Method and apparatus for forming feedstock for cracking

Abstract

The application relates to a method and an apparatus for forming a feedstock for a steam cracking process. Hydrogen gas (4) and a feed (1) comprising at least carbon dioxide are fed to a first reactor (2) in which the feed reacts with the hydrogen to form a synthesis gas (3) comprising at least carbon monoxide, and the synthesis gas is supplied to a second reactor (6) in which the synthesis gas is treated in the presence of a synthesis catalyst to form a hydrocarbon composition (7) comprising at least naphtha range hydrocarbons. Undesired hydrocarbons, unreacted gases and / or water are separated from the hydrocarbon composition (7) and a fraction of the hydrocarbon composition (8) which comprises at least naphtha range hydrocarbons is formed. The fraction of the hydrocarbon composition is treated by a hydrotreatment (10) in which hydrogenation and hydrodeoxygenation reactions are carried out in the presence of at least one hydrotreatment catalyst in one or more reactors for modifying the fraction (8) to form a modified hydrocarbon composition (11), and the feedstock is formed from the modified hydrocarbon composition.

Description

[0001] METHOD AND APPARATUS FOR FORMING FEEDSTOCK FOR CRACKING

[0002] FIELD

[0003] The application relates to a method defined in claim 1 and an apparatus defined in claim 12 for forming a feedstock for a cracking process , preferably for a steam cracking process .

[0004] BACKGROUND

[0005] It is known that steam cracking is the main conversion technology to produce monomers , such as ethylene and propylene , for polypropylene and polyethylene and other chemicals and polymers . Furthermore , butenes and pyrolysis gasoline are produced by steam crackers , and the butenes and pyrolysis gasoline are important intermediates for many chemicals and polymers . Hydrocarbons , e . g . naphtha, can be used as a feed of the steam cracking . Naphtha and light olefins , such as ethylene , propylene and butenes , are among the most important group of petrochemicals that are currently produced mainly from fossil hydrocarbons .

[0006] Further, known from the prior art is to produce hydrocarbons by a Fischer-Tropsch synthesis . The Fischer-Tropsch synthesis requires a mixture of H2 and CO as feed . Further, it is known that carbon dioxide may be converted to carbon monoxide by RWGS ( reverse water gas shift ) reaction . The RWGS reaction is a highly endothermic reaction requiring high reaction temperature . Further, it is known to produce olef ins from the synthesis gas , e . g . with a direct Fischer-Tropsch process or via a methanol-to-olef ins process .

[0007] OBJECTIVE

[0008] An obj ective is to alleviate the disadvantages of the known technology . The obj ective is to disclose a new type of method and apparatus for producing feedstocks from carbon dioxide for the cracking . Further, the obj ective is to disclose a new type of method and apparatus for optimi zing the hydrocarbon feedstock . Further, the obj ective is to improve a combination comprising Fischer-Tropsch synthesis and cracking .

[0009] SUMMARY

[0010] The method and apparatus are characteri zed by what are presented in the claims .

[0011] In the method for forming a feedstock for a cracking process , such as a steam cracking process , a hydrogen based gas and a feed compri sing at least carbon dioxide are fed to a first reactor in which the feed reacts with the hydrogen to form a synthesis gas comprising at least carbon monoxide , and the synthesis gas is suppl ied to a second reactor in which the synthesis gas is treated in the presence of a synthesis catalyst to form a hydrocarbon composition comprising at least naphtha range hydrocarbons . The hydrocarbon composition or a fraction of the hydrocarbon composition is supplied to a hydrotreatment in which two reactions , which are hydrogenation and hydrodeoxygenation reactions , are carried out in the presence of at least one hydrotreatment catalyst for modifying the hydrocarbon composition or its fraction to form a modified hydrocarbon composition, and the feedstock is formed from the modified hydrocarbon composition .

[0012] The apparatus comprises at least one first reactor to which hydrogen based gas and a feed comprising at least carbon dioxide are fed and in which the feed reacts with the hydrogen to form a synthesis gas comprising at least carbon monoxide , and at least one second reactor to which the synthes is gas is supplied and in which the synthesis gas is treated in the presence of a synthesi s catalyst to form a hydrocarbon composi tion comprising at least naphtha range hydrocarbons . Further, the apparatus comprises at least one hydrotreatment device comprising one or more reactors in which the hydrocarbon composition or a fraction of the hydrocarbon composition is treated for carrying out a hydrotreatment comprising hydrogenation and hydrodeoxygenation reactions in the presence of at least one hydrotreatment catalyst and for modifying the hydrocarbon composition or its fraction to form a modif ied hydrocarbon composition .

