Endothermic gas phase catalytic dehydrogenation process

Abstract

An endothermic catalytic dehydrogenation process conducted in gas phase in system including a reactor with a catalyst bed including an inorganic catalytic material and a first inert material including the steps of: feeding a first stream having an alkane of the formulae I C.sub.nH.sub.2n+1R.sup.1 with n?3 and R.sup.1?H or aryl to be dehydrogenated into the reactor, and simultaneously or subsequently feeding a second stream including a mixture of an inert gas and a reactive gas selected from the group of alkanes of the formulae II C.sub.mH.sub.2m+2 with m?2, or alkenes of the formulae III C.sub.mH.sub.2m with .sub.m?2. The alkane to be dehydrogenated of formulae I in first stream has at least one more carbon atom than the alkane of formulae II and alkene of formulae III in the second stream.

Claims

1. An endothermic catalytic dehydrogenation process conducted in gas phase in at least one reactor system comprising at least one reactor with at least one catalyst bed comprising at least one inorganic catalytic material and at least one first inert material comprising the steps of: feeding at least one first stream comprising at least one alkane to be dehydrogenated of a general formula I C.sub.nH.sub.2n+1R.sup.1 with n=3-8 and R.sup.1=H or aryl into the at least one reactor, and simultaneously or subsequently feeding at least one second stream comprising a diluent gas mixture of (i) at least one inert gas, (ii) at least one reactive gas selected from the group of alkanes of a general formula II C.sub.mH.sub.2m+2 with m=2-7, and (iii) at least one reactive gas selected from the group of alkenes of a general formula III C.sub.mH.sub.2, with m=2-7, wherein the at least one alkane to be dehydrogenated of the general formula I in the at least one first stream comprises at least one more carbon atom than the alkane of the general formula II and the alkene of the general formula III in the at least one second stream, such that the alkane of general formula I in the first stream S1 and the alkane in the second stream S2 differ from each other, and wherein a molar ratio of the alkane in the at least one first stream S1 to a mixture of the at least one second stream S2 is between 50:1 and 1:1.

2. The process according to claim 1, wherein in the alkane of the general formula I, n=3-8 and R.sup.1=H or C.sub.6-C.sub.20 aryl.

3. The process according to claim 1, wherein the alkane of the general formula I comprises propane, butane, iso-butane, pentane, iso-pentane, hexane, ethyl benzene or mixtures thereof.

4. The process according to claim 1, wherein the at least one inert gas comprises methane, nitrogen, helium or argon.

5. The process according to claim 1, wherein in the alkane of the general formula II and/or the alkene of the general formula III, m=2-6.

6. The process according to claim 1, wherein the alkane of the general formula II comprises ethane, propane, butane, pentane, hexane or mixtures thereof and the alkene of the general formula III comprises ethene, propene, butene, pentene, hexene or mixtures thereof.

7. The process according to claim 1, wherein a molar ratio of the at least one inert gas to the at least one reactive gas selected from the group of alkanes of the general formula II and/or the at least one reactive gas selected from the group of alkenes of the general formula III in the at least one second stream is between 99.9:0.1 and 0.1:99.9.

8. The process according to claim 1, wherein the at least one alkane of the general formula II and the at least one alkene of the general formula III used in the mixture of the at least one second stream S2 have different moles.

9. The process according to claim 1, wherein the mixture of the at least one second stream S2 comprises methane, ethane and ethene.

10. The process according to claim 1, comprising a total dehydrogenation time, wherein the at least one first stream is fed into the at least one reactor for a total alkane feeding time tS.sub.1 and the at least one second stream is fed into the at least one reactor for a total feeding time tS.sub.2, wherein a ratio z of the total feeding time tS.sub.2 to the total alkane feeding time tS.sub.2 is between 0.001 and 1.

11. The process according to claim 1, wherein the at least one first stream is fed to the at least one reactor of the at least one reactor system as front feed and the at least one second stream is fed to the at least one reactor of the at least one reactor system at least one location alongside of the at least one reactor.

12. The process according to claim 1, wherein at least one layer of a second inert material is arranged upstream and/or downstream of the at least one catalyst bed in the at least one reactor.

