Process for the purification and treatment of a hydrocarbon stream comprising the following steps: a) Providing a hydrocarbon stream having a diene value of at most 1.5 g l2/100 g, preferably at most 1.0, preferably, even more preferably at most 0.5 gl2/100 g as measured according to UOP 326 and a bromine number of at least 5 g Br2/ 100g as measured according to ASTM D1159 and containing at least 10 wt % of pyrolysis plastic oil the other part of said hydrocarbon stream being a first diluent or alternatively providing a hydrocarbon stream containing only pyrolysis plastic oil; b) optionally putting in contact the effluent obtained at step a) with silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves, alkaline oxide and/or porous supports containing lamellar double hydroxide modified or not and silica gel, or any mixture thereof to trap silicon and/or metals and/or phosphorous and/or halogenates; c) optionally performing a first hydrotreating step of the effluent obtained at step a) or b) at a temperature of at most 225°C preferably 200°C; d) putting in contact the effluent obtained at the previous step with silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves, alkaline oxide and/or porous supports containing lamellar double hydroxide modified or not and silica gel, or any mixture thereof to trap silicon and/or metals and/or phosphorous and/or halogenates; e) performing a second hydrotreating step at a temperature of at least 200°C, f) recovering a purified hydrocarbon stream characterized in that said second hydrotreating step is performed over at least one catalyst that presents both (i) an hydrotreating function, namely at least one metal of group VIB as for example Mo, W in combination or not with a promotor selected from at least one metal of group VIII and/or VIIIB as for example Ni and/or Co, and/or mixture thereof, preferably these metals being used in sulfided form and (ii) a trap function, namely said catalyst presents a BET surface area ranging from 150 m2/g to 400 m2/g, said purified hydrocarbon stream obtained at step f) is mixed with naphtha, gasoil or crude oil to have a pyrolysis plastic oil concentration ranging from 0.01 wt % to at most 50 wt %; before being further sent at least partially to a steam cracker to produce olefins, such as ethylene and prolylene, and aromatics. a) Providing a hydrocarbon stream having a diene value of at most 1.5 g l2/100 g, preferably at most 1.0, preferably, even more preferably at most 0.5 gl2/100 g as measured according to UOP 326 and a bromine number of at least 5 g Br2/ 100g as measured according to ASTM D1159 and containing at least 10 wt % of pyrolysis plastic oil the other part of said hydrocarbon stream being a first diluent or alternatively providing a hydrocarbon stream containing only pyrolysis plastic oil; b) optionally putting in contact the effluent obtained at step a) with silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves, alkaline oxide and/or porous supports containing lamellar double hydroxide modified or not and silica gel, or any mixture thereof to trap silicon and/or metals and/or phosphorous and/or halogenates; c) optionally performing a first hydrotreating step of the effluent obtained at step a) or b) at a temperature of at most 225°C preferably 200°C; d) putting in contact the effluent obtained at the previous step with silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminium oxide, molecular sieves, alkaline oxide and/or porous supports containing lamellar double hydroxide modified or not and silica gel, or any mixture thereof to trap silicon and/or metals and/or phosphorous and/or halogenates; e) performing a second hydrotreating step at a temperature of at least 200°C, f) recovering a purified hydrocarbon stream characterized in that said second hydrotreating step is performed over at least one catalyst that presents both (i) an hydrotreating function, namely at least one metal of group VIB as for example Mo, W in combination or not with a promotor selected from at least one metal of group VIII and/or VIIIB as for example Ni and/or Co, and/or mixture thereof, preferably these metals being used in sulfided form and (ii) a trap function, namely said catalyst presents a BET surface area ranging from 150 m2/g to 400 m2/g, said purified hydrocarbon stream obtained at step f) is mixed with naphtha, gasoil or crude oil to have a pyrolysis plastic oil concentration ranging from 0.01 wt % to at most 50 wt %; before being further sent at least partially to a steam cracker to produce olefins, such as ethylene and prolylene, and aromatics.