WO2013029663A1

WO2013029663A1 - Method for hydroisomerising renewable hydrocarbons

Info

Publication number: WO2013029663A1
Application number: PCT/EP2011/064917
Authority: WO
Inventors: Teemu Lindberg; Jaakko Nousiainen; Heli Laumola; Arto Rissanen
Original assignee: Upm-Kymmene Corporation
Priority date: 2011-08-30
Filing date: 2011-08-30
Publication date: 2013-03-07
Also published as: CA2845750A1

Abstract

The present invention provides a method for producing two or more hydrocarbon compositions from different biological feedstocks, the method comprising the steps of: (i) removing C_1-10 compounds from a first biological feedstock; (ii) mixing the C_1-10 compounds removed in step (i) with a second biological feedstock; (iii) subjecting the first biological feedstock from which the C_1-10 compounds have been removed to hydroprocessing in the presence of a catalyst to produce a first hydrocarbon composition; and (iv) subjecting the mixture obtained in step (ii) to hydroprocessing in the presence of a catalyst to produce a second hydrocarbon composition; wherein the amount of C_1-10 compounds contained in the second biological feedstock prior to step (ii) is greater than the amount of C_1-10 compounds contained in the first biological feedstock prior to step (i). An apparatus for producing the two or more hydrocarbon compositions, use of the hydrocarbon compositions for producing a fuel and a fuel comprising a hydrocarbon composition produced by the above method are also provided.

Description

METHOD FOR HYDROISOMERISING RENEWABLE HYDROCARBONS

Technical Field

The present invention relates to a method and an apparatus for producing a plurality of hydrocarbon compositions from different biological feedstocks. The hydrocarbon compositions can be used to produce a biofuel .

Background of the Invention

Fuels derived from biological matter ("biofuels") are gaining popularity as a more environmentally friendly alternative to conventional fossil fuels. Examples of biofuels include biodiesel, which is typically produced by transesterification of triglycerides contained in vegetable oil (e.g. sunflower oil). Biodiesel can also be derived from animal fats.

Another type of biofuel is renewable (green) diesel, which contains hydrocarbons obtainable by treating a biological feedstock with hydrogen gas in the presence of a catalyst. This "hydroprocessing" chemically alters compounds in the feedstock so they are suitable for use as fuel components; heteroatoms (e.g. sulfur and oxygen) may be removed from feedstock compounds and unsaturated compounds may be hydrogenated. The hydroprocessed composition may be fractionated to separate fuel components according their molecular weights.

A biological feedstock of interest is tall oil, which is a by-product of the well-known kraft process for wood pulp manufacture. Tall oil comprises a significant proportion of resin acids and fatty acids containing C_12^i8 hydrocarbon chains, so is useful for producing diesel components. In this regard, US-A-5705722 discloses a method for producing diesel components by subjecting tall oil to catalytic hydroprocessing and fractionating the resultant composition to isolate components having a high cetane number. The tall oil contains 30-60 wt% of unsaturated fatty acids, 20-50 wt% of diterpenic (resin) acids and 5- 20 wt% of unsaponifiable compounds.

Another by-product of the kraft process is crude turpentine, which predominantly contains unsaturated C₁₀H₁₅ terpenes (e.g. -pinene) . The composition of crude turpentine thus differs substantially from that of tall oil. Crude turpentine also typically contains up to 6 mass% of sulfur, which makes it unsuitable for use in a fuel . WO-A-2011/004065 discloses a method for producing hydrocarbons from crude turpentine by subjecting the crude turpentine to hydrodesulfurisation using hydrogen gas and a catalyst. This process removes sulfur as hydrogen sulfide and converts the terpenes to less reactive hydrocarbons by ring-opening and hydrogenation of the carbon-carbon double bonds. The hydrocarbons are fractionated to produce compositions suitable for inclusion in various fuels (e.g. diesel and gasoline) . Crude turpentine is particularly useful for the production of gasoline components since gasoline requires hydrocarbons having a lower mass (typically C _₁₀ hydrocarbons} than those contained in diesel (typically C₁₀_₂₈ hydrocarbons) . On the other hand, tall oil is primarily used to produce renewable diesel.

Whilst tall oil and similar biological feedstocks predominantly contain relatively heavy compounds as compared to crude turpentine, they may also contain a certain amount of relatively light compounds such as those contained in crude turpentine (e.g. C₁₀ terpenes) . This is often undesirable as regards fuel production by hydroprocessing since the wide range of compounds in the tall oil makes it difficult to optimise hydroprocessing conditions; catalysts used for hydroprocessing tall oil will inevitably cause some cracking of the lighter turpentine components. This produces yet lighter compounds, even gaseous compounds, such as benzene, toluene, methane and propane, benzene being carcinogenic and hence unwanted. In addition, turpentine components hinder certain purification techniques for tall oil such as low-pressure evaporation. Accordingly, the efficiency of tall oil hydroprocessing using known methods is reduced when the tall oil is contaminated with crude turpentine. On the other hand, disposal of these components reduces the overall yield of the process.

