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A dual template-assisted approach for optimizing support structures to enhance catalytic efficiency in hydrotreating reactions is presented. Catalysts synthesized using activated carbon (AC) templates exhibited significantly higher activity in both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) compared to those prepared with starch (ST) templates. The unique porous architecture, characterized by well-distributed meso- and macropores, facilitated efficient access of bulky molecules to the active sites. On the other hand, while the reactivity in the selective opening of the naphthenic ring (SONR), which is indicative of hydrocracking functionality, was similar across all catalysts, those modified with Zr exhibited a slight improvement. The catalysts displayed bifunctional characteristics, and their performance was influenced by the amphoteric nature of the support and the specific ratios of active species on the surface. A clear correlation between catalytic activity, selectivity, and the distribution of active sites was established.

The uniformity of nanoparticles on supported catalysts is crucial for the understanding of their active sites. Compared to traditional synthesis methods, continuous flow method can effectively control the size of nanoparticles. Herein, we successfully synthesized a series of Pt/C catalysts with uniform Pt nanoparticles by continuous flow method and discriminated the active sites for 2-methylfuran (2-MF) hydrogenation. The activation energy and XPS characterization results indicate that the 2-MF hydrogenation is mainly governed by Pt geometric properties for Pt nanoparticles ≥ 3.05 nm. Based on the truncated cuboctahedron model, the dominant active sites for 2-MF hydrogenation are further discriminated as follows: the (111) facet for 2-MF conversion, the (100) facet for 2-pentanone (2-PN) formation, the edge site for 2-methyltetrahydrofuran (2-MTHF) formation and the corner site for 2-pentanol (2-POL) formation. For Pt nanoparticles < 3.05 nm, the reaction is mainly influenced by the electronic properties of Pt.

The reverse water-gas shift (RWGS) reaction is of great significance to convert CO₂ to valuable feedstocks. Reasonable design and preparation of catalysts is necessary to achieve high CO₂ conversion and CO selectivity. In this study, a series of Cu-Al based spinel catalysts were synthesized by coprecipitation-calcination method or A-site doped with active metal (Co, Zn, Mg, and Fe) for the RWGS reaction. The results indicated that the surface oxygen vacancies and crystal structure of CuAl₂O₄ can be regulated by calcination temperature. Remarkably, the CuAl-800 catalyst exhibits the highest CO₂ conversion rate (62.7 %) with 100 % CO selectivity at 500 °C. Excessive calcination temperatures (> 800 °C) resulted in a well-defined spinel structure, but decreased surface oxygen vacancies and CO₂ conversion rate. At calcination temperatures < 800 °C, surface oxygen vacancies increased, but the formation of CuO impurities which irreversibly converted to Cu₂O during reduction, decreased catalytic activity. Compared with Zn, Mg and Fe, Co doping can significantly improved the reactivity of CuAl₂O₄ catalyst in RWGS reaction at 500 °C, increasing the CO₂ conversion rate by 8 % while maintaining 100 % CO selectivity. The main reason is that Co doping not only effectively improves the integrity and stability of spinel structure of CuAl₂O₄, but also enhances its ability to dissociate and activate H species through interfacial sites of CuO-O_V-Cu_XCo_1-XAl₂O₄, thus further enhancing its catalytic conversion ability of CO₂ to CO. These results enrich the understanding of surface chemistry of CuAl₂O₄ spinel and lay an important theory foundation for design of spinel-based catalysts for RWGS reaction.

The catalytic performance of a series of dendritic mesoporous silica nanoparticles (DMSNs) containing vanadium, featuring a unique central-radial pore structure with large pore size and highly accessible surface areas, was investigated for the selective oxidation of propane. The one-pot method allowed to synthesize vanadium-containing dendritic mesoporous silica nanoparticles (V-DMSNs). V/DMSN catalysts with similar V-loading were prepared using the impregnation procedure for comparison. These V-containing DMSNs materials served as catalysts for the selective oxidation of propane, utilizing a mixture of N₂O and O₂ as a mild oxidant. The nature of vanadium oxide species was characterized using Raman spectroscopy, diffuse reflectance ultraviolet–visible spectroscopy (UV–vis DRS), and temperature-programmed reduction with hydrogen (H₂-TPR). Additionally, the acidic sites' nature and strength were estimated based on the Fourier transform infrared spectroscopy (FTIR) of adsorbed CO and pyridine. Spectroscopic measurements revealed that vanadium predominantly exists as an isolated or low-polymeric VO_x species in one-pot synthesized catalysts. At the same time, impregnation resulted in more polymerized or bulk forms of vanadia, characterized by lower accessibility. Textural, SEM, and TEM results indicated that the characteristic dendritic features of DMSNs were maintained after vanadium incorporation, regardless of the preparation procedure. Propane oxidation led to a conversion of 64 %, accompanied by a propene selectivity of approximately 60 % and resulting space-time yield of 77 g_C3H6 kg_cat⁻¹ h⁻¹. Furthermore, propene oxide was identified among the products, with a space-time yield ranging from 3 to 11.5 g_PO kg_cat⁻¹ h⁻¹. Notably, the maximum turnover frequency (TOF) values for propene and propene oxide formation were 7.5 h⁻¹ and 1.45 h⁻¹, respectively. V-DMSNs catalysts exhibited superior catalytic performance in propane oxidation. The one-pot synthesized catalysts demonstrated higher stability over time on stream and lower selectivity towards CO_x. This study introduces a novel multifunctional catalyst that presents the potential for co-production of propene and propene oxide while utilizing N₂O.

