HK1128038B - Process for the manufacture of hydrocarbons - Google Patents

Description

Process for producing hydrocarbons

Technical Field

The present invention relates to a process for producing hydrocarbons, in particular branched hydrocarbons, from renewable sources and to a process for producing hydrocarbons suitable for use in diesel fuel pools. The process comprises a skeletal isomerization step and a deoxygenation step by decarboxylation/decarbonylation or hydrodeoxygenation.

Background

Fatty acids have been used in the chemical industry as raw materials in a variety of applications, typically for the production of products ranging from lubricants, polymers, fuels and solvents to cosmetics. Fatty acids are generally obtained from wood pulping processes or from the hydrolysis of triglycerides of vegetable or animal origin. Naturally occurring triglycerides are generally esters of glycerol and straight chain, even-numbered carboxylic acids having from 10 to 26 carbon atoms. The most common fatty acids contain 16, 18, 20 or 22 carbon atoms. The fatty acids may be saturated or they may contain one or more unsaturated bonds. Unsaturated fatty acids are typically olefinic with a cis configuration of carbon-carbon double bonds. The unsaturated center is present in the preferred position of the carbon chain. The most common position is ω 9, as in oleic acid (C18:1) and erucic acid (C22: 1). Polyunsaturated acids typically have a cis-olefinic double bond arrangement with methylene interruptions.

Saturated long straight chain fatty acids (C10:0 and above) are solid at room temperature, which makes them difficult to process and use in many applications. Unsaturated long chain fatty acids such as oleic acid are liquids that are easily processed at room temperature, but they are unstable due to double bonds.

Branched fatty acids have properties in many respects similar to linear unsaturated fatty acids, but they are more stable. For example, a branched C18:0 fatty acid known as isostearic acid is liquid at room temperature, but it is not as unstable as a C18:1 acid because there are no unsaturated bonds in the branched C18: 0. Thus, branched fatty acids are more desirable than straight chain fatty acids in many applications.

Diesel fuels based on biological materials are generally referred to as biodiesel. The definition of "biodiesel" provided in the Original Equipment Manufacturer (OEM) guidelines is as follows: biodiesel is a mono-alkyl ester of long chain fatty acids obtained from vegetable oils or animal fats, consistent with ASTM D6751 or EN 14214 specifications used in diesel engines described in table 1 below. Biodiesel refers to pure fuel (B100) before being mixed with diesel fuel.

TABLE 1 specification for biodiesel (B100, 100%)

Properties ASTM D6751 EN 14214 units

Density of 860 ℃ and 900 kg/m at 15 DEG C³

A flash point (closed cup) of 130 ℃ or more

Water and sediment less than or equal to 0.050% and less than or equal to 0.050%

Kinematic viscosity of 1.9-6.03.5-5.0 mm at 40 DEG C²/s

Sulfated ash content of 0.020-0.020 wt%

Sulfur content of 0.05-0.001 wt%

The cetane number is not less than 47 and not less than 51

Less than or equal to 0.050 percent of carbon slag by mass

10% of bottom fraction of the tower contains carbon residue not more than 0.3% by mass

The acid value is less than or equal to 0.80 and less than or equal to 0.5 mg KOH/g

Free glycerin not more than 0.020 not more than 0.02% by mass

Less than or equal to 0.240 and less than or equal to 0.25 percent of total glycerin by mass

Phosphorus content of not more than 0.001 and not more than 0.001 wt%

Good diesel fuels need to have a high cetane number, a suitable viscosity range and good low temperature properties. The Cetane Number (CN) established forThe ignition properties of diesel fuel or its components are described. Branching and chain length affect CN, which decreases with decreasing chain length and increasing branching. Hexadecane C₁₆H₃₄CN of (2) is 100, and 2, 2, 4, 4, 6, 8, 8-heptamethylnonane C₁₆H₃₄Has a CN of 15. The double bonds also reduce CN by structural features. In addition, unsaturated compounds can cause engine gelling.

In addition to CN, the total heat of combustion (HG) of the compounds is essential for the suitability of the compounds for use as diesel fuel. HG comparisons of paraffinic biodiesel and ester biodiesel were as follows: the HG for hexadecane was 2559kg cal/mol at 20 ℃ and the HG for methyl palmitate (C16:0) was 2550kg cal/mol.

Cloud point refers to the temperature at which a petroleum product just exhibits a cloud or haze of wax crystals when cooled under standard test conditions as described in the ASTM D2500 standard. Cloud point measures the ability of the fuel used to not clog filters and supply lines in cold climates.

The flow point is the lowest temperature at which the fuel just flows when tested under conditions as described in the ASTM D97 standard. Engine manufacturers recommend that the cloud point should be below the use temperature and not exceed the pour point by more than 6 ℃. Branching, saturation and chain length also affect cloud point and flow point, and they decrease with decreasing chain length, increasing unsaturation and increasing branching.

The viscosity of vegetable oils is about an order of magnitude greater than conventional diesel fuels. High viscosity results in poor atomization in the combustion chamber, thereby causing nozzle coking and deposits.

