Method for reducing feed impurities

Abstract

Disclosed herein is a method for selecting a pre-treatment for renewable feedstocks comprising organic nitrogen impurities prior to feeding the feedstock to catalytic hydroprocessing and isomerization. Removal of nitrogen impurities protects catalysts of subsequent process steps from deactivation and extends catalyst life. Some of the nitrogen impurities disclosed herein were not previously found or reported in renewable feedstocks.

Description

Technical Field

[0001] This disclosure generally relates to the field of hydrotreating renewable feedstocks. Specifically, it relates to feedstocks used in said hydrotreating and impurities therein. In particular, a method is provided here for analyzing and identifying at least one organic nitrogen-containing compound, based on which effective pretreatment of the feedstock can be selected. Background Technology

[0002] Methods for hydrogenating renewable feedstocks to produce renewable fuels have been known since the 1990s. FI100248 B1 is one of the earliest publications that discloses how vegetable oils or waste (such as TOFA) can be converted into n-alkanes and further into isoalkanes in a catalytic process.

[0003] Typical feedstocks for such methods include vegetable oils / fats and animal oils / fats, as well as their waste or residue materials. Some related waste or residue materials, such as PFAD or CTO, are also referred to as feedstocks of interest. The main compounds in the feedstock are fatty acids, fatty acid alkyl esters such as FAME, and / or glycerides, more specifically fatty acid triglycerides, diglycerides, and monoglycerides. However, depending on the source of the feedstock, they may also contain other components, some of which are useless or even harmful to fuel production.

[0004] Several impurities have been identified that passivate, deactivate, clog, poison, or otherwise interfere with the applied catalysts. These interferences degrade catalyst performance and shorten catalyst lifetime. For example, it is known that the removal of metallic impurities, phosphates, and phospholipids is essential for maintaining catalyst activity.

[0005] The heteroatom-containing organic compounds in the feedstock vary depending on the feedstock. When producing hydrocarbons from oxidized feedstocks, heteroatom-containing oxygen in the feedstock can be removed via hydrodeoxygenation (HDO) reaction. Besides gaseous H₂O, other heteroatoms such as sulfur and nitrogen mostly react with gaseous H₂S and NH₄ on typical HDO catalysts. However, some compounds are complex in nature and remain unreacted or transform into other heteroatom-containing organic compounds.

[0006] Furthermore, in impurity identification, the raw materials themselves are difficult to use as a matrix because they contain various compounds. Typically, the physical properties of impurities are similar to those of the raw material matrix. Therefore, impurity identification has always been challenging because matrix components interfere with impurity analysis.

[0007] Analyzing the total nitrogen content in fatty acid samples is common. However, the range of different organic nitrogen derivatives with varying functional groups is broad, and some compounds are more detrimental to catalysts and, more importantly, to more specific analyses compared to others. Therefore, the need to remove certain compounds varies before hydrogenation, particularly before hydroisomerization, and before analysis itself. This cannot be predicted solely by the total nitrogen content.

[0008] Recently, several methods have been developed for studying challenging matrices containing specific organic nitrogen species or their groups. Gas chromatography / mass spectrometry (GC / MS) coupled with direct analysis of sludge bio-oil can broadly indicate the types of organic nitrogen species, such as amides, nitriles, amines, pyridines, pyrazines, pyrroles, and indoles. To obtain more detailed results, Sultana & Johnson focused on sample preparation and reported a protocol for fractionation and identification of primary amides from bio-oil produced by the rapid pyrolysis of sewage sludge (Sultana T, Johnson ME, Sample preparation and gas chromatography of primary fatty acid amides, J Chromatogr A. 2006 Jan 6;1101(1-2):278-85). They proposed column chromatography using a series of solvent elutions to adequately separate model compounds for GC / MS analysis. However, they reported that only 16.3% of the nitrogen in the bio-oil was detectable by GC / MS. Furthermore, they reported difficulties in detecting highly polar and / or non-volatile organic nitrogen species due to the limitations of GC / MS analysis.

[0009] Better methods for extracting raw material samples from the raw material matrix are still needed for identification. Furthermore, to better understand and control the following methodological steps, it is necessary to identify impurities in the raw materials. The analytical results from impurity identification also need to be used to select raw material pretreatments to remove one or more organic nitrogen compounds. Summary of the Invention

[0010] The purpose of this disclosure is to eliminate at least some of the problems associated with known techniques and to provide a method for specific analysis in which the detection of organic nitrogen compounds provides data for the selection of feedstock pretreatment.

[0011] Another object of this disclosure is to provide a novel sample preparation procedure capable of specific analysis of organic nitrogen compounds.

[0012] According to this disclosure, a method for pretreating a renewable feedstock comprising triacylglycerol and one or more organic nitrogen compounds is provided, wherein the method comprises the following steps: (i) Collect at least one sample of the renewable raw material and purify the sample by removing triglycerides to obtain a purified sample; (ii) Analyze the purified sample to provide data on at least one organic nitrogen compound in the renewable feedstock; (iii) Using the data, identify at least one organic nitrogen compound; (iv) Select at least one pretreatment step based on the identified organic nitrogen compounds, said pretreatment step being capable of reducing or removing the identified organic nitrogen compounds from the renewable feedstock; (v) subject the renewable feedstock to at least one of the pretreatments selected in step (iv) to obtain a pretreated renewable feedstock suitable for hydrotreating into branched alkanes, wherein the pretreated renewable feedstock has a lower content of the organic nitrogen compounds than the content of the organic nitrogen compounds in the sample collected in step (i).

[0013] The range of different organic nitrogen-containing compounds in feedstocks varies, especially in recycled or waste feedstocks. Some organic nitrogen functional groups do not convert to ammonia during hydrotreating, but rather to other functional groups. For example, fatty acid amides have been found to convert to fatty acid amines under hydrotreating conditions. Therefore, unless the feedstock undergoes specific pretreatment prior to hydrotreating, some organic nitrogen-containing compounds themselves or their derivatives may be carried into the liquid product instead of ammonia hydrodenitrogenation and removal via gas separation. This method provides information about the organic nitrogen compounds contained in the feedstock, which can then be used to select appropriate pretreatments or a series of pretreatments to ensure the desired low levels of said organic nitrogen compounds entering the hydrotreating process.

[0014] The inventors have unexpectedly discovered a method for identifying previously unidentifiable organic nitrogen compounds, specifically those not previously available by analytical methods. Furthermore, the detection of these compounds can be used to select appropriate pretreatments for triacylglycerol-containing feedstocks suitable for hydrogenation into branched alkanes. This identification method is based on the detection of nitrogen compounds deposited on the catalyst used in the hydrogenation process, particularly those intended for conversion into branched alkanes. Reducing or even removing certain organic nitrogen compounds through appropriate pretreatment can improve or extend catalyst performance and / or catalyst lifetime.

[0015] In the analysis of complex matrices, such as renewable feedstocks containing triacylglycerols, and especially when derived from waste and residues, the availability and applicability of methods for detailed identification, detection, and quantification of impurities are limited because analytical data obtained from triacylglycerols overlap with analytical data for compounds of interest. The inventors have now developed a method for providing efficient sample purification through the removal of triacylglycerols and subsequent identification of organic nitrogen compounds. The analytical results can then be used to select appropriate pretreatment for renewable feedstocks.

