Process and plant for acid removal in an oxygenate-to-hydrocarbon system

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.

Description

[0001] Title: Process and plant for acid removal in an oxygenate-to-hydrocarbon system

[0002] 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.

[0003] 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).

[0004] 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the MTG reactor a raw converted oxygenate product comprising hydrocarbons boiling in the gasoline boiling range, is withdrawn as a raw converted-oxygenate product, i.e. a first raw gasoline product, and then supplied to a three-phase separation unit.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.

[0005] 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.

[0006] 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 process, and subsequently separating the treated liquid hydrocarbon product stream from the wash water. The addition of ammonia reduces the amount of water wash by an unexpected amount. This citation is at least silent on diverting a wash water recycle as a bleed stream and combining this bleed stream with process condensate comprising water and oxygenates from an upstream separation unit, into a combined process condensate stream.

[0007] Accordingly, in a first aspect of the invention, there is provided a process for the conversion of oxygenates to hydrocarbons, comprising the steps of:

[0008] - supplying a feed stream of one or more oxygenates to an oxygenate-to-hydrocarbons section (OTH-section) and providing therefrom a converted-oxygenate product comprising said hydrocarbons, said OTH-section comprising: an oxygenate conversion reactor in the presence of a conversion catalyst comprising a zeolite, and a separation unit;

[0009] - converting in said oxygenate conversion reactor the feed stream of one or more oxygenates to a raw converted-oxygenate product;

[0010] - separating in said separation unit the raw converted-oxygenate product into at least: a process condensate comprising water and oxygenates; and said converted oxygenate product; the process further comprising:

[0011] - supplying said converted oxygenate product to an acid removal step and providing an acid-washed converted-oxygenate product;

[0012] - supplying said acid-washed converted-oxygenate product to a separation section for separating from said acid-washed converted-oxygenate product at least one of: an intermediate gasoline product, an intermediate naphtha product, an intermediate jet fuel product, an intermediate diesel product, optionally an off-gas stream (33) such as an off-gas stream comprising C1-C4 hydrocarbons, e.g. LPG; wherein said acid removal step comprises:

[0013] - combining said converted oxygenate product with a wash water recycle comprising an alkaline agent into a combined stream; in which a first wash water recycle is withdrawn from a downstream filtration unit and combined with said alkaline agent into said wash water recycle;

[0014] - supplying said combined stream to a mixing unit and subsequently to said filtration unit;

[0015] - withdrawing from said filtration unit said wash water recycle and said acid- washed converted-oxygenate product; the process further comprising:

[0016] - diverting a portion of said wash water recycle as a bleed stream and combining said bleed stream with said process condensate comprising water and oxygenates into a combined process condensate stream.

[0017] The removal of the acids in the converted oxygenate product from the separation unit enables the provision of downstream units, such as said separation section, made of carbon steel rather than stainless steel, thereby significantly reducing capital and operation expenditure (CAPEX, OPEX).

[0018] In an embodiment, the oxygenate is methanol (MeOH) and / or dimethyl ether (DME).

[0019] The invention enables that a single process condensate stripper (PC-stripper) be utilized for separating unconverted oxygenates, in particular MeOH and / or DME, which may then be introduced to said oxygenate conversion reactor of the OTH-section, for instance a methanol to gasoline (MTG) reactor or a methanol to olefins (MTO) reactor, or more generally a methanol-to-hydrocarbons (MTH) reactor, without risking the carrying over of ammonia compounds thereto. There is no need to provide a separate, i.e. a dedicated, PC-stripper to treat any wash water comprising ammonia. The MTH reactor comprises an acidic zeolite as the catalyst, which reacts reversibly with ammonia thereby deactivating the catalyst. A lower catalyst cycle time results and thereby also more frequent regenerations are required to remove the ammonia from the catalyst. Catalyst longevity is thereby also reduced.

[0020] In an embodiment, the process further comprises supplying the combined process condensate stream 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.

