Composite catalyst, preparation method thereof and preparation method of biological aviation kerosene

Abstract

The invention belongs to the technical field of preparation of biological aviation kerosene, and particularly relates to a composite catalyst, a preparation method thereof and a preparation method of the biological aviation kerosene. The isomerization catalyst and the cracking catalyst are combined, the active site of the composite catalyst is optimized, the yield of the biological aviation kerosene and the proportion of isomerization products are increased, the catalyst cost is low, and the technological process is flexible and controllable.

Description

Technical Field

[0001] The present invention belongs to the technical field of bio-jet fuel preparation, and in particular relates to a composite catalyst and a preparation method thereof, and a preparation method of bio-jet fuel. Background Art

[0002] Conventional hydrocarbon-based biodiesel has a high pour point, generally between 15 and 20°C. Some people use precious metal catalysts to isomerize and depress the pour point to improve its cold flow properties, and convert high-pour point hydrocarbon-based biodiesel into biojet fuel and low-pour point biodiesel.

[0003] Chinese patent CN114540077A discloses a method for preparing bio-jet fuel, which uses biomass deoxygenated oil obtained by hydrodeoxygenation of biomass oil as raw material, and undergoes a hydrocracking isomerization reaction with hydrogen under the action of a precious metal catalyst to obtain bio-jet fuel.

[0004] U.S. Patent No. 8,039,682B2 discloses a method for preparing aviation kerosene, which uses a precious metal catalyst to prepare naphtha, aviation kerosene and heavy diesel from bio-based oils such as vegetable oils through steps such as hydrodeoxygenation and isomerization.

[0005] U.S. Patent No. 12129438B2 discloses a catalyst Pt / SAPO-11, which uses precious metals as active ingredients to hydrogenate and isomerize treated bio-based oil to produce bio-jet fuel.

[0006] The aforementioned patents all utilize precious metal catalysts, which have high catalytic activity. However, they can over-crack during hydrocracking, resulting in products with a high concentration of small molecules that are easily vaporized. While isomerization improves the low-temperature performance of bio-jet fuel, excessive isomerization reduces the proportion of linear alkanes and the bio-jet fuel yield, typically peaking at around 69% or even lower. There are no reports of further improvements in bio-jet fuel yield. Summary of the Invention

[0007] The present invention aims to provide a composite catalyst and a preparation method thereof, and a preparation method for bio-jet fuel. The bio-jet fuel yield of the composite catalyst of the present invention is above 75%.

[0008] For the above purpose, the technical solution of the present invention is:

[0009] The present invention provides a composite catalyst, comprising an isomerization catalyst and a cracking catalyst; the isomerization catalyst comprises, by weight, 5 to 20 parts of a first active component, 0.5 to 3 parts of a catalytic promoter, 5 to 20 parts of a first extrusion aid, 10 to 40 parts of a first binder, 1 to 10 parts of a first peptizing agent, and 30 to 60 parts of a first carrier; the first active component comprises at least one of nickel, molybdenum, cobalt, iron, and tungsten; the catalytic promoter comprises at least one of silver, lanthanum, and copper; the first carrier comprises at least one of ZSM-23 molecular sieve, ZSM-22 molecular sieve, ZSM-48 molecular sieve, SAPO-11 molecular sieve, and SAPO-34 molecular sieve; the cracking catalyst comprises, by weight, 5 to 20 parts of a second active component, 5 to 20 parts of a second extrusion aid, 10 to 40 parts of a second binder, 1 to 10 parts of a second peptizing agent, and 30 to 60 parts of a second carrier; the second active component comprises at least one of nickel, molybdenum, cobalt, and tungsten; and the second carrier comprises at least one of ZSM-5 molecular sieve and β molecular sieve.

[0010] The present invention provides a method for preparing the composite catalyst described in the above scheme, comprising the following steps: mixing a catalytic promoter precursor, a first extrusion aid, a first binder, a first peptizing agent and a first carrier, and then sequentially performing a first drying, a first calcination, loading a first active component precursor and a second calcination to obtain an isomerized catalyst precursor; mixing a second extrusion aid, a second binder, a second peptizing agent and a second carrier, and then sequentially performing a second drying, a third calcination, loading a second active component precursor and a fourth calcination to obtain a cracking catalyst precursor; and reducing the isomerized catalyst precursor and the cracking catalyst precursor to obtain the composite catalyst comprising the isomerized catalyst and the cracking catalyst.

