Molecular sieve and its preparation method and application

Abstract

The present invention relates to the field of molecular sieves, and discloses a ZSM-48 molecular sieve and a preparation method and application thereof, wherein the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200m 2 / g, the crystal grains of the ZSM‑48 molecular sieve are ellipsoidal, the major diameter does not exceed 700nm and the ratio of the major diameter to the minor diameter is 1‑3:1. A synthesis system of clean water + molecular sieve mother liquor is adopted, seed crystals are introduced, and a ZSM‑48 molecular sieve with an ellipsoidal morphology is prepared through three stages of crystallization processes at different temperatures, thereby increasing the specific surface area of ​​the molecular sieve. When the molecular sieve is applied to the dewaxing of waxy oil, the product yield and viscosity index are higher.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieves, and in particular to a molecular sieve and a preparation method and application thereof. Background Art

[0002] The lubricating base oil produced by the hydroisomerization dewaxing method has a higher paraffin content and a lower S and N content, and has higher antioxidant stability, lower volatility, higher viscosity index (VI) and excellent low-temperature flow properties. Compared with traditional solvent dewaxing, hydrocracking and other methods, it shows good performance and economic and environmental advantages. The core of the hydroisomerization dewaxing technology is mainly composed of isomerization dewaxing catalysts. Isomerization dewaxing catalysts are bifunctional catalysts that usually load precious metals Pt and / or Pd onto molecular sieves with special pore structures. The use of special molecular sieves and special processes can obtain better products.

[0003] ZSM-48 molecular sieve is a new type of high-silicon molecular sieve developed in the 1980s. It has a two-dimensional ten-membered ring pore structure and belongs to the orthorhombic crystal system. The pores are connected by 5-membered rings, and the pore diameter is about 0.6nm. It is characterized by a high silicon-aluminum molar ratio and tubular linear pores, which can accommodate organic molecules with a smaller kinetic radius than benzene. In theory, ZSM-48 molecular sieve has a smaller pore "self-restraint effect", and the pore size is suitable for the shape-selective isomerization of chain alkanes. At present, many synthesis methods of ZSM-48 molecular sieves have been reported at home and abroad.

[0004] CN101801848A discloses a method for preparing ZSM-48, comprising: (a) providing an aqueous reaction mixture comprising at least one silica source, at least one alumina source, at least one hydroxyl ion source, at least one alkyl diquaternary ammonium source R 2+ , having the formula (CH 3 ) 3 N + (CH 3 ) 3 ions, and optionally seeds, wherein the composition of the reaction mixture comprises the following molar ratios: R 2+ :SiO 2 Less than 0.1, SiO 2 :Al 2 O 3 Less than 100, OH - :SiO 2 less than 0.2; and (b) crystallizing the reaction mixture under conditions effective to produce the ZSM-48.

[0005] CN102910642A discloses a method for preparing a ZSM-48 molecular sieve, comprising: (1) mixing a silicon source, an aluminum source, an alkali, water and a template agent uniformly, and expressing the molar ratio of the oxides as DBH / SiO 2 =0.025-0.20,TMA / SiO 2 =0.05-0.40,ETA / SiO 2 =0.25-1.50, SiO 2 :Al 2 O 3 =150-500, Na 2 O / / SiO 2 =0.01-0.20, H 2 O / SiO 2 =5-50, DBH represents the template agent dibromohexane; TMA represents the template agent blue methylamine; ETA represents the template agent ethanol; (2) Crystallization: the reaction mixture is heated to 150-170°C and hydrothermally crystallized for 4-10 days; (3) After the crystallization is completed, the ZSM-48 molecular sieve is obtained by filtering, washing and drying. The method uses a relatively cheap template agent to synthesize a ZSM-48 molecular sieve with a low silicon-aluminum ratio for hydroisomerization dewaxing.

[0006] CN102874833A discloses a method for synthesizing a ZSM-48 molecular sieve, which uses a mother liquor synthesized from the ZSM-48 molecular sieve and uses the mother liquor as a raw material for synthesizing the ZSM-48 molecular sieve. 2 、Al 2 O 3 、Na 2 O, the content of template agent (SDA); according to the content of each component in the mother liquor, silicon source, aluminum source, alkali source, template agent and water are added in proportion to prepare a gel mixture for synthesizing a new ZSM-48 molecular sieve; the gel mixture is purified in a hydrothermal reactor to obtain ZSM-48 molecular sieve and mother liquor. The mother liquor is repeatedly recycled. In order to utilize the mother liquor, reduce environmental pollution and reduce production costs.

[0007] In addition to the above-mentioned relatively simple templates, some complex templates are also disclosed. EP-A-142317 discloses the synthesis of ZSM-48 molecular sieves in the presence of a specific linear diquaternary ammonium compound having the following general formula: [(R) 3 N + (Z)m[(R) 3 N + ](X - ) 2, wherein each R is an alkyl or heteroalkyl group having 1-20 carbon atoms, a cycloalkyl or cycloheteroalkyl group having 3-6 carbon atoms, or an aryl or heteroaryl group, Z is an alkylene or heteroalkylene group having 1-20 carbon atoms, an alkenylene or heteroalkenylene group having 2-20 carbon atoms, or an arylene metal or heteroarylene group, m is 5, 6, 8, 9 or 10, and X- is an anion. CN102910642A discloses a method for synthesizing ZSM-48 molecular sieve using dibromohexane, trimethylamine and ethanol as templates, which has the characteristics of low synthesis cost and a silicon-aluminum ratio ranging from 150 to 500. The prior art mainly focuses on the crystal phase control of ZSM-48 molecular sieve and the selection of templates used in the synthesis process, and there are few reports on the morphology and size control of ZSM-48 molecular sieve. Summary of the invention

[0008] The purpose of the present invention is to overcome the problem that the prior art lacks control over the morphology and size of ZSM-48 molecular sieves, and the product yield of the prepared catalyst in the catalytic reaction is low. A molecular sieve and its preparation method and application are provided. The ZSM-48 molecular sieve has an ellipsoidal morphology and a large specific surface area. When used in the dewaxing reaction of waxy oil, the product yield and viscosity index are higher.

