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[Display omitted] • 1-dimethylamino-2-propanol/ N -(2-hydroxyethyl) ethylenediamine is biphasic solvent. • The solvent-rich phase is 66.67 % and the CO 2 loading can be up to 5.07 mol/L. • Biphasic solvents have a desorption rate 106.7% higher than conventional MEA. • The regeneration efficiency of the biphasic system as high as 71.8% in 60 min. • The regeneration heat is 54.1 % lower than conventional 5 mol/L MEA. Biphasic solvents are widely used for CO 2 capture owing to their low regeneration heats; however, they typically suffer from poor regeneration performance and excessive energy consumption. In this study, a mixture of 1-dimethylamino-2-propanol (1DMA2P) and N -(2-hydroxyethyl) ethylenediamine (AEEA) was proposed for CO 2 capture. By optimizing the 1DMA2P and AEEA concentrations, this biphasic solvent achieved superior phase separation and excellent absorption and regeneration performance. The proportion of CO 2 -rich phase was 66.67 %, with a CO 2 -rich phase loading of up to 5.07 mol/L. The desorption rate was improved by 106.7 % compared to that of conventional 5 mol/L monoethanolamine, and the regeneration efficiency up to 71.8 % in 60 min. Initially, CO 2 reacted with AEEA at a faster rate to form a carbamate product. Subsequently, 1DMA2P acted as a proton acceptor, facilitating the formation of bicarbonates and carbonates. Nuclear magnetic resonance analysis indicated that the reaction products (AEEACOO-, AEEAH+, and HCO 3 –/CO 3 2–) migrated to one phase, whereas 1DMA2P and any unreacted AEEA migrated to the other phase. Additionally, the disparity in polarity between the reactants and reaction products constituted the primary determinant for the phase transition. Notably, the regeneration heat of the 1DMA2P/AEEA biphasic solvent (1.83 GJ/t CO 2) was approximately 54.1 % lower than that of conventional 5 mol/L monoethanolamine. Owing to its superior absorption properties, excellent regeneration performance, and low regeneration heat, the 1DMA2P/AEEA biphasic solvent is a promising candidate for practical CO 2 capture systems. [ABSTRACT FROM AUTHOR]

One of the key points in the development of dry reforming of methane (DRM) is the design of catalysts with high activity and stability. The reactivity and carbon deposition properties of La 2 NiO 4 in DRM, as well as its regeneration performance, were studied. The results showed that the in-situ decomposition of La 2 NiO 4 led to a more uniform distribution of smaller Ni0 particles on the La 2 O 3 matrix compared with the directly loaded NiO/La 2 O 3. A temperature-programmed test revealed that the breakthrough curve temperature for La 2 NiO 4 in DRM was 618 °C. The carbon deposition would carry Ni0 metal away from the La 2 O 3 matrix, making the solid carbon unable to be removed promptly due to insufficient oxygen supply, resulting in an increase in the catalyst's instantaneous carbon deposition rate at 650 °C and 750 °C. The regeneration tests showed that the samples' DRM performance and carbon deposition levels remained relatively stable before and after steam regeneration. However, air-regenerated samples exhibited a hysteresis time in DRM due to sintering. Additionally, CO 2 was unable to completely remove carbon deposition from the samples, resulting in a significant increase in carbon deposition when regenerated samples were used for DRM. • La 2 NiO 4 could maintain high reactivity in DRM for its ability of obtaining finely dispersed Ni0 metal on the La 2 O 3 carrier. • There was a breakthrough curve temperature (618 °C) for La 2 NiO 4 in the DRM atmosphere. • The instantaneous carbon deposition rate of La 2 NiO 4 samples increased over time at 650 and 750 °C for DRM. • The steam was the most effective regeneration atmosphere to regenerate La 2 NiO 4 after the DRM reaction, followed by air and finally CO 2. [ABSTRACT FROM AUTHOR]

• An improved quasi-cycle capacity screening method was proposed in this work. • Guidelines about the effective screening of solvents based on two parameters. • The CO 2 quasi-cyclic capacity was used to evaluate the reaction rate. • The CO 2 absorption heat of six amino acid salts was first accurately measured. • The sensible heat of different absorbent solutions was directly measured. Reaction rate and energy consumption are important factors that determine whether the chemical absorbent is suitable for capturing carbon dioxide (CO 2). In this work, a high-precision microcalorimetry instead of the traditional estimation method based on the Gibbs-Helmholtz equation was used to directly measure the CO 2 absorption heat of six amino acid salt absorbents (potassium taurinate (PT), potassium sarcosinate (PS), potassium L-Prolinate (PL-P), potassium β-Alaninate (Pβ-A), potassium L-Threonine (PL-T), and potassium glycinate (PG)) and the sensible heat of their solutions. In addition, the absorption rate, desorption rate, absorption time, desorption time, and CO 2 loading of the absorbents were studied and were integrated into a parameter called the CO 2 quasi-cycle capacity to evaluate the reaction rate. Based on thermodynamic data and CO 2 quasi-cycle capacity, the absorbent screening method was improved in this work, and PS was identified as a promising absorbent by this method. The CO 2 quasi-cycle capacity of the PS solution was similar to that of MEA. In addition, PS solution has the lowest CO 2 absorption heat (-75.79 kJ/mol CO 2) and the lowest sensible heat which were 14.1% and 23.2% lower than those of MEA solution. [ABSTRACT FROM AUTHOR]

