HK1119734B - Process for the manufacture of diesel range hydrocarbons - Google Patents

Description

Process for producing diesel range hydrocarbons

Technical Field

The present invention relates to an improved process for the production of diesel range hydrocarbons from bio-oils and fats with reduced hydrogen consumption. In particular, the present invention relates to an improved process for the production of diesel range hydrocarbons with high selectivity and which produces products with improved cold flow properties without reducing diesel yield during isomerization.

Background

Environmental concerns and the increasing demand for diesel fuel, particularly in europe, have prompted fuel manufacturers to adopt more thoroughly renewable, available feedstocks. In the production of diesel fuel based on biological feedstocks, the main interest has focused on vegetable oils and animal fats, including triglycerides of fatty acids. The long, straight and substantially saturated hydrocarbon chains of the fatty acids chemically correspond to the hydrocarbons present in diesel fuel. However, pure vegetable oils show poor properties, in particular extremely high viscosities and poor stability, and thus their use in transportation fuels is limited.

Traditional routes to convert vegetable oils or other fatty acid derivatives into liquid fuels include processes such as transesterification, catalytic hydrotreating, hydrocracking, catalytic cracking without the use of hydrogen, and thermal cracking. Typically, triglycerides, which form the major component in vegetable oils, are converted to the corresponding esters by transesterification with an alcohol in the presence of a catalyst. The product obtained is a fatty acid alkyl ester, usually a Fatty Acid Methyl Ester (FAME). However, the poor low temperature performance of FAME limits its widespread use in areas where cooler ambient conditions exist. Poor cold flow properties are a result of the long chain nature of the FAME molecules and thus double bonds are required to produce more sustainable cold flow properties. However, the carbon-carbon double bond and the ester group decrease the stability of the fatty acid ester, which is a major drawback of the transesterification technique. Additionally, Schmidt, k., Gerpen j.v.: SAE paper 961086 teaches that the presence of oxygen in the ester results in an undesirable and higher NO relative to conventional diesel fuels_xAnd (4) discharging.

Undesirable oxygen can be removed from the fatty acid or ester by a deoxygenation reaction. Deoxygenation of bio-oils and fats, which refers to oils and fats based on biological materials, into hydrocarbons suitable as diesel fuel products can be carried out in the presence of a catalyst under controlled hydrotreating conditions, known as hydrotreating or hydrocracking processes.

During the hydrodeoxygenation process, oxygen-containing groups react with hydrogen and are removed by the formation of water. The hydrodeoxygenation reaction requires a higher amount of hydrogen. Due to the high heat protection reaction, the control of the heat of reaction is extremely important. Unnecessarily high reaction temperatures, insufficient control of the reaction temperature, or unnecessarily low hydrogen availability in the feed stream, lead to increased formation of unwanted side reaction products and coking of the catalyst. Undesirable side reactions such as cracking, polymerization, ketonization, cyclization and aromatization reduce the yield and performance of diesel fractions. Unsaturated feed and free fatty acids in triglyceride bio-oils may also promote the formation of high molecular weight compounds.

Patents US 4,992,605 and US 5,705,722 describe processes for producing diesel fuel additives by converting bio-oil to saturated hydrocarbons under hydrotreating conditions using NiMo and CoMo catalysts. The hydrotreating operates at high temperatures of 350-450 ℃ and produces normal paraffins and other hydrocarbons. The product has a high cetane number but poor cold performance, which limits the amount of product that can be mixed into conventional diesel fuel in summer and prevents its use during winter. The properties of heavy compounds with boiling points above 343 c are observed, in particular when using fatty acid cuts as feed. The lower limit of the reaction temperature is considered to be 350 ℃ as required for trouble-free operation.

FI 100248 discloses a two-step process for the production of middle distillates from fatty oils by hydrogenation of fatty acids or triglycerides of vegetable oil origin using commercial sulfur removal catalysts such as NiMo and CoMo, whereby n-alkanes are obtained, which are subsequently isomerized using metal-containing molecular sieves to obtain branched alkanes. The hydrotreating is carried out at a higher reaction temperature of 330-450 deg.C, preferably 390 deg.C. Hydrogenation of fatty acids at those high temperatures results in a reduction in catalyst life (due to coking) and the formation of by-products.

EP 1396531 describes a process comprising at least two steps, the first step being a hydrodeoxygenation step and the second step being a hydroisomerization step, using the convection principle, and containing as feed a biological feedstock of fatty acids and/or fatty acid esters. The process includes an optional stripping step.

Cracking is a major side reaction in n-paraffin isomerization. Cracking increases with higher isomerization conversion (more severe reaction conditions) and reduces the yield of diesel. The severity of the isomerization conditions (isomerization conversion) also controls the amount of methyl branches formed and their distance from each other, and the cold properties of the biodiesel fraction produced therefrom.

FR 2,607,803 describes a process for hydrocracking vegetable oils or their fatty acid derivatives at high pressure to obtain hydrocarbons and to some extent acids. The catalyst contains a metal dispersed on a support. High reaction temperatures of 370 ℃ do not allow complete conversion and high selectivity of n-alkanes. The resulting product also contains some intermediate fatty acid compounds.

The formation of water during hydrotreating results primarily from the deoxygenation of triglyceride oxygen by way of hydrogen (hydrodeoxygenation). Deoxygenation using hydrodeoxygenation conditions is accomplished to some extent by a decarboxylation reaction pathway (described below as reaction a), and a decarbonylation reaction pathway (reactions B1 and B2). De-oxidation of fatty acid derivatives by decarboxylation and/or decarbonylation reactions to form Carbon Oxides (CO)₂And CO) and an aliphatic hydrocarbon chain having one less carbon atom than the original fatty acid molecule. The subsequent water gas shift reaction may balance CO with CO₂(reaction E). Methanation reaction employs hydrogen and forms H₂O and methane if they are active during hydrotreating conditions (reaction D). Hydrogenation of the fatty acids yields aliphatic hydrocarbons and water (reaction C). The equations A-E are as follows.

