Mesoporous SBA-15-based materials with tailored surface hydrophobicity and active sites were synthesized and evaluated as catalysts for the oxidative desulfurization of dibenzothiophene. Surface wettability was controlled by external silylation with hexamethyldisilazane, while Br & Oslash;nsted acid sites were introduced by grafting 3-(tri-hydroxysilyl)-1-propane sulfonic acid and molybdenum species were incorporated by incipient wetness impregnation. Nitrogen adsorption-desorption and X-ray diffraction confirmed preservation of the ordered mesoporous structure after modification. Water contact angle measurements revealed a pronounced increase in hydrophobicity for silylated materials. Spectroscopic analyses showed that molybdenum was predominantly present as dispersed Mo6+ species. Catalytic tests demonstrated that molybdenum-containing catalysts exhibited significantly higher activity than materials containing only sulfonic acid groups. The hydrophobically modified Mo/eHMDS/SBA-15 catalyst achieved nearly complete dibenzothiophene conversion under mild conditions (1 bar, 60 degrees C) and displayed improved stability compared to unmodified Mo/SBA-15-cal upon reuse. These results highlight the importance of surface hydrophobicity and active site accessibility in mesoporous catalyst design.

Mixed La-Zn, La-Nb, and Zn-Nb oxides were synthesized by mechanical mixing followed by calcination and characterized by XRD, TGA/DTA, UV-Vis, and FT-IR spectroscopy. The analyses confirmed the formation of mixed oxide systems with strong interactions between the component oxides. Acid-base properties determined by NH3-TPD and CO2-TPD showed that the LaZnOx(1:1) sample possesses the highest concentration of surface active sites and a balanced acid-base character. Catalytic activity was evaluated in the solvent-free Claisen-Schmidt condensation of benzaldehyde with acetophenone. Mixed oxides exhibited higher activity than the corresponding single oxides, with LaZnOx(1:1) achieving the highest chalcone yield (85% after 4 h of reaction) and excellent stability upon reuse. The superior performance of LaZnOx(1:1) is attributed to the synergistic interaction between La3 + and Zn2+ species, which generate cooperative acid-base sites on the surface. These results demonstrate the potential of LaZnOx mixed oxides as efficient and reusable bifunctional catalysts.

Bifunctional hybrid catalysts based on mesoporous SBA-15 silica and organosilanes bearing both acidic and basic groups were synthesized, characterized, and evaluated in the deacetalization-Knoevenagel condensation tandem reaction. Basic sites were introduced by grafting (3-aminopropyl)trimethoxysilane (AP) or imidazole (Im), while acidic sites were incorporated via 3-(trihydroxysilyl)propane-1-sulfonic acid (TPS) or trihydroxysilylethyl phenylsulfonic acid (TPhS). Water adsorption on the monofunctional catalysts surface was used to inhibit the deactivation of opposite active sites and to increase the efficiency of the second modifier loading. Variation in organosilane loading enabled systematic control of acid-base interactions. Comprehensive characterization (N2 adsorption-desorption, XRD, SEM/EDX, FT-IR, pyridine adsorption) revealed that amine groups in AP enhance the Br & Oslash;nsted acidity (BAS) of TPS through hydrogen bonding between NH2 and S=O species in AP and TPS, respectively, thereby improving catalytic performance. The enhancement in acidity strength was less for TPhS than for TPS. Catalytic tests demonstrated that L-TPS/AP/SBA-15 achieving 100% yield of benzylidenemalononitrile within 180 min. This superior activity is attributed to the synergy between strong BAS and an optimized base/acid molar ratio. When imidazole species were present near TPS and TPhS, they decreased the acidity strength of the-OH species in the sulfonic groups minimizing activity of the catalysts.

