Application of liquid organic hydrogen carriers, such as “methylcyclohexane (MCH)–toluene” chemical couple, is one of the promising approaches for hydrogen storage and transportation. In the present study, copper-modified nickel catalysts with high metal loading of 75 wt% were synthesized via heterophase sol–gel technique, and investigated in the dehydrogenation of MCH. Two approaches towards the copper introduction were applied. The catalyst samples prepared via wetness impregnation of the nickel sol–gel catalyst are characterized by more effective Ni-Cu interaction compared to those where two metals were introduced simultaneously by the mixing of their solid precursors. As a result, the “impregnated” catalysts revealed higher selectivity towards toluene. The addition of copper up to 30 wt% of total metal content was shown to increase significantly toluene selectivity and yield without a noticeable decrease in MCH conversion. The catalyst with the active component including 80 wt% of Ni and 20 wt% of Cu demonstrated 96% and 89% toluene selectivity at 40% and 80% MCH conversion, respectively. Based on the obtained data, this non-noble catalytic system appears quite promising for the MCH dehydrogenation.

The heightened interest in liquid organic hydrogen carriers encourages the development of catalysts suitable for multicycle use. To ensure high catalytic activity and selectivity, the structure–reactivity relationship must be extensively investigated. In this study, high-loaded Ni–Cu catalysts were considered for the dehydrogenation of methylcyclohexane. The highest conversion of 85% and toluene selectivity of 70% were achieved at 325 °C in a fixed-bed reactor using a catalyst with a Cu/Ni atomic ratio of 0.23. To shed light on the relationship between the structural features and catalytic performance, the catalysts were thoroughly studied using a wide range of advanced physicochemical tools. The activity and selectivity of the proposed catalysts are related to the uniformity of Cu distribution and its interaction with Ni via the formation of metallic solid solutions. The method of introduction of copper in the catalyst plays a crucial role in the effectiveness of the interaction between the two metals.

The high-energy potential of wastewater sewage sludge (SS) produced in large amounts around the world makes it an attractive feedstock for fuels and energy sectors. Thermochemical valorization relying on pyrolysis of SS followed by hydrotreatment of pyrolysis oil (Py-SS) might even allow the integration of SS into existing oil refineries. In the present study, catalytic hydrotreatment of Py-SS was performed over a NiCuMo-P-SiO₂ catalyst in a batch reactor at temperatures in the range of 200–390 °C. Due to sulfur presence in the feed, the increasing reaction temperature induced in situ transformation of metallic Ni into Ni₃S₂ in the catalyst. In contrast, the Ni₃P active phase possessed remarkable stability even at the harshest reaction conditions. The oxygen content in the reaction products was decreased by 59%, while up to 52% of N and 89% of S were removed at 390 °C. The content of free fatty acids was greatly reduced by their conversion to n-alkanes, while the larger amount of volatile aromatics was generated from high molecular mass compounds. The quality of oil-derived products greatly changed at elevated temperatures, providing strong evidence of effective upgrading via decarboxy(ny)lation, hydrogenation, and hydrocracking transformations.