MILD CRACKING OF PARAFFINS

Abstract

A process is disclosed for the mild cracking of C7+ paraffins using a supported ionic liquid of the formula AB, wherein: A is a cation capable of forming an ionic liquid, and B is an anion containing aluminum and a halogen which is capable of forming an ionic liquid.

Description

FIELD OF THE INVENTION

The present invention relates to a process for the mild cracking of paraffins. In another aspect, this invention relates to a process for the mild cracking of C₇+ paraffins using a supported ionic liquid.

BACKGROUND OF THE INVENTION

It is known that ionic liquids can be used in various hydrocarbon conversion processes. However, we have found an ionic liquid dispersed on a support which is unexpectedly effective at mildly cracking paraffins at moderate conversion conditions.

SUMMARY OF THE INVENTION

In accordance with the present invention, a process is provided including the following:

(a) contacting a hydrocarbon feed stream comprising C₇+ paraffins having at least seven carbon atoms per molecule with a composition comprising an ionic liquid supported on silica thereby producing a product stream comprising light paraffins having in the range of from four to six carbon atoms per molecule; wherein the ionic liquid has the formula: AB, wherein:

A is a cation capable of forming an ionic liquid, and

B is an anion containing aluminum and a halogen which is capable of forming an ionic liquid.

DETAILED DESCRIPTION OF THE INVENTION

The hydrocarbon feed stream of the present invention can be any feed comprising, consisting of, or consisting essentially of C₇+ paraffins having at least seven carbon atoms per molecule, preferably in the range of from seven to thirty carbon atoms per molecule, more preferably in the range of from seven to fifteen carbon atoms per molecule, and most preferably in the range of from seven to twelve carbon atoms per molecule. Typically, the feed is a heavy straight run naphtha having a boiling range between around 180° F. and around 380° F. Preferably, C₇+ paraffins are present in the hydrocarbon feed stream in an amount in excess of about 50 weight %, more preferably in an amount in excess of about 70 weight %, and most preferably in an amount in excess of about 90 weight %.

The hydrocarbon feed stream is contacted with a composition comprising an ionic liquid supported on silica thereby producing a product stream comprising light paraffins having in the range of from four to six carbon atoms per molecule. The silica of the composition is preferably non-crystalline. The ionic liquid preferably has the formula: AB, wherein:

A is a cation capable of forming an ionic liquid, and B is an anion containing aluminum and a halogen which is capable of forming an ionic liquid.

A is preferably (CH₃)₃NH⁺, and B is preferably an anion selected from the group consisting of Al₂Cl₇⁻, AlCl₄⁻, Al₃CL₁₀⁻, and combinations thereof.

The ionic liquid is present in the composition in an amount in the range of from about 50 wt. % to about 90 wt. %, preferably in the range of from about 60 wt. % to about 90 wt. %, and more preferably in the range of from about 70 wt. % to about 85 wt. %. Silica is present in the composition in an amount in the range of from about 10 wt. % to about 50 wt. %, preferably in the range of from about 10 wt. % to about 40 wt. %, and more preferably in the range of from about 15 wt. % to about 30 wt. %.

The hydrocarbon feed stream is contacted with the composition at a temperature in the range of from about 50° C. to about 150° C., preferably at a temperature in the range of from about 60° C. to about 100° C., and more preferably at a temperature in the range of from about 70° C. to about 95° C.; at a pressure in the range of from about 25 psig to about 650 psig, preferably at a pressure in the range of from about 100 psig to about 550 psig, and more preferably at a pressure in the range of from about 150 psig to about 300 psig; and at a liquid hourly space velocity of about 0.1 hr.⁻¹ to about 3 hr.⁻¹, preferably at a liquid hourly space velocity of about 0.2 hr.⁻¹ to about 2 hr.⁻¹, and more preferably at a liquid hourly space velocity of about 0.25 hr.⁻¹ to about 1 hr.⁻¹.

The light paraffins of the product stream preferably contain isobutane, and more preferably contain isobutane, isopentane, and hexane isomers (such as 2,2 dimethylbutane, 2-methylpentane and 3-methylpentane).

Preferably at least about 10%, more preferably at least about 15%, and more preferably at least about 20% by weight of the C₇+ paraffins of the hydrocarbon feed stream are converted to the light paraffins of the product stream.

The light paraffins of the product stream preferably contain at least about 40 weight %, and more preferably at least about 70 weight % isoparaffins having from three to six carbon atoms per molecule.

The following example is provided to further illustrate this invention and is not to be considered as unduly limiting the scope of this invention.

EXAMPLES

A 7.38 gram quantity of AlCl₃ was mixed with 2.71 grams of trimethylammonium chloride (N(CH₃)₃:HCl) (at approximately 2 equivalents AlCl₃ and 1 equivalent (N(CH₃)₃:HCl)) to form an ionic liquid. A 1.98 gram quantity of silica spheres, having a surface area greater than about 400 m²/g, a pore volume of 3.0 cc/g, and an average pore diameter of 308 Å, were added to the ionic liquid along with 17.01 grams of the inert support Alundum alumina to form a mixture. The mixture was then charged to a reactor.

A n-heptane feed was charged to the reactor at 90° C., 300 psig and varying liquid hourly space velocities. Results of such are presented in the Table below.

