Methods for converting plastic to wax

Abstract

Methods for converting plastic to wax are provided. In one embodiment, a method for converting a waste plastic to wax includes introducing the waste plastic into a chamber and adding hydrogen to the chamber. The method includes heating the waste plastic and hydrogen sufficiently to thermally depolymerize the waste plastic to form a wax product comprising paraffin and olefin compounds.

What is claimed is: 
     
         1 . A method for converting a waste plastic to wax, the method comprising the steps of:
 introducing the waste plastic into a chamber;   adding hydrogen to the chamber;   heating the waste plastic and hydrogen sufficiently to thermally depolymerize the waste plastic to form a wax product comprising paraffin and olefin compounds.   
     
     
         2 . The method of  claim 1  further comprising providing the chamber with a depolymerization catalyst selected from solid acid catalysts, liquid acid catalysts, radical initiators, hydrogenation catalysts, zeolites, and catalysts on supports. 
     
     
         3 . The method of  claim 1  wherein:
 melting the waste plastic comprises heating the waste plastic to a temperature of about 100° C. to about 150° C.; and 
 heating the waste plastic and hydrogen comprises heating the waste plastic and hydrogen to a temperature of from about 300° C. to about 500° C. 
 
     
     
         4 . The method of  claim 1  wherein heating the waste plastic and hydrogen comprises forming a polyethylene wax product comprising paraffin and olefin compounds in a paraffin:olefin ratio of at least about 1.1:1 and having a weight average molecular weight of from about 5000 gram per mole (g/mol) to about 15000 g/mol. 
     
     
         5 . The method of  claim 1  wherein introducing the waste plastic into a chamber comprises introducing the waste plastic to a chamber in a batch process. 
     
     
         6 . The method of  claim 1  wherein hydrogen is added to the chamber after the waste plastic is introduced into the chamber. 
     
     
         7 . A method for converting a plastic to wax, the method comprising the steps of:
 contacting the plastic with hydrogen; and   heating the plastic and the hydrogen sufficiently to thermally degrade the plastic to form a wax product with a Saybolt color (ASTM D156) of at least about 0.   
     
     
         8 . The method of  claim 7  wherein heating the plastic and the hydrogen sufficiently to thermally degrade the plastic comprises forming the wax product with a Saybolt color (ASTM D156) of at least about +20. 
     
     
         9 . The method of  claim 7  wherein heating the plastic and the hydrogen comprises thermally degrading the plastic to form a wax product having an average molecular weight of from about 5000 gram per mole (g/mol) to about 15000 g/mol. 
     
     
         10 . The method of  claim 7  wherein heating the plastic and the hydrogen comprises thermally degrading the plastic to form a wax product having an average molecular weight of from about 6000 gram per mole (g/mol) to about 9000 g/mol. 
     
     
         11 . The method of  claim 7  wherein heating the plastic and the hydrogen comprises thermally degrading the plastic to form a wax product comprising paraffin and olefin compounds in a paraffin:olefin ratio of at least about 1.1:1. 
     
     
         12 . The method of  claim 7  wherein heating the plastic and the hydrogen comprises heating the plastic and the hydrogen to a temperature of about 300° C. to about 500° C. 
     
     
         13 . The method of  claim 7  further comprising melting the plastic before contacting the plastic with hydrogen. 
     
     
         14 . The method of  claim 7  further comprising melting the plastic after contacting the plastic with hydrogen. 
     
     
         15 . The method of  claim 7  further comprising melting the plastic at a temperature of about 100° C. to about 150° C. 
     
     
         16 . The method of  claim 7  further comprising agitating the plastic after contacting the plastic with hydrogen to promote dissolution of the hydrogen into the plastic. 
     
     
         17 . The method of  claim 7  wherein contacting the plastic with hydrogen comprises locating the plastic in a hydrogen environment, and wherein the method further comprises maintaining a hydrogen partial pressure in the hydrogen environment of at least about 0.5 atmospheres (atm). 
     
     
         18 . The method of  claim 7  wherein contacting the plastic with hydrogen comprises:
 introducing the plastic to a chamber; and 
 filling the chamber with the hydrogen and an inert gas. 
 
     
     
         19 . The method of  claim 7  wherein contacting the plastic with hydrogen comprises locating the plastic in an environment comprising substantially pure hydrogen. 
     
     
         20 . A method for converting waste plastic to polyethylene wax, the method comprising the steps of:
 melting the waste plastic;   dissolving hydrogen into the waste plastic; and   thermally depolymerizing the waste plastic in the presence of the hydrogen to form a polyethylene wax product comprising paraffin and olefin compounds.