Hydrogen type boron-containing MWW structure molecular sieve and preparation method thereof, methylnaphthalene / dimethylnaphthalene isomerization catalyst and isomerization method

Abstract

The invention provides a hydrogen type boron-containing MWW structure molecular sieve, a preparation method thereof, a methylnaphthalene / dimethylnaphthalene isomerization catalyst and an isomerization method. The preparation method comprises the following steps: mixing a silicon source, an aluminum source, an alkali source, a template agent and water to obtain first gel; performing primary aging on the first gel, and then adding a boron source for secondary aging to obtain second gel; carrying out hydrothermal crystallization on the second gel, and carrying out first roasting on the obtained product to obtain a boron-containing MWW structure molecular sieve; carrying out ammonium ion exchange on the boron-containing MWW structure molecular sieve, and carrying out secondary roasting on the obtained product to obtain a hydrogen-type boron-containing MWW structure molecular sieve; the boron source contains an aromatic ring structure. The hydrogen type boron-containing MWW structure molecular sieve provided by the invention has a relatively high specific surface area, and the acidity of the outer surface of the molecular sieve is reduced through the synergistic effect of means such as organic boron modification and segmented aging, so that an isomerization catalyst prepared from the molecular sieve can simultaneously meet the requirements of high activity and long service life.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve material synthesis and isomerization catalysis, specifically relating to a hydrogen-form boron-containing MWW structure molecular sieve and its preparation method, as well as a methylnaphthalene / dimethylnaphthalene isomerization catalyst and isomerization method. Background Technology

[0002] Polyethylene naphthalate (PEN) is a novel polyester material that offers superior mechanical properties, heat resistance, and gas barrier properties compared to the widely used polyethylene terephthalate (PET), making it widely applicable in electronics, food packaging, and textiles. Currently, the key factor limiting the large-scale application of PEN lies in the complex and costly preparation process of its raw material, 2,6-dimethylnaphthalene. Given the abundance of alkylnaphthalene resources, synthesizing 2,6-dimethylnaphthalene from inexpensive and plentiful 1-methylnaphthalene via isomerization and alkylation is an ideal process route. However, 2,6-dimethylnaphthalene has 10 isomers with similar properties, making separation extremely difficult. To maximize the utilization of dimethylnaphthalene resources and reduce production costs, it is necessary to further isomerize the convertible components in the dimethylnaphthalene mixture to 2,6-dimethylnaphthalene. Therefore, researching and developing low-cost isomerization catalysts for the preparation of 2,6-dimethylnaphthalene is of great significance for the application of PEN.

[0003] In recent years, the main catalysts used for the catalytic isomerization of methylnaphthalene / dimethylnaphthalene have been ZSM-5, Y, Beta, and MOR molecular sieves. US4962260A discloses a method for preparing specific dimethylnaphthalene isomers via liquid-phase solid acid isomerization. This method uses Beta molecular sieves or acidic ultrastable Y molecular sieves as the solid acid, and the reaction is carried out in the range of 200-500℃, which can improve the yield and selectivity of specific dimethylnaphthalenes. US5495060A discloses a method for producing 2,6-dimethylnaphthalene. A catalyst prepared by molding MOR zeolite with a silica-to-alumina ratio greater than 100 and alumina can stably produce 2,6-dimethylnaphthalene with high selectivity and high yield under mild reaction conditions, while suppressing side reactions and catalyst deactivation. However, due to the small pore size of ordinary molecular sieve catalysts, the diffusion of larger alkylnaphthalene molecules within the pores is limited. This results in high product selectivity, but the catalyst is still prone to coking, leading to a rapid decline in activity.

[0004] In contrast, the MCM-22 molecular sieve with its MWW structure contains two independent pore structures: ten-membered rings and twelve-membered rings. Both the upper and lower surfaces of its layered structure are covered with twelve-membered ring pores approximately 0.7 nm deep. This unique structure gives the MCM-22 molecular sieve a large external specific surface area and numerous external surface active centers, exhibiting excellent adsorption and catalytic performance for larger molecules, thus attracting widespread attention from researchers.

[0005] CN106536411B discloses a method for preparing boron-containing zeolite materials with a MWW framework structure of YO2 and B2O3, where Y represents a tetravalent element. The method involves mixing a YO2 source, a B2O3 source, a template agent, and seed crystals for a crystallization reaction. The resulting crystallization product is washed, dried, and calcined to obtain a boron-containing zeolite material with an MWW framework structure. The seed crystals used are zeolite materials with an MWW framework structure and / or layered zeolite precursors, and the template agent is a cycloalkylamine compound. This invention confirms that the presence of seed crystals and organic template agents is necessary for the synthesis of MWW zeolite materials, providing a novel method for synthesizing boron-containing zeolites with an MWW framework structure. However, this method relies on MWW molecular sieve seed crystals, increasing production costs and making the process relatively complex.