It is an object of the present invention to provide a method and an apparatus for efficiently producing hydrocarbons which can be used as fuel components, particularly biocomponents of diesel or gasoline.

Summary of the Invention

A first embodiment of the present invention is a method for producing two or more hydrocarbon compositions from different biological feedstocks, the method comprising the steps of:

(i) removing C₁_₁₀ compounds from a first biological feedstock;

(ii) mixing the C₁„₁₀ compounds removed in step (i) with a second biological feedstock;

(iii) subjecting the first biological feedstock from which the C₁„₁₀ compounds have been removed to hydroprocessing in the presence of a catalyst to produce a first hydrocarbon composition; and

(iv) subjecting the mixture obtained in step (ii) to hydroprocessing in the presence of a catalyst to produce a second hydrocarbon composition;

wherein the amount of C₁_₁₀ compounds contained in the second biological feedstock prior to step (ii) is greater than the amount of C₁_₁₀ compounds contained in the first biological feedstock prior to step (i) .

The above method involves integration of two process streams, one being for the production of the first hydrocarbon composition from the first biological feedstock, and the other being for the production of the second hydrocarbon composition from the second biological feedstock. The integrated feature is the mixing of the C_l_ ₁₀ compounds (hereinafter occasionally referred to as "the light compounds") removed from the first feedstock with the second feedstock, the second feedstock having a higher initial content of C_1^.₁₀ compounds.

The method is advantageous in that it avoids wastage of the C_]_„₁₀ compounds removed from the first feedstock, thereby improving the overall yield as compared to a method in which these light compounds are disposed of (e.g. by burning). In addition, the method improves the efficiency of hydroprocessing since the compositions of t e feedstocks are less varied following steps (i) and (ii) as regards the molecular weights of their components. More particularly, the conditions for hydroprocessing of the first feedstock can be more readily optimised following removal of the light compounds. The light compounds can also be hydroprocessed under improved conditions since they are mixed with the second feedstock, which has a higher content of C₁_₁₀ compounds than the first feedstock. Subsequent steps such as f actionation are also made easier by the removal of the light compounds from the first feedstock.

Step (i) of the method both purifies the first feedstock and provides C₁_₁₀ compounds for incorporation into the second feedstock, which has a higher initial content of such compounds. Therefore, the method is particularly advantageous when the first feedstock contains components of the second feedstock, whether as a contaminant or deliberately. For instance the first feedstock may contain predominantly crude tail oil as well as a certain amount of crude turpentine (crude tall oil produced by kraft pulping inevitably contains some turpentine) , and the second feedstock may be crude turpentine, which may or may not have been previously purified. In this case, turpentine components can be removed from the first feedstock and combined with the second feedstock prior to hydroprocessing . Other contaminants (e.g. metals and water) can be removed from the first feedstock at the same time as the turpentine components.

Accordingly, step (i) can be used to simultaneously purify two or more compositions (e.g. tall oil and crude turpentine) which are mixed together as the first feedstock. C_x_₁₀ compounds (e.g. C_1Q terpenes) constituting pure components of one composition (e.g. crude turpentine) are removed from the first feedstock and mixed with the second feedstock, which has a higher content of these compounds .

The first and second hydrocarbon compositions produced by hydroprocessing can be used as components of a fuel or to produce such components. Since they have different compositions, the first and second hydrocarbon compositions can be used for the production of different types of fuel (e.g. diesel and gasoline) . On the other hand, common components of each composition can be removed (e.g. by distillation) and combined to produce one type of fuel (e.g. diesel) .

Another embodiment of the invention is an apparatus for producing two or more hydrocarbon compositions from different biological feedstocks, the apparatus comprising: a purifier (1) for removing C₁_₁₀ compounds from a first biological feedstock;

a first feedstock inlet conduit (2) connected to the purifier (1) for delivering the first biological feedstock to the purifier (1); a mixing unit (3) for mixing C_x_₁₀ compounds removed from the first biological feedstock with a second biological feedstock;

a second feedstock inlet conduit (4) connected to the mixing unit (3) for delivering the second biological feedstock to the mixing unit (3) ;

a linking conduit (5) connecting the purifier (1) and the mixing unit (3) for transporting Ο_1-10 compounds from the purifier (1) to the mixing unit (3);

a first hydroprocessing reactor (10) connected directly or indirectly to the purifier (1); and

a second hydroprocessing reactor (12) connected directly or indirectly to the mixing unit (3);

wherein the first hydroprocessing reactor (10) is not connected to the purifier (1) via the mixing unit (3) , and the second hydroprocessing reactor (12) is not connected to the mixing unit (3) via the purifier (1) .

