Silicon-modified molecular sieve, method for preparing the same, and method for preparing 2,6-diisopropyl naphthalene

Abstract

The application provides a silicon modified molecular sieve, a preparation method thereof and a method for preparing 2,6-diisopropyl naphthalene. The preparation method of the silicon modified molecular sieve comprises the following steps: carrying out silicon treatment on a molecular sieve by immersing the molecular sieve in a modification liquid comprising a silicon source, removing a solvent, drying, and calcining to obtain the silicon modified molecular sieve; and the molecular sieve comprises at least one of MCM-56 molecular sieve, MCM-22 molecular sieve and MP01 molecular sieve. The silicon modified molecular sieve provided by the application is used in the reaction of naphthalene and / or 2-isopropyl naphthalene with propylene to prepare 2,6-diisopropyl naphthalene, and has the advantages of high naphthalene source conversion rate and high 2,6-diisopropyl naphthalene selectivity.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalyst technology, specifically relating to a silicon-modified molecular sieve and its preparation method, and a method for preparing 2,6-diisopropylnaphthalene. Background Technology

[0002] 2,6-Diisopropylnaphthalene (2,6-DIPN) is an important organic chemical raw material with advantages such as being colorless, odorless, having a high boiling point, low toxicity, low freezing point, and strong fuel solubility. 2,6-Diisopropylnaphthalene (2,6-DIPN) can be used to synthesize 2,6-naphthalenedicarboxylic acid, which can be used to produce polyethylene terephthalate (PEN) and thermally oriented liquid crystal polymers (LCPs). PEN, in particular, possesses unique properties such as heat resistance, mechanical properties, gas barrier properties, chemical stability, and radiation resistance, and is widely used in electronic devices, high-performance films, food packaging films, insulating materials, and aerospace. Currently, the bottleneck for the large-scale application of PEN lies in the cumbersome preparation process and high production cost of its key raw material, 2,6-diisopropylnaphthalene.

[0003] my country has abundant naphthalene resources. Using inexpensive and plentiful naphthalene as a raw material, the synthesis of 2,6-diisopropylnaphthalene via the alkylation reaction of naphthalene and propylene can broaden the raw material sources for PEN synthesis, increase the added value of naphthalene and propylene, and shorten the process route. Due to the numerous isomers of 2,6-diisopropylnaphthalene with similar boiling points, separation is very difficult. Therefore, improving the selectivity of 2,6-diisopropylnaphthalene is key to its preparation from naphthalene. Existing technologies disclose several methods for preparing 2,6-diisopropylnaphthalene from naphthalene, but they generally suffer from the problem that the naphthalene conversion rate or the 2,6-diisopropylnaphthalene selectivity cannot simultaneously meet high requirements, resulting in generally unsatisfactory yields. For example, CN107954812A discloses a method for the alkylation of naphthalene with propylene to generate 2,6-DIPN, using a silanized modified ZSM-5 / ZSM-12 composite molecular sieve as a catalyst, achieving a naphthalene conversion rate of 31% and a 2,6-DIPN selectivity of 41%. Patent JP1994080591A discloses a method for using silicon-modified molecular sieves for β,β'-dialkylnaphthalene. The molecular sieves used can be ZSM-5, Y-type zeolite, X-type zeolite, or mordenite. Although silicon-modified molecular sieves improve the selectivity of β,β'-dialkylnaphthalene, the conversion rate of naphthalene or monoalkylnaphthalene is very low (<20%). Moreover, although the total selectivity of β,β'-dialkylnaphthalene is above 80%, the actual selectivity of 2,6-dialkylnaphthalene is not very high because the proportion of 2,7-dialkylnaphthalene in β,β'-dialkylnaphthalene is very high.

[0004] Therefore, it is very meaningful to provide a method for preparing 2,6-diisopropylnaphthalene that simultaneously has high reactant conversion rate and high product selectivity. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a silicon-modified molecular sieve and its preparation method, as well as a method for preparing 2,6-diisopropylnaphthalene, to solve the technical problem in the prior art that it is impossible to simultaneously obtain high reactant conversion rate and high product selectivity in the preparation of 2,6-diisopropylnaphthalene.

