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[Display omitted] • K 2 CO 3 /Al 2 O 3 adsorbent pellets were prepared via the hydrophobic interface-assisted method. • High temperatures make hydrophobic powders lose their hydrophobicity. • Residual hydrophobic powders inhibits the diffusion of water molecules due to hydrophobicity. • The detrimental effect of the hydrophobicity exceeds that of high temperature. Suitable molding and granulation methods are crucial, and an outstanding sphere structure can play a better role in the future scale-up industrial application of K 2 CO 3 -based CO 2 adsorbent. Water will form a large contact angle on the surface of hydrophobic solution and become sphericity water. In this work, hydrophobic powders (polyethylene (PE), TiO 2 , and SiO 2) were selected in the hydrophobic interface-assisted method. The CO 2 adsorption capacity of TiO 2 pellets is 0.50 mmol/g, while that of PE pellets is 0.24 mmol/g, and finally that of SiO 2 pellets is 0.36 mmol/g. Then, experiment proved that high temperature (>500 ℃) makes the hydrophobic powders (i.e, TiO 2 and SiO 2) lose hydrophobicity which make water molecules diffuse faster, while PE is completely decomposed at high temperature. Compared with the pellets calcined at 300 ℃, the TiO2 pellets calcinated at 500 ℃ have an adsorption capacity of 0.70 mmol/g, which is over 1.72 times that of the original pellets, and the other two hydrophobic surfaces are also improved to some extent. Additionally, the appropriate ratio of low-temperature pore forming agent (i.e., urea) can help improve the adsorption performance, while excessive addition will lead to poor CO 2 adsorption performance. In addition, the K 2 CO 3 /Al 2 O 3 pellets also exhibited desirable mechanical properties, with an optimal compressive strength of 41 Mpa. Therefore, the loss of hydrophobicity leads to more active diffusion of water molecules, which may provide a new idea for the future development of CO 2 adsorbents and other areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Graphite-casted K 2 CO 3 -based adsorbent pellets with different supports were prepared. • ZrO 2 -supported K 2 CO 3 pellets exhibit outstanding performance for CO 2 adsorption. • 500 °C is the optimal calcination temperature for SiO 2 -supported K 2 CO 3 pellets. • SiO 2 -supported K 2 CO 3 adsorbent pellets possess excellent practicality for its low cost. K 2 CO 3 -based adsorbent pellets produced by graphite-casting method are promising alkali metal-based solid CO 2 adsorbents. The incorporation of porous metal oxide supports is an effective to enhance CO 2 adsorption capacity of K 2 CO 3 -based adsorbent pellets. In this work, graphite-casted K 2 CO 3 -based adsorbent pellets incorporated with different porous supports (i.e., TiO 2 , ZrO 2 , and SiO 2) were prepared for CO 2 capture. Comparatively, the ZrO 2 -supported, K 2 CO 3 pellets loaded with 30 wt% of K 2 CO 3 exhibit the highest CO 2 adsorption capacity, approximately 0.93 mmol/g. For the SiO 2 -supported K 2 CO 3 adsorbent pellets, the high calcination temperature (>700 °C) required to remove the graphite layer covering the pellet surface will cause the formation of new eutectics (i.e., K 2 Si 2 O 5 and K 2 Si 4 O 9), which leads to the collapse of the adsorbent pellets. Low calcination temperature of 500 °C can avoid the collapse of the SiO 2 -supported K 2 CO 3 adsorbent pellets and remove most of the graphite on the surface. Moreover, the CO 2 adsorption capacity can be further increased to 1.30 mmol/g by adding 20 wt% of microcrystalline cellulose to the SiO 2 -supported K 2 CO 3 adsorbent pellet. Although the adsorption capacity of structurally improved, SiO 2 -supported K 2 CO 3 pellets is still inferior to that of structurally improved, ZrO 2 -supported K 2 CO 3 pellets, they exhibit great cost advantage. Therefore, SiO 2 -supported K 2 CO 3 pellets with 20 wt% of microcrystalline cellulose have industrial application prospects. [ABSTRACT FROM AUTHOR]