[0006] CN116692898A synthesized MWW molecular sieves using boric acid as a structural aid and triethylenediamine and piperazine as dual template agents. This method successfully expanded the synthetic approach for MWW molecular sieves using a novel template agent system. However, in this method, boric acid is used as a structural aid to promote the synthesis of MWW molecular sieves, and the stability of the catalytic activity of the molecular sieves was not investigated.

[0007] Wang et al. (Yilin Wang, Shufang Xu, Xuan He, Fan Yang, Xuedong Zhu, Regulating the acid sites and framework aluminum siting in MCM–22zeolite to enhance its performance in alkylation of benzene with methanol, Microporous and Mesoporous Materials, 2022, 332, 111677.) reported that incorporating a certain proportion of boron into the hydrothermal synthesis of MCM-22 molecular sieves can regulate the distribution of framework aluminum in the sinusoidal channels of MCM-22 molecular sieves. The boron-doped MCM-22 molecular sieves suppressed the formation of byproducts and improved the catalyst lifetime and anti-carbon deposition ability during the catalytic alkylation reaction of benzene and methanol. However, the molecular sieves prepared using inorganic boron by this method are mainly used in alkylation reactions, and their single-pass lifetime is less than 60 hours, still lacking long-term stability.

[0008] To improve the long-term stability of MCM-22 molecular sieves, CN116851032A modifies MCM-22 using methods such as acid washing, which improves the catalyst's stability and product selectivity. Alternatively, CN103803577B and CN104528757B prepare fewer-layer crystals or reduce crystal size by controlling the crystallization reaction conditions, thereby obtaining shorter crystal diffusion paths, shortening the residence time of reactant molecules in the pores, reducing the probability of them transforming into coking macromolecules, and thus improving the catalyst's lifespan. However, the above methods have relatively complex preparation processes, limiting the further application of the catalysts.

[0009] Therefore, given the problems of insufficient catalytic activity or poor long-term stability of methylnaphthalene / dimethylnaphthalene isomerization catalysts, it is quite urgent to develop a catalyst that combines high catalytic activity, target product selectivity, and stability to meet the production requirements of isomerization of methylnaphthalene / dimethylnaphthalene, a key raw material in the PEN preparation process. Summary of the Invention

[0010] To address the aforementioned technical problems, the present invention aims to provide a hydrogen-form boron-containing MWW structured molecular sieve and its preparation method, as well as a methylnaphthalene / dimethylnaphthalene isomerization catalyst and isomerization method. By using a boron-doped MCM-22 molecular sieve to prepare the catalyst, the acidity of the molecular sieve surface can be effectively adjusted, enabling the catalyst to possess both high activity and long lifetime, and making it suitable for the methylnaphthalene / dimethylnaphthalene isomerization reaction.

[0011] To achieve the above objectives, the present invention provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve, wherein the preparation method includes:

[0012] (1) Mix silicon source, aluminum source, alkali source, template agent and water to obtain the first gel;

[0013] (2) The first gel is aged once, and then a boron source is added for a second aging to obtain the second gel; wherein the boron source contains an aromatic ring structure;

[0014] (3) The second gel was subjected to hydrothermal crystallization, and the resulting product was calcined for the first time to obtain a boron-containing MWW structure molecular sieve.

[0015] (4) The boron-containing MWW structure molecular sieve is subjected to ammonium ion exchange, and the resulting product is calcined a second time to obtain a hydrogen-type boron-containing MWW structure molecular sieve.

[0016] According to a specific embodiment of the present invention, preferably, the aromatic ring structure includes one or more combinations of benzene ring structure, naphthalene ring structure, anthracene ring structure, biphenyl structure, terphenyl structure, etc.; more preferably, the aromatic ring structure is a rigid aromatic ring structure, such as benzene ring, naphthalene ring, anthracene ring.

[0017] According to a specific embodiment of the present invention, preferably, the boron source has a structural formula selected from one or more combinations of compounds shown in the following structural formulas:

[0018]

[0019] Wherein, R is selected from one or more combinations of H, halogens (F, Cl, Br), and alkyl groups (preferably H and / or methyl); more preferably, the boron source has the following structural formula: (Pinacol phenylboronic acid ester), where R is H.