[0011] The present invention provides a method for preparing bio-jet fuel, comprising the following steps: mixing high-condensation-point hydrocarbon-based biodiesel with hydrogen, performing hydrogenation isomerization reaction and cracking reaction under the action of a composite catalyst, and then fractionating, wherein the fractionation temperature is less than 140°C, 140-280°C, and greater than 280°C, naphtha is obtained at a temperature less than 140°C, the bio-jet fuel is obtained at a temperature between 140 and 280°C, and low-condensation diesel is obtained at a temperature greater than 280°C; the composite catalyst is the composite catalyst described in the above scheme or the composite catalyst obtained by the preparation method described in the above scheme; the stacking mode of the isomerization catalyst and the cracking catalyst in the composite catalyst is cross-stacked; the number of layers of the isomerization catalyst is 1-3; the ratio of the total bed thickness of the isomerization catalyst to the reactor diameter is (5-10):1; the number of layers of the cracking catalyst is 1-3; and the ratio of the total bed thickness of the cracking catalyst to the reactor diameter is (1-5):1.

[0012] The present invention provides a composite catalyst. This invention combines an isomerization catalyst with a cracking catalyst to optimize the active sites of the composite catalyst, enhance catalytic activity and selectivity, and increase the yield of bio-jet fuel and the proportion of isomerized products, with a yield exceeding 75%. The catalyst cost is low, and the process is flexible and controllable. Specifically:

[0013] The present invention utilizes a catalytic promoter to anchor the first active component to form an alloy, thereby increasing the dispersion and steric hindrance of the first active component and preventing the first active component from sintering and agglomerating. The catalytic promoter can also regulate the electron cloud density of the first active component, induce changes in the electronic structure of the first active component, promote hydrogen heteroscission, serve as a hydrogen overflow channel, and increase the hydrogenation and isomerization rates. The catalytic promoter can also improve the catalytic activity of the first active component, reduce the amount of the first active component used, and reduce costs.

[0014] The heterogeneous catalyst carrier of the present invention has a unique pore structure, and the high-condensation-point hydrocarbon-based biodiesel has a large diffusion resistance, and is preferentially adsorbed on the metal sites of the molecular sieve pores for dehydrogenation to obtain olefins. The acidic sites protonate and β-break olefins to produce smaller linear alkanes and isoalkenes. The isoalkenes are then hydrogenated again at the metal sites to produce isoalkanes. The unique pore structure of the isoalkenes catalyst support inhibits the formation of multi-branched isomers and prioritizes the formation of end-isomers.

[0015] After desorption from the isomerization catalyst, the end isomers enter the pores of the shape-selective cracking catalyst molecular sieve. Due to their spatial structure, the end isomers contain weak electron groups, which reduce the stability of the C-C bond. The end branched chains diffuse through the molecular sieve pores to the surface of the second active component, where they are dehydrogenated to form olefins. These olefins also undergo protonation (to form carbon cations) and β-scission to produce bio-jet fuel. The cracking catalyst carrier of the present invention is a molecular sieve with a high silicon-aluminum ratio (i.e., SiO2:Al2O3 molar ratio). Its surface acidity is weak, and the resulting carbon cations are more stable, effectively reducing secondary cracking after the cracking reaction and improving the selectivity of bio-jet fuel. DETAILED DESCRIPTION

[0016] The present invention provides a composite catalyst comprising an isomerization catalyst and a cracking catalyst;

[0017] The isomerization catalyst comprises, by weight, 5 to 20 parts of a first active component, 0.5 to 3 parts of a catalytic promoter, 5 to 20 parts of a first extrusion aid, 10 to 40 parts of a first binder, 1 to 10 parts of a first peptizing agent, and 30 to 60 parts of a first carrier; the first active component comprises at least one of nickel, molybdenum, cobalt, iron, and tungsten; and the catalytic promoter comprises at least one of silver, lanthanum, and copper.

[0018] Calculated by mass, the cracking catalyst includes 5 to 20 parts of a second active component, 5 to 20 parts of a second extrusion aid, 10 to 40 parts of a second binder, 1 to 10 parts of a second peptizing agent, and 30 to 60 parts of a second carrier; the second active component includes at least one of nickel, molybdenum, cobalt, and tungsten.

