A method for restoring the catalytic activity to a spent non-additive based hydroprocessing catalyst which method comprises: contacting with a solution a spent non-additive based hydroprocessing catalyst, comprising a metal component and a support material, having a reduced catalytic activity relative to a catalyst in its fresh state prior to use thereof to thereby become said spent catalyst, wherein said solution comprises a chelating agent selected from the group of compounds consisting of aminocarboxylic acids, polyamines, aminoalcohols, oximes, and polyethyleneimines and a solvent, and wherein said contacting is done for a time period from 40 to 400 hours at a temperature in the range of from 10 °C to 60 °C to provide for a restored catalytic activity thereby resulting in an aged catalyst having incorporated therein said chelating agent and said solvent and a re-dispersed catalytically active metal component, wherein said spent hydroprocessing catalyst contains an amount of said chelating agent in the range of from 0.005 moles chelating agent per mole of active metal to 1 mole of chelating agent per mole of active metal; exposing said aged catalyst to conditions including a drying temperature less than 250 °C so as to remove from said aged catalyst a portion of said solvent while removing less than 50 weight percent of said chelating agent from said aged catalyst thereby resulting in a dried aged catalyst; and sulfur treating said dried aged catalyst to yield a restored catalyst, wherein the conditions to which said aged catalyst is exposed prior to the sulfur treating of said dried aged catalyst includes a maximum exposure temperature that is less than a calcination temperature of 400 °C. contacting with a solution a spent non-additive based hydroprocessing catalyst, comprising a metal component and a support material, having a reduced catalytic activity relative to a catalyst in its fresh state prior to use thereof to thereby become said spent catalyst, wherein said solution comprises a chelating agent selected from the group of compounds consisting of aminocarboxylic acids, polyamines, aminoalcohols, oximes, and polyethyleneimines and a solvent, and wherein said contacting is done for a time period from 40 to 400 hours at a temperature in the range of from 10 °C to 60 °C to provide for a restored catalytic activity thereby resulting in an aged catalyst having incorporated therein said chelating agent and said solvent and a re-dispersed catalytically active metal component, wherein said spent hydroprocessing catalyst contains an amount of said chelating agent in the range of from 0.005 moles chelating agent per mole of active metal to 1 mole of chelating agent per mole of active metal; exposing said aged catalyst to conditions including a drying temperature less than 250 °C so as to remove from said aged catalyst a portion of said solvent while removing less than 50 weight percent of said chelating agent from said aged catalyst thereby resulting in a dried aged catalyst; and sulfur treating said dried aged catalyst to yield a restored catalyst, wherein the conditions to which said aged catalyst is exposed prior to the sulfur treating of said dried aged catalyst includes a maximum exposure temperature that is less than a calcination temperature of 400 °C.