CONVERSION OF ETHANE IN SHALE GAS TO VALUABLE CHEMICALS

Abstract

A process for producing valuable aromatic hydrocarbons from a crude or semi-crude shale gas stream. A crude or semi-crude shale gas stream including methane is introduced into a reactor that converts at least a portion of the ethane component into aromatic hydrocarbons. Unreacted methane, other hydrocarbons, and hydrogen may then be easily separated from the aromatic hydrocarbons. Because methane is not separated from the shale gas stream, the expensive and resource-consuming shale gas C1/C2+ separation step is avoided.

Claims

1. A process for the production of BTX aromatic hydrocarbons from shale gas, the process comprising: (a) reacting shale gas comprising methane, ethane, and C2+ hydrocarbons under conditions sufficient to produce a first stream comprising BTX aromatic hydrocarbons, methane, hydrogen, and unreacted ethane and C2+ hydrocarbons; (b) contacting the first stream with a solvent to produce a second stream and a third stream, wherein the second stream comprises methane, hydrogen, and unreacted ethane and C2+ hydrocarbons, and the third stream comprises the solvent and the BTX aromatic hydrocarbons; and (c) removing the solvent from the third stream.

2. The process of claim 1, wherein water and hydrates are removed from the shale gas prior to step (a).

3. The process of claim 2, wherein water and hydrates are removed from the shale gas prior to step (a).

4. The process of claim 2, wherein the step of reacting the shale gas comprises heating the shale gas to a temperature ranging from about 400° C. to about 700° C.

5. The process of claim 2, wherein the step of contacting the first stream with a solvent comprises contacting the first stream with an aromatic selective solvent.

6. The process of claim 5, wherein the aromatic selective solvent is selected from the group consisting of 1-methylnaphthalene, mono-ethylene glycol, di-ethylene glycol, tri-ethylene glycol, tetra-ethylene glycol, tetrahydrothiophene dioxide, N-methylpyrrolidone, dimethylsulfoxide, propylene carbonate, phenol, cresol, N-formylmorpholine, monomethylformamide, N-methyl-ε-caprolactam and water, or combinations thereof.

7. The process of claim 1 wherein the solvent is removed from the third steam by distilling the third stream to produce a product stream comprising the BTX aromatic hydrocarbons and a fourth stream comprising the solvent; and (d) recycling the fourth stream to step (b).

8. The process of claim 7, wherein water and hydrates are removed from the shale gas prior to step (a).

9. The process of claim 8, wherein water and hydrates are removed from the shale gas prior to step (a).

10. The process of claim 7, wherein the step of reacting the shale gas comprises heating the shale gas to a temperature ranging from about 400° C. to about 700° C.

11. The process of claim 7, wherein the step of contacting the first stream with a solvent comprises contacting the first stream with an aromatic selective solvent.

12. The process of claim 11, wherein the aromatic selective solvent is selected from the group consisting of 1-methylnaphthalene, mono-ethylene glycol, di-ethylene glycol, tri-ethylene glycol, tetra-ethylene glycol, tetrahydrothiophene dioxide, N-methylpyrrolidone, dimethylsulfoxide, propylene carbonate, phenol, cresol, N-formylmorpholine, monomethylformamide, N-methyl-ε-caprolactam and water, or combinations thereof.

13. The process of claim 12, further comprising the step of distilling the BTX aromatic hydrocarbons to recover benzene.

14. The process of claim 1, wherein the step of reacting the shale gas comprises heating the shale gas to a temperature ranging from about 400° C. to about 700° C.; wherein the step of separating the first stream comprises cooling the first stream to a temperature ranging from about 30° C. to about 100° C.; and wherein the step or reacting the shale gas occurs in a catalytic aromatization unit.

15. The process of claim 14, wherein water and hydrates are removed from the shale gas prior to step (a).

16. The process of claim 2, wherein the step of reacting the shale gas comprises heating the shale gas to a temperature ranging from about 400° C. to about 700° C.

17. The process of claim 2, wherein the step of contacting the first stream with a solvent comprises contacting the first stream with an aromatic selective solvent.

18. The process of claim 5, wherein the aromatic selective solvent is water.

19. The process of claim 8, wherein the step of reacting the shale gas comprises heating the shale gas to a temperature of 400° C.

20. The process of claim 8, wherein the step of contacting the first stream with a solvent comprises contacting the first stream with an aromatic selective solvent, wherein the aromatic selective solvent is water.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0026] FIG. 1 is a schematic of the inventive process. Water and hydrates are removed from shale gas, and the crude shale gas, having methane as its primary component, is provided to an aromatics reactor. At least a portion of the ethane is converted into aromatic hydrocarbons. The aromatic hydrocarbons are separated from the methane, hydrogen, and unconverted C2+ components in an absorption column. The solvent is stripped from the aromatic hydrocarbons and recycled to the absorption column.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention provides a process for producing valuable aromatic hydrocarbons from a crude or semi-crude shale gas stream. Although methane is the primary component of most shale gas, the fractions of other constituents, e.g., ethane, propane, nitrogen, water, and CO.sub.2 varies based upon the gas deposit's geographical location.

