Reforming process for enhanced benzene yield

Abstract

A process for reforming a full boiling range naptha feed to enhance benzene yield is disclosed which first separates the feed into a .[.C 6 .]. .Iadd.lighter .Iaddend.fraction .[.containing at least 10% by volume of C 7+ hydrocarbons.]. .Iadd., comprising at least one member selected from the group consisting of C 6 , C 7 , and C 8 hydrocarbons, .Iaddend.and a .[.C 7 +.]. .Iadd.heavier .Iaddend.fraction, then subjecting the .[.C 6 .]. .Iadd.lighter .Iaddend.fraction to a catalytic aromatization process .[.and subjecting the C 7 + fraction to a catalytic reforming process, followed by recovering the aromatics produced.]..Iadd.in the presence of a non-acidic catalyst.Iaddend..

What is claimed is: 
     
       1. A process for reforming a full boiling range hydrocarbon feed to enhance benzene yield comprising: (a) separating the hydrocarbon feed into a C 5-  fraction, a C 6  -C 7  fraction containing at least 10% by volume of C 7+  hydrocarbons, and a C 7+  fraction;   (b) subjecting the C 6  -C 7  fraction to catalytic aromatization at elevated temperatures in the presence of hydrogen and utilizing a catalyst containing a non-acidic carrier and at least one Group VIII noble metal which catalyst converts C 6  paraffins to benzene in a yield of at least 30% by volume and a selectivity of at least 50% and separating a C 5+  effluent:   (c) subjecting the C 7+  fraction to catalytic reforming at elevated temperatures in the presence of hydrogen utilizing a catalyst comprising platinum on an acidic alumina carrier and separating a C 8-  effluent from a C 9+  effluent;   (d) mixing the C 5+  effluent and C 8-  effluent from steps (b) and (c) and recovering an aromatic extract and a non-aromatic raffinate.   
     
     
       2. Process of claim 1 wherein the C 5+  effluent is separated in a flash drum. 
     
     
       3. Process of claim 2 wherein the C 6  fraction contains 15 to 35% by volume of C 7+  hydrocarbons. 
     
     
       4. Process of claim 1 wherein the catalyst for catalytic aromatization converts C 6  paraffins into benzene at a selectivity of at least 50% of the C 6  paraffins to benzene and the catalyst for catalytic reforming converts C 6  paraffins into benzene at a selectivity of less than 35% of C 6  paraffins to benzene. 
     
     
       5. Process of claim 4 wherein the aromatic extract and non-aromatic raffinate are recovered in a solvent extraction process. 
     
     
       6. Process of claim 5 wherein the catalytic reforming is carried out at temperatures sufficient to convert at least 90% of the C 7  paraffins. 
     
     
       7. Process of claim 6 wherein the catalytic reforming is carried out with a platinum-rhenium gamma alumina catalyst at temperatures of from about 480° C. to 510° C. 
     
     
       8. Process of claim 6 wherein the non-aromatic raffinate recovered in the solvent extraction process is recycled and added to the full boiling range naphtha prior to the separation of step (a). 
     
     
       9. Process of claim 5 further comprising separating the C 8-  effluent into a C 6-  effluent, a C 7  effluent and a C 8  effluent and only the C 6-  effluent and the C 8  effluent are mixed with the C 5+  effluent for the recovery of the aromatic extract in the solvent extraction process. 
     
     
       10. Process of claim 9 wherein the effluent from the catalytic reforming are separated by first fractionating the effluent into a C 6-  effluent, a C 7  effluent and a C 8+  effluent, then fractionating the C 8+  effluent into a C 8  effluent and a C 9+  effluent. 
     
     
       11. Process of claim 5 wherein the non-aromatic raffinate recovered in the solvent extraction process is recycled and added to the C 6  fraction in step (b) for catalytic aromatization. 
     
     
       12. Process of claim 5 wherein the solvent extraction process uses a solvent selected from the group consisting of sulfolane and tetra ethylene glycol. 
     
