A method of preparing a jet fuel

Abstract

The application discloses a method for preparing jet fuel by mixing a direct coal liquefaction crude oil fraction with an indirect coal liquefaction crude oil fraction, hydrogenating and refining the mixture, and separating the mixture to obtain the jet fuel. The preparation method is simple, and the prepared jet fuel has good indexes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aviation fuel, and relates to a method for preparing jet fuel, in particular, a method for preparing jet fuel by hydrogenation refining of a light oil fraction of coal direct liquefaction crude oil and a light oil fraction of coal indirect liquefaction crude oil as raw materials. BACKGROUND

[0002] China is rich in coal and short of oil, and coal accounts for 94% of fossil energy. In a long period of time, coal will still be the main energy source in China, so how to use coal more efficiently and cleanly and ensure national energy security and national defense security is a major problem to be solved. According to the coal type and resource characteristics in China, coal direct liquefaction and indirect liquefaction are two main development approaches for coal-to-liquids. Developing coal-to-liquids complete technology meets the major needs of China's economic development, and has great strategic significance for improving the national energy security guarantee capacity, promoting the transformation of the modern coal industry, and helping the upgrading of military special fuels and aerospace fuels.

[0003] Coal direct liquefaction process is a coal utilization approach in which coal macromolecules are pyrolyzed and liquefied to produce small molecule oil products under the action of a solvent and a catalyst under high temperature, high pressure and hydrogen conditions. In the direct liquefaction reactor, coal macromolecule cracking and free radical hydrogenation mainly occur, and the obtained primary liquefied product is mainly composed of aromatic hydrocarbons and naphthenes. Subsequently, the liquefied oil product enters a hydrogenation stabilization unit, and the heavy product part is used as a solvent oil to recycle coal slurry, and the light part enters a hydro-upgrading unit to obtain a product which basically retains the molecular structure characteristics of coal, and the produced fuel oil component has low sulfur and nitrogen content, high naphthene content, high specific gravity, and low condensation point.

[0004] The coal indirect liquefaction process uses coal as raw material to first produce synthesis gas (CO and H2) through gasification, and then produces light oil, heavy oil and heavy wax crude products through Fischer-Tropsch synthesis reaction under the action of a catalyst. After stripping to separate liquefied petroleum gas, the crude products enter a refining reactor for hydrogenation refining. The refined products are fractionated into diesel, crude naphtha and heavy products. The crude naphtha is separated into liquefied petroleum gas and naphtha through adsorption and desorption and stabilization distillation. The heavy products enter a vacuum tower for further separation, and the tower bottom product is hydrogenated to be fractionated into naphtha and fuel oil components.

[0005] The aromatic hydrocarbon content and sulfur and nitrogen content of the primary liquefied oil from the coal direct liquefaction unit are high, and if the primary liquefied oil is directly used to prepare jet fuel, the requirements for the hydrogenation catalyst and the corresponding process conditions are high, the process is long, and the conditions are harsh. Moreover, the produced jet fuel has low heat value and smoke point, which cannot meet the requirements of jet fuel.

[0006] The coal indirect liquefaction product has high carbon number, in order to process the target product, needs to pass through the process units of hydrofining, cracking and isomerization and the like, the processing flow is longer. And the produced jet fuel has low density and the freezing point is not up to standard, which cannot meet the requirement of jet fuel.

[0007] The invention patent CN200510083900.8 discloses a method for producing aviation kerosene from coal liquefaction oil. The method uses coal liquefaction crude oil as raw material to produce aviation kerosene with high specific gravity, has high yield and high kerosene specific gravity. However, the method causes the solvent part in the coal liquefaction crude oil to also produce kerosene, so that the solvent cannot be recycled, which will affect the coal liquefaction reaction.