Decarboxylation: c₁₇H₃₅COOH-＞C₁₇H₃₆+CO₂ (A)

Decarbonylation: c₁₇H₃₅COOH+H₂-＞C₁₇H₃₆+CO+H₂O (B1)

C₁₇H₃₅COOH-＞C₁₇H₃₄+CO+H₂O (B2)

Hydrogenation: c₁₇H₃₅COOH+3H₂-＞C₁₈H₃₈+2H₂O (C)

Methanation: CO +3H₂-＞CH₄+H₂O (D)

Water gas shift: CO + H₂O-＞H₂+CO₂ (E)

The feasibility of decarboxylation varies significantly depending on the type of carboxylic acid or its derivative used as the starting material. The alpha-hydroxy, alpha-carbonyl and dicarboxylic acids are in active form and they are readily deoxygenated by decarbonylation (which is herein meant as decarboxylation and/or decarbonylation). Linear fatty acids are not this way of activation and in general they are difficult to deoxygenate by the decarbonation reaction pathway and they require more stringent reaction conditions.

Maier, w.f. et al: chemische Berichte (1982), 115(2), 808-12 suggests decarboxylation of carboxylic acids to hydrocarbons by contacting the carboxylic acid with a heterogeneous catalyst. Maier et Al tested Ni/Al₂O₃And Pd/SiO₂The catalyst decarboxylates several carboxylic acids. During this reaction, the vapors of the reactants are passed through the catalyst bed along with hydrogen. Hexane represents the main decarboxylation product of the test compound hexanoic acid.

Patent US 4,554,397 discloses a process for preparing linear olefins from saturated fatty acids, recommending a catalyst system consisting of nickel and at least one metal selected from lead, tin and germanium. For other catalysts, such as Pd/C, low catalytic activity and cracking to saturated hydrocarbons, or ketone formation using Raney-Ni, were observed.

Lauren t, e., Delmon, b.: applied Catalysis, a: general (1994), 109(1), 77-96 and 97-115 describe decarboxylation with hydrogenation of oxygenates, where biomass-derived pyrolysis oils were studied in sulfiding CoMo/γ -Al₂O₃And NiMo/gamma-Al₂O₃Hydrodeoxygenation over a catalyst. In which diethyl sebacate was used as model compound and the rate of formation of decarboxylation product, nonane and hydrogenation product, decane was found to be comparable under the hydrotreating conditions (260 ℃ C., 7MPa in hydrogen). Hydrogen sulfide (H) in the feed₂S) promotes decarboxylation selectivity relative to the absence of sulfur in the feed. However, the different sulphur levels studied had no effect on the decarboxylation selectivity of diethyl sebacateAnd (6) sounding.

Biological feedstocks often contain impurities such as metal compounds, organic nitrogen, sulfur and phosphorus compounds, which are well known catalyst inhibitors and poisons, inevitably reducing the useful life of the catalyst and necessitating more frequent catalyst regeneration or replacement. Metals in the bio-oil/fat inevitably accumulate on the catalyst surface and alter the activity of the catalyst. Metals may promote some side reactions and clogging of the active sites of the catalyst generally reduces activity.

The fatty acid composition, size and saturation of fatty acids can vary greatly among feeds from different sources. The melting point of biological oils or fats is the main cause of saturation. Fats are more saturated than liquid oils and in this regard require less hydrogen to hydrogenate the double bonds. The double bonds in the fatty acid chains also contribute to different types of side reactions, such as oligomerization/polymerization, cyclization/aromatization and cracking reactions, which deactivate the catalyst, increase hydrogen consumption and reduce diesel yield.

Hydrolysis of triglycerides also produces diglycerides and monoglycerides, which are partial hydrolysis products. Diglycerides and monoglycerides are surface active compounds that can form emulsions and make liquid/liquid separation of water and oil more difficult. Biological oils and fats may also contain other glyceride-like surfactant impurities such as phospholipids, e.g., lecithin, which have phosphorus in their structure. Phospholipids are colloidal materials that can be harmful to the catalyst. Natural oils and fats also contain components other than glycerides. Among these are other waxes, sterones, tocopherols and carotenoids, some metal and organic sulfur compounds and organic nitrogen compounds. These compounds may be harmful to the catalyst or cause other problems in handling.

Vegetable and mineral 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 problematic class of components in biological oils and fats, typically in amounts of 0-30 wt%. Free fatty acids are corrosive in nature, they may attack the materials or catalysts of the process unit, and they may promote side reactions such as the formation of metal carboxylates in the presence of metal impurities. Due to the free fatty acids contained in bio-oils and fats, the formation of high molecular weight compounds is significantly increased when compared to bio-feeds having only low content of free fatty acids, typically less than 1 wt% triglycerides.

Deoxygenation of vegetable and mineral oils/fats with hydrogen requires more hydrogen and at the same time releases a lot of heat. Heat is generated from the de-oxidation reaction and hydrogenation of the double bonds. Different feeds generate significantly different amounts of heat of reaction. The heat of reaction produced varies depending mainly on the double bond hydrogenation. The average amount of double bonds per triglyceride molecule may vary from about 1.5 to above 5, depending on the source of the biological oil or fat.