[0009] In order to achieve the above object, the present invention provides a ZSM-48 molecular sieve, wherein the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200m 2 / g, the crystal grains of the ZSM-48 molecular sieve are ellipsoidal, the major diameter does not exceed 700nm and the ratio of major diameter to minor diameter is 1-3:1.

[0010] The second aspect of the present invention provides a method for preparing a ZSM-48 molecular sieve, the method comprising the following steps:

[0011] (1) providing a mixture containing a silicon source, an alkali source, an aluminum source, a template, water, a molecular sieve mother liquor, and a seed crystal;

[0012] (2) subjecting the mixture to a crystallization reaction; the conditions of the crystallization reaction include: reacting at 20° C.-50° C. for 1-20 h, reacting at 50° C.-80° C. for 1-34 h, and then reacting at 80° C.-180° C. for 1-70 h;

[0013] (3) The mixture obtained by the crystallization reaction in step (2) is subjected to solid-liquid separation to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and the molecular sieve mother liquor is returned to step (1);

[0014] The method further comprises an optional step (4), which comprises: acidifying and precipitating the molecular sieve mother liquor, and then performing solid-liquid separation, and returning the obtained filtrate to step (1);

[0015] The mass percentage of the added seed crystals in step (1) is not less than 10% of the mass percentage of the silicon source, and the silicon source is SiO 2 count.

[0016] The third aspect of the present invention provides the use of the ZSM-48 molecular sieve described in the first aspect or the ZSM-48 molecular sieve prepared by the method described in the second aspect in a hydrogenation isomerization reaction.

[0017] Through the above technical scheme, the crystal grains of the ZSM-48 molecular sieve described in the present invention have an ellipsoidal morphology and a large specific surface area. When the molecular sieve is applied to the hydroisomerization of waxy oil, the product yield and viscosity index are higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the X-ray diffraction pattern of the seed crystal A1 obtained in Preparation Example 1-1 after calcination;

[0019] Figure 2 is the X-ray diffraction pattern of the seed crystal A3 obtained in Preparation Example 1-3 after calcination;

[0020] Figure 3 This is the SEM image of the ZSM-48 molecular sieve in Preparation Example 2-1. DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] The first aspect of the present invention provides a ZSM-48 molecular sieve, wherein the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is not less than 200m 2 / g, the crystal grains of the ZSM-48 molecular sieve are ellipsoidal, the major diameter does not exceed 700nm and the ratio of major diameter to minor diameter is 1-3:1.

[0023] The ZSM-48 molecular sieve of the present invention has an ellipsoidal morphology with a smaller aspect ratio, a high silicon-aluminum ratio and a large specific surface area. When the molecular sieve is used for the hydrogenation isomerization of waxy oil, the product yield and viscosity index are higher.

[0024] According to a preferred embodiment of the present invention, the specific surface area of ​​the ZSM-48 molecular sieve is 200-280m 2 / g.

[0025] Preferably, the aspect ratio of the ZSM-48 molecular sieve is 1-2:1.

[0026] According to a preferred embodiment of the present invention, the pore volume of the ZSM-48 molecular sieve is 0.20-0.30 ml / g.

[0027] According to a preferred embodiment of the present invention, the crystal size of the ZSM-48 molecular sieve is 300-700 nm, preferably 400-600 nm.

[0028] Under the above preferred conditions, the molecular sieve has better diffusion performance of isomerized products.

[0029] The second aspect of the present invention provides a method for preparing a ZSM-48 molecular sieve, the method comprising the following steps:

[0030] (1) providing a mixture containing a silicon source, an alkali source, an aluminum source, a template, water, a molecular sieve mother liquor, and a seed crystal;

[0031] (2) subjecting the mixture to a crystallization reaction; the conditions of the crystallization reaction include: reacting at 20° C.-50° C. for 1-20 h, reacting at 50° C.-80° C. for 1-34 h, and then reacting at 80° C.-180° C. for 1-70 h;

[0032] (3) The mixture obtained by the crystallization reaction in step (2) is subjected to solid-liquid separation to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and the molecular sieve mother liquor is returned to step (1);

[0033] The method further comprises an optional step (4), which comprises: acidifying and precipitating the molecular sieve mother liquor, and then performing solid-liquid separation, and returning the obtained filtrate to step (1);

[0034] The mass percentage of the added seed crystals in step (1) is not less than 10% of the mass percentage of the silicon source, and the silicon source is SiO 2 count.

[0035] According to the present invention, the formation of small crystals is facilitated by recycling the molecular sieve mother liquor and introducing crystal seeds. In the present invention, the progress and temperature of the crystallization reaction are strictly controlled through three stages of crystallization processes at different temperatures. Compared with the prior art, the crystallization reaction process is set at a low temperature, which helps to control the growth of crystals.

