Process for the selective decarboxylation of oxygenates

Abstract

One broad aspect of the present disclosure relates to a process apparatus and method for producing a hydrocarbon mixture suitable for use as an aviation fuel having an end boiling point below 300°C according to ASTM D86 from a decarboxylation feedstock, the decarboxylation feedstock being a feedstock comprising fatty acid esters and / or triglycerides and comprising C18 side chains, by directing the decarboxylation feedstock under decarboxylation conditions in contact with a material catalytically active in decarboxylation to become a deoxygenated hydrocarbon mixture, wherein the ratio between decarboxylation by formation of carbon oxides and decarboxylation by formation of water is at least 1.5:1, 2:1 or 3:1 as measured by the ratio of C17 paraffins to C18 paraffins in the deoxygenated hydrocarbon mixture, the related benefit being that such a decarboxylation based process selectively reduces the product carbon length by one carbon atom compared to a hydrogenolysis based process, which is advantageous for processes requiring a moderate reduction of the end boiling point.

Description

[0001] So far, the conversion of renewable energy sources in hydrotreatment has mainly focused on diesel production, because the typical fatty acids of biomaterials such as vegetable oils and animal fats (C14, C16 and C18) correspond to paraffins with a boiling point of 250-320°C, which fully complies with the typical diesel product with a boiling point of 150-380°C. According to ASTM 86, the boiling range of 120-300°C is required for aviation fuel products, which means that the heavy fraction of paraffins in the renewable feedstock needs to be converted into lighter materials in order to produce only aviation fuel. The present invention relates to a process to obtain high yield renewable aviation fuel by a selective decarboxylation process.

[0002] The standard for the quality of aviation fuel originating from hydrotreatment of oxygenates such as esters and fatty acids is ASTM D7566, A2.1, where the boiling point curve and composition are particularly specified. In particular, this standard requires a low boiling point product by requiring a T 10 (i.e. the temperature at which 10% has distilled according to ASTM D86) lower than 205°C, thus requiring the amount of low boiling point product. According to ASTM D86, the final boiling point (FBP) is specified lower than 300°C, which means that according to ASTM D86, all material that distills above 300°C needs to be converted into lighter components to fall within the aviation fuel range. Finally, the amount of aromatics is limited to lower than 0.5%wt. Most of these properties can be easily met by hydrotreatment, hydrocracking and fractionation, but especially hydrocracking leads to a yield loss.

[0003] Now, according to the present disclosure, it is proposed to produce aviation fuel by a process with a higher selectivity for decarboxylation than for hydrodeoxygenation, thus producing C17 hydrocarbons with a boiling range within the aviation fuel range, instead of C18 hydrocarbons with a boiling range above aviation fuel. This can be done in the presence of a catalytically active material comprising nickel as the only or the main active metal, and optionally after saturation of the double bonds in the feedstock, or by other decarboxylation specific methods, such as the method known to the skilled person from EP 1681337B. Compared to a process where C18 hydrocarbons are converted into C17 hydrocarbons by hydrocracking, the advantage is a surprisingly low yield loss and a low hydrogen consumption.

[0004] In the following, the term "stage" is applied to a process section without separation.

[0005] In the following, the abbreviation ppm 摩尔 is applied to mean parts per million by mass.

[0006] In the following, the abbreviation ppm v is applied to mean parts per million by volume, such as molar gas concentration.

[0007] In the following, the abbreviation %wt is applied to mean weight percent.

[0008] In the following, the term "renewable feedstock or hydrocarbon" is applied to mean a feedstock or hydrocarbon derived from a biological source or waste cycle. Recycled waste from fossil sources such as plastics should also be interpreted as renewable.

[0009] In the following, the term "deoxygenation" is applied to mean the removal of oxygen from oxygen-containing compounds by formation of water in the presence of hydrogen, and the removal of oxygen from oxygen-containing compounds by formation of carbon oxides in the presence of hydrogen.

[0010] In the following, the term "hydrodeoxygenation" is applied to mean the removal of oxygen from oxygen-containing compounds by formation of water in the presence of hydrogen.

[0011] In the following, the term "decarboxylation" is applied to mean the removal of oxygen from oxygen-containing compounds by formation of carbon oxides in the presence of hydrogen.

[0012] In the following, the term "topology of a molecular sieve" is used in the sense described in "Atlas of Zeolite Framework Types", Sixth Revised Edition, Elsevier, 2007, and according to the three-letter framework type code used herein.

[0013] In the following, the concentration of olefins shall be the total mass of oxygen-containing compound molecules in the mixture having at least one C=C double bond divided by the total mass of hydrocarbon-containing molecules (hydrocarbons, oxygen-containing compounds and hydrocarbon-containing molecules containing other heteroatoms).

[0014] In the following, for example, the term C18 (in general Cn, where n is a number) shall be interpreted as a hydrocarbon structure comprising 18 (or n) carbon atoms. A C18 side chain shall be interpreted as a chemically characteristic substructure comprising 18 carbon atoms, for example one of the fatty acids of a triglyceride molecule is stearic acid or oleic acid (giving two examples of linear C18 fatty acids).