[0020] According to a specific embodiment of the present invention, preferably, the molar ratio of each component in the first gel is: SiO2 / Al2O3 = 20-100, M2O / SiO2 = 0.03-0.15, N / SiO2 = 0.05-0.40, H2O / SiO2 = 15-120; wherein, the silicon source is calculated as SiO2, the aluminum source as Al2O3, the alkali source as M2O, and the template agent as N.

[0021] According to a specific embodiment of the present invention, preferably, the molar ratio of boron (B) atoms in the boron source to Al atoms in the first gel satisfies B / Al = 0.01-20.

[0022] In some specific embodiments, preferably, the molar ratio of B atoms in the boron source to Al atoms in the first gel satisfies B / Al = 0.1-8.

[0023] In this invention, during the synthesis of MWW-structured molecular sieves, organoboron with a large molecular size and rigidity is used to modify the boron (B) content. This makes it difficult for the organoboron to enter the inner surface of the MWW molecular sieve during crystallization due to its large molecular size. Consequently, the organoboron is adsorbed on the outer surface of the molecular sieve and undergoes slow decomposition, thereby allowing B atoms to enter the framework of the molecular sieve's outer surface and regulate the acidity of the outer surface. The methylnaphthalene / dimethylnaphthalene isomerization catalyst prepared from the organoboron-modified B-MWW molecular sieve exhibits excellent catalytic activity and stability when used in the methylnaphthalene / dimethylnaphthalene isomerization reaction.

[0024] According to a specific embodiment of the present invention, preferably, the temperature of the first aging is 25-80℃ (preferably 30-70℃, more preferably 40-60℃), and the aging time is 2-24 hours (preferably 4-12 hours, more preferably 4-8 hours).

[0025] According to a specific embodiment of the present invention, preferably, the temperature of the secondary aging is 25-80℃ (preferably 30-70℃, more preferably 40-60℃), and the time of the secondary aging is 2-24 hours (preferably 4-12 hours, more preferably 4-8 hours).

[0026] In this invention, the molecular sieve forms microcrystals during the aging process. The large and rigid organic boron molecules cannot penetrate the interior of the formed molecular sieve microcrystals, and instead are mainly adsorbed on the outer surface of the molecular sieve. Furthermore, when the temperature is increased for crystallization, the organic boron slowly decomposes and releases boron in an alkaline environment, thereby regulating the acidity within the outer surface framework of the MCM-22 molecular sieve. Therefore, by using the aging process to allow the molecular sieve microcrystals to grow at low temperatures, it is possible to help prevent boron from entering the interior of the molecular sieve framework, thus achieving acidity regulation concentrated on the outer surface of the molecular sieve. In addition, the aging process of this invention is a "segmented" aging process. First, molecular sieve microcrystals are generated through a primary aging process; then, a boron source is added for a secondary aging process. This secondary aging process, on the one hand, prevents the rapid decomposition of organic boron due to excessively high crystallization temperatures, and on the other hand, allows the organic boron to be fully adsorbed on the outer surface of the microcrystals during the aging process.

[0027] According to a specific embodiment of the present invention, preferably, the silicon source includes one or more of silica gel, silica sol, fumed silica, and water glass.

[0028] According to a specific embodiment of the present invention, preferably, the aluminum source includes one or a combination of two or more of aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum chloride, aluminum oxide, and aluminum hydroxide.

[0029] According to a specific embodiment of the present invention, preferably, the alkali source includes one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; more preferably, sodium hydroxide.

[0030] According to a specific embodiment of the present invention, preferably, the template agent includes one or a combination of two or more of hexamethyleneimine, triethylenediamine, piperazine, cyclohexylamine, and diethyldimethylammonium hydroxide; more preferably, it is one or a combination of two or more of hexamethyleneimine, piperazine, and diethyldimethylammonium hydroxide.

[0031] In the above preparation method, preferably, the hydrothermal crystallization temperature is 80-220℃, more preferably 100-200℃, and even more preferably 120-180℃. The growth of the molecular sieve is controlled by adjusting the crystallization temperature; excessively low or high temperatures can lead to the formation of impurity phases.

[0032] In the above preparation method, preferably, the hydrothermal crystallization time is 12-120 hours, more preferably 18-96 hours, and even more preferably 24-80 hours.