     
       13. Process of claim 4 wherein the C 6  fraction contains 10 to 50% by volume of C 7+  hydrocarbons. 
     
     
       14. Process of claim 1 wherein the platinum on acidic alumina catalyst also contains a metal chosen from the group consisting of rhenium,. iridium, tungsten, tin and bismuth. 
     
     
       15. Process of claim 1 wherein the catalyst for catalytic aromatization converts the C 6  paraffins into benzene at a yield of at least 40% by volume of C 6  paraffins in the feed and at a selectivity of at least 55% of C 6  paraffins to benzene. 
     
     
       16. Process of claim 15 wherein the catalyst for catalytic aromatization is a platinum type L zeolite catalyt wherein at least 90% of the exchangeable cations are metal ions selected for sodium, lithium, barium, calcium, potassium, strontium, rubidium and cesium. 
     
     
       17. Process of claim 16 wherein the benzene yield is from 5 to 25% by volume of the C 6+  hydrocarbons and 35 to 80% by volume of the C 6  hydrocarbons in the full boiling range hydrocarbon feed. 
     
     
       18. The process of claim 15 where the catalyst is platinum potassium type L zeolite. 
     
     
       19. Process of claim 1 wherein the hydrocarbon feed is a naphtha having a boiling range up to about 350° F. .Iadd. 
     
     
       20.  A process for reforming a hydrocarbon feed comprising: (a) separating said hydrocarbon feed into a lighter fraction, comprising at least one member selected from the group consisting of C 6 , C 7 , and C 8  hydrocarbons, and a heavier fraction;   (b) reforming said lighter fraction under reforming conditions in a reformer in the presence of a non-acidic catalyst, said non-acidic catalyst comprising a non-acidic zeolite support, to produce a first reformate;   (c) reforming said heavier fraction under reforming conditions in the presence of an acidic catalyst to produce a second reformate;   (d) introducing said first reformate into an extraction unit;   (e) separating and removing an aromatic extract stream and a non-aromatic raffinate stream from said extraction unit; and   (f) recycling said non-aromatic raffinate stream to said hydrocarbon feed for reforming under reforming conditions in the presence of a non-acidic catalyst to produce a stream comprising benzene..Iaddend. .Iadd.21. The process as defined by claim 20, wherein said non-acidic catalyst further comprises at least one metal selected from the group consisting of Group VIII metals, tin, and germanium, said at least one metal comprising at least one Group VIII metal having a dehydrogenating effect..Iaddend. .Iadd.22. The process as defined by claim 20, wherein said zeolite is selected from the group consisting of zeolite L, zeolite X, and zeolite Y..Iaddend. .Iadd.23. The process as defined by claim 22, wherein said zeolite is zeolite L..Iaddend. .Iadd.24. The process as defined by claim 23, wherein said zeolite L has exchangeable cations, at least 90% of said exchangeable cations being metal ions selected from the group consisting of sodium, lithium, barium, calcium, potassium, strontium, rubidium and cesium..Iaddend. .Iadd.25. The process as defined by claim 21, wherein said at least one metal comprises platinum..Iaddend. .Iadd.26. The process as defined by claim 20, wherein said lighter fraction comprises C 6 , C 7 , and C 8  hydrocarbons..Iaddend. .Iadd.27. The process as defined by claim 20 wherein said lighter fraction is a C 6  -C 7  fraction containing at least 10% by volume C 7+  hydrocarbons, and said heavier fraction is a C 7+  fraction..Iaddend. .Iadd.28. A process for reforming a hydrocarbon feed comprising:   (a) separating said hydrocarbon feed into a lighter fraction, comprising at least one member selected from the group consisting of C 6 , C 7 , and C 8  hydrocarbons, and a heavier fraction;   (b) reforming said lighter fraction under reforming conditions in the presence of a non-acidic catalyst, said non-acidic catalyst comprising a non-acidic zeolite support, to produce a first reformate;   (c) reforming said heavier fraction under reforming conditions in the presence of an acidic catalyst to produce a second reformate;   (d) introducing said first reformate into an extraction unit;   (e) separating and removing an aromatic extract stream and a non-aromatic raffinate stream from said extraction unit; and   (f) recycling said non-aromatic raffinate stream to said lighter fraction for reforming under reforming conditions in the presence of a non-acidic catalyst to produce a stream comprising benzene..Iaddend. .Iadd.29. The process as defined by claim 28, wherein said non-acidic catalyst further comprises at least one metal selected from the group consisting of Group VIII metals, tin, and germanium, said at least one metal comprising at least one Group VIII metal having a dehydrogenating effect..Iaddend.   
     