[0015] One broad aspect of the present disclosure relates to a process for producing a hydrocarbon mixture from a decarboxylation feedstock comprising fatty acid esters and / or triglycerides, the hydrocarbon mixture having an end boiling point below 300°C according to ASTM D86 and suitable for use as an aviation fuel, wherein at least 40% of the carbon atoms of the decarboxylation feedstock are contained in C18 side chains, the process by converting the decarboxylation feedstock in the presence of a material catalytically selective for decarboxylation such that the ratio between decarboxylation by formation of carbon oxides and decarboxylation by formation of water as measured by the ratio of C17 paraffins to C18 paraffins in the deoxygenated hydrocarbon mixture is at least 1.5:1, 2:1 or 3:1, the associated benefit being that such a decarboxylation based process selectively reduces the product carbon length by one carbon atom compared to a hydrogenative deoxygenation based process, the process being advantageous for processes requiring a modest reduction in end boiling point.

[0016] In another embodiment, the decarboxylation conditions comprise a temperature in the range of 250-400°C, a pressure in the range of 30-150 bar and a liquid hourly space velocity (LHSV) in the range of 0.1-2, wherein the material catalytically active in decarboxylation comprises nickel, optionally in combination with other metals, supported on a support comprising one or more refractory oxides, such as alumina, silica or titania, the associated benefit being that such process conditions are well suited for the selective decarboxylation conversion of renewable feedstocks.

[0017] In another embodiment, at least 40%, 60% or 80% of the carbon of the decarboxylation feedstock is contained in C18 side chains, the associated benefit being that such a feedstock is particularly well suited for the production of products boiling in the aviation fuel range using a material catalytically active in decarboxylation.

[0018] In another embodiment, the material catalytically active in decarboxylation comprises more than 5 wt% Ni, more than 10 wt% Ni or more than 15 wt% Ni and less than 30 wt% Ni, less than 50 wt% Ni or less than 70 wt% Ni and less than 1 wt%, 0.5 wt% or less than 0.1 wt% Co, Mo and W, such as 0 wt% Co, Mo and W, the associated benefit being that such a material is selective for decarboxylation while being cost moderate.

[0019] In another embodiment, the decarboxylation feedstock is a saturated decarboxylation feedstock comprising less than 10 wt% or 1 wt% olefinic oxygenates, the associated benefit being a reduced need to carefully monitor the decarboxylation conditions to avoid deactivation of the material catalytically active in decarboxylation due to carbon deposition.

[0020] In another embodiment, the decarboxylation feedstock is provided as a product of a hydrogenation reaction that receives a crude oxygenate feedstock comprising at least 10 wt% or 50 wt% of olefinic oxygenates and selectively hydrogenates the olefinic oxygenates under olefin pre-hydrogenation conditions to provide the saturated decarboxylation feedstock, with the related benefit of minimizing exposure of catalytically active materials in decarboxylation to olefins, which can lead to carbon deposition on the catalytically active materials. Selective pre-hydrogenation on materials having NiS as the only or main active phase prior to decarboxylation is particularly beneficial because such materials have a higher propensity to form carbon deposits in the presence of olefins.

[0021] In another embodiment, the pre-hydrogenation conditions include a temperature in the range of 150°C to 220°C, 250°C or 280°C, a pressure in the range of 30-150 bar and a liquid hourly space velocity (LHSV) in the range of 0.1-2, wherein the material catalytically active in pre-hydrogenation comprises 5 wt% to 20 wt% of molybdenum and / or tungsten in combination with 1 wt% to 5 wt% of nickel and / or cobalt, supported on a carrier comprising one or more refractory oxides, such as alumina, silica or titania, with the related benefit that such process conditions are well suited for hydrogenation of olefinic bonds while minimizing hydrodeoxygenation of the renewable feedstock.

[0022] In another embodiment, the deoxygenated hydrocarbon mixture is separated according to boiling point to provide a hydrocracked intermediate aviation fuel having a T10 below 205°C and a final boiling point below 300°C according to ASTM D86, with the related benefit that the product of this process meets the boiling point specifications of the renewable aviation fuel specification ASTM D7566, even if the decarboxylation process is not 100% selective.

[0023] In another embodiment, the total volume of hydrogen sulfide is at least 50 ppm v , 100 ppm v or 200 ppm v , relative to the volume of molecular hydrogen in the gas phase of the total stream directed to contact the material catalytically active in decarboxylation, optionally originating from an addition stream comprising one or more sulfur compounds, such as dimethyl disulfide or fossil fuels, with the related benefit of ensuring stable operation of the material catalytically active in decarboxylation comprising sulfurized base metals if the amount of sulfur comprised in the feedstock is insufficient.

[0024] In another embodiment, the decarboxylation feedstock comprises at least 50% wt of triglycerides or fatty acids, with the related benefit that such feedstock is well suited for providing aviation fuels with excellent properties.

[0025] In another embodiment, the process further comprises a hydrocracking step under active hydrocracking conditions, wherein the deoxygenated hydrocarbon mixture or a mixture derived therefrom is directed to contact a material catalytically active in hydrocracking, the related benefit being that due to the nature of the decarboxylation feedstock or the selectivity of the decarboxylation step, such step allows to produce from the deoxygenated hydrocarbons a hydrocarbon mixture suitable for use as aviation fuel, even if it comprises hydrocarbons longer than C17. The hydrocracking step can be located upstream of decarboxylation in a so-called reverse section layout, or it can be located downstream of decarboxylation, either directly downstream of decarboxylation or after a separation step (e.g. a simple gas / liquid separation or fractionation).