Biodiesel is an alternative fuel produced from renewable sources and it does not contain petroleum. It can be blended with petroleum diesel in small amounts to produce biodiesel blends, and in addition it is non-toxic and essentially free of sulfur and aromatics. It can be used in compression-ignition (diesel) engines with little or no modification.

Diesel fuels based on biological materials have proven to have significant environmental benefits in terms of reduced global warming impact, reduced emissions, greater energy independence and positive impact on agriculture.

It has been demonstrated that the use of diesel fuels based on biological materials will result in a significant reduction in carbon dioxide emissions. The life cycle study of biodiesel, initiated by the U.S. department of energy and the U.S. department of agriculture in 1998, concluded that biodiesel, compared to petroleum diesel, results in pure CO₂The emission was reduced by 78%. This is due to the closed carbon cycle of biodiesel. CO released to the atmosphere when biodiesel is combusted₂Is circulated by the growing plants and subsequently processed into fuels. Thus, increasing the use of diesel fuels based on biomaterials represents an important step in meeting the emission reduction goals achieved under the kyoto agreement. It is also believed that the reduction of particulate emissions and other harmful emissions, such as nitrogen oxides, alleviates human health problems.

Methyl esters of long chain acids have higher cloud and pour points than the corresponding triglycerides and conventional diesel fuels. Cloud point and flow point are important characteristics when the engine is operating in a cooler environment.

Several methods have been proposed for obtaining diesel fuels from vegetable oils and other triacylglycerol-based feedstocks, such as transesterification, dilution, microemulsification, and co-solvent blending and cracking. The aim of the process is to reduce the high kinematic viscosity of pure vegetable oils, which can lead to serious operational problems and unsuitable fuel atomization.

In the transesterification, triglycerides, which are the main components of vegetable oils, are converted into the corresponding esters using alcohols in the presence of a catalyst. Methanol is the most commonly used alcohol due to its low cost and ease of separation from the resulting methyl ester and glycerol phases.

Dilution of vegetable oils by 0-34% with conventional diesel fuel results in proper atomization but causes similar problems to engines using pure vegetable oils.

The microemulsified fuel consists of conventional diesel fuel and/or vegetable oil, a single alcohol, an amphiphilic compound such as a surfactant and a cetane improver. Trace amounts of water are usually required for the formation of microemulsions.

Cracking processes, Kolbe electrolysis and thermocatalytic cracking of biological materials such as vegetable oils, their methyl esters and animal fats result in the production of a wide range of products such as alkanes, alkenes, aromatics and carboxylic acids. The reaction is generally non-selective and also forms less valuable by-products.

The unsaturated aromatic hydrocarbons present in the liquid fraction make the products obtained by the above-described process unsatisfactory for use in diesel pools. The poor low temperature properties of the products limit their widespread use as biodiesel in colder climate conditioned areas. In addition, the presence of oxygen in the ester results in the production of undesirably higher Nitrogen Oxides (NO) than conventional diesel fuel_x) And (5) discharging.

Sulfur-free fuels are needed in order to obtain the full effect of new and effective anti-pollution technologies in modern vehicles, and to reduce emissions of nitrogen oxides, volatile hydrocarbons and particulates, as well as to achieve direct reduction of sulfur dioxide in exhaust gases. The european union has promulgated that these products must be commercially available from 2005 and must be the only form to be sold from 2009. These new requirements will reduce annual sulfur emissions from automotive fuels.

Patent US 5,856,539 discloses the obtaining of branched fatty acids and branched fatty acid esters, mainly methyl and ethyl esters, by isomerization of linear unsaturated fatty acids and linear unsaturated fatty acid esters having the corresponding chain length. For example, branched C18:0 acids are prepared from straight chain C18:1 acids or also from C18:2 acids.

Maier, w.f. et al: chemische Berichte (1982), 115(2), 808-12, teaches decarboxylation of carboxylic acids to hydrocarbons by contacting the carboxylic acid with a heterogeneous catalyst. They tested Ni/Al for decarboxylation of some carboxylic acids₂O₃And Pd/SiO₂A catalyst. During the reaction, the vapors of the reactants, together with hydrogen, pass through the catalytic bed at 180 ℃ and 0.1 MPa. Hexane represents the main product of decarboxylation of heptanoic acidAnd (5) preparing the product. When nitrogen is used instead of hydrogen, no decarboxylation is observed.

US 4,554,397 discloses a process for the production of linear olefins from saturated fatty acids or esters by decarboxylation using a catalytic system consisting of nickel and at least one metal selected from lead, tin and germanium. The catalyst may contain additives such as sulfur derivatives to reduce the hydrogenation capacity of the nickel and to make the reaction more selective for olefin formation. The presence of hydrogen is necessary to maintain the activity of the catalyst. The reaction is carried out at a temperature of 300 ℃ and 380 ℃ and at a pressure of atmospheric pressure or higher.

Decarboxylation with hydrogenation of oxy compounds is described in Laurent, e., Delmon, b.: applied Catalysis, a: general (1994), 109(1), 77-96 and 97-115, in which the sulfur-containing CoMo/Al is described₂O₃And NiMo/Al₂O₃Hydrodeoxygenation of biomass-derived pyrolysis oils over catalysts was investigated. The hydrotreating conditions were 260 ℃ and 300 ℃ and 7MPa in hydrogen. The decarboxylation is promoted by the presence of hydrogen sulfide, particularly when a NiMo catalyst is used.

