This work investigated the self-activation behavior of large K2CO3-doped Li4SiO4 sorbent particles. In this self-activation mechanism, the sorption ability increased as the number of cycles increased. After the sorption–desorption cycles occurred, the sorption ability of the K2CO3-doped Li4SiO4 sorbent was remarkably enhanced from approximately 2.0 mmol CO2/g sorbent to approximately 5.0 mmol CO2/g sorbent at 565 °C in 10 vol % CO2 atmosphere. The fresh and used sorbents were then characterized through N2 adsorption and SEM methods. Results showed that the average pore size increased from 7 to 32 nm and the surface microstructure changed from dense to porous, because the molten eutectic mixture formed by Li2CO3 and Li2SiO3 can facilitate CO2 diffusion. The formed CO2 diffusion channel can provide more CO2 accessibility; this channel can also reduce the CO2 diffusion resistance through the product layer. Therefore, the sorption ability of the sorbent is enhanced. Meanwhile, the effects of the self-activation temperature were also investigated and the results revealed that the optimal self-activation temperature is 615 °C. Furthermore, under critical conditions, the self-activated sorbent performed more efficiently than the fresh sample. At 450 °C under 10 vol % CO2 atmosphere, the sorption capacity of the self-activated sorbent was approximately 20 times higher than that of the fresh sample. Finally, a pore–core model was also proposed to illustrate the K2CO3-doped Li4SiO4 self-activation mechanism.

•A novel sorbent was evaluated under the steam and low CO2 concentration conditions.•Different sorbent-catalyst coupling methods were discussed in SE-SMR system.•High-purity H2 and low CO concentration can be obtained at low temperatures.•A reasonable sorbent regeneration strategy was proposed to simplify the process.•Steam increased the sorbent regeneration rate and can keep the system stable.A homemade K2CO3-doped Li4SiO4 sorbent was applied into the sorption-enhanced steam methane reforming (SE-SMR) system. Both the activated K2CO3-doped Li4SiO4 sorbent and the Ni/γ-Al2O3 catalyst showed good activity and stability. The result shows that the application of the activated K2CO3-doped Li4SiO4 sorbent into SMR system can remarkably enhance the process. High-purity hydrogen (H2 yield >95%) was obtained at relatively low temperatures (500–550 °C), which was 100–150 °C lower than that of using the calcium-based sorbents. Furthermore, the effects of different absorbent-catalyst coupling methods and particle sizes on the reactant diffusion were also discussed, finding that in-situ enhancement and moderate particle sizes (20–40 mesh) were beneficial for the reaction system. Finally, a reasonable sorbent regeneration strategy was proposed. It is found that steam enhances the regeneration rate of sorbent and has little negative effects on the activity of sorbent and catalyst, which makes it possible to obtain high-purity CO2 directly and simplify the subsequent separation process for the sorption-desorption operation design.

•A novel structured Cu-based anodic γ-Al2O3/Al catalyst was applied for DME SR.•The self-reduction mechanism of fresh Cu/γ-Al2O3/Al catalyst was analyzed.•The mechanism of Ni doping on the structure evolution of Cu/γ-Al2O3 was evaluated.•The addition of nickel can improve the thermal stability of Cu-based catalyst.A plate-type anodic alumina supported Cu composition catalyst was developed to investigate its catalytic performance in steam reforming of dimethyl ether (DME). It is found that the fresh Cu/γ-Al2O3/Al catalyst without H2 pre-reduction treatment exhibited the similar catalytic activity as the pre-reduced one. The XPS results show that Cu+ species exist in the surface of the fresh catalyst, which results in the self-activation reaction. However, the Cu/γ-Al2O3/Al catalyst showed a quick deactivation at 350 °C due to the sintering of copper. As an approach, a second component Ni was doped to the Cu-based catalyst, and a series of Cu/Ni/γ-Al2O3/Al catalysts with different Ni loadings were prepared by impregnation method. Furthermore, the effect of nickel loading and chemical state on the activity of catalyst was extensively investigated. The results show that the catalytic performance was related to both of the nickel loading and chemical state. The proper amount of nickel doping is helpful in improving the dispersion of copper species, and thus enhancing the catalytic activity. Finally, a 180 h stability evaluation was carried out and the results show that the optimized Cu/Ni/γ-Al2O3/Al catalyst has an excellent stability under critical conditions with 400 °C, and gives a 100% DME conversion, which demonstrated that the novel γ-Al2O3/Al monolith supported Cu and Ni composite catalyst was an excellent catalyst for steam reforming of dimethyl ether.