• K 2 CO 3 -based adsorbent pellets were prepared via graphite-casting method. • Residual graphite inhibits carbonation reaction due to hydrophobicity of graphite. • The detrimental effect of the residual graphite exceeds that of high temperature. • The addition of microcrystalline cellulose can improve adsorbent performance. • Graphite-casted K 2 CO 3 -based adsorbent pellets possess good mechanical property. The desirable CO 2 adsorption capacity and mechanical property are both important for the large-scale industrial applications of K 2 CO 3 -based CO 2 adsorbents. In this work, graphite-casted, Al 2 O 3 -supported, K 2 CO 3 -based pellets were prepared for CO 2 adsorption. The prepared K 2 CO 3 -based pellets containing 30 wt% of K 2 CO 3 calcinated at 900 °C exhibit CO 2 adsorption capacity of 1.4 mmol/g, which is over 2.5 times that of the pellets calcinated at 300 °C. It is mainly attributed to the residual graphite coating on the surface of the K 2 CO 3 -based pellets calcinated at 300 °C, which inhibits the diffusion of H 2 O due to the hydrophobicity of graphite and further causes the poor carbonation performance. Moreover, the addition of 40 wt% of microcrystalline cellulose can further enhance the adsorption capacity of the graphite-casted K 2 CO 3 -based pellets to ∼1.95 mmol/g due to the improved pore structure. However, excessive addition of microcrystalline cellulose (50–60 wt%) will lead to poor CO 2 adsorption performance (1.07–1.16 mmol/g) because of the active sites within the pellets being covered by molten K 2 CO 3. Additionally, the structurally improved K 2 CO 3 -based pellets also exhibit desirable mechanical property with a compression strength of 69.45 MPa. Comprehensively considering the simple and easily scaled-up preparation route of graphite-casting method, the structurally improved, graphite-casted, Al 2 O 3 -supported, K 2 CO 3 -based pellets possess potential practical application prospect. [ABSTRACT FROM AUTHOR]

• Ni-Na 2 ZrO 3 bifunctional materials were prepared by different synthetic modes. • Integrated CO 2 capture and RWGS performance for CO production was evaluated. • Structure-property-activity relationships of Ni-Na 2 ZrO 3 samples were clarified. • Detailed reaction paths of ICCU-RWGS over Ni-Na 2 ZrO 3 was illustrated. Integrated CO 2 capture and utilization by reverse water gas shift (ICCU-RWGS) reaction for syngas production for C1 chemical industry has gained increasing attention. Designing highly active bifunctional materials that enables CO 2 adsorption and in-situ conversion is essential. In this work, Ni-Na 2 ZrO 3 bifunctional materials are prepared by different synthetic methods for ICCU-RWGS. N 2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO 2 temperature-programmed desorption (CO 2 -TPD) and H 2 temperature-programmed reduction (H 2 -TPR) analysis reveals that Ni-Na 2 ZrO 3 -CP prepared by the co-precipitation (CP) method shows small Ni crystalline size, moderate surface basicity, and excellent reducibility. ICCU-RWGS performance is investigated under isothermal conditions of 650 °C, 10 %CO 2 and 35 %H 2. The results indicate that Ni-Na 2 ZrO 3 -CP demonstrates excellent performance in ICCU-RWGS, with a notable CO 2 capture capacity of 3.76 mmol CO 2 /g and a CO production rate of 3.10 mmol CO/g. Additionally, it exhibits relatively good operational stability. Detailed reaction paths of the ICCU-RWGS procedure for the Ni-Na 2 ZrO 3 bifunctional materials are proposed. The findings will shed new perspectives on the design of synthetic bifunctional catalysts for ICCU-RWGS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four materials are successfully used to produce CaO-based pellets. • Nano-TiO 2 is the most suitable for producing CaO-based pellets as hydrophobic layer. • Al(NO 3) 3 surpasses alumina powder and sol on improving stability of CaO-based pellets. • Higher load of Al-based stabilizer contributes to the superior cyclic stability. Granulation serves as an effective strategy for mitigating the elutriation of CaO-based sorbents in the fluidized bed-based Calcium Looping system designed for CO 2 capture. Here, hydrophobic interface-assisted casted CaO-based sorbent pellets were prepared via a range of hydrophobic materials, i.e., graphite, Nano-titanium dioxide, Nano-silica, and polyethylene powders. The contact Angle values of the composite slurry droplets for the four