Hydrogen rejection in methanol to hydrocarbon process with bifunctional catalyst

Abstract

The present application relates to a process for production of hydrocarbons comprising the steps of: converting a feed stream comprising alcohols, ethers or mixtures hereof over a Zn-containing zeolite based catalyst wherein Zn is at least partly present as ZnAl.sub.2O.sub.4, active in dehydrogenation of hydrocarbons, in a conversion step thereby obtaining a conversion effluent, separating said effluent to obtain an aqueous process condensate stream, a liquid hydrocarbon stream and a gaseous stream, removing part of the hydrogen formed in the conversion step, and recycling at least part of the gaseous and/or liquid hydrocarbon stream to the conversion step.

Claims

1. A process for production of hydrocarbons comprising the steps of converting a feed stream comprising alcohols, ethers or mixtures hereof over a bifunctional catalyst comprising zeolite, alumina binder and Zn, wherein the Zn is present at least partly as ZnAl.sub.2O.sub.4, in a conversion step thereby obtaining a conversion effluent including hydrogen, separating said effluent to obtain an aqueous process condensate stream, a liquid hydrocarbon stream and a gaseous stream, removing part of the hydrogen formed in the conversion step, and recycling at least part of the gaseous and/or liquid hydrocarbon stream to the conversion step, wherein: the at least partially H2 depleted recycle stream is obtained from the gaseous stream by passing said gaseous phase, after admixture with a predetermined amount of dioxygen, to a catalytic oxidation step, where hydrogen is reacted with said predetermined amount of oxygen to form water, and recycling said reacted stream, at least partly depleted in hydrogen, to the conversion step; and/or the at least partly H2 depleted recycle stream is obtained from the gaseous stream by passing said gaseous phase, after admixture with a predetermined amount of a non-dioxygen hydrogen scavenger, to a catalytic oxidation step, where hydrogen is reacted with said predetermined amount oxidizing agent, and recycling said reacted stream, at least partly depleted in hydrogen, to the conversion step.

2. A process according to claim 1 wherein hydrogen is removed by purging at least part of the gaseous recycle stream.

3. A process according to claim 1 wherein an at least partially H.sub.2 depleted recycle stream is obtained from the gaseous stream by passing the gaseous stream to a hydrogen permselective membrane.

4. A process according to claim 1, wherein the liquid hydrocarbon phase is separated into a product phase and one or more lower- and/or higher-boiling phases, at least one of which lower- and/or higher-boiling phases is at least partially recycled to the conversion step as the at least partly H.sub.2 depleted recycle.

5. A process according to claim 1, wherein at least part of the gaseous phase is recycled to the conversion step.

6. A process according to claim 1, wherein the conversion step takes place in two or more consecutive reactors with quench addition of feed and recycle streams.

7. A process according to claim 3 wherein the permeation of H.sub.2 in the selective membrane is adjusted to leave 1-10% of H.sub.2 in the retentate, recycled to the conversion step as the at least partially H.sub.2 depleted recycle stream.

8. A process according to claim 1, wherein the hydrogen scavenger is an aldehyde, wherein said aldehyde and hydrogen is converted into an alcohol over a hydrogenation catalyst.

9. A process according to claim 1, wherein the hydrogen scavenger is formaldehyde and wherein formaldehyde and hydrogen is converted into methanol over a hydrogenation catalyst.

10. A process according to claim 1, wherein the hydrogen scavenger is hydrogen peroxide and wherein hydrogen peroxide and hydrogen is converted into water over a hydrogenation catalyst.

11. A process according to claim 1, wherein the at least part of the recycle stream or recycle streams is returned to one or more points upstream the conversion step.

12. A process according to claim 1, comprising a step regulating the H.sub.2 content in the at least partly H.sub.2 depleted or partially depleted recycle stream.