[0036] In the present invention, it is understood by those skilled in the art that the molecular sieve mother liquor can be obtained by arbitrarily selecting the above step (3) or steps (3) and (4). When the method provided by the present invention includes step (4), it is understood by those skilled in the art that the filtrate provides at least part of the molecular sieve mother liquor described in step (1).

[0037] Preferably, the preparation method further comprises step (4). Adopting the above preferred implementation mode is conducive to obtaining a ZSM-48 molecular sieve with small crystals and high specific surface area.

[0038] In the present invention, the amount of seed crystals used is relatively large. According to a preferred embodiment of the present invention, the mass percentage of the seed crystals added in step (1) is 10-30% of the mass percentage of the silicon source, and more preferably 20-30%. In the above preferred case, it is conducive to forming more crystal nuclei, and the prepared molecular sieve has the characteristics of small grains.

[0039] According to the present invention, preferably, in the mixture of step (1), the amount of the molecular sieve mother liquor is less than the amount of water. Further preferably, the mass percentage of the molecular sieve mother liquor added in step (1) to the total mass percentage of the molecular sieve mother liquor and water in step (1) is not more than 50%, more preferably 10-30%. In the above preferred case, it is helpful to form a molecular sieve with small crystals and high specific surface area.

[0040] According to a preferred embodiment of the present invention, the water may be deionized water.

[0041] In the present invention, the ratio of each raw material in the reactants has a certain influence on the final performance of the molecular sieve. According to a preferred embodiment of the present invention, specifically, the composition of each component in the mixture in step (1) calculated by molar amount satisfies the following relationship:

[0042] The composition of each component calculated by molar amount satisfies the following relationship:

[0043] R / SiO 2 =0.01-0.40, preferably 0.01-0.08;

[0044] M + / SiO 2 =0.01-0.40, preferably 0.1-0.2;

[0045] Al 2 O 3 / SiO 2 =0-0.02, preferably 0.01-0.015;

[0046] H 2 O / SiO2 =5-30, preferably 5-20;

[0047] Among them, SiO 2 Refers to SiO in the silicon source 2 , R represents the template, M + Indicates alkaline source.

[0048] The silicon source, alkali source, aluminum source and template agent in step (1) of the present invention have a wide range of choices, and the above raw materials are conventionally selected in the art. The above raw materials should generally be mixed into a uniform colloid by corresponding means, for example, by stirring.

[0049] According to a preferred embodiment of the present invention, the silicon source is selected from at least one of silica sol, white carbon black, fumed silica, water glass and tetraethyl orthosilicate; more preferably, it is silica sol.

[0050] According to a preferred embodiment of the present invention, the alkali source is selected from alkaline metal salts, preferably at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide; more preferably sodium hydroxide.

[0051] According to a preferred embodiment of the present invention, the aluminum source is selected from at least one of pseudo-boehmite, aluminum sulfate, aluminum isopropoxide and sodium aluminate; and pseudo-boehmite is further preferred.

[0052] According to a preferred embodiment of the present invention, the template is selected from at least one of ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-hexanediamine, hexamethylammonium bromide, hexamethylammonium chloride and hexamethylammonium hydroxide, and is further preferably selected from at least one of 1,6-hexanediamine, hexamethylammonium bromide, hexamethylammonium chloride and hexamethylammonium hydroxide.

[0053] According to a preferred embodiment of the present invention, the conditions of the crystallization reaction in step (2) include: reacting at 20°C-50°C for 6-20h, reacting at 50°C-80°C for 12-34h, and then reacting at 80°C-180°C for 48-70h.

[0054] According to a preferred embodiment of the present invention, in step (4), the acidification precipitation comprises: adding acid to the molecular sieve mother liquor to adjust the pH value to 5-7, preferably 5-6.5.

[0055] Preferably, the acidification deposition time is 0.5-4h.

[0056] The molecular sieve mother liquor obtained by the above preferred embodiment has the characteristic of an appropriate amount of seed crystals, and is further recycled to step (1) to participate in the reaction, which is conducive to the formation of a molecular sieve with a high specific surface area.

[0057] In the present invention, there is no specific limitation on the type of the acid described in step (4), as long as the above-mentioned pH adjustment effect can be achieved. Preferably, the acid can be at least one of hydrochloric acid, nitric acid, ammonium nitrate and ammonium chloride.

[0058] According to a preferred embodiment of the present invention, the seed crystal is a ZSM-48 molecular sieve seed crystal, and the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve seed crystal is not less than 40, preferably 45 to 500. The silicon-aluminum ratio in the ZSM-48 molecular sieve seed crystal mainly depends on the feeding and preparation method of the silicon source and aluminum source in the raw material.

[0059] In the XRD diffraction pattern of the ZSM-48 molecular sieve raw powder synthesized by the prior art method after calcination, the peak position of the diffraction peak is generally at 7.5°, 21.2°, 22.8°, and 31.3° at 2θ angles, wherein the diffraction peak at 21°-22° is the highest, while the diffraction peak intensity at 7°-8° is weaker. The researchers of the present invention have found that by adopting a specific synthesis method, the preferred ZSM-48 molecular sieve seed of the present invention can be prepared, and in the X-ray diffraction pattern after calcination, the relative peak height of the diffraction peak at 7°-8° at 2θ angle is significantly higher than the relative peak height of the diffraction peak at 7°-8° in the molecular sieve obtained by the prior art.