[0008] The invention patent CN201911428632.2 discloses a method for producing aviation kerosene from coal liquefaction oil. The method prepares qualified jet fuel by subjecting the coal direct liquefaction crude oil to hydrofining and hydro-upgrading. However, the method is relatively complex and needs two times of hydrogenation. And the obtained jet fuel has low smoke point. SUMMARY

[0009] In order to make up for the deficiency of the prior art, the present application provides a method for preparing jet fuel, which mixes the coal direct liquefaction crude oil fraction and the coal indirect liquefaction crude oil fraction, then carries out hydrofining and separation to obtain jet fuel. The preparation method is simple, and the prepared jet fuel has good indicators.

[0010] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0011] A method for preparing jet fuel, the method comprises the following steps:

[0012] (1) subjecting the oil coal slurry prepared by coal and solvent oil to coal direct liquefaction reaction with hydrogen, and obtaining first light fraction oil and heavy fraction oil after the generated coal direct liquefaction crude oil is separated in a first fractionating column; the first light fraction oil enters an oil product mixer;

[0013] (2) subjecting the coal gasification synthesis gas to Fischer-Tropsch synthesis reaction, and obtaining second light fraction oil and wax after the synthesized coal indirect liquefaction crude oil is separated in a second fractionating column; the second light fraction oil enters the oil product mixer;

[0014] (3) mixing the first light fraction oil separated from the coal direct liquefaction crude oil and the second light fraction oil separated from the coal indirect liquefaction crude oil in the oil product mixer to obtain mixed oil, and then carrying out hydrofining reaction in a hydrofining reactor;

[0015] (4) obtaining naphtha, jet fuel and heavy bottom oil after the hydrofining product obtained in step (3) is fractionated;

[0016] (5) The heavy oil obtained in step (4) is recycled to the hydrofining reactor and mixed with the mixed oil to perform hydrofining reaction.

[0017] In step (1) of the present application, the coal direct liquefaction crude oil is a liquefaction crude oil obtained by coal direct liquefaction process, such as the product oil leaving the coal direct liquefaction reactor after removal of oil gas and solid residue, i.e. without further hydroprocessing, and its distillation range is usually in the range of 30-500°C.

[0018] According to the method of the present application, preferably in step (1), the first fractionating column is fractionated at a temperature of 290-300°C, such as 295°C, and the fraction below this temperature is taken as the first light fraction oil and the fraction above this temperature is taken as the heavy fraction oil.

[0019] In some embodiments, in step (1), the heavy fraction oil can be subjected to hydrostabilization treatment to obtain solvent oil for recycling; hydrostabilization of coal direct liquefaction oil is well known in the art, such as hydrostabilization treatment in a hydrostabilization reactor, and the reaction conditions can be: reaction temperature 300-400°C, reaction pressure 12.0-20.0 MPa, volume space velocity 0.5-3.0 h -1 , hydrogen to oil ratio 500-1500 V / V; the support of the loaded hydrogen catalyst can use amorphous alumina or aluminum silicate, and the active metal loaded on the catalyst support is VIB and VIII group; wherein the content of VIB non-noble metal component loaded on the catalyst support is 5-30%, and the content of VIII non-noble metal component is 1-10%. The VIB group metal is selected from Mo or / and W, and the VIII group metal is selected from Co or / and Ni. It is understood in the art that the hydrostabilization reactor is a fixed bed hydrogenation reactor or an expanded bed reactor, or a boiling bed reactor with forced internal circulation.

[0020] In step (2) of the present application, the coal indirect liquefaction crude oil is a synthesis crude oil obtained by low-temperature Fischer-Tropsch synthesis process (i.e. slurry bed Fischer-Tropsch synthesis process), such as the product oil leaving the Fischer-Tropsch reactor after removal of oil gas and wax residue, i.e. without further hydroprocessing, and its distillation range is usually in the range of 30-500°C.

[0021] According to the method of the present application, preferably in step (2), the second fractionating column is fractionated at a temperature of 310-330°C, such as 320°C, and the fraction below this temperature is taken as the second light fraction oil into the oil product mixer.

[0022] In step (3) of the present application, the direct coal liquefaction crude oil fraction (i.e. the first light oil fraction) and the indirect coal liquefaction crude oil fraction (i.e. the second light oil fraction) are mixed uniformly in an oil mixer, preferably, the mixing mass ratio of the first light oil fraction to the second light oil fraction is 7:3-3:7, preferably 6:4-4:6, such as 5:5, to ensure the quality of the jet fuel.

