EA013754B1 - Process for the manufacture of diesel range hydrocarbons - Google Patents

Abstract

The invention relates to a process for the manufacture of diesel range hydro- carbons wherein a feed comprising fresh feed is hydrotreated in a hydrotreating step and isomerised in an isomerisation step and the fresh feed contains at least 20 % by weight triglyceride C

Description

FIELD OF THE INVENTION

The invention relates to an improved method for the production of hydrocarbons fractions of diesel fuel from oils and fats of biological origin with reduced consumption of hydrogen. In particular, the invention relates to an improved method for producing hydrocarbons of a diesel fraction with high selectivity, and this method provides a product with improved cold flow properties, while at the same time without reducing the yield of the diesel fraction in the isomerization process.

The scope of the invention

Environmental interests and the growing demand for diesel fuel, especially in Europe, are stimulating fuel producers to make more intensive use of available renewable sources. In the production of diesel fuel based on biological raw materials, the main interest has focused on vegetable oils and animal fats, including triglycerides of fatty acids. Long, linear and mostly saturated hydrocarbon chains of fatty acids chemically correspond to the hydrocarbons present in diesel fuels. However, vegetable oils in their natural form exhibit worse properties, especially excessive viscosity and poor stability, and therefore their use in motor fuels is limited.

Conventional approaches to converting vegetable oils or other derivatives of fatty acids to liquid fuels include methods such as transesterification, catalytic hydrotreating, hydrocracking, catalytic cracking without hydrogen and thermal cracking. Typically, the triglycerides that make up the main component of vegetable oils are converted to the corresponding esters by the transesterification reaction with alcohol in the presence of catalysts. The resulting product is a fatty acid alkyl ester, most often a fatty acid methyl ester (PAME). However, the poor low-temperature properties of RAME limit its wider use in regions with cold climatic conditions. Poor cold flow characteristics are the result of the linear chain nature of the PAME molecule, and thus double bonds are required to create uniform acceptable cold flow characteristics. Carbon-carbon double bonds and ester groups, however, reduce the stability of fatty acid esters, which is the main disadvantage of transesterification technology. Moreover, C. Schmidt and J. W. Herpen (8c1ishb1 K., Sgspsp. 1. V., 8AE (8oc1c1u o £ AnYushoTsus Epdshega, Society of Automotive Engineers), article 961086, report that the presence of oxygen in esters leads to unwanted and increased emissions of NΟ _x compared to conventional diesel fuels.

Unwanted oxygen can be removed from fatty acids or esters through deoxygenation reactions. Deoxygenation of oils and fats of biological origin, which include oils and fats based on biological material, to hydrocarbons useful as diesel fuel products, can be performed in the presence of a catalyst under controlled hydroprocessing conditions known as hydrotreating or hydrocracking methods.

During hydrodeoxygenation, the oxo groups react with hydrogen and are removed by the formation of water. The hydrodeoxygenation reaction requires relatively large amounts of hydrogen. Due to the high exothermicity of the reactions, it is extremely important to control the thermal effect of the reaction. An excessively high reaction temperature, insufficient regulation of the reaction temperature, or too low a concentration of hydrogen in the feed stream causes increased formation of undesirable side reaction products and coking of the catalyst. Undesirable side reactions, such as cracking, polymerization, ketonization, cyclization and aromatization, reduce the yield and worsen the properties of the diesel fraction. Unsaturated raw materials and free fatty acids in triglyceride biological oils can also contribute to the formation of high molecular weight compounds.

US patents 4,992,605 and 5,705,722 describe methods for producing diesel fuel additives by converting biological oils to saturated hydrocarbons under hydroprocessing with nickel-molybdenum (ΝίΜο) and cobalt-molybdenum (CoMo) catalysts. Hydrotreating is carried out at high temperatures of 350-450 ° C and gives n-paraffins and other hydrocarbons. The product has a high cetane number, but poor properties in cold conditions, which limit the amount of product that can be mixed with conventional diesel fuel in the summer and prevent its use in the winter. The formation of heavy compounds with a boiling point of about 343 ° C was observed, especially when a fraction of fatty acids was used as a raw material. A lower limit of 350 ° C for the reaction temperature was derived as a necessary condition for uninterrupted operation.

A two-stage process is described in patent P1 100248 for the production of middle distillates from vegetable oils by hydrogenation of fatty acids or triglycerides derived from vegetable oil using commercial desulfurization catalysts such as nickel molybdenum (ΝίΜο) and cobalt-molybdenum (CoMo), with the formation of n- paraffins followed

- 1 013754 isomerization of the above n-paraffins using metal-containing molecular sieves or zeolites to obtain branched paraffins. Hydrotreating was preferably carried out at high reaction temperatures of 330-450 ° C, mainly 390 ° C. Hydrogenation of fatty acids at such high temperatures shortens the life of the catalyst due to coking and the formation of by-products.

Patent EP 1396531 describes a process comprising at least two steps, the first of which is a hydrodeoxygenation step, and the second step is a hydroisomerization step using a countercurrent principle, and a biological feedstock containing fatty acids and / or fatty acid esters serving in quality of feedstock. The method includes, optionally, the stage of distillation of light fractions.

Cracking is a significant adverse reaction in the isomerization of n-paraffins. Cracking increases with increasing isomerization conversion (under more severe reaction conditions) and decreases the yield of diesel fraction. The stringency of the isomerization conditions (isomerization conversion) also determines the number of methyl branches formed and the distance between them, and thereby the cold characteristics of the produced biodiesel fraction.

Patent GK 2,607,803 describes a method for hydrocracking vegetable oils or their derivatives of fatty acids under high pressure to form hydrocarbons and to some extent acid. The catalyst contains a metal dispersed on a support. The high reaction temperature of 370 ° C did not ensure complete conversion and high selectivity of the formation of n-paraffins. The resulting product also contained some intermediate derivatives of fatty acids.

The formation of water during hydrotreatment is mainly due to the deoxygenation of triglyceride oxygen under the action of hydrogen (hydrodeoxygenation).

Deoxygenation using hydrodeoxygenation conditions is to some extent accompanied by a decarboxylation reaction route, described below as reaction A, and a decarbonylation reaction route (reaction B1 and B2). Deoxygenation of fatty acid derivatives by means of decarboxylation and / or decarbonylation reactions forms carbon oxides (CO ₂ and CO) and aliphatic hydrocarbon chains containing one less carbon atom than in the original fatty acid molecule. After this, the water gas conversion reaction can equalize the concentrations of CO and CO ₂ (reaction E). The methane synthesis reaction uses hydrogen and forms H ₂ O and methane if it is feasible under hydrotreating conditions (reaction Ό). Hydrogenation of fatty acids produces aliphatic hydrocarbons and water (reaction C). Reaction Schemes AE are described below.