The apparatus is advantageous for the reasons mentioned above with respect to the method; that is, the apparatus efficiently produces different hydrocarbon compositions by integrating components of the process streams upstream of the hydroprocessing reactors. Brief Description of the Drawings

Figure 1: A schematic diagram illustrating an apparatus according to the present invention. Detailed Description of the Invention

In the present application, the terms "comprising", "comprise ( s )" , "containing" and "contain (s)" in the context of one or more components (e.g. compounds in a composition) cover the case where the referenced components are the only components as well as the case where other components are present. When a composition is defined as containing a generic compound {e.g. 0_1-10 compounds) in a certain amount, the disclosure of a subset of compounds (e.g. C₅„₁₀ terpenes) falling within the generic class means that the subset of compounds can be present in said amount and other compounds within the generic class but not within the subset may or may not be contained in the composition.

The method of the present invention is described in detail belo .

The method uses first and second biological feedstocks (i.e. feedstocks derived from biological sources) having different compositions to produce first and second hydrocarbon compositions. The first feedstock is not limited, provided that it has a lower initial content of Ci-io compounds (i.e. compounds containing 1-10 carbon atoms) than the second feedstock. The first feedstock may contain no more than 10 mass% or no more than 5 mass% (based on the mass of the feedstock) of C_L-_₁₀ compounds prior to step (i) .

In one embodiment, the first feedstock comprises at least 15 mass%, more suitably at least 25 massl, of C_1?_₁₈ fatty acids (e.g. linoleic acid, oleic acid and linolenic acid) ; at least 15 mass%, more suitably at least 25 mass%, of resin acids (e.g. abietic acid, pimaric acid and isomers thereof); and at least 10 mass% of neutral products (e.g. sterols) based on the mass of the feedstock. This feedstock is suitably tall oil obtainable from kraft pulping of wood, especially coniferous wood. In general, tall oil contains saturated and unsaturated oxygen- containing organic compounds such as resin acids, fatty acids, unsaponifiables, fatty alcohols, sterols and other alkyl hydrocarbon derivatives, as well as inorganic impurities (e.g. alkaline metal compounds, sulfur, silicon, phosphorus, calcium and iron compounds). "Tall oil" also covers soap oil.

The first feedstock may be a mixture of compositions which are purified simultaneously. For instance, the first feedstock may contain a certain amount of crude turpentine or turpentine distillation bottoms/residues from turpentine refining as well as a relatively heavy composition such as tall oil. The turpentine can be purified (e.g. rid of metals) simultaneously with its separation from the heavier composition, and the purified turpentine can be combined with a second feedstock having a similar composition prior to hydroprocessing . No separate purification step is required if the second feedstock is already of sufficient purity.

The kraft method of wood pulping is well known. It involves treating wood (e.g. wood chips) with a mixture of sodium hydroxide and sodium sulfide in order to remove lignin from the wood.

The second biological feedstock is not limited insofar as it has a higher initial content of C₁_₁₀ compounds than the first feedstock. The second feedstock may suitably contain at least 50 mass%, at least 60 mass%, at least 70 mass% or at least 80 mass% (based on the mass of the feedstock) of ^ci-io compounds prior to being mixed with the removed C_l__1Q compounds in step (ii) . That way, the second feedstock has a uniform composition for hydroprocessing , In a particular embodiment, the second feedstock comprises at least 50 mass%, at least 60 mass%, at least 70 mass% or at least 80 mass% (based on the mass of the feedstock) of unsaturated C₅„₁₀ mono- and/or bi-cyclic hydrocarbons (e.g. C₅_₁₀ terpenes or C₁₀Hie terpenes) . An example of such a feedstock is crude turpentine, which is obtainable from wood, particularly from kraft, mechanical, thermomechanical or chemimechanical pulping of wood such as coniferous wood. Crude turpentine is typically composed predominantly of CioHi₆ terpenes such as cc-pinene, β-pinene and Δ-3-carene. Ci₀H_ie terpenes may constitute more than 70 mass%, more than 80 mass% or even more than 90 mass of the crude turpentine.

Turpentine distillation bottoms and/or turpentine distillation residues from turpentine refining can also be used as the second feedstock. These turpentines should be purified before hydroprocessing.

A terpene-containing feedstock can be produced by other means such as processing of citrus fruits. D-limonene is an example of a terpene contained in such a feedstock.

The Ci_₁₀ compounds contained in the second feedstock prior to step (ii) do not have to be the same as the C₁_₁₀ compounds removed from the first feedstock in step (i) . However, it is preferred that the second feedstock initially contains one or more of the C_1^10 compounds removed from the first feedstock in order to minimise variation in the composition of the second feedstock. More preferably, the second feedstock contains at least 50 mass%, at least 60 mass%, at least 70 mass% or at least 80 mass% in total (based on the mass of the feedstock} of the C_1^10 compounds removed from the first feedstock.

