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EP-4739751-A1 - PROCESS AND PLANT FOR ACID REMOVAL IN AN OXYGENATE-TO-HYDROCARBON SYSTEM

EP4739751A1EP 4739751 A1EP4739751 A1EP 4739751A1EP-4739751-A1

Abstract

Process and plant for producing hydrocarbons from an oxygenate feed stream, such as methanol, comprising acid removal of the converted-oxygenate product prior to down-stream fractionation. The plant comprises: an OTH section arranged to receive an oxygenate and provide a converted-oxygenate product comprising said hydrocarbons; an acid removal section arranged to receive said converted-oxygenate product and pro- vide an acid-washed converted-oxygenate product; a separation section arranged to receive said acid-washed converted-oxygenate product and provide at least one of: an intermediate gasoline product, an intermediate naphtha product, an intermediate jet fuel product, an intermediate diesel product.

Inventors

  • SØRENSEN, Martin Dan Palis

Assignees

  • Topsoe A/S

Dates

Publication Date
20260513
Application Date
20240614

Claims (11)

  1. 1. Process (10) for the conversion of oxygenates to hydrocarbons, comprising the steps of: - supplying a feed stream of one or more oxygenates (1) to an oxygenate-to-hydrocar- bons section (OTH-section) and providing therefrom a converted-oxygenate product (11) comprising said hydrocarbons, said OTH-section comprising: an oxygenate conversion reactor (12) in the presence of a conversion catalyst (12’) comprising a zeolite, and a separation unit (14); - converting in said oxygenate conversion reactor (12) the feed stream of one or more oxygenates (1) to a raw converted-oxygenate product (7); - separating in said separation unit (14) the raw converted-oxygenate product (7) into at least: a process condensate (9) comprising water and oxygenates; and said converted oxygenate product (11); the process further comprising: - supplying said converted oxygenate product (11) to an acid removal step and providing an acid-washed converted-oxygenate product (23); - supplying said acid-washed converted-oxygenate product (23) to a separation section (22) for separating from said acid-washed converted-oxygenate product (23) at least one of: an intermediate gasoline product (27), an intermediate naphtha product (25, 25’, 25”), an intermediate jet fuel product (29), an intermediate diesel product (31), optionally an off-gas stream (33) such as an off-gas stream comprising C1-C4 hydrocarbons; wherein said acid removal step comprises: - combining said converted oxygenate product (11) with a wash water recycle (21 , 2T) comprising an alkaline agent (19) into a combined stream (13); in which a first wash water recycle (17) is withdrawn from a downstream filtration unit (18) and combined with said alkaline agent (19) into said wash water recycle (21 , 21”); - supplying said combined stream (13) to a mixing unit (16) and subsequently to said filtration unit (18); - withdrawing from said filtration unit (18) said wash water recycle (17) and said acid-washed converted-oxygenate product (23); the process further comprising: - diverting a portion of said wash water recycle (17, 21) as a bleed stream (21”) and combining said bleed stream (21”) with said process condensate (9) comprising water and oxygenates into a combined process condensate stream (9’).
  2. 2. Process according to claim 1 , further comprising: supplying the combined process condensate stream (9’) to a process condensate stripping unit (PC-stripper) and withdrawing therefrom: an overhead gas stream free of alkaline agent and comprising unconverted oxygenates, such as unconverted methanol and/or DME; and a bottom stream comprising said alkaline agent.
  3. 3. Process according to claim 2, further comprising: supplying said overhead gas stream free of alkaline agent and comprising unconverted oxygenates, such as unconverted methanol and/or DME, to said oxygenate conversion reactor (12).
  4. 4. Process according to any of claims 1-3, wherein said step of diverting a portion of said wash water recycle (17, 21) as a bleed stream (21”), is conducted prior to said step of combining the alkaline agent (19) with said wash water recycle (17).
  5. 5. Process according to any of claims 1-4, wherein said separation unit (14) further provides an overhead recycle stream (3, 3’), and the process further comprises recycling said overhead recycle stream (3, 3’) to said oxygenate conversion reactor (12), for instance by admixing with said feed stream of one or more oxygenates (1) into a combined feed stream (5).