Decarboxylation: C ₁₇ H ₃₅ COOH C ₁₇ H ₃₆ + CO ₂ (BUT) Decarbonylation: С ₁₇ Н ₃₅ С00Н + Н ₂ -> С „Н ₃₆ + СО + Н ₂ О (IN 1) C ₁₇ H ₃₅ COOH C ₁₇ H ₃₄ + CO + H ₂ O (AT 2) Hydrogenation: C1 ₇ H ₃ $ COOH and SZ ₂ -> S1dN ₂ 2 + 2H ₂ O (FROM) Methane Synthesis: co + zn ₂ -> sn ₄ + n _g o Water Gas Conversion: СО + Н ₂ О -> Н ₂ + С0 ₂ (E)

The feasibility of decarboxylation varies greatly depending on the type of carboxylic acid or its derivative used as starting material. Alpha-hydroxy-, alpha-keto-and dicarboxylic acids are activated forms, and they are more easily deoxygenated during decarboreaction, which means decarboxylation and / or decarbonylation. Linear aliphatic acids are not activated in this way, and in general they are difficult to deoxygenate through decarbo reactions, and they require much more stringent reaction conditions.

The decarboxylation of carboxylic acids to hydrocarbons in contact of carboxylic acids with heterogeneous catalysts was proposed by V.F. Mayer and colleagues (Ma1eg, G. s1 a1: Sysh15sie VspySys (1982), Volume 115, No. 2, pp. 808-812). Meyer and co-workers tested Νί / Ά1 ₂ Ο ₃ and Ρά / δίΟ ₂ catalysts for decarboxylation of certain carboxylic acids. During the reaction, reactant vapors were passed through a catalyst bed with hydrogen. Hexane was the main product of decarboxylation of enanthic acid, taken as a test compound.

US 4,554,397 discloses a process for the production of linear olefins from saturated fatty acids or esters, providing a catalyst system that consists of nickel and at least one metal selected from the group consisting of lead, tin and germanium. With other catalysts, such as S / C, low catalytic activity and cracking to saturated hydrocarbons, or the formation of ketones when Raney nickel was used, were observed.

Decarboxylation accompanied by hydrogenation of the oxo compound is described in the articles Eaigey !, E., Oe1oi. B .: Arrieb Ca1a1u515, A: Oeyega1 (1994), 109 (1), pp. 77-96 and 97-115, in which the hydrodeoxygenation of oils obtained by pyrolysis of biomass was studied over sulfurized CoMo / γ-Α1 ₂ Ο ₃ and

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ΝίΜο / γ-Α1 ₂ 0 ₃ catalysts. Diethyl decanedioate was used among others as a model compound, and it was found that the rates of formation of the decarboxylation product, nonane, and the hydrogenation product, decane, were comparable under hydrotreating conditions (260-300 ° C, 7 MPa, in hydrogen). The presence of hydrogen sulfide (H ₂ §) in the feed contributed to the decarboxylation selectivity compared to the sulfur-free feed. Various levels of sulfur were investigated, but no effect on the selectivity of decarboxylation of diethyl decanedioate was detected.

Biological raw materials often contain certain impurities, such as metal compounds, organic nitrogen-containing, sulfur-containing and phosphorus-containing compounds, which are known inhibitors of catalytic activity and catalytic poisons, which inevitably shorten the life of the catalysts and create the need for more frequent regeneration or replacement of the catalyst. Metals in biological oils / fats inevitably accumulate on the surface of the catalyst and alter the activity of the catalyst. Metals can favor certain side reactions and block the active sites of catalysts, usually reducing activity.

The composition of fatty acids, the size and degree of saturation of the fatty acid molecule can vary significantly in raw materials of various origins. The melting point of biological oil or fat is mainly a consequence of the degree of saturation. Fats are more saturated than liquid oils, and in this respect require less hydrogen to hydrogenate double bonds. Double bonds in fatty acid chains also contribute to various types of side reactions, such as oligomerization / polymerization, cyclization / aromatization and cracking reactions, which deactivate the catalyst, increase hydrogen consumption and reduce the yield of the diesel fraction.

The hydrolysis of triglycerides also produces diglycerides and monoglycerides, which are partially hydrolyzed products. Diglycerides and monoglycerides are surfactants that can form emulsions and make separation of the liquid phases of water and oil more difficult. Biological oils and fats may also contain other, such as glycerides, surfactants such as phospholipids, such as lecithin, which contain phosphorus in their structures. Phospholipids are gummy materials that can be harmful to catalysts. Natural oils and fats also contain non-glyceride components. Among others, they are waxes, sterols, tocopherols and carotenoids, some metals and organic sulfur compounds, as well as organic nitrogen compounds. These compounds may be harmful to the catalysts or create other problems in the process.

Vegetable oils / fats and animal oils / fats may contain free fatty acids, which are formed during the processing of oils and fats by hydrolysis of triglycerides. Free fatty acids are a class of problematic compounds in biological oils and fats, where their typical content is from 0 to 30% by weight. Free fatty acids are corrosive in nature, they can corrode materials from a plant or catalyst, and they can contribute to side reactions such as the formation of metal salts of carboxylic acids in the presence of metal impurities. Due to the fact that free fatty acids are contained in biological oils and fats, the formation of compounds with a high molecular weight is significantly enhanced compared to triglyceride biological raw materials having only small amounts of free fatty acids, usually below 1% by weight.

Deoxygenation of vegetable oils / fats and animal oils / fats with hydrogen requires a little more hydrogen and at the same time, a significant amount of heat is released. Heat is released in the reactions of deoxygenation and hydrogenation of double bonds. Different raw materials produce significantly different amounts of heat of reaction. The variation in the released heat of reaction is mainly determined by the method of hydrogenation of double bonds. The average number of double bonds per triglyceride molecule can vary from about 1.5 to more than 5, depending on the source of biological oil or fat.

Subject of invention

The subject of the invention is an improved method for the production of hydrocarbon fractions of diesel fuel from oils and fats of biological origin with a reduced consumption of hydrogen.