[0013] DETAILED DESCRIPTION

[0014] In the method for forming a feedstock for a steam cracking process , a hydrogen gas , i . e . hydrogen based gas , and a feed comprising at least carbon dioxide are fed to a first reactor in which the feed reacts with the hydrogen to form a synthesis gas comprising at least carbon monoxide , and the synthesis gas is supplied to a second reactor in which the synthesis gas is treated in the presence of a synthesis catalyst to form a hydrocarbon composition comprising at least naphtha range hydrocarbons . Undesired hydrocarbons , e . g . light and / or heavy hydrocarbons , unreacted gases , e . g . carbon monoxide , carbon dioxide and / or hydrogen, and / or water are separated from the hydrocarbon composition and a fraction of the hydrocarbon composition, preferably comprising at least naphtha range hydrocarbons , is formed . The fraction of the hydrocarbon composition is treated by a hydrotreatment in which two reactions , which are hydrogenation and hydrodeoxygenation reactions , are carried out in the presence of at least one hydrotreatment catalyst in one or more reactors for modifying the fraction to form a modified hydrocarbon composition, and the modified hydrocarbon composition is discharged from the hydrotreatment and the feedstock is formed from the modified hydrocarbon composition . An apparatus for forming a feedstock for a steam cracking process comprises at least one first reactor to which hydrogen gas and a feed comprising at least carbon dioxide are fed and in which the feed reacts with the hydrogen to form a synthesis gas comprising at least carbon monoxide , and at least one second reactor to which the synthesis gas is supplied and in which the synthesis gas is treated in the presence of a synthesis catalyst to form a hydrocarbon composition comprising at least naphtha range hydrocarbons . Further, the apparatus comprises at least one separation device to separate undesired hydrocarbons , unreacted gases and / or water from the hydrocarbon composition and to form a fraction of the hydrocarbon composition which comprises at least naphtha range hydrocarbons . Further, the apparatus comprises at least one hydrotreatment device comprising one or more reactors in which the fraction of the hydrocarbon composition is treated for carrying out a hydrotreatment comprising hydrogenation and hydrodeoxygenation reactions in the presence of at least one hydrotreatment catalyst and for modifying the fraction to form a modified hydrocarbon composition, and at least one outlet for discharging the modified hydrocarbon composition from the hydrotreatment device to form the feedstock from the modified hydrocarbon composition .

[0015] In this context , the hydrogen gas means any hydrogen composition, flow or the like, comprising hydrogen, in a gaseous form. The hydrogen gas may comprise also other components . In one embodiment , the hydrogen gas mainly consists of hydrogen . In one embodiment , the hydrogen gas is manufactured, e . g from water by an electrolysis . In one embodiment , the hydrogen gas is formed from a by-product of the industrial process . In one embodiment , the hydrogen gas from the same hydrogen source is fed to the first reactor and to the hydrotreatment . In one embodiment , the hydrogen gases from the separate hydrogen sources are fed to the first reactor and to the hydrotreatment.

[0016] In this context, the feed means any feed comprising at least carbon dioxide. The feed may comprise also other components, e.g. inert components, hydrocarbons, water, hydrogen and / or other components. The feed can contain one or more components. In one embodiment, the feed mainly consists of carbon dioxide, preferably content of CO2 is over 95 % , such as 95 - 100 % , in the feed. In one embodiment, the feed mainly contains carbon dioxide, and further contains a minor amount of other component (s) , e.g. below 5 % by weight, in one embodiment below 2 % by weight. In one embodiment, the feed comprises at least carbon dioxide, and further hydrocarbon (s) , e.g. light hydrocarbon ( s ) . In one embodiment, the feed may comprise hydrogen. The feed can be formed from any source, e.g. from carbon dioxide emissions, gas of industrial process or other source. In one embodiment, the feed is a flow from a gas recirculation system. In one embodiment, the feed is partially formed from a recirculated gas or a flow of the gas recirculation system. In one embodiment, the feed is a flow from a flue gas system. In one embodiment, the feed is formed from air or air of ventilation system. In one embodiment, the feed is formed by a carbon dioxide capture. In one embodiment, the feed is formed from carbon dioxide based emissions of the industrial process. In one embodiment, the feed is formed from industrial emissions, e.g. biogenic origin emissions, by capturing carbon dioxide. In one embodiment, the carbon dioxide may be purified.

[0017] In this context, the synthesis gas means any gas comprising carbon monoxide. Preferably, the synthesis gas comprises at least carbon monoxide. Further, preferably the synthesis gas comprises hydrogen. The synthesis gas may contain also other components. In one embodiment, the synthesis gas consists of carbon monoxide and hydrogen . In one embodiment , the synthesis gas mainly contains carbon monoxide and hydrogen, and further contains a minor amount of other components , e . g . below 5 % by weight .

[0018] In this context, the hydrocarbon composition means any composition comprising hydrocarbon or hydrocarbons . The hydrocarbon composition contains at least naphtha range hydrocarbons . In one embodiment , the hydrocarbon composition comprises naphtha range paraffinic hydrocarbons .

[0019] The feed is supplied to the first reactor and arranged to contact with the hydrogen, and optionally with the catalyst in the first reactor, and the feed is treated by means a reaction wherein the carbon monoxide and water is formed from the carbon dioxide and hydrogen . Any suitable reaction can be carried out to convert the carbon dioxide to carbon monoxide in the first reactor . The hydrogen can be used as a reactant in the first reactor .

[0020] In one embodiment , the carbon dioxide is treated with the hydrogen to form the synthesis gas comprising carbon monoxide in the first reactor . In one embodiment , the reaction is carried out in the presence of a catalyst . In one embodiment , a reforming reaction is carried out in the first reactor . In one embodiment , a partial oxidation is carried out in the first reactor . In one embodiment , a reverse water gas shift reaction (RWGS ) i s carried out in the first reactor , preferably the RWGS is carried out in the presence of the catalyst . The reverse water gas shift (RWGS ) reaction is an endothermic reaction . In one embodiment , the reverse water gas shift reaction (RWGS ) combined with a catalytic partial oxidation (CPOX) is carried out in the first reactor . In one embodiment , the reverse water gas shift reaction (RWGS ) based on the catalytic partial oxidation (CPOX) is carried out in the first reactor . In one embodiment, the combination of the RWGS and CPOX is carried out in the presence of the catalyst. In one embodiment, a co-electrolysis reaction is carried out in the first reactor. In one embodiment, the co-elec- trodes are used as catalytic elements. In one embodiment, the first reactor comprises a reforming device. In one embodiment, the first reactor comprises a reforming device comprising a partial oxidation. In one embodiment, the first reactor is a reverse water gas shift (RWGS) reactor. In one embodiment, the first reactor is a reverse water gas shift (RWGS) reactor comprising a catalytic partial oxidation (CPOX) . In one embodiment the RWGS reactor is combined with the partial oxidation, such as the CPOX, to provide heat for the endothermic RWGS-reaction . In one embodiment, two reactions, e.g. RWGS and CPOX, are carried out, preferably simultaneously, in the first reactor. In one embodiment, two reaction steps are carried sequentially in the first reactor. In one embodiment, the apparatus comprises at least two first reactors arranged in sequentially. In one embodiment, the apparatus comprises at least two first reactors arranged in parallel with each other. The synthesis gas can be formed in the first reactor. Further, some hydrocarbons, such as light hydrocarbons, may be formed in the first reactor or first step.

