Method for production of a transportation fuel

Abstract

The present disclosure relates to a process for production of a dewaxed hydrocarbon fraction from a hydrocarbon feedstock having a cloud point above -5°C wherein the dewaxed hydrocarbon has a cloud point at least 5°C below the hydrocarbon feedstock, comprising the steps of providing a process feed comprising an amount of an ammonia source, hydrogen and an amount of said hydrocarbon feedstock, at a temperature above 200°C, directing said process feed to contact a material catalytically active in isomerization under isomerization conditions to provide a dewaxed hydrocarbon fraction, wherein said ammonia source provides an amount of ammonia corresponding to a concentration of NH3 in the presence of said material catalytically active in hydrodeoxygenation being at least (50) ppbwt and less than 1000 ppmwt. This has the associated benefit that the ammonia source releases ammonia by thermal reaction, such that the presence of ammonia may limit the extent of hydrocracking the isomerization process, as the addition of ammonia source is sufficient for affecting the catalyst, but not sufficient for full deactivation of the zeolite in the catalytically active material.

Description

Title of Invention:Method for production of a transportation fuelTechnical Field

[0001] The present disclosure relates to a method for production of a high yield of aviation fuel and diesel with good cold flow properties by isomerization with decreased cracking side reactions by catalyst moderation with ammonia.Background Art

[0002] Conversion of oxygenates such as triglycerides and fatty acids and other renewables to aviation fuel and diesel by hydroprocessing typically involve a step of hydrodeoxygenation and a step of isomerization.Summary of Invention

[0003] We have now identified that presence of low amounts of NHs in the gas phase when isomerizing linear alkanes reduces the yield loss by hydrocracking to form naphtha and other small hydrocarbons.Definitions

[0004] In the following the term stage shall be used for a section of the process, in which no separation is performed.

[0005] In the following the abbreviation ppmvshall be used to signify volumetric parts per million, e.g. molar gas concentration.

[0006] In the following the abbreviation ppmmoiar shall be used to signify atomic parts per million (106).

[0007] In the following the abbreviation pprriwt and ppbwt shall be used to signify weight parts per million (106) and weight parts per billion (109), e.g. wt / wt concentration.

[0008] In the following the abbreviation wt / wt% shall be used to signify weight percentage.

[0009] In the following the abbreviation vol / vol% shall be used to signify volume percentage for a gas.

[0010] In the following the term renewable feedstock or hydrocarbon shall be used to indicate a feedstock or hydrocarbon originating from biological sources or wasterecycle. Recycled waste of fossil origin such as plastic shall also be construed as renewable.

[0011] A feedstock of biological origin may be defined by tracing the origin, but it may also be defined by the14C content being above 0.5 parts per trillion of the total carbon content.

[0012] In the following the term hydrocarbonaceous shall be used broadly to signify a composition having a structure of hydrocarbons, but possibly comprising an amount of heteroatoms, such as oxygen, sulfur, nitrogen and metals.

[0013] In the following the term oxygenates shall be used to signify a composition being rich in oxygenates, but not necessarily consisting only of oxygenate molecules.

[0014] In the following the term hydrodeoxygenation shall be used to signify removal of oxygen from oxygenates by formation of water in the presence of hydrogen, as well as removal of oxygen from oxygenates by formation of carbon oxides in the presence of hydrogen unless specified otherwise.

[0015] In the following a cold flow property shall be understood as a temperature reflecting the viscosity of a hydrocarbon mixture at low temperatures, including the parameters cloud point, pour point, freezing point and cold filter plugging point (CFPP). Common for these parameters are that they define the requirement to low viscosity of diesel and jet fuel under cold conditions as it is also specified in the standard EN 590 specifying requirements to diesel and similar standards for jet fuel, such as ASTM D1655, and the improvement of cold flow properties or of any one of these parameters shall unless stated otherwise be understood as qualitatively equivalent.

[0016] A material catalytically active in a chemical reaction such as hydrodeoxygenation or hydrocracking shall be understood as a material having significant catalytic activity and preference for said chemical reaction under the conditions used. As it will be realized by the skilled person, most reactions will show an amount of side reactions, but unless otherwise specified the term a material catalytically active in a chemical reaction shall be understood as a combination of a material and conditions under which a commercially relevantamount of conversion takes place with higher selectivity than any other chemical reaction.