[0006] The objective of this invention is mainly achieved through the following technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing a silicon-modified molecular sieve, comprising: immersing the molecular sieve in a modification solution containing a silicon source for silicon treatment, removing the solvent, drying, and calcining to obtain the silicon-modified molecular sieve;

[0008] The molecular sieve includes at least one of MCM-56 molecular sieve, MCM-22 molecular sieve, and MP01 molecular sieve.

[0009] Molecular sieves with surface-loaded SiO2 layers, such as ZSM-5 molecular sieve with a SiO2 layer, can be used as catalysts to prepare diisopropylnaphthalene. However, the problem of low feed conversion rate has persisted, and the content of 2,7-diisopropylnaphthalene in the product is basically the same as that of 2,6-diisopropylnaphthalene, resulting in unsatisfactory overall selectivity for 2,6-diisopropylnaphthalene. For these reasons, the use of molecular sieves with surface-loaded SiO2 layers has not been practically applied in the production of 2,6-diisopropylnaphthalene.

[0010] During their research, the inventors discovered that by employing more suitable molecular sieve types, such as MCM-56, MCM-22, or MP01 molecular sieves as the SiO2-supported matrix, they could simultaneously improve the conversion rate of naphthalene / 2-isopropylnaphthalene and the selectivity of 2,6-diisopropylnaphthalene. This is likely because MCM-56, MCM-22, and MP01 molecular sieves have pore sizes that match the molecular diameter of 2,6-diisopropylnaphthalene, which facilitates the utilization of the pore shape-selective effect of the molecular sieves, thereby increasing the selectivity of 2,6-diisopropylnaphthalene.

[0011] In this invention, solvent removal can be achieved by commonly used methods such as evaporating the solvent to remove it from the system.

[0012] According to some embodiments of the present invention, the silicon source includes at least one of silicon tetrachloride, triethoxysilane, and tetraisopropyl orthosilicate.

[0013] According to some embodiments of the present invention, the silicon source includes silicon tetrachloride.

[0014] In this invention, the selection of the silicon source is another key factor in improving the catalytic performance of silicon-modified molecular sieve catalysts. Molecular sieve catalysts prepared by modifying MCM-56, MCM-22, and MP01 molecular sieves with silicon tetrachloride as the silicon source exhibit higher reactant conversion and selectivity for 2,6-diisopropylnaphthalene compared to those prepared using other silicon sources. This may be because when loading SiO2 onto the molecular sieve surface, it is necessary for SiO2 to effectively cover the acid sites on the outer surface of the molecular sieve while ensuring the unobstructed flow of the molecular sieve pores. When the molecular size of the silicon source is larger than the pore size of the molecular sieve, the silicon source mainly deposits on the outer surface of the molecular sieve. While covering the acidic sites on the outer surface of the molecular sieve, it also coats the area near the pore openings, thus reducing their size. When silicon tetrachloride (SiCl4) is selected as the silicon source for silicon modification, since the molecular diameter of silicon tetrachloride is smaller than the pore size of the molecular sieve used, silicon tetrachloride modification can, on the one hand, cover the acidic sites on the outer surface and reduce the occurrence of surface isomerization reaction; on the other hand, silicon tetrachloride can enter the molecular sieve pores to adjust the pore size, which is more conducive to the diffusion of linear 2,6-diisopropylnaphthalene in the pores, thereby improving the selectivity of 2,6-diisopropylnaphthalene.

[0015] According to some embodiments of the present invention, the ratio of the mass of silicon source (calculated as SiO2) to the sum of the masses of silicon source and molecular sieve (calculated as SiO2) is (0.5 to 20): 100, preferably (1 to 10): 100.

[0016] According to some embodiments of the present invention, the modified liquid further includes a solvent.

[0017] According to some embodiments of the present invention, the solvent includes at least one of benzene, petroleum ether, toluene, and alcohol solvents.

[0018] According to some embodiments of the present invention, the solvent includes at least one of benzene, petroleum ether, and toluene.