[0023] In step (3) of the present application, the oil fed into the hydrofining reactor is subjected to hydrofining treatment, which is well known in the art; in some embodiments, the reaction temperature of the hydrofining reactor is 280-400°C, preferably 300-380°C, such as 320, 340, 350 or 370°C, the reaction pressure is 8.0-20.0 MPa, preferably 12-18 MPa, such as 15 or 17 MPa; the volume space velocity is 0.4-4.0 h -1 , preferably 0.5-2.0 h -1 , such as 1 or 1.5 h -1 ; the hydrogen to oil ratio is 400-1500 V / V, preferably 500-1000 V / V, such as 800 V / V.

[0024] In some embodiments, in step (3), the support of the hydrofining catalyst loaded in the hydrofining reactor is amorphous alumina or aluminum silicate, and the active metal loaded on the catalyst support is VIB and VIII group; wherein the content of the VIB non-noble metal component loaded on the catalyst support is 0.5-30%, and the content of the VIII non-noble metal component is 1-20%; the VIB group metal is selected from Mo or / and W, and the VIII group metal is selected from Co or / and Ni; specifically, the hydrofining catalyst can also be one or more of the commercial RNC-2 catalyst (Research Institute of Petroleum Processing) or FFT-1 catalyst (Fushun Research Institute of Petroleum and Petrochemicals).

[0025] In a preferred embodiment, the support of the hydrofining catalyst is alumina, and the active metal oxides loaded thereon are MoO3, WO3 and NiO, wherein the content of the active metal oxide component in the total amount of the hydrofining catalyst is 8%-25%, such as 9%, 12%, 15%, 18% or 20%, wherein the content of MoO3 is 8-20%, such as 10%, 15% or 18%, the content of NiO is 1-6%, such as 1%, 3% or 5%, and the content of WO3 is 0-10%; it is understood in the art that when the content is 0, it means that the component is not contained. The preparation of the supported hydrofining catalyst is well known in the art, for example, in the present application, taking alumina support as an example, the supported catalyst is prepared by impregnation method, which can be specifically referred to CN85104438A.

[0026] Preferably, in step (3), the hydrofining reactor is a fixed bed reactor.

[0027] According to the method of the present application, preferably, in step (4), the cut temperature of naphtha and jet fuel is 130-150℃, such as 140℃, i.e. below this cut temperature is naphtha; the cut temperature of jet fuel and heavy bottom oil is 280-300℃, such as 290℃, i.e. above this cut temperature is heavy bottom oil.

[0028] In step (5) of the present application, the heavy bottom oil obtained in step (4) is recycled to the hydrofining reactor, and after being mixed with the mixed oil, they are subjected to hydrofining reaction together, so as to better meet the product index while improving the yield of jet fuel.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] 1. The coal direct liquefaction crude oil fraction is characterized by high content of sulfur and nitrogen, high content of cyclic hydrocarbons and aromatic hydrocarbons and low content of chain hydrocarbons, but high density. The coal indirect liquefaction crude oil fraction has low density, high content of chain hydrocarbons, and almost no sulfur, nitrogen and aromatic hydrocarbons, but high oxygen content and part of olefins. Mixing the coal direct liquefaction crude oil and the coal indirect liquefaction crude oil balances the hydrocarbon group composition of the raw material, dilutes the content of heteroatoms, and has moderate density, so as to realize the complementary advantages of the two kinds of raw materials and reduce the difficulty of subsequent processing.