The unsaturated aromatic hydrocarbons produced in the side reactions of the above-mentioned processes make the products obtained unsatisfactory for use in diesel pools. Furthermore, the unbranched and highly saturated structure leads to poor low temperature performance.

FI 100248 discloses a two-step process for the production of middle distillates from vegetable oils by the following steps: the normal paraffins are obtained by hydrogenating fatty acids or triglycerides of vegetable oils using commercially available desulfurization catalysts (NiMo and CoMo) and then isomerizing them using metals containing molecular sieves or zeolites to obtain branched paraffins. The hydrotreatment is carried out at a reaction temperature of 330 ℃ and 450 ℃.

Based on the above, it can be seen that there is a need for new alternative processes for the preparation of saturated branched hydrocarbons from renewable sources, suitable for use as high quality biodiesel.

Object of the Invention

One object of the present invention is a process for producing branched saturated hydrocarbons from renewable sources.

Another object of the invention is a process for producing branched saturated hydrocarbons suitable for use in diesel fuel pools.

The method according to the invention is characterized in the claims.

Definition of

Skeletal isomerization is understood to mean the formation of branches on the main carbon chain, while the carbon number of the compound does not change.

Deoxygenation is understood to mean the removal of carboxyl oxygen, such as fatty acid or fatty acid ester oxygen. Deoxygenation may be performed by Hydrodeoxygenation (HDO) or decarboxylation/decarbonylation.

Decarboxylation/decarbonylation is understood to mean the passage of CO₂(decarboxylation) and/or removal of the carboxyl oxygen by CO (decarbonylation).

Hydrodeoxygenation (HDO) refers to the removal of oxygen as water using hydrogen.

The term "branched fatty acid" is understood herein to include fatty acids containing one or more alkyl side groups which may be attached to the carbon chain at any position. The alkyl group is typically C₁-C₄An alkyl chain.

Pressure is understood here to mean an overpressure above atmospheric pressure.

Summary of The Invention

The present invention relates to a catalytic process for the production of branched saturated hydrocarbons suitable for use in diesel fuel pools from renewable sources such as plant, vegetable, animal and fish oils and fatty acids. The present invention relates to the conversion of a feedstock comprising fatty acids or esters of fatty acids with lower alcohols into branched fatty acids or fatty acid esters using an acidic catalyst and then converting the resulting branched fatty acids or fatty acid esters into branched hydrocarbons by contact with a heterogeneous decarboxylation/decarbonylation catalyst or with a hydrodeoxygenation catalyst.

The branched hydrocarbon product formed via the decarboxylation/decarbonylation reaction has one carbon atom less than the starting fatty acid, and the branched hydrocarbon product formed via the hydrodeoxygenation reaction has a carbon atom number equal to that of the starting fatty acid.

In this process, a minimum amount of hydrogen is used, resulting in a high quality hydrocarbon product with good low temperature properties and a high cetane number.

Detailed Description

It has now surprisingly been found that saturated branched hydrocarbons suitable for use in biodiesel fuels can be obtained from oxygenated feedstocks derived from renewable sources by skeletal isomerization followed by removal of oxygen using deoxygenation by decarboxylation/decarbonylation or hydrodeoxygenation.

In a first treatment step, a feedstock comprising unsaturated fatty acids or esters of unsaturated fatty acids with lower alcohols or mixtures thereof is skeletally isomerized, where they are isomerized to fatty acids or fatty acid alkyl esters containing short alkyl branches in their carbon chains. In a subsequent process step, the branched product is deoxygenated. Deoxygenation is carried out by decarboxylation/decarbonylation, wherein oxygen is supplied as CO and CO₂Is removed as hydrogen, or the deoxygenation is carried out by hydrodeoxygenation, in which the oxygen is in the form of H₂The O form is removed from the isomerized fatty acid or fatty acid alkyl ester. The process may also include an optional pre-hydrogenation step prior to the deoxygenation step to eliminate unsaturation after skeletal isomerization and to liberate lower alcohols in the hydrodeoxygenation.

The process according to the present invention provides a convenient method for producing branched chain hydrocarbons from fatty acids or esters of fatty acids and lower alcohols. The fatty acids and fatty acid esters are derived from biological sources such as vegetable, animal and fish oils.

Raw materials

The raw material comprises fatty acid or fatty acid and C₁-C₅Preferably C₁-C₃Esters of alcohols, or mixtures thereof. The material is preferably derived from biological materials such as plants, vegetables, animalsAnd fish oil. The biological raw material may be treated using any pretreatment or purification method known in the art, such as hydrolysis, etc., to obtain fatty acids or fatty acid esters suitable for use as feedstock. The starting material comprises at least 20% by weight, preferably at least 50% by weight and particularly preferably 80% by weight of unsaturated fatty acids or fatty acid esters. The feedstock may also comprise a mixture of fatty acids and fatty acid esters, but preferably fatty acids or fatty acid esters are used.