As mentioned above, the second feedstock may have a similar composition to a composition contained in the first feedstock. For instance, the first feedstock may be a mixture of tall oil and turpentine, and the second feedstock may be turpentine. In this case, the turpentine in the first feedstock can be purified (e.g. rid of metals) and separated from the tall oil at the same time as the tall oil is purified. The separated and purified turpentine can then be mixed with the second feedstock.

Compounds in the first and second feedstock may contain heteroatoms such as sulfur. Sulfur is not desirable with regards to fuel ingredients but can be useful for maintaining the activity of the catalyst during hydroprocessing . An example of a sulfur-containing feedstock is crude sulfate turpentine (CST) , which is suitably used as the second feedstock. CST can contain up to 6 mass% of sulfur (e.g. in methanethiol ) .

The Ci-i_Q compounds removed from the first biological feedstock can be selected from a range of light compounds. Particular examples are the light compounds described above with respect to the second feedstock. Specifically, the C_1^]0 compounds may comprise unsaturated C „₁₀ mono- and/or bi-cyclic hydrocarbons, more particularly C₅„₁₀ terpenes or C₁₀H₁₆ terpenes . As well as removing hydrocarbons, some of the C₁_₁₀ compounds removed from the first feedstock and combined with the second feedstock may contain heteroatoms. Examples of such compounds include the sulfur-containing compounds methanethiol , dimethyl sulfide and dimethyl disulfide. In a preferred embodiment, at least 80 mass%, at least 90 mass% or at least 95 mass% of the removed C₁_₁₀ compounds are hydrocarbons {e.g. C₅„₁₀ terpenes) . This minimises the amount of heteroatoms to be removed during nydroprocessing of the mixture derived from the second feedstock .

Other compounds may be removed from the first feedstock but not mixed with the second feedstock. In particular, impurities such as metals and water can be removed from the first feedstock. This may take place simultaneously with removal of the C₁_₁₀ compounds in order to improve the efficiency of the process. Water removed from the first feedstock is preferably separated from the C₁„₁₀ compounds prior to mixing the compounds with the second feedstock. This can be performed by decanting or by another conventional method.

The C₁__i0 compounds can be removed from the first biological feedstock using a conventional method. It is though preferred that the C₁_₁₀ compounds are removed by evaporation, which includes distillation and flashing. In one embodiment, the C₁_₁₀ compounds are contained in a gaseous fraction obtained from a first evaporation step. Evaporation of C₁_₁₀ compounds typically occurs at a temperature up to 210°C at 1 bar. Accordingly, the first evaporation step can be performed at a temperature of 50- 200°C and a pressure of 5-100 mbar. As well as the C₁_₁₀ compounds, other light compounds such as water may be removed by evaporation.

The relatively heavy compounds remaining in the first feedstock after removal of the C_2-.₁₀ compounds may be further purified prior to hydroprocessing . In one embodiment, the residue of the first evaporation step is subjected to one or more further evaporation steps to separate compounds to be hydroprocessed from impurities such as metals, lignin and carbohydrates, which remain in the residue. Impurities such as metals deactivate hydroprocessing catalyst.

A second evaporation step can be performed at a temperature of 200-400°C and a pressure of 50 mbar or less so as to effectively separate useful compounds from impurities .

Removal of the Ci_₁₀ compounds and, optionally, other light compounds from the first feedstock in a first evaporation step serves to improve the effectiveness of subsequent evaporation steps. This is because light compounds have a tendency to cause "carry over" of impurities into the vapour at temperatures above their boiling points. Boiling takes place in a controlled manner in subsequent evaporation steps owing to the removal of light compounds in the first evaporation step.

The €_λ__1ΰ compounds in the first feedstock may improve its purification; for instance, turpentine reduces the viscosity of tall oil, which makes it easier to remove water from the mixture. The C^-L_Q compounds removed from the first biological feedstock are mixed with the second biological feedstock in step (ii) of the method. This may be achieved using a conventional mixing means. If necessary, the C₁_₁₀ compounds can be separated from other removed compounds such as water (see above) . Also, if necessary, the second feedstock (e.g. turpentine distillation bottom/residue ) may be purified simultaneously with, before or after mixing with the C₁„₁₀ compounds.

Following the removal and mixing steps, the first feedstock from which the C₁_₁₀ compounds have been removed and the mixture containing the second feedstock are separately hydroprocessed (i.e. reacted with hydrogen) in the presence of a catalyst to produce first and second hydrocarbon compositions. Hydroprocessing chemically alters compounds contained in the feedstocks. Typical reactions include hydrogenat ion of double bonds, deoxygenation (e.g. by decarboxylation), desulfurisation, isomerisation, ring-opening and, in some cases, cracking. For instance, terpenes contained in the feedstocks, particularly the second feedstock, can be converted to non-terpenic acyclic or cyclic hydrocarbons (e.g. 1- isopropyl-4-methylbenzene, l-isopropyl-4- methylcyclohexane, 2 , 6~dimethyloctane ) by hydrogenation of olefinic bonds and ring-opening. This reduces the reactivity of the compounds so they are r use as a fuel component. Bound contaminants such as sulfur can be converted to gaseous compounds (e.g. hydrogen sulfide), which can be removed in a subsequent step.

