A hydroprocessing method for producing bio-jet fuel

Abstract

The application discloses a hydrogenation method for preparing bio-jet fuel, wherein oil and fat raw materials are reacted in a hydrogenation treatment reaction zone, liquid hydrocarbons obtained are reacted in a selective hydrocracking reaction zone, selective hydrocracking reaction effluents obtained are directly reacted in a hydroisomerization reaction zone, and bio-jet fuel is obtained after separation of hydroisomerization reaction effluents. The method provided by the application has high bio-jet fuel yield and stable bio-jet fuel properties.

Description

Technical Field

[0001] This invention relates to a hydrogenation method for preparing biojet fuel, specifically a hydrogenation method for producing biojet fuel from oil-based feedstocks. Background Technology

[0002] With the supply of traditional fossil fuels tightening and the pressure to reduce carbon dioxide emissions increasing, how to effectively reduce carbon dioxide emissions while increasing fuel supply is a significant challenge facing the oil refining industry. Biodiesel fuel, produced from renewable biomass such as animal and vegetable oils or agricultural and forestry waste, has significantly lower greenhouse gas emissions over its entire life cycle than fossil diesel fuel. Developing biomass fuels is considered one of the effective means to address this issue.

[0003] The main reasons why biofuels are gradually attracting attention are as follows: 1. Biofuels are a renewable energy source; 2. The carbon content of biofuels is similar to that of existing fuels; 3. The carbon dioxide absorbed by biofuel precursors can reduce net greenhouse gas emissions; 4. Bioenergy is distributed more evenly than fossil fuels.

[0004] The traditional method for converting vegetable oils or other fatty acid derivatives into liquid fuels is transesterification. Transesterification involves the exchange of alcohols with a catalyst to convert the triglycerides that form vegetable oils into the corresponding fatty acid alkyl esters, typically fatty acid methyl esters. However, the low-temperature fluidity of fatty acid methyl esters limits their use in cold environments. This low-temperature fluidity is determined by the chain characteristics of their fatty acids; the presence of carbon-carbon double bonds can improve low-temperature fluidity but reduces the stability of fatty acid methyl esters. Furthermore, the presence of oxygen in fatty acid methyl esters leads to higher NOx emissions compared to conventional diesel fuels.

[0005] CN103059902B discloses a method for preparing jet fuel blending components using animal and vegetable oils as raw materials, comprising: animal and vegetable oils entering a first hydrogenation reactor, where they undergo a hydrodeoxygenation reaction in the presence of hydrogen and contact with a hydrotreatment catalyst; the resulting hydrocarbon liquid stream entering an intermediate fractionation tower, where the C16-C24 fractions obtained from fractionation enter a second hydrogenation reactor from the top, where they undergo selective cracking in a cracking section in the presence of hydrogen, and then enter an isomerization section for isomerization; the resulting C6-C15 fractions enter the isomerization section from the middle for isomerization; and the resulting hydrocarbon liquid stream from the second hydrogenation reactor entering a product fractionation tower for fractionation to obtain jet fuel blending components.

[0006] CN103059900B discloses a method for preparing jet fuel, wherein the method comprises: (1) contacting vegetable oil and / or animal fat, hydrogen and a hydrodeoxygenation catalyst under hydrodeoxygenation conditions to obtain C8-C24 n-alkanes; (2) contacting the C8-C24 n-alkanes and hydrogen with a hydroisomerization catalyst under hydroisomerization conditions; (3) fractionating the product after contact in step (2) and hydrogen with a hydrorefining catalyst under hydrorefining conditions to obtain jet fuel; wherein the hydroisomerization catalyst contains a support and a metal active component, the support contains a silicon-phosphorus-aluminum molecular sieve, and the metal active component contains one or more of Group VIII metal elements.

[0007] In the prior art, the preparation of hydroisomerization catalysts usually involves ammonium exchange after crystallization followed by extrusion molding. However, the alkali metal content in the resulting catalyst is generally below 0.1 wt%, which is difficult to further reduce, thus limiting the catalytic activity of the catalyst. Therefore, how to further improve the catalytic activity of hydroisomerization catalysts is also an important problem in the prior art. Summary of the Invention

[0008] The purpose of this invention is to provide a hydrogenation method for preparing biojet fuel based on existing technology, so as to solve the problem of low biojet fuel yield in existing technology.

[0009] The hydrogenation method for preparing biojet fuel provided by this invention includes:

[0010] (1) Oily feedstock and hydrogen are introduced into the hydrotreating reaction zone together. Under the hydrotreating reaction conditions, they react with the hydrotreating catalyst to obtain a hydrotreating reaction effluent. The obtained hydrotreating reaction effluent is separated to obtain liquid hydrocarbon, water and gas streams. The active metal component of the hydrotreating catalyst is at least one metal component selected from Group VIII and / or at least one metal component selected from Group VIB.

[0011] (2) The liquid hydrocarbon obtained in step (1) enters the selective hydrocracking reaction zone and reacts with the selective hydrocracking catalyst under selective cracking reaction conditions to obtain the selective hydrocracking effluent.

[0012] (3) The selective hydrocracking reaction effluent obtained in step (2) directly enters the hydroisomerization reaction zone and reacts with the hydroisomerization catalyst to obtain the hydroisomerization reaction effluent. The obtained hydroisomerization reaction effluent is then separated into gas and liquid and fractionated to obtain biojet fuel.

[0013] The hydroisomerization catalyst comprises a support and an active metal component supported on the support. The support contains ZSM-48 molecular sieve, wherein the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve is not less than 40, the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200 m2 / g, and the crystals of the ZSM-48 molecular sieve are ellipsoidal with a major axis not exceeding 700 nm and an aspect ratio of 1-3:1.

[0014] The active metal component is Pt and / or Pd;

[0015] In the hydroisomerization catalyst, based on the total amount of the hydroisomerization catalyst, the content of molecular sieve on a dry basis is 20-80% by weight, and the content of the active metal component on an elemental basis is 0.1-20% by weight.

[0016] Specifically, based on the total amount of the carrier, the content of alkaline metal oxides in the carrier is no higher than 0.001 by weight.

[0017] In this invention, the oily raw materials are animal and vegetable oils and / or waste cooking oil. The animal and vegetable oils include vegetable oils and animal fats, as well as raw materials containing glycerides and free fatty acids, and fatty acid methyl esters or fatty acid ethyl esters prepared from vegetable oils and / or animal fats through transesterification. The waste cooking oil refers to oily waste products that are no longer suitable for consumption, generated during the processing and consumption of animal and vegetable oils. This includes fatty acids and acidified oils produced during the production of edible oil from oilseeds; various types of waste cooking oil such as frying waste oil, kitchen waste oil, and swill oil generated from the use of edible oil by households, hotels, restaurants, and food production enterprises; animal fats by-products of meat production and processing; and edible oils that have exceeded their shelf life.

[0018] In one embodiment of the present invention, the hydrogenation reaction conditions are: reaction temperature 250-450℃, reaction pressure 3.0-10.0 MPa, and volume hourly space velocity 0.1-10.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 300-2000 Nm 3 / m 3 ;

[0019] Preferably, the hydrogenation reaction conditions are: reaction temperature 300-400℃, reaction pressure 4.0-8.0 MPa, and volume hourly space velocity 0.5-5.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500-1500 Nm. 3 / m 3 .

