CN114229869B - Hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree, preparation method and application - Google Patents
Hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree, preparation method and application Download PDFInfo
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- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/46—Other types characterised by their X-ray diffraction pattern and their defined composition
- C01B39/48—Other types characterised by their X-ray diffraction pattern and their defined composition using at least one organic template directing agent
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
- B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
- B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
- B01J29/74—Noble metals
- B01J29/7461—MRE-type, e.g. ZSM-48
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- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/026—After-treatment
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- C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
- 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
- C07C5/277—Catalytic processes
- C07C5/2775—Catalytic processes with crystalline alumino-silicates, e.g. molecular sieves
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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
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- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/14—Pore volume
Abstract
The invention discloses a preparation method of a hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree, which comprises the following steps: (1) Uniformly mixing alkali liquor, a structure directing agent solution, a silicon source, an aluminum source and water, and crystallizing at 150-170 ℃ for 1-5 days; (2) Separating the product to obtain a solid, washing to be neutral, and drying at 100-120 ℃; (3) pre-calcining the solid; (4) Alkali treatment is carried out on the solid, and then ammonium ion exchange is carried out; (5) Calcining the material for a period of time to obtain the hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree. The invention also discloses the hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree and the application of the molecular sieve in hydroisomerization reaction of long-chain normal alkane.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to a hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree, a preparation method and application.
Background
The normal alkane hydroisomerization catalyst is generally a bifunctional catalyst, and the molecular sieve is used as a carrier and provides an acidic site to load noble metals for hydrogenation and dehydrogenation. For normal alkane hydroisomerization reactions, too strong an acidity of the support may promote cracking, while too weak an acidity may significantly reduce the activity of the catalyst. Thus, the normal alkane hydroisomerization catalyst requires a suitable acidity.
Patent US 10618816 discloses a method for preparing an improved ZSM-48 molecular sieve. The ZSM-48 molecular sieve obtained by adjusting the proportion of the raw materials has the characteristics of low impurity crystal, high polytype 6 ratio and small crystal grain, and has good selectivity for hydroisomerization reaction of the n-hexadecane. Patent CN 106458615 discloses a method for obtaining an SSZ-95 molecular sieve by carrying out partial removal of a structure directing agent on the basis of the molecular sieve SSZ-32; the SSZ-95 molecular sieve has unique acid site density, and compared with SSZ-32, the SSZ-95 molecular sieve has higher isomerism selectivity and generates less pyrolysis gas.
Molecular sieve of the MRE structure type has one-dimensional parallel straight pore canal with the pore size of 0.56nm multiplied by 0.56nm, and the pore canal features are suitable for hydroisomerization reaction of long-chain normal alkane and have higher selectivity to isomerism products. The molecular sieve catalyst with the MRE structure has relatively moderate acidity and micropore canals, thus having higher isomerism selectivity; however, a part of strong acid sites are inevitably present at the same time, so that further cracking of the isomerised product is induced to generate a cracking product; although microporous channels facilitate product shape selection, they do not facilitate diffusion of the reaction product. Therefore, in order to further increase the isomerism selectivity and isomerism yield of the catalyst, reduce the cracking rate, it is necessary to reduce the number of strong acid sites on the molecular sieve and to create hierarchical pores more favorable for product diffusion.
Disclosure of Invention
The present invention prepares hierarchical pore MRE molecular sieve with adjustable pore acid distribution through pre-calcining at certain temperature for certain period of time, regulating the distribution of exchangeable ions, such as alkali metal ions, exposed in pore canal, alkali treatment, ammonium ion exchange and other steps. The method is used for hydroisomerization reaction of long-chain normal alkane, and can reduce the cracking rate and improve the isomerism selectivity.
