Beta molecular sieve catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts and provides a Beta molecular sieve catalyst as well as a preparation method and application thereof. The Beta molecular sieve catalyst comprises a Beta molecular sieve and an optional Y-type molecular sieve; the total content of the Beta molecular sieve and the Y-type molecular sieve in the catalyst is greater than 94wt%, and the molar ratio of silicon dioxide to aluminum oxide in the Beta molecular sieve and the Y-type molecular sieve is 5-50. The Beta molecular sieve catalyst provided by the invention is prepared by adopting the Y-type molecular sieve and the Beta molecular sieve as raw materials, has good mechanical strength, and has the characteristics of high activity and good stability when being used in transalkylation reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and more specifically to a Beta molecular sieve catalyst and a preparation method and application thereof. Background Art

[0002] Beta molecular sieve and Y molecular sieve have the same chemical element composition (silicon oxide and aluminum oxide) and 12-membered ring channel system, but have different structural units and topological structures, and will show different characteristics in catalytic reactions. Both Beta molecular sieve and Y molecular sieve can be used for transalkylation reactions. When a single Beta molecular sieve is used, it has good stability because there is no supercage in its pores; however, the silicon-aluminum ratio of Beta molecular sieve is relatively high, requiring a higher reaction temperature; and the crystals of Beta molecular sieve are relatively small among known molecular sieves, generally less than 100 nanometers, and it is difficult to recover them using conventional kettle hydrothermal crystallization synthesis; at the same time, the catalyst prepared by Beta molecular sieve has the disadvantages of poor strength, easy powder loss, and high wear rate. When a single Y molecular sieve is used, because the Y molecular sieve has a relatively low silicon-aluminum ratio, the pore system is relatively smooth and developed, the acid content is relatively large, and it has a higher catalytic activity in the transalkylation reaction, which can be suitable for a lower reaction temperature, but the pores of the Y molecular sieve contain supercages, and a small amount of heavy components produced during the reaction will be deposited here, resulting in poor activity stability.

[0003] In addition, both Beta molecular sieve and Y molecular sieve crystals are nano-scale powder particles, which are not sticky in themselves. When used as industrial catalysts, additional binders need to be added to shape them so that they can meet the requirements of loading, separation, unloading and replacement in the chemical production process. Binders are usually aluminum oxide, silicon oxide, etc. and their mixtures, which are generally chemically inert substances under chemical reaction conditions. On the one hand, the presence of binders will block the micropores of molecular sieve crystals and reduce the diffusion properties of reactants and products, thereby reducing the reaction activity and stability of the catalyst; on the other hand, the presence of binders will also cover the active sites on the surface of the molecular sieve crystals, causing the loss of active sites and reducing the utilization rate of the catalyst.

[0004] Although the prior art discloses some composite molecular sieves including Beta molecular sieve and Y-type molecular sieve, they still need to be molded with a binder before they can be used as catalysts. Summary of the invention

[0005] The object of the present invention is to provide a Beta molecular sieve catalyst and a preparation method and application thereof, so as to solve the technical problems in the prior art that the molecular sieve particles are difficult to recover when synthesizing the Beta molecular sieve and the catalyst prepared by using the Beta molecular sieve has poor mechanical strength.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a Beta molecular sieve catalyst, comprising a Beta molecular sieve and an optional Y-type molecular sieve; the total content of the Beta molecular sieve and the Y-type molecular sieve in the catalyst is greater than 94wt%, and the molar ratio of silica to alumina in the Beta molecular sieve and the Y-type molecular sieve is 5-50.

[0008] The Beta molecular sieve catalyst provided by the present invention is mainly composed of Beta molecular sieve and may contain a small amount of Y-type molecular sieve, the content of which in the catalyst is 0-30wt%; it may also contain a small amount of sodium oxide and amorphous silicon dioxide, wherein the content of sodium oxide is 0-1wt% and the content of amorphous silicon dioxide is 0-5wt%.