[0021] In one embodiment, the catalyst is used in the reverse water gas shift reaction (RWGS) or in the reverse water gas shift reaction (RWGS) combined with the catalytic partial oxidation (CPOX) . In one embodiment, the catalyst is a Rh-based catalyst.

[0022] In one embodiment, the RWGS reaction is carried out at temperature which is 700 - 1000 °C, preferably 750 - 900 °C, in the first reactor.

[0023] In one embodiment, the hydrogen gas is supplied into the first reactor by means of one first hydrogen inlet, or by means of more than one first hydrogen inlets. In one embodiment, the apparatus comprises at least one feed inlet for supplying the feed into the first reactor. The feed inlet may be any suitable inlet known per se, e.g. pipe, port or the like. In one embodiment, the apparatus comprises at least one feeding device. In this context, the feeding device can be any feeding device, equipment or other suitable device. In one embodiment, the feeding device is selected from the group comprising pump, compressor, tube, pipe, other suitable feeding device and their combinations.

[0024] The synthesis gas is supplied to the second reactor and arranged to contact with the catalyst in the second reactor, and the synthesis gas is treated by means a reaction wherein hydrocarbons are formed from the carbon monoxide and hydrogen. The hydrogen can be used as a reactant in the second reactor. Preferably, the carbon monoxide reacts with the hydrogen of the synthesis gas. In one embodiment, additional hydrogen, e.g. hydrogen gas, may be fed to the second reactor.

[0025] In one embodiment, a Fischer-Tropsch reaction (FT) is carried out in the second reactor, preferably in the presence of the synthesis catalyst. The Fischer- Tropsch (FT) reaction is an exothermic reaction. Preferably, the hydrocarbon composition which comprises naphtha range hydrocarbons is formed in the second reaction step, i.e. in the second reactor. The hydrocarbon composition may comprise a mixture of different hydrocarbons, e.g. C5 - C30 hydrocarbons. In one embodiment, the hydrocarbon composition comprises C5 - C22 hydrocarbons. In one embodiment, the hydrocarbon composition comprises at least C5 - C12 hydrocarbons. In one embodiment, the hydrocarbon composition mainly consists of C5 - C12 hydrocarbons. In a preferred embodiment, the hydrocarbon composition is free of oxygen-containing compounds. In one embodiment, the second reactor is a

[0026] Fischer-Tropsch (FT) reactor. In one embodiment, two reaction steps, e.g. two FT reaction steps, are carried sequentially in the second reactor. In one embodiment, the apparatus comprises at least two second reactors arranged in sequentially, and two reaction steps, e.g. two FT reaction steps, are carried sequentially in the reactors. In one embodiment, the apparatus comprises at least two second reactors arranged in parallel with each other, and two reaction steps, e.g. two FT reaction steps, are carried in the parallel reactors.

[0027] In one embodiment, the Fischer-Tropsch reaction is carried out in the presence of the synthesis catalyst which is Co-based catalyst. In one embodiment, the Co-based catalyst can be any Co-based catalyst which is suitable for the FT-reaction. The Co-catalyst with a suitable catalyst carrier / catalyst support, e.g. Co / alumina-catalyst , Co / titanium dioxide -catalyst and Co / silica-catalyst , or other suitable Co-based catalyst or any combination thereof, may be used in the FT-reaction. Alternatively, other Fischer-Tropsch synthesis catalyst may be used in the second reactor.

[0028] In one embodiment, process conditions are optimized during the Fischer-Tropsch (FT) reaction and / or the second reactor for increasing the amount of naphtharange hydrocarbons and / or decreasing an amount of wax component (s) . In one embodiment, the treatment temperature is 100 - 500 °C in the second reactor. In one embodiment, the FT-reaction is carried out at temperature which is 200 - 350 °C, preferably 230 - 330 °C, and more preferably 260 - 300 °C, which is higher than typical temperature in the FT-reaction. In one embodiment, the FT-reaction is operated at pressure of 1 - 50 bar, and in one embodiment 2 - 30 bar in the second reactor. In one embodiment, the FT-reaction is operated at low pressure of 5 - 10 bar.

[0029] The separation after the second reaction or the second reactor can be based on any separation or separation process which is suitable to separate undesired hydrocarbons, unreacted gases and / or water to form the fraction of the hydrocarbon composition. In one embodiment, undesired hydrocarbons which are separated are light and / or heavy hydrocarbons, e.g. C1-C4 and / or C12+, or alternatively C22 +, hydrocarbons. In one embodiment, light hydrocarbons and heavy hydrocarbons are separated. In one embodiment, unreacted gases which are separated are carbon monoxide, carbon dioxide, hydrogen and / or other unreacted gases. Further, other undesired components may be removed during the separation. In one embodiment, undesired components, e.g. accumulated components, purge components, inert components and / or nitrogen, are removed in the separation. In one embodiment, the separation is a distillation. Any suitable separation device may be used in the apparatus. In one embodiment, the separation device is a distillation device. In one embodiment, the fraction of the hydrocarbon composition comprises hydrocarbons which have a final boiling point of max 400 °C, and in one embodiment 380 °C. In one embodiment, the hydrocarbon composition is dis- tillated for naphtha boiling point range to form the fraction of the hydrocarbon composition, where a final boiling point of the fraction is up to 400 °C, i.e. max 400 °C, and in one embodiment 380 °C. In one embodiment, the fraction of the hydrocarbon composition contains over 90 % hydrocarbons which have a final boiling point of max 400 °C. In one embodiment, the fraction comprises C5 - C12 hydrocarbons after the separation.