The technical scheme of the invention is as follows:
the first aspect of the invention discloses a method for preparing a hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree, which comprises the following steps:
(1) Uniformly mixing alkali liquor, a structure directing agent solution, a silicon source, an aluminum source and water, and crystallizing at 150-170 ℃ for 1-5 days;
(2) Separating the crystallized product from the step (1) to obtain a solid, washing to be neutral, and drying at 100-120 ℃;
(3) Pre-calcining the solid obtained in the step (2);
(4) Performing alkali treatment on the solid obtained in the step (3), and then performing ammonium ion exchange;
(5) Calcining the material obtained in the step (4) for a period of time to obtain the hierarchical pore-size MRE molecular sieve with adjustable pore acid distribution.
Preferably, the temperature of the pre-calcination in step (3) is 150-550 ℃.
Preferably, the aluminum source in the step (1) is one or more of aluminum sulfate octadecanoate, sodium metaaluminate or aluminum sol, the silicon source is one or more of silica sol, silica aerosol, tetraethyl orthosilicate or sodium silicate, the structure directing agent is hexamethyl ammonium bromide, and the alkali liquor is aqueous solution of NaOH or KOH; the molar ratio of the raw materials is as follows:
| Range | |
| SiO 2 /Al 2 O 3 | 130-200 |
| H 2 O/SiO 2 | 30-60 |
| OH - /SiO 2 | 0.2-0.3 |
| Q/SiO 2 | 0.05-0.15 |
wherein Q represents a structure directing agent.
Preferably, the alkali treatment in the step (4) uses aqueous solution of NaOH or KOH, and the molar concentration is 0.3-1.0 mol/L; the alkali treatment conditions are as follows: according to the mass ratio of alkali liquor to solid being 8-12, reflux is carried out for 0.5-2 h at 65-90 ℃.
Preferably, the ammonium ion exchange of step (4) uses a soluble ammonium salt, wherein the molar concentration of ammonium ions is 0.8 to 1.2mol/L; the amount of the soluble ammonium salt of the ammonium ion exchange is 1: (5-15), preferably 1:10; the ammonium ion exchange is carried out a plurality of times, preferably three times.
Preferably, the calcination temperature in step (5) is 500-600 ℃ and the time is 2-6 h.
The second aspect of the invention discloses a hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree prepared by the preparation method.
In a third aspect, the invention discloses the use of the hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree for hydroisomerization reaction of long-chain normal paraffins.
The preparation method comprises the following specific steps:
sequentially adding water, alkali liquor, structure directing agent solution, silicon source and aluminum source into a crystallization kettle, stirring uniformly, and crystallizing at 160deg.C for 2 days. The product is washed to neutrality, centrifuged or suction filtered and dried at 120 ℃. Pre-calcining the crystallized product in a muffle furnace for a period of time, and regulating the distribution degree of exchangeable ions (alkali metal ions) exposed by the pore canal, wherein the pre-calcining temperature is a certain temperature within the range of 150-550 ℃; alkali treatment is carried out according to the mass ratio of alkali liquor to molecular sieve of 10, the molecular sieve is dispersed in 0.3-1.0 mol/L alkali liquor, reflux is carried out for 0.5-2 h at 65-90 ℃, and drying is carried out at 100-120 ℃; then carrying out ammonium ion exchange, adopting 0.8-1.2 mol/L ammonium ion aqueous solution, and carrying out three times of ion exchange steps according to the solid-to-liquid ratio of 1:10 so as to ensure that the ion exchange is complete. Finally roasting in a muffle furnace for 2-6H at 500-600 ℃ to obtain the H-shaped hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree.
The mol ratio range of the reaction raw materials is as follows:
| Range | |
| SiO 2 /Al 2 O 3 | 130-200 |
| H 2 O/SiO 2 | 30-60 |
| OH - /SiO 2 | 0.2-0.3 |
| Q/SiO 2 | 0.05-0.15 |
wherein Q represents a structure directing agent.
Wherein the aluminum source is: aluminum sulfate octadecatriend, sodium metaaluminate, aluminum sol, etc.
