Introduction Based on the structural--electronic structure of MOFs, it can be assumed that these materials can be unique macromolecular adsorbents that can form intermediates with organic reagents and then turn them into the final products of chemical transformations.

Methods PXRD, IR-spectroscopy, thermogravimetric analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and catalytic units were used in this study.

Results The metal--organic framework structures of Cu-MOF and Gd-MOF were synthesized using nitrates of metals and benzene-1,3,5-tricarboxylic acid, an organic ligand. Replacing copper ions with gadolinium ions in MOFs increases the efficiency of the process. The conversion of propane at 400°C increases to 8.0 % for the Cu-MOF catalyst and to 20% for the Gd-MOF catalyst. At this temperature, there is no non-catalytic reaction. Synthesized metal--organic frameworks are porous materials with a specific surface area of 319 m²/g for Cu-MOF and 551 m²/g for Gd-MOF. The surface morphology of synthesized materials was studied using SEM. The resulting particles have the shape of an octahedron.

Conclusions These materials have demonstrated high catalytic activity in the process of propane dehydrogenation at a temperature of 400°C. Propane conversion using Gd-MOF increased to 20.0 %, and selectivity for light olefins (ethylene and propylene) increased to 71.0 %, while when using Cu-MOF, propane conversion increased to 8.0 %, and light olefin selectivity by 69.0 %. For Gd-MOF, there was no decrease in the efficiency of its operation due to the deposition of amorphous carbon on the surface of the catalyst. This result allows us to predict the significant service life of this catalyst.

Introduction
Currently, much attention is paid to the development of new technologies and increasing the efficiency of existing processes for converting natural gas into “light” olefins, of which propylene is of greatest interest.
Methods
Synchrotron X-ray diffraction (s-XRD), Raman scattering, inductively coupled plasma atomic emission spectroscopy, low-temperature nitrogen adsorption, and a catalytic cracking unit were used.
Results
To obtain the catalyst, molybdates Ln₂(MoO₄)₃ were synthesized according to the developed method using rare earth nitrate and sodium molybdate dihydrate Na₂MoO₄×2H₂O. Lanthanum, praseodymium, neodymium, and ytterbium molybdate catalysts for propane dehydrogenation increased feedstock conversion by 40.0% without recycling and the process yield of target propylene by 33.0% while maintaining high propylene selectivity (70.0%) and total selectivity for "light" olefins (83.0%). Over 8 hours of continuous operation, the catalyst activity decreased by less than 1.0%. The reaction activation energy decreased from 114 kJ/mol to 91.0 kJ/mol. A decrease in catalyst activity (about 15.0%) was observed after 200 hours of continuous operation. To regenerate the catalytic systems, it is proposed to treat their surface with an air flow at 573 K for 10 hours.
Conclusions
The formation of the mixed structure of Ln₂(МоO₄)₃ leads to a shift in the degree of conversion to the region of catalytic temperatures of 700-900 K with a predominance of the dehydrogenation reaction of 80%. It was revealed that the steric factor prevails over the energetic one in the process of propane destruction, making the reaction of ethylene formation stereospecific, with the achievement of a maximum in ethylene selectivity of 83%. It was determined that the non-isovalent substitution of K⁺- leads to the deformation of the crystal structure and blocking of the most energetic Lewis centers, which leads to an insignificant decrease in propylene selectivity from 83% to 81% with a decrease in surface carbonization at high cracking temperatures.

Current trends aimed at reducing the environmental impact of human activity have led to the need for the development of efficient and sustainable catalytic systems for the methane dry reforming process. Moreover, the by-products of the primary greenhouse gases represent valuable raw materials for the petrochemical industry. These materials, which meet the requirements for activity, selectivity, and thermal and chemical stability, are complex oxides with a perovskite structure.

Gd(Co,Mn)O₃ complex oxides were prepared by the sol–gel method with citric acid and characterized by X-ray diffraction and Fourier-transform IR spectroscopy. Their oxygen non-stoichiometry was also investigated by iodometric titration. The catalytic properties of the samples were studied in a flow reactor at atmospheric pressure with a volume flow rate of 0.9-1.0 L/h and a CO₂:CH₄ ratio of 1:1.

It has been shown that the addition of manganese to the anionic sublattice of a complex oxide inhibits the conversion of carbon dioxide into methane. In samples containing manganese, the reaction temperature is shifted towards lower values, with X_50% conversions of CH₄ and CO₂ occurring at almost 300 K lower than in unsubstituted samples of cobalt. The synthesis gas ratio does not reach stoichiometric levels, which may be due to an increased side reaction of CO₂ reduction. Despite the lower catalytic activity, less surface carbonization was observed in complex oxides containing manganese. The formation of trace amounts of hydrocarbons suggests that the adsorption of methane on manganese atoms occurs mainly through the formation of CH_x species. These results suggest that catalytic systems based on Gd(Co,Mn)O₃ have potential for the production of synthesis gas through the conversion of carbon dioxide into methane.