[0030] In one embodiment, a naphtha fraction is separated from the hydrocarbon composition formed in the Fischer-Tropsch reaction and / or in the second reactor, and the naphtha fraction is supplied to the hydrotreatment. In one embodiment, the separation device is arranged to separate the naphtha fraction from the hydrocarbon composition. In one embodiment, the separation is performed by a distillation. In one embodiment, the separation device is a distillation device. The hydrocarbon composition may be distilled for naphtha boiling point range to form the naphtha fraction, where a final boiling point of the naphtha fraction may be less than 400 °C, in one embodiment about 300 °C, and in one embodiment about 200 °C. The naphtha fraction can be fed to the hydrotreatment device in which the naphtha fraction is treated by the hydrotreatment to form the modified hydrocarbon composition. Further, undesired components, e.g. oxygen-containing compounds, oxygenates, undesired olefins and / or other components, and / or further unreacted gases and / or water, may be removed from the naptha fraction or decreased in the naphtha fraction during the separation, e.g. the distillation. In a preferred embodiment, the naphtha fraction is free of ox- ygen-containing compounds after the separation. In one embodiment, the naphtha fraction comprises C5 - C12 hydrocarbons after the separation.

[0031] In one embodiment, the method further comprises at least one removal step for removing undesired components, e.g. oxygen-containing compounds, oxygenates, undesired olefins and / or other components, from the fraction of the hydrocarbon composition. In one embodiment, the apparatus further comprises at least one separator for removing undesired components from the fraction of the hydrocarbon composition. In a preferred embodiment, the fraction of the hydrocarbon composition is free of oxygen-containing compounds after the removal step. In one embodiment, the removal step is the hydrotreatment .

[0032] In one embodiment, the reactions of the hydrotreatment are carried out at one stage. In one embodiment, the reactions of the hydrotreatment are carried out in one hydrotreatment device. In one embodiment, the reactions of the hydrotreatment are carried out in one reactor at the hydrotreatment stage. In one embodiment, the apparatus comprises one hydrotreatment device. In one embodiment, the hydrotreatment device comprises one reactor, e.g. hydrotreatment reactor or hydrotreater, in which the reactions are carried out. In one embodiment, the hydrotreatment is a two-step hydrotreatment. In one embodiment, the hydrotreatment steps are carried out in the same hydrotreatment device. In one embodiment, the hydrotreatment steps are carried out in two reactors, such as hydrotreatment reactors or hydrotreaters. In one embodiment, the hydrogenation is carried out in a first hydrotreatment reactor and the hydrodeoxygenation is carried out in a second hydrotreatment reactor. In one embodiment, the hydrotreatment device is a two-step hydrotreater in which two reactions, i.e. the hydrogenation and hydrodeoxygenation reactions, are carried out. In one embodiment, the hydrotreatment steps are carried out in at least two hydrotreatment devices.

[0033] In one embodiment, the first and second hydrotreatment steps, such as the hydrogenation and hydrodeoxygenation reactions, are carried out using the same or similar catalyst. Then the hydrotreatments steps may be run in series using two consecutive reactors or two consecutive catalyst beds in the same reactor. In one embodiment, the first and second hydrotreatment steps, such as the hydrogenation and hydrodeoxygenation reactions, are carried out using the different catalysts, e.g. in the separate reactors. In one embodiment, the hydrotreatment is carried out with the hydrotreatment catalyst which is a non-sulfided catalyst or a sulfur- free catalyst, and then the modified hydrocarbon composition is very clean from contaminants. Further, the non-sulfided catalyst is active also at low temperatures of below 200 °C, and thus the same catalyst may be used in the both steps. In one embodiment, the hydrotreatment is carried out with the hydrotreatment catalyst which is a noble metal based catalyst. In one embodiment, the hydrotreatment is carried out with the hydrotreatment catalyst which is selected from the group consisting of a noble metal based catalyst, noble metal based alumina catalyst, Pt / alumina catalyst, Ni / alumina catalyst, Rh / alumina catalyst, or any combination thereof. In one embodiment, the noble metal based catalyst can be any catalyst which comprises noble metal and which is suitable for the hydrotreatment reaction. The noble metal based catalyst can comprise a suitable catalyst car- rier / catalyst support, e.g. alumina, titanium dioxide, silica or other suitable carrier, or any combination thereof. In one embodiment, the noble metal based catalyst comprises a gamma alumina as the catalyst support. The gamma alumina has rather high Na2<3 content, which is known to reduce the acidity of the alumina. As no isomerization and low catalytic cracking are preferred, it is advantageous to use the catalyst support material with relatively low acidity.

[0034] In one embodiment, the hydrogen gas is fed to the hydrotreatment, such as to the hydrotreatment reaction or the hydrotreatment device, e.g. to both hydrotreatment reactions or alternatively to one of the hydrotreatment reactions. In one embodiment, the hydrogen gas is supplied into the hydrotreatment device or the reactor (s) by means of one second hydrogen inlet, or by means of more than one second hydrogen inlets.

[0035] In one embodiment, the hydrogenation is carried out at temperature of 130 - 200 °C, preferably 140 - 190 °C, and more preferably 150 - 180 °C. In one embodiment, the hydrodeoxygenation is carried out at temperature of 280 - 380 °C, preferably 300 - 360 °C, and more preferably 320 - 340 °C.

[0036] Preferably, olefins are hydrogenated in the hydrogenation reaction, i.e. in the hydrogenation step of the hydrotreatment. Preferably, the hydrodeoxygenation of oxygenates present in the hydrocarbon composition is performed by the hydrodeoxygenation reaction, i.e. in the hydrodeoxygenation step of the hydrotreatment.

