The present invention relates to a method and a process plant for flexible production of a gasoline product with a low amount of high boiling hydrocarbons and olefins from methanol and other oxygenates, which optionally may be produced from synthesis gas.

Production of synthetic gasoline from methanol and other easily convertible oxygenates either produced via synthesis gas of fossil or renewable origin or of other origins (commonly known as the methanol to gasoline, MTG, process), results in a product having many characteristics highly suitable for gasoline, but having a distillation curve, which compared to typical fractionated fossil feedstock, comprises a distillation tail rich in diaromatic hydrocarbons, e.g., substituted naphthalenes, and other two-ring structures, e.g., substituted indenes, which have a tendency to formation of deposits and/or particle emissions during combustion in a vehicle engine. Furthermore, the synthetic gasoline comprises an amount of olefins and aromatics. This product distribution from the MTG process is dictated by kinetics and equilibrium, and may be close to or in conflict with regulations on boiling points and concentrations of regulated constituents in gasoline, and the nature of the MTG process only provides few possibilities for adjusting the product distribution. The heaviest product fraction could be removed by fractionation and used for fuel oil in the process, however, this option is associated with a loss of profit, so instead there is a need for a chemical solution to this problem.

Recent regulations for gasoline specifications in various jurisdictions include upper limits for Tgo of 152°C (305°F) and less than 6 vol% olefins in strict specifications or Tgo of 168°C (335°F) and less than 10 vol% olefins in intermediate specifications in contrast to commonly Tgo of 190°C (375°F) and less than 18 vol% olefins in prior specifications. Some such specifications are indirect, by specifying properties after blending, e.g. with ethanol. For convenience, the examples of specifications will be referred to throughout the present application under the terms strict specifications and intermediate specifications, without implying any legal compliance with specific regulations, unless expressly stated. Since synthetic gasoline from a production plant may be distributed to different markets, with different gasoline specifications, there is a need for a production process which provides flexibility for the production plant.

In the following the term effective conditions of a reaction shall be used to signify conditions, such as pressure, temperature and space velocity, under which the conversion by said reaction is at least 10%, unless otherwise stated.

In the following the term ppmw shall be used to signify weight parts per million.

In the following the term wt% this shall be used to signify weight/weight %.

In the following the term vol% this shall be used to signify vol/vol %.

In the following the term Cn shall be used to signify hydrocarbons with exactly n carbon atoms, e.g. C10 signifies hydrocarbons with exactly 10 carbon atoms. Similarly, Cn+ shall be used to signify hydrocarbons with at least n carbon atoms, e.g. C10+ signifies hydrocarbons with at least 10 carbon atoms

In general, boiling points are determined according to ASTM D86, unless otherwise specified. In this respect T _n shall be used to signify the temperature at which n vol% has been distilled in the equipment defined by ASTM D86, e.g. Tgo is the temperature at which 90 vol% of the hydrocarbon mixture has been distilled.

In the following, a synthetic hydrocarbon mixture produced from a mixture of reactive oxygenates may be understood as a hydrocarbonaceous mixture wherein at least 50% of the C9 aromatics present in said hydrocarbonaceous mixture are tri-methyl benzenes.

A broad aspect of the present disclosure relates to a method for providing a synthetic gasoline product comprising less than a specified concentration of olefins, such as 6 vol% or 11 vol% from a first synthetic hydrocarbon mixture produced from a mixture of reactive oxygenates, said first synthetic hydrocarbon mixture having T90 of less than 140°C and comprising at least said specified concentration of olefins and a second synthetic hydrocarbon mixture, produced from a mixture of reactive oxygenates, said second synthetic hydrocarbon mixture having T90 of more than 150°C said method comprising the steps of a. directing the second synthetic hydrocarbon mixture to contact a material catalytically active in hydrocracking under effective hydrocracking conditions, to provide a hydrocracked second synthetic hydrocarbon mixture, b. directing said first synthetic hydrocarbon mixture to contact a material catalytically active in olefin hydrogenation, to provide a hydrogenated hydrocarbon mixture, wherein said hydrocracked second synthetic hydrocarbon mixture is either added to the first synthetic hydrocarbon mixture upstream contacting said material catalytically active in olefin hydrogenation or it is added to hydrogenated hydrocarbon mixture, downstream contacting said material catalytically active in olefin hydrogenation to provide said synthetic gasoline product.

This has the associated benefit of enabling a flexible production of synthetic gasoline adhering to strict specifications or intermediate specifications for boiling point and concentration of olefins as required.

In a further embodiment effective hydrocracking conditions involve a temperature in the interval 250-425°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-4, optionally together with intermediate cooling by quenching with hydrogen, feed or product and wherein the material catalytically active in hydrocracking comprises (a) one or more active metals taken from the group platinum, palladium, nickel, cobalt, tungsten and molybdenum, (b) an acidic support showing cracking activity, such as amorphous acidic oxides and molecular sieves and (c) a refractory support such as alumina, silica or titania, or combinations thereof. This has the associated benefit of such conditions being effective for hydrocracking of synthetic gasoline. Typically, the conditions are chosen such that the amount of material boiling above 190°C in said hydrocracked hydrocarbon stream fraction is reduced by at least 20%wt, 50%wt or 80%wt or more compared to said hydrocracker feed stream. In a further embodiment effective hydrogenation conditions involve a temperature in the interval 220-350°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-4, optionally together with intermediate cooling by quenching with hydrogen, feed or product and wherein the material catalytically active in hydrocracking comprises 0.1% to 30% of one or more active metals taken from the group platinum, palladium, nickel, cobalt, tungsten and molybdenum and a refractory support such as alumina, silica or titania, or combinations thereof, such as 5-20 wt% sulfided molybdenum or tungsten and 1-10 wt% sulfided nickel or cobalt on an alumina support. This has the associated benefit of such conditions being effective for hydrogenations of olefins in synthetic gasoline. Typically, the conditions are chosen such that the amount of olefins is reduced by from 20%wt to 80%wt or more compared to the feed stream to the hydrogenation unit.