[0020] In one embodiment of the present invention, the support for the hydrotreating catalyst is selected from one or more of alumina, silicon oxide, titanium oxide, and zirconium oxide, the Group VIII metal component is cobalt and / or nickel, and the Group VIB metal component is molybdenum and / or tungsten; based on oxides and the hydrotreating catalyst, the content of cobalt and / or nickel is 1-10% by weight, and the content of molybdenum and / or tungsten is 10-45% by weight.

[0021] To maintain the sulfided state of the hydrotreating catalyst, it is preferable to add a sulfiding agent to the oil-based feedstock, wherein the concentration of the sulfiding agent is 0.01-0.5% by weight. The sulfiding agent is H₂S, CS₂, dimethyl disulfide, methyl sulfide, or di-tert-butyl polysulfide (SZ). 54 One or more of n-butyl sulfide and thiophene.

[0022] The reactor in the hydrotreating reaction zone is a fixed-bed reactor. The reactor can have multiple beds. The reaction temperature rise can be controlled by injecting cold hydrogen between the beds, or by circulating oil, or by using both methods.

[0023] In the hydrotreating reaction zone, oil and fat feedstocks mainly undergo olefin saturation and hydrodeoxygenation reactions. Oxygen in the feedstocks is primarily removed as water. The effluent from the hydrotreating reaction mainly consists of alkanes with 8-24 carbon atoms, along with water, carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia, and hydrogen.

[0024] In one embodiment of the present invention, the effluent from the hydrogenation treatment reaction enters a separator for gas-liquid separation to obtain a liquid stream, water, and a gas stream. The obtained liquid stream sequentially enters a stripping tower for stripping and a dehydration tower for dehydration to remove dissolved hydrogen sulfide, ammonia, and water, thereby obtaining liquid hydrocarbons.

[0025] The gas stream can be directly recycled or purified by a hydrogen purification unit to obtain hydrogen-rich gas, which is then recycled. The hydrogen purification unit can employ conventional pressure swing adsorption (PSA) technology or membrane separation technology.

[0026] In one embodiment of the present invention, the separator is selected from any combination of two or more of the following: hot high-pressure separator, hot low-pressure separator, cold high-pressure separator, and cold low-pressure separator.

[0027] In step (2) of this invention, the obtained liquid hydrocarbons enter the selective hydrocracking reaction zone and react with a selective hydrocracking catalyst under selective cracking reaction conditions. This moderately cracks the high-carbon hydrocarbons while retaining as many C18 and lower hydrocarbons as possible, yielding the selective hydrocracking effluent. In one embodiment of this invention, the mass percentage of the fraction with a temperature >310°C in the liquid phase of the obtained selective hydrocracking effluent is not greater than 50%, preferably not greater than 30%.

[0028] In one embodiment of the present invention, the selective hydrocracking catalyst comprises a support and an active metal component supported on the support. The support contains one or more of amorphous silica-alumina, SAPO-11, SAPO-31, SAPO-41, ZSM-22, ZSM-23, and ZSM-48 molecular sieves. The active metal component is selected from one or more of Pt, Pd, Rh, Ru, Ag, and Au. The content of amorphous silica-alumina or molecular sieves in the selective hydrocracking catalyst, based on the total amount of the selective hydrocracking catalyst, is 40-99.9% by weight on a dry basis. The content of the active metal component, based on elemental composition, is 0.1-0.8% by weight, with the remainder being alumina.

[0029] The selective hydrocracking catalyst described in this invention is a reduced selective hydrocracking catalyst. When in use, the metal active component of the selective hydrocracking catalyst is in a reduced state. Therefore, the selective hydrocracking catalyst needs to be reduced and activated before use: under a hydrogen atmosphere, the reduction temperature is 300-500℃ and the reduction time is 2-6h.

[0030] In one embodiment of the present invention, the selective hydrocracking reaction conditions are: reaction temperature 250-500℃, reaction pressure 1.0-15.0 MPa, and volume hourly space velocity 0.1-10.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200-1500 Nm 3 / m 3 ,

[0031] Preferably, the selective hydrocracking reaction conditions are: reaction temperature 300-400℃, reaction pressure 2.0-8.0 MPa, and volume hourly space velocity 0.5-5.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 300-1000 Nm 3 / m 3 .

[0032] In step (3) of this invention, the selective hydrocracking reaction effluent enters the hydroisomerization reaction zone directly without any separation, and reacts with the hydroisomerization catalyst. In one embodiment of this invention, the hydroisomerization reaction conditions are: reaction temperature 200-500℃, reaction pressure 1.0-15.0MPa, and volume hourly space velocity 0.1-10.0h. -1 Hydrogen-to-oil volume ratio 200-1500 Nm 3 / m 3 ;

[0033] Preferably, the hydroisomerization reaction conditions are: reaction temperature 280-380℃, reaction pressure 2.0-8.0 MPa, and volume hourly space velocity 0.5-5.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 300-1000 Nm 3 / m 3 .

[0034] In one embodiment of the present invention, the content of molecular sieve in the hydroisomerization catalyst is 30-70% by weight on a dry basis, based on the total amount of the hydroisomerization catalyst, and the content of the active metal component is 0.2-10% by weight on an elemental basis.

[0035] In one embodiment of the present invention, the hydroisomerization catalyst further contains a binder, wherein the binder is alumina and / or silicon oxide;

[0036] Based on the total amount of hydroisomerization catalyst, the binder content is 20-80% by weight.

[0037] In one embodiment of the present invention, the aspect ratio of the ZSM-48 molecular sieve is 1-2:1; the grain size of the ZSM-48 molecular sieve is 300-700 nm, preferably 400-600 nm; and the specific surface area of ​​the ZSM-48 molecular sieve is 200-280 m². 2 / g; The pore volume of ZSM-48 molecular sieve is 0.2-0.3 mL / g.

[0038] In this invention, the ZSM-48 molecular sieve has an ellipsoidal morphology with a small aspect ratio, a high silicon-to-aluminum ratio, and a large specific surface area. The alkali metal content in the support is extremely low, and the resulting hydroisomerization catalyst has higher catalytic activity in the hydroisomerization reaction of liquid hydrocarbons.

[0039] In this invention, the content of alkali metal oxides was determined using a Rigaku Electric Industries, Ltd. 3271E X-ray fluorescence spectrometer (XRF) to analyze the composition of the sample. Those skilled in the art will understand that the standard accuracy of XRF testing is 10 ppm; therefore, a test result of 0 indicates that the content of alkali metal oxides is no higher than 0.001% by weight.

[0040] In one embodiment of the present invention, the method for preparing the hydroisomerization catalyst includes the following steps:

[0041] Step 1: Shape the dried powder of ZSM-48 molecular sieve into a molded carrier;

[0042] The molar ratio of silica to alumina in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200 m². 2 / g, the ZSM-48 molecular sieve crystals are ellipsoidal, with a major axis not exceeding 700nm and an aspect ratio of 1-3:1;

[0043] Based on the mass of the dried ZSM-48 molecular sieve powder, the moisture content of the dried ZSM-48 molecular sieve powder is less than 15% by weight.

