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 the general formulae I C.sub.nH.sub.2n+1R.sup.1 with n≧3 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 mixture of at least one inert gas and at least one reactive gas selected from the group of alkanes of the general formulae II C.sub.mH.sub.2m+2 with .sub.m≧2, or alkenes of the general formulae III C.sub.mH.sub.2m with .sub.m≧2, wherein the alkane to be dehydrogenated of the general formulae I in the at least one first stream comprises at least one more carbon atom than the alkane of the general formulae II and alkene of the general formulae III in the at least one second stream.

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

3. The process according to claim 1, wherein the alkane of general formulae I comprises propane, butane, iso-butane, tert-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 general formulae II and/or the alkene of the general formulae III m=2-19.

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

7. The process according to claim 1, wherein the molar ratio of the at least one inert gas and the at least one alkane of general formulae II and/or alkene of general formulae III in the second stream is between 99.9:0.1 and 0.1:99.9.

8. The process according to claim 1, wherein the at least alkane of general formulae II and the at least one alkene of general formulae III used in the mixture of the second stream have a varying molar ratio to each other.

9. The process according to claim 1, wherein a mixture comprising methane, ethane and ethene is used.

10. The process according to claim 1, comprising a total dehydrogenation time, wherein the at least one first stream comprising the at least one alkane of the general formulae I is fed into the at least one reactor for a total alkane feeding time tS.sub.1 and the at least one second stream comprising the mixture of at least one inert gas and the at least one alkane of the general formulae II and/or the at least one alkene of the general formulae III is fed into the at least one reactor for a total feeding time tS.sub.2, wherein the ratio z of total feeding time tS.sub.2 and total feeding time tS.sub.1 is between 0.001 and 1.

11. The process according to claim 1, wherein the first stream is fed to the at least one reactor of the reactor system as front feed and the second stream is fed to the at least one reactor of the reactor system at 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 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 the temperature of the feed of the at least one first stream and of the feed of the at least one second stream are between 400 and 650° C. respectively, and that reaction temperatures in the catalyst bed are between 500 and 1000° C.

15. The process according to claim 1, wherein the at least one inorganic catalyst material of the catalyst bed comprises chromium oxide, platinum, iron, vanadium or a mixture thereof and the at least one first inert material of the 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 5, wherein m=2-7.

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

19. The process according to claim 9, wherein the mixture comprises 20 mol % methane, 50 mol % ethane, and 30 mol % ethene.

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

Description

[0073] The present invention is further explained in more detail based on the following examples in conjunction with the Figures. It shows:

[0074] FIG. 1 a first diagram showing the influence of a diluent according to prior art to the dehydrogenation process; and

[0075] FIG. 2 a second diagram showing the influence of a diluent according to an embodiment of the present invention.

[0076] 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.

[0077] The composition of methane-ethane-ethylene gas mixture is shown in table 1.

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

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 %

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 %

[0078] 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.