A further subject of the invention is an improved method for the production of hydrocarbons of a diesel fraction from oils and fats of biological origin with high selectivity, and this method provides a product with improved cold flow properties, while not reducing the yield of diesel fraction during isomerization.

A further subject of the invention is an improved method for the production of hydrocarbons of a high-quality fraction of diesel fuel from oils and fats of biological origin with a reduced hydrogen consumption and a high yield of diesel fraction.

Distinctive features of the method according to the invention are presented in the claims.

Definitions

Here, hydroprocessing is understood as the catalytic treatment of organic material with molecular hydrogen in any way.

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Here, hydrotreating is understood as a catalytic method that removes oxygen from organic oxygen-containing compounds in the form of water (hydrodeoxygenation, ΗΌΟ), sulfur from organic sulfur-containing compounds in the form of hydrogen sulfide (Η ₂ 8) (hydrodesulfurization, ΗΌ8), nitrogen from organic nitrogen-containing compounds in the form of ammonia (ΝΗ ₃ ) (hydrodenitrification, ΗΌΝ) and halogens, such as chlorine from organic chlorine compounds in the form of hydrogen chloride (HC1) (hydrodechlorination, IES1), usually under the action of sulphide осο or sulphurous x CoMo catalysts.

Here, deoxygenation is understood in the sense of removing oxygen from organic molecules, such as derivatives of fatty acids, alcohols, ketones, aldehydes or esters, by any of the means previously described.

Here, the hydrodeoxygenation (ΗΌΟ) of triglycerides or other derivatives of fatty acids or fatty acids is understood to mean the removal of carboxylic oxygen in the form of water by the action of molecular hydrogen under the influence of a catalyst.

Here, the decarboxylation and / or decarbonylation of triglycerides or other derivatives of fatty acids or fatty acids is understood in the sense of removing carboxylic oxygen in the form of CO ₂ (decarboxylation) or in the form of CO (decarbonylation) under the influence of molecular hydrogen or without it. Decarboxylation and / or decarbonylation reactions are referred to as decarboxylation.

Here, hydrocracking is understood as the catalytic decomposition of organic hydrocarbon materials using molecular hydrogen at high pressures.

Here, hydrogenation means the saturation of carbon – carbon double bonds by the action of molecular hydrogen under the influence of a catalyst.

Here, n-paraffins mean normal alkanes or linear alkanes that do not contain side chains.

Here isoparaffins means alkanes having one or more C1-C9, typically _C1-C2 alkyl side chains, typically mono-, di-, tri- or tetrametilalkany.

The feed (the initial reaction mixture as a whole) in the hydrotreatment step should be understood to include fresh feed and, optionally, at least one diluent.

SUMMARY OF THE INVENTION

The present invention relates to an improved method comprising a hydrotreating step and an isomerization step for producing hydrocarbons of a diesel fraction from renewable sources such as oils and fats of biological origin, such as vegetable oils / fats and animal and fish oils / fats, especially C ₁₂ -C ₁₆ fatty acids and / or their derivatives, in the presence of sulfur. The invention relates to hydrotreating feedstocks, including triglycerides, fatty acids and derivatives of fatty acids, and in particular C ₁₂ -C ₁₆ fatty acids and / or their derivatives or combinations thereof, in n-paraffins with reduced consumption of hydrogen during hydrotreating, in the presence of sulfur, with subsequent conversion of n-paraffins to branched alkanes of the diesel type using isomerization with a high yield of diesel fraction. The hydrocarbon fuel product formed in this way is a high quality diesel component. In the hydrotreating step, the feed is contacted with a sulfurized hydrotreating catalyst in the presence of sulfur, followed by an isomerization step with an isomerization catalyst.

DETAILED DESCRIPTION OF THE INVENTION

It has been unexpectedly discovered that hydrogen consumption in the hydrotreating step, deoxygenation of fatty acids and / or derivatives of fatty acids, and cracking during isomerization of n-paraffins can be significantly reduced by adding one or more sulfur compounds to the feed to achieve a sulfur content of 50-20000 weight. mn ^-1 (te-rrsh), preferably 1000-8000 w. mn ^-1, most preferably 2000-5000 w. ^-1 million in the feed, calculated as elemental sulfur, particularly when bio oils and fats containing C ₁₂ -C ₁₆ fatty acids and / or their derivatives, use camping as fresh feed for the hydrotreatment step.

Feedstock

The biological oil and / or fat used as fresh raw materials in the method according to the present invention, come from renewable sources, such as fats and oils from plants and / or animals, and / or fish and compounds derived from them. The basic structural unit of a typical vegetable or animal oil / fat useful as a feedstock is triglyceride, which is a complex triester of glycerol and three fatty acid molecules having the structure shown in the following formula I:

Formula 1. The structure of triglyceride

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In formula I, the groups Κι, Κ ₂ and K ₃ are alkyl chains. The fatty acids found in natural triglycerides are almost exclusively fatty acids with an even number of carbon atoms. Therefore, the Κ · K ₂ and K ₃ groups typically represent C ₅ -C ₂₃ -alkyl groups, for the most part Ci-C19-alkyl groups, and most typically Ci- ₅ or C ^ -alkyl groups. The radicals Κι, K ₂ and K ₃ may contain carbon-carbon double bonds. These alkyl chains may be saturated, unsaturated or polyunsaturated. Suitable biological oils are vegetable oils and fats, animal fats, fish oils and mixtures thereof, containing fatty acids and / or fatty acid esters. Examples of these materials are wood based fats and oils and other vegetable based fats and oils, such as rapeseed oil, rape oil, canola oil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil , palm oil, peanut oil, castor oil, coconut oil, as well as fats found in genetically modified plants, animal fats such as pork, lard, blubber, and fats found in milk, as well as regeneration ated fats, food industry and mixtures thereof.

Typically, biological oils or fats suitable as raw materials contain C ₁₂ -C ₂₄ fatty acids, derivatives thereof, such as anhydrides or esters of fatty acids, as well as fatty acid triglycerides, or combinations thereof. Fatty acids or derivatives of fatty acids, such as esters, can be obtained by hydrolysis of biological oils or their fractionation or triglyceride esterification reactions.

