Methyl N-phenylcarbamate (MPC) is an important intermediate for the synthesis of diphenylmethane diisocyanate (MDI), and its preparation using CO₂ or its equivalents/derivatives as carbon source represents a green and sustainable manner for fine chemicals synthesis. This review will highlight the development of MPC synthetic methods from the viewpoint of chemical fixation of CO₂. The contents mainly include the introduction of MPC synthesis through CO₂ equivalents (urea or phenyl urea) alcoholysis, dimethyl carbonate (DMC) aminolysis, and the coupling of DMC and diphenyl urea. Furthermore, one-pot synthesis of carbamates/MPC from aliphatic amines/aniline, CO₂ and alcohols is highlighted which represents one of the most promising schemes in direct CO₂ utilization. What is more, the reaction mechanisms and selection of catalysts are also discussed in detail. The advances will provide important theories on further improving the efficiency of green catalysis and sustainable chemical processes.

CO₂ methanation is a very complex heterogeneous catalytic process, in which a variety of intermediates are produced. There are still many controversies and contradictions in the exploration of the reaction pathway of CO₂ methanation. In-depth and systematic study of the evolution process of the intermediates formed on the catalyst surface in CO₂ methanation will help to further optimize the design of catalyst from the perspective of mechanism, thereby improving the catalytic performance. This paper summarises recent work on the CO₂ methanation reaction pathway based on in situ infrared spectroscopy, focusing on the influence of the active metal, carrier, additives and synthesis method of the supported catalyst on the CO₂ methanation reaction pathway and the resulting positive effects on catalyst performance. In addition, the controversial points faced at the current stage, such as the activation sites of reaction gases CO₂ and H₂, the active sites of catalysts and the feasible research methods in the future are discussed in detail.

Hydrogen is considered to be one of the most desirable clean energy sources and plays an important role in petroleum, chemical, metallurgical, petrochemical, food and fertilizer industries. Steam catalytic reforming of bio-oil for hydrogen production is considered as a promising and economically viable sustainable green hydrogen production technology, which has received a lot of attention from researchers. This paper presents a review of recent research in this field, focusing on the catalytic reforming of bio-oils (bio-crude oil, aqueous bio-oil and heavy bio-oil/tar), bio-oil model compounds (carboxylic acids, alcohols, phenols, etc.) and other bio-oil derivatives for hydrogen production, including the reforming reaction mechanism, reforming process and catalysts. The development of energy-efficient and efficient catalytic reforming reactors and stable and highly active reforming catalysts are the main focus of current and future research and promotion in the field of catalytic reforming of bio-oil for hydrogen production.

Fe-based Fischer-Tropsch synthesis (FTS) catalysts usually exist as the oxide precursor α-Fe₂O₃, which have different catalytic activities after being transformed to Fe_xC_y under different pretreatment conditions, so it is critical to study the pretreatment process of α-Fe₂O₃ for whole FTS reaction. However, the phases of Fe-based catalysts in such a process are highly dynamic and complex, and conventional characterizations cannot capture the accurate real-time information in the pretreatment reaction. Therefore, it is necessary and desired to apply various in-situ characterizations in this process, because they can obtain the dynamic changes of phase, morphology, surface structure and properties of the catalyst. And then a relationship between the pretreatment process and the subsequent catalytic performance of FTS will be effectively and reasonably established. This review presents a systematic summary of the experimental and data processing methods in in-situ characterizations of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy and Raman spectroscopy during the pretreatment of Fe-based FTS catalysts. These characterizations can clarify the complex structure and surface property changes of catalyst precursors and thus will facilitate the design and development of more efficient Fe-based FTS catalysts.

