FI124194B - Method and apparatus for separating components from fuel feedstock - Google Patents

Description

METHOD AND EQUIPMENT FOR THE SEPARATION OF INGREDIENTS FROM FUEL RAW MATERIAL

Field of the Invention 5

The present invention relates to a method of separating ingredients from a fuel feedstock of the type set forth in the preamble of claim 1. The invention also relates to apparatus of the type set forth in the preamble of claim 9 for carrying out the method.

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Background of the Invention

Naturally occurring raw materials are potential sources of various fuels or fuel components. For example, tall oil, which is a by-product of conifer sulphate soup, has been used as a raw material for hydrocarbon fuel components. U.S. Patent No. 5,705,722 discloses the conversion of unsaturated fatty acids from tall oil to cetane number enhancers in diesel fuels. According to that patent, a tall oil feedstock is fed through a catalytic reactor by simultaneous contact with gaseous hydrogen. The resulting product is removed from the reaction as a single product stream which is further fractionated, whereupon the cetane stream is removed as a middle distillate.

In the aforementioned patent US 5,705,722, all the constituents of the tall oil feed are subjected to a catalytic treatment, and the distillates obtained in the subsequent distillation step are all used as different fuels or fuel additives for different combustion processes.

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o i ° In the above process, tall oil is used as raw material feed, g 30 minus tall oil pitch. According to this publication, tall oil from which

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the pitch is removed by evaporation of crude tall oil, for example, by a thin film evaporator to remove unsaponifiable compounds and m g of ash in tall oil, followed by possibly further distillation steps to remove fatty acids, diterpenoic acids, etc. Small removal (thermal evaporation) reduces the amount of both unsaponifiable compounds and ash in tall oil.

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In addition to fatty acids, crude tall oil contains a number of other ingredients that may be of value for uses other than fuel. The main constituents of crude tall oil are free fatty acids, some of which are saturated-5 unsaturated, resin acids and so-called. pitch containing various sterols. The pitched tall oil used in the process of U.S. Patent No. 5,705,722 still contains about 5 to 20% by weight of unsaponifiable ingredients.

Another process using biological raw materials is described in European Patent No. 1396531, in which raw materials containing fatty acids and / or fatty acid esters, including tall oil, are converted into hydrocarbon components in catalytic hydrodeoxygenation and isomerization steps.

15 Crude tall oil (CTO) is a promising candidate for the production of various fuel components. Prior art solutions use expensive distillation steps to produce tall oil fatty acid fractions from crude tall oil. These fatty acid fractions are then refined, for example, by catalytic HDO (hydrodeoxygenation) and isomerization to the desired fuel components, while losing the fuel potential of the other fractions that are not present.

On the other hand, if all the organic carbon compounds of tall oil are passed through catalytic conversion steps, some of them may have a molecular size and structure that requires additional processing such as cracking to be suitable for low fuel fractions.

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Summary of the Invention o

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It is an object of the invention to use crude tall oil or some other pine oil.

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the various constituents of the oil-based feed by more efficiently preserving the natural form of the constituents, notwithstanding converting its fatty acid constituents into fuel or fuel additives. This object is achieved by a method characterized by the features of the characterizing part of claim 1. The separation step and the hydrodeoxygenation step take place in the same reactor. In the separation step, the light constituents are separated from the heavier constituents of tall oil feed 3 and the heavier constituents form their own fraction which is not led to the hydrogenation step. The apparatus of the invention comprises a hydrogenation reactor which is simultaneously used as a separator for separating the heavier constituents from the feed before being subjected to a hydrogenation treatment.

The heavier constituents in the separated heavier fraction bypassing the hydrogenation treatment remain unchanged in structure, and thus their useful natural structure can be used for many applications. One important group in this verse is sterols, especially β-sitosterol. Under normal hydrogenation treatment of all the components of crude tall oil, this material would be converted into a stigma, which has virtually no value other than as a potential fuel component requiring cracking to be suitable for this purpose.

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Known commercial desulfurization catalysts can be used in the hydrogenation step of the lighter constituents, followed by the optional isomerization step to produce the diesel oil constituents.