[0026] In another embodiment, the hydrocracking conditions comprise a temperature in the range of 300-450 °C, a pressure in the range of 30-150 bar and a liquid hourly space velocity (LHSV) in the range of 0.5-8, wherein the material catalytically active in hydrocracking comprises an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten and molybdenum, preferably one or more elemental noble metals such as platinum or palladium, the acidic support is one or more of: an amorphous acidic oxide such as silica-alumina and a molecular sieve showing high cracking activity, for example a molecular sieve having a topology taken from the group of MFI, BEA and FAU, and an amorphous refractory support comprising one or more oxides taken from the group comprising alumina, silica and titania, the related benefit being that these conditions and materials are cost-effective and selective processes for conditioning the low temperature flow properties of the product. If the hydrocracking is directly located downstream of decarboxylation, the active metal is preferably one or more of the sulphided base metals nickel, cobalt, tungsten and molybdenum, whereas if the hydrocracking is located after a separation step, the active metal is preferably one or more elemental noble metals (such as platinum or palladium), unless a sulphur source is added to ensure sulphidation.

[0027] In another embodiment, the process further comprises an isomerization step under active isomerization conditions comprising a temperature in the range of 250-350 °C, a pressure in the range of 30-150 bar and a liquid hourly space velocity (LHSV) in the range of 0.5-8, wherein the material catalytically active in isomerization comprises an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten and molybdenum, preferably one or more elemental noble metals such as platinum or palladium, an acidic support preferably a molecular sieve, more preferably a molecular sieve having a topology taken from the group comprising MOR, FER, MRE, MWW, AEL, TON and MTT, and an amorphous refractory support comprising one or more oxides taken from the group comprising alumina, silica and titania, with the related benefit that these conditions and materials are a cost-effective and selective process for conditioning the low temperature flow properties of the product. For hydrocracking, isomerization can occur immediately downstream of decarboxylation or downstream of the separation section. If isomerization is directly downstream of decarboxylation, the active metal is preferably one or more of the sulfided base metals nickel, cobalt, tungsten and molybdenum, whereas if isomerization is after the separation step, the active metal is preferably one or more elemental noble metals (such as platinum or palladium), unless a sulfur source is added to ensure sulfidation.

[0028] The same considerations regarding active metals apply to the material catalytically active in isomerization as in hydrocracking.

[0029] Another aspect of the present disclosure relates to a process plant for producing a hydrocarbon fraction from a decarboxylation feedstock, the process plant comprising a decarboxylation section, a hydrocracking section and a fractionation section, the process plant being configured to direct a decarboxylation feedstock in combination with an amount of hydrocracked intermediate product to the decarboxylation section to provide a deoxygenated hydrocarbon mixture, separate the deoxygenated hydrocarbon mixture in the fractionation section to provide at least two fractions, including a low boiling product fraction and a high boiling product fraction, direct at least an amount of the high boiling product fraction to the hydrocracking section to provide a hydrocracked intermediate product, direct at least an amount of the hydrocracked intermediate product to the decarboxylation section, wherein the decarboxylation section comprises a catalytically active material, the catalytically active material comprising less than 1 wt%, 0.5 wt% or 0.1 wt% of Co, Mo or W, with the related benefit that such a process plant is suitable for carrying out the disclosed process in order to produce an aviation fuel according to specification ASTM D7566 Appendix A2 in a cost-effective and selective manner.

[0030] The processes described in this disclosure receive renewable feedstocks and / or oxygenate feedstocks, which include one or more oxygenates taken from triglycerides, fatty acids, esters, resin acids, ketones, aldehydes, alcohols, phenols, and aromatic carboxylic acids, wherein the oxygenates are derived from one or more of a biological source, a gasification process, a pyrolysis process, a Fischer-Tropsch synthesis, a methanol-based synthesis, or other synthesis processes, especially from raw materials of renewable origin, such as from plants, algae, animals, fish, vegetable oil refining, municipal waste, used cooking oil, plastic waste, rubber waste, or industrial organic waste such as tall oil or black liquor. Some of these feedstocks can contain aromatic compounds; especially from products derived from, for example, lignin and wood, or from waste derived from, for example, frying oil. Depending on the source, the oxygenate feedstock can include 1 wt% to 40 wt% oxygen. Biological sources typically include about 10 wt%, and 1 wt% to 20 wt% or even 40 wt% of the derived products.

[0031] To convert the renewable feedstock and / or oxygenate feedstock to hydrocarbon transportation fuels, the feedstock is directed, along with hydrogen, to contact a catalytically active material in a hydroprocessing, especially a hydrodeoxygenation. In addition to hydrodeoxygenation, the catalytically active material is typically active in decarboxylation, where oxygen is removed in the form of CO2 rather than H2O. Decarboxylation is typically less preferred than hydrodeoxygenation, as decarboxylation results in a loss of yield, and in addition, while the decarboxylation reaction itself consumes less hydrogen than the hydrodeoxygenation reaction, CO2 can be converted to CH4 to some extent, which involves consumption of hydrogen. In addition, especially at elevated temperatures, the catalytic hydrodeoxygenation process can have side reactions, such as the formation of heavy products from olefin molecules in the feedstock. This side reaction can be more frequent in the presence of catalytically active materials that are predominantly NiS. To moderate the release of heat, a liquid hydrocarbon, such as a liquid recycle stream or an external diluent feed, can be added. If the process is designed for the co-processing of fossil feedstocks and renewable feedstocks, it is convenient to use fossil feedstocks as the diluent, as less heat is released during the processing of fossil feedstocks, as fewer heteroatoms are released and fewer olefins are saturated. In addition to moderating the temperature, the recycle or diluent has the effect of reducing the likelihood of polymerization of olefinic materials, which would form undesirable heavy fractions in the product. The resulting product stream will be a hydrodeoxygenated hydrocarbon mixture stream including hydrocarbons, typically n-paraffins, and acid gases, such as CO, CO2, H2O, H2S, NH3, and light hydrocarbons, especially C3 and methane. For this disclosure, the feedstock is preferably rich in triglycerides, fatty acid esters, or fatty acids, which can release oxygen by decarboxylation.

