Process for producing naphtha and diesel from pyrolysis of plastics

Abstract

The present invention relates to producing hydrocarbon products from a polymer feed. In particular, the present invention relates to producing naphtha and diesel from a polymer feed by pyrolysis and hydrogenation of a fluid product stream from the pyrolysis.

1 . A process for producing naphtha and diesel from a polymer feed, the process comprising:
 (i) providing a polymer feed comprising at least 80 wt. % of polyolefin polymers;   (ii) melting the polymer feed to provide a molten polymer feed;   (iii) passing the molten polymer feed to a rotary kiln reactor comprising a plurality of sequential heating zones, wherein each zone of the rotary kiln is operated at a temperature of from 300° C. to 800° C. to pyrolyze the molten polymer feed and produce a fluid product stream and a solid char product;   (iv) separating the solid char product from the fluid product stream;   (v) passing a liquid fraction of the fluid product stream comprising C 5+  hydrocarbons to a hydrogenation reactor and hydrogenating said liquid fraction to produce a hydrogenated hydrocarbon product stream;   (vi) fractionating the hydrogenated hydrocarbon product stream to produce a light hydrogenated fraction comprising C 5-20  hydrocarbons;   (vii) hydrocracking the light hydrogenated fraction to produce a light hydrocarbon product stream enriched in C 5-10  hydrocarbons; and   (viii) fractionating the light hydrocarbon product stream from (vii) to produce a naphtha fraction and a diesel fraction.   
     
     
         2 . A process according to  claim 1 , further comprising the step of obtaining a kerosene fraction from the light hydrocarbon product stream enriched in C 5-10  hydrocarbons. 
     
     
         3 . A process according to  claim 2 , wherein the kerosene fraction is obtained by fractionating the light hydrocarbon stream from (vii). 
     
     
         4 . A process according to any one of  claims 1 to 3 , wherein fractionating the hydrogenated hydrocarbon product stream comprises fractionating in a fractional distillation column. 
     
     
         5 . A process according to any one of the proceeding claims, wherein the rotary kiln comprises four or more sequential heating zones. 
     
     
         6 . A process according to  any one of the preceding claims , wherein the rotary kiln is maintained under an atmosphere of nitrogen. 
     
     
         7 . A process according to  any one of the preceding claims , wherein the rotary kiln is operated at approximately atmospheric pressure or at a slight negative pressure of 0.9 bar absolute or higher, for example 0.95 bar absolute or higher. 
     
     
         8 . A process according to  any one of the preceding claims , wherein each zone of the rotary kiln is operated at a temperature of from 310° C. to 720° C., preferably from 400° C. to 650° C. 
     
     
         9 . A process according to  any one of the preceding claims , wherein the final zone of the plurality of zones is heated to a higher temperature than the other heating zones, preferably wherein the plurality of heating zones comprise sequential zones operated at from 310° C. to 600° C. in one or more zones and from 480° C. to 700° C. in a subsequent final zone. 
     
     
         10 . A process according to  any one of the preceding claims , wherein the polymer feed comprises at least 85 wt. % polyolefin polymers, preferably at least 90 wt. % polyolefin polymers, more preferably at least 95 wt. % polyolefin polymers, for example at least 99 wt. % polyolefin polymers. 
     
     
         11 . A process according to  any one of the preceding claims , wherein the polyolefin polymers comprise or consist essentially of polyethylene and polypropylene, for example wherein the polyolefin polymers comprise at least 90 wt. % polyethylene and polypropylene, preferably at least 95 wt. % polyethylene and polypropylene, for example at least 99 wt. % polyethylene and polypropylene. 
     
     
         12 . A process according to  any one of the preceding claims , wherein the polymer feed is melted in a melt extruder. 
     
     
         13 . A process according to  claim 12 , wherein the melt extruder is heated at a temperature of from 250° C. to 350° C., preferably from 265° C. to 325° C. 
     
     
         14 . A process according to  any one of the preceding claims , wherein calcium oxide is added to the polymer feed, preferably in an amount of up to 3 wt. % 
     
     
         15 . A process according to  any one of the preceding claims , wherein at least a portion of a non-condensable gas fraction is recycled to provide heating to the rotary kiln and/or to melt the polymer feed. 
     
     
         16 . A process according to  any one of the preceding claims , wherein the solid char product comprises no more than 15 wt. % of the effluent from the kiln, preferably no more than 10 wt. %. 
     
     
         17 . A process according to  any one of the preceding claims , wherein the hydrogenation reactor in step (v) comprises a fixed bed reactor, preferably a trickle bed reactor. 
     
     
         18 . A process according to  any one of the preceding claims , wherein the solid char product is separated from the fluid product stream at least in part by a decanter centrifuge or a tricanter centrifuge. 
     
     
         19 . A process according to  any one of the preceding claims , wherein the fluid product stream comprises a non-condensable gas fraction and a liquid fraction comprising C 5 + hydrocarbons, wherein the non-condensable gas fraction is separated from the liquid fraction prior to step (v). 
     
     
         20 . A process according to  any one of the preceding claims , wherein the hydrogenation catalyst is a metal catalyst, preferably wherein the metal hydrogenation catalyst comprises a metal selected from Group VIII of the periodic table, preferably the catalyst comprises Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and/or Pt, such as a catalyst comprising Ni, Co, Mo, W, Cu, Pd, Ru, Pt, and preferably wherein the catalyst is selected from CoMo, NiMo or Ni, more preferably wherein the catalyst is NiMo; and/or wherein the catalyst is supported on a carrier preferably selected from bauxite, alumina, silica, silica-alumina or zeolite, preferably alumina. 
     