Mesostructured cellular foam (MCF) materials were modified with sulfonic acid (TPS) and molybdenum species to obtain dual-site catalysts containing both Br & oslash;nsted and Lewis acid sites. The physicochemical properties of the materials were characterized using N2 adsorption-desorption, XRD, SEM-EDX, XPS, pyridine adsorption combined with FT-IR and UV-vis spectroscopy. N2 physisorption revealed that TPS and molybdenum incorporation led to pore blockage and surface area reduction, particularly for Mo/MCF. XRD and SEM-EDX analyses indicated that molybdenum species are well dispersed, although TPS presence promoted localized accumulation, suggesting interactions between the two components. The catalysts were evaluated in dibenzothiophene (DBT) oxidation using H2O2. Mo/TPS/MCF exhibited superior activity, achieving 100% DBT conversion within 30 min at 80 degrees C, outperforming TPS/MCF and Mo/MCF. Moreover, the dual-site catalyst maintained high activity over five consecutive cycles, whereas Mo/MCF showed significant deactivation due to molybdenum leaching. These results demonstrate that TPS plays a stabilizing role for molybdenum species and enhances catalytic performance. The interaction between Br & oslash;nsted and Lewis acid sites in Mo/TPS/MCF offers a promising strategy for efficient and recyclable oxidative desulfurization catalysts.

Unsupported NbVOx and TaVOx mixed oxides as well as materials based on SBA-15 silica support were prepared, characterized and applied as catalysts for extractive catalytic oxidative desulfurization (ECODS) of dibenzothiophene (DBT). Properties of the materials obtained and the role of active centers and mesoporous support in the catalytic process were examined by low-temperature nitrogen physisorption, XRD, SEM-EDS, XPS, UV-Vis, chemisorption of pyridine combined with FT-IR spectroscopy as well as by test reactions, i.e. dehydration and dehydrogenation of 2-propanol and cyclization and dehydration of 2,5-hexanedione. The highest effectiveness of DBT removal from the oil phase, reaching up to 98 % within 15 min at 60 degrees C was shown by the supported materials prepared by impregnation method. The superior efficiency of DBT removal achieved for niobium containing samples could be related to its ability to interact with hydrogen peroxide towards the formation of reactive oxygen species.

Two different SBA-15 silicas with long and short channels, containing zirconium species, were prepared and used as supports for molybdenum additives. The resulting materials were characterized and tested as catalysts for extractive catalytic oxidative desulfurization (ECODS) of dibenzothiophene (DBT) using acetonitrile as a solvent and H2O2 as an oxidant. The synthesis procedure for the zirconium-containing silicas influenced both the zirconium loading and its distribution, i.e., whether it was incorporated into the framework or present in extra-framework positions. Additionally, the choice of support for molybdenum inclusion affected the amount of modifier loaded and its resistance to leaching, which collectively impacted the acidic and basic properties of the synthesized catalysts. The textural and surface properties of the materials were evaluated using low-temperature nitrogen adsorption/desorption, XRD, SEM-EDS, FT-IR-ATR, XPS, and UV-vis. The acidity and basicity of the samples were evaluated using FT-IR spectroscopy with pyridine adsorption/desorption and test reactions including 2-propanol dehydration/dehydrogenation and 2,5-hexanedione cyclization/dehydration. The catalytic activity was measured in ECODS. The Mo/ZrSBA-15-S catalyst demonstrated the best performance in DBT removal from the oil phase, achieving approximately 92% conversion of DBT within 120 minutes at 60 °C. This superior activity was attributed to the material's high acidity strength.

NbVOx mixed oxides were synthesized, characterized, and evaluated as catalysts for the extractive catalytic oxidative desulfurization (ECODS) of dibenzothiophene (DBT) using acetonitrile as a solvent. The mixed oxides were prepared using two different vanadium precursors: ammonium metavanadate and vanadium(IV)-oxy acetylacetonate. These precursors influenced the acidic/basic properties and the concentration of oxygen vacancies in the resulting catalysts. The texture and surface properties of the synthesized materials were analyzed using nitrogen adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy (UV-vis). Their catalytic activity was evaluated through the dehydration and dehydrogenation of 2-propanol and the ECODS of DBT. The mixed oxides synthesized with an excess of ammonium metavanadate (Nb:V = 1:2) demonstrated superior catalytic activity in removing DBT from the oil phase, achieving approximately 90% removal within 90 min at 60 °C. This enhanced activity is attributed to its higher acidity, greater concentration of oxygen vacancies, and the presence of vanadium peroxo ligands on its surface.