In the method according to the invention, the fresh feed contains at least 20%, preferably at least 30% and most preferably at least 40% by weight of C ₁₂ C ₁₆ fatty acid triglycerides or C ₁₂ -C ₁₆ fatty acid esters or C ₁₂ -C ₁₆ fatty acids or combinations thereof. Examples of such raw material grades are palm oils and animal fats comprising fatty acids with a lower number of carbon atoms, which are typically more saturated than _C18 fatty acids, and their tendency to decarboxylation during hydrodeoxygenation smaller than that of the fatty acids with more high carbon atoms. Fresh raw materials may also include biological raw materials and hydrocarbons or hydrocarbons.

C1 ₂ -C16 fatty acids can be bound to glycerol as triglycerides or other esters. Animal fats and triglycerides of palm oil contain significant amounts of C ₁₆ fatty acids, typically 15-45% by weight, and in particular palmitic acid. Other plant triglycerides contain only 1-13% by weight of C ₁₆ fatty acids, for example, rapeseed oil only 15% by weight.

In order to avoid catalyst deactivation and unwanted side reactions, the feed must meet the following requirements: the amount of alkali and alkaline earth metals calculated on elemental alkaline and alkaline earth metals in the feed is less than 10, mainly less than 5 and most preferably less than 1 weight. ppm ^-1 . The amount of other metals calculated on elemental metals in the feed is less than 10, mainly less than 5 and most preferably less than 1 weight. ppm ^-1 . The amount of phosphorus per elemental phosphorus is less than 30, preferably less than 15 and most preferably less than 5 weight. ppm ^-1 .

In many cases, the feedstock, such as untreated vegetable oil or animal fat, is not suitable as such for processing due to the high content of impurities, and therefore, the feedstock is predominantly purified using one or more suitable generally accepted purification technologies before entering it into the hydrotreating stage of the process. Examples of a number of commonly accepted technologies are given below.

Dehumming vegetable oils / fats and animal oils / fats means removing phosphorus-containing compounds such as phospholipids. Solvent-extracted vegetable oils often contain significant amounts of gums, typically 0.5-3% by weight, which are mostly phosphatides (phospholipids), and therefore a degumming step is required for crude vegetable oils and animal fats to remove phospholipids and metals present in crude oils and fats. Iron, as well as other metals, may be present in the form of metal phosphatide complexes. Even trace amounts of iron can cause catalytic oxidation of oil or fat.

Degumming is carried out by washing the raw materials at a temperature of 90-105 ° С and a pressure of 300-500 kPa (absolute) Н ₃ РО ₄ , ΝαΟΗ and softened water and separating the formed gums. The bulk of the metal components that are harmful to the hydrotreating catalysts are also removed from the feedstock during the degumming step. The moisture content in the degummed oil is reduced in the dryer at a temperature of 90-105 ° C and a pressure of 5-50 kPa (absolute).

The amount of free fatty acids present in vegetable oils is typically 1-5% by weight, and in animal fat 10-25% by weight. High amounts of free fatty acids in the feed can be reduced using a deoxidation step that can be performed, for example, by steam stripping. The feedstock, which is optionally degummed,

- 5 013754 is usually first degassed at a pressure of 5-10 kPa (absolute) at a temperature of approximately 90 ° C. After that, the resulting oil is heated to about 250-280 ° C under a pressure of 5-10 kPa (absolute) and sent to a stripping column, where free fatty acids are distilled off with hot steam at 230-260 ° C, and the oil is deodorized in vacuum. The fatty acid fraction is taken from the top of the column.

The feedstock, which is optionally degummed or refined in some other traditional way, can be bleached. During bleaching, the degummed or refined feedstock is heated and mixed with natural or acid-activated bleaching clay. Bleaching removes a variety of trace impurities remaining after other stages of pre-treatment such as dehumming, such as chlorophyll, carotenoids, phospholipids, metals, soaps and oxidation products. Whitening is typically carried out in vacuo to minimize possible oxidation. Bleaching is used to reduce the amount of color pigments, to produce an acceptable color oil, and to reduce the tendency of the oil to oxidize.

Below, the method according to the invention, comprising a hydrotreating step and an isomerization step, is described in more detail.

Hydrotreating Stage

The feed to the hydrotreatment unit includes fresh feed and optionally at least one diluent. The diluent may be a hydrocarbon of biological origin and / or non-biological origin. In the case where the feed includes an additional at least one diluent, it is preferred that the feed contains less than 20% by weight of fresh feed.

The diluent may also be a recycle product from the method (return product), and in addition, the diluent / fresh feed ratio is 5-30: 1, preferably 10-30: 1, and most preferably 12-25: 1.

The feedstock generally comprising fresh feed containing at least 20%, preferably at least 30% and most preferably at least 40% by weight of triglycerides of C ₁₂ -C ₁₆ fatty acids or esters of C ₁₂ -C ₁₆ fatty acids or C ₁₂ -C ₁₆ fatty acids, or combinations thereof, is hydrotreated in the presence of hydrogen with a catalyst under hydrotreatment conditions in the presence of 50-20000 weight. mn ^-1, preferably 1000-8000 w. mn ^-1, most preferably 2000-5000 w. ^-1 million of sulfur in the feedstock as a whole, based on elemental sulfur.

In the hydrotreatment step of the process, fatty acids, triglycerides and fatty acid derivatives are deoxygenated, denitrified, desulfurized and dechlorinated.

In the hydrotreating step, known hydrogenation catalysts containing metals from groups VIII and / or νίΒ of the periodic system can be used. Advantageously, the hydrogenation catalysts are catalysts containing Ρά, Ρΐ, Νί, илиο or CoMo on supports, where the supports may be alumina and / or silica, as described, for example, in patent No. 100248. Typically, ΝίΜο / Ά1 _{2 are used.} Θ ₃ and CoMo / A1 ₂ O ₃ catalysts.

At the hydrotreating stage, the pressure range can vary between 2 and 15 MPa, mainly between 3 and 10 MPa and most preferably between 4 and 8 MPa, and temperatures between 200 and 400 ° C, mainly between 250 and 350 ° C and most preferably 280-345 ° C.

It has been found that deoxygenation of starting materials from renewable sources can be controlled with direction along two partially alternative reaction routes: hydrodeoxygenation and decarboxylation and / or decarbonylation. The selectivity of decarboreaction and deoxygenation due to decarboreaction in a hydrotreatment method can be facilitated by a hydrotreatment catalyst using a sulfur content of 50-20000 weight. ^-1 million in the feed as a whole. With a certain sulfur content in the feed, it is possible to double the yield of n paraffins formed by the removal of CO _X. The complete deoxygenation of triglycerides using decarboreaction can theoretically reduce hydrogen consumption by about 60% (maximum) compared to pure hydrogen deoxygenation, as can be seen in Table. 3.