• A two-step reaction mechanism of Hg with NO 2 was studied theoretically. • The calculated third-order rate constant agrees with the experimental value. • The effect of pressure on the reaction kinetics was investigated using RRKM. • The life time of Hg is highly dependent on NO 2 concentration. Reaction of Hg and NO 2 significantly contributes to mercury removal in CO 2 compression and purification unit. However, the reaction mechanism remains unclear and the product species is difficult to collect and identify experimentally. To gain insight into this reaction, we studied it using quantum chemical and kinetic calculations. A two-step reaction mechanism of Hg and NO 2 was investigated. Initially, Hg could react with NO 2 without a barrier to form two isomeric HgNO 2 complexes (i.e. HgO 2 N and HgNO 2) that achieve equilibrium very quickly. Then both HgNO 2 isomers can add another NO 2 to form a variety of HgN 2 O 4 compounds, among which the most stable is trans-syn, syn -Hg(ONO) 2. Kinetics were investigated using variational transition state theory (VTST) and RRKM theory to calculate the rate constants with respect to both temperature and pressure. The only effective reaction pathway is the one described above leading to trans-syn, syn- Hg(ONO) 2. The temperature- and pressure-dependent rate constants of these relevant reactions were presented. The calculated third-order rate constant is 7.4 × 10-35 cm6 molecule-2 s−1 at 298 K and 1 atm, which is of the same order of magnitude as the experimental value. This reaction pathway shows a negative temperature dependence from 250 to 400 K, which is in accordance with the existing experimental results. The gas phase reaction mechanism of Hg with NO 2 could well explain the observations in the transformation of mercury in the CO 2 compression and purification unit. [ABSTRACT FROM AUTHOR]

[Display omitted] • CeO 2 @Cu catalysts were prepared with cerium salt via a solution auto-combustion method. • CeO 2 @Cu-A exhibited best CO production rate 1.64 mol/g cat.h at 400 °C. • CO 2 hydrogenation performance was enhanced by oxygen vacancy on CeO 2 @Cu catalyst. • CuO x unreduced on CeO 2 @Cu-C limited CO 2 conversion and increased CH 4 selectivity. Cu-based catalysts had been widely used in CO 2 hydrogenation process for their excellent performance and high selectivity. Micron-sized Cu powder obtained by ball milling exhibited poor CO 2 activity for its large particle size and small specific surface area, limited its catalytic application. In this work, micron Cu powder was modified with CeO 2 species synthesized from different cerium precursor salts via a solution auto-combustion method to investigate CO 2 hydrogenation activity. This work revealed that CeO 2 species formed from cerium acetate precursor salt achieved excellent CO 2 performance (1.64 mol/g cat.h at 400 °C), which was 3.8 times and 6000 times higher than that from cerium nitrate salt or cerium chloride salt, respectively. Interestingly, a thick dense CeO 2 shell would be formed on micron Cu generated from cerium(III) chloride precursor salt, which inhibited CuO x reduction and had the opposite effect for RWGS reaction. In addition, the CuO x species in CeO 2 @Cu synthesized from cerium chloride salt resulted in the CH 4 selectivity. The enhancement performance of the CeO 2 @Cu prepared from cerium acetate salt and cerium nitrate salt could be attributed to the oxygen defects formed around the Cu-Ox-Ce interface area and metallic Cu in the RWGS reaction. Cerium precursor salts enhanced the structural integrity of CeO 2 @Cu and played a vital role in RWGS reaction. These results will support a new direction for exploring micron Cu powder in Cu-based catalysts for CO 2 utilization. [ABSTRACT FROM AUTHOR]