[0016] The use of different non-binding example aspects and implementations in this disclosure is merely to illustrate selected aspects or steps that may be used in different implementations. Some implementations may be presented with reference only to certain example aspects. It should be understood that corresponding implementations may also be applicable to other example aspects. Attached Figure Description

[0017] Some exemplary embodiments will be described with reference to the accompanying drawings, in which: Figure 1 An example elution map of extraction using an elution gradient for a raw material sample is provided, where the signal intensity of the evaporative light scattering detector (ELSD) is given as a function of time (min).

[0018] Figure 2 The entire process according to the present invention is illustrated schematically. Detailed Implementation

[0019] The following will refer to the illustration. Figure 2 The entire process according to the present invention will be described in more detail.

[0020] The renewable feedstock (101) is fed into a storage tank (100), where a sample (10) can be obtained. Analysis (not shown) is performed according to this procedure to provide the characteristics and, optionally, the amount of one or more organic nitrogen compounds in the feedstock. Based on this result, a pretreatment (110) is selected, and the analyzed feedstock (102) is fed to one or more suitable pretreatments (111, 112, 113, 114, 115). Pretreatments (111, 112, 113, 114, 115) are provided as alternatives, or optionally, a series of two or more pretreatments can be performed. Additional samples (11) can be collected between or after pretreatment. The pretreated renewable feedstock (103) is then fed to a hydrotreating process. Figure 2In the described embodiment, the hydrotreating is carried out in a combination of hydrodeoxygenation (120) and hydroisomerization (130) reactions in separate reactors. The effluent from the hydrodeoxygenation reaction is subjected to gas / liquid separation to remove the gas (121), and only the liquid product (104) is directed to the hydroisomerization (130) reactor. The effluent (105) from the hydroisomerization reaction may also optionally undergo gas / liquid separation (not shown) and be separated into different products (141, 142, 143) in a product fractionator (140).

[0021] Regarding organic nitrogen compounds as process impurities, the most important sample is obviously the sample (10) taken from the renewable feedstock (101). This result is used to select an appropriate pretreatment. However, other samples (11) collected between or after pretreatment, such as sample (12) collected after hydrodeoxygenation or yet another sample (13) collected after hydroisomerization, can provide data on the level and characteristics of organic nitrogen impurities remaining after their respective reactors. However, in this method, at least one sample (11) is collected and analyzed to confirm that the organic nitrogen compound content in the pretreated renewable feedstock (103) is lower than that in sample (10). Alternatively, the total nitrogen content in sample (11) is lower than the organic nitrogen compound content in sample (10), which also indicates effective pretreatment. The inventors have noted that hydrodeoxygenation conditions convert fatty acid amides into fatty acid amines rather than ammonia, which can be removed by gas (121). This analytical procedure can be applied to samples from other unit processes, such as after hydrodeoxygenation and / or even after hydroisomerization.

[0022] Considering the entire process, the effectiveness of the pretreatments (111, 112, 113, 114, 115) can also be demonstrated by analyzing the gases (121). When monitoring the effectiveness of the selected pretreatments, ammonia formed in the hydrodeoxygenation reactor via the hydrodenitrification reaction can be considered.

[0023] The renewable feedstocks used in this method include triacylglycerols and are suitable for hydrotreating to provide branched alkanes that can be used as renewable fuels or fuel components as end products.

[0024] Generally, the raw materials used in this article refer to renewable raw materials, that is, raw materials derived from biological sources. The renewable properties of carbon-containing compositions (such as biologically derived raw materials and products, i.e., renewable raw materials and products) can be determined by comparing the 14C-isotope content of the raw material with the 14C-isotope content of the air in 1950. 14Carbon isotope content can serve as evidence of the renewable or biological origin of raw materials, any intermediates, or products. Renewable materials contain more unstable radioactive carbon compared to fossil-derived carbon atoms. 14 C) Atoms. Therefore, through analysis 12 C and 14 The ratio of carbon isotopes can distinguish carbon compounds from those of biological origin and those from fossil origin. Therefore, a specific ratio of these isotopes can be used to identify renewable carbon compounds and differentiate them from non-renewable carbon compounds (i.e., fossil carbon compounds). The isotopic ratio does not change during chemical reactions. ASTM D6866 (2020) is an example of a suitable method for analyzing the carbon content of biological sources. For example, an example of how ASTM D6866 can be applied to determine the renewable content in fuels is provided in Dijs et al.’s article Radiocarbon, 48(3), 2006, pp 315-323. For the purposes of this invention, a carbon-containing material, such as a feedstock or product, is considered to be of renewable origin if it contains 90% or more modern carbon (pMC) (e.g., approximately 100% modern carbon, measured using ASTM D6866).

[0025] Renewable feedstocks are readily available from a wide range of sources, including oils and / or fats, typically containing lipids (e.g., fatty acids or glycerides), such as vegetable oils / fats, animal oils / fats, algae oils / fats, fish oils / fats, and oils / fats derived from other microbial processes, such as genetically manipulated algae oils / fats, genetically manipulated oils / fats from other microbial processes, and genetically manipulated vegetable oils / fats. Feedstocks from renewable sources (such as vegetable oils and animal fats) are well-suited to this method. Most of these vegetable oils and animal fats typically consist of fatty acids, either as free fatty acids or as esters of free fatty acids, such as 25 wt% or 40 wt% or more of fatty acids. Components derived from these materials, such as alkyl esters, typically C1-C5 alkyl esters, such as methyl esters, ethyl esters, propyl esters, isopropyl esters, butyl esters, sec-butyl esters, or olefins, may also be used. Furthermore, renewable feedstocks may include C1-C5 alkyl alcohols, particularly methyl, ethyl, propyl, isopropyl, butyl, and / or sec-butyl esters of fatty acids, and any combinations thereof. Examples of free fatty acid esters are fatty acid glycerides (monoglycerides, diglycerides, and / or triglycerides) or, for example, fatty acid methyl esters (FAME) or fatty acid ethyl esters (FAE). Therefore, renewable feedstocks may contain 25 wt% or more of fatty acids or fatty acid esters.

[0026] Renewable feedstocks may also include free fatty acids, fatty acid esters (including monoglycerides, diglycerides, and triglycerides), or combinations thereof. For example, free fatty acids may include free fatty acids obtained by removing free fatty acids from triglyceride transesterification feedstocks. Renewable feedstocks may include fatty acid distillates from vegetable oil deodorization.

[0027] Raw materials can be selected from animal and fish oils / fats, vegetable oils and / or plant oils, and / or microbial oils, such as babassu oil, palm seed oil, carinata oil, olive oil, coconut butter, soybean oil, canola oil, coconut oil, muscat butter, rapeseed oil, peanut oil, sesame oil, corn oil, sunflower oil, poppy seed oil, cottonseed oil, soybean oil, laurel seed oil, crude tall oil, tall oil, tall oil fatty acids, tall oil pitch, crude palm oil, palm oil, palm oil fatty acid distillate, jatropha oil, palm kernel oil, camelina oil, archaeal oil, bacterial oil, fungal oil, protozoal oil, algae oil, seaweed oil, and mustard seed oil. Oils containing halophilic bacteria, milk fats including lauric acid-myristic acid groups (C12-C14), land animal fats including palmitic acid groups (C16), land animal fats including stearic acid groups (C18), whale oil and fish oils including linoleic acid groups (unsaturated C18), whale oil and fish oils including erucic acid groups (unsaturated C22), whale oil and fish oils including oleo stearic acid groups (conjugated unsaturated C18), fats with substituted fatty acids (ricinoleic acid, C18) such as castor oil, and any mixtures of two or more of these. Based on the level of pretreatment and the content of residual phosphorus and metals, feedstock oils can be classified into crude oil, degummed oil, heat-treated oil, and RBD (refined oil, bleached oil, and deodorized oil) grades. Animal fats and / or oils may include non-edible tallow, edible tallow, industrial tallow, flotation tallow, lard, poultry fat, poultry oil, fish fat, fish oil, and any mixture of two or more thereof. Oils and greases may include yellow oils and greases, brown oils and greases, waste vegetable oils, restaurant greases and grease traps (FOG) from municipal facilities (such as water treatment facilities), and waste oils from industrial packaged food operations, and any mixture of two or more thereof.