In a further embodiment said one or more active metals of said material catalytically active in hydrocracking are taken from the group consisting of nickel, cobalt, tungsten and molybdenum and the hydrocracking feedstock contacting the material catalytically active in hydrocracking comprises at least 50 ppmw sulfur. This has the associated benefit of such a material catalytically active in hydrocracking having a low cost.

In a further embodiment said one or more active metals of said material catalytically active in hydrocracking are taken from the group consisting of platinum and palladium and the hydrocracking feedstock contacting the material catalytically active in hydrocracking comprises at less than 50 ppmw sulfur. This has the associated benefit of such a material catalytically active in hydrocracking having a high selectivity.

In a further embodiment said one or more active metals of said material catalytically active in isomerization are taken from the group consisting of nickel, cobalt, tungsten and molybdenum and the hydrocracking feedstock comprises at least 50 ppmw sulfur. This has the associated benefit of such a material catalytically active in isomerization having a low cost.

In a further embodiment said one or more active metals of said material catalytically active in isomerization are taken from the group consisting of nickel, platinum and palladium and the hydrocracking feedstock comprises at less than 50 ppmw sulfur. This has the associated benefit of such a material catalytically active in isomerization having a high selectivity.

In a further embodiment said first synthetic hydrocarbon mixture and said second synthetic hydrocarbon mixture are provided by fractionation of a synthetic hydrocarbon mixture produced from a mixture of reactive oxygenates, optionally after one or both synthetic hydrocarbon mixtures having contacted a material catalytically active in a hydroprocessing process under active hydroprocessing conditions. This has the associated benefit of enabling a flexible production of synthetic gasoline adhering to strict specifications or intermediate specifications, based on a separation commonly carried out already in the stabilization of the synthetic gasoline.

In a further embodiment said fractionation provides a third synthetic hydrocarbon mixture, having a T90 above that of said second synthetic hydrocarbon mixture and wherein said third synthetic hydrocarbon mixture is directed to contact a material catalytically active in hydrocracking under active hydrocracking conditions, to provide a hydrocracked third synthetic hydrocarbon mixture, which is included in said synthetic gasoline product, either by addition upstream said fractionation or by addition in a position downstream said fractionation. This has the associated benefit of further hydrocracking an amount of synthetic gasoline under mild conditions, ensuring a product adhering to strict specifications or intermediate specifications, while minimizing the yield loss.

In a further embodiment said hydrocracking process conditions for the hydrocracking feedstock are chosen, such that the molar ratio between hydrocarbons comprising exactly 10 carbon atoms in the hydrocracked hydrocarbon stream and the hydrocracking feedstock is less than 20%. This has the associated benefit of such a high hydrocracking conversion simplifying the process by avoiding operation with recycle.

In a further embodiment the conditions of the hydrocracking step for the hydrocracking feedstock and the amount of recycled hydrocarbon stream are such that the ratio of the mass of hydrocarbons comprising at least 11 carbon atoms in the synthetic gasoline to the mass of hydrocarbons comprising at least 11 carbon atoms in the synthetic hydrocarbon mixture is less than 5%. This has the associated benefit of a recycle process being able to obtain high overall hydrocracking conversion but maintaining moderate conditions and thus moderate conversion per pass.

A further aspect of the present disclosure relates to a method for production of a synthetic gasoline product from a synthetic hydrocarbon mixture produced from a mixture of reactive oxygenates comprising the steps of i. fractionating the synthetic hydrocarbon mixture in at least a low boiling hydrocarbon fraction and an intermediate boiling hydrocarbon fraction, ii. directing at least an amount of said intermediate boiling hydrocarbon fraction to contact a material catalytically active in isomerization under effective isomerization conditions to provide an isomerized intermediate boiling hydrocarbon fraction, iii. directing at least an amount of said isomerized intermediate boiling hydrocarbon fraction to contact a material catalytically active in hydrocracking under effective hydrocracking conditions to provide a hydrocracked intermediate boiling hydrocarbon fraction, iv. combining at least an amount of said low boiling hydrocarbon fraction with said hydrocracked intermediate boiling hydrocarbon fraction to provide a hydrogenation feed stream and directing this hydrogenation feed stream to contact a material catalytically active in hydrogenation under effective hydrogenation conditions providing a hydrogenated hydrocarbon product stream.

This has the associated benefit of enabling a flexible production of synthetic gasoline adhering to strict specifications or intermediate specifications, based in a process integrated with the stabilization of synthetic gasoline, wherein the amount of psedocumene in said isomerized hydrocarbon stream is reduced by at least 20%wt, 50%wt or 80%wt or more compared to said intermediate boiling hydrocarbon fraction.

In a further embodiment the method further comprises the steps of v. further separating the synthetic hydrocarbon mixture in a higher boiling fraction comprising at least 70% of the molecules comprising 10 or more carbon atoms present in the hydrocarbon mixture, vi. directing at least an amount of said higher boiling hydrocarbon fraction as a hydrocracking feedstock to contact a material catalytically active in hydrocracking under effective hydrocracking conditions providing a hydrocracked hydrocarbon stream and vii. separating said hydrocracked hydrocarbon stream, in the same or an additional separation step, to provide a high boiling hydrocracked hydrocarbon stream and an intermediate boiling hydrocracked hydrocarbon stream, wherein at least an amount of said intermediate boiling hydrocracked hydrocarbon stream, is added to at least an amount of either said intermediate boiling hydrocarbon fraction or said isomerized intermediate boiling hydrocarbon fraction.

This has the associated benefit of further hydrocracking an amount of synthetic gasoline with high overall hydrocracking conversion but maintaining moderate conditions and thus moderate conversion per pass, ensuring a product adhering to strict specifications or intermediate specifications, while minimizing the yield loss.