[0044] Step 2: Perform ammonium exchange on the molded carrier;

[0045] Step 3: Introduce an active metal component onto the product obtained in Step 2 to obtain a hydroisomerization catalyst;

[0046] The active metal component is Pt and / or Pd.

[0047] In this invention, the dried ZSM-48 molecular sieve powder refers to dried ZSM-48 molecular sieve powder. Drying is a conventional operation in the art, requiring only that the dried ZSM-48 molecular sieve powder meet the aforementioned moisture content requirements. In conventional catalyst preparation processes, the dried and calcined molecular sieve powder typically undergoes ammonium exchange in a solution before drying, shaping, and calcining. However, this process results in a limited catalytic activity, with the alkali metal content in the support generally between 0.01-1% by weight after conventional ammonium exchange. Furthermore, directly processing the molecular sieve powder after ammonium exchange is challenging. The inventors of this invention have discovered that shaping the dried ZSM-48 molecular sieve powder before ammonium exchange significantly reduces the alkali metal content in the support and improves the catalyst's catalytic activity.

[0048] In this invention, the method for testing the moisture content is as follows: Take a mass M of dried ZSM-48 molecular sieve powder and place it in an oven. Dry it at 105-110℃ for about 6-8 hours until the sample weight no longer changes. Weigh the dried sample and record it as M. After drying, the moisture content of the dried ZSM-48 molecular sieve powder can be calculated.

[0049] Moisture content (wt%) = (mm after drying) / mm × 100%.

[0050] In this invention, preferably, the preparation method of the ZSM-48 molecular sieve includes the following steps:

[0051] (1) Provide a mixture containing silicon source, alkali source, aluminum source, template agent, water and molecular sieve mother liquor and seed crystals;

[0052] (2) The mixture is subjected to a crystallization reaction; the conditions for the crystallization reaction include: reacting at 20℃-50℃ for 1-20h, reacting at 50℃-80℃ for 1-34h, and then reacting at 80℃-180℃ for 1-70h.

[0053] (3) The mixture obtained from the crystallization reaction in step (2) is subjected to solid-liquid separation to obtain ZSM-48 molecular sieve and molecular sieve mother liquor. The molecular sieve mother liquor is returned to step (1).

[0054] The method further includes, optionally, step (4), which includes: acidifying and depositing the molecular sieve mother liquor, then performing solid-liquid separation, and returning the filtrate to step (1);

[0055] In step (1), the mass percentage of the added seed crystals is not less than 10% of the mass percentage of the silicon source, and the silicon source is SiO2.

[0056] According to the present invention, the ZSM-48 molecular sieve is prepared by reusing the molecular sieve mother liquor and introducing seed crystals, which is beneficial to the formation of small crystals. In this invention, the crystallization process is carried out in three stages at different temperatures, strictly controlling the progress and temperature of the crystallization reaction. Compared with the prior art, setting the crystallization reaction process at a low temperature helps to control the growth of crystals.

[0057] In this invention, those skilled in the art will understand that step (3) or steps (3) and (4) can be arbitrarily selected to obtain the molecular sieve mother liquor. When the method provided by this invention includes step (4), those skilled in the art will understand that the filtrate provides at least a portion of the molecular sieve mother liquor described in step (1). Using the above-preferred preparation method, the reuse of the molecular sieve mother liquor and the introduction of seed crystals are beneficial to the formation of small crystals.

[0058] In this invention, the proportions of each raw material in step (1) can be adjusted according to actual needs. In order to improve the performance of the molecular sieve in the ZSM-48 molecular sieve precursor, and thus further improve the catalytic performance of the catalyst, preferably, the composition of each component in the mixture in step (1) calculated by molar amount satisfies the following relationship:

[0059] R / SiO2 = 0.01-0.4, preferably 0.01-0.08;

[0060] M + / SiO2 = 0.01-0.4, preferably 0.1-0.2;

[0061] Al2O3 / SiO2 = 0-0.02, preferably 0.01-0.015;

[0062] H2O / SiO2 = 5-30, preferably 5-20;

[0063] Wherein, SiO2 refers to SiO2 in the silicon source, R represents the template agent, and M... + Indicates the alkali source.

[0064] According to the present invention, preferably, the conditions for the crystallization reaction in step (2) include: reacting at 20℃-50℃ for 6-20h, reacting at 50℃-80℃ for 12-34h, and then reacting at 80℃-180℃ for 48-70h.

[0065] In this invention, the amount of seed crystals used is relatively large. Preferably, the mass percentage of the added seed crystals in step (1) is 10-30% of the mass percentage of the silicon source, and more preferably 20-30%. By adopting the above preferred embodiment, it is beneficial to form more crystal nuclei, and the molecular sieve prepared has the characteristic of small crystal grains.

[0066] According to the present invention, preferably, in the mixture described in step (1), the amount of the molecular sieve mother liquor is less than the amount of water. More preferably, the mass percentage of the molecular sieve mother liquor added in step (1) to the total mass of the molecular sieve mother liquor and water in step (1) is not greater than 50%, more preferably 10-30%. In the above preferred cases, it is beneficial to form a molecular sieve with small crystals and a high specific surface area.

[0067] According to the present invention, preferably, in step (4), the acidification deposition includes: adding acid to the molecular sieve mother liquor to adjust the pH value to 5-7, preferably 5-6.5.

[0068] Preferably, the acidification deposition time is 0.5-4 hours.

[0069] In this invention, the selection range for the silicon source, alkali source, aluminum source, and template agent in step (1) is relatively wide, and the above-mentioned raw materials are all conventional choices in the art. The above-mentioned raw materials should generally be mixed into a uniform gel by appropriate means, for example, by stirring.

[0070] According to the present invention, preferably, the silicon source is selected from at least one of silica sol, silica, fumed silica, water glass and tetraethyl orthosilicate; more preferably, silica sol.

[0071] According to the present invention, preferably, the alkali source is selected from alkaline metal salts, and more preferably at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide; more preferably sodium hydroxide.

[0072] According to the present invention, preferably, the aluminum source is selected from at least one of boehmite, aluminum sulfate, aluminum isopropoxide and sodium aluminate; more preferably, it is boehmite.

[0073] According to the present invention, preferably, the template agent is selected from at least one of ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-anetanediamine, hexamethylammonium bromide, hexamethylammonium chloride, and hexamethylammonium hydroxide; more preferably, at least one of 1,6-hexanediamine, hexamethylammonium bromide, hexamethylammonium chloride, and hexamethylammonium hydroxide.

[0074] In this invention, preferably, the seed crystal is a ZSM-48 molecular sieve seed crystal, wherein the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve seed crystal is not less than 40, preferably 45-500. The silicon-aluminum ratio in the ZSM-48 molecular sieve seed crystal mainly depends on the feeding and preparation method of the silicon and aluminum sources in the raw materials.

