CN112934254B - Dual-function catalyst for catalyzing n-heptane conversion and preparation method thereof - Google Patents
Dual-function catalyst for catalyzing n-heptane conversion and preparation method thereof Download PDFInfo
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
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- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
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- C07C4/02—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
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- C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
- C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
- C07C5/2767—Changing the number of side-chains
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- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G45/00—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds
- C10G45/58—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to change the structural skeleton of some of the hydrocarbon content without cracking the other hydrocarbons present, e.g. lowering pour point; Selective hydrocracking of normal paraffins
- C10G45/60—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to change the structural skeleton of some of the hydrocarbon content without cracking the other hydrocarbons present, e.g. lowering pour point; Selective hydrocracking of normal paraffins characterised by the catalyst used
- C10G45/64—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to change the structural skeleton of some of the hydrocarbon content without cracking the other hydrocarbons present, e.g. lowering pour point; Selective hydrocracking of normal paraffins characterised by the catalyst used containing crystalline alumino-silicates, e.g. molecular sieves
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- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
- B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
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- C07C2529/00—Catalysts comprising molecular sieves
- C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
- C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- C07C2529/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
- C07C2529/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11 containing iron group metals, noble metals or copper
- C07C2529/44—Noble metals
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2529/00—Catalysts comprising molecular sieves
- C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
- C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- C07C2529/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
- C07C2529/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11 containing iron group metals, noble metals or copper
- C07C2529/46—Iron group metals or copper
Abstract
The application discloses a bifunctional catalyst, which comprises a molecular sieve and a metal with hydrogenation function supported on the molecular sieve; the molecular sieve is a hierarchical pore ZSM-5 molecular sieve with an MFI topological structure. The application also discloses a preparation method of the bifunctional catalyst, which at least comprises the following steps: (1) The microporous molecular sieve is treated by desilication to obtain a multi-level porous molecular sieve; (2) Adding the hierarchical porous molecular sieve into a solution containing a metal element precursor, and obtaining the bifunctional catalyst through reaction, drying and roasting. The double-function catalyst used for catalyzing the n-heptane conversion is a high-efficiency catalyst for preparing other hydrocarbon products by the n-heptane catalytic conversion, and has the advantages of simple composition and low-cost and easily-obtained raw materials. The preparation method of the bifunctional catalyst has the advantages of simple process and mild condition, and can be used for large-scale industrial production.
Description
Technical Field
The application relates to a bifunctional catalyst for catalyzing n-heptane conversion and a preparation method thereof, belonging to the field of catalyst synthesis.
Background
Catalytic reforming and isomerization are important reaction pathways in petroleum processing. In particular, the normal alkane isomerization reaction is an ideal route which meets the increasingly strict environmental protection regulations at present, improves the fuel quality and weakens the adverse effect on the environment. The isomerization of light alkanes of C4 to C6 has been largely studied to develop more sophisticated technology and with successfully operated industrial units. There is a relatively high content of n-heptane in the reformate feedstock and therefore isomerisation of n-heptane is of great importance for improving the quality of gasoline.
The catalyst is a key factor influencing normal alkane isomerization reaction, and the expansion application of light alkane isomerization catalysts such as platinum halide/alumina, platinum/mercerized molecular sieve and the like to long-chain alkane isomerization reaction with more than 7 carbon atoms can cause serious cracking reaction, so that the hydrogen consumption is increased, and the yield of isomerized liquid products is greatly reduced (Appl.Catal.A, 1998,166,29;Micropor.Mesopor.Mater, 2012,164,222). Hydroisomerization of normal paraffins is a complex reaction process requiring that the bi-functional catalyst maintain a proper ratio of acid sites to metal sites, with stronger acid sites leading to increased cracking reactions. For traditional aluminum-rich molecular sieves such as FAU, BEA, etc., the isomerization selectivity is significantly lower due to the large number of acidic sites (J.Catal., 2013,307,122;J.Catal, 1996,162,179). The silicon-aluminum ratio of the ZSM-5 molecular sieve with the MFI structure can be modulated in a large interval, so that the number and the strength of the acid sites of the ZSM-5 molecular sieve can be controlled, and the ZSM-5 molecular sieve has certain advantages in constructing the bifunctional isomerization catalyst. However, the pore structure of the ten-membered ring leads to smaller pore diameter and limited diffusion performance. Therefore, the method starts from the modulation of the pore channel structure, improves the diffusion performance of the catalyst, and is an effective means for constructing the high-efficiency isomerization catalyst.