13. The process according to claim 1, wherein the at least one reactor system comprises at least two reactors, which are connected in series and comprise at least one catalyst bed comprising at least one inorganic catalytic material and at least one first inert material, respectively.

14. The process according to claim 1, wherein a temperature of a feed of the at least one first stream and of a feed of the at least one second stream are between 400 and 650? C. respectively, and reaction temperature(s) in the at least one catalyst bed is/are between 500 and 1000? C.

15. The process according to claim 1, wherein the at least one inorganic catalytic material of the at least one catalyst bed comprises chromium oxide, platinum, iron, vanadium or a mixture thereof and the at least one first inert material of the at least one catalyst bed comprises magnesium oxide, aluminium oxide, aluminium nitride, titanium oxide, zirconium dioxide, niobium oxide or aluminium silicate.

16. The process according to claim 2, wherein n=3-8 and R.sup.1=H or C.sub.6-C.sub.10 aryl.

17. The process according to claim 7, wherein the molar ratio of the at least one inert gas to the at least one reactive gas selected from the group of alkanes of the general formula II and/or the at least one reactive gas selected from the group of alkenes of the general formula III in the at least one second stream is between 70:30 and 30:70.

18. The process according to claim 9, wherein the mixture of the at least one second stream S2 comprises 20 mol % methane, 50 mol % ethane, and 30 mol % ethene.

19. The process according to claim 10, wherein the ratio z of the total feeding time tS.sub.2 to the total alkane feeding time tS.sub.1 is between 0.05 and 0.1.

20. The process according to claim 1, wherein the molar ratio of the alkane in the at least one first stream S1 to the mixture of the at least one second stream S2 is between 45:1 and 3:1.

21. The process according to claim 1, wherein the molar ratio of the alkane in the at least one first stream S1 to the mixture of the at least one second stream S2 is between 30:1 and 15:1.

22. The process according to claim 7, wherein the molar ratio of the at least one inert gas to the alkane of the general formula II and the alkene of the general formula III in the at least one second stream is between 80:20 and 20:80.

23. The process according to claim 7, wherein the molar ratio of the at least one inert gas to the alkane of the general formula II and the alkene of the general formula III in the at least one second stream is between 70:30 and 30:70.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further explained in more detail based on the following examples in conjunction with the Figures. It shows:

(2) FIG. 1 a first diagram showing the influence of a diluent according to prior art to the dehydrogenation process; and

(3) FIG. 2 a second diagram showing the influence of a diluent according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) The following examples show the propylene yield improvement that can be made using methane as a diluent or methane-ethane-ethylene as a diluent. From FIGS. 1 and 2 one can see that using methane-ethane-ethylene gas mixtures as a diluent is more beneficial than using methane alone as a diluent in terms of propylene yield improvement. Increasing the methane-ethane-ethylene amount increases the yield improvement.

(5) The composition of methane-ethane-ethylene gas mixture is shown in table 1.

(6) TABLE-US-00001 TABLE 1 Composition of methane-ethane-ethylene gas mixture Component Mole % Methane 20 Ethane 50 Ethylene 30

(7) TABLE-US-00002 TABLE 2 Experimental conditions and yield improvement while using methane as diluent Base case Methane diluent C1/C3 ratio, mol/mol 0 0.23 0.47 0.72 Total pressure, bar 1.7 1.7 1.7 1.7 Temperature, ? C. 600 600 600 600 Yield improvement per 0.4 1.1 1.2 pass, mol %

(8) TABLE-US-00003 TABLE 3 Experimental conditions and yield improvement while using methane- ethane-ethylene gas mixture as diluent Methane-Ethane- Base case Ethylene diluent (C1 + C2)/C3 ratio, mol/mol 0 0.17 0.53 Total pressure, bar 1.7 1.7 1.7 Temperature, ? C. 600 600 600 Yield improvement per pass, 3.12 7.8 mol %

(9) 50 grams of catalyst was loaded in a fixed bed reactor. Reactor was heated externally by an electrical heating oven. The reactor effluents were analysed by a GC and online CO, CO.sub.2 and hydrogen sensors. Nitrogen was introduced with the reactant at constant rate. After the dehydrogenation step, reactor was flushed and regenerated by air.