[0009] According to some embodiments of the present invention, the BET surface area of ​​the catalyst is greater than 520 m 2 g -1 , the ratio of the surface area to the BET surface area is less than 0.3, and the micropore volume is greater than 0.2 cm 3 g -1 , crushing strength>90N / cm.

[0010] According to some embodiments of the present invention, the BET surface area of ​​the catalyst is 530 to 600 m 2 g -1 .

[0011] According to some embodiments of the present invention, the BET surface area of ​​the catalyst is 540 to 570 m 2 g -1 .

[0012] According to some embodiments of the present invention, the ratio of the external surface area to the BET surface area of ​​the catalyst is 0.1 to 0.28.

[0013] According to some embodiments of the present invention, the micropore volume of the catalyst is 0.21-0.3 cm 3 g -1 .

[0014] According to some embodiments of the present invention, the micropore volume of the catalyst is 0.22 to 0.25 cm 3 g -1 .

[0015] According to some embodiments of the present invention, the catalyst has a crushing strength of 100 to 150 N / cm.

[0016] According to some embodiments of the present invention, the catalyst has a crushing strength of 110 to 130 N / cm.

[0017] According to some embodiments of the present invention, the mesopore volume of the catalyst is less than 0.4 cm 3 g -1 .

[0018] According to some embodiments of the present invention, the mesopore volume of the catalyst is 0.1 to 0.3 cm 3 g -1 .

[0019] According to some embodiments of the present invention, the average pore size of the catalyst is less than 6 nm.

[0020] According to some embodiments of the present invention, the average pore diameter of the catalyst is 1 to 5 nm.

[0021] According to some embodiments of the present invention, the average pore diameter of the catalyst is 2 to 4 nm.

[0022] In a second aspect, the present invention provides a method for preparing the catalyst according to the first aspect, comprising:

[0023] S1. A colloidal material comprising a molecular sieve raw powder, a silicon source, an aluminum source, an alkali source, and a molding aid is obtained, and then formed into colloidal particles; the molecular sieve raw powder comprises a Y-type molecular sieve raw powder and a Beta molecular sieve raw powder;

[0024] S2. The colloidal particles are subjected to hydrothermal crystallization treatment in the presence of a template, and calcined to obtain a molecular sieve solid;

[0025] S3. subjecting the molecular sieve solid to ion exchange and water vapor treatment to obtain the catalyst.

[0026] According to some embodiments of the present invention, the amounts of the components used to obtain the colloidal material are:

[0027] Molecular sieve powder: 20-80 parts by weight;

[0028] Silicon source: 10-80 parts by weight;

[0029] Aluminum source: 0.1-15 parts by weight;

[0030] Alkali source: 0.1-10 parts by weight;

[0031] Molding aid: 0.1-5 parts by weight;

[0032] The weight ratio of the Y-type molecular sieve raw powder to the Beta molecular sieve raw powder in the molecular sieve raw powder is (10-50): (10-30).

[0033] In the present invention, the amount of each component is measured based on the dry weight of the component.

[0034] According to some embodiments of the present invention, the amounts of the components used to obtain the colloidal material are:

[0035] Molecular sieve powder: 20-50 parts by weight;

[0036] Silicon source: 10-40 parts by weight;

[0037] Aluminum source: 1 to 10 parts by weight;

[0038] Alkali source: 1-5 parts by weight;

[0039] Molding aid: 1 to 5 parts by weight.

[0040] According to some embodiments of the present invention, the Y-type molecular sieve raw powder has a molar ratio of silicon dioxide to aluminum oxide greater than 20, and a sodium content less than 1 wt%.

[0041] According to some embodiments of the present invention, the molar ratio of silicon dioxide to aluminum oxide in the Beta molecular sieve raw powder is 5-50.

[0042] According to some embodiments of the present invention, the silicon source includes at least one of silica sol, white carbon black, and tetraethyl orthosilicate.