13. A process according to claim 1, wherein the feed stream comprises methanol, dimethyl ether or mixtures hereof.

14. A process according to claim 1, wherein the process is carried out in one or more fixed bed reactors.

15. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein the zeolite is ZSM-5 or ZSM-11.

16. Process according to claim 1, wherein the catalyst is bifunctional catalyst comprising 30-80% zeolite, 5-40% ZnAl.sub.2O.sub.4, 0-40% Al.sub.2O.sub.3, 0-10% ZnO.

17. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein Zn is present in both zeolite and alumina binder.

18. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein the alumina binder further comprises silica.

19. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein the catalyst, by X-ray diffraction, does not contain free ZnO in the binder.

20. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein the Zn concentration is 3-25 wt %.

21. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein Zn is present in the binder as mainly ZnAl.sub.2O.sub.4.

22. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein Zn is present in the binder as at least 50% ZnAl.sub.2O.sub.4.

23. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein Zn is present in the binder as at least 95% ZnAl.sub.2O.sub.4.

24. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein Zn is present in the binder as up to 10% ZnO.

25. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein Zn in the zeolite is present as ZnO, Zn(OH)+ and/or Zn++ in ion exchange positions.

26. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein the total Zn content in the catalyst is 3-25 wt % Zn.

27. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein said catalyst is partly or fully spinelized.

28. Process according to claim 1, wherein the catalyst is bifunctional catalyst and wherein the Zn content is substantially the same in its partly spinelized and fully spinelized form.

29. Process according to claim 1, comprising a step of in situ obtaining a catalyst partially spinelized catalyst with a very high ZnAl.sub.2O.sub.4 content, fully spinelized catalyst or a substantially fully spinelized catalyst from a partially spinelized catalyst.

30. Product obtained by the process according to claim 1.

Description

(1) In the following the process and plant is further described with reference to the accompanying drawings. The drawings show exemplary embodiments of the present process and plant and are not to be construed as limiting to the scope of the present application.

(2) FIG. 1 shows a schematic setup of a first embodiment according to the present invention,

(3) FIG. 2 shows a schematic setup of a second embodiment according to the present invention, and

(4) FIG. 3 shows a schematic setup of third embodiment according to the present invention.

(5) FIG. 1 shows a schematic overview 1 of a plant/process according to the present application. A conversion effluent 2 is fed to a first separator 3 wherein the conversion effluent is separated into three streams: process condensate 4, first product stream 5 and a gas stream 6.

(6) The first product stream is fed to a second separator 7 wherein the first product stream is separated into a second product stream 8 and a LPG stream comprising C3-C4 wherefrom the recycle stream 9a is taken.

(7) As described herein the first product stream is near H.sub.2 free and H.sub.2 is present predominantly in the gas phase in the first separator. Thus when the first product stream is separated into the second product stream 8 and the recycle stream the recycle stream obtained is a H.sub.2 depleted recycle.

(8) The second product stream 8 may be send to further processing, upgrade, storage etc.

(9) FIG. 2 shows a schematic overview 10 of a plant/process according to the present application. A conversion effluent 2 is fed to a first separator 3 wherein the conversion effluent is separated into three streams: process condensate 4, first product stream 5 and a gas stream 6. At least part of the gas stream 6 is taken through a H.sub.2 depletion step 11 whereby a H.sub.2 depleted recycle stream 9b obtained.

(10) The H.sub.2 depletion step 11 may comprise e.g. a H.sub.2 permeable membrane and/or a catalytic oxidation step.

(11) FIG. 3 shows a schematic overview 12 of a plant/process wherein the embodiments of FIGS. 1 and 2 are combined whereby a H.sub.2 depleted stream is obtained from the gas stream 9b and from the LPG fraction taken from the second separator as H.sub.2 depleted stream 9a.

(12) In the embodiments of FIGS. 1, 2 and 3 the one or more H.sub.2 depleted streams are returned to the conversion step (not shown) from which the conversion effluent 2 is obtained. The conversion step may be a MTG or a MTA process.