Process for pyrolysis of coal

Abstract

A process for pyrolyzing a coal feed is described. The coal feed is pyrolyzed into a coal tar stream and a coke stream in a pyrolysis zone. The coal tar stream is fractionated into at least a pitch stream. The pitch stream is hydrogenated, and the hydrogenated pitch stream is recycled into the pyrolysis zone. The hydrocarbon stream may be processed further by at least one of hydrotreating, hydrocracking, fluid catalytic cracking, alkylation, and transalkylation.

What is claimed is: 
     
         1 . A process comprising:
 pyrolyzing a coal feed into a coal tar stream and a coke stream in a pyrolysis zone;   separating the coal tar stream into at least a pitch stream;   hydrogenating the pitch stream; and   recycling the hydrogenated pitch stream into the pyrolysis zone.   
     
     
         2 . The process of  claim 1  wherein hydrogenating the pitch stream comprises contacting the pitch stream with a hydrogenation catalyst consisting of metal selected from the group consisting of Group VI metals (Cr, Mo, W), Group VII metals (Mn, Tc, Re), or Group VIII metals (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) and combinations thereof supported on an inorganic oxide, carbide or sulfide support, including Al 2 O 3 , SiO 2 , SiO 2 —Al 2 O 3 , zeolites, non-zeolitic molecular sieves, ZrO 2 , TiO 2 , ZnO, and SiC. 
     
     
         3 . The process of  claim 1  wherein hydrogenating the pitch stream takes place at a temperature between about 250° C. and about 500° C. 
     
     
         4 . The process of  claim 1  wherein the hydrogenation takes place at a pressure between about 1.72 MPa (about 250 psig) and about 20.7 MPa (about 3,000 psig). 
     
     
         5 . The process of  claim 1  wherein separating the coal tar stream further provides a hydrocarbon stream. 
     
     
         6 . The process of  claim 5  further comprising:
 recovering at least one product from the hydrocarbon stream. 
 
     
     
         7 . The process of  claim 1  further comprising:
 feeding additional coal feed into the pyrolysis zone; and 
 pyrolyzing the recycled pitch stream. 
 
     
     
         8 . The process of  claim 6  further comprising:
 processing the hydrocarbon stream to produce at least one product. 
 
     
     
         9 . The process of  claim 8  wherein the hydrocarbon stream is processed by at least one of hydrotreating, hydrocracking, fluid catalytic cracking, alkylation, and transalkylation. 
     
     
         10 . The process of  claim 9  further comprising:
 treating at least one product to remove contaminants. 
 
     
     
         11 . A process for recovering at least one product from coal tar comprising:
 introducing a coal feed into a pyrolysis zone;   pyrolyzing the coal feed in the pyrolysis zone to produce a coal tar stream and a coke stream;   separating the coal tar stream into at least one hydrocarbon stream and a pitch stream;   hydrogenating the pitch stream;   recycling the hydrogenated pitch stream to the pyrolysis zone;   pyrolyzing the hydrogenated pitch stream; and   recovering at least one product from the hydrocarbon stream.   
     
     
         12 . The process of  claim 11  wherein the recovering comprises:
 processing the hydrocarbon stream by at least one of hydrotreating, hydrocracking, fluid catalytic cracking, alkylation, and transalkylation. 
 
     
     
         13 . The process of  claim 11  wherein hydrogenating the pitch stream comprises contacting the pitch stream with a hydrogenation catalyst consisting of metal selected from the group consisting of Group VI metals (Cr, Mo, W), Group VII metals (Mn, Tc, Re) or Group VIII metals (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) metals and combinations thereof supported on an inorganic oxide, carbide or sulfide support, including Al 2 O 3 , SiO 2 , SiO 2 —Al 2 O 3 , zeolites, non-zeolitic molecular sieves, ZrO 2 , TiO 2 , ZnO, and SiC. 
     
     
         14 . The process of  claim 11 , wherein hydrogenating the pitch stream takes place at a temperature between about 250° C. and about 500° C. 
     
     
         15 . The process of  claim 11 , wherein hydrogenating the pitch stream takes place at a pressure between about 1.72 MPa (about 250 psig) and about 20.7 MPa (about 3,000 psig). 
     
     
         16 . The process of  claim 11  wherein pyrolyzing the hydrogenated pitch stream further comprises pyrolyzing additional coal feed with the hydrogenated pitch stream. 
     
     
         17 . The process of  claim 11  wherein hydrogenating the pitch stream uses hydrogen provided in a hydrogen-containing compound selected from the group consisting of tetralin, alcohols, and hydrogenated naphthalenes. 
     
     
         18 . The process of  claim 1  wherein hydrogenating the pitch stream comprises adding hydrogen to a hydrogenation zone. 
     
     
         19 . The process of  claim 11  wherein separating the coal tar stream provides a plurality of hydrocarbon streams and the pitch stream. 
     
     
         20 . The process of  claim 11  wherein hydrogenating the pitch stream uses a catalyst bed selected from the group consisting of a fixed catalyst bed, an ebulated catalyst bed, and a fluidized catalyst bed.