[0028] Raw materials may include derivatives of natural fats, including monoglycerides or diglycerides of C10-C28 fatty acids, C10-C28 fatty acids, C10-C28 fatty acid anhydrides, non-glycerol C10-C28 fatty acid esters, C10-C28 fatty alcohols, C10-C28 fatty aldehydes, and C10-C28 fatty ketones. C10-C28 fatty acids, their monoglycerides, and diglycerides are typically prepared by hydrolyzing the corresponding triglycerides. Non-glycerol C10-C28 fatty acid esters are primarily prepared from triglycerides via transesterification. C10-C28 fatty alcohols, aldehydes, and ketones are prepared by reducing (usually by hydrogenation) the corresponding fatty acids. Advantageously, the raw material hydrocarbons may be C10-C24. Most typical exemplary raw materials are animal fats and palm oil fatty acids, particularly those derived from waste and residues.

[0029] In one embodiment, the raw materials include waste and residue materials selected from one or more of animal fats / oils and vegetable fats / oils: for example, sludge palm oil, such as palm effluent sludge (PES) or palm oil mill effluent (POME), uneaten edible oil (UCO), or crude tall oil (CTO), acid oil (ASK), brown oil (BG), yellow oil (YG), low-quality animal fat (LQAF), poultry fat (AFP), spent bleaching earth oil (SBEO), industrial corn oil (TCO), or lignocellulose-based oil, municipal solid waste-based oil, or algae-based oil.

[0030] Typically, waste and residue materials used as raw materials contain relatively high levels of metals, nitrogen, and / or phosphorus, which classifies them as inferior raw materials. Different raw materials may contain metals (total weight of any metal detected) greater than 50 wppm, greater than 200 wppm, or even greater than 300 wppm, such as greater than 380 wppm of poultry fat or greater than 500 wppm of PES, or even greater than 800 wppm of metals. The most abundant metals are sodium, potassium, magnesium, calcium, iron, and copper. Accordingly, the phosphorus content in the waste and residue materials used as raw materials, calculated as elemental phosphorus, in BG can be greater than 50 wppm, greater than 70 wppm, greater than 100 wppm, or even greater than 200 wppm, for example, greater than 300 wppm.

[0031] It has been found that the majority of the nitrogen content in the waste and residue materials initially exists as impurities in the form of organic nitrogen compounds. Of particular interest are the wide variety of organic nitrogen compounds, which are generally more difficult to remove from matrices containing triglycerides through conventional feedstock pretreatment. Animal fats (as a specific feedstock), including peptides, amino acid derivatives, etc., have proven difficult to remove from feedstock streams.

[0032] Oils and / or fats of biological origin may include a single type of oil, a single type of fat, a mixture of different oils, a mixture of different fats, a mixture of oils and fats, fatty acids, glycerol, and / or a mixture of the above. Typically, when waste and residue materials are used, they contain mixtures of several components and therefore a range of several organic nitrogen-containing compounds as impurities.

[0033] It is already known that feed impurities include nitrogen. Animal fats can commonly contain 1000 ppm or even higher levels of nitrogen (measured as elemental nitrogen). A typical approach to treating undesirable impurities such as nitrogen impurities in feedstocks is to pretreat the feedstock prior to hydrotreatment. Removing water-soluble nitrogen compounds (such as inorganic nitrogen) via degumming is straightforward. However, in animal fats, the majority of nitrogen compounds are oil-soluble organic nitrogen compounds, which are much more difficult to reduce or remove than water-soluble nitrogen compounds. This method provides specific knowledge about organic nitrogen compounds and their removal measures, contributing to lower total nitrogen content in pretreated renewable feedstocks and other streams (such as hydrodeoxygenation products). Preferably, the hydrodeoxygenation products, prior to hydroisomerization, contain greater than 99 wt% hydrocarbons and less than 0.3 wppm of nitrogen (measured as elemental nitrogen).

[0034] Many vegetable oils and animal fats may contain typical amounts of organic nitrogen compounds as impurities, such as 1-100 ppm (measured as elemental nitrogen). By using this method and the analysis therein, feedstocks with high nitrogen levels can be used. Feedstocks with nitrogen contents greater than, for example, 60 wppm, 100 wppm, 300 wppm, 1000 wppm, or even greater than 2000 wppm, such as those in the range of 300-1200 wppm, can be used. In some embodiments, the feedstock has a nitrogen content greater than 1000 wppm, for example in animal fats. Typical ranges for nitrogen content in waste and residue materials used as feedstocks can be 300 wppm to 2500 wppm or greater, such as 500 wppm or greater, or 800 wppm or greater. Feedstocks can, for example, have nitrogen contents as high as 1500 wppm, such as 2500 wppm, or even as high as 4500 wppm. Examples of feedstocks with high nitrogen impurity content include some animal fats, namely BG, AFP, and LQAF, which may have a nitrogen content of about 1000 wppm, for example, in the range of 600 wppm to 1400 wppm. If desired, the feedstock can consist of a mixture of oxygenated hydrocarbons from different sources. For example, 50% palm oil with 23 ppm nitrogen impurities can be mixed with 50% animal fat with 1000 ppm nitrogen impurities to produce a feedstock with 512 ppm nitrogen impurities. Therefore, the feedstock can be selected from vegetable oils, animal fats, or mixtures thereof. This method has proven particularly useful when the feedstock includes animal fats.

[0035] Total nitrogen impurities are measured as elemental nitrogen. The method used to measure elemental nitrogen is ASTM D572, which may be more suitable for values ​​above 100 wppm.

[0036] The pretreated renewable feedstock for this method needs to be suitable for hydrodeoxygenation. Typically, when entering a hydrodeoxygenation reactor or its catalyst bed, the pretreated renewable feedstock should not include alkali metal and alkaline earth metal impurities greater than 10 w-ppm, preferably no greater than 5 w-ppm, more preferably no greater than 1 w-ppm (calculated as elemental alkali metals and alkaline earth metals); other metals not greater than 10 w-ppm, preferably no greater than 5 w-ppm, more preferably no greater than 1 w-ppm (calculated as elemental metals); nitrogen-containing impurities not greater than 1000 w-ppm, preferably no greater than 500 w-ppm, more preferably no greater than 150 w-ppm, most preferably no greater than 50 w-ppm, such as no greater than 5 w-ppm, such as no greater than 1 w-ppm (calculated as elemental nitrogen); phosphorus-containing impurities not greater than 30 w-ppm, preferably no greater than 15 w-ppm, more preferably no greater than 5 w-ppm, such as no greater than 1 w-ppm (calculated as elemental phosphorus); optionally no greater than 100 w-ppm, preferably no greater than 50 w-ppm, most preferably no greater than 30 w-ppm, such as no greater than 10 w-ppm, such as no greater than 5 w-ppm Sulfur-containing impurities (calculated as elemental sulfur) at w-ppm; and chlorine-containing impurities (calculated as elemental chlorine) optionally not exceeding 20 w-ppm, preferably not exceeding 10 w-ppm, and more preferably not exceeding 5 w-ppm. Depending on the efficiency of the hydrotreating catalyst bed system and the hydrotreating reactor unit configuration, even large amounts of nitrogen impurities in the feed can be tolerated, and the effluent from HDO can contain a suitable small amount of nitrogen impurities to enable it to withstand subsequent catalytic processes.

