A delayed coking process includes: a. introducing a fresh hydrocarbon feedstock containing undesirable sulfur and/or nitrogen compounds for preheating into the lower portion of a coking unit product fractionator; b. introducing at least a portion of an intermediate fraction derived from the fractionator and at least one adsorbent material that selectively adsorbs sulfur- and/or nitrogen-containing compounds into a mixing zone to form an adsorbent slurry stream; c. discharging a bottoms fraction from the fractionator; d. adding all or a portion of the slurry stream to the bottoms fraction to form a mixed coking unit feedstream; e. heating the mixed feedstream in the coking unit furnace to a predetermined coking temperature; and f. passing the heated mixed feedstream to a drum of the delayed coking to produce a delayed coking product stream while depositing the adsorbent material having adsorbed sulfur and/or nitrogen compounds with the coke in the coking drum.