  6. 6. Process according to any of claims 1-5, wherein said alkaline agent is a caustic agent, such as any of NaHCCh or Na2COs.
  7. 7. Process according to claim 6, wherein said downstream filtration unit (18) is a coalescer, said mixing unit (16) is a static mixer, said alkaline agent (19) is said caustic agent, such as any of NaHCCh or Na2COs; and wherein said acid removal step further comprises combining the alkaline agent (19) with said wash water recycle (17) by said alkaline agent (19) being provided by a dosing unit (20), e.g. a caustic dosing unit.
  8. 8. Process according to any of claims 1-7, wherein said acid-washed converted-oxy- genate product (23) comprises less than 1 ppmw acids, such as less than 0.6 ppmw acids, such as below 0.01 ppmw; said acids being at least one: of formic acid, acetic acid, propanoic acid, or combinations thereof.
  9. 9. Process according to any of claims 1-8, wherein said acid-washed converted-oxy- genate product (23) comprises C5+ hydrocarbons of which at least 30 wt%, such as at least 40 wt%, or at least 50 wt%, are hydrocarbons boiling in the gasoline boiling range and/or hydrocarbons boiling in the jet fuel boiling range.
  10. 10. Process according to any of claims 1-9, wherein: - said OTH-section is a methanol-to-gasoline loop section (MTG-loop section) in which said zeolite is: a zeolite with a framework having a 10-ring pore structure, said 10-ring pore structure being a three-dimensional (3D) pore structure, such as ZSM-5; or - said OTH-section is a methanol-to-olefins loop section (MTO-loop section) in which said zeolite is: a zeolite with a framework having a 10-ring pore structure, said 10-ring pore structure being a unidimensional (1 D) pore structure, such as ZSM-48.
  11. 11. A plant (10) for carrying out the process according to any of claims 1-10; the plant comprising: - an OTH section comprising: an oxygenate conversion reactor (12) and a separation unit (14); said OTH section being arranged to receive a a feed stream of one or more oxygenates (1) and provide a converted-oxygenate product (11); said OTH-section comprising: an oxygenate conversion reactor (12) in the presence of a conversion catalyst (12’) comprising a zeolite, and a separation unit (14), said oxygenate conversion reactor (12) being arranged to receive the feed stream of one or more oxygenates (1) and provide a raw converted-oxygenate product (7); said separation unit (14) being arranged to receive the raw converted-oxygenate product (7) and provide at least: a process condensate (9) comprising water and oxygenates; and said converted oxygenate product (11); - an acid removal section comprising: a filtration unit (18), a mixing unit (16) upstream said filtration unit (18), optionally a dosing unit (20); said acid removal section being arranged to receive said converted-oxygenate product (11) and provide an acid- washed converted-oxygenate product (23); - a separation section (22), such as a fractionation section, arranged to receive said acid-washed converted-oxygenate product (23) and provide at least one of: an intermediate gasoline product (27), an intermediate naphtha product (25, 25’, 25”), an intermediate jet fuel product (29), an intermediate diesel product (31), optionally an off-gas stream (33) such as an off-gas stream comprising C1-C4 hydrocarbons; wherein said acid removal section further comprises: - a mixing point, such as a juncture, for combining said converted oxygenate product (11) with a wash water recycle (21 , 2T) comprising an alkaline agent (19) into a combined stream (13); a conduit for withdrawing a first wash water recycle (17) from said filtration unit (18) and a mixing point, such as juncture, for combining said first wash water recycle (17) with said alkaline agent (19) into said wash water recycle (21 , 21”); - a conduit for supplying said combined stream (13) to said mixing unit (16) and subsequently to said filtration unit (18); - withdrawing from said filtration unit (18) said wash water recycle (17) and said acid- washed converted-oxygenate product (23); the plant (10) further comprising: - a conduit for diverting a portion of said wash water recycle (17, 21) as a bleed stream (21”), and a mixing point, such as a juncture, for combining said bleed stream (21”) with said process condensate (9) comprising water and oxygenates into a combined process condensate stream (9’).

