## 留言板

La2O3 as a catalyst is used for oxidative coupling of methane (OCM) reactions due to its excellent stability and high C2 selectivity, but poor activity on methane dissociation limits its wide application. Different valence metals are doped on the La2O3(001) surface to improve the methane conversion activity, and the activation of methane on metal-doped La2O3(001) surfaces has been investigated via the density functional theory (DFT) calculations. The relationship between the valence states of doped metals and the methane conversion activities shows that doping low valence metals (Li, Na, K, Mg, Ca, Sr and Ba) and equivalent metals (Al, Ga, In) can significantly improve the conversion activity of methane. Among them, the activation energy of methane on the Li-La2O3(001) surface is the lowest, which is only 13.0 kJ/mol. However, doping of high valence metals (Zr, Nb, Re and W) cannot improve the CH4 dissociation activity. Furthermore, the relationships between surface oxygen vacancy formation energies, acid-base properties and the activation energies of CH4 have also been investigated. The results show that with the increase of metal valence state, the oxygen vacancy formation energy increases, while the dissociation activity of CH4 decreases. The introduction of alkali and alkaline earth metals increases the alkalinity of La2O3(001) surface, and the alkalinity of La2O3(001) doped with the alkali metal is stronger than that with the alkaline earth metal, exhibiting higher dissociation activity of CH4. Our research may provide a guide for improving methane conversion activity on La2O3 catalysts.

Using pseudo-boehmite and ultrafine copper hydroxide as the raw materials with n(Cu/Al) = 1∶3, the effects of ball milling medium on the Cu-Al spinel sustained release catalysts prepared via the solid-state reaction method are explored. The obtained catalysts are characterized by XRD, BET, and H2-TPR techniques, and their catalytic properties in methanol steam reforming (MSR) are evaluated. The results demonstrate that Cu-Al spinel solid solution can be synthesized by both dry and wet mechanical ball milling methods, and more Cu2 + ions are found to be incorporated into the spinel lattice through the latter method. The crystalline sizes of as-synthesized spinels are similar; however, the specific surface areas and pore volumes are different as well as their reduction properties. Compared with the dry milling method, the wet ball milling method can facilitate the solid phase reaction, generating catalysts with solely spinel crystalline phase, higher specific surface area, and larger pore volume. Furthermore, catalysts derived from the wet milling method demonstrate improved catalytic activity and stability, and lower CO selectivity in MSR. The highest activity is obtained over CuHAl-Ac-950 prepared using ethanol (95%) as the ball milling medium.

Direct synthesis of liquefied petroleum gas from syngas via Fischer-Tropsch synthesis route was systematically investigated over a nano-level core@shell catalyst. We introduced an incorporation of FeMg catalyst into mesoporous silica shell, with a further modification of Cu particles on the silica surface. The modified Cu/FeMg@SiO2 nano core-shell catalysts were synthesized by the combination of co-precipitation, modified sol-gel and facile impregnation methods. The as-synthesized catalysts’ physicochemical property was characterized by XRD, TEM, N2 adsorption-desorption, H2-TPR, XPS and CO2-TPD techniques. The catalytic performance of Cu/FeMg@SiO2 catalyst shows a high CO conversion of 96.6%, rather low CO2 selectivity of 21.9% and considerable LPG selectivity of 37.9%. The catalytic results indicate that the SiO2 shell restrains the formation of CH4 and contributes to increasing long-chain products. Meanwhile, the enhanced CO conversion of Cu/FeMg@SiO2 was ascribed to the active metal Cu dispersed on SiO2 shell, which also promoteolefin hydrogenation and cracking of C5+ hydrocarbons products. The proposed catalyst preparation method will provide a new strategy for the synthesis of nano level catalyst with combinations of metal- and zeolite-based catalyst.