Object of the Invention

It is an object of the present invention to provide an improved process for the production of diesel range hydrocarbons from bio-oils and fats with reduced hydrogen consumption.

It is another object of the present invention to provide an improved process for the production of diesel range hydrocarbons which has high selectivity and which produces products with improved cold flow properties without reducing the diesel yield during isomerization.

It is another object of the present invention to provide an improved process for producing high quality diesel range hydrocarbons from bio-oils and fats with reduced hydrogen consumption and high diesel yield.

The characteristic features of the method according to the invention are provided in the claims.

Definition of

Hydrotreating is understood herein to mean the catalytic treatment of organic materials by means of all molecular hydrogen.

Hydrotreating is understood herein to mean a catalytic process which removes oxygen from organic oxygen compounds as water (hydrodeoxygenation, HDO) and sulfur from organic sulfur compounds as sulfurHydrogen hydride (H)₂S) (hydrodesulphurization, HDS) removal, nitrogen from organic nitrogen compounds as ammonia (NH)₃) (hydrodenitrogenation, HDN) removal, and removal of halogens such as chlorine from organic chlorides with hydrochloric acid (HCl) (hydrodechlorination, HDCl), typically under the influence of sulfided NiMo or sulfided CoMo catalysts.

Deoxygenation is herein understood to mean the removal of oxygen from an organic molecule, such as a fatty acid derivative, alcohol, ketone, aldehyde or ether, by any of the means previously described.

In this context, Hydrodeoxygenation (HDO) of triglycerides or other fatty acid derivatives or fatty acids is understood to mean the removal of carboxyl oxygen in the form of water by means of molecular hydrogen under the influence of a catalyst.

In this context, decarboxylation and/or decarbonylation of triglycerides or other fatty acid derivatives or fatty acids is understood to mean the oxidation of a carboxyl group with CO₂(decarboxylation) or removal as CO (decarbonylation), with or without the influence of molecular hydrogen. The decarboxylation and/or decarboxylation reaction is denoted as a decarburization reaction.

Hydrocracking is herein understood to mean the catalytic decomposition of organic hydrocarbon materials using molecular hydrogen at elevated pressure.

Herein, hydrogenation means the saturation of carbon-carbon double bonds by means of molecular hydrogen under the influence of a catalyst.

Herein, n-alkane means a conventional alkane or linear alkane having no side chain.

In this context, isoparaffins are meant to have one or more C₁-C₉Typically C₁-C₂Alkyl pendant alkanes, typically mono-, di-, tri-, or tetramethylalkanes.

The feed (total feed) of the hydrotreatment step is understood to comprise fresh feed and optionally at least one diluent.

Summary of The Invention

The present invention relates to an improved process, comprising a hydrotreating step and an isomerization step, for the production of renewable feedstocks such as biological oils and fats, such as vegetable oils/fats and animal oils/fats and fish oils/fats, in particular C₁₂-C₁₆Fatty acids and/or derivatives thereof, in the presence of sulfur, produce diesel range hydrocarbons. The invention relates to a composition comprising triglycerides, fatty acids and derivatives of fatty acids and in particular C₁₂-C₁₆A feed of fatty acids and/or derivatives thereof or combinations thereof is hydrotreated in the presence of sulfur into normal paraffins, the hydrogen consumption during hydrotreating is reduced, and isomerization is subsequently employed to convert the normal paraffins into diesel range branched paraffins, which have a high diesel yield. The hydrocarbon oil product formed by this process is a high quality diesel component. The feed is contacted with a sulfided hydrotreating catalyst in the presence of sulfur in a hydrotreating step, followed by an isomerization step using an isomerization catalyst.

Detailed Description

It has surprisingly been found that the hydrogen consumption in the hydrotreating step, the deoxygenation of the fatty acids and/or fatty acid derivatives, and the cracking during the isomerization of n-paraffins can be significantly reduced by adding one or more sulfur compounds to the feed, thereby achieving a sulfur content in the feed of 50-20000w-ppm, preferably 1000-₁₂-C₁₆Bio-oils and fats of fatty acids and/or derivatives thereof as fresh feed to the hydroprocessing step.

Feeding of the feedstock

The bio-oils and/or fats used as fresh feed in the process of the invention are produced from renewable sources such as fats and oils and compounds derived from them in plants and/or animals and/or fish. The basic building block of a typical vegetable or animal oil/fat suitable as a feedstock is a triglyceride, which is a triester of glycerol with three fatty acid molecules, having the structure shown in formula I below:

formula I: structure of triglyceride

In the formula I, R₁、R₂And R₃Is an alkyl chain. The fatty acids found in natural triglycerides are almost exclusively even-numbered fatty acids. Whereby R₁、R₂And R₃Is typically C₅-C₂₃Alkyl radical, mainly C₁₁-C₁₉Alkyl and most typically C₁₅Or C₁₇An alkyl group. R₁、R₂And R₃May contain carbon-carbon double bonds. These alkyl chains may be saturated, unsaturated or polyunsaturated. Suitable bio-oils are vegetable and vegetable oils and fats, animal fats, fish oils and mixtures thereof containing fatty acids and/or fatty acid esters. Examples of such materials are wood-based and other plant-and vegetable-based fats and oils, such as rapeseed oil (rapeseed oil), rapeseed oil (colza oil), canola 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, fats contained in plants grown by means of genetic manipulation, animal-based fats, such as lard, tallow, whale oil and milk, as well as recycled fats of the food industry and mixtures of the above.

Typically, the bio-oil or fat suitable as a feedstock comprises C₁₂-C₂₄Fatty acids, their derivatives such as anhydrides or esters of fatty acids and triglycerides of fatty acids or combinations thereof. Fatty acids or fatty acid derivatives, such as esters, can be prepared by hydrolysis of biological oils or by their separation or transesterification of triglycerides.