[0028] In order to convert shale gas non-methane hydrocarbons into more valuable aromatic compounds, methane is first separated from C2+ hydrocarbons using expensive processes like cryogenic distillation separation and molecular sieves filtering. According to the instant disclosure, the methane/C2+ separation can be avoided, and a crude or semi-crude shale gas stream can be used as a feed stream for a reforming process like catalytic aromatization. At least a portion of the ethane component in the shale gas stream is converted into aromatic hydrocarbons. Unreacted methane, other hydrocarbons, and hydrogen may then be easily separated from the aromatic hydrocarbons. Because methane is not separated from the shale gas stream prior to reforming, the expensive and resource-consuming shale gas C1/C2+ separation step is avoided. The present invention therefore provides a method for the production of aromatic hydrocarbons at a reduced cost.

[0029] These and other non-limiting aspects of the present invention are discussed in further detail herein.

[0030] In the exemplary process 100 depicted in FIG. 1, water and hydrates are first removed from shale gas to produce a crude or semi-crude shale gas stream 101. The shale gas stream has a typical composition of 80-85 wt. % methane, 10-15 wt. % ethane and 5-10 wt. % C2+ hydrocarbons. The shale gas stream 101 is heated up to a temperature of 600-700° C. and is sent to an aromatics reactor 102 which reforms at least a portion of the ethane and higher hydrocarbons into aromatic compounds. The effluent 103 coming out the aromatics reactor 102 is cooled to a temperature of 50° C. and sent to a solvent absorption column 104 to absorb the aromatics. Effluent 103 will contain the aromatics, unconverted methane, unconverted ethane, unconverted C2+ hydrocarbons and hydrogen. The aromatic+ solvent stream 105 from the absorber is sent to series of distillation columns 106 where in BTX 107 is separated from the solvent 108, and the solvent 108 is recycled back to the absorption column 104. The BTX separation can be carried out in a Divided Wall Column in order to improve process energy efficiency. The gas stream 109 coming out of the absorption column consists primarily of methane, unconverted ethane and hydrogen. The presence of hydrogen in methane increases lower heating value (LHV) of the gas.

[0031] In the context of the present invention, embodiments 1-19 are described. Embodiment 1 is a process for the production of BTX aromatic hydrocarbons from shale gas, including reacting shale gas comprising methane, ethane, and C2+ hydrocarbons under conditions sufficient to produce a first stream comprising BTX aromatic hydrocarbons, methane, hydrogen, and unreacted ethane and C2+ hydrocarbons; contacting the first stream with a solvent to produce a second stream and a third stream, wherein the second stream comprises methane, hydrogen, and unreacted ethane and C2+ hydrocarbons, and the third stream comprises the solvent and the BTX aromatic hydrocarbons; and removing the solvent from the third stream. Embodiment 2 is the process of embodiment 1, wherein the methane in the shale gas remains essentially unreacted. Embodiment 3 is the process of either of embodiments 1 or 2, wherein water and hydrates are removed from the shale gas prior to the first step of embodiment 1 above. Embodiment 4 is the process of any of embodiments 1 to 3, wherein the step of reacting the shale gas comprises heating the shale gas to a temperature ranging from about 400° C. to about 700° C. Embodiment 5 is the process of any of embodiments 1 to 4, wherein the step of contacting the first stream with a solvent comprises contacting the first stream with an aromatic selective solvent. Embodiment 6 is the process of any of embodiments 1 to 5, wherein the aromatic selective solvent is selected from the group consisting of 1-methylnaphthalene, mono-ethylene glycol, di-ethylene glycol, tri-ethylene glycol, tetra-ethylene glycol, tetrahydrothiophene dioxide, N-methylpyrrolidone, dimethylsulfoxide, propylene carbonate, phenol, cresol, N-formylmorpholine, monomethylformamide, N-methyl-ε-caprolactam, water, and combinations thereof.

