Hydrogen sulphide and mercaptans scavenging compositions

A composition for scavenging hydrogen sulphide and mercaptans in hydrocarbon streams, said composition comprising an oxazolidine compound and an additive, said additive being a modified alkylphenol-aldehyde resin obtainable by a Mannich reaction of an alkylphenol-aldehyde condensation resin,

• with at least one aldehyde and/or one ketone having 1 to 8 carbon atoms;
• and
• at least one hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 2 to 30 carbon atoms,
• optionally with at least one alkylene oxide;
• said alkylphenol-aldehyde condensation resin being obtainable by condensation;
• of at least one alkylphenol substituted by at least one linear or branched alkyl group having 1 to 30 carbon atoms;
• and
• at least one aldehyde and/or one ketone having 1 to 8 carbon atoms.