[0021] It is understood that the term “free of alkaline agent” means that the alkaline agent is undetectable, or present in a concentration or amount which does not deactivate the conversion catalyst of the oxygenate conversion reactor.

[0022] It is understood that the PC-stripper is a common PC-stripper, as it treats the combined process condensate stream; see e.g. stream 9’ in appended figure.

[0023] As is well-known in the art, a PC-stripper (PC-stripping unit) is a unit for removing impurities from a process condensate. The impurities include unconverted oxygenates such as methanol and / or DME and acid compounds, for instance said formic acid or acetic acid. In the PC-stripper, heat is provided and optionally pressure to respectively heat and pressurize the process condensate; preferably, however, the PC-stripper operates a lower pressure than the synthesis. Thereby, the impurities are vaporized and then separated in an overhead gas stream from the rest of the process condensate, the latter being withdrawn in a bottom stream. This process condensate is then sent to a wastewater treatment plant.

[0024] It is understood that the acids, i.e. the organic acids, are also withdrawn with the bottom stream from the PC-stripper.

[0025] In an embodiment, the process further comprises: 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.

[0026] By the invention, the e.g. sodium-ions (Na-ions) of the alkaline agent present in the combined process condensate stream, condense in the common PC-stripper and are withdrawn with a bottom stream of the PC-stripper. Hence, contrary to ammonia compounds, the e.g. Na-ions are not carried over with the unconverted oxygenate, e.g. unconverted methanol withdrawn in the overhead gas of the PC-stripper, and which is reutilized as oxygenate feed in the oxygenate conversion reactor of the OTH-section. If these ions are carried over together with the unconverted oxygenate, the ions will deactivate the MTG catalyst, thereby reducing catalyst cycle time.

[0027] When ammonia is present in the combined process condensate and sent to the PC- stripper, some ammonia will be withdrawn with the bottom stream of the PC-stripper and some ammonia will be carried over together with the unconverted oxygenate, e.g. unconverted methanol, as part of the PC-stripper overhead gas being withdrawn therefrom, and thereby deactivate the catalyst of the MTH reactor. Further ammonia removal becomes also necessary before sending the unconverted oxygenate back to the MTH reactor, thereby incurring a high penalty in terms of capital and operating expenditures. Furthermore, ammonia as alkaline agent in the acid removal step or correspondingly, acid removal system, is more difficult to handle and entails substantial safety measures, as ammonia is highly volatile.

[0028] The Na-ions which condense in the common PC-stripper are withdrawn in the bottom stream which is directed to a wastewater treatment plant (WWTP). The sodium ions contribute to the conductivity of the wastewater, thereby enhancing certain treatment processes in the WWTP, such as electrocoagulation, by which suspended particles from water, can be more effective removed with higher conductivity.

[0029] In an embodiment, said step of diverting a portion of said wash water recycle as a bleed stream, is conducted prior to said step of combining the alkaline agent with said wash water recycle.

[0030] For the purposes of the present application, the term “first aspect of the invention” means the process of the invention. The term “second aspect of the invention” means a plant (system) i.e. process plant.

[0031] The term “Process for the conversion of oxygenates to hydrocarbons” may be used interchangeably with the term “OTH-process”. The term “OTH-section” means a physical section comprising one or more units, such as a reactor and separation unit, and associated process steps. It would be understood that the OTH-section is a physical section of a OTH-process / plant. An OTH-process / plant comprises a OTH-section. For instance, a MTG-process / plant comprises a MTG-section.

[0032] The term “process / plant” means process and / or plant. The term “and / or” means in connection with a given embodiment any of three options; hence, the term “and / or” may be used interchangeably with the term “at least one of” the three options.

[0033] The term “comprising” includes “comprising only” i.e. “consisting of”.

[0034] The term “suitably” is used interchangeably with the term “optional” i.e. an optional embodiment.

[0035] The term “present invention” or simply “invention” may be used interchangeably with the term “present application” or simply “application”.

[0036] The term “LPG”, liquified petroleum gas, as is well known in the art means a C3-C4 hydrocarbon fraction.