The unsaturated fatty acid used as the raw material is a fatty acid having an unsaturated bond and a total carbon number of 8 to 26, preferably 12 to 20 and particularly preferably 12 to 18. For the degree of unsaturation, i.e., the number of unsaturated carbon-carbon bonds, any unsaturated fatty acid can be used, so long as one or more unsaturated carbon-carbon bonds are present in the molecule.

The feedstock may comprise C of unsaturated fatty acids₁-C₅Preferably C₁-C₃Alkyl esters having a total carbon number of from 8 to 26, preferably from 12 to 20 and particularly preferably from 12 to 18, corresponding to the above-mentioned unsaturated fatty acids. Examples of suitable alkyl esters include the methyl, ethyl and propyl esters of the unsaturated fatty acids, preferably the methyl ester.

Typically, the number of unsaturated bonds in the starting material is from 1 to 3. Preferably the feedstock comprises at least 40% by weight of monounsaturated fatty acids or fatty acid esters, more preferably at least 70% by weight. The feedstock may also include polyunsaturated fatty acids or fatty acid esters. The presence of unsaturated bonds in the molecule results in the formation of cationic intermediates, thereby facilitating skeletal isomerization reactions.

Skeletal isomerization

In the first step of the process according to the invention, branched fatty acids or fatty acid alkyl esters are prepared. The previously described feedstock is subjected to a skeletal isomerization step. The skeletal isomerization is carried out using an acidic catalyst at a temperature of 150-400 ℃ and a pressure of 0-5MPa, preferably at 200-350 ℃ and 0.1-5MPa and particularly preferably at 220-300 ℃ and 0.1-2 MPa. Suitable acidic catalysts are silicoaluminophosphates and zeolites, preferably faujasite, offretite (offertite), montmorillonite and mordenite. A particularly preferred catalyst is mordenite.

Water or a lower alcohol may be added to the raw material to suppress the formation of acid anhydride due to dehydration or dealcoholization. Water is preferably added when the feedstock comprises unsaturated fatty acids and alcohol is preferably added when the feedstock comprises unsaturated fatty acid esters. Typical amounts of water or lower alcohol added are from 0 to 8%, and preferably from 1 to 3% by weight, based on the total reaction mixture. The lower alcohol is C₁-C₅Alcohols, and preferred alcohols are methanol, ethanol and propanol, more preferably alcohols having the same alkyl group as the starting fatty acid ester to be isomerized. Too much water (more than 10%) should be avoided to avoid anhydride formation. The skeletal isomerization step may also be carried out in the absence of water or lower alcohols.

The skeletal isomerization step may be carried out in a closed batch reactor at reaction pressure. This is to prevent vaporization of water, alcohols and other low boiling point materials in the system, including those contained in the catalyst. The reaction time is preferably less than 24 hours, more preferably less than 12 hours and most preferably less than 30 minutes.

In general, the amount of catalyst used in the process is from 0.01 to 30% by weight, preferably from 1 to 10% by weight, based on the total reaction mixture.

When a continuous flow reactor is used, the space velocity WHSV is in the range of from 0.1 to 100l/h, more preferably from 0.1 to 50l/h and most preferably from 1 to 10 l/h.

The product from the skeletal isomerization step contains saturated as well as unsaturated branched fatty acids or fatty acid esters. Possible by-products are cyclic acids and polymerized fatty acids, such as dimer acids, and polymerized fatty acid esters when the feedstock includes unsaturated fatty acid esters. The resulting branched compounds generally have short alkyl branches, from 1 to 4 carbon atoms in length, and they are obtained as a mixture of many isomers with different branching positions.

Preferably, the resulting branched fatty acids or fatty acid esters are separated from the dimer acid, for example by distillation, their unsaturated bonds are prehydrogenated, and then separated from the linear saturated alkyl fatty acids or esters thereof by solvent fractionation. The order of distillation, pre-hydrogenation and fractionation may be varied. The distillation and solvent fractionation steps may also be carried out at the end of the process after deoxygenation.

Optionally the skeletal isomerization product may be pre-hydrogenated in order to eliminate unsaturations which may lead to coke formation on the catalyst surface in a subsequent catalytic step. The prehydrogenation is carried out in the presence of a hydrogenation catalyst at a temperature of from 50 to 400 ℃ and under a hydrogen pressure of from 0.1 to 20MPa, preferably at from 150 ℃ to 250 ℃ and from 1 to 10 MPa. The heterogeneous hydrogenation catalyst comprises one or more group VIII and/or group VIA metals. The hydrogenation catalyst is preferably a Pd, Pt, Ni, NiMo or CoMo catalyst on an aluminium and/or silica support.

In the case of fatty acid esters used as feedstock in the isomerization step, the branched products from skeletal isomerization may optionally be pre-hydrogenated prior to the final deoxygenation step, thereby saturating the double bonds and liberating the lower alcohols used in the esterification. The fatty acid alkyl esters are converted to fatty alcohols for hydrodeoxygenation. The free lower alcohol may be recovered after distillation. The fatty acid alkyl esters are prehydrogenated using a metal catalyst at a hydrogen pressure of 25-30MPa and at a temperature of 200-230 ℃. The metal catalyst is preferably a copper-chromite catalyst or a chromium-, ferrous-or rhodium-activated nickel catalyst.