Biodiesel is a mixture of fatty acid methyl esters (FAMEs) and is a biodegradable and renewable fuel, produced from fat sources mainly composed of triglycerides. The use of ionic liquids (ILs) in biodiesel catalytic production has been studied mainly in the ecological field, as it allows a high recycling efficiency. Choline (2-hydroxyethyl trimethylammonium)-based ILs have received attention due to their biocompatibility characteristics and potential for various industrial applications. Specifically, choline hydroxide (ChOH) represents a promising option. This work's objective is the optimization of the methyl transesterification reaction conditions using commercial and waste sunflower oil (WSO) as raw material and ChOH as a catalyst, assessing the possibility of recovering the catalyst between reaction cycles. Therefore, biodiesel production was carried out on heating plates with temperature control and with magnetic stirring, using methanol reflux. After phase separation, centrifugation was used to enhance biodiesel recovery. Reaction conversion was assessed by acidity drop determination, and the biodiesel FAME content was determined by GC-FID, through a procedure in accordance with EN 14103, using methyl heptadecanoate as the internal standard. IL recovery was carried out by solvent extraction with water-based binary systems, followed by an FTIR analysis of both phases for ChOH detection, and a comparison with initial IL samples. Optimal conversions, determined by acid value (AV) reduction or by biodiesel FAME mass content, were obtained using a 4%wt. catalyst load, oil/methanol molar ratio of 1:8, duration of 1 h, and temperature of 65 °C. The products’ AV for WSO showed a significant reduction relating to the raw material AV (6.14 mgKOH/g). For the reactions with commercial sunflower oil (AV close to 0.20 mgKOH/g), the biodiesel phase AV remained low. ChOH recovery, performed with n-butanol/water and ethyl acetate/water systems, proved to be inefficient under the conditions tested. FTIR analysis showed the presence of ChOH in both liquid–liquid extraction phases.

Biodiesel consists of a mixture of fatty acid methyl esters (FAMEs) and is produced by processing vegetable oils or animal fats. Oil sources, not competing with the food market, such as waste cooking oils (WCOs), can be used, and ionic liquids (ILs) are promising catalysts, since they promote esterification/transesterification reactions to biodiesel. The objective was to study biodiesel production using 1-methylimidazolium hydrogen sulphate IL ([HMIM][HSO4]) as a catalyst in esterification/transesterification reactions with methanol, for oleic acid (OA) and simulated high acidic oils, in mixtures of 40%(w/w) OA to 60%(w/w) WCO. The IL recovery procedure was also assessed using water as solvent. Biodiesel production was carried out on two heating plates with automatic temperature control and magnetic stirring (IKA, digital C-MAG HS4 model, and VWR, VMS-C4 model). A centrifuge (SIGMA, model 2-4) was used for phase separation. Samples were dried in an oven (CIENTIFIC, series 9000) and all masses were measured on an analytical balance (accuracy: ±0.0002g and maximum: 210g; AE, ADA 210/C). FAME content was determined by GC (SHIMADZU, Nexis GC 2030), with FID, an AOC-20i autoinjector and an Optima BioDiesel F capillary column (30mx0.25mm). Analyses were carried out by FTIR with a Perkin Elmer equipment, Spectrum Two, and an ATR universal accessory. Reaction conditions were as follows: 65°C, 4 hr, raw-material/methanol molar ratio 1:10, and 10%(w/w) IL load. Using OA as the raw material, an acidity drop conversion of 81.2% was obtained. After seven reaction cycles, the conversion dropped to 69.4%, while the FAME content decreased from 64.7% to 57.5%. For WCO, a conversion of 45.6% was obtained and after nine reaction cycles it decreased to 27.2%, while the biodiesel FAME content decreased from 24.1% to 14.0%. The FTIR correlation between initial and final IL samples was 99.3% for OA and 90.0% for WCO, showing that the recovery method is efficient. For these operating conditions, IL only promotes esterification reactions.