[0019] According to some embodiments of the present invention, the volume ratio of the silicon source to the solvent is 1:(5-100), preferably 1:(10-50).

[0020] According to some embodiments of the present invention, the temperature of the silicon treatment is (30-90)°C, preferably (30-60)°C; the time of the silicon treatment is (0.5-12)h, preferably (1-5)h.

[0021] According to some embodiments of the present invention, the drying temperature is 60-140°C, preferably 80-120°C; the silicon treatment time is 6-18 hours, preferably 8-15 hours.

[0022] According to some embodiments of the present invention, the calcination includes: first heating to 240-300°C and calcining for 1-3 hours; then heating to 350-550°C and calcining for 3-8 hours.

[0023] Secondly, the present invention provides a silicon-modified molecular sieve, which is prepared by the preparation method described in the first aspect.

[0024] According to some embodiments of the present invention, the loading of SiO2 in the silicon-modified molecular sieve is 0.5wt% to 20wt%, preferably 1wt% to 10wt%.

[0025] Thirdly, the present invention provides a method for preparing 2,6-diisopropylnaphthalene, comprising: reacting a naphthalene source including naphthalene and / or 2-isopropylnaphthalene with propylene in the presence of the silicon-modified molecular sieve described in the second aspect to obtain 2,6-diisopropylnaphthalene.

[0026] According to some embodiments of the present invention, the molar ratio of the naphthalene source to propylene is 1:1 to 1:5, preferably 1:1 to 1:3.

[0027] According to some embodiments of the present invention, the mass of the silicon-modified molecular sieve is 0.2% to 15% of the mass of the naphthalene source, preferably 1% to 10%.

[0028] According to some embodiments of the present invention, the reaction temperature is 150–300°C, preferably 170–250°C.

[0029] According to some embodiments of the present invention, the pressure of the reaction is 0.5 to 5 MPa, preferably 1 to 3.5 MPa.

[0030] According to some embodiments of the present invention, the reaction is carried out in a reactor, which is selected from any one of a batch reactor, a fixed-bed reactor, and a slurry-bed reactor.

[0031] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0032] The silicon-modified catalyst provided by this invention is used in the reaction of naphthalene and / or 2-isopropylnaphthalene with propylene to prepare 2,6-diisopropylnaphthalene, and has the advantages of high naphthalene source conversion and high selectivity for 2,6-diisopropylnaphthalene. Detailed Implementation

[0033] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0034] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0035] The qualitative and quantitative analyses of the products in the various embodiments and comparative examples of this invention were performed offline using a Shimadzu GC-2030 gas chromatograph, with separation using an HP-INNOWAX column and detection analysis using a flame ionization detector.

[0036] Naphthalene conversion rate = (number of moles of naphthalene converted / total number of moles of naphthalene) × 100%.

[0037] DIPN selectivity = (number of moles of DIPN in the product / total number of moles of the product) × 100%.

[0038] 2,6-DIPN selectivity = (number of moles of 2,6-DIPN in the product / total number of moles of DIPN in the product) × 100%.

[0039] 2,7-DIPN selectivity = (number of moles of 2,7-DIPN in the product) / (total number of moles of DIPN in the product) × 100%.

[0040] The MCM-56 molecular sieve, MCM-22 molecular sieve, MP01 molecular sieve, and ZSM-5 molecular sieve used in the embodiments and comparative examples of this invention are all commercially available products manufactured by Zhuoran Environmental Protection Technology (Dalian) Co., Ltd.

[0041] Example 1

[0042] (1) Silicon tetrachloride and toluene were mixed in a volume ratio of 1:10 to prepare a modified solution; MCM-56 molecular sieve was added to the modified solution. At this time, the mass ratio of silicon tetrachloride to MCM-56 molecular sieve in the modified solution (calculated as SiO2) was 2:98. The mixture was stirred at 40°C for 1 hour; then the temperature was raised to 80°C to evaporate the solvent. The resulting precursor was dried at 120°C for 10 hours, then the temperature was raised to 260°C and calcined for 1 hour; then the temperature was raised to 550°C and calcined for 4 hours to obtain silicon-modified molecular sieve. The SiO2 loading was measured to be 2 wt%.