[0075] Currently, in the XRD diffraction patterns of ZSM-48 molecular sieve raw powder synthesized using existing techniques and calcined, the peak positions are generally at 2θ angles of 7.5°, 21.2°, 22.8°, and 31.3°, with the highest peak at 21°-22° and a weaker peak at 7°-8°. Researchers of this invention have discovered that by employing a specific synthesis method, the preferred ZSM-48 molecular sieve seed crystals of this invention can be prepared. In the X-ray diffraction pattern of these seed crystals after calcination, the relative peak height of the diffraction peak at 2θ angle of 7°-8° is significantly higher than that of the diffraction peak at 7°-8° in molecular sieves obtained using existing techniques. Preferably, in the X-ray diffraction pattern of the calcined ZSM-48 molecular sieve seed crystals, using the peak height of the diffraction peak at 2θ angle of 21°-22° as a reference value, the peak height of the diffraction peak at 2θ angle of 7°-8° is not less than 70% of the reference value, preferably 75%-135%. For example, the lower limit of the peak height range of the 7°-8° diffraction peak can be 75%, 80%, 90% of the reference value, etc., and the upper limit of the peak height range of the 7°-8° diffraction peak can be 135%, 120%, 110%, 100% of the reference value, etc. Due to the influence of factors such as sample and instrument, the specific peak position of the 2θ angle in this invention may have a deviation of ±0.5°. The purpose of calcination is to remove impurities such as template agents in the molecular sieve powder to obtain more accurate XRD characterization results, and it will not have a substantial impact on the diffraction peaks in the XRD pattern of the molecular sieve itself. Therefore, the calcination conditions are based on the removal of impurities. For example, calcination can be carried out at 400-700℃ for 1-8 hours. In the preparation example of this invention, the ZSM-48 molecular sieve seed crystals were calcined at 600℃ for 4 hours before characterization.

[0076] In one embodiment of the present invention, the molding in step one includes: mixing dried powder of ZSM-48 molecular sieve, binder and additives, and then molding and calcining.

[0077] The auxiliary agent is an inorganic acid, preferably nitric acid and / or hydrochloric acid;

[0078] The binder is selected from at least one of alumina, silicon dioxide, boehmite, and silica sol, preferably boehmite.

[0079] In one embodiment of the present invention, the amount of the binder is 20-60 parts by weight relative to 100 parts by weight of dried ZSM-48 molecular sieve powder, and the amount of the additive is 2-20 parts by weight.

[0080] The roasting conditions include: a roasting temperature of 300-600℃ and a roasting time of 2-10h.

[0081] In one embodiment of the present invention, the ammonium exchange in step two includes: contacting the molded carrier with an aqueous solution of ammonium salt;

[0082] The conditions for ammonium exchange include: a temperature of 70-120℃, preferably 80-100℃; and a time of 1-8h, preferably 2-5h.

[0083] The concentration of ammonium salt in the aqueous solution is 0.01-1 mol / L, preferably 0.1-1 mol / L.

[0084] The ammonium salt is selected from at least one of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium acetate.

[0085] In one embodiment of the present invention, the method of introducing the active metal component in step three includes: impregnating the product in step two with a solution of a soluble compound containing the active metal component, and then drying and calcining it to obtain the hydroisomerization catalyst.

[0086] The soluble compound containing the active metal component is selected from at least one of tetraamminepalladium nitrate, tetraamminepalladium acetate, dichlorotetraamminepalladium, tetraammineplatinum nitrate, tetraammineplatinum acetate, and dichlorotetraammineplatinum.

[0087] The drying temperature is 80-120℃, and the drying time is 2-6 hours;

[0088] The roasting temperature is 400-500℃, and the roasting time is 2-6 hours.

[0089] The hydroisomerization catalyst of this invention is a reduced-state hydroisomerization catalyst with good isomer selectivity. In use, the metal active component of the hydroisomerization catalyst is in a reduced state; therefore, the preparation method further includes: reducing and activating the hydroisomerization catalyst obtained in step three under a hydrogen atmosphere. The reduction and activation process can be carried out using conventional methods in the art. Preferably, the reduction temperature is 300-500℃, and the reduction time is 2-6 hours.

[0090] The preferred method for preparing the hydroisomerization catalyst of this invention has a short preparation process and is simple to operate. Based on the ZSM-48 molecular sieve with a specific structure, the method adopts a pre-forming and then ammonium exchange approach, which reduces the difficulty of post-processing. At the same time, the alkali metal content in the catalyst is extremely low, and the resulting hydroisomerization catalyst has higher catalytic activity in the hydroisomerization reaction of liquid hydrocarbons.

[0091] In one embodiment of the present invention, the resulting hydroisomerization reaction effluent enters a separator for gas-liquid separation to obtain a liquid stream and a gas stream. The obtained gas stream is recycled, and the obtained liquid stream enters a fractionation tower for fractionation to obtain bio-jet fuel. The obtained bio-jet fuel is almost entirely composed of saturated alkanes, has stable properties, and meets the requirements for HEFA-SPK as a No. 3 jet fuel.

[0092] The features of this invention are:

[0093] (1) This invention can process oily feedstocks to obtain bio-jet fuel in high yield. The invention involves selectively hydrocracking the liquid hydrocarbons obtained from hydrotreatment, moderately cracking the high-carbon-number hydrocarbons, and then introducing them into a hydroisomerization reaction zone where they react with a highly active hydroisomerization catalyst. The reaction effluent is then separated to obtain bio-jet fuel. Furthermore, the bio-jet fuel prepared using this method is entirely composed of saturated alkanes, exhibiting stable properties and meeting the requirements for HEFA-SPK as a No. 3 jet fuel.

[0094] (2) The preferred hydroisomerization catalyst of the present invention has higher catalytic activity in the hydroisomerization reaction of liquid hydrocarbons and can significantly improve the yield of the target product. Attached Figure Description

[0095] Figure 1 A schematic flowchart of one embodiment of the hydrogenation method for preparing biojet fuel provided by the present invention;

[0096] Figure 2 The X-ray diffraction pattern of seed crystal A1 obtained in Preparation Example 1-1 after calcination;

[0097] Figure 3 The X-ray diffraction pattern of seed crystal A3 obtained in Preparation Examples 1-3 after calcination;

[0098] Figure 4 This is a SEM image of the ZSM-48 molecular sieve obtained in Preparation Example 2-1. Detailed Implementation

[0099] The present invention will be further described below with reference to the accompanying drawings, but this description does not limit the scope of the invention.

[0100] Figure 1 This is a schematic flowchart of one embodiment of the hydrogenation method for preparing biojet fuel provided by the present invention. Figure 1As shown, oil-based feedstock 1, first fresh hydrogen gas 2, and first recycled hydrogen gas 24 are fed together into heater 3 and heated to the required reaction temperature. The material from the heater outlet enters the fixed-bed hydrotreating reactor 4 in the hydrotreating reaction zone. Under hydrotreating reaction conditions, it reacts with the hydrotreating catalyst to obtain hydrotreating reaction effluent. The obtained hydrotreating reaction effluent enters the hot high-pressure separator 5 for gas-liquid separation. The resulting gaseous stream enters the cold high-pressure separator 6 for further gas-liquid separation. The water 9 obtained from the cold high-pressure separator 6 is discharged from the device. The separated gaseous stream 12 is processed and then pressurized by the circulating hydrogen compressor 13 for recycling. The first liquid stream 7 obtained from the hot high-pressure separator 5 and the second liquid stream 8 obtained from the cold high-pressure separator 6 are fed together as liquid hydrocarbons into the selective hydrocracking reaction zone.