[0037] The apparatus comprises at least one outlet, alternatively more than one outlets, for discharging the modified hydrocarbon composition out from the hydrotreatment device. The outlet may be any suitable outlet known per se, e.g. pipe, outlet port or the like.

[0038] The modified hydrocarbon composition comprises at least naphtha range hydrocarbons, e.g. C5 - C22 hydrocarbons or C5 - C12 hydrocarbons. The modified hydrocarbon composition may be formed from the fraction of the hydrocarbon composition or the naphtha fraction, e.g. as described above. In one embodiment, the modified hydrocarbon composition comprises C5 - C22 hydrocarbons. In one embodiment, the modified hydrocarbon composition comprises C5 - C12 hydrocarbons. In one embodiment, the modified hydrocarbon composition comprises paraffins, such as linear, branched and / or cyclic paraffins. In one embodiment, the modified hydrocarbon composition is a mixture of hydrocarbons. Further, the modified hydrocarbon composition may comprise other components, e.g. different hydrocarbons, carbon monoxide, hydrogen and / or other components, preferably a minor amount of other components. In one embodiment, the modified hydrocarbon composition comprises paraffins with a carbon number of C5 - C12. In one embodiment, the modified hydrocarbon composition consists of paraffins with a carbon number of C5 - C12. In a preferred embodiment, the modified hydrocarbon composition is free of oxygencontaining compounds. In one embodiment, the modified hydrocarbon composition is in the form of liquid.

[0039] In one embodiment, the modified hydrocarbon composition can be further treated, using a further treatment, after the hydrotreatment and before the steam cracking. In one embodiment, the modified hydrocarbon composition can be supplied to a desired treatment step or device, e.g. to a filtration for filtrating the modified hydrocarbon composition, or to an adsorption column for removing oxygen or other undesired components from the modified hydrocarbon composition, or to a distillation, such as a second distillation, for separating desired components or fractions, or to a water cooling for removing undesired components from the modified hydrocarbon composition. In one embodiment undesired components, impurities and / or non-condensable components, e.g. methane, C2 - C4 hydrocarbons, unreacted gases, and / or other undesired compounds, may be discharged or separated from the modified hydrocarbon composition in the further treatment before the steam cracking.

[0040] In one embodiment, depending on the amount of oxygenates and olefins, a further treatment or a further upgrading step of the hydrotreatment or a further treatment after the hydrotreatment is carried out to reduce coking in the steam cracking. However, it is important that possible fast polymerization of diolefins, if present, can be avoided, and thus blocking the devices can be avoided.

[0041] The feedstock is formed from the modified hydrocarbon composition. In one embodiment, the feedstock is formed from the modified hydrocarbon composition formed in the hydrotreatment, such as in the hydrotreatment device. In one embodiment, the feedstock is formed from the modified hydrocarbon composition, which is treated after the hydrotreatment, e.g. by the filtration, distillation, adsorption, water cooling or other treatment. In one embodiment, the feedstock comprises paraffins with a carbon number of C5 - C12. The feedstock may be fed to the steam cracking, e.g. to a cracker or cracking furnace, directly or via an intermediate tank. In one embodiment, the method further comprises recirculating at least one undesired compound and / or fraction from the hydrocarbon composition and / or modified hydrocarbon composition to the feed. In one embodiment, undesired compound and / or fraction from the hydrocarbon composition comprise the undesired hydrocarbons, which are separated in the separation or separation device after the second reactor, such as light and / or heavy hydrocarbons, e.g. C1-C4 and / or C12+ or C22+ hydrocarbons. The undesired compound and / or fraction may comprise undesired hydrocarbons, undesired FT products, e.g. methane, unreacted gases, e.g. CO, CO2 and / or hydrogen, and / or other undesired compounds. In one embodiment, the undesired compound and / or fraction is recirculated from the second reactor to the feed. In one embodiment, the undesired compound and / or fraction is recirculated from the separation step or the separation device, e.g. from the distillation, to the feed. In one embodiment, the undesired compound and / or fraction is recirculated from the hydrotreatment step or the hydrotreatment device to the feed. In one embodiment, the undesired compound and / or fraction is recirculated from the further treatment, arranged after the hydrotreatment, to the feed. In one embodiment, undesired compound and / or fraction from the modified hydrocarbon composition comprise undesired components, impurities and / or non-condensable components, e.g. undesired hydrocarbons, methane, unreacted gases and / or other undesired compounds. In one embodiment, the apparatus further comprises at least one recirculating device for recirculating at least one undesired compound and / or fraction from the hydrocarbon composition and / or modified hydrocarbon composition to the feed. In one embodiment, the undesired compound and / or fraction from the hydrocarbon composition and / or modified hydrocarbon composition is recirculated to the feed in the process where the first reactor comprises a reforming device, e.g. comprising a partial oxidation, a catalytic partial oxidation (CPOX) or other reforming. In one embodiment, the undesired compound and / or fraction from the hydrocarbon composition and / or modified hydrocarbon composition is recirculated to the feed in the process, where the first reactor comprises a reverse water gas shift (RWGS) reactor comprising a catalytic partial oxidation (CPOX) . Further, the efficiency of the process, e.g. conversion of carbon dioxide, can be improved when RWGS reaction equilibrium is shifted by the circulation of unreacted gases.

[0042] In one embodiment, the hydrogen gas is formed by an electrolysis. The hydrogen may be formed from water by the electrolysis. In one embodiment, the hydrogen gas is formed using electricity formed by renewable energy, e.g. by a solar energy / power, a wind energy / power and / or other renewable energy, i.e. green electricity. Then the green hydrogen can be used in the process. In one embodiment, the apparatus further comprises at least one electrolyzer for forming the hydrogen gas.