[0060] According to a preferred embodiment of the present invention, the peak height of the diffraction peak with a 2θ angle of 21°-22° is taken as the reference value, and the peak height of the diffraction peak with a 2θ angle of 7°-8° in the present invention is not less than 70% of the reference value, and further preferably, the peak height of the diffraction peak with a 2θ angle of 7°-8° is 70%-135% of the reference value; for example, the lower limit of the peak height range of the diffraction peak of 7°-8° can be 75%, 80%, 90% of the reference value, etc., and the upper limit of the peak height range of the diffraction peak of 7°-8° can be 135%, 120%, 110%, 100% of the reference value, etc. Due to the influence of factors such as samples and instruments, the specific peak position of the 2θ angle in the present invention may have a deviation of ±0.5°. The purpose of the calcination is to remove impurities such as the template in the molecular sieve raw powder to obtain more accurate XRD characterization results, and will not substantially affect the diffraction peaks in the XRD spectrum of the molecular sieve itself. Therefore, the calcination conditions are based on the removal of impurities. For example, it can be calcined at 400-700°C for 1-8h. The ZSM-48 molecular sieve seeds prepared in Preparation Examples 1-1 and 1-3 of the present invention are calcined at 600°C for 4h before characterization.

[0061] According to a preferred embodiment of the present invention, the method for preparing the seed crystal includes contacting a reaction mixture under crystallization conditions, wherein the reaction mixture includes a silicon source, an alkali source, an aluminum source, a template and water. The selection range of the silicon source, alkali source, aluminum source and template can be the same as above, and will not be repeated here; the types of the selected silicon source, alkali source, aluminum source and template can be the same as or different from the types of the silicon source, alkali source, aluminum source and template described in the above molecular sieve preparation process. Preferably, in the seed crystal preparation process, the content of each component in the reaction mixture satisfies the following relationship:

[0062] R / SiO 2 =0.01-0.50, more preferably 0.01-0.3;

[0063] H 2 O / SiO 2 =5-50, more preferably 5-20;

[0064] M+ / SiO 2 =0.01-0.50, more preferably 0.01-0.15;

[0065] Al 2 O 3 / SiO 2 =0-0.02; more preferably 0.01-0.017;

[0066] Wherein, R represents the template, M + Indicates alkaline source.

[0067] According to a preferred embodiment of the present invention, the method for preparing the seed crystal mainly includes three steps of crystallization, and the temperature of each crystallization is higher than the temperature of the previous crystallization. Specifically, the first step crystallization temperature t 1 Satisfy 15℃≤t 1 <50℃, preferably at room temperature, more preferably 20℃≤t 1 ≤45℃, the first step crystallization time is 5-24h, preferably 6-15h; the second step crystallization temperature t 2 Satisfy 50℃≤t 2 <100℃, preferably 60℃≤t 2 ≤80℃, the second step crystallization time is 0.5-36h, preferably 5-30h; the third step crystallization temperature t 3 Satisfy 100℃≤t 3 ≤200℃, preferably 120℃≤t 3 ≤190°C, the third step crystallization time is 10-96h, preferably 20-80h.

[0068] According to a preferred embodiment of the present invention, the process of preparing the seed crystals further includes performing solid-liquid separation on the crystallization product to obtain the seed crystals.

[0069] The seed crystals obtained by the above preferred embodiment are used for the preparation of the above molecular sieve, which is conducive to obtaining small-grain products.

[0070] In order to obtain the molecular sieve raw powder of the present invention, the reaction system after the above crystallization can be further subjected to solid-liquid separation and drying and other operations. The methods and conditions for solid-liquid separation and drying are conventional operations in the art and are not repeated here. For example, the reaction product can be filtered and then dried at 120° C. for 6 hours to obtain the molecular sieve.

[0071] The third aspect of the present invention provides the use of the ZSM-48 molecular sieve described in the first aspect or the ZSM-48 molecular sieve prepared by the method described in the second aspect in a hydrogenation isomerization reaction.

[0072] The present invention will be described in detail below through examples.

[0073] In the following preparation examples, a Bruker D5005 diffractometer was used to perform XRD characterization on the samples, Cu Kα radiation (λ=0.154nm), tube voltage 40kV, tube current 30mA, scanning range 5°-35°, step 0.013°, 1 step per second. A Hitachi S-4800 scanning electron microscope (SEM) was used to characterize the sample morphology and size, with an acceleration voltage of 20kV.

[0074] The composition of the samples was determined using a 3271E X-ray fluorescence spectrometer (XRF) produced by Rigaku Corporation. The sample preparation method was the tablet pressing method, and the measurement conditions were an end-window rhodium target, a tube voltage of 50 kV, and a tube current of 50 mA.

[0075] The dry basis of the molecular sieve and pseudo-boehmite in the test examples refers to the weight after calcination at 600° C. for 2 h.

[0076] The pore structure parameters of the product, such as specific surface area and pore volume, were measured by nitrogen adsorption and BET method.

[0077] The following preparation examples are used to illustrate the preparation of seed crystals.

[0078] Preparation Example 1-1

[0079] Aluminum sulfate, hexamethyldiamine hydroxide (HMOH), sodium hydroxide and deionized water were mixed in a certain proportion, stirred for 30 minutes and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMOH):n(Na + ):n(H2 O):n(SiO 2 )=0.01:0.03:0.3:8:1, the mixture was transferred into a crystallization kettle, and crystallized for 6 hours at room temperature with stirring at a speed of 400rpm; then crystallized for 24 hours at 80℃, and then heated to 180℃ for crystallization for 48 hours. After the crystallization, the solid product was filtered and dried at 120℃ for 6 hours, and the obtained product was seed crystal A1. After the crystallization, the solid product was filtered and dried, and the obtained product was seed crystal A1. After the seed crystal A1 was calcined at 600℃ for 4 hours, the XRD diffraction peak was Figure 1 .