One of the current challenges is the reduction of sulfur emitted into the atmosphere, usually in the form of sulfur oxides generated by fossil fuel combustion. To achieve this goal, the sulfur content should be reduced in fuel. In this context, vanadium-containing materials based on SBA-15 mesoporous silica supports and two different sources of vanadium were prepared, characterized, and applied as catalysts for oxidative desulfurization (CODS) and extractive oxidative desulfurization processes (ECODSs). The novelty of this work was the comparative study of vanadium-containing materials in two desulfurization systems. The properties of the catalysts, the concentration and state of vanadium species, and their role in the catalytic process were examined by low-temperature nitrogen physisorption, XRD, UV-Vis, XPS, and chemisorption of pyridine combined with FTIR spectroscopy. The catalytic performance of the material prepared using ammonium metavanadate was superior to that of the catalyst obtained using vanadium(IV) oxide sulfate, which was explained by a higher concentration of vanadium species on the surface of the support and their lower oxidation state in the former. Both types of catalysts showed high activity and stability in the ECODS process.

The aim of this study was to get insight into the pathway of the acetaldehyde formation from ethanol (the rate-limiting step in the production of 1,3-butadiene) on Cu-SBA-15 and Cu-MnSBA-15 mesoporous molecular sieves. Physicochemical properties of the catalysts were investigated by XRD, N2 ads/des, Uv-vis, XPS, EPR, pyridine adsorption combined with FTIR, 2-propanol decomposition and 2,5-hexanedione cyclization and dehydration test reactions. Ethanol dehydrogenation to acetaldehyde (without and with oxygen) was studied in a flow system using the FTIR technique. In particular, the effect of Lewis acid and basic (Lewis and BrØnsted) sites, and the oxygen presence in the gas reaction mixture with ethanol on the activity and selectivity of copper catalysts, was assessed and discussed. Two different reaction pathways have been proposed depending on the reaction temperature and the presence or absence of oxygen in the flow of the reagents (via ethoxy intermediate way at 593 K, in ethanol flow, or ethoxide intermediate way at 473 K in the presence of ethanol and oxygen in the reaction mixture).

A source of Brønsted acid centers, generated on the surface of two mesoporous silica supports of different structures (SBA-15 and MCF), was 3-(trihydroxysilyl)-1-propanesufonic acid (TPS). The materials obtained were characterized and applied as catalysts for the oxidative desulfurization of dibenzothiophene (DBT) with hydrogen peroxide as a model ODS (oxidative desulfurization) process. The properties of the materials were examined via nitrogen physisorption, XRD (X-ray Diffraction) and elemental analysis showing the preservation of the support structure after modification with organosilane species. Due to the aggregation of catalyst particles in the reaction mixture, the SBA-15 based catalyst was not very effective in DBT oxidation. Contrary, TPS/MCF catalyst exhibited a very good activity (almost total conversion of DBT after 1 h in optimized reaction conditions) and stability in dibenzothiophene oxidation in mild reaction conditions.

Herein, the impact of cerium species loaded on mesoporous silica of MCF type on the state and catalytic activity of ruthenium species was studied. Up to 20 wt.% of cerium was incorporated on the silica surface, whereas the same 1 wt.% of Ru loading was applied. The samples prepared were examined by low temperature N2 adsorption/desorption, XRD, XRF, ICP-OES, XPS and H2 chemisorption. The catalytic activity of the materials obtained was investigated in the transformation of levulinic acid to γ-valerolactone. It was documented that the presence of Ce favored an increase in the dispersion of ruthenium species, which had a positive impact on the hydrogenation activity for up to 10 wt.% of Ce. Nevertheless, the highest cerium loading had a negative influence on the textural parameters of the support.