[0017] In the following, the term topology of a molecular sieve is used in the sense described in the "Atlas of Zeolite Framework Types," Sixth Revised Edition, Elsevier, 2007, and three letter framework type codes are used in accordance herewith.Technical Problem

[0018] When hydrocarbons are produced from linear oxygenates by hydrodeoxygenation, linear hydrocarbons with elevated melting points and thus poor cold flow properties are produced.

[0019] Good cold flow properties are ensured by converting such linear hydrocarbons by isomerization of the carbon backbone into a branched structure. Unfortunately, isomerization catalysts may also have a high extent of hydrocracking side reaction, which causes a loss of hydrocarbon yield. We have now identified that minimal amounts of amine addition reduces this extent of hydrocracking.

[0020] The processes described in the present disclosure receives a renewable feedstock and / or an oxygenate feedstock which comprises one or more oxygenates taken from the group consisting of triglycerides, fatty acids, resin acids, ketones, aldehydes, alcohols, phenols and aromatic carboxylic acids where said oxygenates originate from one or more of a biological source, a gasification process, a pyrolysis process, Fischer-Tropsch synthesis, methanol based synthesis or a further synthesis process, especially obtained from a raw material of renewable origin, such as originating from plants, algae, animals, fish, vegetable oil refining, domestic waste, used cooking oil, plastic waste, rubber waste or industrial organic waste like tall oil or black liquor. Some of these feedstocks may contain aromatics; especially products derived by pyrolysis or other processes from e.g. lignin and wood or waste products from e.g. frying oil. Depending on source, the oxygenate feedstock may comprise from 1 wt / wt% to 40 wt / wt% atomic oxygen. Feedstock from biological sources will typically comprise around 10 wt / wt% atomic oxygen, and derivation products from biological sources from 1 wt / wt% to 20 wt / wt% or even 40 wt / wt% atomic oxygen.

[0021] For the conversion of renewable feedstocks and / or oxygenate feedstocks into hydrocarbon transportation fuels (jet and Diesel), the feedstocks are together with hydrogen directed to contact a material catalytically active in hydrotreatment, especially hydrodeoxygenation. Especially at elevated temperatures the catalytic hydrodeoxygenation process may have side reactions forming a heavy product e.g. from olefinic molecules in the feedstock. To moderate the release of heat, a liquid hydrocarbon may be added as a heat sink, e.g. as a liquid recycle stream or an external diluent feed. If the process is designed for co-processing of fossil feedstock and renewable feedstock, it is convenient to use the fossil feedstock as diluent, since less heat is released during processing of fossil feedstock, as fewer heteroatoms are released and less olefins are saturated. In addition to moderating the temperature, the recycle or diluent also has the effect of reducing the potential of the feedstock to polymerize. The resulting product stream will be a hydrodeoxygenated intermediate product stream comprising hydrocarbons, typically n-paraffins, and sour gases such as CO, CO2, H2O, H2S, NH3 as well as light hydrocarbons, especially propane and methane.

[0022] Typically, hydrodeoxygenation involves directing the feedstock to contact a catalytically active material typically comprising one or more sulfided metals taken from the group of nickel, cobalt, molybdenum or tungsten, supported on a carrier comprising one or more refractory oxides, typically alumina, but possibly silica or titania. The support is typically amorphous. The catalytically active material may comprise further components, such as boron or phosphorous. The conditions are typically a temperature in the interval 250-400°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.1 -2 on fresh feed basis. Hydrodeoxygenation is typically exothermal, and with the presence of a high amount of oxygenates, the process may beneficially involve intermediate cooling e.g. by quenching with cold hydrogen, feed or product. The feedstock may preferably contain an amount of sulfur to ensure sulfidation of the metals, in order to maintain their activity. If the gas phase comprises less than 10, 50 or 100 pprriv sulfur, a sulfide donor, such as dimethyldisulfide (DMDS) or dipropyldisulfide (DPDS) may be added to the feed.

[0023] For the hydrodeoxygenated intermediate product stream to be used it may be required that the boiling point range is adjusted. A boiling point adjustment mayalso be required if an amount of heavy product is present in hydrodeoxygenated intermediate. The boiling point is adjusted by hydrocracking of long paraffins to shorter paraffins, by directing the hydrodeoxygenated intermediate product to contact a material catalytically active in hydrocracking.