The production of light olefins through carbon oxide hydrogenation represents a promising alternative to fine organic synthesis, where ethylene and propylene are crucial components of the synthesis chain for valuable products. This research focuses on iron-containing Gd_1-xA_xFeO₃ (A=Ca, Sr, Ba) complex oxides as catalysts for simulated bio-syngas hydrogenation. Ca/Sr/Ba-promoted GdFeO₃ catalysts were prepared by the sol–gel method and characterized by BET N₂-physisorption, X-ray diffraction, and Fourier-transform IR spectroscopy. Their acid–base properties and oxygen non-stoichiometry were also investigated. Their catalytic performances were evaluated in a fixed bed reactor. Ca/Sr/Ba increase the CO conversion rate and ethylene–propylene selectivity, while they decrease the production of methane. A very small amount of A additive can help to enhance the performance of GdFeO₃ catalysts in the hydrogenation of carbon oxides. It is worth noting that Ca/Sr/Ba can promote the occurrence of oxygen vacancies and the growth of both acidic and basic centers, and this affects the catalytic properties. With the modification of the Sr promoter, CO conversion and light olefin selectivity both increase due to the increase in the number of catalytically active sites, and they reach their highest values at a silver content of 0.01 wt.%. As a result, Sr can be seen as an attractive candidate to replace more expensive noble metal promoters, such as Pt and Re, under industrial conditions.

The results presented here offer a roadmap for tailoring the distribution of bio-syngas hydrogenation products to specific desired outcomes by adjusting the composition of the catalyst. To fully understand the active sites and phases and to unravel the underlying mechanisms, further in-depth investigations are required given the intricate nature of perovskite-based catalytic systems.

Funding: This work was funded by the Russian Science Foundation, grant № 24-29-00341, https://rscf.ru/project/24-29-00341

Polymer-supported catalysts are versatile compounds for the synthesis of different molecules.¹ Among polymers, polysiloxanes possess good film-forming abilities, flexibility, a wide range of working temperatures (from –123 to +250 °C), and UV resistivity.² These properties make them desirable candidates for catalytic application in homogeneous and heterogeneous catalysis. The functionalization of polysiloxanes with platinum-group metal complexes opens up new opportunities for usage of the resulting metal–polymer compounds for catalytic hydrosilylation and dehydrocoupling reactions for platinum-containing complexes and for carbon–carbon cross-coupling reactions for palladium-containing polysiloxanes. Considering the nature of the catalytic reactions (homogeneous or heterogeneous), homogeneous catalysts usually demonstrate high catalyst activity and a short reaction time, but they contaminate the product of the reactions with metal and do not allow for the recovery and reuse of catalysts several times. This is crucial, taking into account the high price of platinum-group metals. Alternatively, heterogeneous catalysts can be used. Despite some of its limitations such as lower reaction rates and yields, heterogeneous catalysts are easier to recover and reuse several times.³

Thus, the aim of this study is to synthesize polysiloxanes that have functionalized using platinum and palladium complexes. We synthesized platinum-functionalized polysiloxane (Pt-PDMS) via Cu(I)-catalized azide-alkyne cycloaddition between a palladium C,N-cyclometalated complex and (3-azidopropyl)polysiloxane. Its activity was investigated in Si–O dehydrocoupling reactions⁴. Palladium-containing polysiloxane (Pd-PDMS) was synthesized in a similar way to the Pt-PDMS method. The catalytic activity of Pd-PDMS was examined in carbon–carbon cross-coupling reactions.³ The resulting catalysts demonstrated high catalytic activity in the performed reactions, without yield loss after several catalytic cycles. The usage of both Pt-PDMS and Pd-PDMS allows one to recover and reuse catalysts easily.

The authors acknowledge St Petersburg State University for a research project grant, with the number 95408592.

References

1. Munirathinam, R.; Huskens, J.; Verboom, W. Supported catalysis in continuous‐flow microreactors. Synth. Catal., 2015, 357(6),1093-1123.
2. Mark, J.E.; Schaefer, D.W.; Lin, G. The polysiloxanes. Oxford University Press., 2015.
3. Golovenko, E. A.; Kocheva, A. N.; Semenov, A. V.; Baykova, S. O.; Deriabin, K. V.; Baykov, S. V.; Boyarskiy, V.P.; Islamova, R. M. Palladium-functionalized polysiloxane drop-casted on carbon paper as a heterogeneous catalyst for the Suzuki–Miyaura reaction. Polymers, 2024, 16(19), 2826.
4. Deriabin, K.V.; Golovenko, E.A.; Antonov, N.S.; Baykov, S.V.; Boyarskiy, V.P.; Islamova, R.M. Platinum macrocatalyst for heterogeneous Si–O dehydrocoupling. Dalton Trans., 2024, 52(18), 5854-5858.

Ammonia synthesis is crucial for global fertilizer production, traditionally relying on iron-based catalysts in the Haber–Bosch process [1,2]. However, the limitations of iron catalysts—such as low reaction rates and susceptibility to deactivation—have driven interest in alternative catalysts, particularly Ru-, Co- and high-entropy-based transition metal systems. The use of promoters, both in single and double settings, has become key to enhancing the efficiency and stability of these transition metal catalysts [3]. This presentation focuses on the role of various promoters in optimizing Ru-, Co- and Fe-based catalysts, exploring their mechanisms and potential to advance ammonia synthesis.

