PROCESS FOR PRODUCING BTX AND LPG

Abstract

The invention is directed to a process for producing BTX and LPG, comprising: a) contacting a feed stream comprising C5-C12 hydrocarbons in the presence of hydrogen with a hydrocracking catalyst in a hydrocracking reactor to produce a hydrocracking product stream comprising hydrogen, methane, LPG and BTX, b) separating the hydrocracking product stream into a first gas stream and a first liquid stream, c) separating the first gas stream to obtain a second gas stream comprising hydrogen and methane and a second liquid stream comprising LPG and BTX, wherein the separation is performed such that the second liquid stream is substantially free of hydrogen and methane, d) separating the second liquid stream into a third gas stream comprising LPG and a third liquid stream comprising BTX, wherein step (c) involves adding a part of the third liquid stream to the first gas stream to absorb the LPG in the first gas stream to obtain the second liquid stream or adding a part of the third liquid stream to a gas stream sep crated from the first gas stream to absorb the LPG in said gas stream separated from the first gas stream to obtain the second liquid stream.

Claims

1. A process for producing BTX and LPG, comprising: (a) contacting a feed stream comprising C5-C12 hydrocarbons in the presence of hydrogen with a hydrocracking catalyst in a hydrocracking reactor to produce a hydrocracking product stream comprising hydrogen, methane, LPG and BTX, (b) separating the hydrocracking product stream into a first gas stream and a first liquid stream, (c) separating the first gas stream to obtain a second gas stream comprising hydrogen and methane and a second liquid stream comprising LPG and BTX, wherein the separation is performed such that the second liquid stream is substantially free of hydrogen and methane, (d) separating the second liquid stream into a third gas stream comprising LPG and a third liquid stream comprising BTX, wherein step (c) involves adding a part of the third liquid stream to the first gas stream to absorb the LPG in the first gas stream to obtain the second liquid stream or adding a part of the third liquid stream to a gas stream separated from the first gas stream to absorb the LPG in said gas stream separated from the first gas stream to obtain the second liquid stream.

2. The process according to claim 1, wherein step (c) involves (c1) separating the first gas stream into a gas stream and a liquid stream and (c2) adding the part of the third liquid stream to the gas stream obtained by step (c1).

3. The process according to claim 2, wherein step (c2) involves compressing the gas stream obtained by step (c1) and adding the part of the third liquid stream to the compressed gas stream.

4. The process according to claim 1, wherein step (c) involves adding a part of the third liquid stream to the first gas stream.

5. The process according to claim 1, wherein the second liquid stream substantially consists of LPG and BTX.

6. The process according to claim 1, wherein at least part of the second gas stream is fed back to be mixed with the feed stream.

7. The process according to claim 1, wherein the process further comprises step (e) of separating benzene from the third liquid stream.

8. The process according to claim 6, wherein the third liquid stream is separated into benzene and a liquid stream comprising toluene and xylene and the liquid stream comprising toluene and xylene is used for absorbing the LPG in step (c).

9. The process according to claim 1, wherein the part of the third liquid stream to be added to the first gas stream is cooled to a temperature below 0 C. before being added to the first gas stream.

10. The process according to claim 1, wherein the part of the third liquid stream to be added to the first gas stream is cooled to 40 C. to 30 C. before being added to the first gas stream.

11. The process according to claim 1, wherein the part of the third liquid stream to be added to the first gas stream is cooled to a temperature 0.5-5 C. higher than the temperature at which the third liquid stream freezes, before being added to the first gas stream.

12. The process according to claim 1, wherein the hydrocracking catalyst of step (a) comprises 0.01-1 wt-% hydrogenation metal in relation to the total catalyst weight and a zeolite having a pore size of 5-8 and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200 and step (a) is performed under process conditions including a temperature of 425-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-15 h.sup.1.

13. The process according to claim 12, wherein the hydrogenation metal of the hydrocracking catalyst is at least one element selected from Group 10 of the periodic table of Elements.