Sterol components, such as β-sitosterol, may be separated from the unmodified heavier fraction by extraction or other suitable separation methods. Other possible ingredients can also be separated from this fraction by a suitable method. 1

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings, which schematically illustrates apparatus for carrying out the process of the invention.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS o

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In the present specification and claims, the following terms c \ j have the meanings defined below.

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The term "catalytic HDO" or "catalytic hydrodeoxygenation" refers to the catalytic treatment of the feed with hydrogen under catalytic conditions which results in the following reactions: deprotection by removal of the carboxylic acid with hydrogen by the action of the catalyst, and hydrogenation by hydrogenation of the hydrocarbons the influence. According to a preferred embodiment, the catalytic HDO also has a ring opening feature. The preferred HDO according to the invention also removes unwanted impurities such as sulfur as hydrogen sulfide and nitrogen as ammonia.

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The term "HDO Product" and related terms refer to the products of the above-mentioned catalytic HDO.

The terms' 'decarboxylation' 'and' 'decarbonylation' mean the removal of carboxylic acid as CO 2 (decarboxylation) or CO (decarbonylation) with or without hydrogen.

The term '' isomerization 'refers to the catalytic and hydrogen addition of short-chain (usually methyl) branches to n-paraffinic hydrocarbons.

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The term "cracking" refers to the catalytic decomposition of organic hydrocarbon materials by hydrogen.

The term "n-paraffins" refers to ordinary alkanes or straight chain alkanes that do not contain side chains.

δ ^ The term "isoparaffins" refers to alkanes having one or more C1-C9-,

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o C 1 -C 2 alkyl side chains, usually mono-, di-, tri- or tetramethyl-alkanes.

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The term "crude tall oil" refers to a by-product of the sulphate soup process of wood pulp production. Crude tall oil usually contains both-

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g saturated and unsaturated oxygen-containing organic compounds such as S resins, unsaponifiable compounds, sterols, resin acids (mainly 35 abietic acid and its isomers), fatty acids (mainly linoleic, oleic and linolenic acids), fatty alcohols and other fatty alcohols, impurities (alkali metal (Na, K) compounds, sulfur, silicon, phosphorus, calcium and iron compounds).

The term '' tall oil feed '' refers to tall oil based feed used as a raw material for 5 products and may be crude tall oil or refined crude oil which has various impurities depending on the extent of the purification treatment but contains sterols which have not been purged.

10 The term "separation step" refers to a process in which tall oil feed can be divided into two fractions of different molecular size. Separation of the ingredients takes place according to the boiling points of the ingredients by means of temperature and pressure.

Light constituents are the constituents separated in the separation step and form a light fraction of tall oil feed that is subjected to catalytic HDO. Heavier ingredients refer to ingredients that are separated in the separation step and form a heavier fraction of tall oil feed that overrides catalytic HDO. Without wishing to limit the concepts of light fraction 20 and heavier fraction, and thus light ingredients and heavier ingredients, it can be said that the heavier fraction preferably contains tall oil feed ingredients with more than 21 carbon atoms. Thus, the light fraction contains components with up to 21 carbon atoms, and based on known pine oil components, the light fraction contains components with less than 21 carbon atoms.

The δ ™ apparatus comprises reactor 1, inlet cb o inlet 1b to the bottom of the reactor 1, hydrogen inlet 1b to the bottom of the reactor, output 1c of the HDO product stream 1c connected to the top of the reactor, and gd residual flow outlet 1d connected to the bottom of the reactor.

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The HDO product stream outlet 1c is connected via line 3 to an isomerization reaction 2 comprising a gas stream outlet 2a for the light substances and a fuel product outlet 2b for the diesel fuel components, respectively.

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Reactor 1 is divided into two compartments, a separation compartment S, which forms the lower part of the reactor, and a catalytic HDO compartment H, which forms the upper part of the reactor. Both compartments are within a common pressure-resistant reactor jacket. The catalytic HDO section H contains a catalyst which may be any known catalyst selected according to the conversion process to convert the unsaturated fatty acids in the tall oil feed into useful aliphatic fuel components. The catalyst in the hydrogenation compartment is an HDO catalyst. In the case of tall oil fatty acids, the HDO catalyst catalyzes deoxygenation, whereby the carboxyl-10 groups are removed from oxygen atoms and replaced with hydrogen, referred to as hydrodeoxygenation (HDO). This can be combined with simultaneous decarboxylation and decarbonylation, where the carboxyl group carbon is also removed. These reactions are known and will not be further described.