[0019] In the present invention, the first extrusion aid may include at least one of sesbania powder, magnesium stearate and hydroxymethyl cellulose. The above amount of the present invention can improve the molding efficiency and quality of the isomerized catalyst.

[0020] In the present invention, the first binder may include at least one of pseudo-boehmite, alumina, silica, water glass, kaolin, and attapulgite; and the purity of the first binder may be greater than 99%. The above-mentioned amount of the present invention can enhance the interaction between the components of the isomerization catalyst, improving the mechanical strength, durability, and thermal stability of the isomerization catalyst.

[0021] In the present invention, the first peptizing agent may be an acid; the acid may include at least one of nitric acid, formic acid, and hydrochloric acid; and the first peptizing agent may be an acid solution with a concentration of 10 to 30 wt%. The above amount of the present invention can adjust the formation of a colloid of the heterogeneous catalyst precursor and ensure uniformity of the first active component.

[0022] In the present invention, the first support may include at least one of ZSM-23 molecular sieve, ZSM-22 molecular sieve, ZSM-48 molecular sieve, SAPO-11 molecular sieve, and SAPO-34 molecular sieve. The first support of the present invention has needle-shaped or sheet-like ten-membered ring one-dimensional pores and high isomerization activity. The above amount of the first support can improve the stability of the catalyst.

[0023] In the present invention, the specific surface area of ​​the first carrier can be 150 to 400 m 2 / g, the average pore size can be 0.4-0.6nm, the silicon-aluminum ratio can be (60-100):1, and the total acid content can be 0.2-0.8mmol / g. The present invention uses the above-mentioned first carrier to achieve highly selective isomerization of long-chain alkanes and effectively lower the freezing point of bio-jet fuel.

[0024] In the present invention, the second extrusion aid may be the same as the first extrusion aid; the second binder may be the same as the first binder; and the second peptizing agent may be the same as the first peptizing agent.

[0025] In the present invention, the second carrier may include at least one of ZSM-5 molecular sieve and β molecular sieve; the second carrier of the present invention is a microporous molecular sieve having regular pores and a cage structure, and having medium-strong acidic sites on the surface.

[0026] In the present invention, the specific surface area of ​​the second carrier can be 500 to 800 m 2 / g, the average pore size can be 0.5-1nm, the silicon-aluminum ratio can be (70-150):1, and the total acid content can be 0.1-4mmol / g. The second carrier of the present invention can improve the adsorption and cracking efficiency of macromolecules, inhibit excessive cracking, and achieve highly selective cracking of long-chain alkanes.

[0027] In the present invention, the mass ratio of the isomerization catalyst to the cracking catalyst can be 1:(0.2-1). This mass ratio is used to achieve synergistic catalytic hydrogenation, with the isomerization reaction taking the lead and the cracking reaction assisting with moderate chain scission, thereby maximizing the yield of bio-jet fuel and maintaining a stable freezing point below -40°C.

[0028] The present invention provides a method for preparing the composite catalyst described in the above scheme, comprising the following steps:

[0029] The catalyst promoter precursor, the first extrusion aid, the first binder, the first peptizing agent and the first carrier are mixed and then subjected to a first drying, a first calcination, a first active component precursor is loaded and a second calcination in sequence to obtain a heterogeneous catalyst precursor;

[0030] The second extrusion aid, the second binder, the second peptizing agent and the second carrier are mixed, followed by a second drying, a third calcination, loading of the second active component precursor and a fourth calcination to obtain a cracking catalyst precursor;

[0031] The isomerization catalyst precursor and the cracking catalyst precursor are reduced to obtain the composite catalyst comprising the isomerization catalyst and the cracking catalyst.

[0032] In the present invention, the catalyst promoter precursor may include at least one of a silver salt, a lanthanum salt and a copper salt; the silver salt may include at least one of silver nitrate and silver chloride; the lanthanum salt may include at least one of lanthanum chloride and lanthanum nitrate; and the copper salt may include at least one of copper nitrate and copper chloride.