The epoxidation of alkenes, an important reaction in the context of upgrade and transform the downstream products of coal-to-oil, is typically conducted with supported tungsten oxide-based catalysts. This article investigates the promoting effect of gallium (Ga) on the activity of Ga-WOx/SBA-15 catalyst for cis-cyclooctene epoxidation with H2O2. The optimal catalyst of 0.3Ga-WOx/SBA-15 offered a turnover frequency (TOF) of 112 h–1, which was nearly two times than that of WOx/SBA-15 (57 h–1). The low apparent reaction activation energy for 0.3Ga-WOx/SBA-15 (49.6 kJ/mol vs 64.0 kJ/mol for WOx/SBA-15) was also in line with its superior performance. Kinetic analysis demonstrated stronger adsorption of H2O2 on 0.3Ga-WOx/SBA-15 surface, facilitating the H2O2 activation. Based on the characterizations and catalytic performance, the improvement of Ga was attributed to the increase of Lewis acid sites and the enhancement of electrophilicity. Furthermore, the metal hydrogen peroxide (M-OOH) was identified as the primary intermediate.

Supported cobalt catalysts (Co@C-ZnZrO2 and Co/ZnZrO2) were prepared through a metal-organic frameworks (MOFs)-mediated synthesis strategy. The influence of MOFs pyrolysis on the structure and Fischer-Tropsch synthesis performance of supported cobalt catalysts was investigated. The crystalline phase and microstructure of supported cobalt catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), N2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS). The Co/ZnZrO2 showed the CO conversion of 18.1% and the C5 + selectivity of 77.4%, whereas the Co@C-ZnZrO2 exhibited the CO conversion of 8.5% and the C5 + selectivity of 35.2%. The excellent CO conversion for Co/ZnZrO2 was attributed to the more exposure of active Co sites. Meanwhile, the activity of Co sites on Co@C-ZnZrO2 catalyst was restricted by the carbon layer, suppressing the adsorption and activation of syngas on Co sites.

The effects of supports (CeO2, ZrO2, MnO2, SiO2 andactive carbon) on the structure and catalytic performance of Ru-based catalysts for Fischer-Tropsch synthesis to olefins (FTO) were investigated. It was found that the intrinsic characteristics of supports and the metal-support interaction (MSI) would greatly influence the catalytic performance. The catalytic activity followed the order: Ru/SiO2 > Ru/ZrO2 > Ru/MnO2 > Ru/AC > Ru/CeO2. As far as olefins selectivity was concerned, both Ru/SiO2 and Ru/MnO2 possessed high selectivity to olefins (>70%), while olefins selectivity for Ru/ZrO2 was the lowest (29.9%). Ru/SiO2 exhibited the appropriate Ru nanoparticlessize ( ~ 5 nm) with highest activity due to the relative low MSI between Ru and SiO2. Both Ru/AC and Ru/MnO2 presented low CO conversion with Ru nanoparticles size of 1−3 nm. Stronger olefins secondary hydrogenation capacity led to the significantly decreased olefins selectivity for Ru/AC and Ru/ZrO2. In addition, partial Ru species might be encapsulated by reducible CeO2 layer for Ru/CeO2 due to strong MSI effects, leading to the lowest activity.

In this work, to better understand catalytic gasification process of direct coal liquefaction residue rich in sodium species, char structure evolution and behaviors of sodium species during gasification under CO2 atmosphere were investigated in detail by N2 adsorption and desorption, FT-IR, XRD, SEM, and Raman analyses. The results show that sodium species developed pore structure of direct coal liquefaction residue during gasification, especially expanded mesoporous structures which increased from 0.05 to 0.16 cm3/g at maximum. With the increase of gasification time, different crystalline compounds were formed in chars. Most of the mineral matters identified by XRD were calcium-containing ones, whereas no obvious sodium-containing crystalline compounds were found. This was because that most of sodium species volatilized at high temperature and the crystalline forms of sodium-containing compounds had defects. Compared with sodium species, calcium species were more prone to react with aluminosilicates, which happened to make sodium species remain active during gasification process. The ratio of (GR + VL + VR)/D rose initially and then decreased, which could be explained as the dissociation of the large aromatic and the rearrangement of small aromatic rings into large aromatic structures. Moreover, release ratio of sodium species was closely related with gasification time and 49.8% of them released in the initial stage of gasification process (within 15 min). Compared with that of direct coal liquefaction residue reloaded with water-soluble sodium species, the release ratio of sodium species in the original direct coal liquefaction residue was on a lower level (85.2% versus 89.7%).