[0037] As used herein, hydrotreating of pretreated feedstocks refers to hydrodeoxygenation, hydrodesulfurization, hydrodenitrogenation, hydrodehalogenation (such as hydrodechlorination), double bond hydrogenation, hydrocracking, hydroisomerization, and it also removes some metals. Hydrotreating primarily removes covalently bound oxygen from fatty acids and final fatty acid esters (such as residual glycerol ester molecules) in the form of water, and is therefore also called hydrodeoxygenation (HDO). Liquid products recovered from HDO mainly include n-alkanes.

[0038] However, hydrogen and hydrotreating capacity are also consumed by other reactions, such as hydrodenitrification. Therefore, proper pretreatment of the feedstock can improve HDO capacity and catalyst performance by removing identified organic nitrogen-containing compounds.

[0039] Hydrodeoxygenation is preferably carried out in the presence of a hydrodeoxygenation catalyst on a support selected from Pd, Pt, Ni, Co, Mo, Ru, Rh, W or any combination thereof (such as CoMo, NiMo, NiW, CoNiMo), wherein the support is preferably alumina and / or silica.

[0040] Hydrodeoxygenation can be carried out under reaction conditions including temperatures ranging from 100°C to 500°C, preferably from 250°C to 400°C, more preferably from 280°C to 350°C, and most preferably from 300°C to 330°C. Hydrodeoxygenation can also be carried out under reaction conditions including pressures ranging from 0.1 MPa to 20 MPa, preferably from 0.2 MPa to 8 MPa.

[0041] Preferably, the weight hourly space velocity (WHSV) in the hydrodeoxygenation reaction a is less than 0.5 h⁻¹. -1 up to 3.0 h -1 More preferably 1.0 h -1 Up to 2.5 h -1 Optimal choice 1.0 h -1 Up to 2.0 h -1 Within the range of [specific range]. Preferably, the H2 flow rate is in the range of 350 nl H2 / l to 900 nl H2 / l feed, more preferably 350 to 750, and most preferably 350 to 500, where nl H2 / l refers to the standard hydrogen liters per liter of feed entering the HDO reactor in the presence of a hydrodeoxygenation catalyst.

[0042] Hydrotreating can include simultaneous or sequential hydrodeoxygenation and hydroisomerization. In a particular embodiment, hydrodeoxygenation and hydroisomerization are performed simultaneously using a NiW catalyst. When performed sequentially, hydrotreating includes first performing hydrodeoxygenation and then performing hydroisomerization.

[0043] When the pretreated feedstock is first subjected to HDO, the recovered liquid product is then subjected to hydroisomerization to produce branched alkanes. The hydroisomerization is carried out in the presence of a hydroisomerization catalyst containing a support, a metal, and another catalyst material. The support is selected from Al₂O₃ and SiO₂, the metal is selected from Pt, Pd, and Ni, and the other catalyst material is selected from SAPO-11, SAPO-41, ZSM-22, ZSM-23, ZSM-12, ZSM-48, ZSM-5, β-zeolite, and mixtures thereof. It has been found that this catalyst material is deactivated in the presence of organic nitrogen compounds during the hydroisomerization reaction; according to the invention, this deactivation can be prevented by specific pretreatment selection.

[0044] The hydroisomerization step is preferably carried out at a temperature of 250°C to 400°C, more preferably 280°C to 370°C, and most preferably 300°C to 350°C. The hydroisomerization can be carried out under reaction conditions including a pressure of preferably 1 MPa to 6 MPa, more preferably 2 MPa to 5 MPa, and most preferably 2.5 MPa to 4.5 MPa.

[0045] Hydrodeoxygenation can be performed, preferably at 0.5 h, including WHSV. -1 Up to 3 hours -1 More preferably 0.5 h -1 Up to 2 hours -1 The optimal value is 0.5 h. -1 up to 1 hour -1 The reaction is carried out under reaction conditions where the H2 flow rate (in liters of H2 / liter of feed) is preferably 100 to 800, more preferably 200 to 650, and most preferably 350 to 500.

[0046] Isomerization is a step primarily used to isomerize at least a portion of the hydrodeoxygenation feedstock. That is, although most thermal or catalytic conversions (such as HDO) result in only slight isomerization (typically less than 5 wt%), the isomerization step leads to a significant increase in the content of isoalkanes.

[0047] During conventional hydroisomerization, some cracking may occur. Therefore, the selection of catalysts and the optimization of reaction conditions are always important during the isomerization step. Due to cracking during isomerization, renewable diesel and renewable alkane gasoline components may be formed.

[0048] Hydroisomerization can be carried out in a conventional hydroisomerization unit. Hydrogen is added to the hydroisomerization step. The hydrodeoxygenation step and the hydroisomerization step can be carried out in the same reactor in different reactor beds, or even in the same reactor bed.

[0049] For feedstocks containing triacylglycerols suitable for hydrotreating into branched alkanes, various pretreatments with a wide range of modifications are available in this field. It is also known that two or more feedstock pretreatments can be performed sequentially. According to a preferred embodiment, one or more feedstock pretreatments are selected from degumming, heat treatment, acid treatment (such as strong acid treatment), filtration, adsorbent bleaching, or any combination thereof. This method, based on the identification of organic nitrogen compounds to select pretreatments, best protects the hydrotreating catalyst from deactivation and extends catalyst lifetime.

[0050] Therefore, this document provides a method for pretreating renewable feedstocks containing triacylglycerols and one or more organic nitrogen compounds, wherein the method includes the following steps: (i) Collect at least one sample of the renewable raw material and purify the sample by removing triglycerides to obtain a purified sample; (ii) Analyze the purified sample to provide data on at least one organic nitrogen compound in the renewable feedstock; (iii) Identify at least one organic nitrogen compound based on the data; (iv) Select at least one pretreatment step based on the identified organic nitrogen compounds, the pretreatment step being capable of reducing or removing the identified organic nitrogen compounds from the raw material; (v) subject the renewable feedstock to the pretreatment selected in step (iv) to obtain a pretreated renewable feedstock suitable for hydrotreating into branched alkanes, wherein the pretreated renewable feedstock has a lower organic nitrogen content than the organic nitrogen content in the sample collected in step (i).

[0051] This analysis provides the identification of organic nitrogen compounds and links them to pretreatment methods capable of reducing the content of said organic nitrogen compounds. Identification here refers to the identification of nitrogen-containing functional groups or specific compounds of organic nitrogen compounds based on library databases. When it comes to reducing or decreasing the content of said organic nitrogen compounds, those skilled in the art will recognize that quantitative results depend on factors such as the analytical method, the initial concentration of the organic nitrogen compounds, and their interactions, and therefore cannot be directly evaluated using numerical terms. However, this condition is met when the content of organic nitrogen compounds in renewable feedstocks is lower than the content of organic nitrogen compounds in the sample collected in step (i), and when the difference in content is significant relative to the on-site accuracy of the analytical supplier.