Disclosure of Invention
According to one aspect of the present application, a dual function catalyst is provided that can catalyze the conversion of n-heptane to hydrocarbon products such as isoheptane, propane, butane, pentane, and the like.
A bifunctional catalyst, characterized in that the catalyst comprises a molecular sieve and a hydrogenation-functional metal supported on the molecular sieve;
the molecular sieve is a hierarchical pore ZSM-5 molecular sieve with an MFI topological structure;
optionally, the hierarchical pore molecular sieve has micropores of 0.52-0.56 nm and mesopores of 8-15 nm.
Optionally, the metal element is at least one selected from platinum, palladium and nickel.
Optionally, the metal element accounts for 0.05 to 1.5wt% of the bifunctional catalyst.
Optionally, the metal element accounts for 0.15 to 1.2wt% of the bifunctional catalyst.
Optionally, the metal comprises an upper limit of the bifunctional catalyst selected from 1.5wt%, 1.4wt%, 1.3wt%, 1.2wt%, 1.1wt%, 1.0wt%, 0.9wt% or 0.8wt%; the lower limit is selected from 0.7wt%, 0.6wt%, 0.5wt%, 0.4wt%, 0.3wt%, 0.2wt%, 0.1wt% or 0.05wt%.
Optionally, the molecular sieve comprises 98.5 to 99.95wt% of the bifunctional catalyst.
Optionally, the molecular sieve comprises an upper limit of the bifunctional catalyst selected from 99.95wt%, 99.9wt%, 99.85wt%, 99.8wt%, 99.7wt%, 99.6wt%, 99.5wt%, 99.4wt%, or 99.3wt%; the lower limit is selected from 99.2wt%, 99.1wt%, 99wt%, 98.9wt%, 98.8wt%, 98.7wt%, 98.6wt% or 98.5wt%.
Optionally, the molecular sieve comprises 98.8 to 99.85wt% of the bifunctional catalyst.
Optionally, the preparation method of the bifunctional catalyst at least comprises the following steps:
(1) The microporous molecular sieve is treated by desilication to obtain a multi-level porous molecular sieve;
(2) Adding the hierarchical porous molecular sieve into a solution containing a metal element precursor, and obtaining the bifunctional catalyst through reaction, drying and roasting.
Optionally, the metal element precursor is selected from at least one of chloroplatinic acid, palladium chloride and nickel nitrate which are soluble in water;
optionally, the desilication treatment in the step (1) is to treat the microporous molecular sieve raw powder in an alkali solution and then carry out ammonia exchange treatment.
Optionally, the desilication treatment in the step (1) is to treat the microporous molecular sieve raw powder in sodium hydroxide aqueous solution and then perform ammonia exchange treatment.
Optionally, siO of the microporous molecular sieve raw powder 2 /Al 2 O 3 The molar ratio is 50-200.
Optionally, siO of the microporous molecular sieve raw powder 2 /Al 2 O 3 The upper limit of the molar ratio is selected from 100, 150, 200, 250, 300, 350, 400, 450 or 500; the lower limit is selected from 50, 100, 150, 200, 250, 300, 350, 400, or 450.
Optionally, the alkali solution is at least one selected from aqueous solutions of sodium hydroxide and tetrapropylammonium hydroxide.
Optionally, the concentration of the alkali solution is 0.2-1.0M.
Optionally, the solid-liquid ratio of the microporous molecular sieve raw powder to the alkali solution is 1 g/10-50 ml.
