Methods for removal of silicon and chloride contaminants from mixed plastic waste based pyrolysis oil

Abstract

Systems and methods for pretreating a raw mixed plastic waste pyrolysis oil to remove silicon and chloride contaminants using an aqueous alkaline hydroxide solution. Specifically, these systems and methods lead to at least about 30 weight percent reduction in the silicon compounds present in the pyrolysis oil and at least about 50 weight percent reduction in the chloride compounds in the pyrolysis oil.

What is claimed is: 
     
         1 . A method of treating a pyrolysis oil, the method comprising:
 supplying, to a reaction vessel, a pyrolysis oil containing a plurality of silicon compounds and a plurality of chloride compounds, the pyrolysis oil being a mixture of a light liquid fraction obtained from processing of raw mixed plastic waste pyrolysis oil at less than about 170 degrees centigrade (° C.) and a medium liquid fraction obtained from processing of the raw mixed plastic waste pyrolysis oil from about 170° C. to about 370° C.;   mixing the pyrolysis oil with an aqueous alkaline hydroxide solution in the reaction vessel operated at a temperature ranging from about 15° C. to about 225° C., the aqueous alkaline hydroxide solution containing about 1 weight percent to about 20 weight percent of the alkaline hydroxide;   allowing the mixture of the pyrolysis oil and the aqueous alkaline hydroxide solution to separate into an upgraded pyrolysis oil fraction and an aqueous fraction; the upgraded pyrolysis oil fraction containing at least about 30 weight percent less of the plurality of silicon compounds than the plurality of silicon compounds in the pyrolysis oil and at least about 50 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the pyrolysis oil; and   extracting the upgraded pyrolysis oil fraction and optionally supplying it to a hydroprocessing unit.   
     
     
         2 . The method of  claim 1 , wherein the mixture of the pyrolysis oil and the aqueous alkaline hydroxide solution is separated into the upgraded pyrolysis oil fraction and the aqueous fraction by settling or coalescence. 
     
     
         3 . The method of  claim 1 , wherein the aqueous alkaline hydroxide solution contains less than about 10 weight percent of the alkaline hydroxide. 
     
     
         4 . The method of  claim 3 , wherein the upgraded pyrolysis oil fraction contains at least about 50 weight percent less of the plurality of silicon compounds than the plurality of silicon compounds in the pyrolysis oil and at least about 90 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the pyrolysis oil. 
     
     
         5 . A method of treating a pyrolysis oil, the method comprising:
 supplying, to a reaction vessel, a pyrolysis oil containing a plurality of silicon compounds and a plurality of chloride compounds;   mixing the pyrolysis oil with a first aqueous alkaline hydroxide solution in the reaction vessel operated at a temperature ranging from about 15° C. to about 30° C., the first aqueous alkaline hydroxide solution having a pH of about 10 or greater;   allowing the mixture of the pyrolysis oil and the first aqueous alkaline hydroxide solution to separate into a first upgraded pyrolysis oil fraction and a first aqueous fraction;   removing the first aqueous fraction from the reaction vessel;   mixing the first upgraded pyrolysis oil fraction and a second aqueous alkaline hydroxide solution in the reaction vessel operated at a temperature ranging from about 15° C. to 225° C., the second aqueous alkaline hydroxide solution having a pH of about 10 or greater;   allowing the mixture of the first upgraded pyrolysis oil fraction and the second aqueous alkaline hydroxide solution to separate into a second upgraded pyrolysis oil fraction and a second aqueous fraction;   removing the second aqueous fraction from the reaction vessel;   mixing the second upgraded pyrolysis oil fraction with a third aqueous alkaline hydroxide solution in the reaction vessel operated at a temperature ranging from about 15° C. to 30° C., the third aqueous alkaline hydroxide solution having a pH of about 10 or greater;   allowing the mixture of the second upgraded pyrolysis oil fraction and the third aqueous alkaline hydroxide solution to separate into a third upgraded pyrolysis oil fraction and a third aqueous fraction, the third upgraded pyrolysis oil fraction containing at least about 30 weight percent less of the plurality of silicon compounds than the plurality of silicon compounds in the pyrolysis oil and at least about 50 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the pyrolysis oil; and   extracting the third upgraded pyrolysis oil fraction and optionally supplying it to a hydroprocessing unit.   
     