[0080] Preparation Example 1-2

[0081] Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide and deionized water were mixed in a certain proportion, stirred for 30 minutes and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.004:0.03:0.3:21:1, the mixture was transferred into a crystallization kettle, and crystallized for 12 hours at room temperature with stirring at a stirring speed of 350rpm; crystallized for 12 hours at 60°C and for 48 hours at 160°C. After the crystallization, the product was filtered and dried at 120°C for 6 hours. After the crystallization, the product obtained by filtering and drying is seed crystal A2.

[0082] Preparation Example 1-3

[0083] Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide and deionized water were mixed in a certain proportion, stirred for 30 minutes and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.004:0.03:0.3:21:1, the mixture was transferred into a crystallization kettle, and crystallized for 12 hours under stirring at room temperature, with a stirring speed of 350rpm; crystallized for 60 hours at 170℃, and the product obtained by filtering and drying after the crystallization was seed A3. After calcining seed A3 at 600℃ for 4 hours, XRD showed Figure 2 .

[0084] The following preparation example is used to illustrate the preparation of ZSM-48 molecular sieve.

[0085] Preparation Example 2-1

[0086] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.01:0.03:0.3:10:1. The added mass percentage of molecular sieve mother liquor accounts for 30% of the total mass percentage of the molecular sieve mother liquor and water in step (1). 2 25% by mass of ZSM-48 seed crystals A1;

[0087] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0088] (3) After the crystallization is completed, filter to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and return the molecular sieve mother liquor to step (1);

[0089] After drying at 120°C for 6 hours, the product ZSM-48 molecular sieve was obtained and recorded as Z-1. The XRF analysis results of the silicon-aluminum ratio and the specific surface area of ​​the prepared ZSM-48 molecular sieve are shown in Table 1, and the scanning electron microscope image is shown in Figure 3 Its morphology is ellipsoidal, the particle major diameter is 300-700nm, and the ratio of major diameter to minor diameter is about 1.1-1.4:1.

[0090] Preparation Example 2-2

[0091] (1) Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.004:0.03:0.3:20:1, the added mass percentage of molecular sieve mother liquor accounts for 20% of the total mass percentage of the molecular sieve mother liquor and water in step (1), and SiO 2 15% by mass of ZSM-48 seeds A2;

[0092] (2) transferring the above mixture into a crystallization kettle, crystallizing at 40°C for 12 h, at 80°C for 10 h, and at 170°C for 48 h;

[0093] (3) After the crystallization is completed, filter to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and return the molecular sieve mother liquor to step (1);

[0094] The product ZSM-48 molecular sieve was obtained by drying at 120°C for 6 hours and was recorded as Z-2. The XRF analysis results and specific surface area data of the prepared ZSM-48 molecular sieve are shown in Table 1. Its morphology is ellipsoidal, the particle major diameter is 300-600nm, and the ratio of major diameter to minor diameter is about 1.1-1.4:1.

[0095] Preparation Example 2-3

[0096] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing an acidified molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.018:0.03:0.3:30:1, the added mass percentage of molecular sieve mother liquor accounts for 30% of the total mass percentage of the molecular sieve mother liquor and water in step (1), and SiO 2 25% by mass of ZSM-48 seed crystals A1;

[0097] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0098] (3) After the crystallization is completed, the ZSM-48 molecular sieve and the molecular sieve mother liquor are filtered to obtain, and the molecular sieve mother liquor is acidified and precipitated. The acidification process is to adjust the pH value of the mother liquor to 6.2 with ammonium chloride, stand for 2 hours, and return the filtrate obtained by filtration to step (1);

[0099] The product ZSM-48 molecular sieve was obtained by drying at 120°C for 6 hours and was recorded as Z-3. The XRF analysis results and specific surface area data of the obtained ZSM-48 molecular sieve are shown in Table 1. Its morphology is ellipsoidal, the particle major diameter is 300-600nm, and the ratio of major diameter to minor diameter is about 1.1-1.5:1.

[0100] Preparation Example 2-4

[0101] (1) Sodium aluminate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na +):n(H 2 O):n(SiO 2 )=0.018:0.03:0.3:20:1, the added mass percentage of molecular sieve mother liquor accounts for 20% of the total mass percentage of the molecular sieve mother liquor and water in step (1), and SiO 2 15% by mass of ZSM-48 seeds A2;

[0102] (2) transferring the above mixture into a crystallization kettle and crystallizing at 40°C for 12 h, at 80°C for 6 h, and at 170°C for 48 h;

[0103] (3) After the crystallization is completed, the ZSM-48 molecular sieve and the molecular sieve mother liquor are filtered to obtain, and the molecular sieve mother liquor is acidified and precipitated. The acidification process is to adjust the pH value of the mother liquor to 5.6 with ammonium chloride, stand for 3 hours, and return the filtrate obtained by filtration to step (1);

[0104] The product ZSM-48 molecular sieve was obtained by drying at 120°C for 6 hours and was recorded as Z-4. The XRF analysis results and specific surface area data of the obtained ZSM-48 molecular sieve are shown in Table 1. Its morphology is ellipsoidal, the particle major diameter is 400-700nm, and the ratio of major diameter to minor diameter is about 1.1-1.4:1.