	TABLE
	TOS, Hrs.
	Feed	1	2	3	4
LHSV, hr−1		~0.5	~0.5	~0.5	~0.5
Component (wt. %)
C3	0.00	0.46	0.02	0.44	0.36
iC4	0.00	6.40	6.01	4.22	3.13
n-C4	0.00	1.37	1.11	0.74	0.51
i-C5	0.00	7.26	5.68	4.10	3.04
2-MB-1	0.00	1.08	0.79	0.53	0.36
n-C5	0.00	0.57	0.40	0.26	0.16
2,2-DMC4	0.00	3.72	2.86	2.10	1.57
2-MC5	0.00	1.46	1.12	0.83	0.62
3-MC5	0.00	2.20	2.29	2.22	1.95
n-C6	0.00	1.01	0.00	0.00	0.00
2-MC6	0.00	0.35	0.27	0.21	0.17
n-C7	99.52	65.91	71.65	78.95	83.87
Others	0.48	8.21	7.2	5.4	4.26
Total	100	100	100	100	100
n-C7 conversion %	—	33.8	28.0	20.7	15.7
Wt. % C4-C6	—	86.5	86.0	84.8	84.7
hydrocarbons in Product
on n-C7 free basis

As can be seen in the Table, the silica supported ionic liquid of this invention results in conversion of n-heptane to lower molecular weight paraffins and isoparaffins (including isobutane, isopentane, 2,2 dimethylbutane, 2-methylpentane and 3-methylpentane) at moderate conversion conditions.

While this invention has been described in detail for the purpose of illustration, it should not be construed as limited thereby but intended to cover all changes and modifications within the spirit and scope thereof.

Claims

1. A process comprising:

contacting a hydrocarbon feed stream comprising C7+ paraffins having at least seven carbon atoms per molecule with a composition comprising an ionic liquid supported on silica thereby producing a product stream comprising light paraffins having in the range of from four to six carbon atoms per molecule; wherein said ionic liquid has the formula: AB, wherein:

A is a cation capable of forming an ionic liquid, and

B is an anion containing aluminum and a halogen which is capable of forming an ionic liquid.

2. A process in accordance with claim 1 wherein:

A is (CH3)3NH+, and

B is an anion selected from the group consisting of Al2Cl7−, AlCl4−, Al3CL10−, and combinations thereof.

3. A process in accordance with claim 1 wherein said silica is non-crystalline.

4. A process in accordance with claim 1 wherein said ionic liquid is present in said composition in an amount in the range of from about 50 wt. % to about 90 wt. %.

5. A process in accordance with claim 1 wherein said ionic liquid is present in said composition in an amount in the range of from about 60 wt. % to about 90 wt. %.

6. A process in accordance with claim 1 wherein said ionic liquid is present in said composition in an amount in the range of from about 70 wt. % to about 85 wt. %.

7. A process in accordance with claim 1 wherein said silica is present in said composition in an amount in the range of from about 10 wt. % to about 50 wt. %.

8. A process in accordance with claim 1 wherein said silica is present in said composition in an amount in the range of from about 10 wt. % to about 40 wt. %.

9. A process in accordance with claim 1 wherein said silica is present in said composition in an amount in the range of from about 15 wt. % to about 30 wt. %.

10. A process in accordance with claim 1 wherein said C7+ paraffins are present in said hydrocarbon feed stream in an amount in excess of about 50 weight %.

11. A process in accordance with claim 1 wherein said C7+ paraffins are present in said hydrocarbon feed stream in an amount in excess of about 70 weight %.

12. A process in accordance with claim 1 wherein said C7+ paraffins are present in said hydrocarbon feed stream in an amount in excess of about 90 weight %.

13. A process in accordance with claim 1 wherein said hydrocarbon feed stream is contacted with said composition at a temperature in the range of from about 50° C. to about 100° C., a pressure in the range of from about 25 psig to about 650 psig, and at a liquid hourly space velocity of about 0.1 hr.−1 to about 3 hr.−1.

14. A process in accordance with claim 1 wherein said hydrocarbon feed stream is contacted with said composition at a temperature in the range of from about 60° C. to about 100° C., a pressure in the range of from about 100 psig to about 550 psig, and at a liquid hourly space velocity of about 0.2 hr.−1 to about 2 hr.−1.

15. A process in accordance with claim 1 wherein said hydrocarbon feed stream is contacted with said composition at a temperature in the range of from about 70° C. to about 95° C., a pressure in the range of from about 150 psig to about 300 psig, and at a liquid hourly space velocity of about 0.25 hr.−1 to about 1 hr.−1.

16. A process in accordance with claim 1 wherein said light paraffins of said product stream contain isobutane.

17. A process in accordance with claim 1 wherein said light paraffins of said product stream contain isobutane, isopentane, and hexane isomers.

18. A process in accordance with claim 1 wherein at least about 10% by weight of said C7+ paraffins are converted to said light paraffins.

19. A process in accordance with claim 1 wherein at least about 15% by weight of said C7+ paraffins are converted to said light paraffins.

20. A process in accordance with claim 1 wherein at least about 20% by weight of said C7+ paraffins are converted to said light paraffins.

21. A process in accordance with claim 1 wherein said light paraffins of said product stream contain at least about 40 weight % isoparaffins having from three to six carbon atoms per molecule.

22. A process in accordance with claim 1 wherein said light paraffins of said product stream contain at least about 70 weight % isoparaffins having from three to six carbon atoms per molecule.