Deoxidation

The branched products obtained from the skeletal isomerization step are then subjected to deoxygenation by decarboxylation/decarbonylation or hydrodeoxygenation.

In a first embodiment, a saturated branched fatty acid or fatty acid ester and optionally a solvent or solvent mixture are contacted with a heterogeneous decarboxylation/decarbonylation catalyst selected from supported catalysts comprising one or more metals of group VIII and/or group VIA of the periodic table of elements. Preferably, the decarboxylation/decarbonylation catalyst is a supported Pd, Pt, Ni, NiMo or CoMo catalyst, the support being alumina and/or silica and/or carbon. Particular preference is given to using Pd on carbon and NiMo sulfide on alumina. Optionally, hydrogen may be used. The decarboxylation/decarbonylation reaction conditions vary depending on the starting materials used. The reaction is carried out in the liquid phase. The decarboxylation/decarbonylation reaction is carried out at a temperature of 100 ℃ to 400 ℃, preferably 250 ℃ to 350 ℃. The reaction may be carried out at atmospheric pressure. However, in order to keep the reactants in the liquid phase, it is preferred to use a pressure higher than the saturated vapour pressure of the starting materials at the given temperature, and thus the reaction pressure is from atmospheric to 20MPa and preferably from 0.1 to 5MPa of an inert gas/hydrogen mixture. The product obtained from this embodiment is a mixture of hydrocarbons, preferably having a boiling point of 180-.

In a second embodiment, in the hydrodeoxygenation step, the branched fatty acids or esters thereof resulting from the skeletal isomerization step, or the fatty alcohols resulting from the optional pre-hydrogenation step, and optionally a solvent or solvent mixture are contacted with an optionally pre-treated heterogeneous hydrogenation catalyst, said catalyst being a catalyst containing a metal selected from group VIII and/or group VIA of the periodic table of the elements, as known in the art for hydrodeoxygenation. Preferably, the hydrodeoxygenation catalyst is a supported Pd, Pt, Ni, NiMo or CoMo catalyst, the support being alumina and/or silica and/or carbon. Particular preference is given to using NiMo/Al₂O₃And CoMo/Al₂O₃A catalyst. In the hydrodeoxygenation step, the pressure range may vary between 1 and 20MPa, preferably between 2 and 10MPa, and the temperature is 200-500 ℃, preferably 250-350 ℃.

The optional solvent in each deoxygenation embodiment may be selected from hydrocarbons such as paraffins, isoparaffins, naphthenes and aromatic hydrocarbons having a boiling range of 150-350 c and a recycle process stream comprising hydrocarbons and mixtures thereof is used, preferably a recycle product stream obtained from the process according to the present invention.

Product(s)

The process according to the invention produces branched paraffins suitable for use in diesel fuel pools. The product typically contains some short carbon-carbon branches, resulting in particularly lower cloud points and cold filter plugging points than the products obtained by known processes, but still having good cetane numbers. In table 2, the properties of the product (1) produced using the process according to the invention are compared with the products (2-6) obtained according to the state of the art process. All products were 100% (B100) diesel components.

Table 2.

Performance of	Product 1	Product 2	Product 3	Product 4	Product 5	Product 6
							kV40mm2/s	2.4-4.4	2.9-3.5	4.5	3.2-4.5	2.0-4.5	1.2-4.0
Cloud Point deg.C	-29--42	-5--30	-5	0--25		-10--34
							Flash point PMcc, DEG C	67-141	52-65			≥55
Cold filter plugging point, deg.C	-31--45	-15--19			≤+5--20	≤-20--44
							iQT cetane number	60-93	84-99	51	73-81	≥51	≥51
Sulfur ppm in	＜10	＜10	＜10	＜10	＜10	＜10
							Density 15 ℃ kg/m3	799-811	775-785	885	770-785	820-845	800-840
Fraction 10%	195-286	260-270	340	260		180
							90％	301-337	295-300	355	325-330
95％	312-443				360	340

The products of table 2 were prepared as follows:

prepared by skeletal isomerization and deoxygenation of fatty acids according to the process of the present invention

Preparation of (2) by hydrodeoxygenation and hydroisomerization of triglycerides

(3) fatty acid methyl ester prepared by transesterification of rapeseed oil

(4) is a natural gas-based diesel fuel produced by a gas-liquid and hydroisomerization process

(5) and (6) mineral oil based Diesel fuels of different specifications for use in Arctic environments

The structure of the branched saturated hydrocarbon product obtained using the process according to the invention is different from that obtained, for example, when hydroisomerizing C16-C22 conventional paraffins. In the case of the present invention, the branching is mainly in the middle of the long carbon chain due to the branching of the usual omega 9 olefinic unsaturation. In hydroisomerized isoparaffins, the branches are mainly located near the ends of the carbon backbone. The carbon number of the hydrocarbon product of the invention is C13-C22, typically C15-C18, and can be adjusted in the product by varying the hydrodeoxygenation and/or decarboxylation/decarbonylation reaction conditions.

The branched saturated hydrocarbon product comprises greater than 80 vol-%, typically greater than 99 vol-% paraffins.

The branched saturated hydrocarbon product comprises less than 30 wt% of normal paraffins, typically less than 15 wt%.