[0105] Preparation Example 2-5

[0106] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.0125:0.03:0.3:30:1. The added mass percentage of molecular sieve mother liquor accounts for 15% of the total mass percentage of the molecular sieve mother liquor and water in step (1). 2 15% by mass of ZSM-48 seed crystals A1;

[0107] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0108] (3) After the crystallization is completed, filter to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and return the molecular sieve mother liquor to step (1);

[0109] The product ZSM-48 molecular sieve was obtained by drying at 120°C for 6 hours and was recorded as Z-5. The XRF analysis results of the silicon-aluminum ratio and the specific surface area of ​​the prepared ZSM-48 molecular sieve are shown in Table 1. Its morphology is ellipsoidal, the particle major diameter is 300-700nm, and the ratio of major diameter to minor diameter is about 1.1-1.4:1.

[0110] Preparation Example 2-6

[0111] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.0125:0.03:0.3:30:1. The mass percentage of the added molecular sieve mother liquid to the total mass percentage of the molecular sieve mother liquid and water in step (1) is 20%. 2 20% by mass of ZSM-48 seed crystals A1;

[0112] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0113] (3) After the crystallization is completed, filter to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and return the molecular sieve mother liquor to step (1);

[0114] The product ZSM-48 molecular sieve was obtained by drying at 120°C for 6 hours and was recorded as Z-6. The XRF analysis results of the silicon-aluminum ratio and the specific surface area of ​​the prepared ZSM-48 molecular sieve are shown in Table 1. Its morphology is ellipsoidal, the particle major diameter is 300-700nm, and the ratio of major diameter to minor diameter is about 1.1-1.4:1.

[0115] Preparation Example 2-7

[0116] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.0125:0.02:0.2:20:1. The mass percentage of the added molecular sieve mother liquid to the total mass percentage of the molecular sieve mother liquid and water in step (1) is 20%.2 20% by mass of ZSM-48 seed crystals A1;

[0117] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0118] (3) After the crystallization is completed, filter to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and return the molecular sieve mother liquor to step (1);

[0119] The product ZSM-48 molecular sieve was obtained by drying at 120°C for 6 hours and was recorded as Z-7. The XRF analysis results of the silicon-aluminum ratio and the specific surface area of ​​the prepared ZSM-48 molecular sieve are shown in Table 1. Its morphology is ellipsoidal, the particle major diameter is 300-700nm, and the ratio of major diameter to minor diameter is about 1.1-1.4:1.

[0120] Comparative Preparation Example 1

[0121] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.0125:0.03:0.3:30:1. Add SiO 2 The mass percentage of the added molecular sieve mother liquid is 20% of the total mass percentage of the molecular sieve mother liquid and water in step (1);

[0122] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0123] (3) After the crystallization is completed, the ZSM-48 molecular sieve DZ-1 is obtained by filtering and drying. The XRF analysis results and specific surface area data of the obtained ZSM-48 molecular sieve are shown in Table 1. Its morphology is rod-shaped, and the ratio of the length to the short diameter is about 7:1.

[0124] Comparative Preparation Example 2

[0125] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H2 O):n(SiO 2 )=0.004:0.03:0.3:30:1. Add SiO 2 25% by mass of ZSM-48 seed crystals A3;

[0126] (2) The mixture was transferred into a crystallization reactor, stirred at room temperature for 6 h, crystallized at 80 °C for 24 h, and crystallized at 170 °C for 48 h;

[0127] (3) After the crystallization is completed, the ZSM-48 molecular sieve DZ-2 is obtained by filtering and drying. The XRF analysis results and specific surface area data of the obtained ZSM-48 molecular sieve are shown in Table 1. Its morphology is rod-shaped, and the ratio of the length to the short diameter is about 5:1.

[0128] Comparative Preparation Example 3

[0129] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2 )=0.018:0.03:0.3:30:1. Add SiO 2 The mass percentage of the added molecular sieve mother liquid is 20% of the total mass percentage of the molecular sieve mother liquid and water in step (1);

[0130] (2) transferring the above mixture into a crystallization reactor and crystallizing at 170° C. for 48 h;

[0131] (3) After the crystallization is completed, the ZSM-48 molecular sieve DZ-3 is obtained by filtration and drying. The XRF analysis results of the prepared ZSM-48 molecular sieve DZ-3 are rod-shaped, and the specific surface area and other data are shown in Table 1. Its morphology is rod-shaped, and the ratio of the length to the short diameter is about 6:1.

[0132] Comparative Preparation Example 4

[0133] (1) Aluminum sulfate, hexamethyldiamine chloride (HMCl), sodium hydroxide, and deionized water containing molecular sieve mother liquor were mixed in a certain proportion, stirred for 30 minutes, and then silica sol was added. The molar ratio of each substance was n(Al 2 O 3 ):(HMCl):n(Na + ):n(H 2 O):n(SiO 2)=0.018:0.03:0.3:30:1. Add SiO 2 5% by weight of ZSM-48 seed crystals A1. The added weight of the molecular sieve mother liquid accounts for 20% by weight of the total weight of the molecular sieve mother liquid and water in step (1);

[0134] (2) transferring the above mixture into a crystallization reactor and crystallizing at 170° C. for 48 h;

[0135] (3) After the crystallization is completed, the ZSM-48 molecular sieve DZ-4 is obtained by filtration and drying. DZ-4 is rod-shaped. The XRF analysis results and specific surface area data of the obtained ZSM-48 molecular sieve are shown in Table 1. Its morphology is rod-shaped, and the ratio of the length to the short diameter is about 7:1.