[0101] The liquid hydrocarbon, the second fresh hydrogen 10, and the second recycled hydrogen 19 together enter the selective hydrocracking reactor 11 in the selective hydrocracking reaction zone. Under selective cracking reaction conditions, they react with the selective hydrocracking catalyst to obtain selective hydrocracking effluent 14, which directly enters the hydroisomerization reactor 15 in the hydroisomerization reaction zone. Under hydroisomerization reaction conditions, it reacts with the hydroisomerization catalyst to obtain hydroisomerization effluent 16, which enters the high-pressure separator 17 for gas-liquid separation. The obtained gas phase stream is recycled as the second recycled hydrogen 19, and the obtained third liquid phase stream 18 enters the fractionation tower 20 for fractionation to obtain bio-naphtha 21, bio-jet fuel 22, and biodiesel 23.

[0102] The following embodiments will further illustrate the present invention, but should not be construed as limiting the present invention.

[0103] The hydroisomerization catalysts used in the examples and comparative examples were prepared using the following process.

[0104] In the following preparation examples and comparative examples, the samples were characterized by XRD using a Bruker D5005 diffractometer with CuKα rays (λ = 0.154 nm), a tube voltage of 40 kV, a tube current of 30 mA, a scanning range of 5°–35°, a step size of 0.013°, and a step speed of 1 step per second. The morphology and size of the samples were characterized using a Hitachi S-4800 scanning electron microscope (SEM) with an accelerating voltage of 20 kV.

[0105] The composition of the samples, including the content of alkali metal oxides, was determined using a Rigaku Electric Industries, Ltd. (RIGE) 3271E X-ray fluorescence spectrometer (XRF) from Japan. Sample preparation was performed using a pellet method, and the measurement conditions were a rhodium target with an end window, a tube voltage of 50 kV, and a tube current of 50 mA.

[0106] The pore structure parameters of the product, such as specific surface area and pore volume, were measured using nitrogen adsorption and BET methods.

[0107] The following preparation examples illustrate the preparation of seed crystals.

[0108] Preparation Example 1-1

[0109] Aluminum sulfate, hexamethyldiamine hydroxide (HMOH), sodium hydroxide, and deionized water were mixed in a certain proportion and stirred for 30 minutes. Silica sol was then added. The molar ratio of each substance was n(Al₂O₃):(HMOH):n(Na₂O₃). + The mixture of n(H₂O):n(SiO₂) = 0.01:0.03:0.3:8:1 was transferred to a crystallization vessel and crystallized at room temperature with stirring at 400 rpm for 6 hours; then crystallized at 80℃ for 24 hours, followed by crystallization at 180℃ for 48 hours. After crystallization, the mixture was filtered, and the solid product was dried at 120℃ for 6 hours to obtain seed crystal A1. Seed crystal A1 was calcined at 600℃ for 4 hours, and the XRD diffraction peaks were observed. Figure 1 The peak height of the diffraction peak at 7°-8° is 108% of the peak height of the diffraction peak at 21°-22°. The XRF analysis results and data such as specific surface area are shown in Table 1.

[0110] Preparation Examples 1-2

[0111] Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water were mixed in a certain proportion and stirred for 30 minutes. Silica sol was then added. The molar ratio of each substance was n(Al₂O₃):(HMCl):n(Na₂O₃). + The mixture of n(H₂O):n(SiO₂) = 0.004:0.03:0.3:21:1 was transferred into a crystallization vessel and crystallized at room temperature with stirring at 350 rpm for 12 h; then at 60 °C for 12 h, and then at 160 °C for 48 h. After crystallization, the mixture was filtered, and the product was dried at 120 °C for 6 h. The product obtained after filtration and drying was seed crystal A2. After calcination at 600 °C for 4 h, the peak height of the 7°-8° diffraction peak was 115% of the peak height of the 21°-22° diffraction peak in the XRD diffraction. The XRF analysis results and specific surface area data are shown in Table 1.

[0112] Preparation Examples 1-3

[0113] Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water were mixed in a certain proportion and stirred for 30 minutes. Silica sol was then added. The molar ratio of each substance was n(Al₂O₃):(HMCl):n(Na₂O₃). +The mixture of n(H₂O):n(SiO₂) = 0.004:0.03:0.3:21:1 was transferred to a crystallization vessel and crystallized at room temperature with stirring at 350 rpm for 12 hours. After crystallization, it was crystallized at 170℃ for 60 hours. The product obtained after filtration and drying was seed crystal A3. XRD analysis of seed crystal A3 after calcination at 600℃ for 4 hours is shown in the figure. Figure 2 The peak height of the diffraction peak at 7°-8° is 63% of that at 21°-22°. The XRF analysis results and data such as specific surface area are shown in Table 1.

[0114] The following preparation examples illustrate the preparation of ZSM-48 molecular sieves.

[0115] Preparation Example 2-1

[0116] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion and stirred for 30 minutes before adding silica sol. The molar ratio of each substance was n(Al2O3):(HMCl):n(Na) + ):n(H2O):n(SiO2)=0.01:0.03:0.3:10:1. The mass percentage of the molecular sieve mother liquor added in step (1) is 30% of the total mass of the molecular sieve mother liquor and water, and 25% of the mass of SiO2 is added as ZSM-48 seed crystal A1;

[0117] (2) Transfer the above mixture into a crystallization kettle, stir at room temperature for 6 hours, crystallize at 80°C for 24 hours, and crystallize at 170°C for 48 hours;

[0118] (3) After crystallization, filter and dry at 120℃ for 6 hours to obtain ZSM-48 molecular sieve powder Z-1. Return the molecular sieve mother liquor to step (1). The water content of Z-1 is 5wt%.

[0119] The XRF analysis results of the silicon-to-aluminum ratio and specific surface area of ​​Z-1 are shown in Table 1. Scanning electron microscope images are shown below. Figure 3 Its morphology is ellipsoidal, with a major axis of 300-700 nm and a major axis to minor axis ratio of approximately 1.1-1.4:1.

[0120] Preparation Example 2-2

[0121] (1) Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor are mixed in a certain proportion and stirred for 30 minutes before adding silica sol. The molar ratio of each substance is n(Al2O3):(HMCl):n(Na) +):n(H2O):n(SiO2)=0.004:0.03:0.3:20:1, the mass percentage of the molecular sieve mother liquor added in step (1) is 20% of the total mass of the molecular sieve mother liquor and water, and 15% of the mass of SiO2 is added as ZSM-48 seed crystal A2;

[0122] (2) The above mixture was transferred into a crystallization vessel and crystallized at 40°C for 12 hours, at 80°C for 10 hours, and at 170°C for 48 hours.

[0123] (3) After crystallization, filter and dry at 120℃ for 6 hours to obtain dried powder of ZSM-48 molecular sieve Z-2. Return the molecular sieve mother liquor to step (1). The water content of Z-2 is 6wt%.

[0124] The XRF analysis results of the silicon-to-aluminum ratio of Z-2 and its specific surface area are shown in Table 1. Its morphology is ellipsoidal, with a major axis of 300-600 nm and a major axis-to-minor axis ratio of approximately 1.1-1.4:1.

