TWO-STEP HETEROCYCLIC NITROGEN EXTRACTION FROM PETROLEUM OILS WITH REDUCED REFINERY EQUIPMENT

A process is disclosed for the removal of basic heterocyclic nitrogen compounds from a petroleum crude oil or fraction thereof which comprises treating the petroleum crude oil in a distillation zone to form a distillation bottoms stream which is rich in basic heterocyclic nitrogen compounds. This stream is passed without cooling or heat removal to a two-phase extraction zone with an extractant consisting essentially of an aqueous solution of a lower carboxylic acid and preferably having from 1 to 15 carbon atoms. The extractant complexes the basic heterocyclic nitrogen compound to produce a stream of petroleum crude oil or fraction thereof having a smaller content of heterocyclic nitrogen compounds and a stream comprising the lower carboxylic acid extractant with an increased quantity of basic heterocyclic nitrogen compounds. Both of these streams are passed to distillation without heating. The stream of petroleum crude having the smaller content of heterocyclic nitrogen compound is distilled into an overhead stream and a bottoms stream, the latter of which is hydrotreated to the product of this invention. The stream comprising the higher nitrogen content is passed, without heating, to a distillation zone wherein a stream very high in nitrogen content is removed and an extractant recycle stream is recovered. The extractant recycle stream is then recycled to the extraction zone.