[0024] Hydrocracking involves directing the intermediate hydrodeoxygenated feedstock to contact a material catalytically active in hydrocracking. The material catalytically active in hydrocracking typically comprises an active metal (which may be one or more elemental noble metals such as platinum and / or palladium or one or more sulfided base metals such as nickel, cobalt, tungsten and / or molybdenum), an acidic support (typically a molecular sieve showing high cracking activity, and having a topology such as MFI, BEA and FAU, but amorphous acidic oxides such as silica-alumina may also be used) and a refractory support (such as alumina, silica or titania, or combinations thereof). The catalytically active material may comprise further components, such as boron or phosphorous. Preferred hydrocracking catalysts comprise molecular sieves such as ZSM-5, zeolite Y or beta zeolite.

[0025] The conditions are typically a temperature in the interval 250-400°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8 on fresh feed basis. As hydrocracking is exothermal, the process may involve intermediate cooling e.g. by quenching with cold hydrogen, feed or product. The active metal(s) on the material catalytically active in hydrocracking may be either a noble metal or a base metal. If it is a base metal the intermediate hydrodeoxygenated feedstock including the gas phase is typically directed to contact the material catalytically active in hydrocracking without further purification. This gas phase of this mixture should preferably contain at least 50 ppmvsulfur. If the active metal is a noble metal, purification is required.

[0026] The hydrocracked intermediate product will be branched hydrocarbons, with a shorter length than the feedstock. Depending on the severity of hydrocracking, the hydrocracked intermediate product may contain alkanes having boiling point range (250°C to 320°C) and a freezing point (0°C to 30°C) unsuited for use as transportation fuel.

[0027] Especially if the product has a linear structure, the freezing point may have to be adjusted for the product to be used as a fuel in practice. The freezing point is adjusted by isomerization of n-paraffins to i-paraffins, by directing either the hydrodeoxygenated intermediate product or the hydrocracked intermediate product to contact a material catalytically active in isomerization

[0028] The material catalytically active in isomerization typically comprises an active metal (which may be one or more elemental noble metals such as platinum and / or palladium or one or more sulfided base metals such as nickel, cobalt, tungsten and / or molybdenum), an acidic support (typically a molecular sieve and or zeolite showing high shape selectivity, and having a topology such as MOR, FER, MRE, MWW, AEL, TON and MTT) and a typically amorphous refractory support (such as alumina, silica or titania, or combinations thereof). The catalytically active material may comprise further components, such as boron or phosphorous. Preferred isomerization catalysts comprise 10-MR and 12-MR molecular sieves such as Ell-2, ZSM-11 , ZSM-22, ZSM-23, ZSM-48, SAPO-5, SAPO-11 , SAPO-31 , SAPO-41 , MCM-22, ferrierite and mordenite.

[0029] Typically, isomerization involves directing the intermediate hydrocracked feedstock to contact a material catalytically active in isomerization. The conditions are typically a temperature in the interval 250-400°C, a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8 on fresh feed basis. Isomerization is substantially thermally neutral and consumes only hydrogen in hydrocracking side reactions so only a moderate amount of hydrogen is added in the isomerization reactor. When the active metal on the material catalytically active in isomerization is a noble metal, the hydrocracked feedstock is typically purified by gas / liquid separation to reduce the content of potential catalyst poisons to low levels such as levels of sulfur and carbon oxides to below 1-10 ppm.

[0030] Hydrodeoxygenation of unsaturated fatty acids may produce aromatics as a side reaction. Therefore, even for an oxygenate feedstock comprising less than 2% aromatics, it may be further necessary to direct the isomerized product to contact a material catalytically active in hydrodearomatization.

[0031] In some instances, hydrodearomatization may be satisfactorily carried out in the presence of the material catalytically active in hydroisomerization, but it may also be necessary to have a separate reactor or reactor bed with material catalytically active in hydrodearomatization.