[0043] According to some embodiments of the present invention, the aluminum source includes at least one of sodium aluminate, aluminum sulfate, aluminum sol, and aluminum oxide.

[0044] According to some embodiments of the present invention, the alkali source includes an organic amine template, preferably at least one of tetraethylammonium hydroxide, tetraethylammonium iodide, tetraethylammonium bromide, and tetraethylammonium chloride.

[0045] According to some embodiments of the present invention, the molding aid includes at least one of plant gum (such as cellulose, sesbania gum, guar gum, sesame gum, fenugreek gum, etc.), food gum (such as gelatin, sodium caseinate, gum arabic, tamarind polysaccharide gum, agar, sodium alginate, carrageenan, pectin, xanthan gum, β-cyclodextrin, sodium carboxymethyl cellulose, sodium carboxymethyl starch, sodium starch phosphate, hydroxypropyl starch, propylene glycol alginate, etc.), and starch.

[0046] According to some embodiments of the present invention, the template comprises an organic amine template.

[0047] According to some embodiments of the present invention, the template includes at least one of tetraethylammonium hydroxide, tetraethylammonium iodide, tetraethylammonium bromide, and tetraethylammonium chloride.

[0048] In the preparation method provided by the present invention, operations such as molding, hydrothermal crystallization, calcination, ion exchange, steam treatment, etc. can all adopt conventional methods in the prior art, and the present invention has no particular limitation thereto.

[0049] According to some embodiments of the present invention, the hydrothermal crystallization temperature is 120-190° C., and the time is 1-5 days.

[0050] According to some embodiments of the present invention, the template is a template aqueous solution with a concentration of 5 to 20 wt%.

[0051] According to some embodiments of the present invention, the calcination temperature is 400-600° C. and the calcination time is 1-10 h.

[0052] According to some embodiments of the present invention, the ion exchange comprises: treating with an ammonium salt solution having a concentration of 1 to 20 wt % at 0 to 100° C. for 0.5 to 24 h.

[0053] According to some embodiments of the present invention, the ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride, ammonium oxalate, ammonium acetate, ammonium sulfate, and ammonium citrate.

[0054] According to some embodiments of the present invention, the ion exchange is repeated 1 to 5 times.

[0055] According to some embodiments of the present invention, the steam treatment comprises: performing steam treatment at 400-800°C in an atmosphere containing 10-100 vol% steam for 0.5-24 h, with a weight space velocity of steam and catalyst of 1-10 h －1 .

[0056] In a third aspect, the present invention provides use of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in a transalkylation reaction of polyalkylbenzenes.

[0057] According to some embodiments of the present invention, the alkyl group includes C1 to C 10 The alkyl group is preferably at least one of ethyl, propyl, butyl, pentyl and hexyl.

[0058] According to some embodiments of the present invention, the transalkylation reaction of the polyalkylbenzenes comprises reacting diethylbenzene with benzene to produce ethylbenzene.

[0059] The beneficial effects of the present invention are at least:

[0060] The Beta molecular sieve catalyst provided by the present invention is prepared by using Y-type molecular sieve and Beta molecular sieve as raw materials, has good mechanical strength, and has the characteristics of high activity and good stability when used in transalkylation reaction. DETAILED DESCRIPTION

[0061] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent in detail and do not limit the scope of protection of the present invention in any way.

[0062] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0063] Embodiments 1 to 4