At least one organic or inorganic sulfur compound may be added together with hydrogen or with the raw material to achieve the desired sulfur content. The inorganic sulfur compound may be, for example, H ₂ or elemental sulfur, or the sulfur compound may be a readily degradable organic sulfur compound such as dimethyldisulfide, carbon disulfide and butylthiol, or a mixture of readily degradable organic sulfur compounds. It is also possible to use refinery gas or liquid streams containing decomposable sulfur compounds.

From the examples, an unexpected observation was made that with the addition of sulfur compounds in raw materials, bringing the sulfur content to 100-10000 weight. ^-1 million in the feed the decarboxylation of short chain fatty acids and derivatives thereof such as _C16 fatty acids increases significantly more than that of _C18 fatty acids.

When C1 ₆ -containing fatty acids and their derivatives undergo hydrodeoxygenation, n-C ₄₅ and n-C ₄₆ paraffins are formed with melting points of 9.9 and 18.2 ° C, respectively. The conversion of other vegetable oils such as rapeseed oil and soybean oil gives almost completely nC ₁₇ - and nC18 paraffins with significantly higher melting points of 22.0 and 28.2 ° C.

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The hydrodeoxygenation of triglycerides facilitates the controlled decomposition of a triglyceride molecule in spite of uncontrolled cracking. Double bonds are also hydrogenated in a controlled hydrotreatment process.

The resulting light hydrocarbons and gases, mainly propane, water, CO ₂ , CO, H ₂ § and ΝΗ ₃ , are removed from the hydrotreated product.

In the case where the fresh feed contains more than 5% by weight of free fatty acids, it is preferable to use a diluent or recycle product in the method, as described in the figure, which shows an improved reactor design, especially to control the temperature rise above the catalyst bed and the development of a side reaction . The figure shows the layout of a hydrotreating process comprising one or more successive catalyst beds, introducing a hydrotreated recycle product into the top of the first catalyst bed, and introducing fresh feed, coolant, and hydrogen into the top of each catalyst bed. This is manifested in improved control of the reaction temperature in the catalyst beds and thereby in the reduction of undesired side reactions.

In the drawing, the hydrotreating reactor 100 includes two catalyst beds 10 and 20. Fresh feed 11 is introduced as streams 12 and 13 into the catalyst beds 10 and 20, respectively, and hydrogen in the form of streams 22 and 23 into the catalyst beds 10 and 20, respectively. The fresh feed stream 12 is first mixed with the hydrotreated recycle product stream 41 and the coolant stream 43, and the resulting mixture 31 diluted in the fresh feed concentration is then introduced onto the catalyst bed 10. In order to obtain the desired sulfur concentration in the feed stream 31, the desired a compensating amount of sulfur is added to the fresh feed stream 11 through stream 15. As the mixture 31 passes through the catalyst bed 10 with a stream of hydrogen 22, fatty acids and derivatives of fatty acids from the fresh stream raw materials 12 are converted into the corresponding reaction products. A two-phase stream 32 is discharged from the bottom of the catalyst layer 10 and mixed with a stream of fresh raw materials 13, a stream of cooling liquid 44 and a stream of hydrogen 23. The formed vapor-liquid mixture 33 diluted in the concentration of fresh raw materials is then introduced onto the catalyst layer 20 at a reduced temperature due to the cooling effect of hydrogen of coolant and fresh feed is passed through the catalyst bed 20 and finally removed from the catalyst bed as product stream 34. Stream 34 is separated into steam stream 35 and liquid stream 36 into ysokotemperaturnom separator 101. Vapor stream 35 is rich in hydrogen and is directed to further processing. A portion of the liquid stream 36 is returned to the reactor 100 as a recycle stream 40, which is further divided into a diluent stream 41 and a total coolant stream 42. The coolant stream 42 is cooled in the heat exchanger 102 to provide proper cooling effect in the upper parts of the catalyst layers 10 and 20. The stream The hydrotreated product 51 is sent from the hydrotreatment step to further processing.

The catalyst layers 10 and 20 can be placed in the same high-pressure chamber or in separate high-pressure chambers. In an embodiment in which the catalyst beds are in the same high pressure chamber, hydrogen flows 22 and 23 can alternatively be introduced into the catalyst bed 10 and then passed through the catalyst beds 10 and 20. In an embodiment in which the catalyst beds are located in different high-pressure chambers, the catalyst layers can operate in parallel with separate diluent streams, hydrogen streams and coolant streams. The number of catalyst layers may be one or two, or more than two.

Sulfur replenishment in the hydrotreating step may be introduced with a fresh feed stream 11. Alternatively, the required amount of sulfur may be supplied with hydrogen streams 22 and 23 as a gaseous sulfur component, such as hydrogen sulfide.

Hydrogen is supplied to the hydrotreating reactor in excess of the theoretical consumption of hydrogen. In the method of the hydrotreatment step, triglyceride oils, fatty acids and their derivatives are converted, with a theoretical yield, to n-paraffins without or almost without adverse reactions. Additionally, propane is formed from the glycerol portion of triglycerides, water and CO and / or CO ₂ from carboxylic oxygen, H ₂ § from organic sulfur compounds, and ΝΗ ₃ from organic nitrogen compounds.

Using the above technologies at the hydrotreating stage, the temperature required to start the reactions is reached at the beginning of each catalyst layer, the temperature increase in the catalyst layers is limited, the formation of harmful and partially reacted intermediates can be avoided, and the service life of the catalyst is significantly increased. The temperature at the end of the catalyst bed is controlled by its own heat of reaction and, to some extent, by the use of a diluent. The diluent may be any available hydrocarbon of biological origin or non-biological origin. It may also be a recycle product. If a diluent is used, the content of fresh raw materials in the raw material as a whole may be less than 20% by weight. If a recycle product is used, the ratio of recycle product to fresh raw materials is 5-30: 1, preferably 10-30: 1, most preferably 12-25: 1. After the hydrotreating step, the product is processed in the isomerization step.

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Isomerization of n-paraffins formed in the hydrotreatment process.

To improve the cold performance of products, isomerization of n-paraffins is required. Branched isoparaffins are formed during isomerization. As a rule, isoparaffins may contain mono-, di-, tri- and tetramethyl branches.