In the process according to the invention, the fresh feed contains at least 20%, preferably at least 30% and most preferably at least 40% by weight of C₁₂-C₁₆Fatty acid glycerolTriesters (trigyceridec)₁₂-C₁₆fat acid) or C₁₂-C₁₆Fatty acid esters or C₁₂-C₁₆Fatty acids or combinations thereof. Examples of such feeds are palm oil and animal fats containing fatty acids with a lower number of carbon atoms, which are typically larger than C₁₈Fatty acids are more saturated and their decarboxylation tendency during hydrodeoxygenation is lower than for higher carbon number fatty acids. The fresh feed may also include biologically derived feed and hydrocarbons or hydrocarbons.

C₁₂-C₁₆Fatty acids may be linked to glycerol to form triglycerides or other esters. Animal fat and palm oil triglycerides contain a high content of C₁₆Fatty acids, typically 15-45 wt% and especially palmitic acid. Other vegetable triglycerides contain only 1-13 wt% C₁₆Fatty acids, such as rapeseed oil, are only 1-5 wt%.

In order to avoid catalyst deactivation and undesired side reactions, the feed should meet the following requirements: the amount of alkali and alkaline earth metals in the feed is below 10, preferably below 5 and most preferably below 1w-ppm calculated on the elemental alkali and alkaline earth metals. The amount of other metals in the feed, calculated as elemental metal, is less than 10, preferably less than 5 and most preferably less than 1 w-ppm. The amount of phosphorus, calculated as elemental phosphorus, is below 30, preferably below 15 and most preferably below 5 w-ppm.

Many times, feeds, such as crude vegetable oils or animal fats, are unsuitable for this treatment due to high impurities, and thus it is preferred to purify the feed using suitable conventional purification procedure or procedures, prior to introducing it into the hydrotreating step of the process. Examples of some conventional procedures are provided below.

Degumming of vegetable and animal oils/fats means removal of phosphorus compounds, such as phospholipids. Solvent extracted vegetable oils often contain a large amount of gums, typically 0.5-3 wt%, which are mainly phospholipids (phospholipids) and thus require a degumming step for crude vegetable oils and animal fats to remove phospholipids and metals present in the crude oils and fats. Iron and other metals may be present in the form of metal-phospholipid complexes. Even trace amounts of iron can lead to catalytic oxidation of oils or fats.

Degumming by using H at 90-105 deg.C and 300-500kPa (a)₃PO₄NaOH and soft water wash feeds and separate the formed gum. Large amounts of metal components, which are detrimental to the hydroprocessing catalyst, are also removed from the feed during the degumming step. The water content of the degummed oil is reduced in a dryer at 90-105 deg.C and 5-50kPa (a).

The amount of free fatty acids present in vegetable oils is typically 1-5 wt% and 10-25 wt% in animal fats. The use of a deacidification step can reduce the amount of free fatty acids in the feed, which can be carried out, for example, by steam stripping. The optionally degummed feed is typically degassed at a temperature of about 90 ℃ under hand at a pressure of 5-10kpa (a). The resulting oil is then heated to about 250-. The fatty acid fraction is recovered from the top of the column.

The feed, optionally degummed or otherwise refined in a conventional manner, may be bleached. In bleaching, the degummed or refined feed is heated and mixed with a natural or acid activated bleaching clay. Bleaching removes a variety of impurity traces such as chlorophyll, carotenoids, phospholipids, metals, soaps and oxidation products that are left from other pretreatment steps such as degumming. Bleaching is typically carried out under vacuum to minimize possible oxidation. Bleaching is used to reduce the color pigments, thereby producing an oil of acceptable color and reducing the tendency of the oil to oxidize.

The process according to the invention, comprising a hydrotreating step and an isomerization step, is described in more detail below.

Step of hydrotreatment

The feed to the hydroprocessing unit comprises fresh feed and optionally at least one diluent. The diluent may be a hydrocarbon of biological and/or non-biological origin. In case the feed comprises further at least one diluent, preferably the feed contains less than 20 wt% of fresh feed.

The diluent may also be the product recycled in the process (product recycle) and subsequently the diluent/fresh feed ratio is in the range of from 5 to 30: 1, preferably from 10 to 30: 1 and most preferably from 12 to 25: 1.

Will comprise at least 20%, preferably at least 30% and most preferably at least 40% by weight of C₁₂-C₁₆Fatty acid triglyceride or C₁₂-C₁₆Fatty acid esters or C₁₂-C₁₆The entire feed of fresh feeds of fatty acids or combinations thereof is hydrotreated with a catalyst in the presence of hydrogen under hydrotreating conditions in the presence of sulfur in the range of from 50 to 20000w-ppm, preferably 1000-.

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

In this hydrotreating step, known hydrogenation catalysts containing metals of group VIII and/or group VIB of the periodic table can be used. Preferably, the hydrogenation catalyst is a supported Pd, Pt, Ni, NiMo or CoMo catalyst and the support is alumina and/or silica, such as those described in FI 100248. Typically, NiMo/Al is used₂O₃And CoMo/Al₂O₃。

In the hydrotreating step, the pressure range may vary between 2-15MPa, preferably between 3-10MPa and most preferably between 4-8MPa, and the temperature varies between 200-400 ℃, preferably between 250-350 ℃ and most preferably between 280-345 ℃.