Preferably, the HDO catalyst is sulfur-resistant, since tall oil feed to the catalytic HDO section H may contain traces of organic sulfur compounds that have not been removed in any previous treatment steps. Known commercial sulfur-20 removal catalysts based on, for example, nickel and / or molybdenum can be used as catalysts for these reactions. The catalyst may be a supported NiMo or CoMo catalyst, for example on an alumina and / or silica support. These catalysts are known and will not be further described.

25 By these reactions unsaturated fatty acids linoleic, oleic? and converting the linolenic acid to octadecane (HDO) or heptadecane (HDO + decarboxylation and / or decarbonylation). Abietic acid, which represents

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o Resin acids, converted to abietane by HDO.

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£ 30 For catalytic HDO compartment H, excess hydrogen is fed to the theoretical

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in relation to hydrogen consumption. The pressure may be 50-100 bar and the temperature g 280 ... 340 ° C.

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S The catalyst used in the catalytic HDO section H preferably also has 35 ring-opening properties, whereby it can function as a combined HDO and ring-opening catalyst. When NiMo or CoMo catalysts mentioned above are used in HDO Division H, no ring compounds originally present in tall oil feed resin acids or corresponding hydrogenated ring compounds (such as the abietan mentioned above) are detected in the product stream. Thus, the catalytic HDO section H is a combined HDO / ring opening section.

5 Native resin acids have an undesirable effect on the boiling point and cloud point of diesel fuel and have a very poor Cetane number. Ren canopy treatment can reduce the melting point and cloud point and improve cetane number.

The tall oil feed is fed through the feed inlet 1a to the separating compartment S, while the gaseous hydrogen is fed through the hydrogen inlet 1b to the separating compartment S, below the feed inlet 1a. The tall oil feed may be crude tall oil feed or refined crude tall oil feed with various impurities removed, depending on the extent of the purification treatment. According to a preferred embodiment, the refined crude tall oil feed contains at least some of the heavier constituents originally present in the crude tall oil, such as sterols or polymers, generally compounds having a boiling point above 350 ° C. These ingredients do not enter the catalytic HDO compartment, but are separated in their original form from the feed and remain in the liquid phase.

In the reactor shown in the drawing, hydrogen inlet 1b is provided at the bottom of reactor 1. The temperature of the separating compartment S is maintained at about 350 ° C. In the separating compartment S, the feed flows upstream of the hydrogen flow, which bubbles up through the feed in the direction of the catalytic HDO compartment H. The difference? a stream of hydrogen gas bubbling through the compartment S facilitates the separation of the components of the light fraction ™. In this way, the light fraction differs from the heavier fraction in the feed-

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which flows to the outlet 1 ° of the residual flow arranged at the bottom of the reactor 1. In the catalytic HDO compartment H, hydrogen flows in the same direction as g 30 light fraction. The light fraction contains light ingredients that contain free fatty acids. The HDO catalyst converts unsaturated fatty acids into g n-paraffins and resin acids into acyclic hydrocarbons, respectively, and

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g the elevated products leave the reactor via the HDO product flow outlet 1c at the top of the reactor 1.

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Preferably, the separation section S has a system that maintains the surface height of the liquid phase constant therein. The light components separated in separation section S enter as gaseous components into HDO section H where they undergo catalytic HDO treatment. In one embodiment, hydrogen passing through HDO compartment H is recycled and catalytic HDO compartment H is operated at a lower pressure than usual. In this way, excess hydrogen may be maintained at a sufficient level for catalytic HDO treatment. If recycled hydrogen is cooled, it can also be used as a coolant for the catalytic HDO compartment H. In this case, hydrogen passes the separation section S, which is maintained at a higher temperature.