     
        .Iadd.0.  The process as defined by claim 28, wherein said zeolite is selected from the group consisting of zeolite L, zeolite X, and zeolite Y..Iaddend. .Iadd.31. The process as defined by claim 30, wherein said zeolite is zeolite L..Iaddend. .Iadd.32. The process as defined by claim 31, wherein said zeolite L has exchangeable cations, at least 90% of said exchangeable cations being metal ions selected from the group consisting of sodium, lithium, barium, calcium, potassium, strontium, rubidium and cesium..Iaddend. .Iadd.33. The process as defined by claim 29, wherein said at least one metal comprises platinum..Iaddend. .Iadd.34. The process as defined by claim 28, wherein said lighter fraction comprises C 6 , C 7 , and C 8  hydrocarbons..Iaddend. .Iadd.35. The process as defined by claim 28, wherein said lighter fraction is a C 6  -C 7  fraction containing at least 10% by volume C 7+  hydrocarbons, and said heavier fraction is a C 7+  fraction..Iaddend. .Iadd.36. The process for reforming a hydrocarbon feed comprising: (a) separating a full boiling range naphtha feed stream into at least two fractions;   (b) contacting one of said fractions of said naphtha feed in an aromatizer reactor with a catalyst at process conditions which favor dehydrocyclization to produce an aromatics product, wherein said catalyst is a non-acidic catalyst comprising a zeolite containing at least one Group VIII metal;   (c) reforming another of said fractions of said naphtha feed in the presence of an acidic catalyst to produce an effluent;   (d) separating components comprising normal paraffins and single-branched isoparaffins present in said aromatics product as non-aromatic raffinate; and   (e) recycling said non-aromatic raffinate to said one fraction of said naphtha feed to said aromatizer reactor..Iaddend. .Iadd.37. The process as defined by claim 36 wherein said separating in step (d) is carried out by solvent extraction..Iaddend. .Iadd.38. The process as defined by claim 37, wherein said solvent is sulfolane..Iaddend. .Iadd.39. The process as defined by claim 36, wherein said zeolite is a type L zeolite..Iaddend. .Iadd.40. The process as defined by claim 39, wherein said catalyst contains a metal selected from the group consisting of metals of Group VIII of the periodic table of elements, tin and germanium..Iaddend. .Iadd.41. The process as defined by claim 40, wherein said metal includes at least one metal of the periodic table having a dehydrogenating effect..Iaddend. .Iadd.42. The process as defined by claim 41, wherein said metal is platinum..Iaddend. .Iadd.43. The process as defined by claim 42, wherein said catalyst comprises exchangeable cations selected from the group consisting of sodium, lithium, barium, calcium, potassium, strontium, rubidium, and cesium..Iaddend. .Iadd.44. The process as defined by claim 43, wherein said exchangeable cation is potassium..Iaddend. .Iadd.45. The process as defined by claim 43, wherein said exchangeable cation is barium..Iaddend. .Iadd.46. A process for reforming a hydrocarbon feed comprising:   (a) separating said hydrocarbon feed into a first fraction and a second fraction;   (b) separating said second fraction into a lighter fraction, comprising at least one member selected from the group consisting of C 6 , C 7 , and C 8  hydrocarbons, and a heavier fraction;   (c) reforming said lighter fraction under reforming conditions in the presence of a non-acidic catalyst, said non-acidic catalyst comprising a non-acidic zeolite support, to produce a first reformate;   (d) reforming said heavier fraction under reforming conditions in the presence of an acidic catalyst to produce a second reformate;   (e) introducing said first reformate into an extraction unit; and   (f) separating and removing an aromatic extract stream and a non-aromatic raffinate stream from said extraction unit;   (g) recycling said non-aromatic raffinate stream to said hydrocarbon feed for reforming under reforming conditions in the presence of a non-acidic   
     