In the context of the energy transition scenario, effective sulfur management is crucial. Enhancing the quality of extra heavy crude oil (EHCO) through catalytic processes, specifically hydrotreatment, is essential for reducing pollutant emissions like SOx into the atmosphere. Traditional hydrotreatment, utilizing MoS₂-based catalysts typically on Al₂O₃ support, faces challenges with EHCO due to its elevated S and N content, which hampers catalyst efficiency. Metal carbides and nitrides exhibit promising electronic structures that confer resistance to deactivation in the presence of heteroatoms. This study compares the catalytic performances of Fe-promoted Mo sulfides, carbides, and nitrides (FeMoS(C,N)) in the thiophene hydrodesulfurization (HDS) reaction, serving as a model molecule for sulfur removal. Subsequently, we investigate the upgrading of a Venezuelan EHCO in terms of pollutant reduction, API gravity, and feedstock aromaticity. Catalysts were prepared from oxide precursors, varying the (Fe/(Fe+Mo)) atomic ratios (x = 0.00, 0.10, 0.33, 0.50, and 1.00), employing a temperature-programmed reaction protocol. Catalytic upgrading of EHCO was conducted in a stirred batch reactor, and the results were compared with a commercial CoMo-based catalyst. FeMoC(N) outperformed the commercial catalyst in sulfur removal. The elemental composition and nitrogen content of the feed remained constant; however, the sulfur content of asphaltenes decreased. Furthermore, the API gravity of crude oil increased when employing FeMoS and FeMoN catalysts, except with FeMoC, possibly linked to dealkylation reactions and the enrichment of lighter fractions with alkanes. FeMoN increased asphaltene aromaticity, while FeMoC decreased it. These results highlight the promise of FeMoC(N) as catalysts for HDS and upgrading heavy feedstocks.

Furfural condensation with cyclopentanone has been studied over calcium oxide as a catalyst exploring the influence of temperature, cyclopentanone to furfural ratio, furfural purity, and the effect of a stabilizer. This research delves into the synthesis of aviation fuels from renewable biomass through aldol condensation, focusing on the reaction kinetics. The comprehensive study assesses the previously mentioned factors to optimize the conditions for maximum yield and selectivity towards the desired product. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed significant changes in the catalyst structure after the reaction, influencing its efficiency. The preferred conditions were determined to be the furfural to catalyst mass ratio of 10:1, cyclopentanone to furfural molar ratio of 15:1, stirring speed above 800 rpm and temperature of 130 °C, resulting in high catalytic activity. Furthermore, it was found that addition of a stabilizer enhanced the reaction rate and selectivity towards the desired products, which could be due to changes in the acidity of the reaction media. This study lays the groundwork for further exploration into the production of sustainable jet fuels from the aldol condensation of smaller biomass-derived compounds, highlighting the importance of the reaction conditions to achieve high conversion, product yield and selectivity.

Across the last years, substantial efforts were done to understand the limitations of the oxygen evolution reaction (OER) catalysts and to develop robust ones such as to solve the efficiency problem in water splitting. Fundamental understanding represents a pathway towards designing superior catalysts. In this direction, several descriptors (η_TD, ESSI, G_max(η)) have been derived based on the adsorption energies of the OER intermediate moieties (∆E_HO*/∆E_O*/∆E_HOO*) for faster screening of the materials. A universal scaling between the adsorption energies of HO* and HOO* was established for a wide range of materials and in many cases was shown to govern the minimum theoretical overpotential. On the other hand, the scaling between the adsorption energies of HO* and O* fragments have a large scattering along the trendline. In this work we derive five trends for the O* adsorption energies based on theoretical overpotential intervals, using data collected from the published studies employing DFT calculations for OER. It is shown that the best materials have an adsorption energy for HO* placed within a limited interval, yet sufficiently large for a pool of promising catalysts (-0.5,1.5 eV), and that the adsorption energies of O* scales with that of HO* at a slope of one and an intercept of 1.81 eV. Furthermore, a decrease of the intercept for the scaling between HOO* and HO* from 3.14 (valid for all data analyzed) to 3.03 eV is found. For three of the other four trends, the slope of the adsorption energies of O*/HO*scaling is one with intercepts closer either to HOO* (2.2/2.78) or to HO*(1.43/0.78) adsorption energies. For each set of data, the scaling between HOO* and HO* adsorption energies varies from 3 to 3.37 eV. Separately, the trends for O* adsorption energies were analyzed for the TiO₂(110) semiconducting rutile surface when doped with transition metals and modified (i) with HO* or H* co-adsorbed fragments that act as charge donor/acceptor moieties or (ii) when the surface was provided with an excess or a lack of electrons. The analysis was performed using the data collected from the published literature, supplemented by additional calculations. Clear trends based on the amount of charge were obtained when standard GGA functionals were used. An understanding for the origin of the large variation of the oxygen adsorption energies for the systems that have similar adsorption energies for the HO*/HOO* is provided. However, when the Hubbard corrected GGA functional is used, some trends change. Clearly, it is still a challenge describing accurately and in a cost-effective manner the adsorption of OER moieties on the undoped or doped transition metal oxides, especially for O*. A strategy to get further insight into the origin of large variations of oxygen adsorption energies for the materials that have similar adsorption energies of HO* and HOO* is discussed.