[0043] (2) Take 6g of the above-mentioned silicon-modified MCM-56 molecular sieve and place it in a 200mL high-pressure reactor. Then add 200g of naphthalene, seal the reactor, purge it with nitrogen, pressurize it to 0.3MPa with nitrogen, heat it to 150℃, and then introduce 131.3g of gaseous propylene. Control the reaction temperature at 230℃, the reaction pressure at 3MPa, and the reaction time at 5h. The reaction results are shown in Table 1.

[0044] Example 2

[0045] (1) Silicon tetrachloride and toluene were mixed in a volume ratio of 1:20 to prepare a modification solution; MCM-56 molecular sieve was added to the above modification solution. At this time, the mass ratio of silicon tetrachloride to MCM-56 molecular sieve in the modification solution (calculated as SiO2) was 4:96. The mixture was stirred at 40°C for 4 hours; then the temperature was raised to 80°C to evaporate the solvent. The resulting precursor was dried at 100°C for 14 hours, then the temperature was raised to 280°C and calcined for 2.5 hours; then the temperature was raised to 450°C and calcined for 6 hours to obtain silicon-modified molecular sieve. The SiO2 loading was measured to be 4 wt%.

[0046] (2) Take 10g of the above-mentioned silicon-modified MCM-56 molecular sieve and place it in a 200mL high-pressure reactor. Then add 200g of naphthalene, seal the reactor, purge it with nitrogen, pressurize it to 0.3MPa with nitrogen, heat it to 170℃, and introduce 140g of gaseous propylene. Control the reaction temperature at 210℃, the reaction pressure at 2MPa, and the reaction time at 4h. The reaction results are shown in Table 1.

[0047] Example 3

[0048] (1) The preparation process of silicon modified molecular sieve is the same as in Example 1, except that MCM-56 molecular sieve is replaced with MCM-22 molecular sieve.

[0049] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0050] Example 4

[0051] (1) The preparation process of silicon modified molecular sieve is the same as in Example 1, except that MCM-56 molecular sieve is replaced with MP01 molecular sieve.

[0052] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0053] Example 5

[0054] (1) The preparation process of silicon-modified molecular sieve is the same as in Example 1, except that silicon tetrachloride is replaced with an equal volume of triethoxysilane.

[0055] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0056] Example 6

[0057] (1) The preparation process of silicon-modified molecular sieve is the same as in Example 1, except that silicon tetrachloride is replaced with an equal volume of tetraisopropyl orthosilicate.

[0058] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0059] Example 7

[0060] (1) The preparation process of silicon-modified molecular sieve is the same as in Example 1, except that toluene is replaced with an equal volume of petroleum ether.

[0061] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0062] Example 8

[0063] (1) The preparation process of silicon-modified molecular sieve is the same as in Example 1, except that toluene is replaced with an equal volume of ethanol.

[0064] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0065] Example 9

[0066] (1) The preparation process of silicon-modified molecular sieves is the same as in Example 1, except that the relative amounts of silicon tetrachloride and MCM-56 molecular sieves are changed so that the mass ratio of silicon tetrachloride to MCM-56 molecular sieves in the modification solution (calculated as SiO2) is 0.5:99.5. The SiO2 loading in the obtained silicon-modified molecular sieve is 0.5 wt%.

[0067] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0068] Example 10

[0069] (1) The preparation process of silicon-modified molecular sieve is the same as in Example 1, except that the relative amounts of silicon tetrachloride and MCM-56 molecular sieve are changed so that the mass ratio of silicon tetrachloride to MCM-56 molecular sieve in the modification solution (calculated as SiO2) is 20:80. The SiO2 loading in the silicon-modified molecular sieve is 20 wt%.

[0070] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0071] Example 11

[0072] (1) The preparation process of silicon-modified molecular sieve is the same as in Example 1, except that the precursor obtained is dried at 120°C for 10 hours and then directly heated to 550°C and calcined for 5 hours to obtain silicon-modified molecular sieve.