[0032] Hydrodeoxygenation involves directing the feedstock into contact with a catalytically active material, which typically includes one or more sulphided base metals, such as nickel, cobalt, tungsten or molybdenum, but can also contain elemental noble metals (such as platinum and / or palladium) supported on a carrier, which includes an inert carrier, typically one or more refractory oxides such as alumina, but can also be silica or titania, but other inert carriers such as activated carbon can also be used. The carrier is typically amorphous. The catalytically active material can include other components, such as boron or phosphorus. Effective conditions for hydrodeoxygenation typically include temperatures in the range 250-400°C, pressures in the range 30-150 bar and liquid hourly space velocities (LHSV) in the range 0.1-2. Hydrodeoxygenation is typically exothermic, and in the presence of significant amounts of oxygen, the process can include intermediate cooling, for example by quenching with cold hydrogen, feed or product. The feedstock can preferably contain an amount of sulphur to ensure sulphidation of the metals (except in the case of noble metals), thereby maintaining their activity. If the gas phase includes less than 10, 50 or 200 ppm of sulphur, calculated as hydrogen sulphide, then a sulphide donor, such as dimethyl disulphide (DMDS), can be added to the feed. v

[0033] The hydrodeoxygenated hydrocarbon mixture will predominantly have the same structure as the carbon skeleton of the oxygenate in the feedstock, i.e. if the feedstock includes triglycerides, n-alkanes, but if hydrocracking side reactions occur, the product can have a shorter length than the fatty acids. Typically, the hydrodeoxygenated hydrocarbon mixture consists predominantly of straight chain alkanes having a boiling point range (250°C to 320°C) and a freezing point (0°C to 30°C) which are not suitable for use as aviation fuel.

[0034] For the hydrodeoxygenated hydrocarbon mixture to be used in practice as a fuel, the freezing point must be adjusted. The freezing point is adjusted by contacting the hydrodeoxygenated hydrocarbon mixture with a material having catalytic activity in isomerisation, by isomerising the n-alkanes to iso-alkanes.

[0035] Isomerisation involves directing the deoxygenated hydrocarbon mixture into contact with a material having catalytic activity in isomerisation. Effective conditions for isomerisation typically include temperatures in the range 250-350°C, pressures in the range 30-150 bar and liquid hourly space velocities (LHSV) in the range 0.5-8. Isomerisation is essentially thermally neutral and only consumes hydrogen in hydrocracking side reactions, but an appropriate amount of hydrogen is added to the isomerisation section as this is necessary for effective isomerisation. When the active metal on the material having catalytic activity in isomerisation is a noble metal, the hydrodeoxygenated hydrocarbon mixture is typically purified by gas / liquid separation to reduce the level of potential catalyst poisons to low levels, for example to reduce the level of sulphur, nitrogen and carbon present as carbon oxides to less than 1-10 ppm 摩尔 ​When the active metal is a base metal, the gas phase of the hydrodeoxygenated hydrocarbon mixture preferably contains at least 50 ppm v of sulfur (calculated as hydrogen sulfide).

[0036] The material catalytically active in isomerization typically comprises an active metal (either a noble metal such as platinum and / or palladium or a sulfided base metal such as nickel, cobalt, tungsten and / or molybdenum), an acidic support (typically a molecular sieve showing high shape selectivity and having a topology such as MOR, FER, MRE, MWW, AEL, TON and MTT) and a refractory support, typically amorphous (such as alumina, silica or titania, or a combination thereof). The catalytically active material can comprise other components, such as boron or phosphorus. Preferred isomerization catalysts include molecular sieves such as EU-2, ZSM-48, beta zeolite and combined beta zeolite and Y zeolite.

[0037] For a hydrodeoxygenated hydrocarbon mixture stream to be used as an aviation fuel fraction, the boiling point range can have to be adjusted. By directing the hydrodeoxygenated hydrocarbon mixture in contact with a material catalytically active in hydrocracking, the boiling point is adjusted by hydrocracking long chain alkanes to short chain alkanes.

[0038] Hydrocracking comprises directing a hydrocarbon in contact with a material catalytically active in hydrocracking. Effective conditions for hydrocracking typically include a temperature in the range of 250-400 °C, a pressure in the range of 30-150 bar and a liquid hourly space velocity (LHSV) in the range of 0.5-4. As hydrocracking is exothermic, the process can involve intermediate cooling, for example by quenching with cold hydrogen, feed or product. When the active metal on the material catalytically active in isomerization is a noble metal, the hydrodeoxygenated hydrocarbon mixture is typically purified by gas / liquid separation to reduce the level of potential catalyst poisons to low levels, for example to reduce the level of sulfur, nitrogen and carbon oxides present carbon to less than 1-10 ppm 摩尔 When the active metal is a base metal, the gas phase of the hydrodeoxygenated hydrocarbon mixture preferably contains at least 50 ppm v of sulfur (calculated as hydrogen sulfide).