Description

Title: Process and plant for acid removal in an oxygenate-to-hydrocarbon system The present invention relates to the removal of acids from streams comprising hydrocarbon products produced by the conversion of oxygenates, for instance methanol to hydrocarbons in the transportation fuel range, such as gasoline, jet fuel, optionally also diesel. In conventional oxygenate-to-hydrocarbon (OTH) processes/plants, such as methanol- to-hydrocarbon (MTH), for instance in a methanol-to-gasoline (MTG) process or a methanol-to-olefins (MTO) process in connection with the production of jet fuel (MTJ), catalysts comprising acidic zeolites are typically used. The oxygenate is typically methanol and/or dimethyl ether (DME). For instance, in a conventional methanol-to-gasoline (MTG) process, methanol is converted in a MTG reactor under the presence of a catalyst comprising an acidic zeolite, for instance a zeolite with a framework having a 10-ring pore structure, in which the 10- ring pore structure is a three-dimensional (3D) pore structure, such as ZSM-5. From the MTG reactor a raw converted oxygenate product comprising hydrocarbons boiling in the gasoline boiling range, is withdrawn as a raw converted-oxygenate product, i.e. a first raw gasoline product, and then supplied to a three-phase separation unit. From this separation unit, a process condensate containing water and oxygenates is separated, as so is an overhead stream which may be used as a recycle stream, and a converted-oxygenate product, i.e. a raw gasoline product. The oxygenates in the process condensate include unconverted oxygenate, e.g. unconverted methanol, as well as acids such as formic acid and acetic acid. The recycle stream from the separation unit is suitably directed via a recycle compressor to said MTG reactor, thus in a MTG-loop. The raw gasoline product may then be supplied to a downstream separation section, such as fractionation section, for removing C2-C4 compounds, typically in a so-called de-ethanizer and de-butanizer (LPG-splitter), thereby producing a stabilized gasoline product as an intermediate gasoline product. The stabilized gasoline product may be further upgraded by hydroisomerization (HDI) and/or hydrocracking (HCR) to provide a final gasoline product. For instance, in a methanol-to-jet fuel (MJT) process, methanol is converted in a MTO reactor under the presence of a catalyst comprising an acidic zeolite, for instance a zeolite with a framework having a 10-ring pore structure, in which the 10-ring pore structure is a one-dimensional (1 D) pore structure, such as ZSM-48. From the MTO reactor a raw converted oxygenate product comprising hydrocarbons boiling in the jet fuel range is withdrawn and then supplied to a three-phase separation unit. From this separation unit, a process condensate containing water and oxygenates is separated, as so is an overhead stream which may be used as a recycle stream, and a converted-oxy- genate product. The recycle stream is suitably directed via a recycle compressor to said MTO reactor, thus in a MTO-loop. The converted-oxygenate product comprising hydrocarbons boiling in the jet fuel range is typically supplied in a sequential manner to an oligomerization section for producing more hydrocarbons in the jet fuel range, and then to a downstream separation section, such as fractionation section, for separating therefrom an intermediate naphtha product, an intermediate jet fuel product, optionally, an intermediate diesel product. The intermediate jet fuel may further be hydroprocessed, for instance by hydrogenation thereby saturating the olefins into a final jet fuel product. It has been common general knowledge so far that oxygenates such as unconverted methanol and undesired oxygenates such as organic acids, for instance said formic acid or acetic acid, are removed as part of the process condensate stream withdrawn from the three-phase separator. This process condensate is typically sent to a stripper (PC-stripper) for recovering methanol as oxygenate while the remaining oxygenates in the process condensate are sent to a waste-water treatment plant. While the process condensate contains such acids in ppm range, it has now been found that the acids also transfer to the hydrocarbon phase of the tree-phase separator, thereby making the thus withdrawn converted-oxygenate product highly corrosive when exposed to free water. Surprisingly, even if the water separation in the three- phase separator is conducted effectively, there are still undesired oxygenates, particularly organic acids, present in the hydrocarbon phase. Consequently, the thus corrosive converted oxygenate product requires the use of expensive stainless steel in downstream units. US 20200239785 A1 discloses a process and system for removing organic acids from liquid hydrocarbon product streams, which include injecting an ammoniated water wash into a liquid hydrocarbon product stream, such as an effluent stream from a methanol conversion