ZrO₂ catalysts with different crystal structures show different catalytic performance in isobutene synthesis from CO hydrogenation reaction. Although monoclinic ZrO₂ has the best catalytic performance in isobutene synthesis from syngas, its isosynthesis active sites are still not well understood. To better understand the critical parameters that influence syngas to isobutene reactions over ZrO₂ catalysts, we prepared a series of ZrO₂ catalysts with distinct crystal structures and investigated their catalytic performance of CO hydrogenation to isobutene. Compared with tetragonal and amorphous ZrO₂ catalysts, there are more coordinatively unsaturated Zr and O sites on the surface of monoclinic ZrO₂ catalyst. The coordinatively unsaturated Zr sites are the active sites of CO adsorption and activation, which is beneficial to CO conversion. The coordinatively unsaturated O sites provide more basic sites for isobutene formation. Furthermore, the coordinatively unsaturated Zr and O sites on monoclinic ZrO₂ catalyst surface may inhibit electron transfer to formate species formed during reaction, resulting in weak adsorption on catalyst surface of formate species. The weakly adsorbed formate species on the surface of monoclinic ZrO₂ catalyst is favorable for the synthesis of isobutene from CO hydrogenation reaction.

Due to the intervention from the water-gas shift (WGS) reaction (or the reverse one (RWGS)), the hydrogenation of CO (or CO₂) into alcohols and hydrocarbons often displays rather high selectivity to CO₂ (or CO), which makes it rather puzzling to evaluate such conversion processes by using the relatively low selectivity to the target products. Herein, a thermodynamic consideration is made to elaborately evaluate the effect of the WGS/RWGS reaction on the hydrogenation of CO, CO₂, and their mixture to typical alcohols (e.g. methanol) and hydrocarbons (e.g. ethene). The results indicate that for the hydrogenation of CO (or CO₂), although the WGS (or RWGS) reaction, acting as a communicating vessel connecting CO and CO₂, may have a severe influence on the equilibrium conversion of CO (or CO₂), forming a large amount of CO₂ (or CO), it only has a relatively minor impact on the C-based equilibrium yield of the target alcohol/hydrocarbon product. The hydrogenation of CO shows a higher C-based equilibrium yield for the target product than the hydrogenation of CO₂, while the overall C-based equilibrium yield of target product for the hydrogenation of the CO and CO₂ mixture just lies in between. For the hydrogenation of the CO and CO₂ mixture, although the equilibrium conversion of CO and CO₂ may vary greatly with the change in the feed composition, the relation between the overall C-based equilibrium yield of the target product and the feed composition is rather simple; that is, the overall C-based equilibrium yield of alcohol/hydrocarbon product decreases almost lineally with the increase of the CO₂/(CO + CO₂) molar ratio in the feed. These results strongly suggest that the mixture of CO and CO₂ is credible in practice for the production of alcohols and hydrocarbons through hydrogenation, where the overall C-based yield should be used as the major index for the hydrogenation of CO, CO₂, and their mixture.

The formation of the first carbon ring is a crucial rate-controlling step in developing polycyclic aromatic hydrocarbons (PAHs). It is vital to investigate the mechanism of the creation of the first carbon ring to inhibit the formation of PAHs. To explore the growth process of the first carbocyclic ring, this work used the average localized ionization energy (ALIE) and electrostatic potential (ESP) to predict the reaction sites. Moreover, the reaction paths and chemical kinetic parameters for the generation of the first carbocyclic ring from propargyl (C₃H₃) + diacetylene (C₄H₂) are calculated based on the density functional theory  (DFT) method and transition state theory (TST). The results showed that the addition reaction of C₃H₃ +C₄H₂ can form five-, six- and seven-membered ring molecules, in which the five-membered ring formation is fastest and the six-membered ring formation is slowest. During the formation of the first carbon ring, the activation energy required for the H transfer and cyclization reactions is large, and the reaction rate is slow, which determines the formation rate of the first carbon ring. The rate of H-transfer reaction on each carbon ring depends on the number of C atoms of the carbon ring, with the five-membered ring being the fastest and the six-membered ring the slowest. This paper improves the reaction kinetics and thermodynamic data of the first carbon ring formation during the combustion of hydrocarbon fuels, which offers a powerful theoretical basis for predicting the generation of PAHs.