According to the process of IP-391, the branched saturated hydrocarbon product comprises less than 20 vol-%, typically less than 10 vol-% aromatics.

The biodiesel component also comprises¹⁴C isotopes, which can be used as a basis for fuel biological sources. Typical branched saturated hydrocarbon product compared to the radioactive carbon content of air in 1950¹⁴The C content is at least 100% by weight of the radioactive carbon content.

The method according to the invention has several advantages. Using this method, a branched saturated hydrocarbon product comprising branches and suitable for use in diesel fuel pools is obtained from renewable sources. Due to the absence of unsaturation in the hydrocarbon product, the oxidative stability is good and the polymerization tendency is low compared to conventional fatty acid methyl ester based biodiesel compounds.

Branches in the alkane carbon chains enhance low temperature properties such as cloud point, pour point, and cold filter plugging point. The very good low temperature properties enable the branched saturated hydrocarbon product to be used as a diesel fuel or a diesel fuel component in arctic fuels as well.

The branched chain saturated hydrocarbon product produced according to the present invention is intended for use in a compression ignition engine in which air is compressed until it is heated above the auto-ignition temperature of diesel fuel and then the fuel is injected as a high pressure spray, maintaining the fuel-air mixture within the flammability limits of the diesel fuel. Because there is no ignition source, diesel fuel needs to have a high cetane number and a low auto-ignition temperature.

The branched saturated hydrocarbon product has a high cetane number due to the saturation phenomenon and the long chain alkyl chain length, thereby making the product suitable as a cetane number improver. Cetane number estimates how easily diesel is naturally compressed. Higher cetane numbers indicate naturally easier and better engine operation.

The high flash point of branched saturated hydrocarbon products is of primary importance from a fuel storage and transportation standpoint. In ethanol/mineral oil diesel or ethanol/vegetable oil diesel microemulsions, the ignition point is significantly lower. Too low a fire will cause the fuel to fire, be subject to splashing, and possibly sustain ignition and explosion. In addition, a low ignition point may indicate contamination with more volatile and explosive fuels such as gasoline.

The branched saturated hydrocarbon product contains no sulfur because of the natural fatty acid based starting material. Therefore, in the pretreatment of the exhaust gas, the catalyst and the particulate filter can be easily adjusted to the sulfur-free hydrocarbon compounds according to the present invention. The catalyst poisoning is reduced and the service life of the catalyst is obviously prolonged.

Although the branched saturated hydrocarbon product is produced from natural fatty acid based raw materials, it does not contain oxygen and thus Nitrogen Oxide (NO)_x) Is much lower than conventional biodiesel fuel.

The branched saturated hydrocarbon product produced according to the present invention is very similar to conventional diesel fuel, and therefore it can be used in compression ignition (diesel) engines without modification, which is not the case with fatty acid methyl ester based biodiesel compounds.

Furthermore, no gellation is formed in the fuel delivery system due to the absence of any oxygenate alkane constituents. The engine parts were not contaminated with carbon deposits as was the case with the fatty acid methyl ester based biodiesel compounds.

The branched saturated hydrocarbon product can be blended at any level with petroleum diesel and with fatty acid methyl ester based biodiesel compounds. The latter may be advantageous if it is desired to enhance the lubricity of the product.

In particular, when the process is carried out using the decarboxylation/decarbonylation route, the consumption of hydrogen is significantly reduced. The decarboxylation/decarbonylation reaction reduces the hydrogen consumption by 20-40%.

The invention is illustrated below with examples that set forth some preferred embodiments of the invention. It will be apparent, however, to one skilled in the art that the scope of the present invention is not intended to be limited to these embodiments only.

Examples

Example 1

Skeletal isomerization and deoxygenation of tall oil fatty acids

Distilled tall oil fatty acids were isomerized in a Parr high pressure reactor using mordenite-type zeolite. Tall oil fatty acid, 5 wt% catalyst and 3 wt% water based on all mixtures were placed in the reactor and air was removed from the autoclave using a purge of nitrogen. The mixture was stirred at 300 rpm. The reactor was heated to 280 ℃ and kept under a nitrogen atmosphere of 1.8MPa for 6 hours. After cooling, the reaction mixture is taken out of the autoclave and the zeolite is filtered off. The filtrate was distilled under reduced pressure, thereby producing a monomer acid.

The monomeric acid thus obtained was placed in an autoclave and the double bond was hydrogenated at 150 ℃ for 3 hours under 2MPa of hydrogen atmosphere using a catalyst containing 5 wt% Pd on carbon until the reaction was complete. The amount of catalyst was 2 wt% of the monomer acid. The reaction mixture was then cooled and the catalyst was filtered off.

The resulting crude branched fatty acids are subjected to conventional solvent fractionation steps to produce isomerized fatty acids. To the crude branched fatty acid was added about 2 times by weight hexane. After cooling the mixture to-15 ℃, the resulting crystals were filtered off. Then, hexane was distilled off from the filtrate, thereby producing pure isomerized fatty acids.

In a subsequent deoxidation step by hydrodeoxygenation, dry and prevulcanised NiMo/Al are used, under a hydrogen pressure of 3.3MPa and at a temperature of 340 ℃₂O₃The catalyst hydrodeoxygenated the isomerized fatty acids to the corresponding paraffins in a Parr high pressure reactor. The amount of catalyst was 2.5 wt% of the fatty acid.

