The core–shell catalysts with Cu and Cu/ZnO nanoparticles coated by mesoporous silica shells are prepared for CO2 hydrogenation to methanol. With the confined effect of silica shell, the size of Cu ...nanoparticles is only about 5.0nm, which results in high activity for CO2 conversion. The CH3OH selectivity is enhanced significantly with the introduction of ZnO. The core–shell structured catalysts endow the Cu nanoparticles trapped inside with excellent anti-aggregation and no deactivation is observed with time-on-stream. Therefore, the core–shell Cu/ZnO@m-SiO2 catalyst exhibits the maximum CH3OH yield with high stability.
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•The Cu and Cu/ZnO nanoparticles coated by mesoporous silica shells are prepared.•The Cu nanoparticle size is only 5.0nm with the confined effect of silica shell.•The proportion of strongly basic site enhances markedly with the addition of ZnO.•The core–shell endows Cu particles trapped inside with excellent anti-aggregation.•The Cu/ZnO@m-SiO2 exhibits the best catalytic performance with high stability.
The Cover Feature illustrates the gradients in structure and activity along a catalytic fixed‐bed reactor during CO2‐methanation. In the focus of this study are Ni‐based catalysts. In their Full ...Paper, by combining spatial activity profiling and complementary structural X‐ray absorption spectroscopic studies, M.‐A. Serrer, M. Stehle et al. uncovered relationships between the course of the reaction including gas phase concentration and the structure of the catalysts. In case of a bimetallic Ni‐Fe‐catalyst, a strong correlation between Fe oxidation state and the amount of water in the gas atmosphere was found. An oxidation of Fe under formation of FeOx species is able to protect the active Ni0 centers from oxidation and can offer an alternative CO2 activation pathway. Compared to a conventional Ni‐based catalyst, this results in higher activity and selectivity. More information can be found in the Full Paper by M.‐A. Serrer, M. Stehle et al.
CO2 hydrogenation to methanol has emerged as a promising strategy for achieving carbon neutrality and mitigating global warming, in which the supported Pd/In2O3 catalysts are attracting great ...attention due to their high selectivity. Nonetheless, conventional impregnation methods induce strong metal-support interaction (SMSI) between Pd and In2O3, which leads to the excessive reduction of In2O3 and the formation of undesirable PdIn alloy in hydrogen-rich atmospheres. Herein, we innovatively synthesized Pd/In2O3 nanocatalysts by the electrostatic self-assembly process between surface-modified composite precursors with opposite charges. And the organic ligands concurrently serve as Pd nanoparticle protective agents. The resultant Pd/In2O3 nanocatalyst demonstrates the homogeneous distribution of Pd nanoparticles with controllable sizes on In2O3 supports and the limited formation of PdIn alloy. As a result, it exhibits superior selectivity and stability compared to the counterparts synthesized by the conventional impregnation procedure. Typically, it attains a maximum methanol space-time yield of 0.54 gMeOH h-1gcat -1 (300 °C, 3.5 MPa, 21,000 mL gcat -1 h-1). Notably, the correlation characterization results reveal the significant effect of small-size, highly dispersed Pd nanoparticles in mitigating MSI. These results provide an alternative strategy for synthesizing highly efficient Pd/In2O3 catalysts and offer a new insight into the strong metal-support interaction.
Carbonaceous materials are widely present in the seismic fault zone. They play a crucial role in lubricating the fault slipping. To date, the formation mechanism of carbonaceous materials is still ...unclear. In this work, we have conducted a carbon dioxide hydrogenation reaction experiment in a homemade high temperature reactor for the purpose to insight the formation mechanism of carbonaceous materials, with fault gouge used as the catalyst. During the reaction process, carbonaceous materials are formed on the fault gouge, suggesting that the carbonaceous materials in the fault zone are possibly generated from carbon dioxide hydrogenation reaction. These results are important for understanding fault behavior and earthquake physics.
As a method for valorizing CO2 emissions, hydrogenation of CO2 into olefins remains viable. Herein, ZnO–ZrO2 and SAPO-34 were prepared and used as bifunctional catalysts in light olefins synthesis ...through CO2 hydrogenation. The combination of the two components includes layered filling, physically mixing, physically grinding, and core-shell composite. Based on the evaluation, different combinations resulted in diverse product distributions. ZnO–ZrO2@SAPO-34 core-shell catalysts are better suited for promoting synergistic effects, which facilitate light olefin production. Due to the unique core-shell structure, appropriate weak acidity, and moderate basicity, the light olefins selectivity was enhanced. Further, the calcination time and core-shell mass ratio were optimized over the ZnO–ZrO2@SAPO-34 core-shell catalyst to investigate the synergistic effects between catalytic structure and catalytic performance. With a 3:1 core-shell mass ratio and 3 h of calcination at 550 °C, the optimal ZnO–ZrO2@SAPO-34 (3:1) catalyst was obtained, which exhibited 73% selectivity to light olefins with CO2 conversion of 16.1%, whereas the selectivity of CO and CH4 was lower than 44% and 1.5%, respectively. This study provides new insights into the design and optimization of ZnO–ZrO2@SAPO-34 core-shell catalysts for CO2 hydrogenation and synthesis of light olefins.
