Hydrocracking process and system including separation of heavy poly nuclear aromatics from recycle by ionic liquids and solid adsorbents

1. A process for the treatment of a hydrocracking unit bottoms stream obtained from a hydrocracking operation containing heavy poly-nuclear aromatic (HPNA) compounds that are derived from the hydrocracking operation prior to use within the hydrocracking operation to reduce the content of HPNA compounds, the process comprising:

a. contacting the bottoms stream from the hydrocracking operation with an effective amount of adsorbent material in an adsorption vessel to produce an adsorbent-treated bottoms stream having a reduced content of HPNA compounds;

b. recovering and introducing the adsorbent-treated bottoms stream into an extraction unit with one or more ionic liquids for a predetermined time to extract the HPNA compounds and produce an extraction unit effluent stream containing extracted HPNA compounds and ionic liquid, and an ionic liquid treated stream having a reduced content of HPNA compounds and residual ionic liquid;

c. recovering and introducing the effluent stream from the extraction unit containing the extracted HPNA compounds and ionic liquid into a separation unit for contact with an organic polar solvent;

d. maintaining the extraction unit effluent stream from the extraction unit containing extracted HPNA compounds and ionic liquid in the separation unit for a time that is sufficient to form a solution of the HPNA compounds in the organic polar solvent;

e. recovering ionic liquid from the separation unit for re-use in the extraction unit, and discharging a stream containing solvent and HPNA compounds stream;

f. transferring the stream containing solvent and HPNA compounds to a solvent recovery unit, and recovering a solvent stream for re-use in the separation unit;

g. transferring from the extraction unit the ionic liquid treated stream having reduced HPNA compounds to a liquid-liquid separator and recovering as separate streams

(i) an ionic liquid treated hydrocarbon stream having a substantially reduced content of HPNA compounds, and

(ii) a stream containing residual ionic liquid and HPNA compounds; and

h. using all or a portion of the treated hydrocarbon stream having a substantially reduced content of HPNA compounds as feed within the hydrocracking operation.

2. The process of claim 1 in which a fresh hydrocracking unit feed is combined with the hydrocracking unit bottoms stream, prior to the contacting with adsorbent in the adsorption vessel, to produce a combined stream, and wherein the combined stream is treated in the adsorption vessel.

3. The process of claim 1 in which the one or more ionic liquids is of the general formula Q + A − ,

wherein the A − ion is selected from the group consisting of halide anions, nitrate, sulfate, phosphate, acetate, haloacetates, tetrafluoroborate, tetrachloroborate, hexafluorophosphate, hexafluoroantimonate, fluorosulfonate, alkyl sulfonates, perfluoroalkyl sulfonates, bis(perfluoroalkylsulfonyl)amides, tris-trifluoromethanesulfononyl methylide of the formula C(CF 3 SO 2 ) 3 —, unsubstituted arenesulfonates, arenesulfonates substituted by halogen or haloalkyl groups, and

wherein the Q + ion is an ammonium cation, a phosphonium cation or a sulfonium cation that will form a liquid compound with an A − ion.

4. The process of claim 3 in which the one or more ionic liquids is selected from the group consisting of N-butyl-pyridinium hexafluorophosphate, N-ethyl-pyridinium tetrafluoroborate, pyridinium fluorosulfonate, butyl-3-methyl-1-imidazolium tetrafluoroborate, butyl-3-methyl-1-imidazolium bis-trifluoromethane-sulfonyl amide, triethylsulfonium bis-trifluoromethane-sulfonyl amide, butyl-3-methyl-1-imidazolium hexafluoro-antimonate, butyl-3-methyl-1-imidazolium hexafluorophosphate, butyl-3-methyl-1-imidazolium trifluoroacetate, butyl-3-methyl-1-imidazolium trifluoromethylsulfonate, butyl-3-methyl-1-imidazolium bis(trifluoromethylsulfonyl)-amide, trimethyl-phenylammonium hexafluorophosphate, tetrabutylphosphonium tetrafluoroborate, and mixtures thereof.

5. The process of claim 1 in which the extraction unit operates at a temperature in the range of from 20° to 200° C., a pressure in the range of from 1 to 30 bars, and at a mole ratio of ionic liquid-to-HPNA in the range of from 1:1 to 10:1.

6. The process of claim 1 in which the extraction unit is selected from the group consisting of tray columns, spray columns, packed towers, rotating disc contactors and pulse columns.

7. The process of claim 1 in which the adsorbent material is in an adsorption column in the form of a packed bed or slurry bed.