It has been found that the deoxygenation of raw materials resulting from renewable sources can be controlled between two partially alternative reaction routes: hydro-deoxygenation and decarboxylation and/or decarbonylation (decarbonation reaction). The selectivity of the decarbonization reaction and the deoxygenation by the decarbonization reaction can be promoted during the hydrotreatment over the hydrotreating catalyst, byBy using a sulphur content of 50-20000w-ppm in the total feed. The specific sulfur content in the feed enables the removal of CO by_xThe degree of n-alkanes formed is doubled. The complete deoxygenation of the triglycerides by the decarbonation reaction can theoretically reduce the hydrogen consumption by about 60% (maximum) relative to the pure deoxygenation by hydrogen, as can be seen in table 3.

At least one organic or inorganic sulfur compound may be fed with hydrogen or with the feed material to thereby achieve the desired sulfur content. The inorganic sulfur compound may be, for example, H₂S or elemental sulphur, or the sulphur compound may be a mixture of readily decomposable organic sulphides such as dimethyl disulphide, carbon disulphide and butyl mercaptan or readily decomposable organic sulphides. Refinery gas or liquid streams containing decomposable sulfides may also be used.

It has surprisingly been found from the examples that the addition of sulphur compounds to the feed is used such that the sulphur content in the feed is 100-10000w-ppm, short chain fatty acids and derivatives such as C₁₆Decarboxylation of fatty acids relative to C₁₈The fatty acids increased significantly.

Will contain C₁₆When the fatty acid and its derivative are hydrodeoxidized, a normal C is formed₁₅And n-C₁₆Alkanes having melting points of 9.9 ℃ and 18.2 ℃ respectively. Conversion of other vegetable oils such as rapeseed oil and soybean oil almost exclusively produces positive C₁₇And n-C₁₈Alkanes having higher melting points of 22.0 and 28.2 ℃.

Hydrodeoxygenation of triglycerides facilitates controlled decomposition of the triglyceride molecules, as opposed to uncontrolled cracking. The double bonds are also hydrogenated during this controlled hydrotreating. Light hydrocarbons and gases, mainly propane, water, CO, are formed₂、CO、H₂S and NH₃Removed from the hydrotreated product.

In case the fresh feed comprises more than 5 wt% free fatty acids, it is preferred to use a diluent or product recycle in the process, as shown in figure 1, wherein an improved reactor layout is proposed, in particular for temperature elevation over the catalyst bed and control of side reaction formation. A hydroprocessing process layout is provided in fig. 1, including one or more catalyst beds in series, introduction of a hydrotreated product recycle over the top of a first catalyst bed, and introduction of fresh feed, quench liquid, and hydrogen over the top of each catalyst bed. This results in improved control of the reaction temperature in the catalyst bed and thus in a reduction of undesired side reactions.

In fig. 1, the hydroprocessing reactor 100 includes two catalyst beds 10 and 20. Fresh feed 11 is introduced in streams 12 and 13 to catalyst beds 10 and 20, respectively, and hydrogen is introduced in streams 22 and 23 to catalyst beds 10 and 20, respectively. The fresh feed stream 12 is first mixed with the hydrotreated product recycle stream 41 and the quench liquid stream 43 and the resulting mixture 31 is diluted in fresh feed concentrate and subsequently introduced onto the catalyst bed 10. To achieve the desired sulfur concentration in feed stream 31, the desired amount of sulfur supplement is added to fresh feed stream 11 via stream 15. As the mixture 31 and hydrogen stream 22 pass through the catalyst bed 10, the fatty acids and fatty acid derivatives of the fresh feed stream 12 are converted to the corresponding reaction products. A two-phase stream 32 is withdrawn from the bottom of catalyst bed 10 and mixed with fresh feed stream 13, quench liquid stream 44, and hydrogen stream 23. The resulting vapor-liquid mixture 33, diluted in fresh feed concentrate, is subsequently directed onto the catalyst bed 20 at a reduced temperature due to the cooling effect of the hydrogen, quench liquid and fresh feed, passed through the catalyst bed 20 and finally withdrawn from the catalyst bed as product stream 34. Stream 34 is separated in high temperature separator 101 into vapor stream 35 and liquid stream 36. Vapor stream 35 is enriched in hydrogen and is directed to further processing. A portion of liquid stream 36 is returned to reactor 100 as recycle stream 40 and is further divided into a dilution stream 41 and a total quench liquid stream 42. Quench liquid stream 42 is cooled in heat exchanger 102 thereby providing sufficient cooling on top of catalyst beds 10 and 20. The hydrotreated product stream 51 is directed from the hydrotreating step to further processing.

The catalyst beds 10 and 20 may be located in the same pressure vessel or in separate pressure vessels. In embodiments where the catalyst beds are located in the same pressure vessel, hydrogen streams 22 and 23 may be alternately introduced onto catalyst bed 10 and subsequently passed through catalyst beds 10 and 20. In embodiments where the catalyst bed is located in a separate pressure vessel, the catalyst bed may be operated in parallel with separate dilution streams, hydrogen streams and quench liquid streams. The number of catalyst beds may be one or two or more.

The sulfur make-up for the hydrotreating step may be introduced with the fresh feed stream 11. Alternatively, when other sulfur components are employed, such as hydrogen sulfide, the desired amount of sulfur can be fed with hydrogen streams 22 and 23.