[0039] Materials catalytically active in hydrocracking have similar properties to materials catalytically active in isomerisation and typically comprise an active metal (either a noble metal such as platinum and / or palladium or a sulphided base metal such as nickel, cobalt, tungsten and / or molybdenum), an acidic support (typically a molecular sieve showing high cracking activity and having a topology (e.g. MFI, BEA and FAU) but amorphous acidic oxides such as silica-alumina can also be used) and a refractory support (such as alumina, silica or titania or combinations thereof). The difference from materials catalytically active in isomerisation is typically the nature of the acidic support which can have a different structure (even amorphous silica-alumina) or have a different acidity (e.g. due to the silica: alumina ratio). The catalytically active material can include other components such as boron or phosphorus. Preferred hydrocracking catalysts include molecular sieves such as ZSM-5, Y zeolite or beta zeolite.

[0040] While catalyst design and process design can adjust the selectivity of the hydrocracking process, the nature of hydrocracking will involve some yield loss of light hydrocarbons which will not be useful as aviation fuel or even possibly as naphtha.

[0041] It has now been determined that, in this respect, a process with high selectivity to decarboxylation of fatty acids and triglycerides can be beneficial. The boiling point range required for aviation fuel (determined according to ASTM D86) is T10 < 205°C and FBP < 300°C, which corresponds to C8-C17 alkanes. Since most bio-fatty acids are dominated by C18 fatty acids (typically 70-95wt%), if the decarboxylation reaction is carried out by hydrodeoxygenation, there will be a significant amount of C18 alkanes. However, by selecting a catalyst and process which favours decarboxylation, the C18 fatty acids will be converted to C17 alkanes, which have a boiling point in the required range for aviation fuel.

[0042] Selectivity to decarboxylation has been considered in the prior art, primarily under the assumption that the reaction consumes less hydrogen. However, it has been suggested that the conversion of carbon oxides to methane increases the consumption of hydrogen, to some extent negating the benefit of this assumption. However, to produce aviation fuel, the adoption of selective decarboxylation to minimise yield loss by removing only a single carbon atom from the fatty acid chain has not been considered.

[0043] It is known that the use of catalytically active materials comprising nickel sulfide in the absence of other active metals favours decarboxylation selectivity. Unfortunately, experience with such decarboxylation selective catalysts has generally shown an increased tendency for coke formation, leading to catalyst deactivation, limiting the life of the catalyst charge. Without being bound by theory, it is believed that materials catalytically active in decarboxylation, such as nickel sulfide, are less active in hydrogen uptake and hydrogenation, and thus favour the decarboxylation reaction over hydrodeoxygenation consuming hydrogen, but at the cost of an increased tendency for olefin dehydrogenation leading to solid carbon formation. Thus, long term stability of decarboxylation selective catalytically active materials has been a challenge.

[0044] It has now been determined that if saturated oxygenates are directed to catalytically active materials selective for decarboxylation over hydrodeoxygenation, then hydrocracking combined with hydrodeoxygenation can be stably produced at higher yields of hydrocarbons boiling in the aviation fuel range compared to hydrocracking combined with hydrodeoxygenation.

[0045] Saturated oxygenates can preferably be provided by prehydrogenation in the presence of a hydrogenation active material, operated at a low severity, ensuring that olefinic bonds are hydrogenated without deoxygenation occurring. A material with high activity is preferred as this will result in a low temperature, which results in hydrogenation of the olefins over hydrodeoxygenation of the oxygenates. Examples of suitable catalytically active materials for such prehydrogenation include the materials listed above, especially those comprising a sulfided metal from Group 6 of the Periodic Table (e.g. Mo or W) in combination with a sulfided metal from Group 8, 9 or 10 (e.g. Ni or Co). Effective conditions for olefin hydrogenation generally include temperatures in the range 150°C to 220°C (especially at the start of the run), 250°C or even 280°C (at the end of the run), pressures in the range 30-150 bar, liquid hourly space velocities (LHSV) in the range 0.1-2. Olefin hydrogenation is exothermic, and in the presence of large amounts of olefins, the process can include intermediate cooling, for example by quenching with cold hydrogen, feed or product. The feedstock can preferably contain an amount of sulfur to ensure sulfidation of the metal to maintain its activity. If the gas phase includes less than 10, 50 or 100 ppm of sulfur calculated as hydrogen sulfide, then a sulfide donor, such as dimethyl disulfide (DMDS), can be added to the feed. v

[0046] Thus, a process for providing aviation fuel from oxygenates can advantageously be configured to include a low intensity prehydrogenation in the presence of an active material catalytically active in hydrogenation (e.g. NiMo on a refractory support), followed by deoxygenation under conditions favouring decarboxylation over hydrodeoxygenation. Typically, such a process would be followed by an isomerisation process, either with a sulfided catalytically active material or, after gas separation, with a reducing catalytically active material comprising a noble metal to provide a hydrotreated stream comprising an aviation fuel fraction.