[0033] In the present invention, the first active component precursor may include at least one of nickel salt, molybdenum salt, cobalt salt, iron salt, tungsten oxide and tungsten salt; the nickel salt may include at least one of nickel nitrate, nickel chloride, nickel acetate and nickel acetylacetonate; the molybdenum salt may include at least one of ammonium molybdate and molybdenum nitrate; the cobalt salt may include at least one of cobalt nitrate, cobalt acetate and cobalt chloride; the iron salt may include at least one of ferric nitrate and ferric chloride; the tungsten oxide may be tungsten trioxide; and the tungsten salt may include at least one of ammonium tungstate and ammonium metatungstate.

[0034] In the present invention, the first calcination temperature can be 400-500° C., and the holding time can be 4-6 hours. The present invention improves the thermal stability and mechanical strength of the catalyst and activates the acid sites through the first calcination.

[0035] In the present invention, the second roasting parameters may be consistent with the first roasting parameters.

[0036] In the present invention, the second active component precursor includes at least one of nickel salt, molybdenum salt, cobalt salt, tungsten oxide and tungsten salt; the nickel salt, molybdenum salt, cobalt salt, tungsten oxide and tungsten salt may be consistent with the first active component.

[0037] In the present invention, the parameters of the third and fourth roasting may be consistent with those of the first roasting.

[0038] In the present invention, the reduction temperature may be 400-450° C., and the holding time may be 4-6 hours.

[0039] The present invention provides a method for preparing bio-jet fuel, comprising the following steps:

[0040] After mixing high-condensation-point hydrocarbon-based biodiesel with hydrogen, the mixture is subjected to hydrogenation isomerization reaction and cracking reaction under the action of a composite catalyst, followed by fractionation. The fractionation temperature is less than 140°C, 140-280°C and greater than 280°C. Naphtha is obtained at a temperature less than 140°C, the bio-jet fuel is obtained at a temperature between 140 and 280°C, and low-condensation diesel is obtained at a temperature greater than 280°C. The composite catalyst is the composite catalyst described in the above scheme or the composite catalyst obtained by the preparation method described in the above scheme. The stacking mode of the isomerization catalyst and the cracking catalyst in the composite catalyst is cross-stacked. The number of layers of the isomerization catalyst is 1 to 3. The ratio of the total bed thickness of the isomerization catalyst to the reactor diameter is (5-10):1. The number of layers of the cracking catalyst is 1 to 3. The ratio of the total bed thickness of the cracking catalyst to the reactor diameter is (1-5):1.

[0041] The present invention achieves higher mass transfer and heat transfer efficiency through the above-mentioned total bed thickness setting, and the reactants are fully in contact with the catalyst; the present invention optimizes the conversion of long-chain alkanes through the above-mentioned number of layers, promotes the synergistic effect of the catalysts, reduces side reactions, and improves the yield of bio-jet fuel.

[0042] In the present invention, the carbon number of the high-condensation-point hydrocarbon-based biodiesel may be 15 to 18.

[0043] In the present invention, the space velocity of the high-condensation-point hydrocarbon-based biodiesel can be 0.2-3.0 mL / (g·h), and the volume ratio of hydrogen to high-condensation-point hydrocarbon-based biodiesel (hydrogen-to-oil ratio) can be (300-2000):1.

[0044] In the present invention, the hydroisomerization and cracking reactions can be carried out at a temperature of 200-300°C and a pressure of 3.0-6.0 MPa in a fixed-bed reactor. These conditions improve the rate and selectivity of the isomerization and cracking reactions.

[0045] In the present invention, the calculation formula for the yield of bio-jet fuel is:

[0046] Yield = mass percentage of 140-280°C fraction × total yield of liquid product.

[0047] The present invention is described in detail below with reference to the embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] Table 1

[0050]

[0051]

[0052] Take 8.0g of specific surface area 200m 2 / g, pore size 0.41nm, total acid content 0.42mmol / g, silicon-aluminum ratio of 65 ZSM-22 molecular sieve, add 4.2g pseudo-boehmite and 3.1g alumina, add 3mL of 20wt% dilute nitric acid solution and 2g sesbania powder, mix and knead for 30min to form, dry at 120℃ for 15h and calcine at 500℃ for 5h, then load 15wt% (as a percentage of the precursor mass) nickel nitrate, 3wt% ammonium tungstate, 1wt% silver nitrate, and calcine at 500℃ for 5h to obtain an isomerized catalyst precursor.