Optionally, the solid-to-liquid ratio of the microporous molecular sieve raw powder to the sodium hydroxide solution is 1g/20ml.
Optionally, the desilication treatment is to disperse the microporous molecular sieve raw powder in an alkali solution, stir the solution for 0.5 to 1 hour at 65 to 85 ℃, separate out a solid product, wash the solid product to be neutral and dry the solid product at 90 to 120 ℃.
Optionally, the ammonia exchange is to treat the desilication molecular sieve with ammonium nitrate aqueous solution at 60-100 ℃ for at least 2 hours, separate out solid, repeat the process for at least 2 times, dry the solid product at 90-120 ℃ and bake for 4-6 hours in air atmosphere at 400-600 ℃.
Optionally, the temperature of the post-treatment is 65-85 ℃.
Alternatively, the ammonia exchange is carried out by treating with an aqueous solution of ammonium nitrate at 80 ℃ for 2 hours, separating out solids, repeating the process 3 times, drying the product at 100 ℃, and calcining in air at 550 ℃ for 4 hours.
Optionally, in the step (2), adding the hierarchical pore molecular sieve obtained in the step (1) into a solution containing a metal element precursor, and stirring for 2-30 hours at the temperature of 20-50 ℃; and then stirring the mixture at the temperature of between 50 and 90 ℃ until the solvent is evaporated to dryness to obtain a solid sample, and roasting the solid sample in the air atmosphere at the temperature of between 400 and 600 ℃ for 4 to 6 hours to obtain the bifunctional catalyst.
Alternatively, the reaction in step (2) is: stirring for 2-30 hours at the temperature of 20-50 ℃; then stirring the mixture until the solvent is evaporated to dryness in the temperature range of 50-90 ℃ to obtain a solid sample.
According to a further aspect of the present application there is provided a catalyst for the conversion of n-heptane, characterised in that it comprises at least one of the bifunctional catalysts described above, the bifunctional catalysts prepared by any of the methods described above.
According to a further aspect of the present application there is provided a process for the conversion of n-heptane, characterised in that a feedstock containing n-heptane and hydrogen is passed into a reactor to be contacted with a catalyst to react to obtain a hydrocarbon product comprising isoheptane, propane, butane, pentane.
Optionally, the catalyst comprises the catalyst for catalyzing the conversion of n-heptane.
Optionally, the reaction conditions include:
the reaction temperature is 180-350 ℃, the reaction pressure is 0.1-4.0 Mpa, the mass airspeed of n-heptane is 0.2-3.0 g/g/h, and the molar ratio of hydrogen to heptane is 4-30.
Optionally, the reaction conditions include:
the reaction temperature is 260-350 ℃, the reaction pressure is 1.0-4.0 Mpa, the mass airspeed of the n-heptane is 0.5-2.0 g/g/h, and the molar ratio of the hydrogen to the heptane is 13-30.
Alternatively, the upper limit of the reaction temperature is selected from 350 ℃, 330 ℃, 310 ℃, 300 ℃, 280 ℃, 260 ℃, 250 ℃, 240 ℃, 220 ℃, 200 ℃, or 190 ℃; the lower limit is selected from 330 ℃, 310 ℃, 300 ℃, 280 ℃, 260 ℃, 250 ℃, 240 ℃, 220 ℃, 200 ℃, 190 ℃ or 180 ℃.
Optionally, the upper limit of the reaction pressure is selected from 0.2Mpa, 0.3Mpa, 0.4Mpa, 0.5Mpa, 1.0Mpa, 1.5Mpa, 2.0Mpa, 2.5Mpa, 3.0Mpa, 3.5Mpa or 4.0Mpa; the lower limit is selected from 0.1Mpa, 0.2Mpa, 0.3Mpa, 0.4Mpa, 0.5Mpa, 1.0Mpa, 1.5Mpa, 2.0Mpa, 2.5Mpa, 3.0Mpa or 3.5Mpa.