[0052] Furthermore, this method can also discover novel organic nitrogen compounds that were previously unknown. Appropriate sample purification from triglycerides and subsequent analysis made these discoveries possible.

[0053] The newly detected compounds are thioalkyl fatty amides: C18H37O3NS, C19H39O3NS, C20H41O3NS, C21H43O3NS, C22H45O3NS, C22H43O3NS, and C24H49O3NS; amino acid dimers: cyclic (Ile / Leu-[-2H]Pro)C11H16O2N2, cyclic (Pro-Trp)C16H17O2N3, cyclic ([-2H]Pro-Val)C10H14O2N2, and cyclic (Ile / Leu-Val) C11H20O2N2; Primary fatty amides: C17: 1-amide C17H33NO, C23: O-amide C23H47NO, C21: O-amide C21H43NO, C21: 1-amide C21H41NO, C8: O-amide C8H17NO, C20: O-amide C20H41NO, C22: O-amide C22H45NO, C22: 1-amide C21H43NO, C14: 1-amide C14H27NO, C15: O-amide C15H33NO, C17: O-amide C17H35NO, C19: O-amide C19H39NO, C19: 1-amide C19H37NO, C23: 1-amide C23H45NO, C24: O-amide C24H49NO; Nitriles: docosanonitrile C22H43N and docosanonitrile C24H47N; Imidides: imides (C16:0-C5:1) C21H39O2N, imide (C18:0-C5:1) C23H43O2N, imide (C18:1-C5:1) C23H41O2N, imide (C14:0-C5:1) C19H35O2N, imide (C14:0-C6:1) C20H37O2N, imide (C14:0-Pro) C19H36O2N2, imide (C16:0-C5:1) C21H39O2N, imide (C16:0-C6:1) C22H41O2N, imide (C16:0-Pro) C21H40O2N2, imide (C18:0-C5:1) C23H43O2N, imide (C18:0-C6:1) C24H45O2N, imide (C18:0-Pro) C23H44O2N2, imide (C18:1-C5:1) C23H41O2N, imide (C18:1-Pro) C23H42O2N2;N-Alkenylamides: Octadecenamide, N-(vinyl)-C20H37ON, octadecylamide, N-(vinyl)-C20H39ON, octadecylamide, N-allylC21H39ON, palmitamide, N-(vinyl)-C18H35ON, palmitamide, N-allylC19H37ON, tetradecylamide, N-(vinyl)-C16H31ON; and secondary and tertiary amides: aromatic N-aliphatic derivatives (Mw494, MW520, MW522), N-pentyl-C16:O-amide C21H41NO, N-phenethyl-C17:O-amide C25H43NO, N-phenethyl-C18:O-amide C26H45NO, N-phenethyl-C18:1-amide C26H43NO, phenyl-carbonyl-16:O-amide mw375 C24H41NO2, phenyl-carbonyl-C18:0-amide Mw403 C26H45NO2, and phenyl-carbonyl-C18:1-amide Mw401 C26H43NO2.

[0054] According to one embodiment, in step (i), triacylglycerols are removed from the sample by solid-phase extraction or by rapid chromatography to provide a fraction of the purified sample. The inventors have discovered that triacylglycerols interfering with the analysis of organic nitrogen compounds can be removed by solid-phase extraction or by rapid chromatography to provide such a fraction of the purified sample that can be analyzed by mass spectrometry. Removal of triacylglycerols by rapid chromatography has shown particularly good results in the experiments conducted.

[0055] Based on the preferred removal of triacylglycerols, rapid chromatography includes a column (such as, for example, an amino column, a silica column, or a diol column) and increases the polarity of the solvent during extraction. Preferably, the column is a silica column. Rapid chromatography provides fractions from which organic nitrogen compounds can be identified, and the matrix no longer overlaps with the peaks of most interest. Considering the role of triacylglycerols as the sample matrix and organic nitrogen compounds as minor components (even traces), separation by elution becomes even more meaningful for detection.

[0056] According to a preferred embodiment, heptane is used as the first solvent in rapid chromatography. A polar gradient is required to shorten the analysis time.

[0057] The analysis in step (ii) involves the detection of organic nitrogen compounds from the purified sample or its fractions using GC-HRMS. If not removed, the matrix tends to obscure the relevant regions where organic nitrogen compound peaks appear in the GC-HRMS chromatogram and mass spectrum. GC-HRMS detection appears to be only applicable to samples that do not contain triacylglycerols.

[0058] Given that nitrogen compounds are more polar than typical hydrocarbon compounds in gas chromatography, columns commonly used for hydrocarbon analysis are not entirely suitable. Column length also plays a role in separation. Longer columns can achieve higher chromatographic resolution compared to shorter columns. However, in this case, the compound of interest has relatively low volatility, so long columns cannot be used. Therefore, a 15 μm column with a slightly polar stationary phase provides excellent separation. Furthermore, good heat resistance is required for this column.

[0059] For this experiment, three columns with different stationary phases were selected for laboratory testing. The selected columns had a micropolar phase and were able to withstand high temperatures. The test columns were: RTX-200MS, crosslinked trifluoropropylmethylsiloxane, 15 m, 0.25 mm ID, 0.25 uM df, ZB-35HT Inferno; crosslinked 35% phenyl, 65% dimethyl polysiloxane, 15 m, 0.25 mm ID, 0.25 uM df; TR-50MS, crosslinked 50% phenylphenylene polysiloxane, 15 m, 0.25 mm ID, 0.25 uM df.

[0060] Depending on the specific implementation, high-resolution, high-precision, and high-sensitivity MS, such as Q ExactiveMS, can be used. The acquisition method is then a full scan based on the mass range of the target nitrogen compound's mass spectrum, rather than the tandem mass spectrometry (MS-MS) method often chosen when designing target mass spectrometry methods. Ion source and analyzer conditions can be optimized to enable the analysis of nitrogen impurities with a wide boiling point range eluted from gas chromatography. Electron ionization is chosen as the ionization method due to its high sensitivity and ability to generate unique fragment ions from the analyte.

[0061] The generated MS data files are processed in the software. An automated target screening master method utilizing a large number of parameters provides automated acquisition, detection, identification, and reporting of organic nitrogen compounds in samples. Compound-specific identifiers stored in the database can be selected from GC retention time, compound name, chemical formula, molecular structure, CAS number, exact mass of the target ion, exact mass of the confirmatory ion and fragment ion, and ion ratio. Internal standards (such as stearoyl stearate) can be used to correct for variations in gas chromatographic retention time and to estimate the amount of nitrogenous impurity compounds.

[0062] According to one embodiment, compound-specific identifiers for various organic nitrogen components can be stored in a database. The database provides a basis for comparing data on unknown compounds obtained from samples with data on compounds already identified and stored in the database. The following novel compound groups can be analyzed using the proposed method: diketopiperazines (amino acid dimers), imides (aliphatic-amino acid derivatives), thioalkyl fatty amides, N-alkenyl-fatty amides, fatty acid amides, and fatty acid nitriles.

[0063] The identification in step (iii) involves using an automated target screening master method that includes a library database with compound-specific identifiers. Several different compounds or groups of compounds can be identified from the purified sample.

[0064] The compounds identified to date are compiled in Tables 1 and 2. They provide examples of compounds, and their data can be stored and used in a database.

[0065] Table 1. Organic nitrogen compounds identified in the samples; amides.

[0066] Acyl group name CX:Y; X is the number of carbon atoms, and Y is the number of double bonds in the corresponding acyl group. Acyl groups are derived from the fatty acid precursors of the molecule. For example, C16:0 corresponds to an acyl group with sixteen carbon atoms and zero double bonds, and it is derived from palmitic acid.

