-methanation, and it is more feasible to scale up material production and avoid components interference by directly combining the sorbent and catalyst. However, it is necessary to reveal the effect of different arrangements of sorbent and catalyst on reaction characteristics of ICCU-methanation. In the work, the matching of K 2 CO 3 -doped Li 4 SiO 4 sorbent with various supported Ni-based catalyst was tested and four arrangements of sorbent and catalyst particles in a fixed-bed were investigated to understand the influences on ICCU-methanation. Results show that the presence of catalyst accelerates CO 2 supply by sorbent and achieves quicker methanation, and the promotion effect becomes more obvious with a closer contact between the sorbent and catalyst. Under optimized conditions, ICCU-methanation of uniformly mixed K-Li 4 SiO 4 and Ni/Al 2 O 3 shows an excellent performance with very stable CO 2 conversion of 95.58% and CH 4 selectivity of 93.29% during cyclic reactions.
Zongze Lv,Changlei Qin,Shuzhen Chen,Dawid P. Hanak,Chunfei Wu
CO 2 capture and utilization has been considered as an up-and-coming short- to mid-term approach to mitigate the excessive CO 2 emission. Comparing to the conventional separate capture, transportation and conversion arrangement, the integrated CO 2 capture and utilization (ICCU) could largely simplify the complex process and reduce the energy consumption. However, the poor stability of high-temperature CO 2 sorption/desorption severely limit the potential of ICCU. Therefore, it is indispensable to develop a new sorbent/catalyst system ensuring the high-efficiency and long-term operation of the ICCU. In this paper, we propose and demonstrate the feasibility and performance of using K 2 CO 3 -doped Li 4 SiO 4 as an efficient CO 2 sorbent for ICCU operating at a relatively low temperature by dry reforming of methane. Results show that the ratio of H 2 /CO produced is stabilized at 1 ± 0.05 in the pre-breakthrough stage, and the duration extends to be 1.6 times of the original value in the cyclic operations, displaying an excellent performance in reaction matching and process stability.
Calcium looping (CaL) represents a promising technology for CO 2 capture from flue gas. Nevertheless, CaO-based sorbents, characterized by high theoretical absorption capacities and low costs, experience significant degradation in CO 2 capture capacity during continuous cycling. In the present study, a novel K 2 CO 3 -doped CaO sorbent was synthesized through a concurrent hydrophilic impregnation process, and the performance of consecutive cyclic CO 2 capture was evaluated. The optimal 0.05 K-CaO demonstrated the highest CO 2 sorption (12.4 mmol/g), maintaining about 64 % of the initial sorption after 20 repetitive cycles under N 2 calcination atmosphere, which is 6.6 times greater than that of CaO. These findings indicated that K 2 CO 3 can regulate the particle size and the state of surface oxygen species in CaO-based sorbents while simultaneously enhancing CO 2 diffusivity on the sorbent surface. The DFT calculations indicated that the incorporation of K 2 CO 3 improved the mechanism of CaO chemisorption of CO 2 . Additionally, the vacancies and CO 3 2– generated by K 2 CO 3 doping can enhance the CO 2 sorption energy and reduce the system’s energy level. Notably, the net charge transfer for CO 2 sorption from K 2 CO 3 doping is greater than that from pure CaO, and the O atoms on the surface of K 2 CO 3 -CaO (001) exhibit strong covalent interactions with the C atoms in CO 2 , both of which facilitate CO 2 chemisorption. This study offers a comprehensive theoretical mechanism for the incorporation of K-based alkali metals to enhance the CO 2 capture performance of CaO sorbents.
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