[0136] Test Example 1

[0137] 100 g of the Z-1 molecular sieve prepared in Preparation Example 1 was mixed with 100 g of pseudo-boehmite, extruded and dried to obtain a carrier.

[0138] Pour 1 gram of tetraammine dichloroplatinum (containing 57.3% Pt by mass) into 100 grams of deionized water and stir until uniform. Pour 100 grams of the carrier into the above solution and soak at room temperature for 4 hours. Subsequently, the above catalyst precursor is dried at 120°C for 4 hours. Then it is calcined under the condition of passing air flow, the calcination temperature is 450°C, and the time is 4 hours. The semi-finished catalyst is placed in a hydrogen atmosphere again and reduced at 400°C for 4 hours to obtain a catalyst. The obtained catalyst is named IC-1.

[0139] 50g of catalyst IC-1 was loaded into a high-pressure hydrogenation reactor. Hydrocracking tail oil was injected into the reactor from top to bottom for reaction. The reaction conditions were shown in Table 2 below, and the analysis data of the hydrocracking tail oil were shown in Table 3. After the reaction, the product was distilled to remove light components less than 370 degrees, and the components greater than 370 degrees were analyzed and the yield was calculated. The results are shown in Table 4.

[0140] Test Example 2-7

[0141] The method in Test Example 1 was followed, but the molecular sieves were replaced with Z-2 to Z-7. The prepared catalysts were named IC-2 to IC-7, and the test results are shown in Table 4.

[0142] Test Case 8

[0143] The method in Test Example 1 was followed, except that the amount of Z-1 molecular sieve was 50 g. The obtained catalyst was named IC-8, and the test results are shown in Table 4.

[0144] Test Example 9

[0145] The method in Test Example 1 was followed, except that the amount of tetraammine dichloroplatinum was 0.5 g. The obtained catalyst was named IC-9, and the test results are shown in Table 4.

[0146] Comparative test examples 1-4

[0147] The method in Test Example 1 was followed, except that the molecular sieves were replaced with DZ-1 to DZ-4. The obtained catalysts were named DIC-1 to DIC-4, and the test results are shown in Table 4.

[0148] Table 1

[0149]

[0150] Table 2 Evaluation conditions

[0151]

[0152]

[0153] Table 3 Hydrocracking tail oil analysis results

[0154] Analyze Project Analyze the data Analytical methods <![CDATA[Density at 20°C / (kg / m 3 )]]> 843.6 SH / T0604-2000 <![CDATA[Kinematic viscosity / (mm 2 / s)]]> 80℃ 7.021 GB / T 265-88 100℃ 4.664 GB / T 265-88 Pour point / ℃ +42 SH / T 0771-2005 Nitrogen mass fraction / (μg / g) <1 NB / SH / T 0704-2010 Sulfur mass fraction / (μg / g) 3 SH / T 0842-2010

[0155] Table 4 Evaluation results

[0156]

[0157]

[0158] It can be seen from the results of the above preparation examples and test examples that the ZSM-48 molecular sieve prepared by the present invention has an ellipsoidal morphology and a large specific surface area. When further applied to isomerization dewaxing of hydrocracking tail oil, the product yield and viscosity index are higher.

[0159] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A ZSM-48 molecular sieve, wherein the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve is not less than 40, and the specific surface area of ​​the ZSM-48 molecular sieve is 235-280m 2 / g, the ZSM-48 molecular sieve has an ellipsoidal grain shape, a major diameter not exceeding 700nm and a major to minor diameter ratio of 1-3:1; The ZSM-48 molecular sieve is prepared by the following method: (1) Providing a mixture containing a silicon source, an alkali source, an aluminum source, a template, water, a molecular sieve mother liquor and a seed crystal; (2) subjecting the mixture to a crystallization reaction; the conditions of the crystallization reaction include: React at 20°C-50°C for 1-20h, at 50°C-80°C for 1-34h, and then at 80°C-180°C for 1-70h; (3) The mixture obtained from the crystallization reaction in step (2) is subjected to solid-liquid separation to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and the molecular sieve mother liquor is returned to step (1); The method further comprises an optional step (4), which comprises: acidifying and precipitating the molecular sieve mother liquor, and then performing solid-liquid separation, and returning the obtained filtrate to step (1); The mass percentage of the added seed crystals in step (1) is 15%-30% of the mass percentage of the silicon source, where the silicon source is calculated as SiO2; The seed crystals are ZSM-48 molecular sieve seed crystals, and the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve seed crystals is 45-500.

2. The molecular sieve according to claim 1, wherein The aspect ratio of ZSM-48 molecular sieve is 1-2:

1.

3. The molecular sieve according to claim 1 or 2, wherein: The pore volume of ZSM-48 molecular sieve is 0.20-0.30 ml / g.