[0067] Table 2. Organic nitrogen compounds identified in the samples: diketopiperazines, nitriles, thioalkyl fatty amides, and primary fatty amides.

[0068]

[0069] In Tables 1 and 2, compounds are grouped according to their associated nitrogen-containing functional groups. Those skilled in the art will understand that, from a certain perspective, such compounds may be referred to using different nomenclatures. Nevertheless, the group headings in this table refer to the common functional group as a property shared by each member of its respective group. Variables (Ri) are then characterized around this common functional group. x Next, we will discuss these explanatory functional groups and the groups containing the variables.

[0070] As used herein, N-alkenylamides share a functional amide group substituted by an unsaturated hydrocarbon and an acyclic fatty acid residue. The general structure and structural formula of N-allyl palmitamide as a specific example are given in Scheme 1 below.

[0071]

[0072] Option 1. Using the general formulas of N-alkenylamides and N-allyl palmitamides as specific examples.

[0073] In the general formula, each R1 is a fatty acid residue, referring to the following standard fatty acid nomenclature, such as palmitic acid or octadecenoic acid, and each R2 is an alkenyl substituent, such as vinyl or allyl. In the specific exemplary compound N-allyl palmitamide, R1 is a palmitic acid residue C 15 H 31 Furthermore, R2 is allyl, i.e., 2-propenyl. Following preferred nomenclature in organic chemistry, this compound with the molecular formula C... 19 H 37 The molecular name of NO is N-prop-2-enylhexadecanoamide. However, it is also known as N-allyl palmitoylamide, N-allyl palmitamide, hexadecanoamide, N-2-propenyl, palmitoyl allyl amide, hexadecanoic acid allyl amide, N-allyl palmitamide, and N-(2-propenyl)hexadecanoamide.

[0074] Accordingly, the imides used in Table 1 consist of acyclic residues of fatty acids and amino acids, which are substituted with the same amino groups. The general structures and structural formulas of imides (C16:0-C5:1) and imides (C16:0-Pro) as specific examples are given in Scheme 2 below.

[0075]

[0076] Scheme 2. Using the general formula of imides and specific examples of imides (C16:0-C5:1) and imides (C16:0-Pro).

[0077] In the general formula, each R3 is a fatty acid residue, referring to the following standard fatty acid nomenclature, such as palmitic acid or octadecenoic acid, and each R4 is an amino acid residue, such as a residue of a complete amino acid or a residue of an alkenyl derivative of an amino acid. In the specific exemplary compound imide (C16:0-C5:1), R3 is a palmitic acid residue C 15 H 31 Furthermore, R4 is an isopropenyl group, which may be a residue of the deaminated valine amino acid. In another specific exemplary compound, the imide (C16:0-Pro), R3 is a palmitic acid residue C. 15 H 31 Furthermore, R4 is a proline amino acid residue C4H8N. Following preferred nomenclature in organic chemistry, this compound with the chemical formula C... 21 H 39The imide (C16:0-C5:1) molecule of O2N is named N-(3-methyl-2-butenoyl)-palmitamide, and the imide (Cl6:0-Pro) molecule is named N-hexadecanoyl-prolylamide.

[0078] The secondary and tertiary amides used in Table 1 share a functional amide group, which is substituted by a fatty acid residue and one or two cyclic, straight-chain or branched aliphatic hydrocarbons. The straight-chain or branched aliphatic hydrocarbon may contain aromatic or carbonyl substituents. The general structures and structural formulas of N-phenylethyl-C16:O-amides and pyrrolidine-C16:O-amides as specific examples are given in Scheme 3 below.

[0079]

[0080] Scheme 3. Using the general formula of secondary and tertiary amides and N-phenylethyl-C16:O-amide and pyrrolidine-C16:O-amide as specific examples.

[0081] In the general formula, each R5 is a fatty acid residue, referring to the following standard fatty acid nomenclature, such as palmitic acid or octadecenoic acid. R6 is a straight-chain or branched aliphatic hydrocarbon that may contain aromatic or carbonyl substituents. R7 is a hydrogen atom (in secondary amides) or a straight-chain or branched aliphatic hydrocarbon (in tertiary amides) that may contain aromatic or carbonyl substituents. R6 and R7 together may also represent the same straight-chain or branched aliphatic hydrocarbon forming a cyclic structure with the same nitrogen atom substituted at the end of the hydrocarbon chain. In the specific exemplary compound N-phenylethyl-C16:O-amide, R5 is a palmitic acid residue C 15 H 31 R6 is phenylethyl, and R7 is a hydrogen atom. In the specific exemplary compound pyrrolidine-C16:O-amide, R5 is a palmitic acid residue C. 15 H 31 Furthermore, R6 and R7 are the ends of the same straight-chain C4H8 hydrocarbon chain. Following preferred nomenclature in organic chemistry, this chain with the chemical formula C... 24 H 41 The molecule of NO is named N-phenylethyl palmitamide, but it is also referred to by synonyms such as N-(2-phenylethyl)hexadecanoamide, and has the chemical formula C 20 H 39 The molecular name for NO is hexadecanoic acid, pyrrolidine.

[0082] The nitriles used in Table 2 consist of alkyl residues of fatty acids and nitrile groups. The general structure and structural formula of hexadecanoic acid nitrile as a specific example are given in Scheme 4 below.

[0083]

[0084] Option 4. Using the general formula of nitriles and hexadecanenitrile as specific examples.

[0085] In the general formula, each R8 is an alkyl residue of a fatty acid, referring to the standard fatty acid nomenclature, such as palmitic acid or octadecenoic acid. In the specific exemplary compound hexadecanoic acid, R8 is the palmitic acid residue C. 15 H 31 It is replaced by a nitrile group. Following preferred nomenclature in organic chemistry, this compound with the chemical formula C... 16 H 31 The molecule of N is named hexadecanenitrile, but it also has synonyms such as palmitonitrile, 1-cyanopentadecane, and palmitic acid nitrile.

[0086] The diketopiperazines used in Table 2 are cyclic dipeptides of two amino acids. They share the basic structure of diketopiperazine, which contains substituents for the corresponding amino acids that depend on the constituent molecules. The general structure and structural formula of the ring (Ala-Phe) as a specific example are given in Scheme 5 below.

[0087]

[0088] Scheme 5. Using the general formula and ring (Ala-Phe) of diketopiperazines as specific examples, structural parts A and B are also shown.

[0089] In the general formula, R9-R in the diketopiperazine ring 12 The substituents depend on the amino acid-derived structural motifs A and B of the constituent molecule. Structural motifs A and B are derived from the following amino acids: alanine, proline, valine, isoleucine, leucine, phenylalanine, glycine, dehydroproline, or tyrosine. In a specific compound ring (Ala-Phe), A is derived from alanine, and B is derived from phenylalanine. Following preferred nomenclature in organic chemistry, the compound with the chemical formula C... 12 H 14 The molecular name for N2O2 is cyclo(Ala-Phe), but it is also known to have synonyms such as 2,5-piperazinedione, 3-methyl-6-(phenylmethyl)- and 3-benzyl-6-methyl-2,5-piperazinedione.

[0090] As used in Table 2, thioalkyl fatty amides are reaction products of fatty acids and methionine amino acids, producing decarboxylated and oxidized amides, with sulfone functional groups added to the molecule. A specific example has the chemical formula C0. 20 H 41 The general structure and structural formula of the O3NS compounds are given in Scheme 6 below.