8. The process of claim 7 in which the adsorption column operates at a temperature in the range of from 20° to 200° C. and a pressure in the range of from 1 to 30 bars.

9. The process of claim 1 in which the adsorbent material is selected from the group consisting of attapulgus clay, alumina, silica, activated carbon, natural and synthetic zeolites, spent catalysts, silica-titania and titania.

10. The process of claim 1 in which the organic polar solvent has an overall solubility parameter greater than about 8.5.

11. The process of claim 9 in which the organic polar solvent is selected from the group consisting of toluene, benzene, xylene, tetrahydrofuran, and mixtures thereof.

12. A process for the treatment of a hydrocracking unit bottoms stream obtained from a hydrocracking operation containing heavy poly-nuclear aromatic (HPNA) compounds that are derived from the hydrocracking operation prior to use within the hydrocracking operation to reduce the content of HPNA compound, the process comprising:

a. introducing the bottoms stream from the hydrocracking operation into an extraction unit with one or more ionic liquids for a predetermined period of time to extract the HPNA compounds and to produce an extraction unit effluent stream containing extracted HPNA compounds and ionic liquid, and an ionic liquid treated stream having a reduced content of HPNA compounds and residual ionic liquid;

b. introducing the extraction unit effluent stream containing the extracted HPNA compounds and ionic liquid into a separation unit for contact with an organic polar solvent;

c. mixing the extraction unit effluent stream containing the extracted HPNA compounds and ionic liquid in the separation unit for a time that is sufficient to form a solution of the HPNA compounds in the organic polar solvent;

d. recovering ionic liquid from the separation unit for re-use in the extraction unit and discharging a stream containing solvent and HPNA compounds;

e. transferring the stream containing solvent and HPNA compounds to a solvent recovery unit, and recovering a solvent stream for re-use in the separation unit;

f. transferring from the extraction unit the ionic liquid treated stream having a reduced content of HPNA compounds to a liquid-liquid separator and recovering as separate streams

(i) an ionic liquid treated hydrocarbon stream having a substantially reduced content of HPNA compounds, and

(ii) a stream containing residual ionic liquid and HPNA compounds;

g. contacting the ionic liquid treated hydrocarbon stream with an effective amount of adsorbent material to produce an adsorbent-treated hydrocarbon stream having a reduced content of HPNA compounds;

h. recovering the adsorbent-treated stream having a reduced content of HPNA compounds; and

i. using all or a portion of the adsorbent-treated stream having a reduced content of HPNA compounds as feed within the hydrocracking operation.

13. The process of claim 12 , in which a fresh hydrocracking unit feed is combined with the hydrocracking unit bottoms stream, prior to the introduction into the extraction unit, to produce a combined stream, and wherein the combined stream is treated in the extraction unit.

14. The process of claim 12 in which the one or more ionic liquids is of the general formula Q + A − ,

wherein the A − ion is selected from the group consisting of halide anions, nitrate, sulfate, phosphate, acetate, haloacetates, tetrafluoroborate, tetrachloroborate, hexafluorophosphate, hexafluoroantimonate, fluorosulfonate, alkyl sulfonates, perfluoroalkyl sulfonates, bis(perfluoroalkylsulfonyl)amides, tris-trifluoromethanesulfononyl methylide of the formula C(CF 3 SO 2 ) 3 —, unsubstituted arenesulfonates, arenesulfonates substituted by halogen or haloalkyl groups, and

wherein the Q + ion is an ammonium cation, a phosphonium cation or a sulfonium cation that will form a liquid compound with an A − ion.

15. The process of claim 14 in which the one or more ionic liquids is selected from the group consisting of N-butyl-pyridinium hexafluorophosphate, N-ethyl-pyridinium tetrafluoroborate, pyridinium fluorosulfonate, butyl-3-methyl-1-imidazolium tetrafluoroborate, butyl-3-methyl-1-imidazolium bis-trifluoromethane-sulfonyl amide, triethylsulfonium bis-trifluoromethane-sulfonyl amide, butyl-3-methyl-1-imidazolium hexafluoro-antimonate, butyl-3-methyl-1-imidazolium hexafluorophosphate, butyl-3-methyl-1-imidazolium trifluoroacetate, butyl-3-methyl-1-imidazolium trifluoromethylsulfonate, butyl-3-methyl-1-imidazolium bis(trifluoromethylsulfonyl)-amide, trimethyl-phenylammonium hexafluorophosphate, tetrabutylphosphonium tetrafluoroborate, and mixtures thereof.

16. The process of claim 12 in which the extraction unit operates at a temperature in the range of from 20° to 200° C., a pressure in the range of from 1 to 30 bars, and at a mole ratio of ionic liquid-to-HPNA in the range of from 1:1 to 10:1.