Wherein the silicon source is: siO (SiO) 2 Silica aerosols (AS-30, AS-40, etc.) having a content of 30% to 40% include vapor phase process silica aerosols, precipitation process silica aerosols, etc., tetraethyl orthosilicate (TEOS), sodium silicate, etc.
Wherein OH is - The method comprises the following steps: naOH or KOH aqueous solution, the molar concentration is 0.8-1.2 mol/L.
Wherein the structure directing agent is hexamethylammonium bromide.
Wherein the water is distilled water.
Wherein the alkali liquor in the alkali treatment process is as follows: naOH or KOH aqueous solution, and the molar concentration is 0.3-1.0 mol/L. The alkali treatment conditions are as follows: reflux is carried out for 0.5 to 2 hours at the temperature of 65 to 90 ℃.
Wherein the ammonium ion aqueous solution is: ammonium nitrate or ammonium chloride solution with the molar concentration of 0.8-1.2 mol/L.
The invention has the beneficial effects that:
1. the method of the invention obtains hydrogen form MR through the steps of pre-calcination, alkali treatment process, ammonium ion exchange and the likeE structure molecular sieves, i.e. the alkali metal ions in the molecular sieve are wholly or partly changed to H + Ionic molecular sieve with MRE structure. Wherein the alkali metal ion is from alkali liquor, silicon source or aluminum source. The method of the invention removes all or part of the structure directing agent by adjusting the pre-calcination temperature of the molecular sieve, thereby adjusting the distribution length of exchangeable ion alkali metal ions exposed by the pore canal, and finally obtaining all or part of H + Ionic molecular sieve with MRE structure. The structure guiding agent is generally removed when the precalcination temperature is 150 ℃, and the more the structure guiding agent is removed along with the rising of the precalcination temperature, the structure guiding agent can be completely removed when the precalcination temperature is about 550 ℃, micropore channels are completely unobstructed, alkali metal ions in the channels are completely exposed, and NH can be used for removing the alkali metal ions 4+ Ion exchange is completed, and all the ions are changed into H + Ionic molecular sieve with MRE structure. If the precalcination is carried out at a lower temperature (between 150 and 550 ℃), part of the structure directing agent is removed, part of the alkali metal ions in the microporous channels are blocked by the structure directing agent which is not removed, and the alkali metal ions cannot be blocked by NH 4+ Ion exchange is carried out completely, and part of the ion exchange is finally changed into H + Ionic molecular sieve with MRE structure. The method of the invention adjusts the distribution length of alkali metal ions exposed by the pore canal through the control of the precalcination temperature, thereby obtaining the complete or partial conversion into H + Ionic MRE structure molecular sieve, i.e. one with adjustable pore acid distribution.
2. The method of the invention uses alkali liquor to carry out post-treatment on the pre-calcined product and then carries out ammonium ion exchange. The exchangeable ion distribution determines the exchange degree of ammonium ions, and the alkali treatment desilication not only can generate intragranular mesopores to form a mesoporous and microporous graded MRE molecular sieve, but also can reduce aluminum sites which are partially combined with silicon, and further reduce the number of formable protonic acid sites; and then carrying out secondary calcination to enable the pore canal of the molecular sieve to be completely opened, and finally obtaining the mesoporous and microporous graded MRE molecular sieve with adjustable pore canal acid distribution degree.
3. The mesoporous and microporous graded MRE molecular sieve of the invention is loaded with noble metal platinum, and can be used for hydroisomerization reaction of long-chain n-alkane through roasting, reduction and other processes. The hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree is used in hydroisomerization reaction of long-chain normal alkane, and has low cracking rate, high selectivity and high yield of isomerised product, and the molar ratio of single branched product to multiple branched product in the product is obviously raised.
4. The method of the invention allows the activity to be reduced to a certain extent by adjusting the acidity of the molecular sieve in the post-treatment process, so that the acidity is more suitable for hydroisomerization reaction of normal alkane, and the selectivity of the isomerised product is improved.