[0033] In the above preparation method, preferably, the ammonium ion exchange process is as follows: the boron-containing MWW structure molecular sieve is mixed with an appropriate amount of ammonium salt solution (preferably at a mass ratio of 1:10) and stirred; more preferably, the concentration of the ammonium salt solution is 0.1-3 mol / kg, the stirring temperature is 25-100℃, and the stirring time is 0.5-6 hours.

[0034] In the above preparation method, preferably, the temperature of the first calcination is 450-600℃ and the time of the first calcination is 2-12 hours; the temperature of the second calcination is 450-600℃ and the time of the second calcination is 2-12 hours; the first calcination and the second calcination are respectively preceded by the steps of filtration, washing and drying.

[0035] The present invention also provides a hydrogen-form boron-containing MWW structured molecular sieve, which is prepared by the above-described method for preparing hydrogen-form boron-containing MWW structured molecular sieves.

[0036] According to a specific embodiment of the present invention, preferably, the total specific surface area of ​​the hydrogen-form boron-containing MWW structured molecular sieve is 400-700 m². 2 / g, total pore volume is 0.5-1.0cm³ 3 / g.

[0037] According to a specific embodiment of the present invention, preferably, the silicon-aluminum molar ratio SiO2 / Al2O3 of the hydrogen-type boron-containing MWW structure molecular sieve is 20-100, the grain size is 20nm-1μm, and the relative crystallinity is 85%-110%.

[0038] The present invention also provides a methylnaphthalene / dimethylnaphthalene isomerization catalyst, which is made of the above-mentioned hydrogen-form boron-containing MWW structure molecular sieve and a binder; wherein, based on 100% by weight of the isomerization catalyst, the content of the hydrogen-form boron-containing MWW structure molecular sieve is 20%-90% (preferably 50%-80%), and the content of the binder is 10%-80%.

[0039] According to a specific embodiment of the present invention, preferably, the content of element B is 0.01%-0.5% based on the mass of the hydrogen-type boron-containing MWW structure molecular sieve as 100%.

[0040] According to a specific embodiment of the present invention, preferably, the isomerization catalyst is prepared by mixing the above-mentioned hydrogen-type boron-containing MWW structure molecular sieve with binder, concentrated nitric acid and water evenly, extruding it, drying it and then calcining it a third time; the extrusion is performed using a screw extrusion molding machine.

[0041] In some specific embodiments, preferably, the binder is one or a combination of two or more of boehmite, alumina, guar gum, etc.

[0042] In some specific implementations, preferably, the third roasting temperature is 480-580℃ and the time is 4-12 hours.

[0043] This invention also provides a method for isomerization of methylnaphthalene / dimethylnaphthalene, wherein the steps of the method include:

[0044] Using at least one of methylnaphthalene and / or dimethylnaphthalene isomers as raw materials, the raw materials are contacted with the above-mentioned methylnaphthalene / dimethylnaphthalene isomerization catalyst to carry out an alkylnaphthalene isomerization reaction.

[0045] According to a specific embodiment of the present invention, preferably, the reaction temperature of the alkylnaphthalene isomerization reaction is 200-400℃, the reaction pressure is 0.1-5MPa, the molar ratio of carrier gas to feedstock is (0.1-100):1, and the mass hourly space velocity of the feedstock is 0.01-5h. -1 .

[0046] According to a specific embodiment of the present invention, preferably, the isomers of methylnaphthalene and / or dimethylnaphthalene include 1,2-dimethylnaphthalene, 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,5-dimethylnaphthalene, 1,6-dimethylnaphthalene, 1,7-dimethylnaphthalene, 1,8-dimethylnaphthalene, 2,3-dimethylnaphthalene, 2,6-dimethylnaphthalene, and 2,7-dimethylnaphthalene.

[0047] In some specific embodiments, preferably, the solvent of the raw material is an aromatic hydrocarbon; the aromatic hydrocarbon includes one or more of toluene, benzene, mesitylene, and tetrahydronaphthalene; more preferably, it is benzene and / or mesitylene.

[0048] In some specific embodiments, preferably, the carrier gas includes one or more of nitrogen, hydrogen, and argon; more preferably, it is nitrogen and / or hydrogen.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] (1) The hydrogen-type boron-containing MWW structure molecular sieve provided by the present invention has a high specific surface area. Through the synergistic effect of organoboron modification and segmented aging, the acidity of the outer surface of the molecular sieve is reduced, so that the isomerization catalyst prepared by the molecular sieve can simultaneously meet the requirements of high activity and long life.