In a further embodiment effective hydrocracking conditions involve a temperature in the interval 250-425°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-4, optionally together with intermediate cooling by quenching with hydrogen, feed or product and wherein the material catalytically active in hydrocracking comprises (a) one or more active metals taken from the group platinum, palladium, nickel, cobalt, tungsten and molybdenum, (b) an acidic support showing cracking activity, such as amorphous acidic oxides and molecular sieves and (c) a refractory support such as alumina, silica or titania, or combinations thereof. This has the associated benefit of such conditions being effective for hydrocracking of synthetic gasoline. Typically, the conditions are chosen such that the amount of material boiling above 190°C in said hydrocracked hydrocarbon stream fraction is reduced by at least 20%wt, 50%wt or 80%wt or more compared to said hydrocracker feed stream.

In a further embodiment effective isomerization conditions involves a temperature in the interval 250-350°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8 and wherein the material catalytically active in isomerization comprises one or more active metals in their active form taken from the group elemental platinum, elemental palladium, elemental nickel, sulfided nickel, sulfided cobalt, sulfided tungsten and sulfided molybdenum, one or more acidic supports, preferably molecular sieves, such as those having a topology taken from the group comprising MFI, FAU, BEA, MOR, FER, MRE, MWW, AEL, TON and MTT and an amorphous refractory support comprising one or more oxides taken from the group comprising alumina, silica and titania. This has the associated benefit of such process conditions and catalytically active materials being highly suited for efficient conversion of especially pseudocumene to mesitylene. Typically, the amount the amount of psedocumene in said isomerized hydrocarbon stream is reduced by at least 20%wt, 50%wt or 80%wt or more compared to said intermediate boiling hydrocarbon fraction.

A further aspect of the present disclosure relates to a process for production of a synthetic gasoline product from a feedstock comprising methanol, said process comprising the steps of;

A. directing a stream comprising methanol to contact a material catalytically active in methanol to gasoline conversion providing a raw synthetic gasoline,

B. stabilizing said raw synthetic gasoline by separating a fraction boiling below 40°C from the raw synthetic gasoline, thereby providing a synthetic hydrocarbon mixture

C. directing said synthetic hydrocarbon mixture to react according to a method according to a previous aspect or embodiment.

This has the associated benefit of such a process making an efficient conversion of methanol to a synthetic gasoline matching strict requirements to distillation curve specifications.

A further aspect of the present disclosure relates to a gasoline post-treatment unit for combining and post-treating two streams of synthetic hydrocarbons, a low boiling hydrocarbon inlet, comprising an intermediate boiling hydrocarbon inlet and an upgraded synthetic gasoline product outlet, an post-treatment hydrocracking unit, having an inlet and an outlet and a hydrogenation unit having an inlet and an outlet, wherein the intermediate boiling hydrocarbon inlet is in fluid communication with said post-treatment hydrocracking unit inlet and said post-treatment hydrocracking unit outlet is in fluid communication with either said hydrogenation unit inlet or said upgraded synthetic gasoline product outlet, and said low boiling hydrocarbon inlet is in fluid communication with said hydrogenation unit inlet and the hydrogenation unit outlet is in fluid communication with the upgraded synthetic gasoline product outlet. This has the associated benefit of such a gasoline upgrading unit being flexible and efficient for provision of a synthetic gasoline in compliance with the strict or intermediate specifications as required.

A further aspect of the present disclosure relates to a process plant for production of a synthetic gasoline product comprising a gasoline post-treatment unit according to the previous aspect, and a hydrocarbon synthesis section having an oxygenate inlet and a synthetic hydrocarbon outlet, a gasoline splitter section, having an inlet and at least a low boiling hydrocarbon outlet, an intermediate boiling hydrocarbon outlet and a high boiling hydrocarbon outlet and a hydrocracking section having an inlet and an outlet, and an optional isomerization section having an inlet and an outlet, wherein the gasoline splitter section inlet is in fluid communication with the synthetic hydrocarbon outlet, wherein if the optional isomerization section is absent, the intermediate boiling hydrocarbon outlet is in fluid communication with the low boiling hydrocarbon inlet of the gasoline post-treatment unit or wherein if the optional isomerization section is present, the intermediate boiling hydrocarbon outlet is in fluid communication with the inlet of the optional isomerization section and the outlet of the optional isomerization section is in fluid communication with the low boiling hydrocarbon inlet of the gasoline post-treatment unit, wherein the high boiling hydrocarbon outlet is in fluid communication with the hydrocracking section inlet and the hydrocracking section outlet is in fluid communication with the gasoline splitter section inlet, or in fluid communication with a further means of separation having an high boiling hydrocarbon outlet in fluid communication with the gasoline splitter section inlet and an intermediate boiling hydrocarbon outlet in fluid communication with either the intermediate boiling hydrocarbon outlet of the gasoline splitter section or the intermediate boiling hydrocarbon inlet of the gasoline posttreatment unit.

This has the associated benefit of such a process making an efficient conversion of methanol to a synthetic gasoline matching strict requirements to distillation curve and olefin concentration specifications.

In a further embodiment an intermediate boiling fraction being an amount of the synthetic hydrocarbon mixture, is directed to contact a material catalytically active in isomerization under effective isomerization conditions, and wherein the intermediate boiling hydrocarbon fraction contains at least 80% of the molecules comprising exactly 9 carbon atoms of the synthetic hydrocarbon mixture with the associated benefit of such a process increasing the octane number of the synthetic hydrocarbon mixture, by conversion of pseudocumene to mesitylene.

In a further embodiment the aromatics comprising 10 or more carbon atoms in the intermediate boiling fraction accounts for less than 5%, 10% or 20% of the aromatics comprising 10 or more carbon atoms in the synthetic hydrocarbon mixture, with the associated benefit that when a minimum of C10+ aromatics are present in the intermediate boiling fraction, a majority is present in the high boiling hydrocarbon fraction such that the selective separation maximizes the amount of high boiling hydrocarbons to undergo hydrocracking.

