In view of the worsening quality of crude oil, the use of unconventional petroleum feedstocks (heavy oils, bitumens, residues, etc.) in processing is becoming increasingly important. The...

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.

Biomass-derived liquids, such as bio-oil obtained by fast pyrolysis, can be a valuable source of fuels and chemicals. However, these liquids have high oxygen and water content, needing further upgrading typically involving hydrotreating using H₂ at high pressure and temperature. The harsh reaction conditions and use of expensive H₂ have hindered the progress of this technology and led to the search for alternative processes. In this work, hydrogenation in aqueous phase is investigated using in-situ produced hydrogen from reforming of glycerol, a low-value by-product from biodiesel production, over Ni-based catalysts. Guaiacol was selected as a bio-oil model compound and high conversion (95%) to phenol and aromatic ring hydrogenation products was obtained over Ni/γ-Al₂O₃ at 250 °C and 2-h reaction time. Seventy percent selectivity to cyclohexanol and cyclohexanone was achieved at this condition. Hydrogenation capacity of P and Mo modified Ni/γ-Al₂O₃ was inhibited because more hydrogen undergoes methanation, while Cu showed a good performance in suppressing methane formation. These results demonstrate the feasibility of coupling aqueous phase reforming of glycerol with bio-oil hydrogenation, enabling the reaction to be carried out at lower temperatures and pressures and without the need for molecular H₂.

At present, one of the most promising methods of processing renewable raw materials is pyrolysis, which allows liquid organic products (bio-oil) to be derived from biomass. For obtaining fuel products from bio-oil, the latter needs to be preliminarily upgraded. It is appropriate to carry out this process in two stages. The first stage—decarboxylation—is intended to reduce the corrosiveness (acidity) of the feedstock and hydrogen consumption at the second stage. Decarboxylation is usually conducted over noble metal-based catalysts. There are examples of employing cheaper catalysts based on alkaline-earth metals; however, these catalysts suffer from insufficient stability. Here, we report the activity of MgO-based catalysts in the decarboxylation of pentanoic acid, a model compound imitating bio-oil, and the effect of dopants on the stability of the magnesium-containing catalysts. The process has been carried out in an inert atmosphere at a temperature of 350°C and a pressure of 0.50 MPa. Raising the MgO calcination temperature to 1200°C and introducing stabilizing admixtures (Al₂O₃, SiO₂, and ZrO₂) affords catalysts that are mainly deactivated via carbonate formation rather than the formation of soluble magnesium salts and are, therefore, more promising from the standpoint of regenerability.