[0032] Such a material catalytically active in hydrodearomatization typically comprises an active metal (either sulfided base metals such as nickel, cobalt, tungsten and / or molybdenum or - after purification, by removal of e.g. hydrogen sulfide - noble metals such as platinum and / or palladium) and a refractory support (such as amorphous silica-alumina, zeolite, alumina, silica or titania, or combinations thereof). Since hydrodearomatization is equilibrium controlled, with high temperatures favoring aromatics, noble metals are preferred as the active metal, since they are active at lower temperatures, compared to base metals.

[0033] Typically, hydrodearomatization involves directing an intermediate product to contact a material catalytically active in hydrodearomatization. As the equilibrium between aromatics and saturation molecules shifts towards aromatics at elevated temperatures, it is preferred that the temperature is moderate. The conditions are typically a temperature in the interval 200-350°C, a pressure in the interval 30- 150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8. The preferred active metal(s) on the material catalytically active in hydrodearomatization is often preferred to be noble metal(s), since noble metal catalysts in general are active at lower temperatures than comparable base metal catalysts. According to the present disclosure, the isomerized product is typically sufficiently purified, as the active metal(s) in the material catalytically active in isomerization is a noble metal. Base metal catalysts may also be used, and in this case the gas phase associated with the intermediate hydroisomerized feedstock preferably contains at least 50 ppmvsulfur. Often a hydrocracking or hydroisomerization catalyst operating at temperatures below 350°C will be able to catalyze moderate hydrodearomatization, e.g. reducing 10 wt / wt% aromatics to below 0.5 wt / wt% aromatics.

[0034] This necessity to combine 3 or 4 catalytically active materials for conversion of renewable feedstocks into jet and diesel naturally complicates the process layout, and the sequence of the materials must be considered carefully. In addition, recycle may be used for three different purposes; gas recycle forefficient use of hydrogen, liquid recycle around the material catalytically active in hydrocracking to maximize the yield of the kerosene fraction and liquid recycle around the material catalytically active in hydrodeoxygenation to limit the temperature increase due to exothermal hydrodeoxygenation reactions.

[0035] As isomerization and hydrodearomatization are preferably carried out using a catalytically active material comprising noble metals, “sour gases”, including hydrogen sulfide, carbon dioxide and ammonia, are removed prior to this reaction. An amount of the intermediate product of hydrocracking may also be recycled to the inlet of the hydrodeoxygenation reactor.

[0036] Operating, with recycle around the hydrocracking reactors, has the benefit of allowing high hydrocracking conversion by multiple passes, rather than by severe condition, thus allowing for full conversion at moderate temperatures, and thus moderate yield loss, thus maintaining a high yield of kerosene and minimized over-cracking to naphtha and lighter. The use of an isomerization catalyst to improve freezing point of the transportation fuel allows increasing the distillation endpoint of the transportation fuel while still meeting freezing point requirement.

[0037] The hydrodeoxygenated hydrocarbon stream is directed to a hydrocracking reactor to contact a catalytically active material comprising either one or more sulfided base metals or one or more elemental noble metals and a refractory support with high acidity. Such a material is active in hydrocracking, and this step provides a stream in which higher boiling hydrocarbons are converted to lower boiling hydrocarbons. The severity of the hydrocracking process will define the boiling point characteristics of the product, and the hydrocracking process will typically be operated with full conversion of the fraction boiling above the diesel range. If hydrocracking severity is selected for full conversion of the fraction boiling above the jet range the yield loss to gases and naphtha will typically be too high.

[0038] The hydrocracked stream may be directed to a separation section, withdrawing water, hydrogen sulfide and ammonia, and providing a sweet hydrocarbon stream. An amount of the sweet hydrocarbon stream is recycled as sweet recycled hydrocarbons and an amount is directed as feed to an isomerization reactor containing a material catalytically active in isomerizationand optionally a material catalytically active in hydrodearomatization. Both materials may be based on a noble metal catalyst, such as platinum, palladium or a combination, in combination with an acidic support, but configurations with sulfided base metal catalysts are also possible. For isomerization the acidic support is preferably shape selective, to provide a selective isomerization, rearranging linear alkanes to branched alkanes, with minimal production of lighter hydrocarbons.