The conversion of methanol or methanol/dimethyl ether mixtures into gasoline is generally referred to as the Methanol-to-Gasoline (MTG) process. In this process the methanol reactant is typically synthetized from a synthesis gas, which may be made by gasification of solid carbonaceous material or by reforming liquid or gaseous hydrocarbons, typically natural gas. The gasoline synthesis takes place in well-known fixed bed and/or fluidized bed reactors and is typically carried out at a pressure of 10-40 bar and a temperature of 280-450°C, preferably 300-430°C. The effluent from the gasoline synthesis section, which is enriched in gasoline components and water, low boiling olefinic hydrocarbons, methane and paraffins, is cooled and passed to a three phase separating unit where a non-polar phase comprising C3+ hydrocarbons (including paraffins, naphthenes, aromatics and olefins), a polar phase comprising water, oxygenated hydrocarbon by-products and unconverted oxygenates, and a gaseous phase comprising uncondensables (H2, CO, CO2 etc.), light ends (CH4, C2H6) and low boiling olefins are separated. The gaseous phase is normally split in a purge stream and a recycle stream directed for the production of synthesis gas.

Raw synthetic gasoline is typically fed to a degassing unit to remove fuel gas and LPG fraction and volatile by-products dissolved in the raw synthetic gasoline, to provide a stabilized synthetic gasoline. This degassing unit may be either independent or integrated into other means of separation for the synthetic gasoline. Although the conversion of methanol or methanol/dimethyl ether mixtures into gasoline is generally referred to as the Methanol-to-Gasoline process, oxygen-containing hydrocarbons (oxygenates) other than methanol are also easily converted in the MTG process. Apart from the desired portion of especially C5+ gasoline products and co-produced water, gasoline synthesis results in some by-production of olefins, paraffins, methane and products from thermal cracking (hydrogen, CO, CO2). Subsequent separation and/or distillation ensures the upgrading of the raw hydrocarbon product mixture to useful gasoline. Naturally, a high yield of the useful gasoline products is desirable for obtaining proper process economy.

The synthesis gas for reacting to form the reactive oxygenates for the MTG process, may be made any by synthesis gas production processes well known to the skilled person. These processes may involve gasification of carbonaceous materials, such as coal, (typically high boiling) hydrocarbons, solid waste and biomass; from reforming of liquid or gaseous hydrocarbons, typically natural gas; from coke oven waste gas; from biogas or from combination of streams rich in carbon oxides and hydrogen - e.g. of electrolytic origin. When the oxygenates originates from biomass, they may be created by synthesis or fermentation and they may be characterized by having a 14C-isotope content above 0.5 parts per trillion of the total carbon content. Oxygenates originating from biomass will be beneficial due to a reduced CO2 emission.

The synthesis section for the production of easily convertible oxygenates may consist of a one-step methanol synthesis, a two-step methanol synthesis, a two-step methanol synthesis followed by a DME synthesis, or a methanol synthesis step followed by a combined methanol and DME synthesis step and a DME synthesis step or a one-step combined methanol and DME synthesis. It would be understood that the number of possible combinations of means of co-feeding into the methanol/DME synthesis loop and the layouts of the methanol or methanol/dimethyl ether synthesis is large. Any combinations deductible is therefore to be regarded as embodiments of present invention.

A catalytically active material comprising a zeolite is used for the conversion of oxygenates to gasoline products. This may be any zeolite type being known as useful for the conversion of oxygenates to gasoline range boiling hydrocarbons. Preferred types are those with a silica to alumina mole ratio of at least 12 and pore sizes formed by up to 12 membered rings, preferably 10 membered. Examples of such zeolites are those having one of the topologies MFI, MEL, MTW, MTT, FER such as ZSM-5, ZSM-11 , ZSM-12, ZSM-23, ZSM-35 and ZSM-38. The manufacture of these is well known in the art and the catalysts are commercially available. A common catalytically active material is the ZSM-5 zeolite in its hydrogen form, i.e. HZSM-5.

Without being bound by theory, the synthesis of gasoline from oxygenates is in simple terms based on conversion of some methanol (a C1 compound) to dimethylether (a C2 compound). Methanol (C1) and dimethylether (C2) react to form olefins (C2-C5), and the olefins react to form aromatics and naphthenics (C6-C11+) as well as longer olefins and paraffins (C6-C11). The gaseous compounds (C1-C3) are recycled to synthesis gas production and the high boiling compounds constitute a mixture corresponding qualitatively to fossil naphtha. As the catalyst is deactivated, synthesis temperature is increased and as a result the relative activity of side reactions towards forming longer olefins is increased.

While functionally equivalent, to naphtha obtained by hydroprocessing of fossil hydrocarbons, the synthetic gasoline has a different carbon distribution, resulting into a slightly higher boiling range of products, typically with a lower amount of C6 and C7 hydrocarbons, a higher amount of C8, C9 and C10 hydrocarbons as well as a presence of C11 + hydrocarbons in the 2-5wt% range, which would be substantially absent in fractionated fossil hydrocarbons. A further difference between the nature of fossil gasoline and synthetic gasoline is the fact that fossil gasoline is a mixture of hundreds of different molecules, whereas synthetic gasoline is dominated by as few as 10 different molecules that account for approximately 50 wt% of the total composition. The nature of the synthetic gasoline is illustrated in Table 1.

A common C10 hydrocarbon in the synthetic gasoline product is durene (1 ,2,4,5- tetramethylbenzene), which has a melting point of 79.2°C and a boiling point of 196°C. The high melting point is problematic for the final gasoline product, especially in cold climates. The other tetramethylbenzenes have a much lower melting point and a slightly higher boiling point. Among the C9 hydrocarbons in the synthetic gasoline product, pseudocumene (1 ,2,4- trimethylbenzene) is the most abundant, whereas the isomer mesitylene (1 ,3,5-trime- thylbenzene) is less common. The octane number of mesitylene is 171 , i.e. higher than the octane number of 148 for pseudocumene but the melting point and boiling points are similar (mesitylene/pseudocumene m.p. of -45/-44°C and b.p. of 165/169°C, respectively).

The C11+ hydrocarbons are often diaromatics and are undesired in gasoline due to the potential formation of particulate matter during combustion.