[0073] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0074] Comparative Example 1

[0075] 6g of MCM-56 molecular sieve was placed in a 200mL high-pressure reactor, followed by the addition of 200g of naphthalene. The reactor was sealed, purged with nitrogen, and pressurized to 0.3MPa. After heating to 150℃, 131.3g of gaseous propylene was introduced. The reaction temperature was controlled at 230℃, the reaction pressure at 3MPa, and the reaction time at 5h. The reaction results are shown in Table 1.

[0076] Comparative Example 2

[0077] (1) The preparation process of silicon modified molecular sieve is the same as in Example 1, except that “MCM-56 molecular sieve” is replaced with “ZSM-5 molecular sieve”.

[0078] (2) The reaction process for preparing 2,6-DIPN was as described in Example 1. The reaction results are shown in Table 1.

[0079] Table 1. Naphthalene conversion and product selectivity for each example and comparative example.

[0080]

[0081]

[0082] As shown in Table 1, the methods for preparing 2,6-diisopropylnaphthalene by reacting naphthalene with propylene in each embodiment of the present invention can simultaneously obtain high naphthalene conversion and high 2,6-DIPN selectivity.

[0083] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing silicon-modified molecular sieves, characterized in that, include: The molecular sieve is immersed in a modification solution containing a silicon source for silicon treatment, the solvent is removed, and the sieve is dried and calcined to obtain the silicon-modified molecular sieve. The molecular sieve includes at least one of MCM-56 molecular sieve, MCM-22 molecular sieve, and MP01 molecular sieve.

2. The preparation method according to claim 1, characterized in that, The silicon source includes at least one of silicon tetrachloride, triethoxysilane, and tetraisopropyl orthosilicate, preferably silicon tetrachloride; And / or, the ratio of the mass of silicon source (in terms of SiO2) to the sum of the masses of silicon source and molecular sieve (in terms of SiO2) is (0.5 to 20): 100, preferably (1 to 10):

100.

3. The preparation method according to claim 1 or 2, characterized in that, The modified liquid also includes a solvent; Preferred, The solvent includes at least one of benzene, petroleum ether, toluene, and alcohol solvents, preferably at least one of benzene, petroleum ether, and toluene; And / or, the volume ratio of the silicon source to the solvent is 1:(5-100), preferably 1:(10-50).

4. The preparation method according to any one of claims 1-3, characterized in that, The silicon treatment temperature is (30-90)℃, and the silicon treatment time is (0.5-12)h; And / or, the drying temperature is 60–140°C, preferably 80–120°C; And / or, the calcination includes: first heating to 240-300°C and calcining for 1-3 hours; then heating to 350-550°C and calcining for 3-8 hours.

5. A silicon-modified molecular sieve, prepared by the preparation method according to any one of claims 1-4; Preferably, the loading of SiO2 in the silicon-modified molecular sieve is 0.5wt% to 20wt%, and more preferably 1wt% to 10wt%.

6. A method for preparing 2,6-diisopropylnaphthalene, characterized in that, include: A naphthalene source, including naphthalene and / or 2-isopropylnaphthalene, reacts with propylene in the presence of the silicon-modified molecular sieve of claim 5 to obtain 2,6-diisopropylnaphthalene.

7. The method according to claim 6, characterized in that, The molar ratio of the naphthalene source to propylene is 1:1 to 1:5, preferably 1:1 to 1:

3.

8. The method according to claim 6 or 7, characterized in that, The mass of the silicon-modified molecular sieve is 0.2% to 15% of the mass of the naphthalene source, preferably 1% to 10%.

9. The method according to any one of claims 6-8, characterized in that, The reaction temperature is 150–300°C, preferably 170–250°C; And / or, the pressure of the reaction is 0.5 to 5 MPa, preferably 1 to 3.5 MPa.

10. The method according to any one of claims 6-8, characterized in that, The reaction is carried out in a reactor, which is selected from any one of a batch reactor, a fixed-bed reactor, or a slurry-bed reactor.

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