[0053] Take 8.0g of the specific surface area of ​​720m 2 / g, pore size 0.74nm, total acid content 2.1mmol / g, silicon-aluminum ratio of 71 beta molecular sieve, add 4.2g pseudo-boehmite and 3.1g alumina, add 3mL of 20wt% dilute nitric acid solution and 2g sesbania powder, mix and knead for 50min to form, dry at 120℃ for 15h and calcine at 500℃ for 5h, then load 15wt% nickel nitrate and 3wt% ammonium tungstate, and calcine at 500℃ for 5h to obtain a cracking catalyst precursor.

[0054] A fixed-bed reactor was loaded with an isomerization catalyst precursor and a cracking catalyst precursor, with the isomerization catalyst precursor forming one layer and the cracking catalyst precursor forming another layer, with the isomerization catalyst precursor on top and the cracking catalyst precursor on the bottom. The ratio of the total bed thickness of the isomerization catalyst precursor to the reactor diameter was 6:1, the ratio of the total bed thickness of the cracking catalyst precursor to the reactor diameter was 3:1, and the mass ratio of the isomerization catalyst precursor to the cracking catalyst precursor was 1:0.5. Hydrogen was introduced at a flow rate of 100 mL / min, and the isomerization catalyst precursor and cracking catalyst precursor were in situ reduced at 450°C for 4 hours to obtain a composite catalyst.

[0055] C15-C18 high-freezing-point hydrocarbon-based biodiesel was pumped into a fixed-bed reactor, and hydrogen was introduced at a hydrogen-to-oil ratio of 1000:1, a space velocity of 0.6 mL / (g·h), a reaction temperature of 270°C, and a reaction pressure of 4 MPa. Biojet fuel was obtained by fractionation according to Table 1, as shown in Table 2.

[0056] Table 2

[0057]

[0058] Note: The percentage refers to the mass ratio of a certain fraction to the total mass of the three fractions; the isomerization ratio refers to the mass ratio of the isomerization product to the normal product, which affects the freezing point.

[0059] Example 2

[0060] The preparation method is the same as that of Example 1, except that:

[0061] Table 3

[0062]

[0063] The loading order is isomerization catalyst precursor at the bottom and cracking catalyst precursor at the top; the ratio of the total bed thickness of the cracking catalyst precursor to the reactor diameter is 2:1; the mass ratio of the cracking catalyst precursor to the isomerization catalyst precursor is 0.3:1; the reaction temperature is 280°C, and biojet fuel is obtained by fractionation, as shown in Table 4.

[0064] Table 4

[0065]

[0066] Example 3

[0067] The preparation method is the same as that of Example 1, except that:

[0068] Table 5

[0069]

[0070] The carrier of the isomerization catalyst has a specific surface area of ​​350m 2 / g, average pore size 0.54nm, total acid content 0.8mmol / g, Si-Al ratio 71 ZSM-48 molecular sieve; cracking catalyst carrier with specific surface area 480m 2 / g, average pore size 3.2nm, total acid content 0.9mmol / g, silicon-aluminum ratio 60 beta molecular sieve;

[0071] The ratio of the total bed thickness of the isomerization catalyst to the reactor diameter was 5:1, the ratio of the total bed thickness of the cracking catalyst to the reactor diameter was 2:1, and the mass ratio of the isomerization catalyst to the cracking catalyst was 1:0.4; the space velocity was 0.5 mL / (g·h), and the reaction temperature was 260℃. The bio-jet fuel was obtained by fractionation, and details are shown in Table 6.

[0072] Table 6

[0073]

[0074] Example 4

[0075] The preparation method was the same as that in Example 1, except that:

[0076] Table 7

[0077]

[0078] The carrier of the isomerization catalyst was ZSM-48 molecular sieve with a specific surface area of 350 m 2 / g, an average pore size of 0.54 nm, a total acid amount of 0.8 mmol / g, and a silicon-aluminum ratio of 71; and the carrier of the cracking catalyst was ZSM-5 molecular sieve with a specific surface area of 270 m 2 / g, an average pore size of 3.2 nm, a total acid amount of 1.5 mmol / g, and a silicon-aluminum ratio of 83.