[0091]

[0092] Option 6. Using the general formula and C of thioalkyl fatty amides.20 H 41 O3NS is a specific example.

[0093] In the general formula, each R 13 It is an alkyl residue of a fatty acid, referring to the standard nomenclature of fatty acids, such as palmitic acid or octadecenoic acid. Following the preferred nomenclature in organic chemistry, it is designated as having the chemical formula C... 20 H 41 The molecular name of O3NS is N-(3-((S-methylthioalkyl)propyl)-palmitamide.

[0094] The primary amides used in Table 2 share functional amide groups substituted with acyclic fatty acid residues. The general structure and structural formula of C22:O-amides as specific examples are given in Scheme 7 below.

[0095]

[0096] Scheme 7. Using the general formula of primary amides and C22:0 amides as specific examples.

[0097] In the general formula, R 14 The substituent is an alkyl residue of the fatty acid, referring to the standard fatty acid nomenclature below, such as palmitic acid or octadecenoic acid. Following the preferred nomenclature in organic chemistry, the fatty acid with the chemical formula C1 is... 22 H 45 The molecular name for NO is docosamide. The compound groups detected by GC-HRMS were identified in the experiments as primary fatty acid amides, secondary fatty acid amides, tertiary fatty acid amides, N-alkenyl amides, imides, diketopiperazines, nitriles, or sulfur-containing fatty acid amides (such as thioalkyl fatty acid amides). Rapid chromatography has also been shown to achieve such purification of secondary fatty acid amides, tertiary fatty acid amides, N-alkenyl amides, imides, diketopiperazines, nitriles, or sulfur-containing fatty acid amides, which is unpredictable in existing analytical methods.

[0098] According to a second aspect of the invention, this document provides the use of GC-HRMS analysis for identifying organic nitrogen compounds present in renewable feedstock samples containing triacylglycerols, the use further comprising, based on said identification, selecting a pretreatment to reduce the organic nitrogen compound content of said renewable feedstock. As explained in detail with respect to this method, GC-HRMS analysis provides data for identifying organic nitrogen compounds in the feedstock.

[0099] According to a preferred embodiment of the intended use, the sample is purified prior to GC-HRMS analysis by removing triglycerides, preferably by rapid chromatography.

[0100] This application can also involve treating the renewable feedstock with at least one pretreatment to obtain a pretreated renewable feedstock. The pretreatment selected based on the identification provides a pretreated renewable feedstock in which the content of the identified organic nitrogen compounds is reduced. In other words, the feedstock can be selectively purified. Pretreatment can be selected from various types, including degumming, heat treatment, acid treatment (e.g., strong acid treatment), filtration, bleaching with a usable adsorbent, or any modification, or combinations thereof. According to one embodiment, two or more pretreatments are performed sequentially, which ensures the removal of two or more undesirable organic nitrogen compounds.

[0101] experiment

[0102] The following examples illustrate various aspects of the present invention.

[0103] Example 1. Elution method

[0104] The device used is a CombiFlash NextGen 300+ (Teledyne ISCO).

[0105] Four solvents were used in the extraction method: heptane, ethyl acetate, isopropanol, and methanol. For optimal detection in ELSD, the spray chamber temperature was set to 40°C instead of the default 30°C for normal phase separation. The drift tube temperature was set to 60°C. Detection sensitivity was set to high, peak width to 30 seconds, and threshold voltage to 0.02 volts.

[0106] The specific properties of the sample of interest are considered by first separating the main triglyceride fraction and then separating the fraction containing the unknown analyte. Furthermore, the flow rate and sample volume also vary.

[0107] Flow rate and gradient program have a combined effect on resolution. For 24 g silica-gold columns, flow rates of 35 ml / min and 40 ml / min were tested; for smaller columns, a flow rate of 10 ml / min was used in the initial tests. The total run time was approximately 27 minutes.

[0108] The sample is injected into heptane, and for nonpolar fractions, 10 vol-% EtOAc in heptane is used as the elution solvent. An example of a gradient method includes: heptane / EtOAc 10% for 7 min; EtOAc for 5 min; EtOAc / IPA 0-100% for 4 min; IPA / MeOH 70-100% for 3 min; MeOH for 1 min; EtOAc / IPA 100-50% for 3 min; heptane / EtOAc 50% for 2 min; and heptane / EtOAc 50-10% for 2 min. The solvent fraction containing the unknown analyte is then evaporated.

[0109] This method was found to provide pure fractions for GC-Orbitrap analysis. Obtaining numerous fractions with "small amounts" of components or at least as little background as possible allows the GC-Orbitrap method to develop and create libraries. Using the developed method, in addition to the first fraction primarily containing triglycerides, a series of 4–8 fractions can be collected based on the sample and its components.

[0110] Example 2. Orbitrap

[0111] The device used is a Thermo Fisher Scientitic Q Exactive GC Orbitrap (available from Thermo Fisher Scientitic).

[0112] Nitrogen compounds are more polar than typical hydrocarbon compounds, so columns commonly used for hydrocarbon analysis are not entirely suitable. Regarding column length, the compounds of interest are quite polar and have low volatility, therefore a 15 m column was tested. This column must have a slightly polar phase and be able to withstand high temperatures; therefore, a Restec: RTX-200MS, crosslinked trifluoropropylmethylsiloxane, 15 m, 0.25 mm ID, 0.25 μM df was used.

[0113] The GC method employed a split / splitless inlet with a split ratio of 1:100 to 1:10. The GC oven was initially held at 25–100°C for 0.5–5 minutes, then ramped up to 200–320°C at a rate of 5–20°C / minute. Analysis showed that the GC inlet and GC-MS interface were maintained at a constant temperature of 250–320°C.

[0114] The GC method was finalized by adding a carrier gas flow ramp to ensure all compounds were flushed out of the column. The initial flow rate (2.8 ml / min) was maintained for the first 24 minutes, after which the flow rate was increased to 4.5 ml / min.

[0115] Given the high resolution and sensitivity of Q Exactive MS, the acquisition method was based on a full scan of the target nitrogen compound's mass spectrum mass range, rather than tandem mass spectrometry (MS-MS) methods often chosen when designing target mass spectrometry methods. Ion source and analyzer conditions were optimized to enable the analysis of nitrogen impurities with a wide boiling point range eluted from gas chromatography. Electron ionization was chosen as the ionization method due to its high sensitivity and ability to generate unique fragment ions from the analyte, a prerequisite for automated identification used in this method. The high resolution (20,000–120,000) of MS was used to ensure complete separation and high-quality precision (<2–10 ppm) of tightly localized m / z values ​​for analyte molecules and fragment ions from the complex nature of the sample. Internal mass axis calibration with column ionization was used. Real samples prepared by pretreatment methods and various standards (e.g., perfluorotributylamine, capsaicin, caffeine, stearoyl stearate, fatty acid methyl esters) were used for the development and optimization of the MS method. The mass spectrometry parameters are as follows: electron ionization energy of 20-100 eV, mass range of 30-1500 m / z, solvent delay of 0.1-6 minutes, run time of 24-80 minutes, and ion source temperature of 200-320°C.