Alkaline earth metal calcium is a typical poison in coal-fired power plants, which will result in deactivation of SCR catalyst. The ATMP (amino trimethylene phosphonic acid) and PBTCA (2-phosphonobutane-1,2,4-tricarboxylic acid) complexing agents were employed for the regeneration of a poisoned by calcium V₂O₅-WO₃/TiO₂ catalyst. The physical and chemical properties and regeneration denitration performance of the catalyst before and after regeneration were investigated by BET, NH₃-TPD, H₂-TPR, XPS and experiments. The results indicated that the ATMP and PBTCA exhibited efficient regeneration performance, and the NO_x conversion of regenerating catalysts recovered from 25.8% to 89.8% and 88.1% at 400 ℃, respectively. Compared with the regeneration by dilute sulfuric acid, the ATMP and PBTCA exhibited a higher calcium removal rate with lower vanadium loss (less than 5%). The utilization of the ATMP and PBTCA can effectively restore the Brønsted acid sites, active vanadium V^{5 +} and the surface chemisorbed oxygen O_α on the catalyst surface, which leads to the overall activity of the catalyst reaching an optimal level. Therefore, it has a great potential to apply ATMP and PBTCA complexing agents in the regeneration of deactivated SCR denitration catalysts.

A series of Co-doped La_1.5Sr_0.5Ni_1−xCo_xO_4+δ cathode materials ( x =0, 0.2, 0.4 and 0.6) were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), coefficient of thermal expansion (CTE) measurement and scanning electron microscope (SEM). The results suggest that all La_1.5Sr_0.5Ni_1−xCo_xO_4+δ samples have a single pure phase with the perovskite-like structure and the doping with the Co element can increase the CTE value. Using La_1.5Sr_0.5Ni_1−xCo_xO_4+δ as the cathode materials in the solid oxide fuel cell (SOFC), their electrical conductivity and electrochemical impedance spectroscopy were measured. The results indicate that the conductivity increases with the increase of Co doping amount and the La_1.5Sr_0.5N_i0.6Co_0.4O_4+δ sample with x = 0.4 displays the highest conductivity of 51.21 S/cm at 800 ℃; however, a higher content of Co (x > 0.4) leads to a decrease of the conductivity. In addition, La_1.5Sr_0.5N_0.6Co_0.4O_4+δ exhibits the lowest polarization resistance of 4.180 Ω·cm² in electrochemical impedance spectrum at 700 ℃, displaying its excellent electrochemical properties as the cathode materials.

Solid oxide fuel cell (SOFC) is a promising power-generation device. Direct operation of SOFC on methane has several important advantages, such as simple system, high efficiency and low emissions. The challenge of the state-of-the-art nickel cermet anode is prone to coke formation when operating on methane, which may cause rapidly deteriorate of the performance and durability on SOFC. In this work, the anode Ni-BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ (BZCYYb) was investigated for wet methane (97% CH₄-3% H₂O) conversion in the temperature range of 700 to 600 ℃. The Ni-BZCYYb anode showed a good electrochemical performance for the steam reforming of methane. Furthermore, under a constant current density, a good operational stability was achieved at 600 ℃ for 100 h operating. For comparison, a conventional Ni-YSZ anode was also prepared, the voltage of cell dropped to zero after feeding wet CH₄ for ~ 6 h. These results indicate that the Ni-BCZYYb is a good candidate as the anode in SOFC on methane fuel.

In this paper, nitrogen-doped graphitic carbon materials (N-GMCs) with unique layered structure were prepared by calcining a mixture of melamine and glucose at high temperature. The Rh/N-GMCs catalyst was finally prepared by impregnation-reduction method using N-GMCs as the carrier to support the metal Rh on the surface of the carrier. The results showed that there was a strong metal-support interaction between Rh and N-GMCs, and the reaction transition frequency (TOF) value reached a peak when the loading amount of Rh was 0.4%. At this time, the TOF value of AB dehydrogenation reaction catalyzed by 0.4%Rh/N-GMCs catalyst was 645.3 min^–1, and the activation energy (E_a) of ammonia borane hydrolysis on this catalyst was 54.0 kJ/mol. The rate was positively correlated with the ammonia borane concentration and the catalyst concentration. After 10 cycles of the catalyst, the catalytic activity did not decrease significantly, indicating that the catalyst had excellent cyclic stability.

