A process for the upgrading of raw hydrocarbon streams rich in heteroatomic polar compounds and/or unsaturated moieties involving the extractive oxidation of sulfur, nitrogen, conjugated dienes and other unsaturated compounds from said streams, the said process comprising treating said streams with a peroxide solution/organic acid couple and an iron oxide catalyst which is a limonite ore, under an acidic pH, atmospheric pressure and ambient or higher temperature. As a result of the reaction, the oxidized heteroatomic compounds, having strong affinity for the aqueous slurry phase, are extracted into said aqueous phase, while the oxidized hydrocarbon is separated from catalyst by decanting, neutralizing, water washing and drying, the resulting end product being a hydrocarbon stream from which have been removed 90% or more of total nitrogen compounds and basic nitrogen up to 99.7%, both calculated as mass contents.