     
         6 . The method of  claim 5 , wherein the pyrolysis oil is a raw mixed plastic waste pyrolysis oil. 
     
     
         7 . The method of  claim 6 , wherein the third upgraded pyrolysis oil fraction contains at least about 90 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the raw mixed plastic waste pyrolysis oil. 
     
     
         8 . The method of  claim 5 , wherein the pyrolysis oil is a light liquid fraction obtained from processing of raw mixed plastic waste pyrolysis oil at less than about 170° C., defining a naphtha fraction. 
     
     
         9 . The method of  claim 8 , wherein the third upgraded pyrolysis oil fraction contains at least about 80 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the naphtha fraction. 
     
     
         10 . The method of  claim 5 , wherein the pyrolysis oil is a medium liquid fraction obtained from processing of raw mixed plastic waste pyrolysis oil from about 170° C. to about 370° C., defining a diesel fraction. 
     
     
         11 . The method of  claim 10 , wherein the third upgraded pyrolysis oil fraction contains at least about 50 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the diesel fraction. 
     
     
         12 . A system for treating a pyrolysis oil, the system comprising:
 a reaction vessel operated at a temperature ranging from about 15° C. to about 30° C. and containing:
 (i) a pyrolysis oil inlet configured to receive and supply to the reaction vessel a pyrolysis oil containing a plurality of silicon compounds and a plurality of chloride compounds, 
 (ii) an alkaline hydroxide inlet configured to receive and supply to the reaction vessel an aqueous alkaline hydroxide solution containing less than about 20 weight percent of the alkaline hydroxide, 
 (iii) a mixing element located inside the reaction vessel to facilitate mixing of the pyrolysis oil and the aqueous alkaline hydroxide solution, 
 (iv) an upgraded pyrolysis oil outlet configured to discharge an upgraded pyrolysis oil fraction that is produced by separation of the mixture of the pyrolysis oil and the aqueous alkaline hydroxide solution into the upgraded pyrolysis oil fraction and an aqueous fraction, the upgraded pyrolysis oil fraction containing at least about 30 weight percent less of the plurality of silicon compounds than the plurality of silicon compounds in the pyrolysis oil and at least about 50 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the pyrolysis oil, and 
 (v) an effluent outlet configured to supply the aqueous fraction to an alkaline hydroxide recycling unit and to discharge any solids formed during production of the upgraded pyrolysis oil fraction and the aqueous fraction; and 
   the alkaline hydroxide recycling unit connected to and in fluid communication with the effluent outlet and configured to process the aqueous fraction and supply fresh aqueous alkaline hydroxide solution to the reaction vessel.   
     
     
         13 . The system of  claim 12 , further comprising a jacket heater operatively connected to an external wall of the reaction vessel. 
     
     
         14 . The system of  claim 12 , further comprising a hydrotreater unit connected to and in fluid communication with the upgraded pyrolysis oil outlet of the reaction vessel. 
     
     
         15 . The system of  claim 12 , wherein the pyrolysis oil is raw mixed plastic waste pyrolysis oil. 
     
     
         16 . The system of  claim 15 , wherein the upgraded pyrolysis oil fraction contains at least about 90 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the raw mixed plastic waste pyrolysis oil. 
     
     
         17 . The system of  claim 12 , wherein the pyrolysis oil is a light liquid fraction obtained from processing of raw mixed plastic waste pyrolysis oil at less than about 170° C., defining a naphtha fraction. 
     
     
         18 . The system of  claim 17 , wherein the upgraded pyrolysis oil fraction contains at least about 80 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the naphtha fraction. 
     
     
         19 . The system of  claim 12 , wherein the pyrolysis oil is a medium liquid fraction obtained from processing of raw mixed plastic waste pyrolysis oil from about 170° C. to about 370° C., defining a diesel fraction. 
     
     
         20 . The system of  claim 19 , wherein the third upgraded pyrolysis oil fraction contains at least about 50 weight percent less of the plurality of chloride compounds than the plurality of chloride compounds in the diesel fraction.