[0125] Comparative Preparation Example 1

[0126] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion and stirred for 30 minutes before adding silica sol. The molar ratio of each substance was n(Al2O3):(HMCl):n(Na) + ):n(H2O):n(SiO2)=0.0125:0.03:0.3:30:1. Add 25% of the mass of SiO2 ZSM-48 seed crystal A3. The mass percentage of the molecular sieve mother liquor added in step (1) to the total mass of the molecular sieve mother liquor and water is 20%;

[0127] (2) Transfer the above mixture into a crystallization kettle, stir at room temperature for 6 hours, crystallize at 80°C for 24 hours, and crystallize at 170°C for 48 hours;

[0128] (3) After crystallization, filter and dry at 120℃ for 6 hours to obtain dried powder of ZSM-48 molecular sieve DZ-1. Return the molecular sieve mother liquor to step (1). The water content of DZ-1 was tested to be 8wt%.

[0129] The XRF analysis results and specific surface area data of DZ-1 are shown in Table 1. Its morphology is rod-shaped with a length-to-short diameter ratio of approximately 7:1.

[0130] Table 1

[0131]

[0132]

[0133] The following preparation examples illustrate the preparation of hydroisomerization catalysts.

[0134] Preparation Example 3-1

[0135] 70 g of sample Z-1 from Preparation Example 2-1 was mixed with 40 g of boehmite (dry basis) and 2 g of nitric acid solution, shaped, and calcined at 580°C for 3 h. The carrier strip was then placed in a 0.5 M ammonium chloride solution and exchanged at 90°C for 2 h. The carrier strip was removed, dried, and the sodium oxide content was measured; the results are shown in Table 2.

[0136] Dichlorotetraammineplatinum (containing 57.3% Pt by mass) was poured into 100 g of deionized water and stirred until homogeneous. 100 g of support was added to the above solution and impregnated at room temperature for 4 hours. Subsequently, the catalyst precursor was dried at 120°C for 4 hours. It was then calcined under an air stream at 450°C for 4 hours. The semi-finished catalyst was then reduced again in a hydrogen atmosphere at 400°C for 4 hours to obtain the final catalyst. The resulting hydroisomerization catalyst was named CAT-1. The Pt loading in the catalyst was 0.5 wt%.

[0137] Preparation Example 3-2

[0138] Following the method of Preparation Example 3-1 and using the same catalyst composition, except that Z-1 was replaced with Z-2 from Preparation Example 2-2, after ammonium exchange, the support strip was removed, dried, and the sodium oxide content was measured. The results are shown in Table 2. The obtained hydroisomerization catalyst was named CAT-2.

[0139] Comparative Preparation Example 3-1

[0140] Following the method of Preparation Example 3-1 and using the same catalyst composition, except that Z-1 was replaced with DZ-1 from Comparative Preparation Example 1, the support strip was removed after ammonium exchange, dried, and the sodium oxide content was measured. The results are shown in Table 2. The obtained hydroisomerization catalyst was named DCAT-1.

[0141] Comparative Preparation Example 3-2

[0142] Following the method of Preparation Example 3-1 and using the same catalyst composition, the Z-1 sample from Preparation Example 2-1 was calcined at 580°C for 3 hours. The resulting solid underwent ammonium exchange and was then extruded into strips. The sodium oxide content was measured, and the results are shown in Table 2. The obtained hydroisomerization catalyst was named DCAT-2.

[0143] Table 2

[0144]

[0145] Example 1

[0146] This embodiment uses waste cooking oil A as raw material. The main properties of waste cooking oil A are shown in Table 3.

[0147] The hydrotreating reaction zone is filled with 100 mL of hydrotreating catalyst, supported by alumina. The content of nickel is 4.2 wt% and the content of molybdenum is 26.5 wt%, based on the oxide and the hydrotreating catalyst.

[0148] The selective hydrocracking reaction zone is packed with 100 mL of selective hydrocracking catalyst, supported by amorphous silica-alumina. The active metal components Pt and Pd are 0.15 wt% and 0.30 wt% respectively.

[0149] The hydroisomerization reaction zone is filled with 100 mL of hydroisomerization catalyst CAT-1.

[0150] Waste cooking oil A and hydrogen gas enter the hydrogenation reaction zone together, and sulfiding agent SZ is added to waste cooking oil A. 54 The concentration of the sulfiding agent was 0.3% by weight. Under hydrotreating reaction conditions, it reacted with the sulfidated hydrotreating catalyst to obtain the hydrotreating reaction effluent. The hydrotreating reaction conditions were: reaction pressure 6.4 MPa, reaction temperature 320 °C, and volume hourly space velocity 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 1000. The resulting hydrotreating effluent underwent gas-liquid separation to obtain liquid hydrocarbons, water, and gaseous streams. The conversion rate of catering waste oil A was 100%. The final boiling point of the obtained liquid hydrocarbons was less than 350℃, the liquid hydrocarbon yield was 82.5% by weight, the sulfur content in the obtained liquid hydrocarbons was 2 μg / g, the nitrogen content was 1 μg / g, and the fraction with a boiling point greater than 310℃ accounted for 80% by weight.

[0151] The resulting liquid hydrocarbon enters the selective hydrocracking reaction zone and reacts with a selective hydrocracking catalyst under selective hydrocracking reaction conditions to obtain the selective hydrocracking effluent. The selective hydrocracking reaction conditions are: reaction temperature 355℃, reaction pressure 5.0 MPa, and volume hourly space velocity 1.0 h⁻¹. -1 With a hydrogen-to-oil volume ratio of 500, the fraction at or below 310°C in the liquid phase of the selective hydrocracking effluent accounts for 80% by weight.

[0152] The resulting selective hydrocracking effluent is not separated and directly enters the hydroisomerization reaction zone. Under hydroisomerization reaction conditions, it reacts with a hydroisomerization catalyst to obtain the hydroisomerization effluent. The hydroisomerization reaction conditions are: reaction temperature 280℃, reaction pressure 5.0 MPa, and volume hourly space velocity 1.0 h⁻¹. -1 The volume ratio of hydrogen to oil is 500.

[0153] The effluent from the hydroisomerization reaction is subjected to gas-liquid separation and liquid-phase fractionation to obtain biojet fuel.

[0154] The liquid product yield in the hydroisomerization reaction zone was 96 wt%, and the yield of biojet fuel (distillation range 140-300℃) was 77.6 wt%, with a freezing point of -44℃.

[0155] Example 2

[0156] This embodiment uses waste cooking oil B as raw material. The main properties of waste cooking oil B are shown in Table 3.

[0157] The hydrotreating reaction zone is filled with 100 mL of hydrotreating catalyst, supported by alumina. The content of nickel is 4.0 wt% and the content of tungsten is 28 wt%, based on the oxide and the hydrotreating catalyst.

[0158] The selective hydrocracking reaction zone is packed with 100 mL of selective hydrocracking catalyst, supported by amorphous silica-alumina. The active metal components Pt and Pd are 0.15 wt% and 0.30 wt% respectively.

[0159] The hydroisomerization reaction zone is filled with 100 mL of hydroisomerization catalyst CAT-2.