The product was a branched, predominantly paraffinic mixture with properties as shown in table II. The product was light yellow in color and it contained < 10ppm of sulfur derived from the HDO catalyst used in the batch hydrodeoxygenation.

Example 2

Skeletal isomerization and deoxygenation of tall oil fatty acids at higher temperatures

Distilled tall oil fatty acids were isomerized, double bonds hydrogenated, and branched saturated fatty acids were additionally hydrodeoxygenated as in example 1, except that the reactor temperature was reduced to 325 ℃ in hydrodeoxygenation.

A completely transparent product was obtained, the properties of which are shown in table 3.

Example 3

Skeletal isomerization of tall oil fatty acids in the absence of water, deoxygenation at low temperatures, and cold filtration of the final product

In the skeletal isomerization step, tall oil fatty acid and 5 wt% of mordenite-type zeolite catalyst were mixed and air was removed from the Parr autoclave using a purge of nitrogen. The mixture was stirred at 300 rpm. The reactor was heated to 275 ℃ and held under a 0.1MPa nitrogen atmosphere for 6 hours. After cooling, the reaction mixture was taken out of the autoclave and the zeolite was filtered off. The filtrate was distilled under reduced pressure, thereby producing a monomer acid.

The double bond of the monomeric acid thus obtained was hydrogenated as in example 1.

In the deoxidation step, dried and presulfided NiMo/Al is used at a hydrogen pressure of 3.3MPa and a temperature of 325 deg.C₂O₃The catalyst hydrodeoxygenated the isomerized fatty acids to paraffins in a Parr high pressure reactor. The amount of catalyst was 2.5 wt% of the fatty acid. The mixture was cooled to-15 ℃ and the resulting crystals were filtered off.

The product was a mixture of branched, predominantly paraffinic hydrocarbons with properties as shown in table 3. The color of the product was completely transparent.

Example 4

Skeletal isomerization and deoxygenation by decarboxylation/decarbonylation of tall oil fatty acids in the absence of water

Tall oil fatty acid was isomerized and prehydrogenated as in example 3. In the deoxygenation step by decarboxylation/decarbonylation, the isomerized fatty acids were charged to a Parr high pressure reactor and dried and presulfided NiMo/Al was used₂O₃The catalyst removes the carboxyl groups.

The isomerized fatty acids are decarboxylated/decarbonylated to paraffins at a gas pressure of 0.3MPa and a temperature of 335 ℃. The amount of catalyst was 2.5 wt% of the fatty acid. The gas consisted of 10% hydrogen in nitrogen.

The product is a branched, predominantly paraffinic mixture with carbon chain lengths typically one carbon atom less than the hydrodeoxygenation carbon chain length and the properties are shown in table 3. The color of the product was completely transparent.

TABLE 3 Properties of Hydrocarbon products

Method of producing a composite material	Analysis of	Example 1	Example 2	Example 3	Example 4
						ASTM D4052	Density 15 ℃ kg/m3	811	809	799	800
ASTM D2887	Initial distillation temperature	245	219	225	117
							5％，℃	277	281	270	170
	10％，℃	283	286	280	195
							30％，℃	294	293	294	262
	50％，℃	300	296	300	271
							70％，℃	309	310	309	283
	90％，℃	326	337	323	301
							95％，℃	362	443	357	312
	End, C	486	507	481	355
						ASTM D445	kV40，cSt	4.0	4.4	3.8	2.4
	GC wt-% of n-paraffins	6	15	7	11
							Alkane C IR wt-%	＞70		＞70	70
	Cycloalkane C IR wt-%				24
							Aromatic C IR wt%	14		7	6
ASTM D3120	S，mg/kg	9		＜1
						ASTM D4629	N，mg/kg	＜1		＜1
EN 22719	Flash point PMcc, DEG C	141	138	139	67
							iQT cetane number	93	78	93	60
EN 116	Cold filter plugging point DEG C	-39	-31	-35	-45
						ASTM D5773D5771	Cloud point,. degree.C	-32	-29	-29	-42
IP 391	Aromatic Hydrocarbon% (predominantly Single)	16.1		7.8	5.8

Claims (25)

1. A process for producing branched saturated hydrocarbons, characterized in that a mixture comprising unsaturated fatty acids or unsaturated fatty acids and C₁-C₅The starting material of the ester of an alcohol, or a mixture thereof, is subjected to a skeletal isomerization step carried out at a temperature of 150-400 ℃, at a pressure of 0-5MPa and in the presence of an acidic catalyst selected from the group consisting of silicoaluminophosphates and zeolites, followed by a deoxygenation step carried out by decarboxylation/decarbonylation or hydrodeoxygenation carried out by inert gas at a temperature of 100-400 ℃ and at an atmospheric pressure of-20 MPaBy contacting the product resulting from the skeletal isomerization step and optionally the solvent or solvent mixture with a heterogeneous decarboxylation/decarbonylation catalyst under pressure of a gas/hydrogen mixture, the heterogeneous decarboxylation/decarbonylation catalyst being selected from supported catalysts comprising one or more metals of group VIII and/or group VIA of the periodic Table of the elements.