[0031] 2. In the original coal direct liquefaction process, the coal direct liquefaction crude oil is subjected to hydrogenation stabilization and then cut, the heavy components are recycled to the coal direct liquefaction unit as solvent oil, and the light components enter the hydro-upgrading unit for hydrofining treatment. Therefore, the role of the hydrogenation stabilization unit is ① to provide qualified solvent oil for the coal direct liquefaction unit; and ② to provide stable raw material for the downstream hydro-upgrading device. In the hydrogenation stabilization reaction process, mainly aromatic hydrocarbons are partially saturated and heteroatoms are removed. If the hydrogenation is too saturated, the content of saturated hydrocarbons in the circulating solvent will excessively increase, which greatly reduces the swelling ability of the solvent for coal according to the principle of similar compatibility; if the hydrogenation is insufficient, the produced hydro-upgrading raw material has high content of heteroatoms, and the upgrading catalyst is easy to be poisoned. Therefore, in the present application, the coal direct liquefaction crude oil is directly cut, the light components are directly mixed with the coal indirect liquefaction fraction oil and then subjected to hydrogenation, and the heavy components are separately subjected to solvent hydrogenation stabilization, so as to ensure moderate hydrogenation of the solvent, further improve the coal dissolution ability and hydrogen supply ability of the solvent, and thus improve the coal direct liquefaction efficiency.

[0032] 3. The combined processing of the coal direct liquefaction crude oil fraction and the coal indirect liquefaction crude oil fraction only needs hydrofining, so as to produce qualified jet fuel, greatly shorten the process flow, and slow down the process conditions. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A schematic diagram of one embodiment of a process for the production of jet fuel. DETAILED DESCRIPTION

[0034] For the purpose of understanding the present application, the present application will be further described in connection with the following examples. It should be understood that the following examples are only for the purpose of better understanding the present application, and are not meant to limit the present application to the following examples.

[0035] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are provided as approximate descriptions of the ranges and are accomplished by the values reasonably related to the stated endpoints. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum of 1 and a maximum of 10. Any maximum numerical limitation

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The terms "first," "second," "third," etc. are used herein for descriptive purposes only and do not connote or imply a relative importance.

[0037] The experimental steps or conditions not specified in the examples can be carried out according to the conventional experimental steps or conditions in the corresponding technical field. The reagents or instruments not specified by the manufacturer are conventional products that can be obtained by purchase.

[0038] As shown in the following scheme, the preparation of jet fuel of the present application comprises the following steps: Figure 1 (1) The oil coal slurry prepared by coal and solvent oil is passed through a coal direct liquefaction reactor 11 to generate coal direct liquefaction crude oil, which is passed through a first fractionating column 12 for coal direct liquefaction crude oil separation. The heavy fraction oil obtained is used as a solvent oil raw material and passed through a solvent oil hydrogenation stabilizing device 13 for hydrogenation stabilization treatment to generate qualified solvent oil, which is recycled to the oil coal slurry preparation part. The first light fraction oil obtained is passed through an oil product mixer 3.

[0039] (2) The coal gasification synthesis gas is passed through a Fischer-Tropsch synthesis reactor 21 to synthesize coal indirect liquefaction crude oil, which is passed through a second fractionating column 22 for coal indirect liquefaction crude oil separation. The second light fraction oil obtained is passed through an oil product mixer 3.

[0040] (3) The mixed oil uniformly obtained in the oil product mixer 3 is passed through a hydrofining reactor 4 for hydrofining treatment.

[0041]

[0042] ​(4) The hydrorefined product obtained in (3) is separated to obtain naphtha, jet fuel and heavy oil at the bottom of the column; specifically, the hydrorefined product is separated by a hot high-pressure separator 5 to obtain hot high-pressure gas at the top and hot high-pressure oil at the bottom; the hot high-pressure gas at the top is injected into deionized water (to prevent ammonium salt from plugging the pipeline) and then enters a cold high-pressure separator 6 to separate cold high-pressure oil and cold high-pressure gas, the cold high-pressure gas can be vented after metering, and the water separated by the cold high-pressure separator 6 can be discharged into a wastewater tank; the hot high-pressure oil at the bottom of the hot high-pressure separator 5 enters a hot low-pressure separator 7 to separate hot low-pressure gas at the top and hot low-pressure oil at the bottom; the hot low-pressure gas at the top enters a cold low-pressure separator 8 to separate cold low-pressure gas at the top and cold low-pressure oil at the bottom, and the cold low-pressure gas can be vented after metering; the oils separated from the cold high-pressure separator 6, the hot high-pressure separator 7 and the hot low-pressure separator 8 are mixed into a third separation column 9 for cutting separation, and naphtha, jet fuel and heavy oil at the bottom of the column are obtained after separation.