[0039] For hydrodearomatization, an acidic support also contributes to the reaction by ring opening, and in addition as the activity of noble metals is higher than that of base metals, the reaction will take place at lower temperatures. As the equilibrium between aromatic and non-aromatic compounds is shifted away from aromatics at low temperatures, noble metals provide the benefit that the lower temperature matches the equilibrium. Hydrodearomatization may even take place on the material catalytically active in isomerization, which often will have some hydrodearomatization activity.

[0040] The layout provides a conversion of feedstock to diesel, jet range or lighter product, as some or even all heavy hydrodeoxygenated hydrocarbons may be hydrocracked to yield lighter products. Jet / diesel co-production, only diesel or only jet production is possible, and if the conversion of boiling point is mainly carried out in a combined hydrodeoxygenation and hydrocracking stage employing base metal catalysts only, addition of sulfur in the form of DMDS in a single process position is enabled. Furthermore, the adjustment of freezing point may be made selectively by isomerization on a noble metal catalyst, independently of hydrocracking conditions.

[0041] Should it be desired to produce only diesel and no jet fuel, hydrocracking may not be desired. In this case, it may be preferred to either by-pass the hydrocracking reactor or alternatively cool the product prior to this reactor, such that it is inactive. The process plant may be configured for allowing such a configuration with short notice, e.g. by setting up appropriate equipment and control in the control room.Solution to Problem

[0042] As mentioned, isomerization supports formation of branched product with good cold flow properties.

[0043] In the presence of a catalytically active material active in isomerization, both isomerization (restructuring carbon-carbon bonds, but essentially maintaining molecular weight) and hydrocracking (breaking carbon-carbon bonds to produce two smaller molecules) will take place, by a combination of acidic sites supporting breaking of carbon-carbon bonds and metal sites providing reactive hydrogen for hydrogenating molecules on the catalyst surface. When molecules undergo hydrocracking, they will be converted to lower boiling point fractions. In the conversion of heavy diesel to jet fuel, this is desired, but when the product is naphtha, it is commonly of lower value - and especially if methane, ethane and propane molecules are split from longer molecules, the yield loss of liquid products is costly. Therefore, great care is taken in the specific preparation of the catalytically active material to allow only favorable hydrocracking reactions.

[0044] We have however identified that during use, the initial selectivity towards isomerization may shift towards hydrocracking. The shift in selectivity is without being bound by theory believed to be due to a change in catalyst surface; either by increase in acidity, e.g. by release of adsorbed ammonia or structural changes of the refractory support or by reducing metal surface area by sintering or coking of metal nanosize clusters. Irrespective of the cause, we have identified that moderation of the isomerization catalyst by addition of minute amounts of ammonia source, such as methyl diethanolamine (MDEA) or other amines, provides a decrease in cracking activity, without negative impact upon the product cold flow properties.

[0045] If the cause is that acidity is increased, the benefit from adding ammonia is assumed to be neutralization of new acidic sites. If on the other hand, the catalyst change is due to a change in metal surface area; either due to mechanical blockage by coking or by sintering, the effect of ammonia is believed to be rebalancing the relative activities of acidity and hydrogenation activity.

[0046] Therefore, we propose a process with the combined presence of the material catalytically active in hydrodeoxygenation and an amount of ammoniacorresponding to a concentration of NH3 in the presence of said material catalytically active in hydrodeoxygenation being at least 50 ppbwt and less than 1000 pprriwt. The ammonia may be provided to the process in multiple ways, including addition of aqueous ammonia or amines upstream the reactor, a presence of ammonia in the fresh or recycle gas comprising hydrogen which may either be added to the process or collected and recycled to the hydrodeoxygenation process. The ammonia source may also be a solution comprising a salt in neutral form, such as ammonium sulfate or ammonium carbonate, which does not affect the acidity of the feedstock but still has the effect upon the reaction.Advantageous Effects of Invention

[0047] A first aspect of the present disclosure relates to a process for production of a dewaxed hydrocarbon fraction from a hydrocarbon feedstock having a cloud point above -5°C wherein the dewaxed hydrocarbon has a cloud point at least 5°C below the hydrocarbon feedstock, comprising the steps of providing a process feed comprising an amount of an ammonia source, hydrogen and an amount of said hydrocarbon feedstock, at a temperature above 200°C, directing said process feed to contact a material catalytically active in isomerization under isomerization conditions to provide a dewaxed hydrocarbon fraction, wherein said ammonia source provides an amount of ammonia corresponding to a concentration of NHs in the presence of said material catalytically active in hydrodeoxygenation being at least 50 ppbwt and less than 1000 pprriwt such as less than 500 pprriwt.