[0051] (2) The methylnaphthalene / dimethylnaphthalene isomerization catalyst provided by the present invention has excellent alkylnaphthalene isomerization catalytic activity and anti-carbon deposition ability. Its weak acidity and diffusion performance avoid the occurrence of side reactions during the isomerization process, which can extend the catalyst life and greatly improve the stability, and has great industrial application prospects. Attached Figure Description

[0052] Figure 1 The PXRD patterns are of the hydrogen-form molecular sieves prepared in Examples 1-3 and Comparative Examples 1-3.

[0053] Figure 2 The PXRD patterns are of the hydrogen-form molecular sieves prepared in Examples 4-6 and Comparative Examples 4-6.

[0054] Figure 3 SEM images of the hydrogen-form molecular sieves prepared in Examples 1-3 and Comparative Examples 1-3.

[0055] Figure 4 SEM images of the hydrogen-form molecular sieves prepared in Examples 4-6 and Comparative Examples 4-6.

[0056] Figure 5 The nitrogen adsorption-desorption curves of the hydrogen-type molecular sieves prepared in Examples 1-3 and Comparative Examples 1-3 at 77 K are shown.

[0057] Figure 6 The nitrogen adsorption-desorption curves of the hydrogen-type molecular sieves prepared in Examples 4-6 and Comparative Examples 4-6 at 77 K are shown.

[0058] Figure 7 The NH3-TPD diagrams are for the hydrogen-form molecular sieves prepared in Examples 1-3 and Comparative Examples 1-3.

[0059] Figure 8 The NH3-TPD diagrams are for the hydrogen-form molecular sieves prepared in Examples 4-6 and Comparative Examples 4-6. Detailed Implementation

[0060] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0061] Example 1

[0062] This embodiment provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0063] (1) 600g of 30% silica sol, 22g of sodium aluminate, 17.4g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0064] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 36.1g of pinacol ester of phenylboronic acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0065] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0066] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0067] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in air to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as C1.

[0068] Example 2

[0069] This embodiment provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0070] (1) 600g of 30% silica sol, 22g of sodium aluminate, 17.4g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0071] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 72.3g of pinacol phenylboronic acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0072] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0073] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0074] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as C2.

[0075] Example 3

[0076] This embodiment provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0077] (1) 600g of 30% silica sol, 22g of sodium aluminate, 17.4g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0078] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 108.4g of pinacol phenylboronic acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0079] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0080] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0081] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as C3.

[0082] Example 4

[0083] This embodiment provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0084] (1) 600g of 30% silica sol, 15.4g of sodium aluminate, 19.5g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0085] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 25.3g of pinacol ester of phenylboronic acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0086] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0087] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0088] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in air to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as C4.

[0089] Example 5

[0090] This embodiment provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0091] (1) 600g of 30% silica sol, 15.4g of sodium aluminate, 19.5g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0092] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 50.6g of pinacol phenylboronic acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0093] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0094] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0095] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as C5.

[0096] Example 6

[0097] This embodiment provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0098] (1) 600g of 30% silica sol, 15.4g of sodium aluminate, 19.5g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0099] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 75.9g of pinacol phenylboronic acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0100] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0101] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0102] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in air to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as C6.

[0103] Comparative Example 1

[0104] This comparative example provides a method for preparing hydrogen-form MWW structured molecular sieves and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0105] (1) 600g of 30% silica sol, 22g of sodium aluminate, 17.4g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring. The mixture was aged at 50°C for 6h to obtain a white and uniform gel.

[0106] (2) The gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely the MWW structure molecular sieve.

[0107] (3) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-form MCM-22 molecular sieve, i.e. hydrogen-form MWW structure molecular sieve.

[0108] (4) The obtained hydrogen-type MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as D1.

[0109] Comparative Example 2

[0110] This comparative example provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0111] (1) 600g of 30% silica sol, 22g of sodium aluminate, 17.4g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0112] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 21.9g of boric acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0113] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0114] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0115] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as D2.

[0116] Comparative Example 3

[0117] This comparative example provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0118] (1) 600g of 30% silica sol, 22g of sodium aluminate, 72.3g of pinacol phenylboronic acid, 17.4g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were thoroughly mixed under vigorous stirring to obtain a white and uniform gel.

[0119] (2) The gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The resulting precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0120] (3) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0121] (4) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as D3.

[0122] Comparative Example 4

[0123] This comparative example provides a method for preparing hydrogen-form MWW structured molecular sieves and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0124] (1) 600g of 30% silica sol, 15.4g of sodium aluminate, 19.5g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring. The mixture was aged at 50°C for 6 hours to obtain a white and uniform gel.