Hydroprocessing is effected using a catalyst, which can be any catalyst conventionally employed for this process. In one embodiment, the catalyst is a hydrodeoxygenation (HDO) catalyst, which is intended for removal of oxygen but is also capable of removing other heteroatoms such as sulfur and nitrogen from organic compounds. Effective HDO catalysts include those containing a mixture of CoO/NiO and Mo0₃ on a support comprising A1₂0₃, zeolite, zeolite-

Al₂0₃ or Al₂0₃-Si0₂. A mixture of NiO and Mo0₃ on an A1₂0₃ support is particularly effective. An alternative hydroprocessing catalyst is a dewaxing (HDW) catalyst. This type of catalyst is capable of catalysing the same reactions as HDO catalysts. In addition, HDW catalysts can effect isomerisation (e.g. conversion of n-hydrocarbons to iso-hydrocarbons ) and cracking, which decreases the hydrocarbon chain length (e.g. conversion of cymene to toluene). Both isomerisation and cracking can improve cold flow properties. Cracking can also be used to increase the octane number of the composition .

Effective HDW catalysts include those containing NiW on a support comprising A1₂0₃, zeolite, zeolite-Al₂0₃ or A1₂0₃-

Si0₂. An A1₂0₃ support is preferred. In one embodiment, the first feedstock from which the C_]__^10 compounds have been removed is hydroprocessed using an HDW catalyst and the mixture containing the second feedstock is hydroprocessed using an HDO catalyst. This allows for isomerisation and cracking of the relatively heavy compounds contained in the first feedstock as well as removal of heteroatoms, thereby improving the quality of the first hydrocarbon composition as regards its function as a fuel component. The HDW catalyst may be combined with an HDO catalyst for hydroproces sing the first feedstock from which the C_x_₁₀ compounds have been removed. This enhances heteroatom removal. Λ suitable temperature for hydroprocessing the first feedstock from which the C₁_₁₀ compounds have been removed is 150-500°C, preferably 280~450°C, most preferably 350" 420°C. A suitable pressure is 10-250 bar, preferably 30- 130 bar and most preferably 80-110 bar.

The mixture containing the second feedstock is typically hydroprocessed at a temperature of 200-425°C, preferably 275-<325°C and most preferably 350-420°C. The pressure is suitably 10-150 bar, preferably 15-70 bar and most preferably 15-35 bar.

The products of the hydroprocessing reactions are influenced by the feed rate of the feedstocks to the reactors. The weight hourly spatial velocity (WHSV) of the first feedstock from which the C ₀ compounds have been removed can be 0.1-5.0 h^'1, preferably 0.2-0.8 h^"1 and most preferably 0.3-0.7 h^"1. The WHSV of the mixture containing the second feedstock can be 0.5-10.0 h^-1' preferably 0.5- 3.0 h^"1. WHSV is defined as follows:

WHSV (h^-1) = V / m wherein "V" is the feed velocity of the feedstock (g.h^""1) and "m" is the mass of the catalyst (g) .

The hydroprocessing reactors may contain the catalyst (s) in one layer or a plurality of layers. It is also possible to hydroprocess each feedstock in more than one reactor. The first and second compositions produced by hydroprocessing contain hydrocarbons (e.g. n-hydrocarbons , monocyclic hydrocarbons, polycyclic hydrocarbons). The compositions also typically contain small molecules such as hydrogen sulfide, methane and ammonia, which can be removed in subsequent steps. The hydrocarbon compositions are different owing to the differing compositions of the feedstocks; generally, the average molecular weight of the hydrocarbons in the first composition is greater than that of the hydrocarbons in the second composition. In one embodiment, the first hydrocarbon composition contains C₁₀_ ₂₈ hydrocarbons in an amount of at least 80 mass%, at least 85 mass% or at least 90 mass% {based on the mass of the composition) following hydroprocessing. The second hydrocarbon composition suitably contains C4-10 hydrocarbons in an amount of at least 80 mass%, at least 85 mass% or at least 90 mass% based on the mass of the composition. These hydrocarbons are preferably non- terpenic.

The hydrocarbon compositions may be subjected to one or more further steps in order to produce compositions which are suitable for inclusion in a fuel. For instance, various fractions can be separated from the compositions. In one embodiment, the first hydrocarbon composition is distilled to produce a first distilled composition comprising at least 80 mass% of C₄_₁₀ hydrocarbons and a second distilled composition comprising at least 80 mass% of C₁₀_₂₈ hydrocarbons, and the second hydrocarbon composition is distilled to produce a third distilled composition comprising at least 80 mass% of C₄„₁₀ hydrocarbons and a fourth distilled composition comprising at least 80 mass% of C₁₀_₂₈ hydrocarbons. The C₄_₁₀ fractions are suitable for use as gasoline components, whilst the C₁₀_28 fractions are suitable for use as diesel components. The first and third distilled compositions can be combined and stored in the same tank, and the second and fourth distilled compositions can be combined and stored in another tank.