Optionally, the upper limit of the n-heptane mass space velocity is selected from 0.5g/g/h, 0.82g/g/h, 1.0g/g/h, 1.5g/g/h, 2.0g/g/h, 2.5g/g/h or 3.0g/g/h; the lower limit is selected from 0.2g/g/h, 0.5g/g/h, 0.82g/g/h, 1.0g/g/h, 1.5g/g/h, 2.0g/g/h or 2.5g/g/h.
Optionally, the upper limit of the hydrogen to heptane molar ratio is selected from 6, 8, 10, 13, 15, 20, 25 or 30; the lower limit is selected from 4, 6, 8, 10, 13, 15, 20 or 25.
Optionally, the catalyst is pretreated for 0.5-2 hours at 400-500 ℃ in a reducing atmosphere before the reaction.
Optionally, the reducing atmosphere comprises at least one of hydrogen, a hydrogen/argon mixture, and a hydrogen/helium mixture.
The beneficial effects that this application can produce include:
1) The double-function catalyst used for catalyzing the n-heptane conversion is a high-efficiency catalyst for preparing other hydrocarbon products by the n-heptane catalytic conversion, and has the advantages of simple composition and low-cost and easily-obtained raw materials.
2) The preparation method of the bifunctional catalyst for catalyzing n-heptane conversion has the advantages of simple process and mild condition, and can be used for large-scale industrial production.
Drawings
FIG. 1 is a nitrogen physisorption isotherm of the hierarchical pore ZSM-5 molecular sieve obtained in example 1 of the present application.
FIG. 2 is a pore distribution curve of a multi-pore ZSM-5 molecular sieve obtained in example 1 of the present application.
Detailed Description
The present application is described in detail below with reference to examples, but the present application is not limited to these examples.
Unless specifically stated, all materials used in the present application are commercially available and are used without special treatment.
ZSM-5 zeolite molecular sieve was purchased from Nankai university catalyst plant, siO 2 /Al 2 O 3 The molar ratio is 50-200.The ZSM-5 zeolite molecular sieve purchased is microporous ZSM-5 zeolite molecular sieve raw powder.
Adsorption isotherms and pore size distribution tests were performed on an ASAP-2020 physical adsorption instrument.
Product analysis was performed on an Agilent 7890B gas chromatograph, FID detector, FFAP column analysis.
In the examples, the conversion of n-heptane was calculated as follows:
the calculation method of the selectivity of the hydrocarbon C-based product comprises the following steps:
example 1 preparation of catalyst
Weigh 10g SiO 2 /Al 2 O 3 The ZSM-5 molecular sieve with the molar ratio of 50 is dispersed in 200ml of 0.2M sodium hydroxide aqueous solution, stirred for 0.5h at 65 ℃, solid products are centrifugally separated, washed to be neutral and dried at 100 ℃.5g of sodium hydroxide treated molecular sieve is weighed and dispersed in 100ml of 0.8M ammonium nitrate aqueous solution, stirred for 2 hours at 80 ℃, centrifugally separated, the process is repeated for 3 times, and the solid product is dried at 100 ℃ and roasted for 4 hours in air at 550 ℃ to obtain the multi-level hole ZSM-5 molecular sieve. FIG. 1 is a nitrogen physical adsorption isotherm of a multistage pore ZSM-5 molecular sieve, and it can be seen from FIG. 1 that the material presents a composite isotherm of type I and type IV, and a significant hysteresis loop exists between the relative pressures of 0.45-1.0; FIG. 2 is a graph showing the pore distribution curve of the obtained multi-pore ZSM-5 molecular sieve, which has a concentrated distribution around 10nm in pore diameter. In conclusion, it is explained that the multistage pore ZSM-5 molecular sieve obtained in this example has both micropores and mesopores.