• Screening and evaluation of amine/alcohol/H 2 O absorbents were conducted. • The difference of ΔGsol in alcohol and in water confirms phase change behavior. • Alcohol could not only trigger phase change but also facilitate CO 2 absorption. Phase change absorbents have recently drawn increasing attention due to the potential of for low energy-consuming CO 2 capture. When forming two phases after CO 2 absorption, only the CO 2 -rich phase is heated in the desorption process thus reducing the sensible heat. In this work, five amine and three alcohol blends were used to investigate their phase change behavior after reacting with CO 2. Phase separation could easily occur for DETA/alcohol/water combinations after CO 2 absorption, which was confirmed by the large difference of the solvation free energy in alcohol and in water (i.e. DETA-CO 2 has 12.5 kcal/mol ΔGsol in 1-propanol less than that in water). The optimization of the DETA/1-propanol/H 2 O solution was confirmed to be 30% DETA + 30% 1-propanol + 40% H 2 O (D30P30H40). It was found that above 90% of CO 2 loading was enriched in lower phase. 13C NMR spectrum indicated that carbamate and bicarbonate was formed in lower phase and 1-propanol acted as a good physical solvent to trigger phase separation and facilitate the reaction between amine and CO 2. [ABSTRACT FROM AUTHOR]

• An increase in the proportion "-NH-" functional groups causes lower ΔH abs. • Secondary amino functional groups appear to stimulate the growth of Δα CO2. • 2MPZR has a 10.7% lower ΔH abs than MEA. • The effective phase change solvent, 2MPRZ/TGBE/H 2 O, was proposed in this work. • The sensible heat of 2MPRZ/TGBE/H 2 O is 56 % lower than that of 5 M MEA. Energy consumption is one of the crucial factors in determining the suitability of the chemical absorbents for capturing carbon dioxide (CO 2). Polyamines have attracted increasing attention in recent years because of the existence of several amino functional groups that could effectively capture CO 2 in their molecules. In this work, the structures of seven polyamines with excellent CO 2 capture performance were investigated in relation to reaction rate and the CO 2 absorption heat. A high-precision microcalorimeter was applied to analyze the absorption heat of CO 2 directly, and a parameter defined as the CO 2 quasi-cycle capacity was employed to assess the cyclic capture capacity of CO 2 , absorption rate, and desorption rate. Experimental results revealed that for the selected polyamines, the increase in the ratio of the secondary amino functional group to the primary-one in the molecule leads to a decrease in the CO 2 absorption heat and an increase in the CO 2 cyclic capacity.The ΔH abs of the eight amines give out the order of HMDA (92.22 kJ/mol) > MAPA(90.91 kJ/mol) > AEEA (87.62 kJ/mol) > MEA (86.36 kJ/mol) > TEPA (82.95 k/mol) > AEP (82.36 kJ/mol) > 2MPRZ (77.08 kJ/mol) > PZ (74.41 kJ/mol). The CO 2 quasi-cycle capacity of 2MPZR is about twice that of the MEA. In addition, 2MPRZ was found to be an absorbent with phase change potential. The effective phase change solvent system, 2MPRZ + Triethylene glycol monobutyl ether (TGBE) + H 2 O, was developed in this work. Compared to the 5 M MEA aqueous solution, its sensible heat was reduced by 56.3 %, indicating that 2MPRZ is a promising absorbent. [ABSTRACT FROM AUTHOR]

• Three possible pathways for bicarbonate generation were investigated based on DFT. • Base-catalyzed CO 2 hydration is dominant in [N 1111 ][Gly]/EtOH aqueous system. • Water effect on phase change behavior is analyzed from hydrogen bonding view. • Water content of 5 wt% promotes products aggregation in favor of phase change. Ionic liquids-based anhydrous biphasic absorbents have the potential to lower the energy consumption for CO 2 capture. Recent experimental studies have revealed that the presence of water in [N 1111 ][Gly]/EtOH system leads to generation of a new CO 2 -product – bicarbonate and affects the phase change behavior. However, the reaction pathway for bicarbonate formation remains unclear. In this work, the reaction pathways were investigated in depth through quantum chemical calculations employing density functional theory, with reaction rate constants determined via transition state theory. Among the three possible reaction pathways, the base-catalyzed CO 2 hydration reaction prevailed, i.e. a one-step reaction involving [Gly]-, H 2 O, and CO 2. An H atom in H 2 O was transferred to [Gly]-'s amino group, forming protonated [Gly]-, and hydroxide combined with CO 2 to generate bicarbonate. Additionally, molecular dynamics simulations were conducted to understand the phase change behaviors with varying water content. When water content exceeded 5 wt%, an increased water content led to reduced hydrogen bonding among products and enhanced hydrogen bonding of products-solvent with the solvent, diminishing product self-aggregation. No phase change behavior were observed at water contents up to 80 wt%. This study could well explain the experimental phenomena of water effect on CO 2 absorption in [N 1111 ][Gly]/EtOH, providing theoretical references for application of ILs-based anhydrous biphasic absorbent. [ABSTRACT FROM AUTHOR]