[0064] USY molecular sieve (SiO2 / Al2O3 molar ratio of 23, sodium content of 0.05wt%), Beta molecular sieve (SiO2 / Al2O3 molar ratio of 25), silica sol, sodium aluminate, tetraethylammonium bromide, cellulose are added to the mixer and mixed for 30 minutes. The amount of each component is shown in Table 1. Then put it in a kneader, add an appropriate amount of deionized water, wet mix it into a material with appropriate humidity, extrude it, shape it, and dry it in an oven at 110℃. Then put it in a pressure-resistant container for hydrothermal crystallization treatment. The treatment temperature is shown in Table 1. The treatment time is 48h. A tetraethylammonium hydroxide solution with a concentration of 10wt% is configured in the pressure-resistant container. After taking it out, wash it twice with deionized water, dry it, and roast it at 500℃ for 2h. Then put it into a 5wt% ammonium nitrate solution for ion exchange, stir it at 90℃ for 4h, centrifuge it, and wash it twice with deionized water. Repeat the above ion exchange process 4 times. Then, the catalyst was treated at 550°C for 2 h in a 100% steam atmosphere with a weight space velocity of 1 h -1 , to obtain a catalyst.

[0065] Table 1

[0066]

[0067] Example 5

[0068] The catalyst preparation method refers to Example 1, except that the Y-type molecular sieve is replaced by another Y-type molecular sieve with a SiO2 / Al2O3 molar ratio of 5.3 and a sodium content of 13 wt%.

[0069] Example 6

[0070] The catalyst preparation method refers to Example 1, with the only difference being that the Y-type molecular sieve is replaced by another Y-type molecular sieve with a SiO2 / Al2O3 molar ratio of 7.8 and a sodium content of 1.8 wt%.

[0071] Comparative Example 1

[0072] Weigh 20g of USY molecular sieve (SiO2 / Al2O3 molar ratio of 23, sodium content of 0.05wt%), 20g of Beta molecular sieve (SiO2 / Al2O3 molar ratio of 25) and 65.75g of silica sol (40wt%), mix them with alumina in a dry weight ratio of 80:20, extrude into strips, and then dry and calcine.

[0073] The catalyst was then washed twice with deionized water, dried, and calcined at 500°C for 2 hours. The catalyst was then placed in a 5wt% ammonium nitrate solution for ion exchange, stirred at 90°C for 4 hours, centrifuged, and washed twice with deionized water. The above ion exchange process was repeated 4 times. The catalyst was then treated at 550°C in a 100% steam atmosphere for 2 hours to obtain the catalyst.

[0074] Comparative Example 2

[0075] The catalyst preparation method refers to Example 1, except that 20 g of USY molecular sieve and 20 g of Beta molecular sieve are replaced by 40 g of USY molecular sieve.

[0076] Comparative Example 3

[0077] The catalyst preparation method refers to Example 1, except that 20 g of USY molecular sieve and 20 g of Beta molecular sieve are replaced by 40 g of Beta molecular sieve.

[0078] Performance Evaluation

[0079] (I) Catalyst composition

[0080] Test method:

[0081] (1) Total content of Beta molecular sieve and Y molecular sieve in the catalyst: D8ADVANCE Bruker X-ray diffractometer, Cu target, 2Theta angle range: 5-50°, is used to analyze the crystal structure and relative crystallinity of Beta molecular sieve and Y molecular sieve. Y molecular sieve is a molecular sieve with an octahedral structure, and its XRD characteristic peaks are mainly 6.24, 10.16, 11.90, 15.70, 18.73, 20.41, 23.82, 31.43, and 34.00. Beta molecular sieve is a molecular sieve with a BEA structure, and its XRD characteristic peaks mainly include peaks at 6.0, 7.0, 8.0, 11.6, 12.0, 14.5, 19.0, 23.0, and 28.0°. By analyzing the ratio of the sum of the characteristic peak heights of the standard sample and the test sample, it can be used to measure the total content of Beta molecular sieve and Y molecular sieve in the catalyst.

[0082] (2) The molar ratio of silicon dioxide to aluminum oxide (SiO2 / Al2O3) in Beta and Y molecular sieves: The contents of Si, Al and other elements in the samples were tested using Varian 725ES inductively coupled plasma atomic emission spectrometry (ICP-AES) from Varian Corporation of the United States and the SiO2 / Al2O3 ratio was calculated.

[0083] The test results are shown in Table 2.