Dissolving 0.067ml77mM chloroplatinic acid aqueous solution in 10ml water, adding 1.999g hierarchical pore ZSM-5 molecular sieve, stirring at 20 ℃ for 30h, continuously stirring at 50 ℃ until the solution is evaporated to dryness, and roasting the obtained powder in 550 ℃ air atmosphere for 4h to obtain the platinum/hierarchical pore molecular sieve doubleFunctional catalyst, designated sample 1 # 。
Example 2 preparation of catalyst
Weighing 10g of SiO 2 /Al 2 O 3 The ZSM-5 molecular sieve with the molar ratio of 200 is dispersed in 200ml of 0.2M sodium hydroxide aqueous solution, stirred for 0.5h at 65 ℃, solid products are centrifugally separated, washed to be neutral and dried at 100 ℃.5g of sodium hydroxide treated molecular sieve is weighed and dispersed in 100ml of 0.8M ammonium nitrate aqueous solution, stirred for 2 hours at 80 ℃, centrifugally separated, the process is repeated for 3 times, and the solid product is dried at 100 ℃ and roasted for 4 hours in air at 550 ℃ to obtain the multi-level hole ZSM-5 molecular sieve. The nitrogen physisorption isotherm and pore distribution curve of this hierarchical pore ZSM-5 molecular sieve were similar to those of example 1.
Dissolving 0.067ml77mM chloroplatinic acid aqueous solution in 10ml water, adding 1.999g hierarchical pore ZSM-5 molecular sieve, stirring at 50 ℃ for 2 hours, continuously stirring at 90 ℃ until the solution is evaporated to dryness, and roasting the obtained powder in 550 ℃ air atmosphere for 4 hours to obtain a platinum/hierarchical pore molecular sieve bifunctional catalyst, which is marked as sample No. 2.
Example 3 preparation of catalyst
Weighing 10g of SiO 2 /Al 2 O 3 The ZSM-5 molecular sieve with the molar ratio of 50 is dispersed in 200ml of 0.2M sodium hydroxide aqueous solution, stirred for 0.5h at 65 ℃, solid products are centrifugally separated, washed to be neutral and dried at 100 ℃.5g of sodium hydroxide treated molecular sieve is weighed and dispersed in 100ml of 0.8M ammonium nitrate aqueous solution, stirred for 2 hours at 80 ℃, centrifugally separated, the process is repeated for 3 times, and the solid product is dried at 100 ℃ and roasted for 4 hours in air at 550 ℃ to obtain the multi-level hole ZSM-5 molecular sieve. The nitrogen physisorption isotherm and pore distribution curve of this hierarchical pore ZSM-5 molecular sieve were similar to those of example 1.
Dissolving 0.266ml of 77mM chloroplatinic acid aqueous solution in 10ml of water, adding 1.996g hierarchical pore ZSM-5 molecular sieve, stirring at 20 ℃ for 16h, continuously stirring at 60 ℃ until the solution is evaporated to dryness, and roasting the obtained powder in 550 ℃ air atmosphere for 4h to obtain a platinum/hierarchical pore molecular sieve bifunctional catalyst, which is marked as sample No. 3.
Example 4 preparation of catalyst
Weighing 10g of SiO 2 /Al 2 O 3 The ZSM-5 molecular sieve with the molar ratio of 50 is dispersed in 200ml of 0.2M sodium hydroxide aqueous solution, stirred for 0.5h at 65 ℃, solid products are centrifugally separated, washed to be neutral and dried at 100 ℃.5g of sodium hydroxide treated molecular sieve is weighed and dispersed in 100ml of 0.8M ammonium nitrate aqueous solution, stirred for 2 hours at 80 ℃, centrifugally separated, the process is repeated for 3 times, and the solid product is dried at 100 ℃ and roasted for 4 hours in air at 550 ℃ to obtain the multi-level hole ZSM-5 molecular sieve. The nitrogen physisorption isotherm and pore distribution curve of this hierarchical pore ZSM-5 molecular sieve were similar to those of example 1.