hydrophobic materials range from 126 to 143°, which can provide enough surface tension to form CaO-based sorbent pellets. Moreover, the Al-based stabilizer precursors in the form of oxide, nitrate and sol, respectively, were incorporated into CaO-based pellets aiming to enhance their cyclic CO 2 uptake stability. Soluble aluminum nitrate exhibits the superior performance on enhancing CO 2 uptake stability compared to Nano-alumina and alumina sol, whose superiority lies in its ability to disperse more evenly with the active CaO component. Therefore, the Al-supported CaO-based pellet (∼30 wt% of Ca 12 Al 14 O 33) with aluminum nitrate as the precursor of Al-based stabilizer remains excellent CaO carbonation conversion of 50.3 % after 20 cycles, approximately 2 times that of pure CaO pellet. Even under harsh calcination condition (950 ℃, 100 vol% CO 2), the Al-supported CaO-based pellet is still markedly superior to CaO pellet for cyclic CO 2 capture. The freshly calcined Al-supported CaO-based pellet exhibits highly desirable compressive strength (3.4 ± 0.83 MPa), compared to 0.35 ± 0.07 MPa for pure CaO pellet. The generated inert Ca 12 Al 14 O 33 skeleton provides structural stability and strength to the Al-supported, CaO-based pellets, which simultaneously contributes to the enhanced cyclic CO 2 uptake capacity and mechanical property. [ABSTRACT FROM AUTHOR]

CaO-based dual function materials (DFMs) with different metallic catalysts (Ni, Co, Mn or Fe) incorporated were prepared by the one-pot synthesis method for integrated CO 2 capture and reverse water gas shift reaction (ICCU-RWGS) for CO production. [Display omitted] • M@CaO (M = Ni, Co, Mn and Fe) DFMs are prepared for CaL-RWGS applications. • Influence of catalyst component on CaL-RWGS performance is investigated. • The interactions between catalyst and CaO affect the physicochemical properties of the DFMs. • Carbonation and regeneration kinetics of the DFMs in CaL-RWGS are demonstrated. • Mn@CaO exhibits good CaL-RWGS performance with high CO 2 uptake and great CO yield. Integrating calcium-looping cycle (CaL) with reverse-water–gas-shift (RWGS) reaction represents an effective path to realizing integrated CO 2 capture and utilization (ICCU). Screening a suitable catalyst to construct highly efficient CaO-based dual function materials (DFMs) is essential for CaL-RWGS. In the current work, M@CaO (M = Ni, Co, Mn, and Fe) DFMs are prepared for CaL-RWGS, and the influence of catalyst component on the structure, CO 2 capture and RWGS performance, and kinetic behaviors of the CaO-based DFMs is investigated. Results show that the interaction between CaO and catalyst affects the average grain size and dispersion of metallic catalyst, oxygen vacancy concentration, surface basicity, and reducibility of CaO-based DFMs. The desired Mn@CaO DFMs exhibit outstanding CaL-RWGS performance at 650 °C, 15%CO 2 and 50%H 2 , with a great CO 2 uptake (12.30 mmol CO 2 /g), a favorable CO yield (5.92 mmol CO/g), and an impressive CO 2 conversion (53.53%), as well as a high CO selectivity (89.98%). Furthermore, Mn@CaO exhibits excellent carbonation and regeneration kinetics but inferior working stability for CO 2 capture and CO production in multiple CaL-RWGS cycles. Overall, Mn could be a competitive and cost-effective catalyst candidate for high-performance CaO-based DFMs for CaL-RWGS applications, while further work is needed to improve cyclic stability. [ABSTRACT FROM AUTHOR]

Ni–CaO–CeO 2 dual function materials prepared by sol–gel methods for efficient integrated CO 2 capture and reversed water gas shift reaction for syngas production. [Display omitted] • NiCaCe DFMs were prepared by different methods for integrated CO 2 capture and conversion. • Sol-gel method endowed the NiCaCe DFMs with better physicochemical properties. • The NiCaCe-SG (A) prepared by sol–gel method exhibited excellent ICCU-RWGS performance. • The DFMs prepared using acetate precursors showed better ICCU-RWGS performance. • Granulation adversely affected the physicochemical properties and ICCU-RWGS performance. Integrated CO 2 capture with reverse water gas shift (RWGS) reaction to produce syngas represents a promising technology