[0079] The ratio of the total bed thickness of the cracking catalyst to the reactor diameter was 2:1, and the mass ratio of the cracking catalyst to the isomerization catalyst was 0.3:1; the space velocity was 0.5 mL / (g·h), and the reaction temperature was 260℃. The bio-jet fuel was obtained by fractionation, and details are shown in Table 8.

[0080] Table 8

[0081]

[0082] Example 5

[0083] The preparation method was the same as that in Example 1, except that:

[0084] Table 9

[0085]

[0086]

[0087] The ratio of the total bed thickness of the isomerization catalyst to the reactor diameter was 5:1, and the mass ratio of the isomerization catalyst to the cracking catalyst was 1:0.6; the isomerization catalyst precursor and the cracking catalyst precursor were reduced in situ at 400℃ for 5 h; the space velocity was 2.0 mL / (g·h), and the reaction temperature was 290℃. The bio-jet fuel was obtained by fractionation, and details are shown in Table 10.

[0088] Table 10

[0089]

[0090] Example 6

[0091] The preparation method is the same as that of Example 1, except that:

[0092] Table 11

[0093]

[0094] The ratio of the total bed thickness of the isomerization catalyst to the reactor diameter is 5:1, and the mass ratio of the isomerization catalyst to the cracking catalyst is 1:0.7. The isomerization catalyst precursor and the cracking catalyst precursor are reduced in situ at 420℃ for 4.5h; the space velocity is 1.5mL / (g·h), the reaction temperature is 290℃, the reaction pressure is 5MPa, and the bio-jet fuel is obtained by fractionation, as shown in Table 12.

[0095] Table 12

[0096]

[0097] Example 7

[0098] The preparation method is the same as that of Example 1, except that:

[0099] The ratio of the total bed thickness of the isomerization catalyst to the reactor diameter is 5:1, and the mass ratio of the isomerization catalyst to the cracking catalyst is 1:0.2. The isomerization catalyst is stacked in 3 layers, and the cracking catalyst is stacked in 3 layers, and the stacking mode is cross-laminated. The isomerization catalyst precursor and the cracking catalyst precursor are reduced in situ at 450℃ for 4.5h; the space velocity is 1.5mL / (g·h), the reaction temperature is 260℃, the reaction pressure is 4MPa, and the bio-jet fuel is obtained by fractionation, as shown in Table 13.

[0100] Table 13

[0101]

[0102] Comparative Example 1

[0103] The preparation method is the same as that of Example 1, except that the C15-C18 high condensation point hydrocarbon-based biodiesel is replaced by kitchen waste oil heated to 60℃, and the bio-jet fuel is obtained by fractionation, as shown in Table 14.

[0104] Table 14

[0105]

[0106] The bio-jet fuel of the present comparative example presents obvious color, and the effect obviously decreases after the catalyst runs for 100h.

[0107] As shown in Tables 1 to 14, in Comparative Example 1, unrefined kitchen waste oil was used as raw material. Excessive amounts of impurities such as S and Cl affected the activity of the composite catalyst, and long-term operation resulted in poisoning and inactivation of the composite catalyst.

[0108] Comparative Example 2

[0109] Take 8.0g of molecular sieve SAPO-11, mix and knead for 30min, shape, dry at 120℃ for 15h and calcine at 600℃ for 4h to obtain a precursor, load the precursor with 5wt% chloroplatinic acid, and calcine at 500℃ for 5h to obtain an isomerized catalyst precursor.

[0110] Hydrogen was introduced at a flow rate of 100 mL / min, and the isomerized catalyst precursor was in situ reduced at 450° C. for 4 h to obtain the isomerized catalyst.

[0111] The catalyst of this comparative example was loaded into a fixed-bed reactor, and C15-C18 high-condensation-point hydrocarbon-based biodiesel was pumped into the fixed-bed reactor at a hydrogen-to-oil ratio of 1000:1, a space velocity of 0.5 mL / (g·h), a reaction temperature of 320°C, and a pressure of 6 MPa. Biojet fuel was obtained by fractionation, as shown in Table 15.

[0112] Table 15

[0113]

[0114] As shown in Tables 1 to 15, the composite catalyst has the same activity as the noble metal catalyst, the yield is more than 5 percentage points higher, and the freezing point is still below -40°C.