As shown in Table 1 , an inherent product group in the synthesis of gasoline from methanol is olefins. The majority of olefins will be C7 and C8 compounds. Typically, around 6-15 wt% olefins are produced, which is in compliance with typical intermediate specification, but not in compliance with strict specifications.

A synthetic gasoline product with lower content of C8+ compounds would thereforebe preferable, as the resulting boiling point distribution would be in compliance with strict specifications, and a simple solution ensuring compliance with all current gasoline standards would be a separation of C8+ products and directing these to other uses. Unfortunately, the chemical nature of the C8+ fraction is not favorable for alternative valuable use, and therefore the use would typically to direct this fraction for use in fired heaters or for recycle to be used in the synthesis gas. Since this would constitute a yield loss of at least 20% this is not a desirable solution.

An aspect to keep in mind when considering the product composition of the MTG process, is that the MTG synthesis process results in a more homogeneous product composition, contrary to fossil gasoline. This has practical implications, e.g. on the separation processes, where the distillation curve for synthetic gasoline is not semi-continuous as for fossil feedstocks, and therefore the manipulation by fractionation is less flexible for synthesized gasoline compared to fossil gasoline, such that even a minor shift of fractionation temperature may result in a dramatic shift in the fraction withdrawn. Instead of separation, selective catalytic upgrading, especially of the C8+ fraction may be considered, and efficient means for that include isomerization, hydrocracking and saturation of olefins.

Isomerization is the conversion of constituents into other constituent having the same molecular formula. The objective of isomerization is to convert undesired constituents to desired constituent, e.g. conversion of pseudocumene to mesitylene and durene to isodurene

An isomerization process for the combined conversion of pseudocumene to mesitylene and durene to isodurene was proposed in WO2013/178375 A1. This process involves treating a high boiling fraction of the synthetic gasoline over a sulfided nickel isomerization catalyst comprising a zeolite of the MFI topology such as ZSM-5, which improved octane numbers as well as cold flow properties by an increased selectivity for favorable isomerization over a non-sulfided catalyst.

This isomerization process will however not solve the problem of strict specification for the distillation curve since the products of isomerization will boil at similar temperatures as the parent molecule. C11+ compounds, which are the main constituents of the distillation tail of the synthetic gasoline, are typically not converted to lower boiling products at the isomerization conditions in WO2013/178375 A1.

In a more general perspective, the material catalytically active in isomerization of synthetic gasoline typically comprises an active metal (which according to the present disclosure is preferred to be either sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum alone or in combination or one or more elemental reduced metals such as nickel, platinum and/or palladium), an acidic support (typically a molecular sieve showing high shape selectivity, and having a topology such as MFI, FAU, BEA, MOR, FER, MRE, MWW, AEL, TON and MTT) and a typically amorphous refractory support (such as alumina, silica or titania, or combinations thereof). Specific examples are material catalytically active in isomerization comprising sulfided or reduced Ni in combination with ZSM-5, reduced Ni in combination with silica-alumina, sulfided NiW in combination with y-alumina, reduced Pt in combination with ZSM-5, reduced Pt in combination with zeolite Y, all supported on an amorphous material, such as alumina. The catalytically active material may comprise further components, such as boron or phosphorous.

Effective isomerization conditions typically involve directing the intermediate synthetic gasoline fraction to contact a material catalytically active in isomerization under effective isomerization conditions. The conditions are typically a temperature in the interval 250- 430°C, a pressure in the interval 50-100 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.3-8. Increasing temperature or decreasing LHSV will, as it is known to the skilled person, increase the process severity and thus the isomerization conversion. Isomerization is substantially thermally neutral and consumes only hydrogen in hydrocracking side reactions so only a moderate amount of hydrogen is added in the isomerization reactor. If the active metal on the material catalytically active in isomerization is in elemental form, the isomerization feedstock must only comprise potential catalyst poisons in low levels such as levels of sulfur below 50 ppmw or even 1-10 ppmw, which may require purification. If the active metal is in sulfided form, a level of sulfur above 50 ppmw is required.

The Tgo requirements may be met by converting the high boiling fraction of synthetic gasoline to a lower boiling fraction by catalytic hydrocracking. Such a process will convert at least an amount of the di-aromatics to mono-aromatics and dealkylate multi-substituted monoaromatics to lower boiling compounds, thus reducing the intermediate boiling point and high boiling point of the product distillation curve. The initial boiling point (IBP) of the high boiling fraction that will be selectively hydrocracked is selected/determined according to an optimization of the conversion required to meet distillation points specifications whilst minimizing octane rating loss incurred by dealkylation and hydrogenation reactions.

Hydrocracking involves directing high boiling synthetic gasoline fraction to contact a material catalytically active in hydrocracking. The material catalytically active in hydrocracking typically comprises an active metal (which may be one or more sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum or reduced noble metals such as Pt, Pd or PdPt), an acidic support (typically a molecular sieve showing high cracking activity, and having a topology such as MFI, BEA, FAU and MOR, but amorphous acidic oxides such as silica-alumina may also be used) and a refractory support (such as alumina, silica or titania, or combinations thereof). The catalytically active material may comprise further components, such as boron or phosphorous.

Effective hydrocracking conditions are typically a temperature in the interval 250-430°C, a pressure in the interval 20-100 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.3-10. Increasing temperature or decreasing LHSV will, as it is known to the skilled person, increase the process severity and thus the hydrocracking conversion, i.e. the amount of product having a lower molecular weight than the feedstock. As hydrocracking is exothermic, the process may involve intermediate cooling e.g. by quenching with cold hydrogen, feed or product. A high boiling synthetic gasoline fraction, including the treat gas, is typically directed to contact the material catalytically active in hydrocracking without further purification. When the active metal(s) on the material catalytically active in hydrocracking are base metals, this mixture of hydrocarbons and treat gas should preferably contain at least 50 ppmw sulfur and when it is a noble metal the sulfur level should preferably be below 10 ppmw sulfur.

As shown, olefins may be present in too high concentration in the raw synthetic gasoline. They may be removed by a catalytic hydrogenation process, where hydrogen reacts with the olefin to saturate olefinic double bonds.