0.33ml of 0.113M palladium chloride aqueous solution is taken and dissolved in 10ml of water, 1.996g of multi-level pore ZSM-5 molecular sieve is added, stirring is carried out for 16h at 20 ℃, stirring is continued at 60 ℃ until the solution is evaporated to dryness, the obtained powder is roasted for 4h in an air atmosphere at 550 ℃, and the palladium/multi-level pore molecular sieve dual-function catalyst is marked as sample No. 4.
Example 5 preparation of catalyst
Weighing 10g of SiO 2 /Al 2 O 3 The ZSM-5 molecular sieve with the molar ratio of 50 is dispersed in 200ml of 0.2M sodium hydroxide aqueous solution, stirred for 0.5h at 65 ℃, solid products are centrifugally separated, washed to be neutral and dried at 100 ℃.5g of sodium hydroxide treated molecular sieve is weighed and dispersed in 100ml of 0.8M ammonium nitrate aqueous solution, stirred for 2 hours at 80 ℃, centrifugally separated, the process is repeated for 3 times, and the solid product is dried at 100 ℃ and roasted for 4 hours in air at 550 ℃ to obtain the multi-level hole ZSM-5 molecular sieve. The nitrogen physisorption isotherm and pore distribution curve of this hierarchical pore ZSM-5 molecular sieve were similar to those of example 1.
0.0934g of nickel nitrate is taken and dissolved in 10ml of water, 1.97g of multi-stage pore ZSM-5 molecular sieve is added, stirring is carried out for 16h at 20 ℃, stirring is continued at 60 ℃ until the solution is evaporated to dryness, the obtained powder is roasted for 4h in 550 ℃ air atmosphere, and the nickel/multi-stage pore molecular sieve dual-function catalyst is marked as sample No. 5.
Comparative example 1 preparation of catalyst
Weighing 10g of SiO 2 /Al 2 O 3 Dispersing ZSM-5 molecular sieve with a molar ratio of 50 in 200ml of 0.2M sodium hydroxide aqueous solution, stirring for 0.5h at 65 ℃, centrifuging to separate a solid product, washing to be neutral, and drying at 100 DEG C.5g of sodium hydroxide-treated molecular sieve was weighed and dispersed in 100ml of a 0.8M aqueous ammonium nitrate solution, stirred at 80℃for 2 hours, centrifuged, and the procedure was repeated 3 times, and the solid product was dried at 100℃and calcined in air at 550℃for 4 hours to give a multi-pore ZSM-5 molecular sieve, designated as sample D1.
Comparative example 2 preparation of catalyst
0.266ml of 77mM chloroplatinic acid aqueous solution was dissolved in 10ml of water, and 1.996g SiO was added 2 /Al 2 O 3 The ZSM-5 molecular sieve with the molar ratio of 50 is stirred for 16 hours at 20 ℃, the mixture is continuously stirred at 60 ℃ until the solution is evaporated to dryness, and the obtained powder is roasted for 4 hours in an air atmosphere at 550 ℃ to obtain the platinum/multi-stage pore molecular sieve bifunctional catalyst which is marked as a sample D2.
Example 6 use of catalyst
0.5g of 3# catalyst which is subjected to tabletting and sieving by a 20-40 mesh sieve is weighed. The mixture is put into a fixed bed reactor, pretreated for 60min at 450 ℃ in a hydrogen atmosphere, then the temperature is reduced to 260 ℃, the hydrogen pressure is regulated to 2.0Mpa, raw material n-heptane is introduced to start the reaction, the mass airspeed of the n-heptane is 0.82g/g/h, the molar ratio of the hydrogen to the n-heptane is 13, and the analysis is carried out after the reaction for 2h.
Product analysis was performed on-line using Agilent gas chromatography 7890, FID detector, FFAP capillary column.
The reaction results were as follows:
the n-heptane conversion was 38.2%, the isoheptane selectivity was 20.8%, the propane selectivity was 36.8%, the butane selectivity was 2.0%, and the pentane selectivity was 1.0%.