C₄_₁₀ hydrocarbons are generally distilled from the hydrocarbon compositions at temperatures ranging from room temperature to 210°C at 1 bar, whilst C₁₀_₂₈ hydrocarbons are generally distilled from the hydrocarbon compositions at temperatures in the range of 200~380°C at 1 bar. The ratio of the mass of the first distilled hydrocarbon composition to the mass of the second distilled hydrocarbon composition is preferably no more than 50:50, more preferably no more than 40:60 and most preferably no more than 30:70. The ratio of the mass of the third distilled hydrocarbon composition to the mass of the fourth distilled hydrocarbon composition is preferably at least 60:40, more preferably at least 70:30 and most preferably at least 80:20. Another optional step involves passing one or both of the biological feedstocks through one or more guard beds in order to remove hazardous substances such as metal residues. For this, the guard beds can comprise low activity HDW and/or HDO catalysts. Hydrogen can be used as a carrier gas, the temperature of the guard bed system can be 330-425°C and the pressure can vary between 10 and 150 bar, preferably between 15 and 35 bar for turpentine and 65-120 bar for tall oil. The feedstocks are typically passed through guard beds directly after the removal and mixing steps (i) and (ii), i.e. prior to hydroprocessing.

The hydrocarbon compositions can be subjected to one or more flash steps after hydroprocessing in order to remove light gaseous compounds such as hydrogen sulfide, water and hydrogen introduced when passing the feedstock through a guard bed. Hydrogen can subsequently be separated and reused. It is also possible to use heated gases such as gaseous hydrocarbons as an energy source elsewhere in the system, e.g. to heat oil to be used for distillation. More than one flash step is appropriate when the components of the composition have a broad range of masses. This may be the case for the first hydrocarbon composition. A first flash step may be employed to remove sour gases, hydrogen and light hydrocarbons from the first composition, and a second (lower pressure) flash step can then be employed to separate the hydrocarbons from the sour gases and hydrogen.

A stripping or stabilisation step can also be employed for removing sour gases from the hydrocarbon compositions. This may be performed after a flash step.

As already mentioned, the hydrocarbon compositions produced by the method of the invention can be used to produce a biofuel, especially biodiesel and/or biogasoline. In the context of the present invention, "biofuel" means a renewable fuel containing hydrocarbons produced by catalytic hydroprocessing of a biological feedstock. The feedstock may be purified prior to hydroprocessing but is not converted to derivatives at this stage. "Biodiesel" does not mean diesel produced by transesterification of triglycerides in the conventional sense, i.e. biodiesel components produced by the method of the present invention do not contain fatty acid methyl/ethyl esters. However, it is not excluded that a hydrocarbon composition of the present invention is mixed with such transesterifled products to produce diesel fuel. Both the first and second hydrocarbon compositions can be used to produce biodiesel and biogasoline, e.g. by distilling the compositions and combining appropriate fractions. Alternatively, the compositions may be used to produce different biofuels. It is also possible to blend the hydrocarbon compositions or biofuels derived therefrom with fuel components obtained from conventional nonrenewable sources. For instance, biodiesel derived from the first hydrocarbon composition may be blended with petrodiesel .

In a particular embodiment, a fuel is provided which comprises first and third distilled hydrocarbon compositions obtainable by the distillation method described above. This fuel is suitably gasoline. In an alternative embodiment, a fuel is provided which comprises second and fourth distilled hydrocarbon compositions obtainable by the distillation method described above. This fuel is suitably diesel fuel. The apparatus of the present invention is explained in detail below with reference to Figure 1. The apparatus is suitable for performing the method of the present invention described above. The apparatus comprises, as essential components, a purifier (1) for removing C₁_₁₀ compounds from a first biological feedstock, a first feedstock inlet conduit (2) connected to the purifier (1) for delivering the first biological feedstock to the purifier (1) , a mixing unit (3) for mixing C compounds removed from the first biological feedstock with a second biological feedstock, a second feedstock inlet conduit (4) connected to the mixing unit (3) for delivering the second biological feedstock to the mixing unit (3), a linking conduit (5) connecting the purifier (1) and the mixing unit (3) for transporting C₁_₁₀ compounds from the purifier (1) to the mixing unit (3), a first hydroprocessing reactor (10) connected directly or indirectly to the purifier (1) for producing a first hydrocarbon composition from the first biological feedstock from which the C₁__]0 compounds have been removed, and a second hydroprocessing reactor (12) connected directly or indirectly to the mixing unit (3) for producing a second hydrocarbon composition from the mixture of the second biological feedstock and 0_]__₁₀ compounds .