4. The molecular sieve according to claim 1 or 2, wherein: The crystal size of the ZSM-48 molecular sieve is 300-700 nm.

5. The molecular sieve according to claim 4, wherein The crystal size of the ZSM-48 molecular sieve is 400-600 nm.

6. A method for preparing a ZSM-48 molecular sieve, the method comprising the following steps: (1) Providing a mixture containing a silicon source, an alkali source, an aluminum source, a template, water, a molecular sieve mother liquor and a seed crystal; (2) subjecting the mixture to a crystallization reaction; the conditions of the crystallization reaction include: reacting at 20°C-50°C for 1-20 hours, reacting at 50°C-80°C for 1-34 hours, and then reacting at 80°C-180°C for 1-70 hours; (3) The mixture obtained from the crystallization reaction in step (2) is subjected to solid-liquid separation to obtain ZSM-48 molecular sieve and molecular sieve mother liquor, and the molecular sieve mother liquor is returned to step (1); The method further comprises an optional step (4), which comprises: acidifying and precipitating the molecular sieve mother liquor, and then performing solid-liquid separation, and returning the obtained filtrate to step (1); The mass percentage of the added seed crystals in step (1) is 15%-30% of the mass percentage of the silicon source, where the silicon source is calculated as SiO2; The seed crystals are ZSM-48 molecular sieve seed crystals, and the molar ratio of silicon oxide to aluminum oxide in the ZSM-48 molecular sieve seed crystals is 45-500.

7. The preparation method according to claim 6, wherein: The mass percentage of the added seed crystals in step (1) is 20-30% of the mass percentage of the silicon source.

8. The preparation method according to claim 6, wherein: The mass percentage of the added molecular sieve mother liquor in step (1) to the total mass percentage of the molecular sieve mother liquor and water in step (1) is no more than 50%.

9. The preparation method according to claim 8, wherein: The mass percentage of the added molecular sieve mother liquor in step (1) to the total mass percentage of the molecular sieve mother liquor and water in step (1) is 10-30%.

10. The preparation method according to claim 6, wherein: The composition of each component in the mixture in step (1) calculated by molar amount satisfies the following relationship: R / SiO2=0.01-0.40; M + / SiO2=0.01-0.40; Al2O3 / SiO2=0-0.02; H2O / SiO2=5-30; Wherein, SiO2 refers to SiO2 in the silicon source, R represents the template, and M + Indicates alkaline source.

11. The preparation method according to claim 10, wherein: The composition of each component in the mixture in step (1) calculated by molar amount satisfies the following relationship: R / SiO2= 0.01-0.08; M + / SiO2=0.1-0.2; Al2O3 / SiO2=0.01-0.015; H2O / SiO2=5-20; Wherein, SiO2 refers to SiO2 in the silicon source, R represents the template, and M + Indicates alkaline source.

12. The preparation method according to claim 6, wherein: The silicon source is selected from at least one of silica sol, white carbon black, fumed silica, water glass and tetraethyl orthosilicate.

13. The preparation method according to claim 6, wherein: The alkalinity source is selected from alkaline metal salts.

14. The preparation method according to claim 13, wherein: The alkali source is selected from at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide.

15. The preparation method according to claim 6, wherein: The aluminum source is selected from at least one of pseudo-boehmite, aluminum sulfate, aluminum isopropoxide and sodium aluminate.

16. The preparation method according to claim 6, wherein: The template agent is selected from at least one of ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-hexanediamine, hexamethylammonium bromide, hexamethylammonium chloride and hexamethylammonium hydroxide.

17. The preparation method according to any one of claims 6 to 16, wherein: The conditions of the crystallization reaction in step (2) include: reacting at 20°C-50°C for 6-20h, reacting at 50°C-80°C for 12-34h, and then reacting at 80°C-180°C for 48-70h.

18. The preparation method according to any one of claims 6 to 16, wherein: In step (4), the acidification precipitation comprises: adding acid to the molecular sieve mother liquor and adjusting the pH value to 5-7.

19. The preparation method according to claim 18, wherein: In step (4), the acidification precipitation comprises: adding acid to the molecular sieve mother liquor and adjusting the pH value to 5-6.

5.

20. The preparation method according to any one of claims 6 to 16, wherein: The acidification deposition time is 0.5-4h.

21. The preparation method according to any one of claims 6 to 16, wherein: The seed crystal is a ZSM-48 molecular sieve seed crystal. In the X-ray diffraction pattern of the ZSM-48 molecular sieve seed crystal after calcination, the peak height of the diffraction peak with a 2θ angle of 21°-22° is used as the reference value, and the peak height of the diffraction peak with a 2θ angle of 7°-8° is not less than 70% of the reference value.

22. The preparation method according to claim 21, wherein The seed crystal is a ZSM-48 molecular sieve seed crystal. In the X-ray diffraction pattern of the calcined ZSM-48 molecular sieve seed crystal, the peak height of the diffraction peak with a 2θ angle of 21°-22° is used as the reference value, and the peak height of the diffraction peak with a 2θ angle of 7°-8° is 75%-135% of the reference value.

23. The preparation method according to claim 21, wherein The method for preparing the seed crystal comprises contacting a reaction mixture under crystallization conditions, wherein the reaction mixture comprises a silicon source, an alkali source, an aluminum source, a template and water, and the crystallization conditions comprise: crystallizing at a temperature t1 for 5-24 hours, crystallizing at a temperature t2 for 0.5-36 hours, and crystallizing at a temperature t3 for 10-96 hours, 15°C≤t1<50°C, 50°C≤t2<100°C, and 100°C≤t3≤200°C.

24. Use of the ZSM-48 molecular sieve according to any one of claims 1 to 5 or the ZSM-48 molecular sieve prepared by the method according to any one of claims 6 to 23 in a hydroisomerization reaction.

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