Example 7 use of a catalyst
0.5g of 3# catalyst which is subjected to tabletting and sieving by a 20-40 mesh sieve is weighed. The mixture is put into a fixed bed reactor, pretreated for 60min at 450 ℃ in a hydrogen atmosphere, then the temperature is reduced to 350 ℃, the hydrogen pressure is regulated to 2.0Mpa, raw material n-heptane is introduced to start the reaction, the mass airspeed of the n-heptane is 0.82g/g/h, the molar ratio of the hydrogen to the n-heptane is 30, and the analysis is carried out after the reaction for 2h.
Product analysis was performed on-line using Agilent gas chromatography 7890, FID detector, FFAP capillary column.
The reaction results were as follows:
the n-heptane conversion was 44.2%, the isoheptane selectivity was 15.6%, the propane selectivity was 39.8%, the butane selectivity was 1.6%, and the pentane selectivity was 0.8%.
Example 8 use of catalyst
0.5g of the 4# catalyst which is subjected to tabletting and sieving by a 20-40 mesh sieve is weighed. The mixture is put into a fixed bed reactor, pretreated for 60min at 450 ℃ in a hydrogen atmosphere, then the temperature is reduced to 260 ℃, the hydrogen pressure is regulated to 2.0Mpa, raw material n-heptane is introduced to start the reaction, the mass airspeed of the n-heptane is 0.82g/g/h, the molar ratio of the hydrogen to the n-heptane is 13, and the analysis is carried out after the reaction for 2h.
Product analysis was performed on-line using Agilent gas chromatography 7890, FID detector, FFAP capillary column.
The reaction results were as follows:
the n-heptane conversion was 40.4%, the isoheptane selectivity was 18.6%, the propane selectivity was 37.8%, the butane selectivity was 1.9%, and the pentane selectivity was 1.1%.
Example 10 use of catalyst
0.5g of 5# catalyst which is pressed into tablets and sieved by a 20-40 mesh sieve is weighed. The mixture is put into a fixed bed reactor, pretreated for 60min at 450 ℃ in a hydrogen atmosphere, then the temperature is reduced to 260 ℃, the hydrogen pressure is regulated to 2.0Mpa, raw material n-heptane is introduced to start the reaction, the mass airspeed of the n-heptane is 0.82g/g/h, the molar ratio of the hydrogen to the n-heptane is 13, and the analysis is carried out after the reaction for 2h.
Product analysis was performed on-line using Agilent gas chromatography 7890, FID detector, FFAP capillary column.
The reaction results were as follows:
the n-heptane conversion was 30.6%, the isoheptane selectivity was 15.6%, the propane selectivity was 41.8%, the butane selectivity was 1.4%, and the pentane selectivity was 0.6%.
Example 11 evaluation of catalyst
The catalyst was treated as in example 7, except that the catalyst and reaction conditions were changed. The reaction results are shown in Table 1.
TABLE 1 Performance of different catalysts to catalyze the conversion of n-heptane
As can be seen from Table 1, the multi-stage pore molecular sieve supported metal dual-function catalyst has significantly higher selectivity for n-heptane isomerization than the microporous catalyst and the single molecular sieve system.
The foregoing description is only a few examples of the present application and is not intended to limit the present application in any way, and although the present application is disclosed in the preferred examples, it is not intended to limit the present application, and any person skilled in the art may make some changes or modifications to the disclosed technology without departing from the scope of the technical solution of the present application, and the technical solution is equivalent to the equivalent embodiments.
Claims (17)
1. A method for catalyzing n-heptane conversion, which is characterized in that a raw material containing n-heptane and hydrogen is introduced into a reactor to contact with a bifunctional catalyst for reaction to obtain hydrocarbon products containing isoheptane, propane, butane and pentane;
the reaction conditions include:
the reaction temperature is 180-350 ℃, the reaction pressure is 0.1-4.0 mpa, the mass airspeed of n-heptane is 0.2-3.0 g/g/h, and the molar ratio of hydrogen to heptane is 4-30;
the double-function catalyst comprises a molecular sieve and a metal element with a hydrogenation function loaded on the molecular sieve;
the molecular sieve is a hierarchical pore ZSM-5 molecular sieve with an MFI topological structure;
the hierarchical pore molecular sieve has micropores of 0.52-0.56 nm and mesopores of 8-15 nm.