[0047] ​The hydrotreated stream can be directed to a fractionator (after appropriate removal of gas phase in a separator train) and at least the gas fraction, middle fraction and bottom fraction of the hydrotreated stream are extracted. The water, hydrogen sulfide and ammonia content of all streams coming out of the fractionator are very low. Typically there will be a bottom fraction which is too heavy to be used as aviation fuel.

[0048] Figure 1 is a simplified diagram showing the layout of an aviation fuel production process. The oxygenate rich feed (100) is directed as a prehydrogenation feed stream to a prehydrogenation section (PRE) along with an amount of hydrogen rich stream (not shown) where it is contacted under olefin hydrogenation conditions with a material catalytically active in hydrogenation, such as a sulfided NiMo catalyst on alumina, typically operated below 250°C. This provides a prehydrogenated intermediate (102). The prehydrogenated intermediate (102) is combined with a hydrocracked bottom fraction (106) and directed as a deoxygenation feed (104) to a deoxygenation section (DO) comprising a material catalytically active in deoxygenation, such as a sulfided nickel catalyst on alumina, operated under deoxygenation conditions, providing a deoxygenated hydrocarbon mixture (112). The deoxygenated hydrocarbon mixture (112) is directed to a fractionation section (FRAC), shown as a single unit for simplicity, which separates the hydrocracked intermediate into a light overhead stream (120), a naphtha stream (122), a hydrotreated middle kerosene fraction (124) and a bottom fraction (126) as well as water and recycled hydrogen (not shown). An amount of the bottom fraction (126) is directed as a recycle stream and along with hydrogen (not shown) to a hydrocracking section (HDC) comprising a material catalytically active in hydrocracking, operated under effective hydrocracking conditions. The hydrotreated middle kerosene fraction is directed to an isomerization section.

[0049] To control the temperature in the deoxygenation section, an amount of the deoxygenated hydrocarbon mixture (112) can also be cooled, separated by flashing into a gas and liquid fraction and the liquid fraction can be directed to combine with the hydrocracked bottom fraction (106) as a recycle, such that the recycled deoxygenated hydrocarbon mixture acts as a heatsink for the heat generated in the exothermic deoxygenation reaction.

[0050] In addition to this particular layout, alternative layouts can also be relevant, including layouts where the hydrocracking section is not included, or layouts where the hydrocracking section (HDC) is located between the deoxygenation section (DO) and the fractionation section (FRAC). Furthermore, in these layouts, the recycle can be used as a heatsink. Example

[0051] Two examples are given to show the effect of the present disclosure.

[0052] Example 1

[0053] In a first example, two catalytically active materials were compared on similar feedstocks to assess selectivity towards decarboxylation and hydrodeoxygenation.

[0054] Example 1 A relates to the reaction of a renewable feedstock having the fatty acid composition shown in Table 1 (denoted here as Feedstock A) in the presence of a catalytically active material (NiMoS) comprising 2.6 wt% of Ni and 13 wt% of Mo, and Example 1 B relates to the reaction of a renewable feedstock having the fatty acid composition shown in Table 1 (denoted as Feedstock B) in the presence of a catalytically active material (NS) comprising 15 wt% of Ni and a small amount (0.3 wt%) of Mo. In both cases, the catalytically active material was sulfided and a certain amount of dimethyl disulfide was added to the reaction stream.

[0055] Examples 1 A and 1 B assess the reaction of the feedstocks in a single deoxygenation reactor. The reaction conditions are also shown in Table 2, corresponding to the mildest severity ensuring oxygen removal in the feedstock below 2000 ppmwt. Despite the different nature of Feedstock A and Feedstock B and the slight differences between the conditions of experiments 1 A and 1 B, the similarities between the two experiments are sufficient to consider the results representative of the differences between the two catalytically active materials, and it can be seen that the selectivity of NiS towards hydrodeoxygenation is only 30%, while the selectivity of NiMoS towards hydrodeoxygenation is 90%, while the NiS-based catalytically active material requires more severe conditions.

[0056] Table 1.

[0057]

[0058]

[0059] Table 2

[0060] Test Unit A B Feed Feed A Feed B Gas / oil ratio Nl / l 952 1500 Pressure Bar 64 90 Hydrogen consumption Nl / l 385 283 LHSV PRE h -1 ]]> 0.75 WABT PRE ℃ 210 Oxygen removed in PRE ％ 12 HDO selectivity PRE ％ 72 Olefins HYD PRE ％ 95 LHSV DO h -1 ]]> 0.505 0.5 WABT DO ℃ 302 330 Oxygen removed in DO ％ 100 100 Olefins HYD DO ％ 100 100 HDO selectivity DO ％ 90 30

[0061] Example 2

[0062] Example 2 compares the reaction of a renewable feedstock having the fatty acid composition shown in Table 1 (denoted as Feedstock A) in the presence of a catalytically active material (NiMoS) comprising 2.6 wt% of Ni and 13 wt% of Mo, and Example 2B relates to the reaction of a renewable feedstock having the fatty acid composition shown in Table 1 (denoted as Feedstock B) in the presence of a catalytically active material (NS) comprising 15 wt% of Ni and a small amount (0.3 wt%) of Mo. In both cases, the catalytically active material was sulfided and a certain amount of dimethyl disulfide was added to the reaction stream. Figure 1The actual process design using two types of catalytically active materials in the corresponding layout, but without isomerization, i.e. assuming 124 as product. For comparison, a process design was also calculated using a third type of catalytically active material (5 wt% Pd / C) taken from EP 1681337 B, which has a selectivity to decarboxylation of 97%, corresponding to a ratio between decarboxylation and hydrodeoxygenation of 32:1. In this example, the feed was assumed to consist of C18:2, C18:1, C16:0 in a molar ratio of 3:2:1, essentially corresponding to sunflower oil. The detailed overview of the stream compositions in the different cases is shown in Tables 3 - 6.