[0032] Embodiment 7 is a process for the production of BTX aromatic hydrocarbons from shale gas, including reacting shale gas containing methane, ethane, and C2+ hydrocarbons under conditions sufficient to produce a first stream containing BTX aromatic hydrocarbons, methane, hydrogen, and unreacted ethane and C2+ hydrocarbons, then contacting the first stream with a solvent to produce a second stream and a third stream, wherein the second stream contains methane, hydrogen, and unreacted ethane and C2+ hydrocarbons, and the third stream contains the solvent and the BTX aromatic hydrocarbons, distilling the third stream to produce a product stream comprising the BTX aromatic hydrocarbons and a fourth stream comprising the solvent; and recycling the fourth stream to the step of contacting the first stream with a solvent. Embodiment 8 is the process of embodiment 7, wherein the methane in the shale gas remains essentially unreacted. Embodiment 9 is the process of either of embodiments 7 or 8, wherein water and hydrates are removed from the shale gas prior to the first step of embodiment 7 above. Embodiment 10 is the process of any of embodiments 7 to 9, wherein the step of reacting the shale gas includes heating the shale gas to a temperature ranging from about 400° C. to about 700° C. Embodiment 11 is the process of any of embodiments 7 to 10, wherein the step of contacting the first stream with a solvent includes contacting the first stream with an aromatic selective solvent. Embodiment 12 is the process of embodiment 10, wherein the aromatic selective solvent is selected from the group consisting of 1-methylnaphthalene, mono-ethylene glycol, di-ethylene glycol, tri-ethylene glycol, tetra-ethylene glycol, tetrahydrothiophene dioxide, N-methylpyrrolidone, dimethylsulfoxide, propylene carbonate, phenol, cresol, N-formylmorpholine, monomethylformamide, N-methyl-ε-caprolactam, water, and combinations thereof. Embodiment 13 is the process of embodiment 12, further comprising the step of distilling the BTX aromatic hydrocarbons to recover benzene.

[0033] Embodiment 14 is a process for the production of BTX aromatic hydrocarbons from shale gas, including reacting shale gas containing methane, ethane, and C2+ hydrocarbons under conditions sufficient to produce a first stream containing BTX aromatic hydrocarbons, methane, hydrogen, and unreacted ethane and C2+ hydrocarbons, then separating the first stream to produce a second stream and a third stream, wherein the second stream comprises methane and hydrogen, the third stream comprises the BTX aromatic hydrocarbons; wherein the methane in the shale gas remains essentially unreacted. Embodiment 15 is the process of embodiment 14, wherein water and hydrates are removed from the shale gas prior to the first step of embodiment 14 above. Embodiment 16 is the process of either of embodiments 14 or 15, wherein the step of reacting the shale gas occurs in a catalytic aromatization unit. Embodiment 17 is the process of embodiment 16, wherein the catalytic aromatization unit comprises a catalyst selected from the group consisting of Ga-ZSM-5, Zn-ZSM-5, Pt-ZSM-5, Mo-ZSM-5, Ru-ZSM-5, and Re-ZSM-5. Embodiment 18 is the process of any of embodiments 14 to 17, and includes heating the shale gas to a temperature ranging from about 400° C. to about 700° C. Embodiment 19 is the process of any of embodiments 14 to 18, wherein the step of separating the first stream comprises cooling the first stream to a temperature ranging from about 30° C. to about 100° C.

Simulated Example

[0034] Water and hydrates will be removed from shale gas to provide a shale gas stream containing methane and ethane which will be sent through an aromatization reactor at a pressure of 5-10 bara a rate of 80.0 moles/hr methane and 20.0 moles/hr ethane, with no propane or butane content. The shale gas stream will be heated up to a temperature in the range of 600-700° C. prior to entering the aromatization reactor to reform at least a portion of the ethane and higher hydrocarbons into aromatic compounds. The effluent from the aromatization reactor has the following composition shown in Table 1:

TABLE-US-00001 TABLE 1 Methane 86.0 moles/hr Ethane 5.0 moles/hr Propane — moles/hr Butane — moles/hr Ethylene 0.9 moles/hr Benzene 2.0 moles/hr Toluene 0.6 moles/hr Xylene 0.2 moles/hr Naphthalene 0.2 moles/hr Hydrogen 21.0 moles/hr Coke 3.0 moles/hr Total 115.8 moles/hr

[0035] The effluent from the aromatization reactor will then be cooled to a temperature of 50° C. and sent to an absorption column at a pressure of 5-10 bara to absorb the aromatics (BTX). A gas stream exits the absorber and has the content shown in Table 2:

TABLE-US-00002 TABLE 2 Methane 86.0 moles/hr Ethane  5.0 moles/hr Propane — moles/hr Butane — moles/hr Ethylene  0.9 moles/hr Hydrogen 21.0 moles/hr

[0036] The remaining effluent from the absorber is sent to a separator to separate the solvent, which is recycled to the absorber at a rate of approximately 300-600 kg/hr. The solvent in this example is mono-ethylene glycol, and liquid products in the additional effluent from the absorber are separated. This effluent was shown to have the composition shown in Table 3:

TABLE-US-00003 TABLE 3 Benzene 2.0 moles/hr Toluene 0.6 moles/hr Xylene 0.2 moles/hr Naphthalene 0.2 moles/hr

[0037] Analysis reveals that this example provides carbon selectivities as follows:

TABLE-US-00004 Component Selectivity, Carbon % Methane 20 Ethylene 6 Benzene 40 Toluene 15 Xylene 4 Heavies 5 Coke 10

[0038] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.