[0037] Other definitions are provided in connection with one or more of below embodiments.

[0038] In an embodiment, said separation unit further provides an overhead recycle stream, and the process further comprises recycling said overhead recycle stream to said oxygenate conversion reactor, for instance by admixing with said feed stream of one or more oxygenates into a combined feed stream.

[0039] Thereby, the OTH-section, for instance a MTG-section, operates as a MTG-loop section. A dedicated recycle compressor supplies the overhead recycle stream to the oxygenate-conversion reactor, here a MTG-reactor, for controlling the exothermicity of the MTG reaction therein. In another embodiment, the OTH-section, for instance a MTO- section, operates as a MTO-loop section. A dedicated recycle compressor supplies the overhead recycle stream to the oxygenate-conversion reactor, here a MTO-reactor, for controlling the exothermicity of the MTO reaction therein.

[0040] According to the invention, said acid removal step comprises:

[0041] - combining said converted oxygenate product with a wash water recycle comprising an alkaline agent into a combined stream; in which a first wash water recycle is withdrawn from a downstream filtration unit and combined with said alkaline agent into said wash water recycle;

[0042] - supplying said combined stream to a mixing unit and subsequently to said filtration unit;

[0043] - withdrawing from said filtration unit said wash water recycle and said acid-washed converted-oxygenate product. Thereby it is also possible to remove the acids by a simple water wash, despite the acids being present in the converted oxygenate product at a ppmw level.

[0044] In an embodiment, said alkaline agent is a caustic agent.

[0045] In an embodiment, the caustic agent is any of NaHCCh or Na2COs.

[0046] The term “caustic agent” means derived from a strong base selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), or combinations thereof.

[0047] The term “caustic agent” does not comprise ammonia or ammonia compounds. Ammonia itself is regarded as a weak base.

[0048] In an embodiment, said downstream filtration unit is a coalescer, said mixing unit is a static mixer i.e. a liquid / liquid static mixer, said alkaline agent is said caustic agent, such as any of NaHCCh or Na2COs; and wherein said acid removal step further comprises combining the alkaline agent with said wash water recycle by said alkaline agent being provided by a dosing unit, e.g. a caustic dosing unit.

[0049] Simple water wash using an alkaline agent, e.g. via caustic dosing, is thereby provided. The wash water is mixed with the converted oxygenate product after separation of the water phase which is mainly removed in the process condensate in the separation unit, suitably a three-phase separator. For instance, there is provided a 10 wt% wash water recycle with alkaline dosing. The mixture is sent to the static mixer, i.e. a system of one or more static mixers, to ensure good contact between the acids and the alkaline agent. The mixture is then sent to the coalescer to effectively separate out the wash water. The then washed hydrocarbon product is sent to downstream separation section, e.g. fractionation section comprising one or more fractionation units, now as an acid-washed converted-oxygenate product.

[0050] According to the invention, the process further comprises: diverting a portion of said wash water as a bleed stream, optionally prior to said step of combining the alkaline agent with said wash water recycle, and combining said bleed stream with said process condensate comprising water and oxygenates into a combined process condensate stream; optionally, supplying the combined process condensate stream to a process condensate stripping unit (PC-stripper).

[0051] The wash water is recycled to the mix point, while said portion as a small bleed corresponding to the alkaline dosing is sent to the process condensate stripper.

[0052] In an embodiment, said acid-washed converted-oxygenate product 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.

[0053] The residual acid in the acid-washed converted-oxygenate product has been found to be below 1 ppmw and even below the detection limit of 0.6 ppmw; further, by the invention is possible to achieve significantly lower values, such as below 0.01 ppmw.

[0054] In an embodiment, said acid-washed converted-oxygenate product 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.

[0055] The invention is thus at least suitably for MTG plants and MTJ process / plants, thus enabling the use of carbon steel or other less expensive materials than stainless steel in downstream units, such as in said separation section, which may comprise one or more fractionation units e.g. distillation units. These units are highly expensive both in terms of CAPEX and OPEX.