[0125] (2) The gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The resulting precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely the MWW structure molecular sieve.

[0126] (3) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-form MCM-22 molecular sieve, i.e. hydrogen-form MWW structure molecular sieve.

[0127] (4) The obtained hydrogen-type MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as D4.

[0128] Comparative Example 5

[0129] This comparative example provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0130] (1) 600g of 30% silica sol, 15.4g of sodium aluminate, 19.5g of sodium hydroxide, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain the first gel;

[0131] (2) The first gel of the mixture was aged at 50°C for 6 hours, and then 15.3g of boric acid was added at once, and the mixture was aged at 50°C for 6 hours to obtain a white and uniform second gel.

[0132] (3) The second gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0133] (4) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0134] (5) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in air to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as D5.

[0135] Comparative Example 6

[0136] This comparative example provides a method for preparing a hydrogen-form boron-containing MWW structured molecular sieve and a methylnaphthalene / dimethylnaphthalene isomerization catalyst, specifically including the following steps:

[0137] (1) 600g of 30% silica sol, 15.4g of sodium aluminate, 19.5g of sodium hydroxide, 50.6g of pinacol ester of phenylboronic acid, 63g of hexamethyleneimine and 800g of deionized water were mixed thoroughly under vigorous stirring to obtain a white and uniform gel.

[0138] (2) The gel was transferred to a high-pressure stainless steel reactor and heated at 170°C for 48 hours for hydrothermal crystallization. The precipitate was filtered, washed, dried and then calcined at 500°C for 6 hours to obtain a white powder, namely boron-containing MWW structure molecular sieve.

[0139] (3) The above powder was placed in a 1 mol / kg ammonium nitrate solution at a solid-liquid weight ratio of 1:10 and stirred at 80°C for 2 hours. After filtration, washing and drying, it was calcined at 500°C for 6 hours to obtain hydrogen-type B-MCM-22 molecular sieve, namely hydrogen-type boron-containing MWW structure molecular sieve.

[0140] (4) The obtained hydrogen-type B-MCM-22 molecular sieve was mixed with alumina, concentrated nitric acid, guar gum powder and water in a mass ratio of 100:20:5:5:100. After being extruded into strips, it was calcined at 500°C for 6 hours in an air atmosphere to obtain the methylnaphthalene / dimethylnaphthalene isomerization catalyst, denoted as D6.

[0141] Test Example 1

[0142] This test case investigates the morphology, relative crystallinity, total acidity, external surface acidity, specific surface area, total pore volume, and silica-alumina ratio of the hydrogen-form B-MCM-22 molecular sieves prepared in Examples 1-6 and Comparative Examples 2-3 and 5-6, as well as the hydrogen-form MCM-22 molecular sieves prepared in Comparative Examples 1 and 4. The relevant results and analyses are as follows:

[0143] The XRD patterns of the hydrogen form B-MCM-22 molecular sieves or hydrogen form MCM-22 molecular sieves prepared in Examples 1-6 and Comparative Examples 1-6 are shown below. Figure 1 , Figure 2 As shown, from Figure 1 , Figure 2 It can be seen that the prepared molecular sieve products all have typical MWW structural characteristic peaks.

[0144] The SEM images of the hydrogen form B-MCM-22 molecular sieves or hydrogen form MCM-22 molecular sieves prepared in Examples 1-6 and Comparative Examples 1-6 are shown below. Figure 3 , Figure 4 As shown, from Figure 3 , Figure 4 As can be seen, the molecular sieve products obtained are all in the form of flakes.

[0145] The nitrogen adsorption curves of the hydrogen form B-MCM-22 molecular sieves or hydrogen form MCM-22 molecular sieves prepared in Examples 1-6 and Comparative Examples 1-6 at 77 K are shown below. Figure 5 , Figure 6 As shown, the measured specific surface area and total pore volume are recorded in Table 1. From the specific surface area results in Table 1, it can be seen that the specific surface area of ​​the MCM-22 molecular sieve prepared in this invention is close to 600 m². 2 / g, reaching a maximum of 606m 2 / g.