to realize C1 recycling and utilization. Designing highly efficient Ni–CaO dual function materials (DFMs) is the key to achieve integrated CO 2 capture and utilization (ICCU). In this work, Ni–CaO–CeO 2 DFMs powders and pellets are prepared by the wet mixing, coprecipitation and sol–gel methods using acetate and nitrate precursors. Physicochemical properties and ICCU performance of the Ni–CaO–CeO 2 DFMs depend on synthetic mode, precursor, and granulation process. NiCaCe-SG (A) and NiCaCe-SG (N) prepared by sol–gel method show excellent ICCU-RWGS performance due to the developed pore structures, enhanced surface basicity, uniform Ni dispersion, minimized Ni grain size, abundant oxygen vacancies and reinforced reducibility. The NiCaCe-SG (A) sample prepared using acetate salts as precursors exhibits better ICCU-RWGS performance than the nitrate precursors-derived NiCaCe–SG (N) DFMs. Granulation adversely affects the CO 2 capture capacity, CO yield and working stability of the NiCaCe–SG (N) sample due to declined textural properties, weakened surface basicity and reducibility. NiCaCe–SG (A) represents an excellent DFMs candidate for ICCU-RWGS with high CO 2 uptake and conversion rate of 15.34 mmol CO 2 /g and 92.4 %, great CO yield and CO selectivity of 5.97 mmol CO/g and 89.1 %, and good working stability (a low decay rate of 11.6 % in 10 cycles). These results have provided new insights into the rational design of high-performance DFMs for ICCU applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Al-stabilized CaO-based sorbents produced by impregnated layer solution combustion. • Ca 12 Al 14 O 33 grains provide an effective inert framework for the synthetic sorbents. • Graphite-moulding method can prepare highly efficient CaO-based sorbent pellets. • Al-stabilized CaO-based sorbent pellets exhibit desirable property for CO 2 capture. Calcium looping (CaL) process is recognized as one of the most promising CO 2 capture technologies. However, the CaO-based sorbents commonly encounter serious sintering and elutriation problem during CO 2 capture cycles. In this work, Al-stabilized, CaO-based sorbents were synthesized by the impregnated layer solution combustion method, and cigarette butt was selected as the porous reactive skeleton. The Al-stabilized, CaO-based sorbent containing 15 wt% of Al 2 O 3 exhibits the highly stable CO 2 capture performance, whose CO 2 capture capacity after 20 cycles is almost the same as its initial capacity, ∼0.354 g/g. It is mainly attributed to the synergistic effect of thermal pretreatment (cigarette butt-assisted combustion) and incorporation of Al-based stabilizer (i.e., Ca 12 Al 14 O 33) provide a stable inert framework for the synthetic sorbents, ensuring their highly stable capability for CO 2 sorption during cycles. Further, graphite-moulding is a facile and energy-saving approach to make Al-stabilized, CaO-based sorbent powders into pellets to enhance its resistance to elutriation. The produced sorbent pellets (85 wt% CaO/15 wt% Al 2 O 3) exhibit excellent long-term CO 2 capture capacity (∼0.248 g/g after 49 cycles) and high compression strength of 18.47 ± 3.47 MPa. Therefore, the combined method involved of impregnated layer solution combustion and graphite-moulding is promising to produce highly efficient CaO-based CO 2 sorbent pellets used in CaL. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct solar-driven CaL can eliminate the adverse influence of coal combustion. • Dolomite-derived sorbents synthesized by cigarette butt-assisted combustion method. • Unitary or binary doping of optical absorption enhanced elements boosts solar absorbance. Calcium looping (CaL) is a promising technology for CO 2 capture owing to the widespread applicability and low-cost CaO-based sorbents. However, the SO 2 and ash from coal combustion in O 2 /CO 2 atmosphere for CaO regeneration is prone to cause rapid degradation for CaO-based sorbent. Hereby, a direct solar-driven CaL system is proposed to eliminate the adverse influence of coal combustion on CaO-based sorbent. Different unitary Mn-doped and binary-doped (Mn/Fe-, Mn/Cu- and Mn/Co-doped) dolomite-derived sorbents were synthesized by cigarette butt-assisted