A method is disclosed for removing impurities such as nitrogen and/or sulfur compounds from a hydrocarbon feed, in which the feed is contacted with an adsorbent including a nitrogen-containing organic heterocyclic salt deposited on a porous support, e.g., a supported ionic liquid. Additionally, a method for hydrotreating a hydrocarbon feed which includes a hydroprocessing step is disclosed, wherein prior to hydroprocessing, the feed is contacted with an adsorbent including a supported ionic liquid. Additionally, a method for producing a lube oil which includes isomerization dewaxing of a base oil fraction is disclosed, wherein prior to the isomerization dewaxing step, the base oil fraction is contacted with an adsorbent including a supported ionic liquid. In one embodiment, the adsorbent is regenerated to restore its treatment capacity.