[0146] The NH3-TPD test results of the hydrogen form B-MCM-22 molecular sieves or hydrogen form MCM-22 molecular sieves prepared in Examples 1-6 and Comparative Examples 1-6 are as follows: Figure 7 , Figure 8 As shown, the measured total acid content is recorded in Table 1. From the total acid content results in Table 1, it can be seen that, generally speaking, the lower the silicon-to-aluminum ratio, the higher the total acid content. When the silicon-to-aluminum ratios are similar, Examples 1 and 4 modified with organoboron have lower total acid contents compared to Comparative Examples 1 and 4 without B modification, respectively. This indicates that, at similar silicon-to-aluminum ratios, organoboron does indeed have the function of regulating the acidity of the molecular sieve surface.

[0147] In addition, the acid content of the outer surface of the molecular sieves prepared in Examples 1-6 and Comparative Examples 1-6 was tested using 2,4-dimethylquinoline as a probe molecule, and the results are recorded in Table 1. The data on the acid content of the outer surface show that, when the silicon-to-aluminum ratio is similar, the acid content of the outer surface of Example 2 (using organoboron modification) is lower than that of Comparative Example 2 (inorganic boron modification) and Comparative Example 3 (without aging) under the same preparation conditions. Similarly, the acid content of the outer surface of Example 5 (organoboron modification) is also lower than that of Comparative Example 5 (inorganic boron modification) and Comparative Example 6 (without aging) under the same preparation conditions. The high total acid content is due to the higher acidity of the inner surface of the examples. Therefore, it can be seen that the organoboron modification and segmented aging methods used in this invention mainly reduce the acid content of the "outer surface" of the MCM-22 molecular sieve, while having a smaller impact on the acid content of its inner surface, which is more conducive to improving catalytic performance.

[0148] The silica-to-alumina ratio (S / A ratio) of the hydrogen-form B-MCM-22 molecular sieves or hydrogen-form MCM-22 molecular sieves prepared in Examples 1-6 and Comparative Examples 1-6 was tested using XRF, and the measured S / A ratios are recorded in Table 1. In this invention, by controlling the proportions of each raw material used in the preparation of the first gel, the S / A ratios of Examples 1-3 and Comparative Examples 1-3 are similar, around 27; while the S / A ratios of Examples 4-6 and Comparative Examples 4-6 are similar, around 37. The conversion rate test results in Table 2 show that, for the reaction type in this invention, a low S / A ratio MCM-22 molecular sieve is beneficial for improving catalytic performance.

[0149] Table 1.

[0150]

[0151] Test Example 2

[0152] The evaluation and analysis method for catalysts can be to automatically control the reaction temperature by electric heating, control the carrier gas flow rate by mass flow meter, and use a plunger pump to pump the raw material containing 1-methylnaphthalene or dimethylnaphthalene into the reactor, which then passes through the catalyst bed from top to bottom to undergo an isomerization reaction.

[0153] This test example demonstrates the 1-methylnaphthalene isomerization test performed on the catalysts prepared in Examples 1-6 and Comparative Examples 1-6, respectively. The specific procedures and results are as follows:

[0154] The isomerization of 1-methylnaphthalene was tested using a fixed-bed reactor for the catalysts prepared in the above examples and comparative examples. 5g of catalyst (approximately 2-4mm in length) was loaded into the middle section of a 20mm inner diameter stainless steel microreactor, with glass beads placed at the top and bottom sections to immobilize the catalyst. Reaction conditions were: reaction temperature 300℃, pressure 3MPa, nitrogen carrier gas flow rate 30mL / min, feedstock a mixed solution of 50wt% 1-methylnaphthalene / 50wt% benzene (benzene as solvent), carrier gas to feedstock molar ratio 45.7, and 1-methylnaphthalene mass hourly space velocity (WHSV) 0.5h⁻¹. -1 The contents of 1-methylnaphthalene, 2-methylnaphthalene, and byproducts were determined using a gas chromatograph (Agilent GC7890A), and the conversion rate of 1-methylnaphthalene was calculated according to the following formula. The results are shown in Table 2.

[0155] 1-Methylnaphthalene conversion rate % = (Inlet 1-methylnaphthalene content - Outlet 1-methylnaphthalene content) / Inlet 1-methylnaphthalene content × 100%;

[0156] Conversion rate decrease = (initial conversion rate - 200h conversion rate) / initial conversion rate × 100%;

[0157] Table 2.1 1-Methylnaphthalene isomerization test results

[0158]