Detailed Description
The invention will now be described in detail with reference to a few specific embodiments thereof. These examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. The embodiments in the examples are only preferred embodiments, but the present invention is not limited to the preferred embodiments.
Example 1: the precalcination temperature is 550 ℃.
1600g of deionized water and 90g of sodium hydroxide are weighed and added into a reactor, and are stirred uniformly; adding 200g of silica aerosol, 100g of hexamethylammonium bromide and 736g of aluminum sulfate octadecanoate solution into the alkaline solution, and uniformly stirring; the reactant gel is put into a reaction kettle for sealing, and crystallized for 48 hours under the autogenous pressure of 160 ℃.
Taking out the crystallized product, cooling, centrifugally separating, washing with deionized water to be neutral, and drying in a baking oven at 120 ℃.
Then, it was placed in a muffle furnace and pre-calcined at 550℃for 3 hours.
Then dispersing the powder in 0.5mol/L sodium hydroxide aqueous solution with the liquid-solid ratio of 10, refluxing for 1h at 80 ℃, filtering and drying in a 120 ℃ oven; then, ion exchange was carried out three times with a solid-to-liquid ratio of 1:10 using a 1.0mol/L ammonium chloride solution.
Finally, the powder is baked for 4 hours at 550 ℃ to convert the molecular sieve into a hydrogen form.
Example 2: the precalcination temperature is 400 ℃.
The conditions and procedure were the same as in example 1, except that the precalcination temperature was 400 ℃.
Example 3: the precalcination temperature was 250 ℃.
The conditions and procedure were the same as in example 1, except that the precalcination temperature was 250 ℃.
Example 4: the precalcination temperature is 150 ℃.
The conditions and procedure were the same as in example 1, except that the precalcination temperature was 150 ℃.
Example 5: the pre-calcination temperature is 400 ℃, and the alkali treatment condition is changed.
The conditions and steps were the same as in example 2; however, the concentration of sodium hydroxide in the alkali treatment was 1.0mol/L, the liquid-solid ratio was 10, and the mixture was refluxed at 65℃for 1 hour.
Example 6: the precalcination temperature is 150 ℃, and the alkali treatment condition is changed.
The conditions and procedure were the same as in example 4; however, the concentration of sodium hydroxide in the alkali treatment was 0.3mol/L, the liquid-solid ratio was 12, and the mixture was refluxed at 90℃for 2 hours.
Comparative example 1: no pre-calcination was performed.
The conditions and steps were the same as in example 1; but without pre-calcination.
Comparative example 2: the precalcination completely removes the structure directing agent, but does not undergo alkali treatment.
The conditions and steps were the same as in example 1; however, the structure directing agent was completely removed by pre-calcination at a pre-calcination temperature of 595 ℃ for 3 hours, but without alkali treatment, the tertiary ammonium ion exchange was directly performed.
Comparative example 3: the precalcination portion removes the structure directing agent but does not undergo alkali treatment.
The conditions and steps were the same as in example 2; calcining at 400 ℃ for 3 hours, partially removing the structure directing agent, but directly carrying out tertiary ammonium ion exchange without alkali treatment.
The parameters of the microporous acid distribution degree, specific surface area, pore volume and the like of the molecular sieve finished products obtained in examples 1-6 and comparative examples 1-3 are shown in Table 1. As can be seen from table 1, the pore acid distribution degree of the molecular sieve finished product of different embodiments is adjustable, and the mesoporous volume is increased after alkali treatment. The molecular sieve finished products of examples 1-6 and comparative examples 1-3 differ in mesoporous volume, external surface area, and acid distribution, and in particular, the acid distribution can be adjusted by controlling the pre-calcination temperature.
As can be seen from table 1, the microporous acid distribution degree of the molecular sieve product obtained without pre-calcination was zero (comparative example 1), and the microporous acid distribution degree could not be adjusted.