[0084] Table 2 Catalyst composition

[0085]

[0086]

[0087] (II) Catalyst pore structure data

[0088] Test method: The specific surface area was measured using a Micromeritics TriStar-3000 physical adsorption instrument, with N2 as the adsorbent and an adsorption temperature of 7.7 K. Before the test, the sample was heated to 7 × 10 -2 Pa, vacuum activation at 350℃ for more than 10h. The specific surface area was calculated by BET method, the surface area was calculated by t-Plot, the micropore distribution was processed by HKSF method, and the mesopore distribution was calculated by BJH method.

[0089] The test results are shown in Table 3.

[0090] Table 3 Pore structure data of catalysts

[0091]

[0092]

[0093] Among them, S BET is the specific surface area; S exter is the surface area; V micro is the micropore volume; V meso is the mesoporous volume; PoreDiameter is the average diameter of the pores (average pore size).

[0094] It can be seen from the test results in Table 3 that the catalyst provided by the present invention has the characteristics of large specific surface area and large micropore volume.

[0095] (III) Evaluation of initial catalyst activity

[0096] The catalyst reaction performance was investigated using a bottom-up fixed bed reactor, which was a stainless steel tube with an inner diameter of 28 mm and a length of 800 mm. The catalyst loading was 3 g and diluted to 10 mL with glass beads.

[0097] After the catalysts of the examples and comparative examples were loaded into the reactor, the catalysts were activated under nitrogen protection at 400°C for 1 hour. Then the reactor was cooled to below 40°C, the nitrogen purge was stopped, the transalkylation material was introduced, and the temperature was raised to the reaction temperature after the pressure reached the set value.

[0098] The reaction conditions are: temperature 230°C, pressure 3.0 MPa, total liquid phase space velocity 1.5 h -1 , the weight ratio of benzene to diethylbenzene is 3:1 (petroleum benzene is used as raw material). After the system is stable, the liquid product is taken regularly for chromatographic analysis. The stable data of feeding for 10 hours is shown in Table 4.

[0099] The following calculation formula is used for transalkylation reaction data processing:

[0100] Diethylbenzene conversion rate = (1-diethylbenzene mass fraction in product / diethylbenzene mass fraction in raw material) × 100%;

[0101] Ethylbenzene selectivity = amount of ethylbenzene produced / (amount of benzene reacted + amount of diethylbenzene produced) × 100%;

[0102] Table 4

[0103]

[0104] The particle strength of the catalyst is defined as the pressure that each centimeter of the catalyst particle withstands when it is broken, that is, Newton / centimeter (N / cm).

[0105] It can be seen from the test results in Table 4 that the catalyst provided by the present invention has higher catalytic activity and mechanical strength.

[0106] (IV) Catalyst activity and stability evaluation

[0107] The catalyst reaction performance was investigated using a bottom-up fixed bed reactor, which was a stainless steel tube with an inner diameter of 28 mm and a length of 800 mm. The catalyst loading was 3 g and diluted to 10 mL with glass beads.

[0108] After the catalysts of the examples and comparative examples were loaded into the reactor, the catalysts were activated under nitrogen protection at 400°C for 1 hour. Then the reactor was cooled to below 40°C, the nitrogen purge was stopped, the transalkylation material was introduced, and the temperature was raised to the reaction temperature after the pressure reached the set value.

[0109] The reaction conditions are: temperature 260°C, pressure 3.0 MPa, total liquid phase space velocity 10.0 h -1 , the weight ratio of benzene to diethylbenzene is 2:1 (using hydrogenated benzene with a biphenyl content of 1.5wt% as raw material). After the system is stable, the liquid product is taken regularly for chromatographic analysis. The stable data of feeding for 10 hours is shown in Table 5.

[0110] Table 5

[0111]

[0112] It can be seen from the test results in Table 5 that the catalyst provided by the present invention has better activity; at the same time, without the covering and wrapping of the binder, the mass transfer capacity of the catalyst is improved, and the product is easier to diffuse out without accumulating and deactivating, so the activity stability is also better, and the ability to resist alkaline toxic substances is stronger.