[0115] Comparative Example 3

[0116] Take 3.6g of Y molecular sieve containing nickel and 5.4g of ZSM-22 molecular sieve, add 5.5g of aluminum oxide, 3mL of 20wt% dilute nitric acid solution and 2g of sesbania powder, mix for 35min, shape, dry at 120℃ for 15h and calcine at 500℃ for 5h to obtain a catalyst.

[0117] The catalyst was loaded into a fixed-bed reactor, and C15-C18 high-condensation-point hydrocarbon-based biodiesel was pumped in. Hydrogen was introduced at a hydrogen-to-oil ratio of 1000:1, a space velocity of 0.5 mL / (g·h), a reaction temperature of 280°C, and a pressure of 4 MPa. Biojet fuel was obtained by fractionation, as shown in Table 16.

[0118] Table 16

[0119]

[0120] As shown in Tables 1 to 16, the catalyst of Comparative Example 3 is a mixed molecular sieve of Y molecular sieve and ZSM-22 molecular sieve with metal in situ embedding, and the steps are complicated; the yield of biojet fuel is equivalent to that of the present invention.

[0121] Comparative Example 4

[0122] The preparation was the same as that in Example 3, except that the catalyst promoter 1 wt% lanthanum nitrate was not added, and the biojet fuel was obtained by fractionation, as shown in Table 17.

[0123] Table 17

[0124]

[0125] As shown in Tables 1 to 17, no catalytic promoter was added in Comparative Example 4, and the proportion of aviation kerosene components in Example 3 was high, so the catalyst activity was improved and the catalyst was not deactivated during long-term operation.

[0126] Comparative Example 5

[0127] The preparation is the same as that of Example 3, except that nickel-loaded Y molecular sieve is used and bio-jet fuel is obtained by fractionation, as shown in Table 18.

[0128] Table 18

[0129]

[0130] As shown in Tables 1 to 18, Comparative Example 5 uses nickel-loaded Y molecular sieve, which has a low bio-jet fuel yield, a low iso-stable ratio, and a high freezing point.

[0131] Comparative Example 6

[0132] The sewage oil was pre-hydrogenated with 2000 ppm of molybdenum-containing liquid catalyst, reaction temperature of 300-380°C, hydrogen pressure of 8 MPa, and mass space velocity of 1.0 h -1 , hydrogen-to-oil ratio 800:1, and a first-stage hydrogenation product was obtained.

[0133] The primary hydrogenation product is supplemented with hydrogenation to improve its quality. A supported transition metal sulfide hydrogenation refining catalyst is used. The reaction temperature is 300-340°C, the hydrogen pressure is 4 MPa, and the mass space velocity is 1.5 h -1 , hydrogen-to-oil ratio 600:1, and secondary hydrogenation product was obtained.

[0134] The secondary hydrogenation product is subjected to hydrocracking isomerization reaction using a non-sulfurized transition metal hydroisomerization catalyst containing molecular sieves, a reaction temperature of 280-320°C, a hydrogen pressure of 4 MPa, and a mass space velocity of 2.0 h -1 , hydrogen-to-oil ratio 500:1, fractional distillation to obtain bio-jet fuel, see Table 19 for details.

[0135] Table 19

[0136]

[0137] As can be seen from Tables 1 to 19, the preparation process of Comparative Example 6 is long, the equipment cost is high, and the production efficiency is low.

[0138] Comparative Example 7

[0139] The preparation is the same as that of Example 3, except that: referring to CN116064107A, ZSM-5 molecular sieve and β molecular sieve loaded with tungsten and nickel are used to fractionate and obtain bio-jet fuel, as shown in Table 20.

[0140] Table 20

[0141]

[0142] As shown in Tables 1 to 20, Comparative Example 7 uses modified ZSM-5 and β molecular sieve as catalysts, and the active components are metal tungsten and nickel, resulting in low bio-jet fuel yield, low iso-to-stable ratio, and high freezing point.

[0143] Although the above embodiments describe the present invention in detail, they are not all embodiments. Other embodiments obtained based on this embodiment without inventiveness are all within the scope of protection of the present invention.