[0043] In one embodiment, the method is based on a continuous process. In one embodiment, the apparatus is a continuous apparatus.

[0044] The modified hydrocarbon composition can be used as the feedstock to the steam cracking. In one embodiment, the method and the apparatus can be used in naphtha production processes, different cracking processes comprising steam cracking, olefin manufacturing processes, manufacturing of fuels, or other suitable processes, or any combination thereof.

[0045] Thanks to the invention feedstock for the steam cracking process can be produced easily and effectively from carbon dioxide based starting materials. Naphtha based feedstock can be formed from carbon dioxide, e.g. biogenic origin CO2. Further, green hydrogen can be used in the process to form hydrocarbons. The high quality feedstock can be produced with low contaminants , low olefins and low oxygenates .

[0046] The method and apparatus offer a possibility to form the feedstock for the steam cracking with good properties easily, and energy- and cost-effectively . The present invention provides an industrially applicable , simple and affordable way to produce the feedstock, and further simultaneously to treat carbon dioxide . The method and apparatus are easy and simple to real i ze in connection with production processes .

[0047] Further, when using emission-based CO2 as a starting material in the process , monomers and polypropylene and polyethylene can be produced more sustainably . Moreover, if the captured CO2 emission is of biogenic origin, the produced monomers can be considered carbon neutral , and in some cases even carbon negative .

[0048] BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings , which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate some embodiments of the invention and together with the description help to explain the principles of the invention . In the drawings :

[0050] Fig . 1 is a flow chart i llustration of a process according to one embodiment ,

[0051] Fig . 2 is a flow chart i llustration of a process according to another embodiment , and

[0052] Fig . 3a and 3b show test results .

[0053] EXAMPLES

[0054] In the process , carbon dioxide is converted to carbon monoxide based synthesis gas which is treated in the Fischer-Tropsch synthesis to form hydrocarbons , i . e . a hydrocarbon composition . The hydrocarbon composition is treated by a hydrotreatment to form a modified hydrocarbon composition. The modified hydrocarbon composition can be fed to a steam cracking directly or via an intermediate tank and / or via an additional treatment.

[0055] Fig. 1 presents one example of the process. Fig. 2 presents another example of the process. Figs. 1 and 2 present the process for producing the feedstock for the steam cracking.

[0056] In Figs. 1 and 2 a hydrogen gas (4,4a) consisting of hydrogen and a feed (1) comprising at least carbon dioxide are fed to a first reactor (2) in which the feed reacts with the hydrogen to form a synthesis gas (3) comprising at least carbon monoxide. The first reactor (2) is a reverse water gas shift (RWGS) reactor comprising a catalytic partial oxidation (CPOX) . The synthesis gas (3) is supplied to a second reactor (6) in which the synthesis gas is treated in the presence of a synthesis catalyst, which is a Co-based catalyst, to form a hydrocarbon composition (7) comprising at least naphtha range hydrocarbons. The second reactor (6) is a Fischer-Tropsch (FT) reactor. The Fischer-Tropsch reaction may be carried out at temperature of 230 - 330 °C in the second reactor. In the second reactor, carbon monoxide reacts with hydrogen, preferably with hydrogen of the synthesis gas, to form the hydrocarbons. According to one example, the hydrocarbon composition comprises at least C5 - C22 hydrocarbons.

[0057] Further, the process comprises a separation device (9) , e.g. a distillation device, for separating undesired light hydrocarbons (15) , e.g. C1-C4, and optionally heavy hydrocarbons, unreacted gases and / or water (16) from the hydrocarbon composition (7) and forming a fraction of the hydrocarbon composition (8) which comprises at least naphtha range hydrocarbons. Preferably, the fraction (8) is the naphtha fraction (8) .

[0058] The fraction (8) , i.e. the naphtha fraction, of the hydrocarbon composition is supplied to a hydrotreatment device (10) in which hydrogenation and hydrodeoxygenation reactions are performed sequentially. The hydrotreatment device comprises two reactors or two catalyst beds (lOa-lOb) in which the reactions are carried out in the presence of the hydrotreatment catalyst, e.g. a noble metal based catalyst or noble metal based alumina catalyst, for modifying the fraction (8) to form a modified hydrocarbon composition (11) . The hydrotreatment device may be a two-step hydrotreater. According to one example, the same hydrotreatment catalyst is used in both reactions. Temperature is lower in the hydrogenation, e.g. 130 - 200 °C, and higher in the hydrodeoxygenation, e.g. 280 - 380 °C. Hydrogen gas (4,4b) may be fed to the hydrotreatment (10a, 10b) , e.g. to both reactions or reactors, or alternatively to one of the reactions or reactors. The same hydrogen gas (4) , supplied to the first reactor, may be fed to the hydrotreatment device. The modified hydrocarbon composition (11) is discharged via at least one outlet from the hydrotreatment device (10) . The feedstock for the steam cracking (13) is formed from the modified hydrocarbon composition. According to one example, the modified hydrocarbon composition comprises C5 - C22 hydrocarbons. According to another example, the modified hydrocarbon composition comprises C5 - C12 hydrocarbons, preferably if the naphtha fraction is treated by the hydrotreament .

[0059] The hydrogen gas (4) may be formed from water by an electrolysis in an electrolyzer (5) . The hydrogen gas may be formed using electricity formed by renewable energy (17) , e.g. a solar energy and / or a wind energy. The hydrogen gas (4) is fed to the first reactor (2) , and optionally also to the hydrotreatment device (10) .

