Search

Catalytic conversion of CO2 to CO via the reverse water gas shift (RWGS) reaction has been identified as a promising approach for CO2 utilization and mitigation of CO2 emissions. Bare Pt shows low activity for the RWGS reaction due to its low oxophilicity, with few research works having concentrated on the inverse metal oxide/Pt catalyst for the RWGS reaction. In this work, MnOx was deposited on the Pt surface over a SiO2 support to prepare the MnOx/Pt inverse catalyst via a co-impregnation method. Addition of 0.5 wt% Mn to 1 wt% Pt/SiO2 improved the intrinsic reaction rate and turnover frequency at 400 °C by two and twelve times, respectively. Characterizations indicate that MnOx partially encapsulates the surface of the Pt particles and the coverage increases with increasing Mn content, which resembles the concept of strong metal–support interaction (SMSI). Although the surface accessible Pt sites are reduced, new MnOx/Pt interfacial perimeter sites are created, which provide both hydrogenation and C-O activation functionalities synergistically due to the close proximity between Pt and MnOx at the interface, and therefore improve the activity. Moreover, the stability is also significantly improved due to the coverage of Pt by MnOx. This work demonstrates a simple method to tune the oxide/metal interfacial sites of inverse Pt-based catalyst for the RWGS reaction. [ABSTRACT FROM AUTHOR]

A large amount of greenhouse gases, such as carbon dioxide and methane, are released during the production process of bioethanol and biogas. Converting CO2 into methane is a promising way of capturing CO2 and generating high-value gas. At present, CO2 methanation technology is still in the early stage. It requires high temperature (300–400 ℃) and pressure (> 1 MPa), leading to high cost and energy consumption. In this study, a new catalyst, Ni–Fe/Al–Ti, was developed. Compared with the activity of the common Ni/Al2O3 catalyst, that of the new catalyst was increased by 1/3, and its activation temperature was reduced by 100℃. The selectivity of methane was increased to 99%. In the experiment using simulated fermentation gas, the catalyst showed good catalytic activity and durability at a low temperature and atmospheric pressure. Based on the characterization of catalysts and the study of reaction mechanisms, this article innovatively proposed a Ni–Fe/Al–Ti quaternary catalytic system. Catalytic process was realized through the synergism of Al–Ti composite support and Ni–Fe promotion. The oxygen vacancies on the surface of the composite carrier and the higher activity metals and alloys promoted by Fe accelerate the capture and reduction of CO2. Compared with the existing catalysts, the new Ni–Fe/Al–Ti catalyst can significantly improve the methanation efficiency and has great practical application potential. [ABSTRACT FROM AUTHOR]

The reverse water-gas shift (RWGS) reaction is one of the effective ways of carbon dioxide (CO2) conversion. However, the RWGS catalyst has the problem of poor stability under high temperature. A series of Co/SiO2 catalysts with promoters (CeO2, La2O3, Y2O3 or ZrO2) were prepared by incipient-wetness impregnation method for the RWGS reaction. The catalysts were characterized by X-ray diffractometry, transmission electron microscopy and H2-programmed temperature reduction, etc. The effects of promoters on the catalyst structure and RWGS reaction performance were studied. The results of catalyst characterization show that the particle size of Co3O4 in the catalyst is not significantly changed by adding promoters. The promoters of CeO2, La2O3, Y2O3 and ZrO2 interacte with the cobalt component. The catalytic performance test results show that the CO2 conversion rate of the Co/SiO2 catalysts decreases from 28.3% to 9.0% after reaction at 600 °C for 12 h. The stability of the catalysts with promoters is improved, and the Co-ZrO2/SiO2 catalyst has the best stability, and the CO2 conversion rate is still as high as 21.9% after reaction for 12 h. This is due to the presence of interaction between the promoters and the cobalt component after the addition of the promoters, which improves the stability of the active component of cobalt. [ABSTRACT FROM AUTHOR]

The fundamental insights of the reaction mechanism, especially the synergistic effect between oxygen vacancies and basic sites, are highly promising yet challenging for Ru-based catalysts during carbon dioxide (CO2) methanation. Herein, a series of Ru-based catalysts were employed to study the mechanism of CO2 methanation. It is found that Ru/CeO2 catalyst exhibits a much higher CO2 conversion (86%) and CH4 selectivity (100%), as well as excellent stability of 30 h due to the existence of abundant oxygen vacancies and weak basic sites. Additionally, the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations reveal that the formate formation step dominated the hydrogenation route on Ru/CeO2 catalyst, and the b-HCOO* could be the key intermediate due to b-HCOO* is more easily hydrogenated to methane than m-HCOO*. The systematic study marks the significance of precise tailoring of the synergistic relationship between oxygen vacancies and basic sites for achieving the desired performance in CO2 methanation. [ABSTRACT FROM AUTHOR]

Atomically dispersed Ir confined in amorphous MoO3 (Ir1/a-MoO3) was designed as a high-efficiency catalyst for electrochemical reduction reaction of NO to NH3 (NORR). Atomic precise characterizations reveal that isolated Ir atoms are immobilized in O-vacancies of amorphous MoO3 to form Ir1-O5 moieties. Theoretical computations demonstrate that single-site Ir1-O5 can not only powerfully activate and hydrogenate NO with a near-zero energy barrier, but also exhibit a higher affinity to NO over H adatoms to suppress the competing hydrogen evolution and promote both NORR activity and selectivity. Consequently, Ir1/a-MoO3 shows the maximum NH3 yield rate of 438.8 µmol·h−1·cm−2 and NH3-Faradaic efficiency of 93.2%, representing one of the most efficient NORR catalysts to date. [ABSTRACT FROM AUTHOR]

