Ferrocene-based catalysts for in-situ hydrothermal upgrading of heavy crude oil: Synthesis and application

•The catalytic performance of oil-soluble synthesized Ferrocene-based ligand catalysts (Mono-, Di- and Tri-Ferrocene) for in-situ upgrading of heavy oil was studied.•Used Ferrocene was mainly transformed in-situ to the particles of iron oxide and sulfide.•The maximum viscosity reduction was observed in presence Tri-Ferrocene and reached around 40% compared to non-catalytic hydrothermal upgrading.•Formed iron sulfide in-situ, show an ideal in situ H2S scavenger method confirming the positive side that reduces its escalation during the processing and refining of heavy oil.