An excess of hydrogen over the theoretical hydrogen consumption is fed to the hydroprocessing reactor. During this hydrotreating step, the triglyceride oil, fatty acids and derivatives thereof are almost theoretically converted to n-alkanes with no or almost no side reactions. In addition, propane is formed from the glycerol moiety of the triglyceride, water and CO and/or CO are formed from the carboxyl oxygen₂Formation of H from organic sulfur compounds₂S and formation of NH from organic nitrogen compounds₃。

The use of the above procedure in the hydroprocessing step achieves the temperature required for reaction start-up at the beginning of each catalyst bed, limits the temperature rise in the catalyst bed, avoids harmful and partially converted intermediates, and greatly extends catalyst life. The temperature at the end of the catalyst bed is controlled by the net heat of reaction and the degree of diluent used. The diluent may be any available hydrocarbon of biological or non-biological origin. It may also be a product recycle. If a diluent is used, the fresh feed content in the total feed is less than 20 wt%. If product recycle is used, the product recycle/fresh feed ratio is in the range of from 5 to 30: 1, preferably from 10 to 30: 1, most preferably from 12 to 25: 1. After the hydrotreating step, the product is subjected to an isomerization step.

Isomerization of normal paraffins formed during hydroprocessing

In order to improve the cold properties of the product, it is necessary to carry out the isomerization of n-alkanes. Branched isoparaffins are formed during the isomerization. Isoparaffins may typically have mono-, di-, tri-or tetramethyl branches.

The product obtained in the hydrotreating step is isomerized under isomerization conditions with a catalyst. The feed to the isomerization reactor is a mixture of pure paraffins and the composition of the feed can be predicted from the fatty acid profile of each bio-oil used as feed to the hydrotreatment.

The isomerization step may include an optional purification step wherein the reaction product of the hydrotreating step may be purified by a suitable method such as stripping with steam or a suitable gas such as light hydrocarbons, nitrogen or hydrogen. Preferably, the acid gas and water impurities are removed as thoroughly as possible prior to contacting the hydrocarbons with the isomerization catalyst.

In the isomerization step, the pressure is varied in the range of 2-15MPa, preferably 3-10MPa, and the temperature is varied between 200-500 deg.C, preferably 280-400 deg.C.

In this isomerization step, an isomerization catalyst known in the art may be used. Suitable isomerization catalysts contain a molecular sieve and/or a metal selected from group VIII of the periodic table and/or a support. Preferably, the isomerization catalyst comprises SAPO-11 or SAPO-41 or ZSM-22 or ZSM-23 or ferrierite and Pt, Pd or Ni and Al₂O₃Or SiO₂. Typical isomerization catalysts are, for example, Pt/SAPO-11/Al₂O₃、Pt/ZSM-22/Al₂O₃、Pt/ZSM-23/Al₂O₃And Pt/SAPO-11/SiO₂. Most of these catalysts require the presence of hydrogen to reduce catalyst deactivation.

The isomerized diesel product consists predominantly of branched and linear hydrocarbons and has a melting point in the range of 180-350 ℃. In addition, some gasoline and gas are available.

THE ADVANTAGES OF THE PRESENT INVENTION

The process according to the invention provides a way to reduce the formation of higher molecular weight compounds during the hydrotreatment of fresh feeds, which may contain fatty acids and derivatives thereof. The process according to the invention provides for the selective production of diesel range hydrocarbons from bio-oils and fats with high diesel yields and without significant side reactions. With the aid of the promotion of the decarbonation reaction during hydrodeoxygenation, branched hydrocarbons can be produced from vegetable and vegetable oils and fats, as well as animal and fish oils and fats, and the hydrogen consumption is thereby reduced by 20-60%, typically 20-40%.

Oxygen is supplied as CO and CO during the deoxygenation of the feed by decarboxylation and/or decarbonylation₂And removing the form. The decarbonation reaction reduces the hydrogen consumption, theoretically about 60-70% throughout the entire deoxygenation, relative to the entire hydrodeoxygenation pathway, but is dependent on the triglyceride feedstock. C₁₂-C₁₆Fatty acids and their derivatives typically have a lower amount of double bonds and their decarboxylation tendency during hydrodeoxygenation is lower than higher carbon number fatty acids and their derivatives. However, it has surprisingly been found that when C is present in an amount of at least 20 wt%₁₂-C₁₆C when 50-20000w-ppm sulphur, calculated as elemental sulphur, is present in the feed of fatty acids and/or their derivatives₁₆Decarboxylation ratio C of fatty acids and derivatives thereof₁₈The fatty acids and their derivatives increased significantly more. This results in still lower hydrogen consumption. The addition of sulfur compounds to the hydrodeoxygenation feed facilitates control of catalyst stability and reduces hydrogen consumption. Like palm oil or animal fat feeds, contain more saturated fatty acid derivatives and produce less heat.

It was also found that there is a large amount of C₁₂-C₁₆The feeding of fatty acids and/or their derivatives reduces the hydrogen consumption in the isomerization step and also improves the cold properties of the diesel fuel. During the isomerization of normal paraffins, the yield of diesel range hydrocarbons is particularly increased due to less cracking of normal paraffins formed from the hydrotreated fatty acid derivative feed. C formed during hydrotreating₁₁-C₁₆N-alkanes inLower conversion and lower reaction temperatures are required during isomerization, thereby maintaining the same diesel cooling performance and thereby significantly reducing the extent of cracking and coke formation relative to heavier n-alkanes. Alternatively, improved cold performance can be obtained at the same reaction temperature without yield loss. The stability of the catalyst during hydrotreating and isomerization increases.

The invention is illustrated below by means of examples showing some preferred embodiments of the invention. However, it is obvious to those skilled in the art that the scope of the present invention is not limited to these examples.