The product obtained from the hydrotreatment step isomerized using a catalyst under isomerization conditions. The raw material for the isomerization reactor is a mixture of pure n-paraffins, and the composition of the feed can be predicted by the distribution of fatty acids in each individual biological oil used as a feed for hydrotreating.

The isomerization step may include, optionally, a purification step in which the reaction product from the hydrotreatment step can be purified using a suitable method, such as evaporation with water vapor or a suitable gas, such as light hydrocarbon, nitrogen or hydrogen. Mostly acidic gases and aqueous impurities are removed as completely as possible before contact of the hydrocarbons with the isomerization catalyst.

At the isomerization stage, the pressure varies in the range of 2-15 MPa, mainly in the range of 3-10 MPa, and the temperature varies between 200 and 500 ° C, mainly between 280 and 400 ° C.

In the isomerization step, isomerization catalysts known in the art can be used. Suitable isomerization catalysts comprise molecular sieves and / or a metal selected from group VIII of the periodic table and / or a carrier. Advantageously, the isomerization catalyst contains 8ΛΡΘ-11 or 8ΆΡΘ-41 or Ζ8Μ-22 or Ζ8Μ-23 or ferrierite and Ρΐ, Ρ6 or N1 and A1 ₂ O ₃ or δίθ ₂ . Typical isomerization catalysts are, for example, P1 / 8APO-11 / A1 ₂ O ₃ , ΡΙ / Ζ8Μ22 / A1 ₂ O ₃ , Ρΐ / Ζ8Μ-23 / Α1 ₂ Ο ₃ and Ρΐ / 8ΑΡΟ-11 / 8ίΟ ₂ . Many of these catalysts require the presence of hydrogen to reduce catalyst deactivation.

The isomerized diesel product mainly consists of branched hydrocarbons, as well as linear hydrocarbons, and has a boiling point in the range of 180-3 50 ° C. Additionally, some gasolines and gasoline can be obtained.

Advantages of the Invention

The method according to the invention opens the way to reducing the formation of compounds with a higher molecular weight during hydrotreating of fresh raw materials, which may contain fatty acids and their derivatives. The method according to the invention is the selective production of hydrocarbons of the diesel fraction from biological oils and fats with a high yield of diesel fraction and without significant adverse reactions. Branched hydrocarbons can be produced from vegetable oils and fats, as well as animal and fish oils and fats using the facilitating participation of decarbo reactions in the hydrodeoxygenation process, and thereby the consumption of hydrogen is reduced by 20-60%, typically by 20-40%.

During deoxygenation of the feed by decarboxylation and / or decarbonylation, oxygen is removed in the form of CO or CO ₂ . Decarboreaction reduces the consumption of hydrogen, theoretically with complete deoxygenation by about 60-70% compared to the full hydrodeoxygenation route, but depends on the source of triglycerides. C ₁₂ -C ₁₆ fatty acids and their derivatives typically have fewer double bonds, and their tendency to decarboxylate in the hydrodeoxygenation process is less than fatty acids with a higher number of carbon atoms and their derivatives. However, it was unexpectedly discovered that when 50-20000 weight. ^-1 million sulfur, calculated as elemental sulfur, was present in the feed comprising fresh feed containing at least 20% by weight of C1 -C1 _{2 6} fatty acids and / or their derivatives, the decarboxylation C1 ₆ fatty acids and their derivatives amplified significantly more than that for C1 ₈ fatty acids and their derivatives. This is manifested in a lower consumption of hydrogen. The added sulfur compounds in the hydrodeoxygenation feedstock facilitate control of catalyst stability and reduce hydrogen consumption. Raw materials such as palm oil or animal fat containing more saturated derivatives of fatty acids produce less heat.

It has also been found that raw materials having a high content of Cl ₂ -Cl ₆ fatty acids and / or their derivatives reduce the consumption of hydrogen in the isomerization step and also improve the cold properties of diesel fuel. The hydrocarbon yield of the diesel fraction is particularly increased in the process of isomerization of n-paraffins due to the lower cracking of naraffins formed during hydrotreatment from raw materials made up of derivatives of fatty acids. The sc-C1 ₆ -n-paraffins formed in the hydrotreatment process require less conversion and lower reaction temperature during isomerization in order to maintain the same cold characteristics of diesel fuel, and thereby significantly reduce the degree of cracking and coking compared to heavier n -paraffins. Alternatively, improved cold performance can be achieved at the same reaction temperature without reducing yield. The stability of the catalysts in the method of hydrotreating and isomerization increases.

The invention is illustrated below by examples representing some preferred embodiments of the invention. However, it is obvious to all technologists that this does not mean limiting the scope of the invention to these examples.

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Examples

Example 1. The effect of sulfur content in raw materials in General.

Palm oil containing free fatty acids in an amount defined as 0.3 percent of the area of the chromatographic peak was used as fresh raw material along with a 5: 1 recycle product in the presence of hydrogen. The content of C ₁₂ -C ₁ b fatty acid triglycerides in fresh raw materials was 58.3% by weight. The raw materials as a whole contained alkali and alkaline earth metals, calculated on elemental alkaline and alkaline earth metals, in an amount below 10 weight. ppm ^-1 . The amount of other metals, calculated on elemental metals, in the feed was less than 10 weight. ppm ^-1 . The amount of phosphorus, calculated on elemental phosphorus, was less than 30 weight. ppm ^-1 .

During the test experiments, various amounts of dimethyldisulfide in the feedstock as a whole were used. The reaction temperature was 305 ° C., the pressure in the reactor was 5 MPa, and the space velocity for fresh feed was 0.5 g / g. A higher sulfur content in the feedstock significantly increased the level of all deoxygenation reactions with the release of CO and CO ₂ (decarboreaction, the formation of n-paraffins with a carbon content of one atom less than the initial fatty acid) instead of deoxygenation with hydrogen (ΗΌΟ, the formation of n-paraffins with the same number of carbon atoms as in the original fatty acid). However, the decarboreaction of C1 ₆ fatty acids increased significantly more than the decarboreaction of higher C1 ₈ or C ₂₀ fatty acids. The high sulfur content in the feedstock reduced the activity of the hydrogenation catalyst of the double bond, and also lowered the level of decarboreaction, as can be seen from Table 1, which shows the effect of sulfur content in raw materials as a whole, calculated on elemental sulfur, on the percentage of decarboration of fatty acids with different numbers of carbon atoms observed in the resulting oil (percentage of decarbo-reaction calculated on fresh raw materials). Tab. 2 shows the relative increase in the decarbo reaction compared to a raw material with a sulfur content of 100 weight. mn ^-1 and Table. 3 represents a theoretical reduction in hydrogen consumption due to decarbo reactions.