Herein, we explore how OH groups on Pt/γ‐AlOOH and Pt/γ‐Al2O3 catalysts affect CO2 hydrogenation with H2 at temperatures from 250°C to 400°C. OH groups are abundant on γ‐AlOOH, but rare at Pt‐(γ‐AlOOH) interface which is the most favorable site for CO2 conversion on Pt/γ‐AlOOH. This makes CO2 hydrogenation on Pt/γ‐AlOOH form CO weakly bonding to γ‐AlOOH, which prefers to desorption from Pt/γ‐AlOOH rather than further conversion, thus enhancing CO production on Pt/γ‐AlOOH. Different from Pt/γ‐AlOOH, OH groups are abundant at Pt‐(γ‐Al2O3) interface which is the most favorable site for CO2 conversion on Pt/γ‐Al2O3. This promotes CO2 hydrogenation on Pt/γ‐Al2O3 to form CO strongly bonding to Pt, which prefers to further hydrogenation to CH4, and thereby increases CH4 selectivity on Pt/γ‐Al2O3. Therefore, the OH groups at metal‐support interface are crucial factor influencing product distribution, and must be considered seriously when fabricating catalysts. [ABSTRACT FROM AUTHOR]

Formic acid has recently been revealed to be an excellent hydrogen carrier, and interest in the development of efficient and selective catalysts towards its dehydrogenation has grown. This reaction has been widely explored using homogeneous catalysts; however, from a practical and scalable point of view, heterogeneous catalysts are usually preferred in industry. In this work, formic acid dehydrogenation reactions in both liquid- and vapor-phase conditions have been investigated using heterogeneous catalysts based on mono- or bimetallic Pd/Ru. In all of the explored conditions, the catalysts showed good catalytic activity and selectivity towards the dehydrogenation reaction, avoiding the formation of undesired CO. [ABSTRACT FROM AUTHOR]

In this work, the effect of ethanol co-feeding in the synthesis of higher alcohols from syngas over K-MoS2 catalyst was investigated in a batch reactor, and the yield of higher alcohols was improved. K-MoS2 prepared with thiourea as a sulfur source exhibited better performance for synthesizing higher alcohols from syngas due to its more stacking layers, higher specific surface area and more Mo4+ active species. Ethanol co-feeding could provide more alkyl intermediate species, which was conducive to the insertion of CO, thereby promoting the conversion of CO and the production of higher alcohols. A change in the reaction path from insertion of CO to homocoupling of ethanol was found upon increasing the ethanol to CO ratio. Higher alcohols production was maximized with the side products in an acceptable range for n EtOH/n CO = 0.3. [ABSTRACT FROM AUTHOR]

Integrated CO2 capture and hydrogenation to produce formate offers a sustainable approach for reducing carbon dioxide emissions and producing liquid hydrogen carriers (formate) simultaneously. In the current study, three different types of aqueous amine solutions including monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were investigated as CO2-capturing and hydrogenation agents in the presence of a Pd/NAC catalyst. The effect of amine structures on the CO2 absorption products and formate yield was investigated thoroughly. It was found that the formate product was successfully produced in the presence of all three aqueous amine solutions, with tertiary amine TEA accounting for the highest formate yield under the same CO2 loadings. This is due to the fact that primary and secondary amine moieties in MEA and DEA are responsible for the formation of CO2 adducts of carbamate and bicarbonate, whereas the tertiary amine moiety in TEA is responsible for the formation of hydrogenation-favorable bicarbonate as the solo CO2 absorption product. A high yield of formate of 82.6% was achieved when hydrogenating 3 M TEA with 0.3 mol CO2/mol amine solution in the presence of a Pd/NAC catalyst. In addition, the physio-chemical properties of the Pd/NAC catalyst analyzed using TEM, XRD and XPS characterization were applied to rationalize the superior catalytic performance of the catalyst. The reaction mechanism of integrated CO2 capture and hydrogenation to produce formate in aqueous amine solutions over Pd/NAC catalyst was proposed as well. [ABSTRACT FROM AUTHOR]

An Ni-CeO2 catalyst with high Ni loading (50 wt.%) prepared by a salt-assisted solution combustion method was characterized by different methods and used for CO2 methanation. The specific surface area of the Ni-CeO2 catalyst prepared by salt-assisted solution combustion is 7 times that of the catalyst prepared by conventional solution combustion. The Ni-CeO2 catalyst prepared by salt-assisted solution combustion has smaller particle sizes of Ni and exhibits excellent activity at low temperatures. The high Ni loading and small Ni particle size can provide more metal Ni site and Ni-CeO2 interface, which help to improve the CO2 methanation performance. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation has been a promising method for producing propylene that has the potentials to meet the increasing global demand for propylene. However, owing to the restricted equilibrium conversion caused by the high endothermicity, even the Pt‐based catalysts, which exhibit high activity and selectivity, severely suffer significantly from coke formation and/or nanoparticle sintering at realistic reaction temperatures, resulting in a short catalyst lifetime. As a result, few innovative catalysts in terms of catalytic activity, selectivity, and stability, have been produced. In this Review, we focus on the characteristics of single‐atom‐like Pt sites for PDH and attempt to provide suggestions for developing highly efficient catalysts. First, we briefly describe the fundamental strategies. Following that, the remarkable catalysis is addressed by three different distinct sorts of state‐of‐the‐art single‐atom‐like Pt catalysts are discussed. Additionally, we present other promising catalyst design approaches that are not based on single‐atom‐like Pt catalysts, as well as future research challenges in this field. [ABSTRACT FROM AUTHOR]