• Revealing the chemical effects of CO 2 and H 2 O on homogeneous fuel-NO mechanism. • CO 2 favors the establishment of MILD regime by reducing the overall oxidation rate. • NO formation is both enhanced with the increasing contents of CO 2 and H 2 O. • CO 2 addition mainly facilitates the generation of NO via HNO as the intermediate. • Increasing H 2 O level evidently strengthens the route NH 3 → NH 2 → NH → N → NO. MILD-oxy combustion is an advanced technology for achieving carbon capture and low NO x emissions simultaneously. In its combustion process, the atmosphere comprises CO 2 and H 2 O due to intense flue gas recirculation. This work numerically investigates the chemical effects of co-flow CO 2 and H 2 O on the homogeneous fuel-NO formation mechanism of CH 4 /NH 3 jet flames in hot co-flow under MILD-oxy condition. The results reveal that compared with H 2 O dilution, CO 2 dilution alters the radical pool and thus lowers the overall oxidation rate, which favors achieving the MILD regime with a notably enlarged reaction zone. The increase in CO 2 and H 2 O contents facilitates the formation of NO, wherein NH 3 conversion into NO primarily occurs via four routes with HNO as the major N-containing intermediate. The addition of CO 2 significantly promotes NH 2 + O ↔ HNO + H and NH + CO 2 ↔ HNO + CO , which enhances the oxidation of NH 3 through the routes NH 3 → NH 2 → HNO → NO and NH 3 → NH 2 → NH → HNO → NO. The enhancement of H 2 O concentration accelerates NH + OH ↔ HNO + H and NH + OH ↔ N + H 2 O through the formation of abundant OH radical. The conversion of NH radical to HNO and N radical is consequently facilitated and strengthens the routes NH 3 → NH 2 → NH → HNO → NO and NH 3 → NH 2 → NH → N → NO. [ABSTRACT FROM AUTHOR]

• Novel biphasic solvent based on polyamine was developed for CO 2 capture. • Microcalorimetry strategy was used to directly measure the CO 2 absorption heat. • The energy consumption of this absorbent was 32.6 % lower than that of 5 M MEA. • This biphasic solvent has superior phase-splitting behavior. • The salting-out effect was the main reason for the phase-splitting behavior. The CO 2 phase change absorbents(CPCAs) formed by introducing phase-splitting agents have attracted increasing attention because of their great energy-saving potential. However, the volatilization problem of the phase-splitting agents and the high viscosity of the solution affect the application of CPCAs. In this work, a novel CPCAs based on 2-Methylpiperazine (2MPRZ)/H 2 O was established by introducing triethylene glycol monobutyl ether (TGBE) with a high boiling point as a phase-splitting agent, and the 2MPRZ/H 2 O/TGBE system exhibited low volatility and low viscosity. The CO 2 capture performance of the novel CPCAs with different ratios was investigated in this work. The best CO 2 absorption rate was achieved by 2.5 M 2MPRZ/H 2 O/TGBE. The viscosity of this system before and after the CO 2 absorption process was merely 7.68 mPa·s and 11.64 mPa·s, respectively, and no volatilization of the phase-splitting agent was observed simultaneously. A convenient and rapid titration method was employed to determine the distribution of the 2MPRZ products in the two phases, which showed that 98 % of the 2MPRZ products were located in the CO 2 -rich phase. In addition, the CO 2 -rich phase captured 99 % of the total CO 2 , indicating that this system has superior phase-splitting behaviors. The regeneration energy consumption of this biphasic absorbent was 2.59 GJ/t CO 2 , which was 32.6 % lower than that of traditional MEA. Furthermore, the salting-out effect was proved to be the cause of the phase-splitting behavior by 13C NMR analysis. [ABSTRACT FROM AUTHOR]