[0043] (5) The heavy oil at the bottom of the column is recycled to the hydrorefining reactor 4 and mixed with the mixed oil to perform hydrorefining reaction.

[0044] The hydrogenation part in the above process is composed of a hydrostabilization reactor and a hydrorefining reactor. The purpose of the hydrostabilization section is to process the solvent to improve the hydrogen supply performance of the solvent and ensure the dissolution capacity of the solvent for coal. The purpose of the hydrorefining section is to remove sulfur, nitrogen, oxygen and other heteroatoms and saturate aromatic hydrocarbons in the coal liquefied oil crude oil to generate qualified fuel.

[0045] The beneficial effects of the present application will be further illustrated below with specific examples.

[0046] Examples 1-8

[0047] (1) The oil coal slurry prepared from coal and solvent oil is subjected to direct coal liquefaction reaction with hydrogen, and the obtained direct coal liquefaction crude oil is separated by a first fractionating column to obtain first light fraction oil and heavy fraction oil; the first light fraction oil enters an oil product mixer;

[0048] (2) The coal gasification synthesis gas is subjected to Fischer-Tropsch synthesis reaction, and the obtained indirect coal liquefaction crude oil is separated by a second fractionating column to obtain second light fraction oil and wax, and the second light fraction oil enters the oil product mixer;

[0049] (3) The first light fraction oil separated from the direct coal liquefaction crude oil is mixed with the second light fraction oil separated from the indirect coal liquefaction crude oil in the oil product mixer to obtain mixed oil, and then the mixed oil is subjected to hydrorefining reaction in a hydrorefining reactor;

[0050] (4) The hydrorefined product obtained in step (3) is separated by fractionation to obtain naphtha, jet fuel and heavy oil at the bottom of the column;

[0051] (5) The heavy bottom oil obtained in step (4) is recycled to the hydrofining reactor and mixed with the mixed oil to perform hydrofining reaction.

[0052] Comparative Example 1

[0053] The first light fraction oil is subjected to hydrofining reaction in a hydrofining reactor; the obtained hydrofining product is then subjected to fractionation to obtain naphtha, jet fuel and heavy bottom oil; and the obtained heavy bottom oil is recycled to the hydrofining reactor and mixed with the first light fraction oil to perform hydrofining reaction. The specific process conditions are the same as those in Example 7.

[0054] Comparative Example 2

[0055] The second light fraction oil is subjected to hydrofining reaction in a hydrofining reactor; the obtained hydrofining product is then subjected to fractionation to obtain naphtha, jet fuel and heavy bottom oil; and the obtained heavy bottom oil is recycled to the hydrofining reactor and mixed with the second light fraction oil to perform hydrofining reaction. The specific process conditions are the same as those in Example 8.

[0056] Comparative Example 3

[0057] Coal direct liquefaction diesel oil prepared in the process of the 1 million ton coal direct liquefaction industrial demonstration device of the National Energy Group (Ordos).

[0058] Comparative Example 4

[0059] Coal indirect liquefaction diesel oil prepared in the process of the 400 million tons / year coal indirect liquefaction device of the National Energy Group Ningxia Coal Industry.

[0060] The properties of the raw oil in the above comparative examples and examples are shown in Table 1, the process conditions are shown in Table 2, and the properties of the obtained jet fuel product or diesel product are shown in Table 3.

[0061] Table 1 Properties of raw oil in comparative examples and examples

[0062]

[0063] Table 2 Process conditions of examples and comparative examples

[0064]

[0065] Note: "0" in the table indicates the absence of the component; the catalyst carrier is alumina.

[0066] Table 3 Properties of jet fuel product and diesel product

[0067]

[0068]

[0069] As shown in Table 3, the combined processing flow of the coal direct liquefaction crude distillate oil and the coal indirect liquefaction crude distillate oil is simple, and the process conditions are mild. The density, freezing point, smoke point, aromatic hydrocarbon content and distillation range of the product jet fuel all meet the requirements of the No. 3 jet fuel GB6537-2018 national standard.