This study explores the selective ketonization of acetic acid on TiO₂, ZrO₂, and HfO₂ catalysts, focusing on the vapour phase conversion of acetic acid and its subsequent conversion into longer-chain aliphatic and aromatic oxygenates, aligning with kerosene fuel requirements. Achieving optimal acetic acid conversion at a WHSV of 4 h⁻¹ and temperatures above 400 ^◦C, the process yields a variety of products, from anhydrides to polyaromatic compounds, with acetone and acetaldehyde identified as primary outputs. The study employs in-situ infrared (IR) analysis to unravel the deactivation mechanisms of the catalysts, discovering that ZrO₂, despite its higher initial reaction rate compared to TiO₂ and HfO₂, undergoes faster deactivation due to the accumulation of monodentate and bidentate carboxylates, which block active sites. This contrasts with TiO₂, which demonstrates enhanced stability through the partial hydrogenation of bidentate carboxylates, pointing to a viable strategy for catalyst regeneration. The incorporation of in-situ IR study provides crucial insights into the surface interactions and deactivation pathways, informing the design of more effective catalysts. These findings underscore the importance of enhancing surface hydrogenation capabilities to develop more active and stable catalysts for ketonization reactions, significantly advancing the field of catalysis and biomass conversion with implications for the efficient production of valuable chemicals and alternative fuels.

Metal-doped hexagonal tungsten oxide bronzes (h-WVO_x and h-WNbO_x) and metal-doped orthorhombic molybdenum oxide bronzes-M1 type (MoVO_x, MoVTeO_x and MoVTeNbO_x) have been synthesized hydrothermally and heat-treated at 400, 550 or 600 °C in N₂. The catalysts were characterized by several techniques and tested in the one-pot aerobic transformation of glycerol at 350 °C. From all of them, h-WNbO_x resulted as the most selective to acrolein (80 % yield), whereas both h-WVO_x and MoVTeNbO_x were more effective to acrylic acid (with a yield lower than 25 %). Subsequently, a double-bed reactor comparative study was conducted, with h-WNbO_x acting as the first catalytic bed. In this case, the yield to acrylic acid decreased as follows: MoVTeNbO_x > MoVTeO_x > MoVO_x > h-WVO_x. IR spectroscopy of acrolein adsorbed on these catalysts allows to explain the catalytic performance of these catalysts.

NiS_X stands out in the electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) due to the favorable conductivity and diverse chemical composition. However, NiS_X usually exhibits few exposed active sites and poor charge transfer kinetics. Moreover, during the electrochemical oxidation of HMF, the conductivity of the catalyst would decrease rapidly with the formation of oxidized Ni species, leading to a rapid decline in catalytic performance. Therefore, a series of NiS_X/carbon black (CB) hybrids (NiS_X/CB-n) were synthesized via a one-step solvent hydrothermal method in which NiS_X displayed a large cubic block structure assembled from small nanosheets. Among the prepared catalysts, NiS_X/CB-2, with the optimal amount of introduced CB, exhibited superior electrocatalytic activity for the oxidation of HMF, achieving 100% HMF conversion, 98% FDCA yield, and 100% Faradaic efficiency at 1.45 V (vs. RHE). The outstanding electrocatalytic activity of NiS_X/CB-2 was attributed to the suitable CB doping, which not only enhanced the conductivity of catalyst but also separated the small nanosheets, preventing the formation of densely packed NiS_X structure and increasing the specific surface area of catalyst, thereby exposing more active sites and improving the availability of material. Furthermore, the formation of C-S bonds facilitated charge interactions between NiS_X and CB, promoting the transfer of charges during the electrolysis process and enhancing electrocatalytic kinetics. Open circuit potential tests demonstrated that the introduction of CB also strengthened the adsorption capacity of catalyst for HMF, further benefiting its electrocatalytic activity.