Two-step heterocyclic nitrogen extraction from petroleum oils

A process for removing heterocyclic nitrogen compounds from a petroleum crude oil or fraction thereof in a two-step process wherein said first step comprises a two-phase extraction zone, said process comprising:

• (a) passing a petroleum crude oil or fraction thereof containing said heterocyclic nitrogen compounds to a two-phase extraction zone having a mixing means and an addition means for the addition to said two-phase extraction zone of an aqueous extractant agent consisting essentially of a carboxylic acid having from 1 to 15 carbon atoms in a concentration of from about 20 up to 95 weight percent in said aqueous phase to form a first phase comprising said petroleum oil or fraction thereof having a reduced content of said heterocyclic nitrogen compounds and to form a second phase comprising water, said carboxylic acid and an increased content of heterocyclic nitrogen compounds compared with the content of heterocyclic nitrogen compounds present in said extractant agent added to said two-phase extraction zone through said addition means;
• (b) removing said first phase comprising said petroleum oil or fraction thereof from said two-phase extraction zone and passing said petroleum oil to a hydrotreatment zone, to hydrotreat said petroleum oil or fraction thereof, at hydrotreatment conditions, in the presence of a hydrotreating catalyst and hydrogen to remove heterocyclic nitrogen compounds;
• (c) removing from said two-phase extraction zone said second phase and passing said second phase to a separation zone to separate said second phase into a stream having a rich content of heterocyclic nitrogen compounds and an extractant recycle stream consisting essentially of water and said C.sub.1 to C.sub.15 carboxylic acid;
• and
• (d) recycling said extractant recycle stream to said two-phase extraction zone through said addition means.