• The individual and combined impacts of physical and chemical effects are differentiated. • CO 2 -dilution better maintains the homogeneous MILD reaction regime by its physical effect. • Heterogeneous reaction tends to be kinetics-controlled under both CO 2 - and H 2 O-dilutions. • The physical effect weakens gasification reaction while the chemical effect greatly promotes it. • H 2 O-dilution shows greater potential in lowering NO emission than CO 2 -dilution. In pulverized coal MILD-oxy combustion process, the oxidizer diluents are switched from N 2 to CO 2 and H 2 O. Hence, the remarkable discrepancies in combustion characteristics directly originate from the differences in physical and chemical properties of diluents, namely, the physical and chemical effects. This work utilizes the fictious materials, i.e., FCO 2 and FH 2 O, which have the same physical properties with the real ones but are completely non-reactive, to isolate these two dilution effects. Their individual and combined impacts on the global reaction behaviors are numerically evaluated. Results reveal that the physical effect of CO 2 and H 2 O plays an important role in enhancing the internal flue gas recirculation. Compared with H 2 O-dilution, CO 2 -dilution better inhibits the temperature rise and promotes the in-furnace thermal uniformity, which predominantly originates from its physical effect. Hence, the MILD reaction regime with high temperature and strong dilution levels occur in a wider region. The homogeneous diffusion/kinetics-controlled regime (0.2 < Da t < 2) is more susceptible to the chemical effect of CO 2 and H 2 O. The kinetics-controlled regime of heterogeneous reaction is facilitated under CO 2 - and H 2 O-dilutions, where the physical effect is dominant in the former case while the physical and chemical effects act jointly in the latter case. The chemical effect of CO 2 and H 2 O is responsible for greatly strengthening gasification reaction by direct participating in the reaction process, which in turn slows down the burnout of char. Importantly, H 2 O-dilution shows greater potential to lower NO emission level than CO 2 -dilution. The physical effect is revealed to play a dominant role in reducing the global NO formation rate, while the chemical effect enhances the reburning of NO in a wide lean-O 2 reduction region. The findings of this work are expected to help gain a more comprehensive understanding in MILD-oxy combustion technology. [ABSTRACT FROM AUTHOR]

• Water markedly affected phase change behaviors of anhydrous biphasic absorbents. • The presence of water was negative for CO 2 absorption but beneficial to desorption. • The main CO 2 -product was HCO 3 - in the presence of water rather than carbamate. • Effect of water on CO 2 absorption mechanism of [N 1111 ][Gly]/ethanol was clarified. The ionic liquids (ILs)-based biphasic absorbents are viewed as promising substitutes for CO 2 capture due to their remarkable CO 2 absorption performance, excellent stability and low energy requirement for regeneration. Further decreasing the regeneration heat requirement can be achieved by utilizing ILs-based anhydrous biphasic absorbents, whose solid CO 2 -rich phase contained small volume and low specific heat capacity. Given the high hygroscopicity of ILs and the water present in the flue gas, comprehending the effect of water is crucial for post-combustion carbon capture using ILs-based anhydrous biphasic absorbents. In this work, the effect of water on CO 2 absorption by an anhydrous biphasic absorbent, tetramethylammonium glycinate ([N 1111 ][Gly])/ethanol, was studied. The experimental results demonstrated that the CO 2 loading and absorption rate were decreased in the presence of water, but the CO 2 desorption efficiency was enhanced. Besides, the presence of water slightly reduced the reaction heat of CO 2 absorption by [N 1111 ][Gly]/ethanol to 69.48 kJ/mol CO 2 , which was 20% lower than that of monoethanolamine (MEA) absorbent. Furthermore, the 13C NMR results indicated that the primary CO 2 -product was bicarbonate in the presence of water rather than carbamate. There were three possible pathways for bicarbonate generation: zwitterion hydrolysis, carbamate hydrolysis, and base-catalyzed CO 2 hydration. Water and ethanol competed to react with carbamate. When a large amount of water was present (≥70 wt%), the reaction of ethanol with the carbamate hardly occurred. [ABSTRACT FROM AUTHOR]

One of the research priorities in dry reforming of methane (DRM) technology is the development of highly active and stable catalysts. Using crystalline oxides as catalyst precursors is an effective catalyst optimization scheme for DRM. Therefore, the application of La 2 NiO 4 perovskite in DRM was systematically studied, including preparation, characterization, carbon deposition properties, regeneration properties, and B-site doping, etc. This paper is the first part, the effects of preparation methods (sol-gel, co-precipitation, hydro-thermal, and solid-state methods) on the physicochemical properties and DRM performance of La 2 NiO 4 samples were investigated, and the relationship between materials' structure and their catalytic performance was analyzed. The results showed that compared with the samples prepared by the hydro-thermal and co-precipitate methods, the sample prepared by the sol-gel method exhibited the highest conversion of CH 4 and CO 2 (91.4% and 91.5%, respectively) and the best carbon resistance in DRM, which were mainly attributed to its richer microstructure, higher reducibility and basicity. While the lowest DRM performance of the sample prepared by the solid-state method was mainly due to the small amount of reduced amorphous NiO and the weak reducibility of the perovskite phase in this sample, resulting in the inability of perovskite in-situ decomposition under the DRM atmosphere. • A series of La 2 NiO 4 perovskite oxides were synthesized by the sol-gel, co-precipitation, hydro-thermal, and solid-state methods for DRM. • The sample prepared by the sol-gel method (L2N-SG) exhibited the highest reactivity and the best carbon resistance in the DRM. • The best DRM catalytic activity and carbon resistance of L2N-SG were due to its rich microstructure, high reducibility, and high basicity. • The in-situ reduction process of perovskites in the DRM depends on the amount of reduced amorphous NiO and the reducibility of the perovskite phase in the material. [ABSTRACT FROM AUTHOR]