Examples

Example 1 Effect of the Sulfur content of the Total feed

Palm oil containing 0.3 area% (area-%) free fatty acids was used as fresh feed, together with the product recycle at 5: 1, in the presence of hydrogen. In the fresh feed C₁₂-C₁₆The content of fatty acid triglyceride was 58.3 wt%. The total feed contains less than 10w-ppm alkali and alkaline earth metals, calculated as elemental alkali and alkaline earth metals. The amount of other metals in the feed is less than 10w-ppm based on elemental metal. The amount of phosphorus is less than 30w-ppm based on elemental phosphorus.

During the test runs, different amounts of dimethyl disulfide were used in the total feed. The reaction temperature was 305 ℃, the reactor pressure was 5MPa and the space velocity was 0.5g/g for fresh feed. Higher sulfur content in the feed significantly increased the passage of CO and CO₂Instead of deoxygenation by hydrogen (HDO, which produces n-alkanes with the same number of carbon atoms as the original fatty acids), is subjected to a total deoxygenation reaction (decarbonation reaction, which produces n-alkanes with one less carbon atom relative to the original fatty acids). However, C₁₆Decarburization reaction ratio C of fatty acid₁₈Or C₂₀The decarbonization reaction of the fatty acid is significantly increased more. The high content of sulphur in the feed reduces the double bond hydrogenation activity of the catalyst and also reduces the decarbonation reaction, as can be seen in table 1That way, the effect of the sulfur content of the total feed, calculated as elemental sulfur, on the% decarbonization of the fatty acids with different numbers of carbon atoms observed in the product oil is given (decarbonization% calculated from the fresh feed). Table 2 discloses the relative increase in the decarbonation reaction relative to the feed with 100w-ppm sulfur, and table 3 gives the theoretical reduction in hydrogen consumption due to the decarbonation reaction.

TABLE 1 influence of the sulphur content of the total feed, calculated as elemental sulphur

TABLE 2 relative increase in decarburization reaction

TABLE 3 theoretical hydrogen consumption with and without decarbonation

Example 2 feeding with palm oil C₁₆Effect of fatty acids on cracking during isomerization and Diesel yield at the same pour Point level

A catalyst containing 44.8% by weight of C was used in the fresh feed₁₂-C₁₆Palm oil of fatty acid triglycerides. Dimethyl disulphide is added to palm oil to obtain a sulphur content in the feed of about 600w-ppm, calculated as elemental sulphur. The feed purity was the same as in example 1, but the free fatty acid content was 0.2 area%. No diluent is used. The feed was hydrotreated in the presence of hydrogen at 305 ℃ with a reactor pressure of 5MPa and a space velocity of 2g/g for fresh feed. The product contains mainly n-alkanes. Feeding the n-alkane intoThe batch was isomerized at 317 ℃ under 4MPa and a WHSV of 3 l/h in the presence of hydrogen. Catalyst (A) contains Pt, SAPO-11 and an alumina support. In the product, > C₁₀The hydrocarbon content was 97 wt%. The cloud point of the liquid product was-22 ℃. The results of the analysis of the product are provided in table 4.

A rapeseed oil feed was used for the comparative tests. Rapeseed oil contained 4.5% by weight of C₁₂-C₁₆Fatty acid triglycerides. Rapeseed oil was hydrotreated and isomerized under the same reaction conditions as described above. In the product, > C₁₀The hydrocarbon content was 96 wt%. The cloud point of the liquid product was-15 ℃. The results of the analysis of the product are provided in table 4.

Example 3C with palm oil feed at the same Diesel yield₁₆Effect of fatty acids on pour Point of isomerized Diesel

The hydrotreated palm oil obtained in example 2 was isomerized at 312 ℃, 4MPa and a WHSV of 3 l/h in the presence of hydrogen using catalyst a. This produced a liquid product with a cloud point of-14 ℃. In the product, > C₁₀The hydrocarbon content is then 98% by weight. Small amounts of light hydrocarbons can be deduced from the flash point neutralization of the product and in the distillation curve, as can be seen in table 4, which gives the analysis results of the hydrotreated and isomerized products obtained from rapeseed oil and palm oil, and HRO ═ hydrotreated rapeseed oil and HPO ═ hydrotreated palm oil.

Table 4 analysis results of hydrotreated and isomerized products obtained from rapeseed oil and palm oil

Example 4 feeding with animal fat C₁₆Effect of fatty acids on cracking during isomerization and Diesel yield at the same pour Point level

Using a catalyst containing 30 wt% of C₁₂-C₁₆Fatty acid glycerolTriester animal fats as fresh feed. The feed contains alkali and alkaline earth metals in an amount of less than 10w-ppm based on elemental alkali and alkaline earth metals. The content of other metals in the feed is below 10w-ppm calculated as elemental metals. The phosphorus content is less than 30w-ppm calculated as elemental phosphorus. Dimethyl disulfide was added to animal fat to obtain a sulfur content of about 100w-ppm in the feed. The fresh feed contained 0.6 vol% free fatty acids. The feed was hydrotreated in the presence of hydrogen at 300 ℃ with a reactor pressure of 5MPa and a space velocity of 2g/g for fresh feed, without using any diluent. The product contains mainly n-alkanes. The n-alkane feed was isomerized at 316 ℃, 4MPa and a WHSV of 1.5 liters/hour in the presence of hydrogen. Catalyst (B) contains Pt, SAPO-11 and an alumina support. In the product, > C₁₀The hydrocarbon content was 95 wt%. The cloud point of the liquid product was-20 ℃.

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 C₁₂-C₁₆Fatty acid triglycerides. In the isomerized product, > C₁₀The hydrocarbon content was 95 wt%. The cloud point of the liquid product was-14 ℃.