2. The method according to claim 1, wherein the metal element is at least one selected from the group consisting of platinum, palladium, and nickel.
3. The method according to claim 1, wherein the metal element accounts for 0.05-1.5wt% of the bifunctional catalyst;
the molecular sieve accounts for 98.5-99.95wt% of the bifunctional catalyst.
4. The method according to claim 1, wherein the metal element accounts for 0.15-1.2wt% of the bifunctional catalyst;
the molecular sieve accounts for 98.8-99.85wt% of the bifunctional catalyst.
5. The method according to claim 1, characterized in that the preparation method of the bifunctional catalyst comprises at least the following steps:
(1) The microporous molecular sieve is treated by desilication to obtain a multi-level porous molecular sieve;
(2) Adding the hierarchical pore molecular sieve into a solution containing a metal element precursor, and obtaining the catalyst for catalyzing n-heptane conversion through reaction, drying and roasting.
6. The method according to claim 5, wherein the metal element precursor is selected from at least one of chloroplatinic acid, palladium chloride, and nickel nitrate that are soluble in water.
7. The method according to claim 5, wherein the desilication treatment in step (1) is carried out by treating the raw microporous molecular sieve powder in an alkaline solution and then carrying out ammonia exchange treatment.
8. The method of claim 7, wherein the SiO of the microporous molecular sieve raw meal 2 /Al 2 O 3 The molar ratio is 50-200.
9. The method according to claim 7, wherein the alkaline solution is at least one selected from the group consisting of aqueous solutions of sodium hydroxide and tetrapropylammonium hydroxide.
10. The method of claim 7, wherein the concentration of the alkaline solution is 0.2-1.0 m.
11. The method according to claim 7, wherein the solid-to-liquid ratio of the microporous molecular sieve raw powder to the alkali solution is 1 g/10-50 ml.
12. The method according to claim 7, wherein the desilication treatment is to disperse the raw micro-molecular sieve powder in an alkali solution, stir the solution for 0.5 to 1 hour at 65 to 85 ℃, separate out a solid product, wash the solid product to be neutral, and dry the solid product at 90 to 120 ℃.
13. The method according to claim 7, wherein the ammonia exchange is carried out by treating the desilicated molecular sieve with ammonium nitrate aqueous solution at 60-100 ℃ for not less than 2 hours, separating out solid, repeating the process for not less than 2 times, drying the solid product at 90-120 ℃, and roasting at 400-600 ℃ in air atmosphere for 4-6 hours.
14. The method according to claim 5, wherein in the step (2), the hierarchical pore molecular sieve obtained in the step (1) is added into a solution containing a metal element precursor, and stirred for 2-30 hours at a temperature ranging from 20 ℃ to 50 ℃; and then stirring the mixture at the temperature of 50-90 ℃ until the solvent is evaporated to dryness to obtain a solid sample, and roasting the solid sample for 4-6 hours in an air atmosphere at the temperature of 400-600 ℃ to obtain the bifunctional catalyst.
15. The method of claim 1, wherein the reaction conditions comprise:
the reaction temperature is 260-350 ℃, the reaction pressure is 1.0-4.0 mpa, the mass airspeed of the n-heptane is 0.5-2.0 g/g/h, and the molar ratio of hydrogen to heptane is 13-30.
16. The method according to claim 1, wherein the bifunctional catalyst is pretreated in a reducing atmosphere at 400-500 ℃ for 0.5-2 h before the reaction.
17. The method of claim 16, wherein the reducing atmosphere comprises at least one of hydrogen, a hydrogen/argon mixture, and a hydrogen/helium mixture.
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