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The performance of the Cu/ZnO catalyst system with the AlMg‐oxide phase is studied for CO2 hydrogenation to methanol. The catalyst is prepared by thermal treatment of the hydrotalcite phase ...containing intimately mixed metal cations in the hydroxide form. CuO in the presence of ZnO and disordered AlMg‐oxide phase gets easily reduced to Cu during the hydrogenation reaction. Its catalytic activity at relatively low Cu metal content (∼14 at.%) remains stable during 100 hours on stream at 260 °C with constant space‐time yield for methanol (∼1.8 gMeOH gcat−1 h−1) and high methanol selectivity (>85 %) The improved performance is attributed to the neutralization of surface acidity, increased number of weak basic sites in the disordered phase, and lower tendency for coke formation.
The performance of the Cu/ZnO catalyst system for CO2 hydrogenation to methanol is improved by using disordered AlMg‐oxide support. The disorder in the mixed metal oxide is characterized by lower surface acidity, increased number of weak basic sites and lower tendency for coke formation. The interactions of Cu with a disordered phase increase Cu reducibility and improve catalyst stability.
Over recent years there has been a significant increase in the amount of technology contributing to lower emissions of carbon dioxide. The aim of this paper is to provide a comparison between two ...technologies for methanol production, both of which use carbon dioxide and hydrogen as initial raw materials. The first methanol production technology includes direct synthesis of methanol from CO2, and the second has two steps. During the first step CO2 is converted into CO via RWGS (reverse water gas shift) reaction, and methanol is produced during the second step. A comparison between these two methods was achieved in terms of economical and energy-efficiency bases. The price of electricity had the greatest impact from the economical point of view as hydrogen is produced via the electrolysis of water. Furthermore, both the cost of CO2 capture and the amounts of carbon taxes were taken into consideration. Energy-efficiency comparison is based on cold gas efficiency, while economic feasibility is compared using net present value. Even though the mentioned processes are similar, it was shown that direct methanol synthesis has higher energy and economic efficiency.
•We compared two methods for methanol production.•Process schemes for both, direct synthesis and two-step synthesis, are described.•Direct synthesis has higher economical and energy efficiency.
CoCu/TiO2 catalysts promoted using alkali metals (Li, Na, K, Rb, and Cs) were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The ...influences of the alkali metals on the physicochemical properties of the CoCu/TiO2 catalysts and the catalytic performance for CO2 hydrogenation to long-chain hydrocarbons (C5+) were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO2 temperature-programmed desorption (TPD), and H2-TPD, the introduction of alkali metals could increase the CO2 adsorption and decrease the H2 chemisorption, which could suppress the formation of CH4, enhance the production of C5+, and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO2 catalyst provided the maximum C5+ yield of 5.4%, with a CO2 conversion of 18.4% and C5+ selectivity of 42.1%, because it showed the strongest basicity and a slight decrease in the amount of H2 desorption; it also exhibited excellent catalytic stability of more than 200 h.
Among the alkali metals (Li, Na, K, Rb, and Cs), the Na-modified CoCu/TiO2 catalyst exhibits the best performance because it shows the strongest basicity and reveals only a slight decrease in the amount of H2 desorbed.
The interaction of CO
2 and H
2/CO
2 with pure
β-Ga
2O
3 and Pd/
β-Ga
2O
3 (1 wt% Pd) was studied by temperature-programmed reaction, between 323 K and 723 K at 0.1 MPa, using in situ FTIR ...spectroscopy. Under CO
2(g), bicarbonate, bidentate, and polydentate carbonate species are formed over the surface of gallia at 323 K. When
β-Ga
2O
3 is exposed to H
2/CO
2 only polydentate carbonate reacts with hydrogen, at
T
>
473
K
(i.e., after the dissociative adsorption of H
2 on gallia), to give bidentate and monodentate formate species (b-HCOO and m-HCOO, respectively) which are further hydrogenated to methoxy groups, just over 523 K. It is proposed that the addition of Pd to the oxide support only increases the hydrogenation rate of all the carbon-containing species bonded to the
β-Ga
2O
3 surface, by spillover of atomic H from metallic Pd to gallia: (i) at 323 K (bi)carbonate groups are hydrogenated to m-HCOO and b-HCOO, and (ii) from 423 K upwards m-HCOO is further transformed to methoxy. A strong evidence of the interconversion between m-HCOO and b-HCOO was also found.
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