The first hydroprocessing reactor (10) is not connected to the purifier (1) via the mixing unit (3), and the second hydroprocessing reactor (12) is not connected to the mixing unit (3) via the purifier (1) . This means that the hydroprocessing reactors are part of separate process streams. The first hydroprocessing reactor and the mixing unit are downstream of the purifier in separate streams, and the mixing unit separates the second hydroprocessing reactor from the purifier (see Figure 1) . The linking conduit connects the purifier to the mixing unit. This connection is typically direct, but may be via an intermediate unit of some kind, e.g. a water-removal unit and/or a storage tank. The linking conduit can be a standard conduit such as a high-pressure pipe. This is also the case for the other conduits in the apparatus.

The purifier may comprise one or more evaporating units capable of removing C₁_₁₀ compounds to be passed to the mixing unit, heavy compounds (e.g. heavy hydrocarbons) and impurities such as metals from a first biological feedstock. The removed compounds are not passed to the first hydroprocessor ; the impurities remain in the residue. Removal of metals prolongs the lifetime of the catalyst in the first hydroprocessing reactor. Preferably, the purifier comprises two or more evaporation units, more preferably two or three evaporation units, the operation of which is discussed about regarding the method of the present invention.

The mixing unit serves to mix C_±_₁₀ compounds removed from the first biological feedstock. In addition, the mixing unit may include means for purifying (e.g. removing metals) from the mixture. This may be the case when the second feedstock introduced into the mixing unit is contaminated. In an alternative embodiment, a separate purification unit is located upstream or downstream of the mixing unit for purifying the mixture or purifying the second feedstock prior to mixing.

The hydroprocessing reactors may each contain one or more catalysts in order to facilitate hydroprocessing (e.g. removal of heteroatoms, removal of double bonds. isomerisation, cracking) . Examples of the catalyst are disclosed above with respect to the method of the present invention. A catalyst can be arranged in the hydroprocessing reactors in a single layer (bed) or in more than one layer, the layers being separated from one another somehow (e.g. using an inert material such as glass beads or alumina) . Multiple catalyst layers improve the efficiencies of the reactors. In the case that one of the reactors contains more than one type of catalyst, the catalysts may be mixed together in one or more layers. The relative amounts of the catalysts can be adjusted as appropriate. In one embodiment, the first hydroprocessing reactor contains multiple layers which contain both HDW and HDO catalysts. The relative amounts of these catalysts can vary between each layer, e.g. the relative amount of the HDW catalyst increases on moving towards the bottom of the reactor, the feedstock being introduced at the top of the reactor. There is typically at least one layer containing only HDW catalyst.

The apparatus may additionally include a first distillation unit (20) connected downstream of the first hydroprocessing reactor, and a second distillation unit (22) connected downstream of the second hydroprocessing reactor. These units are able to separate components of hydrocarbon compositions produced by the hydroprocessing reactors so that they can be used as fuel components. For instance, each distillation unit may produce a C₄_₁₀ fraction, which is suitable for use as a gasoline component, and a C₁₀_₂₈ fraction, which is suitable for use as a diesel component. Similar fractions produced by the distillation units can be combined and stored in tanks (24, 25) The apparatus can contain further optional components. Examples of such components include guard bed units (6, 8) and flash units (14, 17). As regards the components and operation of these units, reference is made to the discussion of guard beds and flash steps above in the context of the method of the invention. When present in the apparatus depicted in Figure 1, guard bed units (6) and (8) are connected to the purifier and the mixer via conduits (7) and (9) respectively. Conduits (11) and (13) connect the guard bed units to the hydroprocessing reactors. When present, flash units (14) and (17) are connected to the first and second hydroprocessing units via conduits (15) and (18) respectively, and conduits (21) and (23) connect the flash units to the distillation units. Conduits (16) and (19) remove light gases (e.g. hydrogen sulfide and hydrogen) from the flash units.

Claims

1. A method for producing two or more hydrocarbon compositions from different biological feedstocks, the method comprising the steps of:

(i) removing C₁_₁₀ compounds from a first biological feedstock;

(ii) mixing the C₁_₁₀ compounds removed in step (i) with a second biological feedstock;

(iii) subjecting the first biological feedstock from which the C₁_₁₀ compounds have been removed to hydroprocessing in the presence of a catalyst to produce a first hydrocarbon composition; and

wherein the amount of ^_₁₀ compounds contained in the second biological feedstock prior to step (ii) is greater than the amount of C₁_₁₀ compounds contained in the first biological feedstock prior to step (i).

2. A method according to Claim 1, wherein the C₁_₁₀ compounds removed from the first biological feedstock in step (i) comprise unsaturated C_5^10 mono- and/or bi~cyclic hydrocarbons.