Because the components that would produce hydrocarbons having more than 21 atoms in HDO remain in the heavier fraction that is removed from Reactor 1 and cannot undergo HDO treatment, HDO products 15 leaving HDO Division H will have suitable carbon chain lengths to used as fuel components after isomerization and do not require cracking.

The temperature of the separation section S depends on the desired distribution of the various components between the light fraction and the heavier fraction, depending on the boiling points of the components to be separated. A temperature of about 350 ° C is sufficient to isolate important unsaturated fatty acids and resin acids as gaseous constituents from tall oil feedstock as precursors of fuel constituents and to maintain them in the gas phase up to HDO compartment H. The heavier fraction that leaves reactor 1 via residual stream outlet 1d without treatment in the HDO-25 step remains in the liquid phase. Temperature can also be some degrees? above or below the above value.

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o The product stream can be further isomerized in the isomerization reactor 2 to convert the n-paraffins into branched hydrocarbons leaving the g 30 reactor 2 at the bottom of the reactor fuel product outlet 2b

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through. The isomerization reactor 2 contains a non-cracking isomerization catalyst, g, which is capable of converting straight carbon-in-shell backbones of n-paraffins (linear alkanes) to branched backbones of isoparaffins (branched alkanes).

The N-paraffins are moderately isomerized to improve the cold flow properties of the diesel fuel, but the Cetane number does not decrease too much. Isomerisation also depends on whether the diesel fuel is for winter or summer use.

The fuel product stream 5 taken from the product stream 2b of the isomerization reactor 2 fuel can be used as diesel fuel or as a diesel fuel component which increases the fuel cetane number and lowers the cloud point. The fuel product of the Isomerization Reactor 2 is preferably EN 590 grade diesel.

The light substances leaving the isomerization reactor 2 via gas stream outlet 2a contain predominantly hydrogen and hydrogen sulfide, and as a result of decarboxylation and decarbonylation in HDO reactions, carbon monoxide and carbon dioxide.

The isomerization reactor 2 may contain a catalyst known in the art. The isomerization catalyst may contain Pt or Pd and SAPO or ZSM. Examples are Pt / SAPO-11 or Pt / ZSM-23. Hydrogen gas is fed to the bottom of reactor 2 via a line branched from the hydrogen line to reactor 1 (not shown) and flowing countercurrently to the diesel fraction through the catalyst bed 20 in the isomerization reactor 2. In the isomerization reactor 2, the pressure may be 30-100 bar. C.

It is also possible to carry out the catalytic HDO and the catalytic isomerization simultaneously in the HDO compartment H by selecting the catalyst appropriately so that no reactor 2 is needed for the isomerization but only a separation step? to separate light substances (hydrogen, hydrogen sulfide, carbon dioxide and carbon monoxide) from the fuel components in the fuel product stream. Pre-

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signs of double-acting catalysts for such a one-step hydrodeoxygenation / hydroisomerization step are disclosed, for example, in International Publication No. WO 2006/100584 and include the metal component Pt or Pd

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(of which Pt is preferred) and an acidic ingredient having acid functionality in a porous solid support, wherein the preferred acidic ingredient is § SAPO-11.

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The heavier fraction separated in the separation section S of reactor 1 bypasses the catalytic HDO treatment, i.e. it does not undergo the catalytic HDO treatment, and thus many of its constituents retain their original form, for example sterols. The heavier fraction taken through the residual flow outlet 1d can be further processed in a separation step which separates the useful ingredients. For example, β-sitosterol can be separated by extraction from the heavier fraction.

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In addition to the sterols, the heavier fraction separated from the light fraction contains other substances such as polymers and esters. Although β-sitosterol is one example of a valuable substance that can be separated from the heavier fraction, the invention is not limited to the separation of this known substance, but it can recover any other substances that may be useful because they have not gone through HDO processing A.

If crude tall oil is used as the feed for reactor 1, the heavier fraction will also contain non-volatile impurities which are detrimental to the operation of the catalysts, such as metals, phosphorus, and polymer compounds, which must generally be separated in the purification step. Separation section S also acts as a purification section in this case, and no separate pre-treatment of the crude tall oil feed before reactor 1 is required.