The material catalytically active in hydrogenation of olefins typically comprises an active metal (sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum, but possibly also either elemental noble metals such as platinum and/or palladium) and a refractory support (such as alumina, silica or titania, or combinations thereof). The most common catalytically active materials will be sulfided molybdenum (5-20 wt%) and nickel (1-10 wt%) on an alumina support.

Effective hydrogenation conditions are typically a temperature in the interval 220-350°C, a pressure in the interval 10-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.1-10, optionally together with intermediate cooling by quenching with cold hydrogen, feed or product. Hydrogenation of olefins will typically also occur in contact with materials catalytically active in other hydroprocessing reactions such as hydrocracking and isomerization, under the conditions for these processes.

Some embodiments of the present disclosure, may involve the use of a catalytically active material comprising a sulfided base metal. In such embodiments, addition of a sulfur donor is required to maintain sulfidation, and thus activity, of the sulfided active metal, since the synthetic gasoline is inherently sulfur free. Similarly, embodiments may be envisioned in which such added sulfur must be removed upstream a catalytically active material based on noble metals. Typically sulfur removal will occur in relation to stabilization of intermediate products.

A process plant for upgrading of synthetic gasoline to comply with intermediate specifications for Tgo and olefin content will, as mentioned above, beneficially involve a single intermediate product fractionation distributing product between the different treatments, such that C10+ will be directed to hydrocracking and C9 to isomerization, in order to adjust boiling point and boost the octane number, while lower boiling hydrocarbons will be by-passed such reactions to ensure a minimal yield loss.

A process for providing a product which is compatible with strict specifications would also require hydrocracking and isomerization as well as some olefin hydrogenation of the synthetic gasoline. As mentioned hydrogenation of olefins will also occur under the reaction conditions for isomerization. Conveniently the C9+ fraction would require hydrocracking and the C7 fraction (or at least a part of it) and the C8 fraction would contain a high amount of olefins to be saturated, and therefore a simple process for compliance with strict specifications with a low number of reactors would involve splitting the synthetic gasoline in a C3-C6/C7 fraction which is passed untreated as product, a C7/C8- C9 fraction for isomerization and hydrogenation and a C10+ fraction for hydrocracking with recycle of the product.

By this process configuration flexibility is obtained in a simple configuration. However, a detailed analysis of the process shows that implementing this configuration will having higher capital and operational cost. Due to the increased process volume and related increased gas flows the cost related to reactors and reactor internals as well as compressors and other aspects of the process gas loop also increase. An increase in makeup hydrogen addition will also be necessary. Therefore following this analysis a process configuration in which two extra reactors are provided downstream the process configuration complying with the intermediate specifications is surprisingly found to be more cost-effective.

According to such a process, the synthetic gasoline is split in a C3-C8 fraction which is passed untreated as product, a C9+ fraction for isomerization and a C10+ fraction for hydrocracking with recycle of the product. The isomerized C9+ fraction is then further hydrocracked and combined with the C3-C8 fraction, the combined stream is subsequently directed for olefin saturation. While such a process has the added cost of two reactors, the total volume of reactors and the total volume of catalyst required is reduced, with substantial savings as the result.

Figures

Figure 1 shows a process for producing a synthetic gasoline product comprising a gasoline upgrade unit according to the present disclosure

Figure 2 shows a process for producing a synthetic gasoline, in which gasoline is upgraded without a separate gasoline upgrade unit by a process integrated in the gasoline stabilization unit.

Figure 1 shows an embodiment of the present disclosure, which is configured for providing a synthetic gasoline complying with strict specifications for boiling point and olefin content, while also minimizing loss of octane number rating by inclusion of an isomerization unit, and for maximizing the gasoline yield by a low extent of hydrocracking per pass in combination with recycling the hydrocracked higher boiling hydrocarbon fraction. Here a carbonaceous feed stream (2), typically natural gas, but optionally a solid feedstock such as coal or renewable feedstock, is directed to a methanol front-end process unit (MFP). For solid feedstock, a gasifier will produce a synthesis gas, whereas natural gas is converted to synthesis gas in a reformer. The synthesis gas is cleaned, and the composition may be adjusted to match the requirements of a downstream methanol synthesis unit, in which synthesis gas is catalytically converted to methanol. The produced methanol (4) is directed to a hydrocarbon synthesis unit (MTG) in which methanol (4) is converted to a raw synthesized hydrocarbon mixture (6). The raw synthesized hydrocarbon mixture (6) is directed to gasoline treatment unit (GTU) comprising a gasoline splitter section (GSS), which may comprise several sub-units, typically including a three-phase separator, separating incondensable gases, water and raw synthetic gasoline. The raw hydrocarbon mixture (6) is typically stabilized in a de-ethanizer and an LPG splitter, to provide one or more gaseous hydrocarbon streams and a synthesized hydrocarbon mixture. For simplicity the figure does not show withdrawal of one or more gas streams comprising H2, CO, CH4, C2H6, C3H8, C4H10, and to some extent, C5H12, but in practice it is typically split in multiple fractions as described. The gasoline splitter section (GSS) further splits the synthesized hydrocarbon mixture in a low boiling hydrocarbon fraction (10) boiling in the gasoline range, and typically comprising C4-C8 hydrocarbons, an intermediate boiling hydrocarbon fraction (12), typically dominated by C9 hydrocarbons and a higher boiling hydrocarbon fraction (14) comprising C10+ hydrocarbons.

The intermediate boiling hydrocarbon fraction (12) is directed to a hydroisomerization unit (ISOM), in which pseudocumene is converted to mesitylene, resulting in increased octane number providing an isomerized intermediate boiling hydrocarbon fraction (16). The higher boiling hydrocarbon fraction (14) is directed to a hydrocracking unit (HDC), in which the C10+ hydrocarbons are converted mainly to C8-C9 hydrocarbons by hydrocracking, providing a hydrocracked higher boiling hydrocarbon fraction (18). The hydrocracked higher boiling hydrocarbon fraction (18) is directed to feed the gasoline splitter section (GSS), such that light and intermediate boiling hydrocracked products are directed to the low boiling hydrocarbon fraction (10) and intermediate boiling hydrocarbon fraction (12), whereas the higher boiling hydrocracked products are directed to the higher boiling hydrocarbon fraction (14), and thus recycled to the inlet of the hydrocracking unit (HDC), allowing milder hydrocracking conditions per pass, as any unconverted high boiling hydrocarbons will be recycled.