In this work, a Fe-doped Co3O4 OER electrocatalyst supported by an N-doped hollow nanocage carbon framework (Fe-Co3O4/NC) was successfully prepared by anion exchange and annealing in an air atmosphere strategy. XRD and HRTEM characterizations confirm that Fe the incorporation of Fe into the lattice of Co3O4. XPS characterization clarifies that the valence state of Co increases after the introduction of Fe, which originates from the electrons transfer from Co2+/Co3+ to Fe3+ and is induced by the valence electron configuration of cations. It simulates Co sites in situ derived into CoOOH active species during the OER process, which is confirmed by the HRTEM and XPS characterization after the OER stability test. Electrochemical performance tests show that the Fe-Co3O4/NC electrocatalyst only exhibits 275 mV overpotential to achieve a current density of 10 mA/cm2 and stably maintains for 20 h at 100 mA/cm2. Together with 20% Pt/C electrocatalyst, the composed two-electrode system only needs 2.041 V applied potential to achieve 100 mA/cm2 for total water splitting in a self-made membrane electrode device, which has industrial application prospects.

We anchored atomically dispersed Fe-N4 sites on hollow N-doped carbon spheres (Fe SAs/HNCSs-800) for electrocatalytic ORR; the obtained material exhibited electrocatalytic activity and stability comparable to that of commercial Pt/C, with an onset potential of 0.925 V and a half-wave potential of 0.867 V. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectroscopy results confirmed the presence of highly dispersed Fe single atoms in Fe SAs/HNCSs-800. The results of experiments and theoretical calculations show that the single-atom dispersed Fe-N4 serve as the ORR active sites, and the adjacent C defects can effectively regulate the electronic structure of Fe atoms and improve the electrocatalytic ORR activity.

To provide some useful suggestions to the operation of circulating fluidized bed (CFB) gasifier, the effect of gasification temperature, residence time and agent on the release and transformation of sodium was studied by using a fixed bed reactor combined with Factsage software. The results indicated that gasification temperature was the significant factor to the release and transformation of sodium. For the promoting effect of sodium release, it was ascribed to the intense of sodium volatilization and competitive reaction between lime and meta-kaolin. Meanwhile, the high temperature promoted the formation of nepheline and slag. The threshold temperature of latter was near 950 °C. It was interesting to find that the release of sodium could be divided into two stages: coal pyrolysis and char gasification. In coal pyrolysis, part of organic and water-soluble sodium was released. The remainder either combined with char structure, or reacted with minerals. In char gasification, Sodium, combined with char structure, was released along with char gasification. Due to the decrease of melting temperature and the formation of NaOH, steam showed a promoting effect on the sodium release. Oppositely, oxygen and nitrogen presented an inhibiting effect. The former was ascribed to the formation of Na2SO4, while the latter was caused by the chemical binding and physical wrapping effect of char.

In the present study, the kinetic behaviour and active sites evolution processes of Pt-based catalysts were investigated. It was found that highly selective hydrogen combustion could be achieved over Sn modified Pt-based catalysts in presence of both propane and propene (over 98%). The stability tests, kinetic study and catalyst characterization revealed that the existence of oxygenated species is the reason for accelerated coking reactions. The formation of graphitized cokes serving as additional unselective active sites and the oxidation of tin in PtSn alloy phases are the primary reasons causing the catalytic selectivity loss during long-run tests under propene-rich condition.

The PrxZr1−xO2-δ catalyst with different atom ratio of Pr/Zr was prepared by the sol-gel to catalytic oxidation denitration. Results showed that the efficiency of catalytic oxidation denitration increased initially and decreased afterward with the ratio of Pr atom increased. And the optimum denitration activity could achieve 94.62% at 250 °C when the atom ratio of Pr/Zr was 5∶5. The catalysts were characterized by SEM, N2 adsorption/desorption, XRD, XPS, H2-TPR, and FTIR. The results illustrated that the catalyst (Pr0.5Zr0.5O2−δ) with the best activity has a "layered" morphology, many pores on the surface, and it has a large specific surface area and pore volume of 77.44 m2/g and 0.66 cm3/g, respectively. Furthermore, the crystalline phase transforms from c-ZrO2 to Pr2Zr2O7 with the increasing of Pr atom. XPS and H2-TPR results showed that the surface chemosorption oxygen and surface Pr4 + oxides increased, and the rising of Pr atom ratio was beneficial to produce oxygen vacancy (Vӧ) site which advantageous to improve the efficiency of catalytic oxidation denitration. FTIR characterization results indicated that Pr0.5Zr0.5O2−δ solid solution had better NO selectivity, which was conducive to the catalytic oxidation of NO. The anti-SO2 and H2O toxicity experiments showed that Pr / Zr atomic ratio at 5∶5 had better anti-toxicity than other ratios. In addition, using IC to analysis absorption products, the result showed that ${\rm{NO}}^-_2$ and ${\rm{NO}}^-_3$ were the main products in the absorption solution.