combustion method. The higher Mn doping ratio, the higher solar absorptance for unitary Mn-doped sorbent due to the gradually deepened blackness of the sample. Comprehensively considering the solar absorptance and CO 2 capture performance, the unitary Mn-doped sorbent (Ca&Mg: Mn=100:10) is an optimal candidate, which has a solar absorptance of 63.6 % and a carbonation conversion of 64.3 % in the 20th cycle. Compared with the unitary Mn-doped sorbent (Ca&Mg: Mn=100:10), the binary-doped sorbent (Ca&Mg: Mn: Fe=100:5:5) exhibits a comparable CO 2 capture capacity and a higher solar absorptance of 76.7 %. More importantly, the binary-doped sorbent (Ca&Mg: Mn: Fe=100:5:5) possesses the markedly faster CO 2 capture rate in the early carbonation stage due to the increased lattice defect of CaO. [ABSTRACT FROM AUTHOR]

Transition metal oxides doping improves the integrated CO 2 capture and conversion performance of Ni-CaO dual function materials. [Display omitted] • Ni-CaO DFMs are doped with transition metal oxides for improved integrated CO 2 capture and conversion performance. • ZrO 2 doping improves surface basicity and reducibility for enhanced CO 2 uptakes and catalytic activity. • ZrO 2 doping improves working stability by forming CaZrO 3 physical barrier to retard CaO and NiO sintering and agglomeration. • Doping ZrO 2 -CeO 2 boosts oxygen vacancy concentration for promoted CO 2 activation and conversion and stabilized CO yield. Transition metal oxides (TMOs) doping is proposed as one effective strategy to improve CO 2 capture and conversion performance of Ni-CaO dual function materials (DFMs). The effect of single and binary TMOs doping on structure–property-activity relationships of Ni-CaO DFMs for integrated CO 2 capture and in-situ reverse water gas shift (RWGS) is investigated. ZrO 2 doping enhances the surface basicity and reducibility of Ni-CaO DFMs for improved CO 2 uptakes and reinforced catalytic activity. ZrO 2 doping also endows Ni-CaO DFMs with improved working stability by forming CaZrO 3 solid solution, which acts as physical barrier to retard the agglomeration and sintering of CaO and NiO species. Doping binary metal oxides of ZrO 2 -CeO 2 further boosts the oxygen vacancy concentration in the DFMs for promoted CO 2 activation and conversion and stabilized CO yield. The desired Ni-CaO-6ZrO 2 -6CeO 2 DFMs shows a higher CO 2 conversion of 72.1% and a lower decay rate of 12.0% for CO yield in consecutive cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Orthogonal experiments were conducted to prepare sawdust-derived porous carbons. • Granulation destroys original porous structure of sawdust-derived porous carbons. • Sawdust-derived porous carbon extrudates are inferior to powders for CO 2 adsorption. • Sawdust-derived porous carbon extrudates possess good mechanical property. Sawdust wastes were used as the low-cost feedstock to prepare porous carbons by KOH activation, and the preparation parameters were optimized via orthogonal experiment. Four main activation parameters (i.e., sawdust type, KOH/sawdust ratio, activation temperature and activation time) were investigated. It is found that activation temperature and KOH/sawdust ratio are the two most important parameters that affect the porous texture properties (specific surface area and micropore volume) of sawdust wastes-derived porous carbons. The optimal sawdust wastes-derived porous carbon possesses a high specific surface area of 1601 m2/g and a micropore volume of 0.75 cm3/g, therefore exhibiting a desirable CO 2 adsorption capacity of 4.25 mmol/g at 0 °C under ambient pressure. Comparatively, the sawdust wastes-derived porous carbon extrudates exhibit the inferior CO 2 adsorption capacity, dropping to 2.85–3.03 mmol/g. It is mainly attributed to the extrusion treatment and binder addition causing the collapse and blockage of the original porous structure, consequently increasing the CO 2 diffusion and adsorption resistance. However, the sawdust wastes-derived porous carbon extrudates possess the advantages of null pressure build-up, improved bulk density and high compress strength (7.3–12.3 MPa) considering the real application point of view. [ABSTRACT FROM AUTHOR]