During production of strict specification gasoline, the low boiling hydrocarbon fraction (10) and the isomerized intermediate boiling hydrocarbon fraction (16) will be directed to a gasoline post-treatment unit (GPT) which may be integrated into the gasoline treatment unit (GTU) or be positioned separately, and possibly receive additional feed streams. The gasoline post-treatment unit (GPT) will contain an post-treat hydrocracker unit (PHC) containing a material catalytically active in hydrocracking, which may be the same or different from the material catalytically active in hydrocracking in the hydrocracker unit (HDC) and a hydrogenation unit (HYD) containing a material catalytically active in hydrogenation of olefins.

The post-treat hydrocracker unit (PHC) will receive the stream of isomerized intermediate boiling hydrocarbon fraction (16), and be configured for an appropriate conversion, resulting in the boiling point being reduced to the extent required for compliance with specifications, to provide a hydrocracked isomerized hydrocarbon fraction (20), which without removal of gas phase including hydrogen is combined with the low boiling hydrocarbon fraction (10) and directed to the hydrogenation unit (HYD) for partial or complete saturation of olefins.

During production of intermediate specification gasoline, the low boiling hydrocarbon fraction (10) and the isomerized intermediate boiling hydrocarbon fraction (16) may be combined, to provide a synthetic gasoline product (24), to reduce process complexity and operating cost.

Hydrogen is added to the hydrocracking, isomerization and hydrogenation units, and the products therefrom are typically stabilized in a separator, by withdrawing light gases but for simplicity this is not shown.

Figure 2 shows a process, which is configured for providing a synthetic gasoline complying with strict specifications for boiling point and olefin content, while also minimizing loss of octane number rating, by inclusion of an isomerization unit, and for maximizing the gasoline yield by a low extent of hydrocracking per pass in combination with recycling the hydrocracked higher boiling hydrocarbon fraction. Here a carbonaceous feed stream (2), typically natural gas, but optionally a solid feedstock such as coal or renewable feedstock, is directed to a methanol front-end process unit (MFP). For solid feedstock, a gasifier will produce a synthesis gas, whereas natural gas is converted to synthesis gas in a reformer. The synthesis gas is cleaned, and the composition may be adjusted to match the requirements of a downstream methanol synthesis unit, in which synthesis gas is catalytically converted to methanol. The produced methanol (4) is directed to a hydro- carbon synthesis unit (MTG) in which methanol is converted to a raw synthesized hydrocarbon mixture (6). The raw synthesized hydrocarbon mixture (6) is directed to gasoline treatment unit (GTU) comprising a gasoline splitter section (GSS), which may comprise several sub-units, typically including a three-phase separator, separating incondensable gases, water and raw synthetic gasoline. The raw hydrocarbon mixture is typically stabilized in a de-ethanizer and an LPG splitter, to provide one or more gaseous hydrocarbon streams and a synthesized hydrocarbon mixture. For simplicity the figure does not show withdrawal of a gas stream comprising H2, CO, CH4, C2H6, C3H8, and C4H10, but in practice it is typically split in multiple fractions as described. The gasoline splitter section (GSS) further splits the synthesized hydrocarbon mixture in three fractions, although a higher number of fractions may be provided. When producing synthetic gasoline (24) according to intermediate specifications, the split will be in a low boiling hydrocarbon fraction (10) typically comprising C4-C8 hydrocarbons, an intermediate boiling hydrocarbon fraction (12), typically dominated by C9 hydrocarbons and a higher boiling hydrocarbon fraction (14) comprising C10+ hydrocarbons. When producing synthetic gasoline (24) according to strict specifications, the gasoline splitter section (GSS) may also be configured such that the low boiling hydrocarbon fraction (10) comprises C4-C7 hydrocarbons, the intermediate boiling hydrocarbon fraction (12), comprises some C7 and C10 as well as the majority of C8 and C9 hydrocarbons and a higher boiling hydrocarbon fraction (14) comprising C10+ hydrocarbons, which would be the gasoline split configuration chosen for compliance with strict specifications.

The intermediate boiling hydrocarbon fraction (12) is directed to a hydroisomerization unit (ISOM), in which pseudocumene is converted to mesitylene and olefins are partially hydrogenated, resulting in minimization of loss of octane number and providing an isomerized intermediate boiling hydrocarbon fraction (16). The higher boiling hydrocarbon fraction (14) is directed to a hydrocracking unit (HDC), in which the C10+ hydrocarbons are converted mainly to C8-C9 hydrocarbons by hydrocracking, providing a hydrocracked higher boiling hydrocarbon fraction (18). The hydrocracked higher boiling hydrocarbon fraction (18) is directed to feed the gasoline splitter section (GSS), such that low boiling and intermediate boiling hydrocracked products are directed to the low boiling hydrocarbon fraction (10) and intermediate boiling hydrocarbon fraction (12), whereas the higher boiling hydrocracked products are directed to the higher boiling hydrocarbon fraction (14), and thus recycled to the inlet of the hydrocracking unit (HDC), allowing milder hydrocracking conditions per pass, as any unconverted high boiling hydrocarbons will be recycled. The low boiling hydrocarbon fraction (10), the isomerized intermediate boiling hydrocarbon fraction (16) and the hydrocracked higher boiling hydrocarbon fraction (18) are combined, to provide a synthetic gasoline product (24).

As for Figure 1 , hydrogen is added to the hydrocracking and isomerization units, and the products therefrom are typically stabilized in a separator, by withdrawing light gases but for simplicity this is not shown.