[0113] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A Beta molecular sieve catalyst, characterized in that: The catalyst comprises Beta molecular sieve and optional Y-type molecular sieve; the total content of the Beta molecular sieve and the Y-type molecular sieve in the catalyst is greater than 94wt%, and the molar ratio of silicon dioxide to aluminum oxide in the Beta molecular sieve and the Y-type molecular sieve is 5-50.

2. The catalyst according to claim 1, characterized in that The BET surface area of ​​the catalyst is >520 m 2 g -1 , the ratio of the surface area to the BET surface area is less than 0.3, and the micropore volume is greater than 0.2 cm 3 g -1 , crushing strength>90N / cm.

3. The method for preparing the catalyst according to claim 1 or 2, characterized in that: include: S1. A colloidal material comprising a molecular sieve raw powder, a silicon source, an aluminum source, an alkali source, and a molding aid is obtained, and then formed into colloidal particles; the molecular sieve raw powder comprises a Y-type molecular sieve raw powder and a Beta molecular sieve raw powder; S2. The colloidal particles are subjected to hydrothermal crystallization treatment in the presence of a template, and calcined to obtain a molecular sieve solid; S3. subjecting the molecular sieve solid to ion exchange and water vapor treatment to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that: The amounts of the components used to obtain the colloidal material are: Molecular sieve powder: 20-80 parts by weight; Silicon source: 10-80 parts by weight; Aluminum source: 0.1-15 parts by weight; Alkali source: 0.1-10 parts by weight; Molding aid: 0.1-5 parts by weight; The weight ratio of the Y-type molecular sieve raw powder to the Beta molecular sieve raw powder in the molecular sieve raw powder is (10-50): (10-30).

5. The preparation method according to claim 3 or 4, characterized in that: The Y-type molecular sieve raw powder has a silicon dioxide to aluminum oxide molar ratio of >20 and a sodium content of <1wt%; And / or, the molar ratio of silicon dioxide to aluminum oxide in the Beta molecular sieve raw powder is 5-50.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The silicon source includes at least one of silica sol, white carbon black and tetraethyl orthosilicate; And / or, the aluminum source includes at least one of sodium aluminate, aluminum sulfate, aluminum sol, and aluminum oxide; And / or, the alkaline source comprises an organic amine template, preferably at least one of tetraethylammonium hydroxide, tetraethylammonium iodide, tetraethylammonium bromide and tetraethylammonium chloride; And / or, the molding aid includes at least one of plant gum, food gum, and starch; And / or, the template agent includes an organic amine template agent, preferably at least one of tetraethylammonium hydroxide, tetraethylammonium iodide, tetraethylammonium bromide and tetraethylammonium chloride.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The hydrothermal crystallization temperature is 120-190°C and the time is 1-5 days; And / or, the calcination temperature is 400-600° C. and the calcination time is 1-10 hours.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The ion exchange comprises: treating with an ammonium salt solution with a concentration of 1 to 20 wt% at 0 to 100° C. for 0.5 to 24 hours; Preferably, the ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride, ammonium oxalate, ammonium acetate, ammonium sulfate and ammonium citrate.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The steam treatment comprises: performing steam treatment at 400-800° C. in an atmosphere containing 10-100% steam for 0.5-24 hours, with a weight space velocity of steam and catalyst of 1-10 h －1 .

10. Use of the catalyst according to claim 1 or 2 or the catalyst prepared by the preparation method according to any one of claims 3 to 9 in the transalkylation reaction of polyalkylbenzenes; Preferably, The alkyl group includes C1~C 10 Alkyl, preferably at least one of ethyl, propyl, butyl, pentyl and hexyl; And / or, the transalkylation reaction of the polyalkylbenzenes comprises the reaction of diethylbenzene with benzene to produce ethylbenzene.

Images