Copper-containing materials based on Ce- and Ca-Nb-mesocellular foam (MCF) silica supports are prepared, characterized and applied as catalysts for gas-phase reductive condensation of acetone to produce methyl isobutyl ketone (MIBK). The properties of the materials, the interaction of metal species, and their role in the catalytic process are examined by nitrogen physisorption, XRD, XPS, CO2 -TPD, H2 -TPR, and chemisorption of NO and pyridine combined with FTIR spectroscopy. A synergistic interaction of Cu2+ , Cu0 , and CeO2 species incorporated in the MCF support enable the Cu/Ce-MCF catalyst to yield 34 % of acetone conversion with over 90 % MIBK selectivity at 250 °C. Moreover, this high catalyst selectivity is maintained during operation for 24 h despite a decline in catalyst activity. The catalytic performance is superior to that of hydroxyapatite-supported Cu and similar previously reported Pd-containing catalysts.

The design of different bimetallic catalysts is an important area of catalytic research in the context of their possible applications in the cascade processes, meeting the requirements of the so-called green chemistry. In this study, such catalysts were obtained by the incorporation of magnesium species into spherical silica, which was in the next step covered with porous silica and modified with ruthenium species. The structure and chemical composition of the materials obtained were determined by XRD measurements, low temperature N2 adsorption/desorption, SEM, ICP-OES and XPS methods. The catalytic activities of materials obtained were tested in 2-propanol decomposition and hydrogenation of levulinic acid. The results obtained confirmed the successful coverage of nanospheres with porous silica. A much higher concentration of ruthenium species was found on the surface of the catalysts than in their bulk. The opposite relationship was observed for magnesium species. The modification of nanospheres with silica had a positive effect on the catalytic activity of the materials obtained. For the most active sample, i.e., Ru/NS/3Mg/NS, 49% of levulinic acid conversion in its hydrogenation process was reported with γ-valerolactone as the only product.

Herein, we report a study on the design of new palladium containing catalysts based on Ce- and Ca-Nb-mesocellular foam (MCF) supports for gas-phase conversion of acetone to methyl isobutyl ketone (MIBK). A comparison to other catalyst materials already described in the literature shows that the role of material structure (mesostructured cellular foams, hydroxyapatite or mesoporous aluminophosphate), acid-base character of the support, state of palladium species and the support metal dopants play important roles for the catalytic performance in the conversion of acetone to MIBK. Thus, the new catalytic system Pd/Ce-MCF with 11% of conversion and 94% of selectivity to MIBK (250 degrees C) is demonstrated to be more attractive in term of stability for the reaction over time than previously described in literature for Pd/hydroxyapatite.

Niobium containing SBA-15 was prepared by two methods: impregnation with different amounts of ammonium niobate(V) oxalate (Nb-15/SBA-15 and Nb-25/SBA-15 containing 15 wt.% and 25 wt.% of Nb, respectively) and mixing of mesoporous silica with Nb2O5 followed by heating at 500 °C (Nb2O5/SBA-15). The use of these two procedures allowed obtaining materials with different textural/surface properties determined by N2 adsorption/desorption isotherms, XRD, UV-Vis, pyridine, and NO adsorption combined with FTIR spectroscopy. Nb2O5/SBA-15 contained exclusively crystalline Nb2O5 on the SBA-15 surface, whereas the materials prepared by impregnation had both metal oxide and niobium incorporated into the silica matrix. The niobium species localized in silica framework generated Brønsted (BAS) and Lewis (LAS) acid sites. The inclusion of niobium into SBA-15 skeleton was crucial for the achievement of high catalytic performance. The strongest BAS were on Nb-25/SBA-15, whereas the highest concentration of BAS and LAS was on Nb-15/SBA-15 surface. Nb2O5/SBA-15 material possessed only weak LAS and BAS. The presence of the strongest BAS (Nb-25/SBA-15) resulted in the highest dehydration activity, whereas a high concentration of BAS was unfavorable. Silylation of niobium catalysts prepared by impregnation reduced the number of acidic sites and significantly increased acrolein yield and selectivity (from ca. 43% selectivity for Nb-25/SBA-15 to ca. 61% for silylated sample). This was accompanied by a considerable decrease in coke formation (from 47% selectivity for Nb-25/SBA-15 to 27% for silylated material).

