Method of Treating Pyrolysis Oil From Waste Plastics

Abstract

The present disclosure provides a method of treating waste plastic pyrolysis oil. The method includes a first step of washing waste plastic pyrolysis oil with water and then removing moisture; a second step of mixing the waste plastic pyrolysis oil from which the moisture is removed and a sulfur source to prepare a mixed oil; a third step of hydrotreating the mixed oil with hydrogen gas in the presence of a hydrotreating catalyst; a fourth step of separating the hydrotreated mixed oil into a liquid stream and a gas stream to obtain liquid pyrolysis oil; and a fifth step of recovering hydrogen gas from the separated gas stream and recycling the recovered hydrogen gas to the third step.

1 . A method of treating waste plastic pyrolysis oil, comprising:
 a first step of washing waste plastic pyrolysis oil with water and then removing moisture;   a second step of mixing the waste plastic pyrolysis oil from which the moisture is removed and a sulfur source to prepare a mixed oil;   a third step of hydrotreating the mixed oil with hydrogen gas in the presence of a hydrotreating catalyst;   a fourth step of separating the hydrotreated mixed oil into a liquid stream and a gas stream to obtain liquid pyrolysis oil; and   a fifth step of recovering hydrogen gas from the separated gas stream and recycling the recovered hydrogen gas to the third step.   
     
     
         2 . The method of  claim 1 , wherein the waste plastic pyrolysis oil that is subjected to the first step comprises moisture in an amount of 300 to 2,000 ppm. 
     
     
         3 . The method of  claim 1 , wherein the sulfur source in the second step comprises sulfur-containing oil. 
     
     
         4 . The method of  claim 1 , wherein the sulfur source in the second step is comprised in an amount of less than 50 parts by weight based on 100 parts by weight of the waste plastic pyrolysis oil. 
     
     
         5 . The method of  claim 1 , wherein the mixed oil in the second step comprises sulfur in an amount of 100 ppm or more. 
     
     
         6 . The method of  claim 1 , wherein the third step comprises:
 a 3-1st step of hydrotreating the mixed oil at a first temperature in the presence of a hydrotreating catalyst to produce a fluid from which olefin, nitrogen, and/or chlorine is removed; and   a 3-2nd step of hydrotreating the fluid at a second temperature higher than the first temperature in the presence of a hydrotreating catalyst to produce refined oil from which impurities are removed.   
     
     
         7 . The method of  claim 6 , wherein the first temperature is higher than 100° C. and lower than 400° C., and the second temperature is higher than 300° C. and lower than 450° C. 
     
     
         8 . The method of  claim 6 , wherein a reaction pressure in the hydrotreating in each of the 3-1st step and the 3-2nd step is more than 10 bar and less than 200 bar. 
     
     
         9 . The method of  claim 6 , wherein liquid hourly space velocities (LHSVs) in the hydrotreating in the 3-1st step and the hydrotreating in the 3-2nd step is 1:0.1 to 1:2.0. 
     
     
         10 . The method of  claim 1 , wherein in the fourth step, the hydrotreated mixed oil is introduced into a high-temperature and high-pressure separator to separate the hydrotreated mixed oil into the liquid stream and the gas stream. 
     
     
         11 . The method of  claim 10 , wherein the gas stream separated in the high-temperature and high-pressure separator is sequentially introduced into a low-temperature and high-pressure separator and a low-temperature and low-pressure separator, and the liquid stream separated in the high-temperature and high-pressure separator is introduced into a high-temperature and low-pressure separator. 
     
     
         12 . The method of  claim 10 , wherein the gas stream separated in the high-temperature and high-pressure separator is washed with water to suppress formation of a salt. 
     
     
         13 . The method of  claim 1 , further comprising a step of performing distillation on the liquid pyrolysis oil separated in the fourth step,
 wherein in the distillation step, formation of a salt is suppressed using a salt remover.   
     
     
         14 . The method of  claim 1 , wherein in the fifth step, the recovered hydrogen gas is purified to remove impurities, and then the hydrogen gas from which the impurities are removed is recycled to the third step. 
     
     
         15 . A method for reducing greenhouse gas emissions in treating waste plastic pyrolysis oil to recover liquid pyrolysis oil, comprising:
 a first step of washing waste plastic pyrolysis oil with water and then removing moisture;   a second step of mixing the waste plastic pyrolysis oil from which the moisture is removed and a sulfur source to prepare a mixed oil;   a third step of hydrotreating the mixed oil with hydrogen gas in the presence of a hydrotreating catalyst;   a fourth step of separating the hydrotreated mixed oil into a liquid stream and a gas stream to obtain liquid pyrolysis oil; and   a fifth step of recovering hydrogen gas from the separated gas stream and recycling the recovered hydrogen gas to the third step.