[0116] The obtained MS data files were processed in Thermo TraceFinder general-purpose GC software. An automated target screening master method utilizing a large number of parameters was developed for the automated acquisition, detection, identification, and reporting of target nitrogen compounds in samples. The core of this method consists of a database containing compound-specific identifiers (e.g., GC retention time, compound name, chemical formula, molecular structure, CAS number, precise mass of target ion, precise mass and ion ratio of confirmatory ion and fragment ion, and precise mass of fragment ion). Using cyclo(Phe-Pro) diketopiperazine as an example, the database is as follows: 15.7 minutes; cyclo(Phe-Pro); C 14 H 16 N2O2; pyrrolo[1,2-a]pyrazin-1,4-dione, hexahydro-3-(benzyl)-; 14705-60-3; 125.0709; 91.05423 40.38796%; 153.0659 69.1742%; 70.06513 34.53461%; 244.12069.77327%; 91.05423; 153.0659; 70.06513; 244.1206. This method also uses stearoyl stearate as an internal standard to correct for variations in gas chromatographic retention time.

[0117] Peak detection and identification settings in the Tracefinder main method were primarily optimized using real samples. Parameter optimization represents a trade-off between accurate identification of nitrogen-containing analytes and the method's final analytical sensitivity. The ICIS algorithm was tested and deemed best suited for peak detection and was selected for the final method.

[0118] Example 3. Analytical method for organic nitrogen compounds in an exemplary feedstock comprising triacylglycerol, method intermediates, and products.

[0119] A method for analyzing different nitrogen compounds at the molecular level was developed. This method consists of GC-HRMS analysis and data processing steps, in which a database of 120 nitrogen compounds was screened. This method allows for tracking the effectiveness of different pretreatment steps for different nitrogen compounds or compound classes. In this example, two organic nitrogen compounds were added to an animal fat feed and subjected to six different pretreatment procedures (Table 3). In Table 3, amounts are expressed as absolute values ​​(ppm) and relative values ​​(%). Relative values ​​were calculated by comparing the amounts of compounds in the feed and the processed products.

[0120] Table 3. Amounts of two organic nitrogen compounds neutralized in the feed after six different pretreatment methods.

[0121]

[0122] Compared to the feed, this method allows for the tracking of the removal of individual organic nitrogen compounds. As can be seen from Table 3, pretreatments 4, 5, and 6 effectively removed imides. Experiments conducted according to this method also showed that diketopiperazines behaved differently compared to imides. Pretreatment 4 only halved the amount of diketopiperazine, and pretreatment 6 had no effect on diketopiperazine. Optimal removal of both compounds was observed after pretreatment 5. This treatment reduced the amounts of imides and diketopiperazine to 4% and 17%, respectively.

[0123] The existing technique for analyzing this sample is total nitrogen analysis. Table 3 also shows that this method does not clearly reveal what actually happens during the treatment steps. The total nitrogen content remained unchanged after pretreatments 4 and 6, even though component level checks showed significant differences. In fact, combining the information from both analyses suggests that even if some compounds are removed, other nitrogen compounds may still be formed in this method.

[0124] This analytical method provides a novel means for identifying organonitrogen compounds in samples, such as renewable feedstock samples containing triacylglycerols. This identification allows for the selection of effective pretreatments to remove the specific organonitrogen compounds from the renewable feedstock containing triacylglycerols. In cases where several organonitrogen compounds are identified in a sample, a series of pretreatments can be designed to selectively remove these compounds. Various implementations have been proposed. It should be understood that in this document, the words *comprise*, *include*, and *contain* are each used as open-ended expressions without intended exclusivity.

[0125] The foregoing description provides a complete and informative description of the inventors’ current preferred mode for carrying out the invention, through non-limiting examples of specific implementations and methods. However, it will be apparent to those skilled in the art that the invention is not limited to the details of the embodiments provided above, but can be implemented in other embodiments or in different combinations of embodiments using equivalent means without departing from the characteristics of the invention.

[0126] Furthermore, some features of the exemplary embodiments disclosed above can be advantageously used without correspondingly using other features. Therefore, the above description should be considered merely illustrative of the principles of the invention and not as limiting thereto. Consequently, the scope of the invention is limited only by the appended patent claims.

Claims

1. A method for pretreating a renewable feedstock comprising triacylglycerol and one or more organic nitrogen compounds, wherein the method comprises the following steps: (i) Collect at least one sample of the renewable raw material and purify the sample by removing triglycerides to obtain a purified sample; (ii) Analyze the purified sample to provide data on at least one organic nitrogen compound in the renewable feedstock; (iii) Using the data, identify at least one organic nitrogen compound; (iv) Select at least one pretreatment step based on the identified organic nitrogen compounds, said pretreatment step being capable of reducing or removing the identified organic nitrogen compounds from the renewable feedstock; (v) subject the renewable feedstock to at least one of the pretreatments selected in step (iv) to obtain a pretreated renewable feedstock suitable for hydrotreating into branched alkanes, wherein the pretreated renewable feedstock has a lower content of the organic nitrogen compounds than the content of the organic nitrogen compounds in the sample collected in step (i).

2. The method of claim 1, wherein in step (i) triglyceride removal from the sample is performed by solid-phase extraction or rapid chromatography to provide fractions of the purified sample.

3. The method of claim 2, wherein the rapid chromatography includes a column, and the polarity of the solvent is increased during extraction.

4. The method according to any one of the preceding claims, wherein the analysis performed in step (ii) comprises using gas chromatography / high resolution mass spectrometry (GC-HRMS) to detect the organic nitrogen compounds from the purified sample or fraction thereof.

5. The method of claim 4, wherein the identification in step (iii) comprises using an automated target screening master method, the method comprising a library database with compound-specific identifiers.

6. The method according to any one of claims 1-3, wherein at least one organic nitrogen compound is identified in step (iii) as a primary fatty acid amide, secondary fatty acid amide, tertiary fatty acid amide, N-alkenyl amide, imide, diketopiramate, nitrile or sulfur-containing fatty acid amide.

7. The method according to claim 1, wherein two or more raw material pretreatments are performed sequentially in step (v).

8. The method according to claim 1 or 7, wherein the raw material pretreatment or said pretreatment is selected from degumming, heat treatment, acid treatment, filtration, adsorbent bleaching, or any combination thereof.

9. The method according to any one of claims 1-3 and 7, wherein the pretreated renewable feedstock is subjected to hydrogenation in the presence of a catalyst on a support selected from Pd, Pt, Ni, Co, Mo, Ru, Rh, W, or any combination thereof, and the liquid product is recovered.

10. The method according to claim 9, wherein the carrier is alumina and / or silicon dioxide.

11. The method according to any one of claims 1-3 and 7, wherein the hydrotreatment comprises hydrodeoxygenation under reaction conditions including a temperature in the range of 100°C to 500°C and / or a pressure in the range of 0.1 MPa to 20 MPa, and the hydrotreatment product is a hydrodeoxygenation product.

12. The method of claim 11, wherein the hydrodeoxygenation product contains more than 99 wt% hydrocarbons and less than 0.3 wppm of nitrogen as measured in elemental nitrogen.

13. The method according to any one of claims 1-3, 7 and 12, wherein the liquid product from the hydrotreatment is subjected to hydroisomerization in the presence of a hydroisomerization catalyst containing a support, a metal and another catalyst material to produce branched alkanes, wherein the support is selected from Al2O3 or SiO2, the metal is selected from Pt, Pd or Ni, and the other catalyst material is selected from SAPO-11, SAPO-41, ZSM-22 or ZSM-23.

14. The method of claim 13, wherein the hydroisomerization is carried out at a temperature of 250°C to 400°C and / or at a pressure of 1 MPa to 6 MPa.

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