[0063] For simplicity, these examples assume a cooled reactor. In practice, the temperature in the deoxygenation section (DO) is limited by cooling a certain amount of the deoxygenated hydrocarbon mixture (112) and combining it with the hydrocracked bottom fraction (106) to provide a heat sink.

[0064] Example 2A (Table 3) and Example 2B (Table 4) show the performance of a NiS-based catalyst corresponding to Example IB. Table 3. Example 2A assumes an ideal configuration of the prehydrogenation reactor (PRE) where the olefins are 100% hydrogenated, but without deoxygenation, while Example 2B corresponds to Example IB with 12% deoxygenation and a hydrodeoxygenation selectivity of 72%. Both Examples 2A and 2B assume 30% hydrodeoxygenation and 70% decarboxylation in the deoxygenation reactor.

[0065] Example 2C (Table 5) shows the performance of a NiMoS-based deoxygenation catalyst similar to Example 1A, but with 95% prehydrogenation, 12% deoxygenation, and a hydrodeoxygenation selectivity of 72% as in Examples IB and 2B. Example 2C assumes 30% hydrodeoxygenation and 70% decarboxylation in the deoxygenation reactor.

[0066] Example 2D (Table 6) shows the performance of a 5 wt% Pd / C-based catalyst reported in EP 1681337 B with a selectivity to decarboxylation of 97% and with 95% prehydrogenation, 12% deoxygenation, and a hydrodeoxygenation selectivity of 72% as in Examples IB, 2B, and 2C. Example 2D assumes 3% hydrodeoxygenation and 97% decarboxylation in the deoxygenation reactor, otherwise similar to Example IB.

[0067] The performance overview of Examples 2A - 2D is shown in Table 7. This clearly shows that for catalysts with high decarboxylation selectivity (2B and 2D), the aviation fuel yield is 5.2% or even 7.5% higher than in Example 2C, while the hydrogen consumption is lower.

[0068] Table 3.

[0069]

[0070]

[0071] Table 4

[0072] 100 102 104 112 126 106 Flow kg / h 100.0 100.0 123.4 123.4 23.4 23.4 Olefins wt% 74.18 3.71 3.01 0.00 0.00 0.00 [H2] wt% 12.09 11.07 9.55 8.49 3.81 3.05 CO, CO2 wt% 0.00 0.31 0.25 5.42 0.00 0.00 C 1-4 ]]> wt% 0.00 74.99 62.47 0.00 0.00 0.00 naphtha (C 5-7 )]]> wt% 0.00 0.00 3.09 3.09 0.00 16.29 Air fuel yield (C 8-17 )]]> wt% 0.00 3.40 17.36 55.53 0.00 77.01 heavy fraction (C 18 )]]> wt% 0.00 5.55 4.50 18.24 96.19 0.00 C5-160℃ wt% 0.00 0.00 7.52 7.52 0.00 39.64 160℃-300℃ wt% 0.00 3.40 12.93 51.10 0.00 53.65 >300℃ wt% 0.00 5.55 4.50 18.24 96.19 0.00

[0073] Table 5.

[0074] 100 102 104 112 126 106 Flow kg / h 100.0 100.0 158.6 158.6 58.6 58.6 Olefins wt% 74.18 3.71 2.34 0.00 0.00 0.00 [H2] wt% 12.09 11.07 8.10 6.78 3.81 3.05 CO, CO2 wt% 0.00 0.31 0.19 0.73 0.00 0.00 [C 1-4 ]]> wt% 0.00 0.54 0.34 2.91 0.00 0.00 naphtha (C 5-7 )]]> wt% 0.00 0.00 6.02 6.02 0.00 16.29 Air fuel yield (C 8-17 )]]> wt% 0.00 3.40 30.61 40.35 0.00 77.01 heavy fraction (C 18 )]]> wt% 0.00 5.55 3.50 35.56 96.19 0.00 C5-160℃ wt% 0.00 0.00 14.65 14.65 0.00 39.64 160℃-300℃ wt% 0.00 3.40 21.98 31.71 0.00 53.65 >300℃ wt% 0.00 5.55 3.50 35.56 96.19 0.00

[0075] Table 6.

[0076] 100 102 104 112 126 106 Flow kg / h 100.0 100.0 107.5 107.5 7.5 7.5 Olefins wt% 74.18 3.71 3.45 0.00 0.00 0.00 [H2] wt% 12.09 11.07 10.51 9.61 3.81 3.05 CO, CO2 wt% 0.00 0.31 0.28 8.49 0.00 0.00 [C 1-4 ]]> wt% 0.00 0.54 0.50 4.22 0.00 0.00 naphtha (C 5-7 )]]> wt% 0.00 0.00 1.14 1.14 0.00 16.29 Air fuel yield (C 8-17 )]]> wt% 0.00 3.40 8.56 65.61 0.00 77.01 heavy fraction (C 18 )]]> wt% 0.00 5.55 5.16 6.74 96.19 0.00 C5-160℃ wt% 0.00 0.00 2.78 2.78 0.00 39.64 160℃-300℃ wt% 0.00 3.40 6.92 63.98 0.00 53.65 >300℃ wt% 0.00 5.55 5.16 6.74 96.19 0.00

[0077] Table 7.