[0048] This has the associated benefit that the ammonia source releases ammonia by thermal reaction, such that the presence of ammonia may limit the extent of hydrocracking in the isomerization process, as this level of addition of ammonia source is sufficient for affecting the catalyst, but not sufficient for full deactivation of the zeolitic acidity in the catalytically active material.

[0049] The ammonia source may be a chemical ammonia precursor, such as an amine or other compounds reacting to form ammonia, it may be a solution of ammonia or it may molecular ammonia provided in the gas phase.

[0050] A second aspect of the disclosure relates to a process according to an aspect above wherein said concentration of NH3 is at least 100 ppbwt or 300 ppbwt and less than 10 pprriwt or 100 pprriwt.

[0051] The lower limits serves a more rapid effect on the catalyst and the upper limits reduces the risk of deactivation of the zeolite.

[0052] A third aspect of the disclosure relates to a process according to an aspect above wherein said oxygenate feedstock or said process feed comprises at least 50 wt / wt% fatty acid esters or fatty acids.

[0053] This has the associated benefit of such a process feed being available as a waste product or as an energy crop and simple to convert to a transportation fuel.

[0054] A fourth aspect of the disclosure relates to a process according to an aspect above, wherein said oxygenate feedstock or said process feed comprises at least 20 wt / wt% aromatics.

[0055] This has the associated benefit of such a process feed being available as a product from thermal decomposition of waste or energy crops and simple to convert to a transportation fuel.

[0056] A fifth aspect of the disclosure relates to a process according to an aspect above, wherein at least an amount of said ammonia source is provided in a separate liquid ammonia source stream.

[0057] This has the associated benefit of providing and controlling the amount of the ammonia source to the process independently of the composition and handling of the feedstock.

[0058] A sixth aspect of the disclosure relates to a process according to an aspect above, wherein at least an amount of said liquid ammonia source stream comprises an aqueous ammonia solution, a solution of an aqueous ammonia salt, such as ammonium carbonate or ammonium sulfate or an amine, such as dibutylamine, tertbutylamine, monoethanolamine, diethanolamine, methyl diethanolamine,

[0059] This has the associated benefit of these compounds being commercially available and approved for use in the refinery industry.

[0060] A seventh aspect of the disclosure relates to a process according to an aspect above, wherein said liquid ammonia source stream comprises an amount of ammonium, ammonia or amine withdrawn from a downstream process position.

[0061] This has the associated benefit of such a stream being withdrawn from a downstream process, such as either sour water from a three phase separator or a purge stream from an amine column may be a cost effective source of ammonia source.

[0062] A eighth aspect of the disclosure relates to a process according to an aspect above, wherein said liquid ammonia source stream has a pH below 8.

[0063] This has the associated benefit of not influencing the process by neutralization of the feedstock or intermediate products.

[0064] An ninth aspect of the disclosure relates to a process according to an aspect above, further comprising one or more additional process steps taken from the group off hydrodeoxygenation, hydrocracking and hydrodearomatization of intermediate streams in the process.

[0065] This has the associated benefit of such steps adjusting the properties of intermediate streams and product to match specific requirements.

[0066] A tenth aspect of the disclosure relates to a process according to the ninth aspect above, further comprising the step of separating one or more intermediate streams in a gas stream, a non-polar liquid stream and optionally a polar liquid stream optionally prior to directing an amount of the non-polar stream to one or more of said additional process steps.

[0067] This has the associated benefit of enabling separating the non-polar liquid stream from the remainder of streams and optionally upgrading only the nonpolar stream in said additional process steps.

[0068] An eleventh aspect of the disclosure relates to a process plant configured for carrying out the process according to any aspect above.Fig.1

[0069] Fig. 1 shows the yield of aviation fuel over time from a process receiving soy oil as feedstock.Example

[0070] The process of the example illustrated in Fig.1 involves a first stage with hydrodeoxygenation over a catalyst loading comprising a molybdenum on alumina catalyst, followed by a nickel / molybdenum on alumina catalyst, intermediate gas / l iquid separation and isomerization over a noble metal catalyst, comprising Pt and Pd on a support of 10-MR zeolite and alumina.