The high-temperature precalcination leads the structure directing agent to be completely removed, the micropore duct is completely unobstructed, and the distribution degree of the micropore acid is 100 percent. If the alkali treatment is not carried out and then the three times of ammonium ion exchange are directly carried out, only partial mesopores (mesopore volume of 0.16cm 3 (g) no intramolecular mesopores, no formation of mesoporous and microporous classified onium MRE molecular sieves (comparative example 2); if the alkali treatment is carried out and then three times of ammonium ion exchange are carried out, the mesoporous volume is 0.26cm 3 /g, increased mesoporous volume 0.10cm 3 /g(0.26-0.16cm 3 And/g) is the volume of the mesopores in the crystal, obtaining the molecular sieve of the onium MRE (example 1) with the classification of mesopores and micropores.
Precalcining at 400 ℃ for 3 hours, partially removing the guiding agent, partially exposing alkali metal ions in the pore canal, and enabling the alkali metal ions to be NH 4+ Ion exchange to obtain microporous molecular sieve with microporous acid distribution degree of 54% and mesoporous volume of 0.23cm after alkali treatment 3 /g, increased mesoporous volume 0.09cm 3 /g(0.23-0.14cm 3 /g) is the intra-crystalline mesoporous volume (example 2); if the ammonium ion exchange is directly carried out three times without alkali treatment, only a part of mesopores (mesopore volume of 0.14cm 3 Per g), no intramolecular mesopores, no mesoporous and microporous classified onium MRE molecular sieves could be formed (comparative example 3).
TABLE 1 acid distribution, specific surface area and pore volume of different products
Example 7: hydroisomerization of n-hexadecane
The samples of the hierarchical pore MRE molecular sieves obtained in examples 1-6 and comparative examples 1-3 were extruded using an adhesiveThen, the noble metal platinum is loaded by adopting an isovolumetric impregnation method and is applied to the hydroisomerization reaction of the n-hexadecane. The platinum loading is 0.3-0.5wt%. After which the mixture was treated in a muffle furnace at 450℃for 4h. The catalyst was packed in a micro fixed bed reactor, both ends being filled with silicon carbide. Just before the hydroisomerization reaction starts, the reaction is reduced for 4 hours at 400 ℃ under a hydrogen atmosphere. The conditions for the hydroisomerization reaction are: pressure 3MPa, airspeed 2h -1 Hydrogen-oil ratio 1000 and temperature 270-330 deg.c.
The conversion, isomerization rate, isomerization selectivity, and molar ratio of single-branched product to multi-branched product of the catalysts obtained in examples 1 to 6 and comparative examples 1 to 3 are shown in Table 2.
As can be seen from Table 2, the cracking rates (i.e. < C) of the catalysts of examples 1 to 6 relative to comparative examples 1 to 3 at the respective optimal isomerization reaction temperatures, i.e., the reaction temperatures at which each catalyst reached the highest isomerization rates, respectively 15 Per wt% ") is significantly reduced by up to 49.7% [ 11.91-5.99/11.91 ]]100% = 49.7% >; the isomerism yield (namely 'C16/wt%') and isomerism selectivity are obviously improved, and the isomerism selectivity can be improved by 7.28 percent at the highest (93.40-87.06/87.06)]100% = 7.28% >; the molar ratio of the single branched product to the multi-branched product can be increased by 83.73 percent (4.36-2.42/2.42)]100% = 80.17% >. The catalysts obtained in comparative examples 1-3 have higher cracking rate, obviously poorer isomerism yield and isomerism selectivity, and lower mole ratio of single branched products to multi branched products.