Bifunctional catalysts-e.g., those with acidic and redox sites-are of particular importance, especially in the cascade processes, including the one-pot transformation of glycerol to acrylic acid. In this study, we explore one aspect of the preparation of a vanadium-containing catalyst, which can be further modified with 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS). The state of vanadium species loaded on mesoporous ordered silica of SBA-15 type was investigated before and after treatment with TPS, which can also be applied for the generation of acidic centers. Two vanadium sources, i.e., ammonium metavanadate and vanadium(IV) oxide sulfate, were applied to generate redox sites on SBA-15. The structure of materials obtained was analyzed using N-2 adsorption/desorption and XRD measurements. For the estimation of the amount of vanadium and characterization of its state, the following techniques were applied: ICP, UV-Vis, XPS, ESR and FTIR combined with pyridine adsorption. The treatment of vanadium containing SBA-15 with TPS was found to lead to the oxidation of V4+ to V5+ and the partial removal of vanadium species, leading to a decrease in the number of penta-coordinated vanadium species. These features should be taken into account in the design of bifunctional catalysts with vanadium-active centers and SO3H acidic sites coming from TPS.

Mesoporous silica of SBA-15 type was modified for the first time with 3-(trihydroxysiyl)-1-propanesulfonic acid (TPS) by post-synthesis modification involving microwave or conventional heating in order to generate the Brønsted acidic centers on the material surface. The samples structure and composition were examined by low temperature N 2 adsorption/desorption, XRD, HRTEM, elemental and thermal analyses. The surface properties were evaluated by esterification of acetic acid with n-hexanol used as the test reaction. A much higher efficiency of TPS species incorporation was reached with the application of microwave radiation for 1 h than conventional modification for 24 h. It was found that the structure of mesoporous support was preserved after modification using both methods applied in this study. Materials obtained with the use of microwave radiation showed a superior catalytic activity and high stability.

In this paper, the optimization of the synthesis of catalysts based on acidic mesoporous silica of the SBA-15 type by post-synthesis immobilization of 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS) under increased pressure up to 20 bar is reported. Sample structures and composition were examined by XRD measurement, low-temperature N2 adsorption/desorption and elemental analysis. The catalytic activities of the materials obtained were determined in both gas and liquid phase processes, i.e., by esterification of acetic acid and glycerol dehydration, respectively. The optimum pressure for modification leading to the highest number of acidic sites was found to be 10 bar. The final material was very active and stable in liquid phase processes; however, the stability in the gas-phase process was unsatisfactory due to the loss of sulphonic species from the catalyst surface.

Mesostructured cellular foams (MCF) were modified with calcium (20 wt%) and dopants (cerium and niobium; Ce/Nb = 2:2, 1:3, 3:1) using wetness impregnation. The samples obtained were used in model reaction, i.e. transesterification of ethyl butyrate with methanol. The application of dopants in non-equivalent weight loadings significantly increased the activity of Ca/MCF catalysts. This activity was dependent on the ratio of Ce to Nb in the sample which determined the oxidation state of cerium. The application of the equivalent amount of Nb and Ce resulted in the formation of cerium niobate that finally decreased the activity of Ca species.

Mesoporous silica of the SBA-15 type was used as a support for basic active centers generated by the incorporation of calcium species and (3-aminopropylo)trimethoxysilane (APTMS) or imidazole. The samples were characterized by low temperature N2 adsorption/desorption, XRD, XPS, FTIR spectroscopy, CO2-TPD, and elemental and thermal analyses. Calcium containing samples were analysed in 2,5-hexanedione dehydration and cyclization, while the activities of all the samples were examined in Knoevenagel condensation between benzaldehyde and malononitrile. It was demonstrated that the calcium species interacted with a silica support increasing the stabilization of organosilanes on the SBA-15 surface. A very high activity of the catalysts in Knoevenagel condensation indicated a synergistic interaction between calcium and the organic modifiers.