HYDROGEN REJECTION IN METHANOL TO HYDROCARBON PROCESS

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 metal-containing zeolite based catalyst, 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 metal-containing zeolite based catalyst, 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, obtaining an at least partly H.sub.2 depleted recycle stream, recycling at least part of the at least partly H.sub.2 depleted recycle stream, the gaseous and/or liquid hydrocarbon streams 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 the 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 at least partially H.sub.2 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.

5. A process according to claim 1, wherein the at least partly H.sub.2 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.

6. 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.

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

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

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

10. A process according to claim 5, wherein the hydrogen scavenger is an aldehyde, wherein said aldehyde and hydrogen is converted into an alcohol over a hydrogenation catalyst.

11. A process according to claim 5, wherein the hydrogen scavenger is formaldehyde and wherein formaldehyde and hydrogen is converted into methanol over a hydrogenation catalyst.

12. A process according to claim 5, wherein the hydrogen scavenger is hydrogen peroxide and wherein hydrogen peroxide and hydrogen is converted into water over a hydrogenation catalyst.

12A. (canceled)

13. 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.

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

15. A process according to claim 1, wherein the zeolite based catalyst is a single bifunctional catalyst catalysing both methanol to hydrocarbons and dehydrogenation.

16. A process according to claim 1, wherein the zeolite based catalyst comprises a mixture of two or more catalysts which in combination catalyse both methanol to hydrocarbons and dehydrogenation reactions.

17. A process according to claim 1, wherein the zeolite based catalyst comprises a metal and/or metal oxide and a zeolite.

18. A process according to claim 1, wherein catalyst comprises a zeolite and a metal selected from the group consisting of Zn, Ga, In, Mo, Ag, P, Ge, Sn, Pd and Pt, preferably Zn.

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

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

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

22. A process according to claim 1, wherein the dehydrogenation catalyst is arranged as a top layer in the conversion reactor and/or in one or more separate dehydrogenation reactors.

23. A bifunctional catalyst for conversion of methanol, dimethyl ether, or mixtures hereof, to hydrocarbons, said catalyst comprising a metal and/or a metal oxide and ZSM-5.

24. A bifunctional catalyst for conversion of methanol to hydrocarbons comprising Zn and ZSM-5.

25. A plant for the conversion of methanol to hydrocarbons comprising aromatics, said plant comprising: means for supplying a feed stream comprising methanol, dimethyl ether or mixtures hereof a conversion reactor, a separator for separating a conversion effluent into a gaseous recycle stream, process condensate and a liquid product, and means for removing H.sub.2 from at least part of the effluent thereby obtaining at least one at least partially H2 depleted recycle stream.

26. A plant for the conversion of methanol to hydrocarbons according to claim 25, wherein the means for removing H.sub.2 from at least part of the effluent obtaining at least one at least partly H.sub.2 depleted recycle stream is a selective membrane, a selective oxidation step and/or a step wherein a hydrogen scavenger is converted into methanol or water in the presence of H.sub.2 and a hydrogenation catalyst.

27. A plant for the conversion of methanol to hydrocarbons according to claim 25, wherein the means for removing H.sub.2 from at least part of the effluent obtaining at least one at least partly H.sub.2 depleted recycle stream comprises means for separating the liquid hydro carbon stream into at least a product phase and one or more lower- and/or higher-boiling phases and means for recycling at least one of said lower- and/or higher-boiling phases as the at least partly H.sub.2 depleted recycle.

28. Product obtained by any of the plant, process or catalyst according to claim 1.

29. A process according to claim 5, wherein the hydrogen scavenger is carbon monoxide and/or carbon dioxide which are hydrogenated over a methanation catalyst.

Description

[0090] 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.

[0091] FIG. 1 shows a schematic setup of a first embodiment according to the present invention;

[0092] FIG. 2 shows a schematic setup of a second embodiment according to the present invention; and

[0093] FIG. 3 shows a schematic setup of third embodiment according to the present invention.

[0094] 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 (liquid hydrocarbon stream) 5 and a gas stream 6.

[0095] The first product stream is fed to a second separator 7 wherein the first product stream is separated into a second product stream (product phase) 8 and a LPG stream comprising C3-C4 wherefrom the recycle stream 9a is taken.

[0096] 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.

[0097] The second product stream 8 may be send to further processing, upgrade, storage etc.

[0098] The separation steps here illustrated by a single separator 7 may be carried in out in one or more separation steps in one or more separators. From the one or more separation steps may be separated one or more lower- and/or higher-boiling phases. For example in addition to the two steams 9 and 8 shown, may be obtained a light fraction comprising e.g. CH.sub.4, CO and/CO.sub.2 together with H.sub.2 if the first product stream 5 contains H.sub.2 (not shown).

[0099] 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.

[0100] The H.sub.2 depletion step 11 may comprise e.g. a H2 permeable membrane and/or a catalytic oxidation step.

[0101] 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.

[0102] In the embodiments of FIGS. 1, 2 and 3 the one or more H2 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.