Claims

1. A composite catalyst comprising an isomerization catalyst and a cracking catalyst; The isomerization catalyst comprises, by weight, 5 to 20 parts of a first active component, 0.5 to 3 parts of a catalyst promoter, 5 to 20 parts of a first extrusion aid, 10 to 40 parts of a first binder, 1 to 10 parts of a first peptizing agent, and 30 to 60 parts of a first carrier. The first active component includes at least one of nickel, molybdenum, cobalt, iron and tungsten; The catalyst promoter includes at least one of silver, lanthanum and copper; The first carrier comprises at least one of ZSM-23 molecular sieve, ZSM-22 molecular sieve, ZSM-48 molecular sieve, SAPO-11 molecular sieve and SAPO-34 molecular sieve; The cracking catalyst comprises, by weight, 5 to 20 parts of a second active component, 5 to 20 parts of a second extrusion aid, 10 to 40 parts of a second binder, 1 to 10 parts of a second peptizing agent, and 30 to 60 parts of a second carrier. The second active component includes at least one of nickel, molybdenum, cobalt and tungsten; The second carrier includes at least one of a ZSM-5 molecular sieve and a beta molecular sieve.

2. The composite catalyst according to claim 1, characterized in that The mass ratio of the isomerization catalyst to the cracking catalyst is 1:(0.2-1).

3. The composite catalyst according to claim 1, characterized in that The specific surface area of ​​the first carrier is 150 to 400 m 2 / g, the average pore size is 0.4-0.6nm, the silicon-aluminum ratio is (60-100):1, and the total acid content is 0.2-0.8mmol / g.

4. The composite catalyst according to claim 1, characterized in that The specific surface area of ​​the second carrier is 500 to 800 m 2 / g, the average pore size is 0.5-1nm, the silicon-aluminum ratio is (70-150):1, and the total acid content is 0.1-4mmol / g.

5. The method for preparing the composite catalyst according to any one of claims 1 to 4, comprising the following steps: The catalyst promoter precursor, the first extrusion aid, the first binder, the first peptizing agent and the first carrier are mixed and then subjected to a first drying, a first calcination, a first active component precursor is loaded and a second calcination in sequence to obtain a heterogeneous catalyst precursor; The second extrusion aid, the second binder, the second peptizing agent and the second carrier are mixed, followed by a second drying, a third calcination, loading of the second active component precursor and a fourth calcination to obtain a cracking catalyst precursor; The isomerization catalyst precursor and the cracking catalyst precursor are reduced to obtain the composite catalyst comprising the isomerization catalyst and the cracking catalyst.

6. The preparation method according to claim 5, characterized in that: The reduction temperature is 400-450° C., and the insulation time is 4-6 hours.

7. A method for preparing bio-jet fuel, comprising the following steps: The high-freezing-point hydrocarbon-based biodiesel is mixed with hydrogen and subjected to a hydroisomerization reaction and a cracking reaction under the action of a composite catalyst, followed by fractionation, wherein the fractionation temperature is less than 140° C., 140-280° C., and greater than 280° C., wherein naphtha is obtained at less than 140° C., the bio-jet fuel is obtained at 140-280° C., and low-freezing-point diesel is obtained at a temperature greater than 280° C.; The composite catalyst is the composite catalyst according to any one of claims 1 to 5 or the composite catalyst obtained by the preparation method according to claim 6; The stacking mode of the isomerization catalyst and the cracking catalyst in the composite catalyst is cross-layered; The number of layers of isomerized catalyst in the composite catalyst is 1 to 3; The ratio of the total bed thickness of the isomerization catalyst to the reactor diameter is (5-10):1; The number of layers of cracking catalyst in the composite catalyst is 1 to 3; The ratio of the total bed thickness of the cracking catalyst to the reactor diameter is (1-5):

1.

8. The preparation method according to claim 7, characterized in that: The space velocity of the high-condensation-point hydrocarbon-based biodiesel is 0.2 to 3.0 mL / (g·h).

9. The preparation method according to claim 7, characterized in that: The temperature of the hydroisomerization reaction and the cracking reaction is 200-300° C., and the pressure is 3.0-6.0 MPa.

10. The preparation method according to claim 7, characterized in that: The volume ratio of the hydrogen to the high-condensation-point hydrocarbon-based biodiesel is (300-2000):1.

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