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Claims (16)

A process for separating constituents from a fuel feedstock, in which process tall oil feed comprising unsaturated fatty acids, resin acids and controls, is led to a continuous process comprising a catalytic hydrodeoxygenation (HDO) step for converting the unsaturated fatty acids into fuel constituents, which process also comprises a separation step for separating different fractions, characterized in that the separation step and the hydrodeoxygenation step occur in the same reactor, and the separation step in which one of the unsaturated fatty acids and resin acids comprises fraction is separated from the heavier fraction of the feed, occurs prior to the hydrodeoxygenation step, and only the light fraction is led into the hydrodeoxygenation stage and taken out in a HDO product stream, while the heavier fraction is discharged into a residual stream. 15 Process according to claim 1, characterized in that the heavier fraction comprises constituents with more than 21 carbon atoms, including sterols. 3. A process according to claim 1 or 2, characterized in that the separation step and the hydrodeoxygenation step are carried out in successive steps such that in the separation stage the components of the light fraction rise in gaseous state and reach the hydrodeoxygenation stage, and the components of the heavier stage. The fraction streams in the separation stage downstream and is removed in the residual flow from the separation stage. 25 Method according to any of the preceding claims, characterized in that hydrogen is measured in the hydrodeoxygenation step countercurrent to the heavier fraction. o CVJ g 30 Process according to any of the preceding claims, characterized by CL that the FIDO product flow from the hydrodeoxygenation step is led to an isomerization step. m O) o cv Process according to any of claims 1-5, characterized in that the hydrodeoxygenation step also comprises an isomerization step. Method according to any of claims 2-6, characterized in that the sterols comprise β-sitosterol. Method according to claim 7, characterized in that the β-sitosterol is separated from the residual flow by extraction. 9. Device for separating components from a fuel feed comprising: a reactor (1) comprising a hydrodeoxygenation (FIDO) catalyst, an inlet (1a) for the feed to the reactor (1) for feeding tall oil feed into the reactor (1), - at least one inlet (1b) for hydrogen in the reactor (1), - an outlet (1c) for HDO product flow for withdrawing the HDO product flow from the reactor (1), characterized in that the reactor (1) comprises a separation compartment (S) and a hydrodeoxygenation compartment (F1) containing said catalytic converter, and the inlet (1a) of the feed is connected to the separating compartment (S) which is arranged to separate a light fraction comprising unsaturated fatty acids and resin acids from the feed stream heavier fraction, wherein the reactor (1) further comprises a current connection from the separation compartment (S) to the hydrodeoxygenation compartment (F1) to direct the light fraction to the hydrodeoxygenation compartment (FI); and - an outlet (1d) for residual flow from the separating compartment (S), for extracting a residual flow comprising the heavier fraction without flow connection with the hydrodeoxygenation compartment (F1). CO o i An apparatus according to claim 9, characterized in that the heavier fraction ion comprises constituents with more than 21 carbon atoms, including sterols. CL CD Section 11. Device according to claim 9 or 10, characterized in that the separating mg compartment (S) is placed in a common reactor jacket below the ° hydrodeoxygenation compartment (F1), and the light fraction separated in the separating compartment (S) is arranged to rise to the same. the hydrodeoxygenation compartment (F1) in the reactor jacket. Device according to claim 9, 10 or 11, characterized in that it further comprises an isomerization reactor (2) coupled to the outlet (1c) of the HDO product flow from the reactor (1). 5 Device according to any of claims 9-12, characterized in that the catalyst is a Ni- and / or Mo-based desulfurization catalyst. Device according to any of claims 9-13, characterized in that the hydrodeoxygenation compartment (H) contains a catalyst capable of catalyzing hydrodeoxygenation (HDO) of unsaturated fatty acids. Device according to any of claims 9-14, characterized in that the inlet (1c) for hydrogen is arranged below the inlet (1a) for inlet in the separating compartment (S). Device according to claim 15, characterized in that the inlet (1c) for hydrogen is arranged in the bottom of the reactor (1). 't δ c \ j CO o o CM X IX CL CD O m m CD o o CM