Applied Catalysis A: General最新文献

Photoelectrochemical (PEC) technology seamlessly integrates and optimizes the merits of photocatalysis and electrocatalysis, facilitating charge separation and enhancing solar conversion efficiency. It stands out as a promising approach for CO₂ treatment. GaN as III-Ⅴ semiconductor, has garnered substantial attention in the realm of PEC CO₂ reduction reactions (RR). In this study, GaN and In/GaN micro-rods were prepared via straightforward hydrothermal synthesis. Attaining a current density of approximately 10 mA/cm² and CO Faradaic Efficiency (FE) of ∼45 % at −0.75 V_RHE (Reversible Hydrogen Electrode, RHE), In/GaN exhibited exceptional stability over a 2 h PEC CO₂ RR. The introduction of In into GaN significantly augmented CO₂ adsorption capacity and light harvesting. Additionally, Density Functional Theory (DFT) calculations elucidated that In-doped GaN can diminish the adsorption of intermediate CO, favoring subsequent CO desorption. Furthermore, the N-vacancy increased with In doping, resulting in a rise in the number of unpaired electrons, facilitating carrier transport. Herein, vibration energy harvester was introduced to drive CO₂ RR, marking a significant advancement in development of PEC CO₂ RR for future green energy applications.

To improve the CO₂-to-light olefin process in terms of economics, efficient catalysts are essential to maximize the yield. Our research was carried out on FeAlCuK, which is still considered as a benchmark for olefin formation via CO₂ Fischer-Tropsch synthesis (FTS). Nevertheless, the effect of various activation conditions on the formation of desired active species and final activity of this catalyst has not been described in literature to date. We studied the pretreatment by varying both the reduction gas and temperature. The catalyst was pretreated with pure H₂ or synthesis gas (H₂/CO = 3) to identify the bulk and surface species formed in each case. We demonstrate that the FeCuAlK catalyst should be activated in a H₂/CO atmosphere at 250 °C for 4 h before the test at typical FTS reaction conditions to reach maximum productivity. The reduction with H₂/CO led to the formation of active Fe₅C₂ and Fe₃O₄ phases producing a high fraction of light olefins at higher CO₂ conversion. The role of promoters K and Cu was also investigated. Selectivity for desired C₂-C₄ olefins increased by 10 % compared to catalysts which were used directly in FTS without preliminary activation. Characterization with ex and in situ powder X-ray diffraction, Raman spectroscopy, and XPS after each activation treatment as well as Mössbauer spectroscopy revealed a strong impact of gas nature on the phase composition which was correlated with the performance.

A series of Ruthenium-Stannum bimetallic catalysts were prepared using the isovolumetric impregnation method and investigated for the liquid-phase hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to its corresponding 2,2,4,4-tetramethyl-1,3-cyclobutanediol. The effects of the reaction temperature and pressure, fluorine-modified alumina, reaction solvent, and catalyst particle size on the catalytic performance were discussed. The optimum reaction conditions were obtained with a temperature of 80 ℃, a hydrogen pressure of 4.0 MPa, and a reaction solvent of tetrahydrofuran. In addition, characterization techniques, such as BET, XRD, TEM, NH₃-TPD, and Py-IR, showed that the active component nanoparticles were effectively introduced into the alumina carriers, and the alumina was modified by a low concentration of NH₄F solution (0.05 mol/L), which ensured that the complete conversion of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was obtained while maintaining a selectivity of over 95 % for the 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

The synergistic coupling of photocatalytic hydrogen evolution and selective organic matter conversion is extremely attractive, as clean fuel and high value–added chemicals can be produced simultaneously with light as the sole energy input. Herein, we developed a dual functional photocatalyst (ZnIn₂S₄/Ni) for efficient photocatalytic conversion of benzyl alcohol into benzaldehyde with simultaneous hydrogen production. Consequently, ZnIn₂S₄/Ni displayed a top-level benzaldehyde and H₂ evolution rate even in aqueous media. The yield of benzaldehyde reaches 19.3 mmol/g/h, which is 33 times higher than that of naked ZnIn₂S₄ and even exceeds that of precious metal systems (Pt, Pd, Ru). Here, Ni site not only acted as an effective co–catalyst for charge separation, but also played an important role in accelerating the α–C–H bond cleavage during the dehydrogenation of benzyl alcohol. This work provides a cost-effective and green reference path for the efficient conversion of solar energy to chemical energy.

Adding Zn to the ZSM-5 zeolite effectively increases the aromatic selectivity in the methanol-to-aromatics (MTA) process. The formation of metal-derived Lewis acid sites promotes the dehydrogenation but at the cost of a rapid deactivation of the catalyst by coke, due to the increased aromatic formation. In this work, we impregnated a Zn-modified catalyst (2 wt%) with variable contents of Ca (0.02 and 0.5 wt%) and evaluated their kinetic behavior in the MTA and ethane dehydrogenation reactions. The results proved the superior performance of the Zn(2)Ca(0.02) catalyst due to a synergistic effect between the two metals. The Ca ions limit coke formation from excessive aromatization, increasing catalyst stability and removing Zn clusters, resulting in a recovery of Brønsted acid sites (BAS) active for the formation of light aromatics. Combining these effects results in a more efficient and viable catalyst for aromatic production from methanol.