[0056] The term “hydrocarbons boiling in the gasoline boiling range” means C5-C12 hydrocarbons boiling in the range 30-210°C.

[0057] The term “hydrocarbons boiling in the jet fuel range” may be used interchangeably with the term “jet fuel hydrocarbons” or “jet fuel range hydrocarbons”, or respectively, “jet fuel” or “jet fuel range”. The term means C8-C19 hydrocarbons, such as C8-C17 or C8- C16 hydrocarbons, boiling in the range 130-300°C. For instance, the jet fuel is sustainable aviation fuel (SAF) in compliance with ASTM D7566 and ASTM D4054. The term boiling in a given range, shall be understood as a hydrocarbon mixture of which at least 80 wt% boils in the stated range.

[0058] The intermediate naphtha product comprises C5-C9 hydrocarbons boiling in the range 30-160°C, such C5-C8 hydrocarbons, e.g. C5-C8 olefins.

[0059] The intermediate diesel product comprises hydrocarbons boiling in the diesel boiling range means C8-C25 hydrocarbons boiling in the range 120-360°C, for instance 160- 360°C.

[0060] For gasoline production (e.g. MTG process / plants), the acid-washed converted oxygenate product is sent as a raw gasoline stream to the downstream separation section comprising a de-ethanizer and de-butanizer (LPG-splitter), thereby producing a stabilized gasoline stream as said intermediate gasoline product. Suitably, as is well-known in the art, the de-ethanizer and LPG-splitter are fractionation units, e.g. distillation units. The stabilized gasoline may be upgraded by subjecting it hydroisomerization (HDI) in a HDI reactor and / or hydrocracking (HCR) in a HCR reactor, for providing a final gasoline product.

[0061] For jet fuel production (e.g. MTJ process / plant), the acid-washed converted oxygenate product is sent to the downstream separation section. The downstream separation section comprising one or more fractionation units, thereby providing the intermediate naphtha product, intermediate jet fuel product, optionally also an intermediate diesel product. The intermediate jet fuel product is suitably sent to hydroprocessing, preferably hydrogenation (HYDRO) in a HYDRO reactor for saturating the olefins in the jet fuel into the corresponding paraffins, thereby providing a final jet fuel product.

[0062] In either MTG or MTJ an off-gas stream is also withdrawn. The off-gas stream means one more off-gas streams. An off-gas stream comprises for instance CO, CO2 and H2. An off-gas stream comprises for instance C1-C4 hydrocarbons, such as LPG. Combinations thereof are also envisaged.

[0063] It would be understood that the OTH-section can be provided as a once-through OTH- section or as an OTH-loop section.

[0064] It would be understood that, in an embodiment, the OTH-section can be a MTH-sec- tion. It would be understood that, in an embodiment, the MTH-section can be a MTH-loop section.

[0065] It would be understood that the term MTH comprises any of MTG or MTO or MTJ.

[0066] It would be understood that the MTJ comprises MTO optionally also oligomerization (OLI).

[0067] It would be understood that MTH means methanol-to-hydrocarbons; MTG means meth- anol-to-gasoline; MTO means methanol-to-olefins; MTJ means methanol-to-jet fuel.

[0068] While the OTH-section, such as MTG-section or MTO-section may be provided in a once-through mode (no recycle of overhead stream from separation unit, thus no recycle compressor), it is advantageous to provide either as a loop, thus with recycle of overhead stream from separation unit, thus with a recycle compressor.

[0069] Accordingly, in an embodiment,

[0070] - 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 1O-ring pore structure, said 1O-ring pore structure being a three-dimensional (3D) pore structure, such as ZSM-5; or

[0071] - 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 1O-ring pore structure, said 1O-ring pore structure being a unidimensional (1D) pore structure, such as ZSM-48.

[0072] For instance, the MTG-reactor of a MTG-loop section is provided as an adiabatic fixed bed rector with a catalyst comprising the 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. The overhead recycle enables control of the exothermicity of the MTG- reactor.