[0160] Waste cooking oil B and hydrogen gas enter the hydrotreating reaction zone together. Dimethyl disulfide, a sulfiding agent, is added to waste cooking oil B at a concentration of 0.25% by weight. Under hydrotreating reaction conditions, it reacts with the sulfidated hydrotreating catalyst to obtain the hydrotreating reaction effluent. The hydrotreating reaction conditions are: reaction pressure 6.4 MPa, reaction temperature 320℃, and volume hourly space velocity 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 1000. The resulting hydrotreating effluent underwent gas-liquid separation to obtain liquid hydrocarbons, water, and gaseous streams. The conversion rate of waste cooking oil B was 100%. The final boiling point of the obtained liquid hydrocarbons was less than 350℃, the liquid hydrocarbon yield was 82.5% by weight, the sulfur content in the obtained liquid hydrocarbons was 7 μg / g, the nitrogen content was 1 μg / g, and the fraction with a boiling point greater than 310℃ accounted for 85% by weight.

[0161] The resulting liquid hydrocarbon enters the selective hydrocracking reaction zone and reacts with a selective hydrocracking catalyst under selective hydrocracking reaction conditions to obtain the selective hydrocracking effluent. The selective hydrocracking reaction conditions are: reaction temperature 355℃, reaction pressure 5.0 MPa, and volume hourly space velocity 1.0 h⁻¹. -1 With a hydrogen-to-oil volume ratio of 500, the fraction at or below 310°C in the liquid phase of the selective hydrocracking effluent accounts for 75% by weight.

[0162] The resulting selective hydrocracking effluent is directly fed into the hydroisomerization reaction zone without separation. Under hydroisomerization reaction conditions, it reacts with a hydroisomerization catalyst to obtain the hydroisomerization effluent. The hydroisomerization reaction conditions are: reaction temperature 290℃, reaction pressure 5.0 MPa, and volume hourly space velocity 1.0 h⁻¹. -1 The volume ratio of hydrogen to oil is 500.

[0163] The effluent from the hydroisomerization reaction is subjected to gas-liquid separation and liquid-phase fractionation to obtain biojet fuel.

[0164] The yield of liquid products in the hydroisomerization reaction zone was 94 wt%, and the yield of biojet fuel (distillation range 140-300℃) was 74.9 wt%, with a freezing point of <-60℃.

[0165] Comparative Example 1

[0166] This comparative example uses the same raw materials, hydrotreating catalyst, and hydrotreating reaction conditions as Example 1. The resulting hydrotreating reaction effluent is subjected to gas-liquid separation to obtain liquid hydrocarbons, water, and gaseous streams.

[0167] The resulting liquid hydrocarbons do not enter the selective hydrocracking reaction zone but are directly fed into the hydroisomerization reactor, which is loaded with 100 mL of hydroisomerization catalyst CAT-1. The reaction is carried out at a pressure of 6.4 MPa, a temperature of 330 °C, and a volume hourly space velocity of 1.0 h⁻¹. -1 Under a hydrogen-to-oil volume ratio of 500, liquid hydrocarbons undergo hydroisomerization. The hydroisomerization effluent is then separated into gas and liquid phases and distilled to obtain biojet fuel.

[0168] The liquid product yield in the hydroisomerization reaction zone was 97 wt%, the biojet fuel (distillation range 140-300℃) yield was 58 wt%, and the freezing point of the biojet fuel was -49℃.

[0169] Comparative Example 2

[0170] The hydroisomerization reaction zone is filled with 100 mL of hydroisomerization catalyst DCAT-2.

[0171] This comparative example uses the same raw materials, hydrotreating catalyst, hydrotreating reaction conditions, selective hydrocracking catalyst, and selective hydrocracking reaction conditions as Example 1.

[0172] The resulting selective hydrocracking effluent is directly fed into the hydroisomerization reaction zone without separation. Under hydroisomerization reaction conditions, it reacts with a hydroisomerization catalyst to obtain the hydroisomerization effluent. The hydroisomerization reaction conditions are: reaction temperature 290℃, reaction pressure 5.0 MPa, and volume hourly space velocity 1.0 h⁻¹. -1 The volume ratio of hydrogen to oil is 500.

[0173] The effluent from the hydroisomerization reaction is subjected to gas-liquid separation and liquid-phase fractionation to obtain biojet fuel.

[0174] The yield of liquid products in the hydroisomerization reaction zone was 92% by weight, and the yield of biojet fuel (distillation range 140-300℃) was 59% by weight. The freezing point of biojet fuel was -43℃.

[0175] Comparative Example 3

[0176] The hydroisomerization reaction zone is filled with 100 mL of hydroisomerization catalyst DCAT-1.

[0177] This comparative example uses the same raw materials, hydrotreating catalyst, hydrotreating reaction conditions, selective hydrocracking catalyst, and selective hydrocracking reaction conditions as Example 1.

[0178] The resulting selective hydrocracking effluent is directly fed into the hydroisomerization reaction zone without separation. Under hydroisomerization reaction conditions, it reacts with a hydroisomerization catalyst to obtain the hydroisomerization effluent. The hydroisomerization reaction conditions are: reaction temperature 290℃, reaction pressure 5.0 MPa, and volume hourly space velocity 1.0 h⁻¹. -1 The volume ratio of hydrogen to oil is 500.

[0179] The effluent from the hydroisomerization reaction is subjected to gas-liquid separation and liquid-phase fractionation to obtain biojet fuel.

[0180] The liquid product yield in the hydroisomerization reaction zone was 91 wt%, and the yield of biojet fuel (distillation range 140-300℃) was 60 wt%, with a freezing point of -41℃.

[0181] As can be seen from the examples, the method described in this invention, which involves selective hydrocracking followed by hydroisomerization, and the use of a highly active hydroisomerization catalyst in the hydroisomerization reaction zone, effectively improves the yield of biojet fuel.

[0182] Table 3

[0183] project Waste cooking oil A Waste cooking oil B <![CDATA[Density (20 °C), g / cm 3 > 904.8 916 Sulfur content, μg / g 78 55 Nitrogen content, μg / g 81 186 Oxygen content, weight % 12.15 11.2 Total acid value, mgKOH / g 124 32

Claims

1. A method for preparing biojet fuel by hydrogenation, comprising: (1) Oily feedstock and hydrogen are introduced into the hydrotreating reaction zone together. Under the hydrotreating reaction conditions, they react with the hydrotreating catalyst to obtain a hydrotreating reaction effluent. The obtained hydrotreating reaction effluent is separated to obtain liquid hydrocarbon, water and gas streams. The active metal component of the hydrotreating catalyst is at least one metal component selected from Group VIII and / or at least one metal component selected from Group VIB. (2) The liquid hydrocarbon obtained in step (1) enters the selective hydrocracking reaction zone and reacts with the selective hydrocracking catalyst under selective cracking reaction conditions to obtain the selective hydrocracking effluent. (3) The selective hydrocracking reaction effluent obtained in step (2) directly enters the hydroisomerization reaction zone and reacts with the hydroisomerization catalyst to obtain the hydroisomerization reaction effluent. The obtained hydroisomerization reaction effluent is then separated into gas and liquid and fractionated to obtain biojet fuel. The hydroisomerization catalyst comprises a support and an active metal component supported on the support. The support contains ZSM-48 molecular sieve, wherein the molar ratio of silica to alumina in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200 m². 2 / g, the ZSM-48 molecular sieve crystals are ellipsoidal, with a major axis not exceeding 700nm and an aspect ratio of 1-3:1; The active metal component is Pt and / or Pd; In the hydroisomerization catalyst, based on the total amount of the hydroisomerization catalyst, the content of molecular sieve on a dry basis is 20-80% by weight, and the content of the active metal component on an elemental basis is 0.1-20% by weight. Specifically, based on the total amount of the carrier, the content of alkaline metal oxides in the carrier is no higher than 0.001 by weight.

