Navigating heterogeneous hydrogenation hazards: A systematic approach from primary screening to catalyst loading and optimization parameters

This research delves into developing an efficient screening process for selecting an economical methodology, appropriate catalyst loading, and batch size for reactor occupancy in hydrogenation of 3-nitro-9-ethylcarbazole (NC-3). The main objective was to prepare the 3-Amino-9-ethylcarbazole (AC-3) using a Raney nickel heterogeneous catalyst from NC-3 and to minimize reaction time. The mass transfer coefficient (k_L.a) was estimated, and the effects of agitation and occupancy (based on the change in hydrogen gas pressure) on k_L.a were investigated. The primary focus was to effectively assess optimizing process parameters like hydrogenation pressure (range of 3–10 bar) and temperatures (up to 135 °C) in the presence of Raney nickel catalyst (of loading range from 3.5 to 12%). The reaction methodology is described based on hydrogen uptake concerning the theoretical requirements and process optimized for a Raney nickel loading of 5.4% at a temperature of 130 °C and 7 bar pressure in approximately 4–6 h. Findings revealed that the major hurdle is the limitation of the surface-aerated hydrogenation technique due to the constraint of the laboratory reactor.