• Revealing the fuel-NO formation mechanism affected by CO 2 and H 2 O dilutions. • CO 2 dilution favors maintaining MILD combustion regime in an expanded reaction zone. • Free radical level is weakened by CO 2 while H 2 O boost the formation of OH radical. • The lowest overall NO emission is derived under MILD-H 2 O combustion. • H 2 O dilution enhances the N radical formation and inhibits HNO direct conversion into NO. MILD-oxy combustion operates conventional oxy-combustion processes under moderate or intense low-oxygen dilution (MILD) condition, which offers a practical approach towards the synergetic control of CO 2 and NO x emissions. This numerical work investigates the MILD combustion characteristics and NO emission of CH 4 /NH 3 fuel blend under N 2 , CO 2 and H 2 O dilutions, aiming at revealing the fuel-NO formation mechanism under MILD-oxy condition. It is found that relative to MILD-N 2 combustion, the flame temperature is reduced under MILD-CO 2 and MILD-H 2 O combustion, while the reaction zone is expanded and reduced, respectively, due to the altered co-flow properties. CO 2 dilution lowers the radical pool level, while the formation of OH radical is boosted under H 2 O dilution. Overall NO emission (EINO) under MILD-N 2 combustion is the largest while that under MILD-H 2 O generates the lowest value, showing its low-NO x emissions superiority. NH 3 is converted into NO via routes NH 3 → NH 2 → HNO → NO and NH 3 → NH 2 → NH → HNO → NO under MILD-CO 2 combustion. By contrast, the importance of route NH 3 → NH 2 → NH → N → NO in producing NO is largely strengthened under MILD-H 2 O combustion, wherein the direct formation of NO via HNO is inhibited with the enhanced availability of reactive N-containing species, contributing to lower NO emission under MILD-H 2 O combustion over MILD-CO 2 combustion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanostructured metal oxyhydroxide AlOOH was synthesized for catalytic CO 2 capture for the first time. • A simple but precise heat transfer model was created for heat duty assessment. • The use of AlOOH exhibited the best catalytic performance in increasing the CO 2 desorption rate and decreasing the energy consumption in comparison with other catalysts reported. • A thorough catalytic mechanism was proposed and preliminarily validated. In order to alleviate the intensive energy demand of amine-based post-combustion carbon capture technology, metal oxyhydroxide AlOOH of nanoscale was synthesized through the hydrothermal method and applied to accelerate the CO 2 desorption rate and reduce the regeneration heat duty of aqueous monoethanolamine (MEA) solution for the first time. Results showed that the use of AlOOH could accelerate the desorption rate by up to 560% and increase the desorption amount by 251%. By comparing the performance between AlOOH and Al 2 O 3 , it can be found that the presence of extra hydroxyl groups is 20.6% more efficient in catalyzing CO 2 desorption. According to a simplified heat transfer model created in this work, AlOOH could reduce the heat duty by 17% with only 0.1 wt% loading, which exhibited the highest performance cost ratio among related literature. In addition, the cyclic stability of AlOOH was confirmed through various characterization methods, including XRD, FT-IR, SEM, and N 2 adsorption–desorption. More importantly, a possible catalytic mechanism of AlOOH was discussed and proved where it could change reaction pathways in different CO 2 loading regions. This work reveals a promising research direction towards cost-efficient and high-performance metal oxyhydroxide catalysts in the catalytic amine regeneration field to approach the net-zero carbon emission goal. [ABSTRACT FROM AUTHOR]