[0060] Optionally, according to Fig. 2, the process may comprise a further treatment (12) , e.g. a filtration, an adsorption column, a distillation, a water cooling or other separation, after the hydrotreatment (10) and before the steam cracking (13) . In the further treatment, the modified hydrocarbon composition (11) can be treated for removing undesired components, impurities and / or non-condensable components, e.g. undesired hydrocarbons, methane, unreacted gases and / or other undesired compounds, and optionally oxygen from the modified hydrocarbon composition (11) . Further, the process may comprise a recirculating device for recirculating the undesired hydrocarbons (15) from the hydrocarbon composition (7) and / or the undesired components, impurities and / or non-condensable components (14) from the modified hydrocarbon composition (11) to the feed (1) . Further, according to one example, the unreacted gases can be recirculated from the separation device (9) to the first reactor (2) , e.g. with the undesired hydrocarbons. Then less-valuable product components can be used to form heat, preferably by the CPOX reaction, and further the most of carbon dioxide can be converted into products.

[0061] Example 1

[0062] In this example, carbon dioxide is converted with hydrogen to carbon monoxide by the RWGS-reaction, and the carbon monoxide is treated with hydrogen by the Fischer-Tropsch (FT) -synthesis to form hydrocarbons. The carbon dioxide may be captured from industrial emissions, e.g. biogenic emissions or other emissions. Green hydrogen formed by renewable energy may be used as the hydrogen .

[0063] The FT-synthesis is operated at low pressure of 5 - 10 bar and higher than typical temperature, i.e. at temperature of 260 - 300 °C, in the presence of Cobased catalyst. Through these operating conditions, the hydrocarbon distribution alpha-value is optimized for the production of suitable hydrocarbon range. The hydrocarbon composition comprising naphtha range paraffinic hydrocarbons is produced in the FT-synthesis. Preferably, the hydrocarbon composition is distilled for full-range naphtha boiling point range to form a naphtha fraction. According to one example, the final boiling point of the naphtha fraction was 212 °C with 95 wt-% boiling below 201 °C, and about 51 wt-% could be distilled to the naphtha fraction. The naptha fraction comprises mainly C5 - C12 hydrocarbons.

[0064] The hydrocarbon composition or the naphtha fraction is supplied to a two-step hydrotreatment device, where olefins are hydrogenated in the hydrogenation step at lower temperature, preferably at 150 - 180 °C, and hydrodeoxygenation of oxygenates is performed at a higher temperature, preferably at 300 - 360 °C. The hydrotreatment, preferably its both steps, may be performed in the presence of a noble metal based, e.g. Ptbased, gamma alumina catalyst. The liquid modified hydrocarbon composition is produced in the hydrotreatment.

[0065] The modified hydrocarbon composition can be fed as the feedstock to the steam cracking, such as to a steam cracker furnace section, e.g. together with steam.

[0066] Example 2

[0067] In this example, the hydrotreatment was performed in two steps in the presence of Pt-based gamma alumina catalyst. The first hydrotreatment, i.e. hydrogenation, was performed at low temperature of about 160 °C to saturate the olefins without a risk of diolefin polymerization, and the later hydrotreatment at the higher temperature of 320 - 340 °C to perform hydrodeoxygenation .

[0068] The hydrocarbon composition, used in this example, was formed in the Fischer-Tropsch synthesis according to Example 1 and comprised hydrocarbons up to C22. The naphtha fraction, used in this example, was distilled from the hydrocarbon composition, and the final boiling point of the naphtha fraction was 212 °C with 95 wt-% boiling below 201 °C, and about 51 wt-% of the hydrocarbon composition could be distilled to the naphtha fraction.

[0069] It was observed that the first hydrotreatment, i.e. hydrogenation, at low temperature reduced the ole- finicity of the hydrocarbon composition from 15 wt-% to 0.4 wt-% (by GC-FID analysis) and from 15000 mg / ml to 40.4 mg / ml (by Br-index) . However, the oxygenates were barely impacted at all. After the second hydrotreatment, i.e. hydrodeoxygenation, at high temperature, the oxygenates were reduced from 5.9 wt-% to 1.1 wt-% (by GC- FID) , which translates to less than 100 ppm oxygen in the final composition, i.e. the modified hydrocarbon composition. Similarly, the olefinicity of the naptha fraction was reduced from 16.9 wt-% to 0.5 wt-% (by GC- FID analysis) and from 28000 mg / ml to 4.3 mg / ml (by Br- index) in the the first hydrotreatment, i.e. hydrogenation. After the second hydrotreatment, i.e. hydrodeoxygenation, the oxygenates were reduced from 6.0 wt-% to 1.2 wt-% (by GC-FID) . The sulfur contents of both final compositions were below the detection limit (< 0.3 ppm) .

[0070] Further, no isomerization was observed, which is preferred as isoparaffins are related to coking in the steam cracker. As no methane or ethane were detected from the gas phases, thermal cracking can be avoided.

[0071] Example 3

[0072] In this example, mass fractions of the hydrocarbon composition (feed) and the modified hydrocarbon composition (product) were compared. The hydrocarbon composition was formed by the Fischer-Tropsch reaction, and the modified hydrocarbon composition was formed from the hydrocarbon composition which was further treated by the hydrotreatment. The hydrocarbon composition and the modified hydrocarbon composition were formed according to Example 2. The test results are presented in Figs. 3a and 3b.

[0073] It was observed that the product, i.e. the modified hydrocarbon composition, mainly consists of alkanes and contains only a minor amount of olefins, and thus it is a high quality feedstock for the steam cracking .

[0074] The devices of the process, e.g. reverse water gas shift and catalytic partial oxidation devices, Fischer-Tropsch reactors, hydrotreatment devices, separating devices, distillation devices, feeding and outlet devices, and recirculating devices of the process, used in these examples are known per se in the art, and therefore they are not described in any more detail in this context.

[0075] The method and apparatus are suitable in different embodiments for forming hydrocarbons and hydrocarbon feedstocks from different kinds of carbon dioxide based starting materials.