[0071] In Fig.1 it is seen that a period of unstable operation of the reactor, ended in unplanned shut-down. After start-up, the yield of diesel dropped by approximately 10% to a fluctuating low level (from index 100 to index 85-95), and a further shut- down / start-up cycle was carried out. Following the second start-up, the yield was very low (index 79), but as injection of methyl diethanolamine (MDEA) in an amount averaging approximately 500 ppbwt NH3 equivalent was initiated (at the time indicated by the arrow), a steady increase in diesel yield was observed to index 94. The yield continued to increase towards index 100.

[0072] Without being bound by theory, it is believed that the unplanned shut-down was related to a moderate damage of the catalyst; either by release of surface ammonia or by sintering of metal surfaces. In either case, the optimal balance surface acidity and hydrogen availability is believed to have been shifted towards a relative increase in acidity, which may be moderated by provision of very low amounts of ammonia, such that the selectivity is shifted to favor isomerization over hydrocracking.

Claims

Claims

1. A process for production of a dewaxed hydrocarbon fraction from a hydrocarbon feedstock having a cloud point above -5°C wherein the dewaxed hydrocarbon has a cloud point at least 5°C below the hydrocarbon feedstock, comprising the steps of providing a process feed comprising an amount of an ammonia source, hydrogen and an amount of said hydrocarbon feedstock, at a temperature above 200°C, directing said process feed to contact a material catalytically active in isomerization under isomerization conditions to provide a dewaxed hydrocarbon fraction, wherein said ammonia source provides an amount of ammonia corresponding to a concentration of NH3 in the presence of said material catalytically active in hydroisomerization being at least 50 ppbwt and less than 1000 ppmwt.

2. The process according to claim 1 wherein said corresponding concentration of NH3 is at least 100 ppbwt or 300 ppbwt and less than 10 ppmwt or 100 ppmwt.

3. The process according to claim 1 or 2 wherein said hydrocarbon feedstock comprises at least 50 wt / wt% n-paraffins.

4. The process according to claim 1 , 2 or 3 wherein said hydrocarbon feedstock comprises at least 20 wt / wt% aromatics.

5. The process according to claim 1 , 2, 3 or 4 wherein at least an amount of said ammonia source is provided in a separate liquid ammonia source stream.

6. The process according to claim 1 , 2, 3, 4 or 5 wherein at least an amount of said liquid ammonia source stream comprises an aqueous ammonia solution, a solution of an aqueous ammonia salt, such as ammonium carbonate or ammonium sulfate or an amine, such as dibutylamine, tertbutylamine, monoethanolamine, diethanolamine, methyl diethanolamine,

7. The process according to claim 1 , 2 , 3, 4, 5 or 6, wherein said liquid ammonia source stream comprises an amount of ammonium, ammonia or amine withdrawn from a downstream or upstream process position.

8. The process according to claim 1 , 2, 3, 4, 5, 6 or 7, wherein said liquid ammonia source stream has a pH below 8.

9. The process according to claim 1 , 2, 3, 4, 5, 6, 7 or 8, further comprising one or more additional process steps taken from the group of hydrodeoxygenation, hydrocracking and hydrodearomatization of streams in the process.

10. The process according to claim 9, further comprising the step of separating one or more intermediate streams in a gas stream, a non-polar liquid stream and optionally a polar liquid stream prior to directing an amount of the non-polar stream to one or more of said additional process steps.

11. The process according to according to claim 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein said hydrocarbon feedstock is provided by hydrodeoxygenation of an oxygenate stream.

12. The process according to according to claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 , wherein the material catalytically active in isomerization comprises either elemental noble metals such as platinum and / or palladium or sulfided base metals such as nickel, cobalt, tungsten and / or molybdenum, an acidic support comprising a molecular sieve having a structure such as MOR, FER, MRE, MWW, AEL, TON and MTT and a refractory support such as alumina, silica or titania, or combinations thereof and wherein isomerization conditions involves a temperature in the interval 250-400°C, a pressure in the interval 20-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8.

13. A process plant comprising a means for provision of an ammonia source in a process feed and configured for carrying out the process according to any claim above.

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