Coal-direct chemical looping hydrogen generation (CDCLHG) is a novel process that uses coal to directly produce H 2 with inherent CO 2 capture. A key issue is to find out suitable oxygen carriers for this process. In this study, perovskite was proposed as the oxygen carrier for CDCLHG, and a series of Mn-based and Fe-based perovskite oxides were synthesized by a sol-gel method for CDCLHG reactions in a fixed-bed reactor. The results showed that BaMnO 3 was an optimal oxygen carrier for CDCLHG, which could obtain H 2 -rich gas (>85%) with a high H 2 gas production rate, about 13 times higher than that in char steam gasification. Further tests showed that the optimal reaction temperature and O/C ratio were 850 °C and 1: 0.05, respectively. XRD and XPS patterns indicated that part of the lattice oxygen in BaMnO 3 could convert to the carbonate oxygen in BaCO 3 during the fuel oxidation stage (FO stage) and obtained BaMnO 3-δ with plentiful oxygen vacancies in it. The BaMnO 3-δ could partially restore its lattice oxygen in the reduction of steam stage (RS stage) and completely recover its initial structure in the air calcining stage (AC stage). SEM images showed that the decrease of BaMnO 3 reaction performance after 9 cycles was mainly due to ash accumulation. • Perovskite is proposed as oxygen carrier for coal-direct chemical looping hydrogen generation. • BaMnO 3 showed good reactivity and stability in the CDCLHG reaction. • The reaction temperature, duration, and oxygen carrier to char ratio have great effect on CO 2 selectivity and H 2 purity. • Part of the lattice oxygen in BaMnO 3 could convert to the carbonate oxygen in BaCO 3 in FO stage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Severe thermal activation condition accelerated formation of a stable structure. • High temperature, long duration, low heating rate caused self-reactivation for CaO. • Sol-gel combustion synthesis is optimized to prepare the best CaO sorbents. • The pH value of precursor solution was the most influential factor. This work is the extension of part Ⅰ. The last procedure in the technical route of sol–gel combustion synthesis for CaO sorbents preparation, i.e. the thermal activation process was studied. The effects of the relevant preparation parameters including temperature, duration, and heating rate on the cyclic CO 2 sorption performance, micromorphology, pore size distribution, and physical parameters of the prepared pure CaO sorbents were investigated. Results were obtained that high temperature (>950 ℃), long duration (>1 h), and low heating rate (<2 ℃/min) in the thermal activation process accelerated the formation of a stable structure in CaO sorbents. Accordingly, the sorbent showed low initial conversion, an opposite increasing trend in the first several cycles, and high cyclic stability. The optimal thermal activation condition was 850 ℃ for 5 min without heating rate. Furthermore, by integrating the optimization results of the whole technical route, the optimal CaO sorbent was prepared, which showed excellent performance. With the cyclic condition of 10 minutes of carbonation at 650 ℃ under 15% volume CO 2 and 10 minutes of calcination at 850 ℃ under 100% volume N 2 , its carbonation conversion varied from 98.2% to 52.1% through 50 cycles. An average enhancement of 21.8% in 50 cycles was obtained compared to the sorbent before optimization and the average enhancement was 168.3% compared to CaCO 3. Moreover, the pH value of the precursor solution was the most influential factor among the preparation variables. [ABSTRACT FROM AUTHOR]

[Display omitted] • LN-CeO 2 catalyst was prepared via a freezing route with liquid nitrogen. • Na ion-doped in LN-CeO 2 promoted the formation of oxygen vacancy. • LN-CeO 2 -100 exhibited a CO production rate of 3.90 mol/g cat· h at 800 °C. • Oxygen vacancy was related to CO 2 hydrogenation performance of LN-CeO 2. CeO 2 -based catalysts have been widely used in the CO 2 hydrogenation process. The oxygen vacancies on CeO 2 resulted from Na ion incorporation play a vital role in CO 2 conversion activity, the effect of Na+ ion-doped in CeO 2 during CO 2 hydrogenation was rarely studied. In this work, the LN-CeO 2 catalysts with different n NaOH :n Ce ratios were prepared with liquid nitrogen(Liquid Nitrogen-CeO 2 , LN-CeO 2), and the effect of the n NaOH :n Ce ratio on the microstructure of the LN-CeO 2 catalysts were evaluated. The best CO 2 hydrogenation performance was achieved by LN-CeO 2 -100 with a CO production rate of 3.90 mol/g cat· h at 800 °C (100% CO selectivity). The kinetic results indicated that the CO 2 hydrogenation performance difference among these LN-CeO 2 catalysts resulted from the CO 2 activation process. Oxygen vacancies could enhance CO 2 activation on the surface of LN-CeO 2 , and oxygen vacancies displayed a linear correlation relationship with the Na content doped in LN-CeO 2. The highest concentration of oxygen vacancies resulted from Na ion incorporated and lower CO 2 reaction order was closely related to CO 2 hydrogenation performance of LN-CeO 2 -100. These results will give insight into the Na effect on the CO 2 hydrogenation mechanism over CeO 2. [ABSTRACT FROM AUTHOR]