A novel fluidizable K-doped HAc-Li4SiO4 sorbent using an incipient impregnation method was prepared in this work. The produced sorbent displayed an excellent CO2 sorption capacity and stability under expected reaction conditions. Glacial acetic acid treatment was first used to modify the Li4SiO4 sorbent microstructure. Following this step, an incipient impregnation method was applied to dope potassium onto the sorbent in order to further enhance the sorbent sorption capacity. This novel K-doped HAc-Li4SiO4 sorbent was characterized using X-ray diffraction, N2 adsorption–desorption, CO2 temperature-programmed carbonation (CO2-TPC), and CO2 temperature-programmed decarbonation (CO2-TPDC) analyses. The experimental results showed that the CO2 sorption capacity of the K-doped HAc-Li4SiO4 sorbent is approximately 100 cm3 STP CO2/g sorbent. This was five times that of the Li4SiO4 sorbent. Furthermore, the cyclic test of the K-doped HAc-Li4SiO4 sorbent demonstrated it to be high and stable for CO2 capture.

•A novel anodic alumina monolith supported Cu catalyst was applied for DME SR.•The degradation behaviors of Cu/γ-Al2O3/Al catalyst were systematically studied.•The selectivity of CO is found to be very sensitive to the copper grain size.•A novel pre-competition impregnation method can improve the catalyst activity.A novel plate type anodic alumina supported Cu composite catalyst was developed to catalyze dimethyl ether steam reforming (DME SR) for hydrogen production. The degradation behaviors of the Cu/γ-Al2O3/Al catalyst during DME SR were systematically studied. It is demonstrated that the catalyst was subjected to deactivation above 350 °C mainly due to the copper sintering. The selectivity of by-product CO is found to be very sensitive to the copper grain size. The aggregation of copper resulting in bigger copper grains will favor the reverse water gas shift reaction (r-WGS), which can be an efficient indicator to monitor the catalyst sintering process. A novel pre-competitive impregnation method was used to improve the composite catalyst. The catalyst's BET surface was significantly increased and the metal dispersion was improved via this method. The catalyst exhibited high activity and stability in DME SR even above 375 °C. A mechanism of this competitive impregnation was also proposed.

•Pure Li4SiO4 sorbent exhibits low capacity at low CO2 concentrations.•K-doped Li4SiO4 exhibits much higher absorption capacity.•The best sorbent can be achieved by maximized KLi(CO3) and minimum Li2SiO3.•The optimized sorbent have good stability.Potassium carbonate was used as a doping agent to improve the absorption properties of Li4SiO4 for CO2 capture during critical sorption-enhanced steam methane reforming (SESMR) under moderate temperature and low CO2 concentration with moisture.The mechanism of CO2 absorption onto pure and K-doped Li4SiO4 under various CO2 concentrations was experimentally and theoretically studied. At 575 °C, pure Li4SiO4 exhibited poor CO2 absorption capacity because of low CO2 diffusion through the solid Li2CO3 shell of the sorbent. By contrast, the K-doped Li4SiO4 sorbent showed excellent performance. K2CO3 and Li2CO3 can form eutectic compounds that facilitate the diffusion of CO2 into the sorbent crystals and enhance the absorption of CO2. The amount of doping agent was further optimized under different operating conditions and numerical analysis. Absorption–desorption cycles were performed under industrial operating conditions and the optimized K-doped Li4SiO4 exhibited satisfactory absorption capacity and stability.

•A novel plate anodic γ-Al2O3 monolith catalyst was applied for DME reforming.•The monolith showed higher DME hydrolysis activity than the commercial γ-Al2O3.•Mechanisms of Cu loading under different impregnation conditions were proposed.•Effects of CuO crystallite size and Cu loading on DME SR were investigated.•The composites of the anodic γ-Al2O3 and Cu exhibited good synergy in DME SR.A novel porous alumina monolithic material was prepared through the anodization technology, and its catalytic performance for hydrolysis of dimethyl ether (DME) was investigated. The anodic γ-Al2O3 exhibited higher catalytic activity due to its stronger acidity, better hydrophilicity and lower activation energy than the commercial γ-Al2O3 and also showed good stability in a 110 h test. Meanwhile, a series of Cu/anodic γ-Al2O3 catalysts were prepared by impregnation method, and the mechanism of Cu loading was studied. Furthermore, the effect of Cu loading and CuO crystallite size on the activity of catalyst for DME steam reforming was investigated. The experimental results show that the conversion of DME was related to both of the Cu loading and the CuO crystallite size, while the selectivity of CO was very sensitive to the latter. In addition, the synergetic effects of different catalysts on DME steam reforming reaction system were also discussed.