[0076] The invention is not limited merely to the examples referred to above; instead many variations are possible within the scope of the inventive idea defined by the claims.

Claims

CLAIMS1. A method for forming a feedstock for a steam cracking process, c h a r a c t e r i z e d in that the method comprises- feeding hydrogen gas (4) and a feed (1) comprising at least carbon dioxide to a first reactor (2) in which the feed reacts with the hydrogen to form a synthesis gas (3) comprising at least carbon monoxide,- supplying the synthesis gas to a second reactor (6) in which the synthesis gas is treated in the presence of a synthesis catalyst to form a hydrocarbon composition (7) comprising at least naphtha range hydrocarbons ,- separating undesired hydrocarbons, unreacted gases and / or water from the hydrocarbon composition (7) and forming a fraction of the hydrocarbon composition (8) which comprises at least naphtha range hydrocarbons ,- treating the fraction of the hydrocarbon composition by a hydrotreatment (10) in which two reactions, which are hydrogenation and hydrodeoxygenation reactions, are carried out in the presence of at least one hydrotreatment catalyst in one or more reactors for modifying the fraction to form a modified hydrocarbon composition (11) , and- discharging the modified hydrocarbon composition (11) from the hydrotreatment and forming the feedstock from the modified hydrocarbon composition.

2. The method according to claim 1, c h a r a c t e r i z e d in that a reverse water gas shift reaction (RWGS) combined with a catalytic partial oxidation (CPOX) is carried out in the first reactor (2) .

3. The method according to claim 1 or 2, c h a r a c t e r i z e d in that a Fischer-Tropsch reaction (FT) is carried out in the second reactor (6) .

4. The method according to claim 3, c h a r a c t e r i z e d in that the Fischer-Tropsch reaction is carried out in the presence of the synthesis catalyst which is Co-based catalyst.

5. The method according to any one of claims 1 to 4, c h a r a c t e r i z e d in that the hydrotreatment (10) is carried out with the hydrotreatment catalyst which is selected from the group consisting of noble metal based catalyst, noble metal based alumina catalyst, Pt / alumina catalyst, Ni / alumina catalyst, Rh / alu- mina catalyst, or any combination thereof.

6. The method according to any one of claims 1 to 5, c h a r a c t e r i z e d in that the hydrogenation is carried out at temperature of 130 - 200 °C.

7. The method according to any one of claims l to 6, c h a r a c t e r i z e d in that the hydrodeoxygenation is carried out at temperature of 280 - 380 °C.

8. The method according to any one of claims 1 to 7, c h a r a c t e r i z e d in that a naphtha fraction (8) is separated from the hydrocarbon composition (7) , and the naphtha fraction is supplied to the hydrotreatment (10) .

9. The method according to any one of claims 1 to 8, c h a r a c t e r i z e d in that the method further comprises recirculating at least one undesired compound and / or fraction from the hydrocarbon composition (7) and / or modified hydrocarbon composition (11) to the feed (1) •10. The method according to any one of claims 1 to 9, c h a r a c t e r i z e d in that the fraction of the hydrocarbon composition (8) comprises hydrocarbons which have a final boiling point of max 400 °C.

11. The method according to any one of claims 1 to 10, c h a r a c t e r i z e d in that the hydrogen gas (4) is formed by an electrolysis (5) .

12. An apparatus for forming a feedstock for a steam cracking process, c h a r a c t e r i z e d in that the apparatus comprises- at least one first reactor (2) to which hydrogen gas (4) and a feed (1) comprising at least carbon dioxide are fed and in which the feed reacts with the hydrogen to form a synthesis gas (3) comprising at least carbon monoxide,- at least one second reactor (6) to which the synthesis gas is supplied and in which the synthesis gas is treated in the presence of a synthesis catalyst to form a hydrocarbon composition (7) comprising at least naphtha range hydrocarbons,- at least one separation device (9) to separate undesired hydrocarbons, unreacted gases and / or water from the hydrocarbon composition (7) and to form a fraction of the hydrocarbon composition (8) which comprises at least naphtha range hydrocarbons,- at least one hydrotreatment device (10) comprising one or more reactors in which the fraction of the hydrocarbon composition is treated for carrying out a hydrotreatment comprising hydrogenation and hydrodeoxygenation reactions in the presence of at least one hydrotreatment catalyst and for modifying the fraction to form a modified hydrocarbon composition (11) , and- at least one outlet for discharging the modified hydrocarbon composition (11) from the hydrotreatment device to form the feedstock from the modified hydrocarbon composition.

13. The apparatus according to claim 12, c h a r a c t e r i z e d in that the hydrotreatment device (10) is a two-step hydrotreater in which two reactions, which are hydrogenation and hydrodeoxygenation reactions, are carried out.

14. The apparatus according to claim 12 or 13, c h a r a c t e r i z e d in that the first reactor (2) is a reverse water gas shift (RWGS) reactor comprising a catalytic partial oxidation (CPOX) .

15. The apparatus according to any one of claims 12 to 14, c h a r a c t e r i z e d in that the second reactor (6) is a Fischer-Tropsch (FT) reactor.

16. The apparatus according to any one of claims 12 to 15, c h a r a c t e r i z e d in that the separation device (9) is arranged to separate a naphtha fraction (8) from the hydrocarbon composition (7) .

17. The apparatus according to any one of claims 12 to 16, c h a r a c t e r i z e d in that the apparatus further comprises at least one recirculating device for recirculating at least one undesired compound or fraction from the hydrocarbon composition (7) and / or modified hydrocarbon composition (11) to the feed (1) .

18. The apparatus according to any one of claims 12 to 17, c h a r a c t e r i z e d in that the apparatus further comprises at least one electrolyzer (5) for forming the hydrogen gas (4) .

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