[0073] For instance, the MTO-reactor of a MTO-loop section is provided as an adiabatic fixed bed rector with a catalyst comprising the zeolite with a framework having a 10-ring pore structure, said 10-ring pore structure being a unidimensional (1D) pore structure, such as ZSM-48. The overhead recycle enables control of the exothermicity of the MTO-reactor. In an embodiment, subsequent to the said separation section, e.g. fractionation section, a downstream hydroprocessing is conducted in a hydroprocessing section or unit in the presence of a hydroprocessing catalyst. For instance, hydroisomerization (HDI) in a HDI reactor in the presence of a HDI catalyst and / or hydrocracking (HCR) in the presence of a HCR catalyst in a HCR reactor, may be provided for upgrading the intermediate gasoline product into a final gasoline product. For instance, hydrogenation (HYDRO) in a HYDRO reactor in the presence of a HYDRO catalyst is provided for hydrogenating the intermediate jet fuel product into a final jet fuel product.

[0074] Suitable conditions and catalysts for hydroprocessing, e.g. HDI, HCR, as well as for HYDRO are well-known in the art.

[0075] In a second aspect of the invention, there is also provided a plant for carrying out the process according to any of the above embodiments.

[0076] There is therefore provided a plant for the conversion of oxygenates to hydrocarbons, the plant comprising:

[0077] - an OTH section comprising: an oxygenate conversion reactor and a separation unit; said OTH section being arranged to receive a a feed stream of one or more oxygenates and provide a converted-oxygenate product; 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);

[0078] - an acid removal section comprising: a filtration unit, a mixing unit upstream said filtration unit, optionally a dosing unit; said acid removal section being arranged to receive said converted-oxygenate product and provide an acid-washed converted-oxygenate product;

[0079] - a separation section, such as a fractionation 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, optionally an off-gas stream such as an off-gas stream comprising C1-C4 hydrocarbons e.g. LPG; wherein said acid removal section further comprises:

[0080] - a mixing point, such as a juncture, for combining said converted oxygenate product with a wash water recycle comprising an alkaline agent into a combined stream; a conduit for withdrawing a first wash water recycle from said filtration unit and a mixing point, such as juncture, for combining said first wash water recycle with said alkaline agent into said wash water recycle;

[0081] - a conduit for supplying said combined stream to said mixing unit and subsequently to said filtration unit;

[0082] - withdrawing from said filtration unit said wash water recycle and said acid-washed converted-oxygenate product; the plant further comprising:

[0083] - a conduit for diverting a portion of said wash water recycle as a bleed stream, and a mixing point, such as a juncture, for combining said bleed stream with said process condensate comprising water and oxygenates into a combined process condensate stream.

[0084] In an embodiment, the plant further comprises a process condensate stripping unit (PC-stripper) arranged to receive said combined process condensate stream and provide: an overhead gas stream free of alkaline agent and comprising unconverted oxygenates, such as unconverted methanol and / or DME; a bottom stream comprising said alkaline agent.

[0085] It is understood that the acids, i.e. organic acids, are also withdrawn as part of the bottom stream from the PC-stripper. The bottom stream is then supplied to a wastewater treatment plant.

[0086] It is understood that the term “conduit” means a process line, such as a pipe, carrying a given process stream.

[0087] In an embodiment, the plant further comprises a conduit for 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. In an embodiment, said downstream filtration unit is a coalescer, said mixing unit is a static mixer i.e. a liquid / liquid static mixer, said alkaline agent is a caustic agent, such as any of NaHCCh or Na2COs; and wherein said acid removal section further comprises a mixing point such a juncture for combining the alkaline agent with said wash water recycle, the acid removal section further comprising a dosing unit, e.g. a caustic dosing unit, to provide said alkaline agent.

[0088] Any of the embodiments and associated benefits of the first aspect (process) of the invention may be used in connection with the second aspect (plant) of the invention, or vice versa.