[0078]

Claims

1. A process for producing a hydrocarbon mixture from a decarboxylation feedstock comprising fatty acid esters and / or triglycerides, the hydrocarbon mixture having a final boiling point below 300°C according to ASTM D86 and suitable for use as an aviation fuel, wherein at least 40% of the carbon atoms of the decarboxylation feedstock are contained in C18 side chains, by converting the decarboxylation feedstock in the presence of a material catalytically selective for decarboxylation, such that the ratio between decarboxylation by formation of carbon oxides and decarboxylation by formation of water, as measured by the ratio of C17 paraffins to C18 paraffins in the deoxygenated hydrocarbon mixture, is at least 1.5:1, wherein the decarboxylation conditions include a temperature in the range of 250-400°C, a pressure in the range of 30-150 bar, and a liquid hourly space velocity (LHSV) in the range of 0.1-2, wherein the material catalytically active in decarboxylation includes nickel, supported on a support comprising one or more refractory oxides, and wherein the material catalytically active in decarboxylation includes greater than 5 wt% Ni and less than 70 wt% Ni and less than 1 wt% Co, Mo and W.

2. The process of claim 1, wherein the material catalytically active in decarboxylation includes less than 0.1 wt% Co, Mo and W.

3. The process of claim 1, wherein the refractory oxide is alumina, silica or titania.

4. The process of claim 1, 2 or 3, wherein at least 60% of the carbon atoms of the decarboxylation feedstock are contained in C18 side chains.

5. The process of claim 1, 2 or 3, wherein the decarboxylation feedstock is a saturated decarboxylation feedstock comprising less than 10 wt% olefinic oxygenates.

6. The process of claim 5, wherein the saturated decarboxylation feedstock is provided as a product of a hydrogenation reaction receiving a crude oxygenate feedstock comprising at least 10 wt% olefinic oxygenates and selectively hydrogenating the olefinic oxygenates under olefin prehydrogenation conditions to provide the saturated decarboxylation feedstock.

7. The process of claim 6, wherein the prehydrogenation conditions include a temperature in the range of 150°C to 220°C, a pressure in the range of 30-150 bar, and a liquid hourly space velocity (LHSV) in the range of 0.1-2, wherein the material catalytically active in prehydrogenation includes 5 wt% to 20 wt% molybdenum or tungsten in combination with 1 wt% to 5 wt% nickel and / or cobalt, supported on a support comprising one or more refractory oxides.

8. The process of claim 1, 2 or 3, comprising separating the deoxygenated hydrocarbon mixture according to boiling point to provide a hydrocracked intermediate aviation fuel having a T10 below 205°C and a final boiling point below 300°C according to ASTM D86.

9. The process of claim 1, 2, or 3, wherein the total volume of hydrogen sulfide is at least 50 ppm relative to the volume of molecular hydrogen in the gas phase of the total stream directed to contact the material having catalytic activity in decarboxylation v .

10. The method of claim 9, wherein the total volume of hydrogen sulfide is at least 100 ppm v .

11. The method of claim 9, wherein the total volume of hydrogen sulfide is at least 200 ppm v .

12. The process of claim 9, wherein the hydrogen sulfide is derived from an addition stream comprising one or more sulfur compounds.

13. The process of claim 1, 2 or 3, wherein the decarboxylation feedstock comprises at least 50% wt of triglycerides or fatty acids.

14. The method of claim 1, 2, or 3, further comprising a hydrocracking step under active hydrocracking conditions, wherein the deoxygenated hydrocarbon mixture or a mixture derived therefrom is directed to contact a material catalytically active in hydrocracking.

15. The method of claim 14, wherein the hydrocracking conditions include a temperature in the range of 300-450 °C, a pressure in the range of 30-150 bar, and a liquid hourly space velocity (LHSV) in the range of 0.5-8, wherein the material catalytically active in hydrocracking includes an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten, and molybdenum, an acidic support is one or more of: an amorphous acidic oxide, the amorphous acidic oxide being silica-alumina, or a molecular sieve showing high cracking activity, the molecular sieve having a topology taken from the group of MFI, BEA, and FAU, and an amorphous refractory support including one or more oxides taken from the group comprising alumina, silica, and titania.

16. The method of claim 15, wherein the material catalytically active in hydrocracking includes one or more elemental noble metals taken from platinum or palladium.

17. The method of claim 1, 2, or 3, further comprising subjecting the deoxygenated hydrocarbon mixture to an isomerization step under active isomerization conditions, the active isomerization conditions including a temperature in the range of 250-350 °C, a pressure in the range of 30-150 bar, and a liquid hourly space velocity (LHSV) in the range of 0.5-8, wherein the material catalytically active in isomerization includes an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten, and molybdenum, a molecular sieve showing high isomerization selectivity, the molecular sieve having a topology taken from the group of MOR, FER, MRE, MWW, AEL, TON, and MTT, and an amorphous refractory support including one or more oxides taken from the group comprising alumina, silica, and titania.

18. The method of claim 17, wherein the material catalytically active in isomerization includes one or more elemental noble metals taken from platinum or palladium.

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