     
         21 . A process according to  any one of the preceding claims , wherein the light hydrogenated fraction comprising C 5-20  hydrocarbons undergoes a further fractionating step to at least partially separate a crude C 5-10  hydrocarbon fraction, a crude C 10-20  hydrocarbon fraction and/or a crude C 8-16  hydrocarbon fraction, and wherein the remaining light hydrogenated C 5-20  hydrocarbons proceed to the hydrocracking step. 
     
     
         22 . A process according to  claim 21 , wherein the one or more of the at least partially separated crude hydrocarbons fractions are blended with fossil fuel materials. 
     
     
         23 . A process according to  claim 22 , wherein the fossil fuel materials are selected from naphtha, kerosene or diesel. 
     
     
         24 . A process according to any one of  claims 21 to 23 , wherein 80 wt % or less of the C 5-10 , C 8-16  and/or C 10-20  crude hydrocarbon fraction is separated from the light hydrogenated fraction comprising C 5-20  hydrocarbons, preferably 70 wt % or less, more preferably 50 wt % or less. 
     
     
         25 . A process according to  any one of the preceding claims , wherein the hydrocracking step comprises contacting the light hydrogenated fraction with a hydrocracking catalyst at a temperature of from 250° C. to 400° C., preferably from 300 to 350° C., and/or at a pressure of from 3 to 10 MPa, preferably from 4 to 8 MPa. 
     
     
         26 . An apparatus for producing naphtha and diesel from a polymer feed, the apparatus comprising:
 (i) means for melting a polymer feed comprising at least 80 wt. % of polyolefin polymers to provide a molten polymer feed;   (ii) a rotary kiln reactor configured to receive the molten polymer feed from part (i), the rotary kiln reactor configured to provide a plurality of sequential heating zones, wherein each zone of the rotary kiln is configured to be operated at a temperature of from 300° C. to 800° C. to pyrolyze the molten polymer feed and produce a fluid product stream and a solid char product;   (iii) means for separating the solid char product from the fluid product stream; and   (iv) a hydrogenation reactor configured to receive a liquid fraction of the fluid product stream comprising C 5+  hydrocarbons from part (iii) and to hydrogenate said liquid fraction to produce a hydrogenated hydrocarbon product stream;   (v) means for fractionating the hydrogenated hydrocarbon product stream to produce a light hydrogenated fraction comprising C 5-20  hydrocarbons;   (vi) a hydrocracking reactor configured to catalytically crack the light hydrogenated fraction in the presence of hydrogen to produce a light hydrocarbon product stream enriched in C 5-10  hydrocarbons; and   (vii) means for fractionating the light hydrocarbon product stream from (vi) to produce a naphtha fraction and a diesel fraction.   
     
     
         27 . An apparatus according to  claim 26 , wherein the apparatus comprises means for obtaining a kerosene fraction from the light hydrocarbon product stream enriched in C 5-10  hydrocarbons. 
     
     
         28 . An apparatus according to  claim 27 , wherein the means for fractionating the light hydrocarbon product stream in part (vii) is arranged to produce a kerosene fraction, 
     
     
         29 . An apparatus according to any one of  claims 26 to 28 , wherein the means for fractionating the hydrogenated hydrocarbon product stream comprises a fractional distillation column configured for receiving the hydrogenated hydrocarbon product stream from the hydrogenation reactor. 
     
     
         30 . An apparatus according to any one of  claims 26 to 29 , wherein the apparatus further comprises means for fractionating the light hydrogenated fraction comprising C 5-20  hydrocarbons to at least partially separate a crude C 5-10  hydrocarbon fraction, a crude C 10-20  hydrocarbon fraction and/or a crude C 8-16  hydrocarbon fraction. 
     
     
         31 . An apparatus according to  claim 30 , wherein the means for fractionating the light hydrogenated fraction comprising C 5-20  hydrocarbons comprises a fractional distillation column configured to receive the light hydrogenation fraction produced in part (v). 
     
     
         32 . An apparatus according to any one of  claims 26 to 31 , wherein the rotary kiln is configured to provide four or more sequential heating zones, preferably wherein the rotary kiln is configured to operate as defined in any one of  claims 6 to 9 . 
     
     
         33 . An apparatus according to any one of  claims 26 to 32 , wherein the means for melting the polymer feed comprises a melt extruder, preferably configured to heat the polymer feed at a temperature of from 250° C. to 350° C., preferably from 265° C. to 325° C. 
     
     
         34 . An apparatus according to any one of  claims 26 to 33 , wherein the apparatus is configured to recycle a gas fraction of the hydrocarbon product stream to provide heating to the rotary kiln and/or to melt the polymer feed. 
     
     
         35 . An apparatus according to any one of  claims 26 to 34 , wherein the hydrogenation reactor in part (iv) comprises a trickle bed reactor, preferably wherein the catalyst is as defined in  claim 20 . 
     
     
         36 . An apparatus according to any one of  claims 26 to 35 , wherein the means for separating the solid char product from the fluid product stream comprises a decanter centrifuge or a tricanter centrifuge, and/or wherein the means for separating the solid char product from the fluid product stream comprises a char outlet from the rotary kiln and a vapour outlet from the rotary kiln, separate to the char outlet, for receiving the fluid product stream the rotary kiln.