14. The process according to claim 12, wherein the zeolite is selected from the group consisting of ZSM-5, MCM-22, ZSM-11, beta zeolite, EU-1 zeolite, zeolite Y, faujastite, ferrierite and mordenite.

15. The process according to claim 1, wherein the feed stream comprises pyrolysis gasoline, straight run naphtha, light coker naphtha and coke oven light oil, FCC gasoline, reformate or mixtures thereof.

16. The process according to claim 13, wherein the hydrogenation metal is Pt.

17. The process according to claim 14, wherein the zeolite is ZSM-5.

18. The process according to claim 15, wherein the feed stream is depentanized.

Description

[0087] The present invention is further elucidated referring to the drawings in which:

[0088] FIG. 1 illustrates a scheme of an example of a process not according to the invention and

[0089] FIG. 2 illustrates a scheme of an example of a process according to the invention.

[0090] FIG. 1 illustrates a scheme of an example of a process not according to the invention. A feed stream comprising C5-C12 hydrocarbons is hydrocracked in the reaction section illustrated in the left part of the figure and the obtained hydrocracking product stream comprising hydrogen, methane, LPG and BTX is fed to the separation section illustrated in the right part of the figure via a heat exchanger H-003.

[0091] The hydrocracking product stream is fed to a heat exchanger H-003 where it is cooled to e.g. 140 C., after which it is fed to a flash vessel V0001. The hydrocracking product stream is separated in the flash vessel V001 into a gas stream and a liquid stream. The gas stream from the flash vessel V0001 is compressed in a compressor K0002 and separated again in a flash vessel V002 at e.g. 100 C. into a gas stream and a liquid stream. The flash vessel V002 separates most of C4+ hydrocarbons as a liquid stream from a gas stream. From the flash vessel V002 a gas stream mostly comprising hydrogen and C1-C3 hydrocarbons is led to a heat exchanger H005 which compresses the gas to e.g. 30 bar and 100 C. and then to a flash vessel V003 wherein a cryogenic separation between hydrogen and methane and C2-C3 hydrocarbons is performed. The gas stream containing hydrogen and methane is recycled to the reaction section, wherein it is partly recycled and partly purged. The liquid stream leaving the flash vessel V003 comprising C2-C3 is combined with the LPG stream obtained from the liquid stream from V001.

[0092] The liquid steam leaving V001 is, together with the liquid stream coming from V002, fed to a distillation column C001 via a heat exchanger H006. In the distillation column C001 the liquid steam is separated into an LPG stream and a BTX stream. The BTX stream is fed to a distillation column C002 for separation of the BTX stream in a stream 17 of lighter products, a benzene stream 18 and a toluene/xylene stream 19.

[0093] FIG. 2 illustrates a scheme of an example of a process according to the invention. The reaction section of FIG. 2 is the same as that of FIG. 1.

[0094] In the separation section illustrated in FIG. 2, the hydrocracking product stream is fed to a flash vessel V001, where it is separated into a gas stream and a liquid stream. The gas stream from the flash vessel V001 is heated in a heat exchanger H003 and separated again in a flash vessel V002. The gas stream from the flash vessel V002 is compressed in a compressor K002 and fed to a distillation column C003.

[0095] The liquid streams from V001, V002 and C003 go through a heat exchanger H004 and enter a distillation column C001, which separates the liquid streams into an LPG stream and a BTX stream. Part of the BTX stream is led to a distillation column C002 for separation of the BTX stream into a stream of lighter products, a benzene stream and a toluene/xylene stream. A part of the BTX stream is fed via a pump 003 to the top of the distillation column C003. In the distillation column C003 this BTX stream is used to obtain a better separation between hydrogen and methane and the heavier components in the gas mixture fed to C003. As already described, the liquid stream leaving C003 is combined with the liquid streams from V001 and V002 and fed to the distillation column C001.