This study is focused on the development of liquid organic hydrogen carriers (LOHC) based on N-heterocyclic compounds. These LOHC-substrates are attractive for their lower hydrogen extraction temperature compared to cycloalkanes, which is caused by the low enthalpy of the dehydrogenation reaction of the N-heterocyclic compounds. The low hydrogen extraction temperature, as well as the low volatility of the heterocycles, provide high purity hydrogen from the reaction. Under similar reaction conditions, the comparison of the efficacy of three promising heterocycles (1-methyl-octahydroindole (8HMI), tetradecahydrophenazine and decahydroquinoline) was carried out in the presence of palladium-containing catalysts. As a result, the advantages of using catalysts supported by alumina, and the high perspectivity of the 8MHI application as a LOHC-substrate, were shown. The dehydrogenation of 8HMI in the presence of 1 wt.% Pd/Al2O3 allowed for reaching a 100% yield in hydrogen under the conditions of the standard catalytic test (1 h, 240 °C). In order to study the high reactivity of 8HMI, thermodynamic dehydrogenation reaction profiles were computationally evaluated, which showed that 8HMI was the most energetically preferred in the field of hydrogen storage from the studied heterocyclic compounds.

Tetradecahydrophenazine (14HP) is a nitrogen-containing heterocycle compound with a high content of hydrogen that can be released during its dehydrogenation to phenazine (P). The high stability of the 14HP/P pair and relatively low dehydrogenation temperature make 14HP a promising organic hydrogen carrier. This manuscript is devoted to the investigation of hydrogen production by 14HP dehydrogenation over Pd supported on a series of magnesium-aluminum oxides prepared by the aerogel method. This technique made it possible to synthesize catalyst supports characterized by a high surface area and high concentration of surface active sites where active transition metals could be stabilized in a finely dispersed state. The synthesized aerogels had high specific surface areas and pore volumes. A surface area as high as 600 m2/g after calcination at 500 °C was observed for the mixed aerogel with an Mg:Al ratio of 1:4. An increase in the concentration of acidic electron-acceptor sites determined by EPR on the surface of the mixed magnesium-aluminum oxide supports with a high surface area prepared by the aerogel method was found to result in higher hydrogen production due to the faster dehydrogenation of sterically hindered nitrogen-containing tetradecahydrophenazine heterocycles.

Актуальность работыMaterials based on nanocrystalline magnesium oxide attract great attention of researchers. The main property of MgO is its pronounced basic properties. MgO nanoparticles find use in organic synthesis as heterogeneous basic catalysts of reactions such as aldol reaction, amide synthesis, Michael reaction and etc. [1]. MgO is a prospective sorbent material for the capture of CO 2 and chloroorganic compounds [2]. It is used as a support in traditional heterogenous catalysis in processes of dry reforming and CO 2 methanation.However, MgO-based catalysts are not widely applied in industry. One of the reasons is the absence of large-scale manufacturing of such materials with high specific surface area (SSA). On the lab-scale level, one of the most prospective approaches is alkoxide sol-gel synthesis of Mg(OH) 2 gels followed by supercritical drying. This method is easily scalable and produces MgO with SSA as high as 350 m 2 / g after calcination at 500 °C. Recently, we developed a modified "one-step" approach to the synthesis of two-and three-component oxide systems based on . In this approach, soluble inorganic salts serve as precursors. The parameters of the process such as pH can be adjusted to obtain optimal porous structure and dispersion of an active component.In this work the approach was applied to the preparation of 1 wt.% Pd/MgO catalysts. The samples were studied via nitrogen adsorption, TEM and UV-vis spectroscopy. Catalytic activity in CO oxidation was evaluated in prompt thermal aging (PTA) mode to test thermal stability.

Ethylene is the most versatile petrochemical feedstock for the production of polyethylene, ethanol, ethylene oxide, ethylene glycol, styrene, dichloroethane, and many other chemical products. The process of hydrogenation of acetylene into ethylene can be used both to purify ethylene from an impurity of alkyne, which is formed at the stage of pyrolysis of crude oil while getting C 2 H 4 [1], and for direct ethylene production from acetylene [2]. Most often, palladium-based metal systems are used as catalysts for the acetylene hydrogenation reaction due to their high catalytic activity. The efficiency of such catalysts is determined primarily by the dispersity and the electronic state of palladium, which depend on the strength of its interaction with the support and the acid-basic properties of the latter. When Al 2 O 3 is used as a support, the acid sites can promote the side reactions of oligomerization. Whereas in the case of magnesium oxide, the base sites, interacting with Pd, can add some electronic density to the metal particles on the surface [3, 4].