17. The process of claim 12 in which the extraction unit is selected from the group consisting of tray columns, spray columns, packed towers, rotating disc contactors and pulse columns.

18. The process of claim 12 in which the adsorbent material is in an adsorption column in the form of a packed bed or slurry bed.

19. The process of claim 18 in which the adsorption column operates at a temperature in the range of from 20° to 200° C. and a pressure in the range of from 1 to 30 bars.

20. The process of claim 12 in which the adsorbent material is selected from the group consisting of attapulgus clay, alumina, silica, activated carbon, natural and synthetic zeolites, spent catalysts, silica-titania and titania.

21. The process of claim 12 in which the organic polar solvent has an overall solubility parameter greater than about 8.5.

22. The process of claim 21 in which the organic polar solvent is selected from the group consisting of toluene, benzene, xylene, tetrahydrofuran, and mixture thereof.

23. A two stage hydrocracking process as the hydrocracking operation of claim 1 comprising:

subjecting a hydrocarbon stream to a first hydrocracking stage to produce a first hydrocracked effluent;

fractionating the first hydrocracked effluent to recover one or more hydrocracked product fractions and a bottoms fraction corresponding to the hydrocracking unit bottoms stream of claim 1 ;

and

wherein using all or a portion of the treated hydrocarbon stream having a substantially reduced content of HPNA compounds within the hydrocracking operation comprises passing all or a portion of the treated hydrocarbon stream having a substantially reduced content of HPNA compounds to a second hydrocracking stage to produce a second hydrocracked effluent.

24. The process as in claim 23 , wherein the second hydrocracked effluent is fractionated with the first hydrocracked effluent.

25. A single-stage or series flow hydrocracking process as the hydrocracking operation of claim 1 comprising:

subjecting a hydrocarbon stream to a hydrocracking zone in a single stage hydrocracking process, or one or more hydrocracking zones in series in a series flow hydrocracking process, to produce a hydrocracked effluent;

fractionating the hydrocracked effluent to recover one or more hydrocracked product fractions and a hydrocracked bottoms fraction corresponding to the hydrocracking unit bottoms stream of claim 1 ;

wherein using all or a portion of the treated hydrocarbon stream having a substantially reduced content of HPNA compounds within the hydrocracking operation comprises recycling all or a portion of the treated hydrocarbon stream having a substantially reduced content of HPNA compounds to the hydrocracking zone in a single stage hydrocracking process, or at least one of the one or more hydrocracking zones in a series flow hydrocracking process.

26. A two stage hydrocracking process as the hydrocracking operation of claim 12 comprising:

subjecting a hydrocarbon stream to a first hydrocracking stage to produce a first hydrocracked effluent;

subjecting a hydrocarbon stream to a first hydrocracking stage to produce a first hydrocracked effluent;

fractionating the first hydrocracked effluent to recover one or more hydrocracked product fractions and a bottoms fraction corresponding to the hydrocracking unit bottoms stream of claim 12 ;

and

wherein using all or a portion of the adsorbent-treated stream having a reduced content of HPNA compounds within the hydrocracking operation comprises passing all or a portion of the adsorbent-treated stream having a reduced content of HPNA compounds to a second hydrocracking stage to produce a second hydrocracked effluent.

27. The process as in claim 26 , wherein the second hydrocracked effluent is fractionated with the first hydrocracked effluent.

28. A single-stage or series flow hydrocracking process as the hydrocracking operation of claim 12 comprising:

subjecting a hydrocarbon stream to a hydrocracking zone in a single stage hydrocracking process, or one or more hydrocracking zones in a series in a series flow hydrocracking process, to produce a hydrocracked effluent;

fractionating the hydrocracked effluent to recover one or more hydrocracked product fractions and a hydrocracked bottoms fraction corresponding to the hydrocracking unit bottoms stream of claim 12 ;

wherein using all or a portion of the adsorbent-treated stream having a reduced content of HPNA compounds within the hydrocracking operation comprises recycling all or a portion of the adsorbent-treated stream having a reduced content of HPNA compounds to the hydrocracking zone in a single stage hydrocracking process, or at least one of the one or more hydrocracking zones in a series flow hydrocracking process.

29. The process as in claim 1 , wherein the stream containing residual ionic liquids and HPNA compounds from the liquid-liquid separator is passed to the separation unit for contact with organic solvent.

30. The process as in claim 12 , wherein the stream containing residual ionic liquids and HPNA compounds from the liquid-liquid separator is passed to the separation unit for contact with organic solvent.