CO2作为主要的温室气体，对全球生态系统造成了巨大影响。生物炭因其原料来源广泛、制备成本低廉等原因，被认为是一种具有成本效益的CO2吸附剂，但原始生物炭的结构特性和表面化学性质较差，所以需要对其理化性质进行调整。本文从生物炭的理化性质出发，对生物炭的制备及改性方法进行了系统的分析，并在前人研究的基础上，对生物炭吸附CO2的机理进行了总结。着重分析了改性过程中生物炭孔隙结构和表面化学性质等对机理的影响。此外，还探讨了生物炭作为CO2吸附剂在大规模CO2捕集中可能存在的问题，以及未来研究的主要方向，旨在为改性生物炭CO2吸附剂的制备及应用提供理论依据。

Efficient utilization of low-temperature coal tar is important for coal pyrolysis or coking. The low-temperature coal tar is rich in phenols with different reactive sites, resulting in a much higher substitution rate (40%) of phenol than high-temperature coal tar and its distillations. In this study, coal tar-based phenolic foam (CPF) was prepared using low-temperature coal tar as raw material to partially replace phenol. The chemical structure, apparent morphology, compressive strength, thermal stability, flame retardancy and thermal insulation properties of CPFs were characterized. The results show that CPFs have similar chemical structures to conventional phenolic foam. Comparing with conventional phenolic foam, the compressive strength of 30%CPF and 40%CPF increases by 18.3% and 55.9%, and the pulverization rate decreases by 22.9% and 50.8%, respectively. The results indicated that toughness was significantly strengthened due to the incorporation of aliphatic structures such as alkylphenols. In addition, the thermal stability of CPFs in the low temperature stage also improves. Although the limited oxygen index of CPFs decreases and thermal conductivity of CPFs increases, they still maintain good flame retardancy and thermal insulation properties. The obtained results prove that low-temperature coal tar can significantly replace phenol to prepare phenolic foam with good performance, which provides a new idea for the high-value utilization of low-temperature coal tar.

CO2的化学转化作为碳减排的有效手段受到了广泛关注，近年来，通过热催化工艺将CO2加氢转化为乙醇已经取得了突破性的进展，但仍然存在乙醇选择性及产率低、副产物较多等问题。本文对热催化CO2加氢制取乙醇的研究进展进行了综述，主要论述了以分子筛、金属氧化物、钙钛矿、二氧化硅、有机框架、金属碳化物等为载体的催化剂的应用，分析了不同金属间的协同作用对CO2转化过程的影响以及各类活性物种的介入对于反应的促进作用，总结了能够有效促进C–C键偶联以及CO2吸附和活化的催化剂体系。在此基础上分析了影响CO2加氢制取乙醇的因素，并对反应机理进行了讨论。综述为CO2加氢制备乙醇的催化剂设计、合成工艺条件优化以及催化机理的探究提供参考。

CO2催化加氢被认为是生产高附加值化学品和燃料最实用的途径之一。然而由于其化学惰性、C–C键偶联过程的高能垒和诸多的竞争反应，因此开发高效的催化剂以促进CO2的活化并转化为多样的化工产物显得至关重要。近年来，氧化铟因具有丰富的氧缺陷位点，在催化CO2加氢方面对甲醇的高选择性以及对CO2转化的高活性引起了人们的广泛关注。本文主要对In2O3的结构及其与氧化物负载或金属元素掺杂的复合催化剂用于催化CO2加氢制备甲醇的催化性能进行了综述。随后又探讨了In2O3与不同类型的分子筛的接近度和元素迁移在CO2加氢制烃类产物中的影响。最后对In2O3基催化剂在CO2选择性加氢方面存在的挑战和发展方向进行了总结。