[0070] Therefore, on the basis of the successful engineering implementation of the existing coal direct liquefaction and indirect liquefaction, the oil upgrading process unit between the two is optimized and coupled, so that not only the product structure can be optimized, but also the process complexity can be reduced, the overall economic benefit of the coal liquefaction technology is improved, and thus beneficial exploration for the large-scale industrial implementation of the coal liquefaction technology is provided.

[0071] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing jet fuel, the method comprising the following steps: (1) subjecting coal to direct coal liquefaction with solvent oil to produce coal direct liquefaction crude oil, and separating the coal direct liquefaction crude oil in a first fraction column to obtain a first light fraction oil and a heavy fraction oil, and feeding the first light fraction oil into an oil product mixer; (2) subjecting coal gasification synthesis gas to Fischer-Tropsch synthesis to produce coal indirect liquefaction crude oil, and separating the coal indirect liquefaction crude oil in a second fraction column to obtain a second light fraction oil and wax, and feeding the second light fraction oil into the oil product mixer; (3) mixing the first light fraction oil from the coal direct liquefaction crude oil and the second light fraction oil from the coal indirect liquefaction crude oil in the oil product mixer to obtain a mixed oil, and subjecting the mixed oil to hydrofining in a hydrofining reactor; wherein the mass ratio of the first light fraction oil to the second light fraction oil is 7:3 to 3:7; (4) subjecting the hydrofining product obtained in step (3) to fractionation to obtain naphtha, jet fuel and heavy bottom oil; (5) recycling the heavy bottom oil obtained in step (4) to the hydrofining reactor, and mixing the heavy bottom oil with the mixed oil to perform hydrofining.

2. The method of claim 1, wherein, In step (1), the first fraction column is fractionated at a temperature of 290-300°C, and the fraction below the fractionation temperature is used as the first light fraction oil, and the fraction above the fractionation temperature is used as the heavy fraction oil.

3. The method of claim 1, wherein, In step (2), the second fraction column is fractionated at a temperature of 310-330°C, and the fraction below the fractionation temperature is used as the second light fraction oil and fed into the oil product mixer.

4. The method according to any one of claims 1-3, characterized in that, In step (3), the hydrofining is performed at a temperature of 280-400°C, a pressure of 8.0-20.0 MPa, a volume space velocity of 0.4-4.0 h-1 and a hydrogen to oil ratio of 400-1500 V / V.

5. The method of claim 4, wherein, In step (3), the hydrofining is performed at a temperature of 300-380°C, a pressure of 12-18 MPa, a volume space velocity of 0.5-2.0 h-1 and a hydrogen to oil ratio of 500-1000 V / V.

6. The method of claim 4, wherein, In step (3), the hydrofining catalyst carrier used in the hydrofining reactor is amorphous alumina or aluminum silicate, and the active metal loaded on the catalyst carrier is VIB and VIII group; wherein the content of the VIB non-noble metal component loaded on the catalyst carrier is 0.5-30%, and the content of the VIII non-noble metal component is 1-10%; the VIB group metal is selected from Mo and / or W, and the VIII group metal is selected from Co and / or Ni.

7. The method of claim 6, wherein, In step (3), the hydrofining reactor is a fixed bed reactor.

8. The method according to any one of claims 1-3 and 5-7, characterized in that, In step (4), the cutting temperature of naphtha and jet fuel is 130-150°C, and the cutting temperature of jet fuel and heavy bottom oil is 280-300°C.

9. The method according to any one of claims 1-3 and 5-7, characterized in that, The coal direct liquefaction crude oil is obtained by a direct coal liquefaction process, and has a distillation range of 30-500°C; the coal indirect liquefaction crude oil is obtained by a low-temperature Fischer-Tropsch synthesis process, and has a distillation range of 30-500°C.

10. The method according to any one of claims 1-3 and 5-7, characterized in that, In step (1), the heavy fraction oil is subjected to hydrostabilization treatment to obtain solvent oil.

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