Example 5 use of animal fat feed at the same Diesel yield C₁₆Effect of fatty acids on pour Point of isomerized Diesel

The hydrotreated animal fat obtained in example 4 was isomerized at 312 ℃, 4MPa and a WHSV of 1.5 liter/hr in the presence of hydrogen, using catalyst B. This produced a liquid product with a cloud point of-13 ℃. The content of hydrocarbons > C10 is then 98 wt.%.

Claims (28)

1. Process for the preparation of diesel range hydrocarbons wherein a feed is hydrotreated in a hydrotreating step and isomerised in an isomerisation step, characterised in that the feed comprises hydrocarbons containing at least 20 wt% of C₁₂-C₁₆Fatty acid triglyceride or C₁₂-C₁₆Fatty acid esters or C₁₂-C₁₆A fresh feed of fatty acids or combinations thereof and the total feed contains 100-10000w-ppm sulphur calculated as elemental sulphur, wherein at least one inorganic or organic sulphur compound or a refinery gas and/or liquid stream containing sulphur compounds is added to the feed.

2. Process according to claim 1, characterized in that the fresh feed contains at least 30 wt% of C₁₂-C₁₆Fatty acid triglycerides or other fatty acid esters, or combinations thereof.

3. Process according to claim 2, characterized in that the fresh feed contains at least 40 wt% C₁₂-C₁₆Fatty acid triglycerides or other fatty acid esters, or combinations thereof.

4. The process according to claim 1, characterized in that the fresh feed contains more than 5 wt% free fatty acids.

5. The process of claim 1, characterized in that the feed contains less than 10w-ppm alkali and alkaline earth metals, calculated as elemental alkali and alkaline earth metals, less than 10w-ppm other metals, calculated as elemental metals, and less than 30w-ppm phosphorus, calculated as elemental phosphorus.

6. Process according to any one of claims 1, 4 or 5, characterized in that the feed comprises less than 20 wt% of fresh feed and additionally at least one diluent.

7. Process according to claim 6, characterized in that the diluent is a diluent selected from hydrocarbons and recycled products of the process or mixtures thereof, and the diluent/fresh feed ratio is 5-30: 1.

8. The process according to claim 7, characterized in that the diluent is a diluent selected from the group consisting of hydrocarbons and recycled products of the process or mixtures thereof, and the diluent/fresh feed ratio is 10-30: 1.

9. The process according to claim 8, characterized in that the diluent is a diluent selected from the group consisting of hydrocarbons and recycled products of the process or mixtures thereof, and the diluent/fresh feed ratio is 12-25: 1.

10. The process as claimed in claim 1, characterized in that the feed contains 1000-8000w-ppm of sulfur, calculated as elemental sulfur.

11. The process as claimed in claim 10, characterized in that the feed contains 2000-5000w-ppm of sulfur, calculated as elemental sulfur.

12. Process according to any one of claims 1, 4 or 5, characterized in that the fresh feed is of biological origin, selected from the group consisting of vegetable oils/fats, animal fats/oils, fish fats/oils, fats contained in plants grown by means of genetic manipulation, recovered fats of the food industry and mixtures thereof.

13. The method according to claim 12, characterized in that the fresh feed is selected from the group consisting of rapeseed oil, rape oil, tall oil, sunflower oil, soya oil, hemp oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, lard, tallow, whale oil or fats contained in milk or mixtures thereof.

14. A method according to claim 13, characterized in that the rapeseed oil is canola oil.

15. Process according to any one of claims 1, 4 or 5, characterized in that the fresh feed comprises feed of biological origin and hydrocarbons.

16. The process according to any one of claims 1, 4 or 5, characterized in that a catalyst bed system comprising one or more catalyst beds is used in the hydrotreating step.

17. The process as claimed in any of claims 1, 4 or 5, characterized in that in the hydrotreating step the pressure is varied in the range from 2 to 15MPa and the temperature is varied between 200 and 400 ℃.

18. The process as claimed in claim 17, characterized in that, in the hydrotreating step, the pressure is varied in the range from 3 to 10MPa and the temperature is varied between 250 ℃ and 350 ℃.

19. The process as claimed in claim 18, characterized in that the temperature is varied between 280 ℃ and 345 ℃ in the hydrotreating step.

20. Process according to any one of claims 1, 4 or 5, characterized in that in the isomerization step the pressure is varied in the range of 2-15MPa and the temperature is varied between 200 ℃ and 500 ℃.

21. The process as claimed in claim 20, characterized in that, in the isomerization step, the pressure is varied in the range from 3 to 10MPa and the temperature is varied between 280 ℃ and 400 ℃.

22. The process according to claim 17, characterized in that the hydrotreating is carried out in the presence of a hydrogenation catalyst comprising a metal selected from groups VIII and/or VIB of the periodic table.

23. The process of claim 22, characterized in that the hydrotreating catalyst is a supported Pd, Pt, Ni, NiMo or CoMo catalyst and the support is alumina and/or silica.

24. The process according to claim 20, characterized in that an isomerization catalyst containing a molecular sieve is used in the isomerization step.

25. The process of claim 24, characterized in that the isomerization catalyst comprises a metal of a group VIII element.

26. The process of claim 24 or 25, characterized in that the isomerization catalyst contains Al₂O₃Or SiO₂。

27. The process of any of claims 24 to 25, characterized in that the isomerization catalyst comprises SAPO-11 or SAPO-41 or ZSM-22 or ZSM-23 or ferrierite and Pt or Pd or Ni and Al₂O₃Or SiO₂。

28. The process of claim 26, characterized in that the isomerization catalyst comprises SAPO-11 or SAPO-41 or ZSM-22 or ZSM-23 or ferrierite and Pt or Pd or Ni and Al₂O₃Or SiO₂。