Table 1. The effect of sulfur content in raw materials as a whole, calculated on elemental sulfur

Sulfur, 100 ppm ' ¹ (ppm) Sulfur, weight 570 million ^'1 (ppm) Sulfur, 1000 ppm ' ¹ (ppm) Sulfur, 3000 weight ppm ¹ (ppm) Sulfur 5000 million by weight of ^'1 (ppm) Sulfur, 10,000 weight ppm ¹ (ppm) С15 / (С15 + С1б) 29.1% 45.6% 52.6% 55.1% 56.2% 47.5% C17 / (C17 + C18) 30.2% 37.5% 40.1% 42.5% 43.3% 39.7% C19 / (C19 + C20) 36.6% 43.4% 46.0% 48.1% 49.2% 46.5% Decarboreaction in general,% 32.0% 42.2% 46.2% 48.6% 49.5% 44.6%

Table 2. Relative increase in decarboreaction

Sulfur, 570 million ¹ compared with 100 million ' ¹ Sulfur, UOO million 'compared to 100 million ¹ Sulfur, 3000 million ’compared with 100 million ' Sulfur, 5,000 million ' ¹ compared with 100 million ¹ Sulfur 10000 million ^'1 compared to 100 million' ¹ C16 56.8% 80.9% 89.5% 93.2% 63.3% C18 24.1% 32.7% 40.7% 43.2% 31.4% C20 18.7% 25.7% 31.5% 34.4% 27.1% Total 31.9% 44.6% 52.0% 55.0% 39.5%

Table 3. Theoretical hydrogen uptake with and without decarboreaction

Rapeseed oil Palm stearin Palm oil Animal Yasser Consumption of hydrogen (H ₂ molecules per triglyceride), 100% deoxygenation by means of hydrogen ezoxngen and ditch Water 6 6 6 6 Hydrogen substitute 6 6 6 6 Double bonds 4 1.16 1.8 2 Total sixteen 13.16 13.8 14 Consumption of hydrogen (H ₂ molecules per triglyceride), 100% deoxygenation by decarborection Water 0 0 0 0 Hydrogen substitute 3 3 3 3

Double bonds 4 1.16 1.8 2 Total 7 4.16 4.8 5 Hydrogen reduction (maximum) 56% 68% 65% 64%

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Example 2. The effect of C16 fatty acids on cracking during isomerization and the yield of a diesel fraction with the same level of temperature loss of fluidity with raw materials from palm oil.

Palm oil, containing 44.8% by weight of C ₁₂ -C ₁₆ fatty acid triglycerides, was used in fresh raw materials. Dimethyl disulfide was added to palm oil to achieve a sulfur content of about 600 weight. ^-1 million in the feed, calculated as elemental sulfur. The purity of the feed was the same as in Example 1, but the amount of free fatty acids was 0.2 percent of the area of the chromatographic peak. The diluent was not applied. The feed was hydrotreated at 305 ° C. in the presence of hydrogen, the pressure in the reactor was 5 MPa, and the space velocity was 2 g / g for fresh feed. The products contained mainly n-paraffins, n-paraffin raw materials were subjected to isomerization at a temperature of 317 ° C, a pressure of 4 MPa, and the hourly average feed rate (^ H8U) was 3 l / h in the presence of hydrogen. Catalyst (A) contained Ρΐ, 8ΆΡ0-11 and an alumina support. The number of hydrocarbons with more than 10 carbon atoms in the product was 97% by weight. The cloud point of the liquid product was -22 ° C. The results of the analysis of the product are presented in table. 4.

A comparative test was conducted on raw rapeseed oil. Rapeseed oil contained 4.5% by weight of triglycerides C1 ₂ -C1 ₆ fatty acids. Rapeseed oil was hydrotreated and isomerized under the same reaction conditions as described above. The number of hydrocarbons with more than 10 carbon atoms in the product was 96% by weight. The cloud point of the liquid product was -15 ° C. The results of the analysis of the product are presented in table. 4.

Example 3. The effect of C16 fatty acids on the pour point of isomerized diesel oil at the same yield of diesel fraction with palm oil feed.

The hydrotreated palm oil obtained in Example 2 was isomerized at a temperature of 312 ° C, a pressure of 4 MPa, and the hourly average feed rate (\ UN8U) was 3 l / h in the presence of hydrogen and catalyst A. This gave a liquid product with a temperature turbidity of 14 ° C. The amount of hydrocarbons with more than 10 carbon atoms in the product was now 98% by weight. According to the flash point and the distillation profile of the products, a conclusion can be made about a small amount of lighter hydrocarbons, as can be seen from table 4, which presents the results of the analysis of rapeseed and palm oil products that underwent hydrotreating and isomerization, and NK.0 = rapeseed oil after hydrotreating, NRA = palm oil after hydrotreating.

Table 4. Results of analysis of rapeseed and palm oil products that have undergone hydrotreating and isomerization

Raw materials Method Unit Rapeseed oil after hydrotreating Palm oil after hydrotreating Palm oil after hydrotreating Isomerization Temperature ° s 317 317 312 Density at 15 ° C Standard ΕΝ KO 12185 kg / m ³ 782.7 779.2 779.3 Cloud point Standard A8TM 05773 ° C -fifteen -22 -14 Pour point Standard AZTM 05949 -24 -33 -24 Pour point on the filter Standard ΕΝ 116 ®c -fifteen -22 -fifteen Flash point Standard ΕΝ 22719 ° s 52 53 65 Distillation Thermal analysis ° s 117 123 185 Standard ΕΝ KO 3405 5 vol .-% "FROM 274 264 268 10 o6 .-% ° s 282 270 274

30 vol .-% ° C 290 279 280 50 vol .-% ° s 292 283 283 70 vol .-% ° s 294 287 287 90 vol .-% ° s 299 294 294 95 vol .-% ° s 306 298 299 In the body ^{R s} 327 311 308

Example 4. The effect of C16 fatty acids on cracking during isomerization and the yield of the diesel fraction at the same level of temperature loss of fluidity with raw materials from animal fat.