[0089] The sole appended figure (Fig.) shows a process / plant 10 for the conversion of oxygenates to hydrocarbons according to an embodiment of the invention. The plant (OTH-plant) 10 comprises a OTH-section, an acid removal section and a separation section, as described below. The OTH-section is provided as an OTH-loop section, in particular as a MTH-loop section, more specifically as a MTG-loop section, or a MTO- loop section. The MTH-loop section comprises a MTH reactor 12 as the oxygenate conversion reactor with associated adiabatic fixed bed of catalyst 12’ comprising a zeolite; a separation unit 14 such as a 3-phase separator, overhead recycle 3, 3’ and dedicated recycle compressor as shown in the figure. Downstream, an acid removal section is provided, which comprises: mixing unit 16 such as static mixer 16 (liquid / liquid static mixer), filtration unit 18 such as a coalescer, and dosing unit 20 and wash water recycle 17, 21 , 2T. Farther downstream, a separation section 22, suitably comprising one or more fractionation units, is also provided. The OTH-plant 10 comprises therefore, in this embodiment, a MTG-loop section or MTO-loop section, and further the acid removal section and downstream separation section.

[0090] In the OTH-section, a feed of one or more oxygenates 1 , such as methanol, is combined, e.g. admixed with overhead recycle stream 3’ and introduced as combined feed stream 5 into MTH reactor 12 comprising a catalyst 12’, in which the catalyst comprises a zeolite. A raw converted-oxygenate product 7 is withdrawn and sent to separation unit 14, wherefrom the overhead recycle 3 is separated as so is process condensate 9 comprising water and oxygenates. The oxygenates include unreacted methanol and acids, such as formic acid and acetic acid. Further, a converted-oxygenate product 11 is also separated as the hydrocarbon fraction of the separation unit 14. The converted- oxygenate product 11 still contains acids, such as said formic acid and / or acetic acid as well as other organic acids.

[0091] These are removed by an acid removal step in the acid removal section, by combining stream 11 with wash water recycle 2T from downstream coalescer 18 into a combined stream 13. The acid removal section comprises in this embodiment a liquid / liquid static mixer 16, a coalescer 18 and a dosing unit 20. The combined stream 13 is then supplied to the liquid / liquid static mixer 16 into stream 15, which is subsequently supplied to the coalescer 18, from which wash water recycle stream 17 is withdrawn as well as an acid-washed converted-oxygenate product 23. An alkaline agent 19 from dosing unit 20 is combined with the water wash recycle 17 to form wash water recycle stream 21 comprising the alkaline agent. Further, a portion of said wash water recycle 17, 21 is diverted as a bleed stream 21”, which is then combined with the process condensate 9. The thus combined process condensate stream 9’ is then suitably supplied to a process condensate stripping unit (PC-stripper, not shown). The PC-stripper is arranged to receive said combined process condensate stream 9’ and provide: an overhead gas stream free of alkaline agent and comprising unconverted oxygenates, such as unconverted methanol and / or DME; a bottom stream comprising said alkaline agent (not shown). The acids, i.e. organic acids, are also withdrawn as part of the bottom stream from the PC-stripper. The bottom stream is then supplied to a wastewater treatment plant (not shown). Further, a conduit (not shown) may be provided for 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.

[0092] Downstream the acid removal section, the acid-washed converted-oxygenate product 23 is supplied to separation section, herein simply illustrated as section 22, and which suitably is a fractionation section comprising one or more fractionation units, where at least one of: intermediate naphtha product 25, 25’, 25”, intermediate gasoline product 27, intermediate jet fuel product 29, intermediate diesel product 31, is separated. Also, an off-gas stream 33, for instance an off-gas comprising C1-C4 hydrocarbons such as LPG may be withdrawn. Downstream the separation section 22, hydroprocessing (not shown) such as hydrogenation may be conducted to provide e.g. a final jet fuel product.

Claims

CLAIMS1. 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. 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. 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. 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. 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. Process according to any of claims 1-5, wherein said alkaline agent is a caustic agent, such as any of NaHCCh or Na2COs.

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. 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. 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. 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. 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 beingarranged 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’).

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