     
        catalyst to produce a stream comprising benzene..Iaddend. .Iadd.47.  The process as defined by claim 46, wherein said non-acidic catalyst further comprises at least one metal selected from the group consisting of Group VIII metals, tin and germanium, said at least one metal comprising at least one Group VIII metal having a dehydrogenating effect..Iaddend. .Iadd.48. The process as defined by claim 46, wherein said zeolite is selected from the group consisting of zeolite L, zeolite X, and zeolite Y..Iaddend. .Iadd.49. The process as defined by claim 48, wherein said zeolite is zeolite L..Iaddend. .Iadd.50. The process as defined by claim 49, wherein said zeolite L has exchangeable cations, at least 20% of said exchangeable cations being metal ions selected from the group consisting of sodium, lithium, barium, calcium, potassium, strontium, rubidium and cesium..Iaddend. .Iadd.51. The process as defined by claim 47, wherein said at least one metal comprises platinum..Iaddend. .Iadd.52. The process as defined by claim 46, wherein said first fraction is a C 5  - fraction, and said second fraction is a C 6  + fraction..Iaddend. .Iadd.53. The process as defined by claim 46, wherein said lighter fraction comprises C 6 , C 7 , and C 8  hydrocarbons..Iaddend. 
     
     
        .Iadd.54.  A process for reforming a hydrocarbon feed comprising: (a) separating said hydrocarbon feed into a first fraction and a second fraction;   (b) separating said second fraction into a lighter fraction, comprising at least one member selected from the group consisting of C 6 , C 7 , and C 8  hydrocarbons, and a heavier fraction;   (c) reforming said lighter fraction under reforming conditions in the presence of a non-acidic catalyst, said non-acidic catalyst comprising a non-acidic zeolite support, to produce a first reformate; and   (d) reforming said heavier fraction under reforming conditions in the presence of an acidic catalyst to produce a second reformate.   (e) introducing said first reformate into an extraction unit;   (f) separating and removing an aromatic extract stream and a non-aromatic raffinate stream from said extraction unit;   (g) recycling said non-aromatic raffinate stream to said hydrocarbon feed for reforming under reforming conditions in the presence of a non-acidic catalyst to produce a stream comprising benzene..Iaddend. .Iadd.55. The process as defined by claim 54, wherein said non-acidic catalyst further comprises at least one metal selected from the group consisting of Group VIII metals, tin, and germanium, said at least one metal comprising at least one Group VIII metal having a dehydrogenating effect..Iaddend. .Iadd.56. The process as defined by claim 54, wherein said zeolite is selected from the group consisting of zeolite L, zeolite X, and zeolite Y..Iaddend. .Iadd.57. The process as defined by claim 56, wherein said zeolite is zeolite L..Iaddend. .Iadd.58. The process as defined by claim 57, wherein said zeolite L has exchangeable cations, at least 90% of said exchangeable cations being metal ions selected from the group consisting of sodium, lithium, barium, calcium, potassium, strontium, rubidium and cesium..Iaddend. .Iadd.59. The process as defined by claim 55, wherein said at least one metal comprises platinum..Iaddend. .Iadd.60. The process as defined by claim 54, wherein said first fraction is a C 5  - fraction, and said second fraction is a C 6  + fraction..Iaddend. .Iadd.61. The process as defined by claim 54, wherein said lighter fraction comprises C 6 , C 7 , and C 8  hydrocarbons..Iaddend.