Oxidation treated carbon materials for the exploitation of efficient and stable loaded catalysts have been proven to be valid. The surfaces of carbon aerogels (CA) were functionalized with different oxidizing agents, H2O2 and HNO3. A series of Ru-supported catalysts were prepared by impregnation on carbon aerogel (CA) with/without functionalized. The impact of oxidation treatment on the texture features of carbon aerogels, the types and contents of formed surface oxygen-containing functional groups, the metal-support interactions and the Fischer-Tropsch synthesis reaction performance of the catalysts were systematically investigated using XRD, Raman spectra, N2-physisorption, H2-TPR, FTIR and XPS. The experimental results showed that Ru/CA catalyst displayed the highest initial activity but poor stability. In contrast, the Ru/CA-H2O2 catalyst exhibited excellent activity and C5+ selectivity. Characterization results demonstrated that the oxidation treatment increased the carbon aerogels defects, thereby enhanced the specific surface area. The increased content of oxygen-containing functional groups on the surface enhanced the interaction between the support and Ru nanoparticles and improved the stability of the catalyst. Nevertheless, the excessive oxygen-containing functional groups on the surface decrease the activity and C5+ selectivity of carbon aerogels-loaded Ru catalysts.

To explore the catalytic performance of three perovskites (LaBO3--LaCoO3, LaFeO3, LaNiO3), the experimental characterization methods (GC−MS, FT−IR, elemental analysis) and DFT calculation were combined for researching liquefaction of lignin. The effects of time, temperature, catalyst dosage and B cation on the conversion rate, bio-oil yield and bio-oil component distribution were investigated. The results showed that all the three catalysts could promoted the liquefaction of lignin to produce aromatic compounds. Among them, LaCoO3 had the greatest promoting on bio-oil yield, and the highest bio-oil yield of 67.20wt% was obtained at 180 °C for 60 min over 5wt% LaCoO3, followed by LaNiO3 and LaFeO3. The relative content of mono-aromatic compounds reached 89.59% under LaCoO3. Mechanism studies suggested that the adsorption of oxygen atoms on the surface of LaBO3 crystal with lignin reduced the dissociation energy of bonds of lignin. Moreover, LaCoO3 had moderate redox capacity, largest adsorption energy, loose and porous morphology, which could effectively promoted the fracture of C−C and CAr−OCH3 of lignin, so that achieved macromolecular depolymerization and demethoxylation reaction to produce high value-added compounds such as phenol.
2023, 51(4): 1-8.

2023, 51(4): 415-427.   doi: 10.1016/S1872-5813(22)60047-1

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.

2023, 51(4): 428-443.   doi: 10.19906/j.cnki.JFCT.2022063

CO2甲烷化反应是一个复杂的多相催化过程，在反应过程中会产生各种各样的中间体，其反应路径目前还存在许多争议和矛盾。深入系统地研究CO2甲烷化反应中催化剂表面中间体的演变过程，可以进一步从机理的角度优化催化剂的设计方案，提高催化性能。本工作主要基于原位红外光谱表征技术，总结梳理了最近关于CO2甲烷化反应路径研究的相关工作，着重探讨了负载型催化剂的活性金属、载体、助剂、合成方法等因素对CO2甲烷化反应路径的影响以及由此对催化剂性能所产生的积极效果。同时针对现阶段所面临的争论点，即反应气CO2与H2的活化位点、催化剂的活性位点以及未来可行的研究方法进行了详细论述。

2023, 51(4): 444-457.   doi: 10.19906/j.cnki.JFCT.2022061

2023, 51(4): 458-472.   doi: 10.19906/j.cnki.JFCT.2022067

2023, 51(4): 473-481.   doi: 10.1016/S1872-5813(22)60050-1

2023, 51(4): 482-491.   doi: 10.1016/S1872-5813(23)60346-9

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.

2023, 51(4): 492-501.   doi: 10.1016/S1872-5813(22)60054-9

2023, 51(4): 502-510.   doi: 10.19906/j.cnki.JFCT.2022068

2023, 51(4): 511-518.   doi: 10.1016/S1872-5813(22)60057-4

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