The effectiveness of a Ru-Fe/SiO₂ catalyst, which exhibits excellent propane dehydrogenation with H₂S co-feeding, was verified for the dehydrogenation of various lower alkanes. When the dehydrogenation characteristics of C2–C4 alkanes were evaluated under H₂S co-feeding, the Ru-Fe/SiO₂ catalyst exhibited a high dehydrogenation activity in all cases. However, a significant degradation tendency of the catalyst was observed when lighter alkanes with smaller carbon numbers were used as the feedstock. The deposition of coke (carbon) and solid sulfur and the reduction of Fe species were identified as the main factors responsible for catalyst degradation. To further evaluate the factors affecting catalyst degradation, the effect of co-feeding H₂ with the gas feedstock on the catalyst performance was investigated. The reaction stability improved significantly with the co-feeding of H₂ during ethane and propane dehydrogenation reactions. This outcome is attributed to the smooth reduction and removal of the carbon accumulated on the catalyst surface, which is the main cause of catalyst degradation.

Metal-Organic Frameworks (MOFs) materials with unique properties have attracted much attention in various fields. However, the limited number of active sites and the time-consuming synthesis process hinder their widespread application. Herein, this work demonstrates the first preparation of highly efficient and stable MOF (Fe-MOF-U) catalysts with enhanced specific surface area, morphology and active sites, through ultrasonic-assisted solvothermal method for oxygen evolution reaction (OER) electrocatalysis. The results show that the crystal size of Fe-MOF-U decreases significantly, and the specific surface area and pore size increase. In addition, many oxygen vacancies are produced in the crystal, making the reaction intermediates easier to form and thus improving the catalyst's oxygen evolution performance. The overpotential of Fe-MOF-U catalyst at 10 mA cm⁻² is 221 mV, which is lower than that of the conventional solvothermal synthesized Fe-MOF-S (237 mV). Furthermore, the turnover frequency of the Fe-MOF-U catalyst is 3.32 s⁻¹ at the overpotential of 300 mV, which is 5 times higher than that of Fe-MOF-S (0.70 s⁻¹). In situ Raman and methanol molecular probe tests indicate a weakened adsorption of *OH on the Fe-MOF-U surface. DFT calculations are consistent with the characterization results, both proving that the ultrasonic-assisted solvothermal method can generate specific oxygen vacancy (μ₃-O defect) in Fe-MOF-U which improved OER performance. This study provides a new idea for the morphology controlling and defect introduction of MOF and a new approach for its application.

This study aims to investigate biofuel production from biomass-derived bio-oil and examine the impact of selecting different active metals, their quantities, and synthesis procedures on biofuel selectivity. For this purpose, alumina-supported catalysts containing Zr, Co, and W were prepared using the wet impregnation method. Some physical and chemical properties of the synthesized catalysts were determined through XRD, BET, SEM/EDS, ICP-MS, TGA-DTA, and DRIFTS analysis. The activity test studies revealed that the 5Co-10Zr@MA catalyst, prepared by co-impregnation, exhibited the highest bio-oil conversion (95 %) and the highest iso-paraffin selectivity (93 %). XRD analysis indicated that this catalyst possess the CoAl₂O₄ structure, indicating the formation of an alloy between alumina and cobalt, thereby enhancing catalytic activity. The reusability tests showed that the 5Co-10Zr@MA catalyst maintained its activity over a time of 3 h. Consequently, the utilization of mesoporous alumina-supported bimetallic catalysts has proven to be successful in the production of biofuels, achieving high conversion and selectivity.

This study introduces a novel Cu-based catalyst for the selective hydrogenolysis of glycerol to 1,2-propanediol, synthesized by impregnating mesoporous γ-alumina with Cu and Fe. Characterization was performed using various analytical methods, and tests were conducted in a tubular continuous reactor under specific conditions. Iron was found to have multiple modifying effects, influencing the modification of Cu clusters on the catalyst surface and the radial Cu concentration profile inside the particles. A low Fe/Cu ratio resulted in an almost egg-shell Cu profile, whereas higher Fe levels produced a more uniform distribution. Interestingly, minor Fe additions led to larger Cu clusters, while higher amounts resulted in smaller clusters and decreased glycerol conversion. The effect of Fe on Cu clusters size, acid sites concentration, and Cu radial profile, as well as the influence of these parameters on the glycerol conversion and selectivity towards 1,2-PD are discussed in this study.

Rhodium-based manganese oxide frameworks were explored as a prototype for carbon dioxide reactive capture and conversion. Three-dimensional frameworks of MnOx were utilized as support structures to isolate Rh metal centers. V, Na, and Zn were introduced as counterions to stabilize the structure and for their beneficial effect as promoters. With this multicomponent catalyst, Rh active centers with MnOxs and varied counterions, we were able to selectively tune the catalytic performance of the material via the choice of counterion and structure of the host material. With cryptomelane-type tunnel manganese oxides octahedral molecular sieve (OMS2), we found that Rh-V-OMS2 was highly stable even after 48 hours on stream with a reaction rate of around 1.5×10⁻⁴ mol CO₂/g_Rh/s, surpassing the net reactivity of other initially more active combinations. Furthermore, during CO₂ hydrogenation, in situ XAFS showed that single Rh atoms nucleated into nanoparticles/ sub-nanometer clusters with a coordination number of 5.5 or less. Our finding of the correlation between the reaction rate and particle size offers the potential for enhanced control over the reaction rate by tuning particle size. Our activity study with control experiments demonstrates that the activities of the catalysts are proved due to the unique metal support interaction offered by the Rh-X-MnO.