Results:
The inclusion of promoters such as K₂O, Ba, Ce, or BaO, among others, significantly enhances the catalytic performance of Ru-, Co- and Fe-based catalysts. For iron, these promoters improve the adsorption of N₂ and its dissociation, leading to higher ammonia yields and longer catalyst lifespans. In cobalt-based systems, these promoters stabilize the active metal sites and promote efficient nitrogen dissociation within a temperature range of below 500 ⁰C. The promoters modify the electronic properties of the catalysts, improving their overall efficiency. The nature of the rate-determining step cannot always be limited to N₂ decomposition; it can also involve other hydrogenation steps.

Conclusion:
Promoters are crucial in optimizing the performance of transition metal catalysts in ammonia synthesis. These promoters enhance catalyst stability, increase reaction rates, and suppress deactivation, offering a promising pathway for more efficient and sustainable ammonia production. Future research should focus on refining promoter–metal interactions to further improve catalyst performance and reduce energy consumption.

1. Haber, F.; van Oordt, G. Über die Bildung von Ammoniak den Elementen. Zeitschrift für anorganische Chemie 1905, 44, 341–378, doi:10.1002/zaac.19050440122.
2. Haber, F. The Synthesis of Ammonia from Its Elements. Nobel Lecture 1920.
3. Huang, J.; Yuan, M.; Li, X.; Wang, Y.; Li, M.; Li, J.; You, Z. Inhibited Hydrogen Poisoning for Enhanced Activity of Promoters-Ru/Sr2Ta2O7 Nanowires for Ammonia Synthesis. Journal of Catalysis 2020, 389, 556–565, doi:10.1016/j.jcat.2020.06.037.

Hydrogen fuel is a non-toxic and abundantly available energy source with a high potential in replacing traditional fossil fuels in the automotive sector. However, several challenges related to its storage need to be resolved for effective industrial applications. Compounds such as sodium borohydride (NaBH4) present a promising option as hydrogen sources, capable of releasing hydrogen rapidly under controlled conditions when utilized with heterogeneous catalyst systems. The hydrolysis of NaBH₄ can be easily controlled by adding or removing a solid catalyst from its solutions. While numerous reports show many catalysts for this reaction, the main emphasis is on their efficiency. The ideal catalyst should not only demonstrate high performance, but also withstand operational temperatures of 60–80 °C, typical for hydrogen engines, and maintain its efficiency for as long as possible. These aspects are often neglected in other reports, while being crucial for their future applications.

In this presentation, I explore metal-based catalysts used for the hydrolysis of sodium borohydride, focusing on their efficiency, durability, and stability at elevated temperatures. We successfully synthesized a variety of cobalt catalysts from both primary and secondary sources and tested their long-term effectiveness in hydrogen production using a custom-built testing system. Our research highlights essential parameters that are crucial for the future industrial applications of hydrogen generation from borohydride hydrogen storage systems, offering valuable insights for advancements in energy production.

Cellulose, the most abundant natural polymer, has garnered significant attention as a catalyst and a catalytic support in sustainable chemical processes. Its unique structure, high surface area, and tunable functional groups, such as hydroxyl moieties, make it an ideal candidate for facilitating various catalytic reactions. The functionalisation of cellulose enhances its catalytic properties, enabling acid–base, redox, and enzymatic reactions. Additionally, its biodegradability and renewability align with green chemistry principles, providing an eco-friendly alternative to traditional catalysts. Cellulose has emerged as a promising material for catalysis in water treatment. Its abundance, eco-friendliness, and ease of functionalisation make it an attractive alternative to conventional catalysts in addressing water pollution challenges. By incorporating functional groups or immobilising active species on its surface, cellulose can facilitate advanced oxidation processes, adsorption, and photocatalytic degradation of contaminants. Modified cellulose-based catalysts have demonstrated efficiency in removing organic pollutants, heavy metals, and microbial pathogens from water. Available as colloidal solutions, films, and hydrogels, nanocellulose is effective in removing contaminants like heavy metals, dyes, and pharmaceuticals. Cellulose–ZnO catalysts offer the dual advantage of high dye removal efficiency and environmental sustainability. Cellulose enhances the adsorption of the dye molecules, facilitating closer interaction with the reactive sites on ZnO. This study shows its successful photocatalyst degradation of Crystal Violet dye and reusability and the impact of factors like the pH and catalyst morphology. Cellulose–ZnO materials exhibit favourable structural properties, characterised using Fourier transform infrared and scanning electronic microscopy, for catalytic applications; these materials present a significant step toward achieving cleaner water and promoting environmental sustainability.