Table 2 comparison of catalytic performance results
| Sample of | Reaction temperature/. Degree.C | Conversion/% | ≤C 15 /wt％ | Isomerism C 16 /wt％ | Isomerism selectivity/% | Single/multiple |
| Comparative example 1 | 325 | 91.58 | 10.05 | 81.53 | 89.03 | 3.04 |
| Comparative example 2 | 310 | 92.01 | 11.91 | 80.10 | 87.06 | 2.52 |
| Comparative example 3 | 315 | 91.46 | 10.53 | 80.93 | 88.49 | 2.42 |
| Example 1 | 310 | 91.67 | 8.97 | 82.70 | 90.21 | 3.37 |
| Example 2 | 315 | 90.92 | 5.99 | 84.92 | 93.40 | 4.36 |
| Example 3 | 320 | 90.19 | 6.17 | 84.02 | 93.16 | 3.74 |
| Example 4 | 320 | 90.10 | 6.38 | 83.72 | 92.92 | 3.71 |
| Example 5 | 315 | 90.32 | 6.03 | 84.29 | 93.32 | 4.24 |
| Example 6 | 320 | 90.21 | 6.00 | 84.21 | 93.35 | 4.15 |
[ MEANS FOR SOLVING ] C in Table 1 15 Weight percent represents the total mass fraction of the substance having 15 or less carbon atoms in the product; "isomerism C 16 Wt% represents the total mass fraction of n-hexadecane isomer in the product; "isomerism selectivity/%" means the percentage of the reactant that selectively produces the n-hexadecane isomer; "Single/multiple" means the molar ratio of single branched products to multiple branched products in the product.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. The preparation method of the hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree is characterized by comprising the following steps:
(1) Uniformly mixing alkali liquor, a structure directing agent solution, a silicon source, an aluminum source and water, and crystallizing at 150-170 ℃ for 1-5 days;
(2) Separating the crystallized product from the step (1) to obtain a solid, washing to be neutral, and drying at 100-120 ℃;
(3) Pre-calcining the solid obtained in the step (2); the temperature of the pre-calcination is 150-550 ℃;
(4) Performing alkali treatment on the solid obtained in the step (3), and then performing ammonium ion exchange;
(5) Calcining the substance obtained in the step (4) for a period of time to obtain the hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree; the calcination temperature is 500-600 ℃ and the time is 2-6 h;
the aluminum source in the step (1) is one or more of aluminum sulfate octadecanoate, sodium metaaluminate or aluminum sol, the silicon source is one or more of silicon sol, silicon aerosol, tetraethyl orthosilicate or sodium silicate, the structure directing agent is hexamethyl ammonium bromide, and the alkali liquor is aqueous solution of NaOH or KOH; the molar ratio of the raw materials is as follows:
；
wherein Q represents a structure directing agent.
2. The process according to claim 1, wherein the alkali treatment in the step (4) uses an aqueous solution of NaOH or KOH at a molar concentration of 0.3 to 1.0mol/L; the alkali treatment conditions are as follows: according to the mass ratio of alkali liquor to solid being 8-12, reflux is carried out at 65-90 ℃ for 0.5-2 h.
3. The process according to claim 1, wherein the ammonium ion exchange in step (4) uses a soluble ammonium salt in which the molar concentration of ammonium ions is 0.8 to 1.2mol/L; the amount of the soluble ammonium salt is 1:5-15.
4. A hierarchical pore MRE molecular sieve with adjustable pore acid distribution degree prepared by the preparation method according to any one of claims 1-3.
5. Use of a hierarchical pore MRE molecular sieve with adjustable pore acid distribution according to claim 4 for hydroisomerization of long chain n-alkanes.
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| CN112978749A (en) * | 2019-12-02 | 2021-06-18 | 中国石油天然气股份有限公司 | Preparation method and application of multi-stage-hole SSZ-13 molecular sieve and method for preparing olefin from methanol |
| CN113620309A (en) * | 2020-05-09 | 2021-11-09 | 中国石油化工股份有限公司 | ZSM-48 molecular sieve and synthesis method and application thereof |
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| CN112978749A (en) * | 2019-12-02 | 2021-06-18 | 中国石油天然气股份有限公司 | Preparation method and application of multi-stage-hole SSZ-13 molecular sieve and method for preparing olefin from methanol |
| CN113620309A (en) * | 2020-05-09 | 2021-11-09 | 中国石油化工股份有限公司 | ZSM-48 molecular sieve and synthesis method and application thereof |
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