[0159] The results in Tables 1 and 2 show that, although the hydrogen-type boron-containing MWW structured molecular sieves prepared by the present invention using an organic boron source and segmented aging have similar overall crystallinity, specific surface area, and morphology to MWW molecular sieves prepared without boron (D1, D4), or using an inorganic boron source (D2, D5), or without an aging process (D3, D6), the boron-containing MWW structured molecular sieve catalyst prepared by the organic boron source and segmented aging exhibits higher conversion rate and resistance to deactivation in the catalytic 1-methylnaphthalene isomerization test. Specifically, taking C2 and C5 as examples, the catalysts prepared from MWW molecular sieves modified with organic boron sources and subjected to staged aging showed a smaller decrease in conversion rate after 200 hours of reaction, maintaining high catalytic activity. In contrast, when other preparation and experimental conditions were the same as for C2 or C5, the catalysts prepared from MWW molecular sieves modified with inorganic boron sources (D2, D5) or without aging (D3, D6) showed a larger decrease in conversion rate after 200 hours of reaction. Therefore, the catalysts prepared by reducing the acidity of the outer surface of MCM-22 molecular sieves in this invention exhibit better long-term stability.

Claims

1. A method for preparing a hydrogen form of a boron-containing MWW structure molecular sieve, wherein, The preparation method includes: (1) Mix silicon source, aluminum source, alkali source, template agent and water to obtain the first gel; (2) The first gel is aged once, and then a boron source is added for a second aging to obtain the second gel; wherein the boron source contains an aromatic ring structure; (3) The second gel was subjected to hydrothermal crystallization, and the resulting product was calcined for the first time to obtain a boron-containing MWW structure molecular sieve. (4) The boron-containing MWW structure molecular sieve is subjected to ammonium ion exchange, and the resulting product is calcined a second time to obtain a hydrogen-type boron-containing MWW structure molecular sieve.

2. The production method according to claim 1, wherein, The aromatic ring structure includes one or more of the following: benzene ring structure, naphthalene ring structure, anthracene ring structure, biphenyl structure, and terphenyl structure.

3. The production method according to claim 2, wherein, The boron source is selected from one or more of the compounds shown in the following structural formulas: R is selected from one or more combinations of H, halogens, and alkyl groups.

4. The production method according to claim 1, wherein The molar ratios of the components in the first gel are: SiO2 / Al2O3 = 20-100, M2O / SiO2 = 0.03-0.15, N / SiO2 = 0.05-0.40, and H2O / SiO2 = 15-120; wherein the silicon source is calculated as SiO2, the aluminum source as Al2O3, the alkali source as M2O, and the template agent as N.

5. The production method according to claim 1, wherein The molar ratio of B atoms in the boron source to Al atoms in the first gel satisfies B / Al = 0.01-20.

6. The production method according to claim 1, wherein The temperature for the first aging process is 25-80℃, and the aging time is 2-24 hours. The secondary aging temperature is 25-80℃, and the secondary aging time is 2-24 hours.

7. The production method according to claim 1, wherein The silicon source includes one or more of silica gel, silica sol, silica fume, and water glass. And / or, the aluminum source includes one or more of aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum chloride, aluminum oxide, and aluminum hydroxide; And / or, the alkali source includes one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; And / or, the template agent comprises one or more of hexamethyleneimine, triethylenediamine, piperazine, cyclohexylamine, and diethyldimethylammonium hydroxide.

8. A hydrogen-form boron-containing MWW structured molecular sieve, which is prepared by the preparation method of the hydrogen-form boron-containing MWW structured molecular sieve according to any one of claims 1-7.

9. The molecular sieve according to claim 8, wherein, The total specific surface area of ​​the molecular sieve is 400-700 m². 2 / g, total pore volume is 0.5-1.0cm³ 3 / g.

10. A methylnaphthalene / dimethylnaphthalene isomerization catalyst, wherein the isomerization catalyst is made from the hydrogen-form boron-containing MWW structure molecular sieve as described in claim 8 or 9 and a binder; wherein, Based on the weight of the isomerization catalyst as 100%, the content of the hydrogen-type boron-containing MWW structured molecular sieve is 20%-90%, and the content of the binder is 10%-80%.

11. A methylnaphthalene / dimethylnaphthalene isomerization process wherein, The steps of this method include: Using at least one of methylnaphthalene and / or dimethylnaphthalene isomers as raw materials, the raw materials are contacted with the methylnaphthalene / dimethylnaphthalene isomerization catalyst of claim 10 to carry out an alkylnaphthalene isomerization reaction.

12. The method of claim 11, wherein, The alkylnaphthalene isomerization reaction is carried out at a temperature of 200-400℃, a reaction pressure of 0.1-5 MPa, a carrier gas to feed molar ratio of (0.1-100):1, and a feed mass hourly space velocity of 0.01-5 h⁻¹. -1 .

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