2. The method according to claim 1, characterized in that, The hydrogenation reaction conditions are as follows: reaction temperature 250-450℃, reaction pressure 3.0-10.0 MPa, and volume hourly space velocity 0.1-10.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 300-2000 Nm 3 / m 3 .

3. The method according to claim 1, characterized in that, The hydrogenation reaction conditions are: reaction temperature 300-400℃, reaction pressure 4.0-8.0 MPa, and volume hourly space velocity 0.5-5.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500-1500 Nm. 3 / m 3 .

4. The method according to claim 1, characterized in that, The support for the hydrotreating catalyst is selected from one or more of alumina, silica, titanium dioxide, and zirconium oxide, wherein the Group VIII metal component is cobalt and / or nickel, and the Group VIB metal component is molybdenum and / or tungsten; based on oxides and the hydrotreating catalyst, the content of cobalt and / or nickel is 1-10% by weight, and the content of molybdenum and / or tungsten is 10-45% by weight.

5. The method according to claim 1, characterized in that, In step (1), the effluent from the hydrogenation treatment reaction enters a separator for gas-liquid separation to obtain a liquid stream, water, and a gas stream. The obtained liquid stream then enters a stripping tower for stripping and a dehydration tower for dehydration to remove dissolved hydrogen sulfide, ammonia, and water, thus obtaining liquid hydrocarbons.

6. The method according to claim 1, characterized in that, The selective hydrocracking catalyst comprises a support and an active metal component supported on the support. The support contains one or more of amorphous silica-alumina, SAPO-11, SAPO-31, SAPO-41, ZSM-22, ZSM-23, and ZSM-48 molecular sieves. The active metal component is selected from one or more of Pt, Pd, Rh, Ru, Ag, and Au. Based on the total amount of the selective hydrocracking catalyst, the content of amorphous silica-alumina or molecular sieves on a dry basis is 40-99.9% by weight, and the content of the active metal component is 0.1-0.8% by weight, with the remainder being alumina.

7. The method according to claim 1, characterized in that, The selective hydrocracking reaction conditions are as follows: reaction temperature 250-500℃, reaction pressure 1.0-15.0 MPa, and volume hourly space velocity 0.1-10.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200-1500 Nm 3 / m 3 .

8. The method according to claim 1, characterized in that, The selective hydrocracking reaction conditions are: reaction temperature 300-400℃, reaction pressure 2.0-8.0 MPa, and volume hourly space velocity 0.5-5.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 300-1000 Nm 3 / m 3 .

9. The method according to claim 1, characterized in that, In the liquid phase product of the obtained selective hydrocracking reaction effluent, the mass percentage of the fraction with a temperature >310℃ is not greater than 50%.

10. The method according to claim 1, characterized in that, In the liquid phase products of the obtained selective hydrocracking reaction effluent, the mass percentage of the fraction with a temperature >310℃ is no more than 30%.

11. The method according to claim 1, characterized in that, In the hydroisomerization catalyst, based on the total amount of the hydroisomerization catalyst, the content of molecular sieve on a dry basis is 30-70% by weight, and the content of the active metal component on an elemental basis is 0.2-10% by weight.

12. The method according to claim 1 or 11, characterized in that, The hydroisomerization catalyst also contains a binder, which is alumina and / or silicon oxide; Based on the total amount of hydroisomerization catalyst, the binder content is 20-80% by weight.

13. The method according to claim 1, characterized in that, The ZSM-48 molecular sieve has an aspect ratio of 1-2:1; the ZSM-48 molecular sieve has a grain size of 300-700 nm; and the ZSM-48 molecular sieve has a specific surface area of ​​200-280 m². 2 / g; The pore volume of ZSM-48 molecular sieve is 0.2-0.3 mL / g.

14. The method according to claim 1, characterized in that, The preparation method of the hydroisomerization catalyst includes the following steps: Step 1: Shape the dried powder of ZSM-48 molecular sieve into a molded carrier; The molar ratio of silica to alumina in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200 m². 2 / g, the ZSM-48 molecular sieve crystals are ellipsoidal, with a major axis not exceeding 700nm and an aspect ratio of 1-3:1; Based on the mass of the dried ZSM-48 molecular sieve powder, the moisture content of the dried ZSM-48 molecular sieve powder is less than 15% by weight. Step 2: Perform ammonium exchange on the molded carrier; Step 3: Introduce an active metal component onto the product obtained in Step 2 to obtain a hydroisomerization catalyst; The active metal component is Pt and / or Pd.

15. The method according to claim 14, characterized in that, The molding process described in step one includes: mixing the dried powder of ZSM-48 molecular sieve, binder and additives, and then molding and calcining. The additive is an inorganic acid; The binder is selected from at least one of alumina, silica, boehmite, and silica sol.

16. The method according to claim 15, characterized in that, The auxiliary agent is nitric acid and / or hydrochloric acid; The binder is boehmite.

17. The method according to claim 15, characterized in that, The amount of the binder is 20-60 parts by weight relative to 100 parts by weight of dried ZSM-48 molecular sieve powder, and the amount of the additive is 2-20 parts by weight. The calcination conditions include: a calcination temperature of 300-600℃ and a calcination time of 2-10h.

18. The method according to claim 14, characterized in that, The ammonium exchange in step two includes: contacting the molded carrier with an aqueous solution of ammonium salt; The conditions for ammonium exchange include: a temperature of 70-120℃ and a time of 1-8 hours; The concentration of ammonium salt in the aqueous solution is 0.01-1 mol / L; The ammonium salt is selected from at least one of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium acetate.

19. The method according to claim 14, characterized in that, The method for introducing the active metal component in step three includes: impregnating the product from step two with a solution of a soluble compound containing the active metal component, followed by drying and calcination to obtain the hydroisomerization catalyst. The soluble compound containing the active metal component is selected from at least one of tetraamminepalladium nitrate, tetraamminepalladium acetate, dichlorotetraamminepalladium, tetraammineplatinum nitrate, tetraammineplatinum acetate, and dichlorotetraammineplatinum. The drying temperature is 80-120℃, and the drying time is 2-6 hours; The roasting temperature is 400-500℃, and the roasting time is 2-6 hours.

20. The method according to claim 1, characterized in that, The hydroisomerization reaction conditions are as follows: reaction temperature 200-500℃, reaction pressure 1.0-15.0 MPa, and volume hourly space velocity 0.1-10.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200–1500 Nm 3 / m 3 .

21. The method according to claim 1, characterized in that, The hydroisomerization reaction conditions are as follows: reaction temperature 280-380℃, reaction pressure 2.0-8.0 MPa, and volume hourly space velocity 0.5-5.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 300-1000 Nm 3 / m 3 .

22. The method according to claim 1, characterized in that, The oily raw materials mentioned are animal and vegetable oils and / or waste cooking oil.

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