In order to improve the efficiency of biomass gasification to hydrogen production, the comprehensive utilization of industrial solid waste resources, the use of calcium-based waste-calcium carbide slag as a CO₂ adsorbent, experiments were carried out in a two-stage fixed bed to explore the effect of calcium-based waste addition, reaction temperature on the biomass gasification hydrogen production characteristics, focusing on the study of the adsorbent in practical applications of the cyclic adsorption performance, and thus discuss the influence mechanism of calcium carbide slag on biomass adsorption enhanced gasification. The results show that with the gradual increase of calcium carbide slag addition, H₂ yield and concentration show an increasing trend. With the increase of temperature, the yield and concentration of H₂ increase first and then decrease. When the CaO/C molar ratio is 1 and the temperature of the reforming section is 700 ℃, the yield and concentration of H₂ in the gas product are 154.34 mL/g biomass and 26.76%, and the maximum value is obtained. When the number of calcium carbide slag cycles is less than 5, the concentration and yield of H₂ increase compared to the initial reaction.

In this study, nitrogen-oxygen co-doped porous carbon materials with nano-sheet structure were successfully prepared by template method and chemical activation method using coal pitch with low cost and abundant sources as carbon precursor, urea as nitrogen source and template, and sodium hydroxide as activator. The porous carbon electrodes exhibit a maximum specific capacity of 255.5 mA·h/g at 0.05 A/g and a discharge specific capacity of 78 mA·h/g at 1 A/g. Moreover, the porous carbon electrodes deliver about 72.4% capacitance retention after 12000 cycles and a high energy density of 99.6 W·h/kg, showing great potential as cathode material. The nitrogen-oxygen co-doped porous carbon materials prepared from coal pitch display an excellent electrochemical performance as cathode material for zinc ion hybrid supercapacitors.

Ash content is an important factor affecting the quality and combustion performance of biochar. In this paper, a method of ash removal from biomass is proposed by carbonization followed by CO₂-enhanced water leaching. The effects of the carbonization temperature of bagasse, the temperature and time of CO₂-enhanced water leaching on the deashing were investigated. The results show that the deashing rate firstly increases and then decreases with the carbonization temperature, while the opposite trend is obtained with increasing the water leaching temperature and time. For bagasse biochar carbonized at 300 ℃, the deashing rate reaches 57% at the water leaching temperature of 40 ℃ for 4 h. Compared with water leaching without carbonization, the proposed method can increase the content of fixed carbon and the char yield by 7% and 3%, respectively. It is because  in the process of deashing, CO₂ diffuses and dissolves into water to form carbonic acid which reacts with part of metal salts to form water-soluble salts, resulting in the removal rate of K, Na and Ca up to above 50%, and part removal of calcite and dolomite. Also, the proposed process shows higher deashing efficiency and universality, but the deashing degree is closely related to the ash composition and kinds in biochar. As to peanut shell and poplar, the deashing rate exceeds 30% by carbonization at 300 ℃ and CO₂-enhanced water leaching at 40 ℃ for 4 h.

In order to realize the effective resource utilization of coal gasification residues (CGR), the composite microwave absorbents loaded with different magnetic components were prepared through wet chemical impregnation and roasting progress, recycling of coal gasification residue as carbon-based carrier. The results showed that the main reaction involved in gradual carbothermal reduction reaction, during which the Fe₂O₃ and Fe₃O₄ were transformed into Fe. And part of high-activity carbon in CGR was consumed as well, which resulted in the poor graphitization degree of CGR composites. Benefitted from the better impedance matching and attenuation characteristic, FeCGR1000 displayed excellent microwave absorbing performance. The reflection loss value reached −25.3 dB under the coating thickness of 2.0 mm, and the effective bandwidth kept 4.0 GHz as the coating thickness remained 1.5 mm. This work not only benefitted for realizing the resource utilization of CGR, but also provided new ideas for the high additional value application for CGR.