2. A process according to claim 1, characterised in that the feedstock comprises at least 20% by weight of unsaturated fatty acids or unsaturated fatty acids and C₁-C₅Esters of alcohols.

3. A process according to claim 1, characterised in that the feedstock comprises at least 50% by weight of unsaturated fatty acids or unsaturated fatty acids and C₁-C₅Esters of alcohols.

4. A process according to claim 1, characterized in that the unsaturated fatty acid or unsaturated fatty acid and C used as starting material₁-C₅The total number of carbons in the ester of the alcohol is 8-26.

5. A process according to claim 1, characterized in that the unsaturated fatty acid or unsaturated fatty acid and C used as starting material₁-C₅The total carbon number of the alcohol ester is 12 to 20.

6. A process according to claim 1, characterized in that the feedstock originates from biological raw materials.

7. Process according to claim 1, characterized in that the skeletal isomerization step is carried out at a temperature of 200-350 ℃ and at a pressure of 0.1-5 MPa.

8. The process according to claim 1, characterized in that the skeletal isomerization step is carried out in the presence of an acidic catalyst selected from the group consisting of silicoaluminophosphates and faujasites, offretites, montmorillonites and mordenites.

9. Process according to claim 1, characterized in that 0 to 8% by weight, based on the total reaction mixture, of water or C₁-C₅Alcohol is added to the feedstock.

10. Process according to claim 1, characterized in that 1 to 3% by weight, based on the total reaction mixture, of water or C₁-C₅Alcohol is added to the feedstock.

11. A process according to claim 1, characterized in that when the feedstock comprises fatty acids, 1-3% by weight of water, based on the total reaction mixture, is added to the feedstock.

12. A process according to claim 1, characterized in that, when the starting material comprises fatty acid esters, 1-3% by weight of C, based on the total reaction mixture₁-C₅Alcohol is added to the feedstock.

13. The process according to claim 1, characterized in that the skeletal isomerization step is followed by a prehydrogenation step.

14. The process according to claim 13, characterized in that the prehydrogenation step is carried out in the presence of a hydrogenation catalyst comprising one or more group VIII and/or group VIA metals at a temperature of 50 to 400 ℃ and under a hydrogen pressure of 0.1 to 20 MPa.

15. The process according to claim 13, characterized in that the prehydrogenation step is carried out in the presence of a hydrogenation catalyst comprising one or more group VIII and/or group VIA metals at a temperature of 150 ℃ and 250 ℃ and under a hydrogen pressure of 1 to 10 MPa.

16. The process according to claim 13, characterized in that when the feedstock comprises fatty acid esters, the prehydrogenation step is carried out in the presence of a metal catalyst at a hydrogen pressure of 25-30MPa and at a temperature of 200-230 ℃.

17. The process according to claim 13, characterized in that when the feedstock comprises fatty acid esters, the prehydrogenation step is carried out in the presence of a copper-chromite catalyst or a chromium-, ferrous-or rhodium-activated nickel catalyst, under a hydrogen pressure of 25-30MPa and at a temperature of 200-230 ℃.

18. Process according to claim 1, characterized in that in the decarboxylation and/or decarbonylation the product and optionally the solvent or solvent mixture are contacted with a heterogeneous decarboxylation/decarbonylation catalyst selected from supported catalysts comprising one or more metals of group VIII and/or group VIA of the periodic Table of the elements at a temperature of 250-350 ℃ and a pressure of 0.1-5MPa of an inert gas/hydrogen mixture.

19. Process according to claim 1 or 18, characterized in that the heterogeneous decarboxylation and/or decarbonylation catalyst is Pd on carbon or sulfided NiMo on alumina.

20. The process according to claim 1, characterized in that in hydrodeoxygenation the product and optionally a solvent or solvent mixture are contacted with a hydrogenation catalyst comprising a metal of group VIII and/or group VIA of the periodic Table of the elements at a pressure of 1-20MPa and at a temperature of 200-500 ℃.

21. Process according to claim 1, characterized in that in hydrodeoxygenation the product and optionally a solvent or solvent mixture are contacted with a hydrogenation catalyst comprising a metal of group VIII and/or group VIA of the periodic Table at a pressure of 2-10MPa and a temperature of 250-350 ℃.

22. The process according to claim 20 or 21, characterized in that the hydrodeoxygenation catalyst is a supported Pd, Pt, Ni, NiMo or CoMo catalyst and the support is alumina and/or silica.

23. A process according to claim 20 or 21, characterized in that the hydrodeoxygenation catalyst is NiMo/Al₂O₃Or CoMo/Al₂O₃。

24. Process according to claim 1, characterized in that in the decarboxylation/decarbonylation and/or hydrodeoxygenation step the solvent is selected from the group consisting of hydrocarbons, and recycled process streams containing hydrocarbons, and mixtures thereof.

25. Process according to claim 1, characterized in that in the decarboxylation/decarbonylation and/or hydrodeoxygenation step the solvent is selected from the group consisting of paraffins, iso-paraffins, cyclo-paraffins and aromatic hydrocarbons having a boiling range of 150-350 ℃, and recycled process streams containing hydrocarbons, and mixtures thereof.