3. A method according to Claim 2, wherein the unsaturated 5-10 ^mono~ and/or bi-cyclic hydrocarbons are terpenes. . A method according to any preceding claim, wherein the first biological feedstock comprises at least 15 mass% of C₁₂_ ₁₈ fatty acids, at least 15 mass% of resin acids, and at least 10 mass% of neutral compounds based on the mass of the feedstock .

5. A method according to any preceding claim, wherein the ^ci-io compounds removed from the first biological feedstock in step (i) are contained in the second biological feedstock in an amount prior to step (ii) which is greater than the amount of the compounds contained in the first biological feedstock prior to step ( i } .

6. A method according to any preceding claim, wherein the first biological feedstock comprises no more than 10 massl, based on the mass of the first feedstock, of C₁_₁₀ compounds prior to step (i), and the second biological feedstock comprises at least 50 massl, based on the mass of the second feedstock, of 0_:_₁₀ compounds prior to step (ii) .

7. A method according to any preceding claim, wherein the first and second feedstocks are obtainable from kraft pulping of wood.

8. A method according to any preceding claim, wherein the C_1^l0 compounds are removed from the first biological feedstock by evaporation of the compounds.

9. A method according to any preceding claim, wherein the catalyst used in step (iii) comprises NiW on a support comprising A1₂0₃, zeolite, zeolite~Al₂0₃ or Al₂0₃-Si0₂.

10. A method according to any preceding claim, wherein the catalyst used in step (iv) comprises a mixture of CoO and Mo0₃ or a mixture of NiO and Mo0₃ on a support comprising AI₂0₃, zeolite, zeolite-Al₂0₃ or Al₂0₃-Si0₂.

11. A method according to any preceding claim, wherein the second hydrocarbon composition produced in step (iv) comprises at least 80 mass% of non-terpenic C₄_₁₀ hydrocarbons based on the mass of the composition.

12. A method according to any preceding claim, comprising the further steps of:

(v) distilling the first hydrocarbon composition to produce a first distilled hydrocarbon composition comprising at least 80 massl of C _₁₀ hydrocarbons and a second distilled hydrocarbon composition comprising at least 80 mass% of C₁₀_₂₈ hydrocarbons; and

(vi) distilling the second hydrocarbon composition to produce a third distilled hydrocarbon composition comprising at least 80 mass% of C₄_₁₀ hydrocarbons and a fourth distilled hydrocarbon composition comprising at least 80 mass% of C₁₀_₂g hydrocarbons ;

wherein the hydrocarbon contents are based on the masses of the individual compositions.

13. An apparatus for producing two or more hydrocarbon compositions from different biological feedstocks, the apparatus comprising:

a purifier (1) for removing C₁_₁₀ compounds from a first biological feedstock;

a first feedstock inlet conduit (2) connected to the purifier (1) for delivering the first biological feedstock to the purifier ( 1 } ; a mixing unit (3) for mixing C -^ _Q compounds removed from the first biological feedstock with a second biological feedstock;

a second feedstock inlet conduit (4) connected to the mixing unit (3) for delivering the second biological feedstock to the mixing unit (3);

a linking conduit (5) connecting the purifier (1) and the mixing unit (3) for transporting C _o compounds from the purifier (1) to the mixing unit (3);

a first hydroprocessing reactor {10} connected directly or indirectly to the purifier (1); and

wherein the first hydroprocessing reactor (10) is not connected to the purifier (1) via the mixing unit (3), and the second hydroprocessing reactor (12) is not connected to the mixing unit (3) via the purifier (1) .

14. An apparatus according to Claim 13, wherein the purifier (1) comprises one or more evaporating units.

15. An apparatus according to Claim 13 or Claim 14, wherein the first hydroprocessing reactor (10) contains a catalyst which comprises NiW on a support comprising A1₂0₃, zeolite, zeolite-Al₂0₃ or Al₂0₃-Si0₂.

16. An apparatus according to any of Claims 13-15, wherein the second hydroprocessing reactor (12) contains a catalyst which comprises a mixture of CoO and Mo0₃ or a mixture of NiO and Mo0₃ on a support comprising A1₂0₃, zeolite, zeolite-Al₂0₃ or Al₂0₃-Si0₂.

17. An apparatus according to any of Claims 13-16, further comprising :

a first distillation unit (20) connected downstream of the first hydroprocessing reactor (10); and

a second distillation unit (22) connected downstream of the second hydroprocessing reactor (12).

18. Use of two or more hydrocarbon compositions obtainable by a method according to any of Claims 1-12 for producing a fuel.

19. A fuel comprising one or more hydrocarbon compositions obtainable by a method according to any of Claims 1-12.

20. A fuel according to Claim 19, which comprises first and third distilled hydrocarbon compositions or second and fourth distilled hydrocarbon compositions obtainable by a method according to Claim 12.

21. A fuel according to Claim 19 or Claim 20, which is gasoline or diesel.