Hydroformylation of α-olefin dimers over Rh/C for synthesis of branched-chain fatty alcohols/acids

• A comprehensive process from Fischer–Tropsch synthesized α-olefins to branched-chain fatty alcohols/acids was demonstrated. • Hydroformylation of α-olefin dimers catalyzed by heterogeneous Rh/C exhibited excellent product selectivity (>86 %). • The synthesized branched-chain fatty alcohols/acids possess low freezing point (< −60°C) and pour point (<-60°C). The industrial utilisation of Fischer–Tropsch synthesis (FTS) products, particularly the valuable C5–C9 linear α-olefins, has been hindered by the high energy-intensive separation of olefins and alkanes with identical carbon numbers. This study presents a comprehensive process integrating the selective dimerisation of linear α-olefins to α-olefin dimers, enabling their separation from paraffins in FTS products. These dimers are subsequently converted into branched-chain aldehyde intermediates through heterogeneous hydroformylation using Rh/C as the catalyst. Notably, optimising the reaction conditions achieved the main product aldehyde of α-olefin dimers with excellent selectivity (up to 86.66 %) at 65 °C, compared to linear α-olefins, which exhibited only 49.31 % selectivity. In-situ IR spectroscopy was used to monitor the entire reaction process. The resulting branched aldehyde intermediates were further transformed into branched acids or branched alcohols through oxidation or reduction reactions, respectively. These products have diverse applications as surfactants, coal flotation agents, and cutting fluid additives. The synthesised compounds were characterised using FT-IR, GC, GC–MS, and NMR. In addition, a comprehensive evaluation of their physicochemical properties was conducted. This study provides a versatile design strategy for developing high-value intermediates from α-olefins in the FTS.