• NaCl tailors the temperature sensitivity of CO 2 sorbents. • NaCl accelerates the sintering of the CaO-based sorbents. • NaCl triples the CO 2 capture capacity of the CaO-based sorbents. • Improved CO 2 diffusion leads to the higher CO 2 capture capacity of the NaCl tailored CaO. Calcium looping process is a prospective strategy to remove CO 2 from flue gas. However, the CO 2 capture capacity of the CaO-based sorbents would be spoiled severe over the repeated cycles. In this work, a kind of NaCl-modified CaO-based sorbents were prepared by a simultaneous hydration and impregnation process and explored for cyclic CO 2 capture by a simultaneous thermal analyzer. The promotion mechanism was discussed by electron microscope, X-ray diffraction, N 2 physisorption, X-ray photoelectron spectroscopy, and so on. Results showed that NaCl tailored the temperature sensitivity of CaO-based sorbents, and it was a good promoter to enhance the carbonation activity of CaO-based sorbents, especially under higher temperature modes. At higher temperatures, NaCl would cover the surface of CaO, and promote the CO 2 transportability in the modified sorbent, and then greatly improve the carbonation ability of the sorbents over the cycles. After 50 repeated cycles, the CO 2 capture capacity of "10 NaCl/CaO" still retained at 0.288 g/g and 0.237 g/g when carbonated at 650 °C and 750 °C, which were 2.05 and 2.63 times that of "CaCO 3 AR" respectively. Hence, the temperature-sensitive CaO-based sorbent promoted by NaCl shows a promising prospect for CO 2 capture from flue gas. [ABSTRACT FROM AUTHOR]

• A close-loop CaLP-TCES process for solar energy storage was investigated. • Na 2 CO 3 doubled the energy storage capacity of the CaO-based materials. • "850 °C–900 °C" was best for the Na 2 CO 3 doped CaO in the CaLP-TCES system. • Improved CO 2 diffusion leads to the higher energy storage density of the Na+ doped materials. Calcium looping (CaL) is a promising thermochemical energy storage (TCES) technology to convert solar energy to power in CO 2 Brayton cycle. However, the energy storage density (ESD) of the CaO-based heat carries decays drastically over the CaL cycles, and the energy storage performance of the CaO-based materials in a close-loop CaL-TCES system is still unclear. In this work, a novel Na 2 CO 3 modified method was proposed to enhance the ESD of the CaO-based materials over the close-loop CaL-TCES process, and the enhancing mechanism was investigated by the simultaneous thermal analyzer, X-ray diffraction, electron microscopy, N 2 physisorption, X-ray photoelectron spectroscopy. The "10Na 2 CO 3 /CaO" showed more promising ESD over the cycles, even though it suffered sintering. After 60 cycles, the "10Na 2 CO 3 /CaO" still held an ESD of 594 kJ/kg, which was 2.27 times that of "Neat CaO" when cycled at "850 °C–900 °C" mode. Increase the carbonation temperature from 650 °C to 850 °C, the cyclic energy storage densities of the "10Na 2 CO 3 /CaO" ascended rapidly, which was opposite to the "Neat CaO". The optimum operating condition for the "10Na 2 CO 3 /CaO" is "850 °C–900 °C" when operated in the close-loop CaL-TCES system. The Na+ species that enriched on the surface of the CaO grains were in amorphous or melting state, and they would react with CaO to form Na-Ca solid solution over the cycles. The "10Na 2 CO 3 /CaO" has a tendency of sintering over the cycles, but Na 2 CO 3 improves reaction kinetics. One suggested mechanism is that the Na+ species may break through the mass transfer barriers to absorb CO 2 during the carbonation process. Therefore, although the Na 2 CO 3 doped CaO materials had poorer surface topography, they held much higher ESD over the repeated cycles. [ABSTRACT FROM AUTHOR]

• A novel phase change absorbent was proposed for CO 2 capture with low energy consumption. • Ethanol promoted phase change behavior and increased CO 2 loading. • Reaction of CO 2 capture with [N 1111 ][Gly]/ethanol was a three-step reaction. • Intramolecular hydrogen bonds affected products' solubility, causing phase change. Carbon capture and utilization technologies are urged more than ever due to the excessive emissions of CO 2 that could lead to serious environmental problems. Phase change absorbents are quite competitive in reducing the energy consumption of carbon capture. In this work, tetramethylammonium glycinate ([N 1111 ][Gly]), an efficient absorbent, was dissolved in ethanol and 1-propanol, respectively, to absorb CO 2. After CO 2 absorption, the saturated solution separated into two phases. CO 2 was enriched in the lower phase, so that only the CO 2 -rich phase needed to be regenerated and the energy consumption of regeneration could be thus reduced. Under the optimal conditions, the CO 2 loading of fresh absorbents could reach 0.85 mol CO 2 /mol IL. On the basis of the 13C NMR analysis and quantum chemical calculation, a three-step reaction mechanism of CO 2 capture with [N 1111 ][Gly]/ethanol was proposed. CO 2 reacted with [N 1111 ][Gly] to form carbamate, which was similar to the two-step Zwitterionic mechanism of MEA with CO 2. Then the formed carbamate could react with ethanol to form ethyl carbonate and [N 1111 ][Gly], which resulted in higher CO 2 loading. Moreover, hydrogen bond characteristics were analysed to clarify the phase change mechanism. The number and bonding energy of intramolecular hydrogen bonds were increased after capturing CO 2 , leading to the formation of precipitation. [ABSTRACT FROM AUTHOR]