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Animal fat, containing 30% by weight of triglycerides of C12-C16 fatty acids, was used as fresh raw material. The raw materials contained alkali and alkaline earth metals, calculated on elemental alkaline and alkaline earth metals, in an amount of less than 10 weight. ppm ^-1 . The amount of other metals, calculated on elemental metals, in the feed was less than 10 weight. ppm ^-1 . The amount of phosphorus, calculated on elemental phosphorus, was less than 30 weight. ppm ^-1 . Dimethyldisulfide was added to animal fat to achieve a sulfur content of about 100 weight in the feed. ppm ^-1 . Fresh raw materials contained free fatty acids in an amount of respectively 0.6% of the area of the chromatographic peak. The feed was hydrotreated at 300 ° C. in the presence of hydrogen, the pressure in the reactor was 5 MPa, and the space velocity was 2 g / g for fresh feed without any diluent. Products mainly contained n-paraffins. n-Paraffin raw materials were isomerized at a temperature of 316 ° C, a pressure of 4 MPa, and the hourly average feed rate (^ H8U) was 1.5 l / h in the presence of hydrogen. Catalyst (B) contained Ρΐ, 8ΆΡΘ-11 and an alumina support. The number of hydrocarbons with more than 10 carbon atoms in the product was 95% by weight. The cloud point of the liquid product was -20 ° C.

As a comparative example, rapeseed oil was hydrotreated and isomerized under the same reaction conditions as described above. Rapeseed oil contained 4.5% by weight of triglycerides C1 ₂ -C1 ₆ fatty acids. The amount of hydrocarbons with a carbon number of more than 10 in the isomerized product was 95% by weight. The cloud point of the liquid product was -14 ° C.

Example 5. The effect of C16 fatty acids on the temperature of the fluidity loss of isomerized diesel fuel at the same yield of diesel fraction with raw materials from animal fat.

The hydrotreated animal fat obtained in Example 4 was isomerized at a temperature of 312 ° C, a pressure of 4 MPa, and an hourly average feed rate (^ H8U) of 1.5 l / h in the presence of hydrogen and catalyst B. This gave a liquid product with a cloud point of -13 ° C. The number of hydrocarbons with more than 10 carbon atoms was now 98% by weight.

Claims (20)

1. A method of producing hydrocarbons of a diesel fuel fraction in which the feedstock is hydrotreated at the hydrotreatment and isomerization step at the isomerization step, characterized in that the feedstock comprises fresh feedstock containing at least 20 wt.% Cl ₂ -C _{1 6} fatty acids triglycerides, or esters of C12-C1 ₆ fatty acids, or C12-C1 ₆ fatty acids, or combinations thereof, and the raw material as a whole contains 50-20000 ppm by weight ^of sulfur based on elemental sulfur. 2. The method according to claim 1, characterized in that the fresh raw material contains at least 30 wt.% And preferably at least 40 wt.% Triglycerides C1 ₂ -C ₆ fatty acids, or other esters of fatty acids, or combinations thereof . 3. The method according to claim 1 or 2, characterized in that the fresh raw material contains more than 20 wt.% Free fatty acids. 4. A method according to any one of claims 1-3, characterized in that the feed contains less than 10 weight mn ^-1 alkali and alkaline earth metal calculated as elemental alkaline and alkaline earth metals, less than 10 million by weight of other ^-1 metal calculated as elemental metals, and less than 30 weight mn ^-1 phosphorus calculated as elemental phosphorus. 5. The method according to any one of claims 1 to 4, characterized in that the raw material comprises less than 20 wt.% Fresh raw materials and additionally at least one diluent. 6. The method according to claim 5, characterized in that the diluent is a diluent selected from hydrocarbons and recycle products of the method or mixtures thereof, and the ratio of diluent to fresh raw materials is 5-30: 1, preferably 10-30: 1, and most predominantly 12-25: 1. 7. A method according to any one of claims 1-6, characterized in that the feed contains 1000-8000 million by weight of ^-1, and preferably 2000-5000 mn ^-1 weight sulfur calculated as elemental sulfur. 8. The method according to any one of claims 1 to 7, characterized in that at least one inorganic or organic sulfur compound or refinery gas and / or a liquid stream containing sulfur compounds is added to the feed. 9. The method according to any one of claims 1 to 8, characterized in that the fresh raw materials are of biological origin, selected from vegetable oils / fats, animal fats / oils, fish fats / oils, fats contained in plants derived by genetic modification, regenerated fats of the food industry and mixtures thereof. 10. The method according to any one of claims 1 to 9, characterized in that the fresh raw materials are selected from rapeseed oil, rape oil, canola oil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, pork fat, lard, blubber or fats found in milk, or mixtures thereof. 11. The method according to any one of claims 1 to 10, characterized in that the fresh raw materials include raw materials of biological origin and hydrocarbons / hydrocarbons. - 11 013754 12. The method according to any one of claims 1 to 11, characterized in that at the hydrotreatment stage a system of catalyst layers is used, including one or more catalyst layers. 13. The method according to any one of claims 1 to 12, characterized in that at the hydrotreating stage, the pressure varies in the range of 2-15 MPa, mainly in the range of 3-10 MPa, the temperature varies between 200 and 400 ° C, mainly between 250 and 350 ° C and most preferably between 280 and 345 ° C. 14. The method according to any one of claims 1 to 13, characterized in that at the isomerization stage, the pressure varies in the range of 2-15 MPa, mainly in the range of 3-10 MPa, the temperature varies between 200 and 500 ° C, mainly between 280 and 400 ° C. 15. The method according to any one of claims 1 to 14, characterized in that the hydrotreating is carried out in the presence of a hydrogenation catalyst, said hydrogenation catalyst contains a metal from group VIII and / or νίΒ of the Periodic system. 16. The method according to clause 15, wherein the hydrotreating catalyst is a catalyst of Ρά, Ρΐ, Νί, ΝίΜο or CoMo on a carrier and the carrier is alumina and / or silicon oxide. 17. The method according to any one of claims 1 to 16, characterized in that the isomerization catalyst containing molecular sieves is used in the isomerization step. 18. The method according to 17, characterized in that the isomerization catalyst comprises a metal from elements of group VIII. 19. The method according to 17 or 18, characterized in that the isomerization catalyst contains A1 ₂ 0 ₃ or 81O2. 20. The method according to any one of paragraphs.17-19, characterized in that the isomerization catalyst contains 8APO-11, or 8APO-41, or Ζ8Μ-22, or Ζ8Μ-23, or ferrierite and ΡΙ, or Ρά or N1 and A1 ₂ O ₃ , or §ί0 ₂ .