In all embodiments shown, the hydrocracking unit (HDC) contains a material catalytically active in hydrocracking and is operated under hydrocracking conditions. If the material catalytically active in hydrocracking comprises sulfided base metals, a source of sulfur must be present, typically by addition of a sulfur containing hydrocarbon. If the material catalytically active in hydrocracking comprises reduced metals, the fractions of the synthetic gasoline are inherently sulfur-free, and thus, do not require any sulfur removal process. If no recycle is applied, the process may typically be configured for a high hydrocracking conversion of higher boiling hydrocarbon to ensure that the product complies with the relevant requirements, whereas the process may be configured for low or moderate hydrocracking conversion if recycle is applied.

Similarly, the hydroisomerization unit (ISOM), if present, contains a material catalytically active in hydroisomerization and is operated under hydroisomerization conditions. If the material catalytically active in hydroisomerization comprises sulfided base metals, a source of sulfide must be present in the intermediate boiling hydrocarbon fraction, typically by addition of a sulfur containing hydrocarbon. If the material catalytically active in hydroisomerization comprises reduced metals, the process must be designed to remove sulfides from the intermediate boiling hydrocarbon fraction, at least to a level below 50 ppmw, which may be accomplished during the stabilization of the synthetic gasoline in the hydrocracker section (HDC) or in the gasoline splitting section (GSS).

Examples

A process for production of synthetic gasoline via a methanol route was evaluated by experimental testing of stabilized synthetic gasoline having the composition and charac- teristics shown in Table 1. This product is neither in compliance with the strict specifications or intermediate specifications considered, which for the examples are an upper limit for Tgo of 152°C (305°F) and less than 6 vol% olefins after blending with 10% ethanol (which before blending corresponds to 6.6 vol%, or 6 wt% in the synthetic gasoline) in strict specifications and Tgo of 168°C (335°F) and less than 10 vol% olefins after blending with 10% ethanol (which before blending corresponds to 11 vol%, or 10 wt% in the synthetic gasoline) in intermediate specifications.

The examples assume final production of 100 t/h synthetic gasoline.

Example 1

Example 1 is an example according to Figure 2. Here a synthetic gasoline is produced, which in a gasoline splitter is split in a low boiling fraction (C3-C8, boiling below 150°C), an intermediate fraction (C9-C10, boiling between 150°C and 180°C) and a high boiling fraction (C9+, boiling above 180°C). The high boiling fraction is hydrocracked and directed to the gasoline splitter. The intermediate boiling fraction is isomerized and directed to be combined with the low boiling fraction.

By this separation the majority of the synthetic gasoline is directed to the low boiling fraction (80 t/h), with minor volumes in the intermediate fraction (20 t/h) and high boiling fraction (7 t/h), all of which is recycled.

According to this example, the concentration of olefins is 10 wt% and T90 is 168°C, which is in compliance with intermediate specifications but not in compliance with strict specifications.

Example 2

Example 2 is also an example according to the process layout Figure 2 of the present disclosure, but with different fractionation temperatures. Here a synthetic gasoline is produced, which in a gasoline splitter is split in a low boiling fraction (41 t/h, C3-C7, boiling below 90°C), an intermediate fraction (59 t/h, C8-C9, boiling between 90°C and 150°C) and a high boiling fraction (13 t/h, C10+, boiling above 150°C). The high boiling fraction is hydrocracked and directed to the gasoline splitter. The intermediate boiling fraction is isomerized and directed to be combined with the low boiling fraction.

In this example, the volume of the intermediate stream is increased from 22 t/h to 59 t/h, i.e. a factor 2.7 compared to example 1 and the volume directed for hydrocracking is increased from 10 t/h to 14 t/h, i.e. by 40%. To have isomerization conversion similar to Example 1 , similar reaction conditions are required, including reactor space velocity. Therefore, an increase of the isomerization reactor size by a factor 2.7 is necessary for sufficient isomerization. It is not assumed that additional reactor volume or catalyst is required due to the olefin saturation. The volume directed for hydrocracking will also be increased by 40%. In addition, there will be two additional HDC catalyst beds, reactor size must be increased and the volume of make-up hydrogen consumed will be increased, which will add to capital cost as well as operational cost.

According to this example, the concentration of olefins is 6 wt% and T90 is 152°C, which is in compliance with strict specifications.

Example 3

Example 3 is an example according to Figure 1 of the present disclosure. Here a synthetic gasoline is produced, which is split in a low boiling fraction (C3-C8, boiling below 150°C), an intermediate fraction (C9-C10, boiling between 150°C and 180°C) and a high boiling fraction (C9+, boiling above 180°C), in a similar manner as Example 1 (78 t/h, 22 t/h and 10 t/h respectively).

The majority of the synthetic gasoline is directed to the low boiling fraction, with minor volumes in the intermediate fraction and high boiling fraction, and thus the required isomerization is possible with an isomerization reactor of the same size as in Example 1. However, to obtain the appropriate boiling point, hydrocracking is carried out on the isomerized intermediate fraction and hydrogenation is carried out on the full product fraction. The required volumes of the hydrocracking reactor and the isomerization reactor are unchanged in comparison with Example 1 , gas flows will also be unchanged and hydrogen consumption will only increase slightly. Compared to Example 1 and Example 2, Example 3 requires two extra reactors; a post-treat hydrocracking unit and a hydrogenation unit; but the related capital cost is secondary to the cost related to the extra reacting volumes of Example 2.

According to this example, the concentration of olefins is 4 wt% and T90 is 152°C, which is in compliance with strict specifications.

In comparison, of the three examples only Example 2 and Example 3 are in compliance with the strict specification. Example 2 is conceptually similar to Example 1 , and appears simpler, and requires 2 reactors less, and therefore appears the immediate choice.

Example 3 is however able to demonstrate the same performance as Example 2, and although apparently more complex, Example 3 is also less expensive to implement, as the total volume of reacting streams will be lower, and provides the flexibility of producing products adhering to strict or intermediate specifications.

Table 1

Table 2 Table 3 Table 4