Method for synthesizing durene through alkylation of unsym-trimethylbenzene and methanol

Abstract

The invention relates to a method for synthesizing durene through alkylation of unsym-trimethylbenzene and methanol, and the method comprises the following step: under alkylation reaction conditions and in the presence of a catalyst, enabling unsym-trimethylbenzene to be in contact with methanol, wherein the catalyst comprises a modified IMF structure molecular sieve, the ratio of the amount of acid B to the amount of acid L of the modified IMF structure molecular sieve measured at 200 DEG C by a pyridine adsorption infrared method is 1.5-4.5, and the ratio of the amount of acid B to the amount of acid L measured at 350 DEG C by the pyridine adsorption infrared method is 4-5. The molecular sieve with the modified IMF structure has a relatively proper B / L value, has the advantage of improving the utilization rate of an acid center, shows optimized catalytic performance when being used for the alkylation reaction of unsym-trimethylbenzene and methanol, can improve the conversion rate of unsym-trimethylbenzene, durene selectivity and tetramethylbenzene selectivity, and has a good application prospect in the alkylation reaction of unsym-trimethylbenzene and methanol. And after a long-time reaction, the catalyst still has relatively high activity stability and can be repeatedly used.

Description

Technical Field

[0001] The present disclosure relates to the technical field of alkylation, and in particular to a method for synthesizing durene by alkylating trimethylolbenzene with methanol. Background Art

[0002] Durene is a high value-added fine chemical raw material and the main raw material for the production of pyromellitic anhydride (PMDA). PMDA and diamines such as 4,4'-diaminodiphenyl ether (ODA) are used to produce polyimide (PI). PI is an important class of polymer materials and is widely used in filter membranes, aerospace composites, electronic-grade coatings and adhesives. In recent years, the main methods for synthesizing durene are separation method and synthesis method: the separation method is to obtain polyimide from C 10 The process of purifying durene from reformed heavy aromatics or methanol synthetic oil by combining distillation and crystallization (or adsorption) is complex, with high energy consumption and low separation accuracy. The synthesis method includes chloromethylation of trimethylol, disproportionation / isomerization of trimethylol, isomerization of tetramethylol and alkylation of trimethylol. Among them, the alkylation reaction of trimethylol and methanol has attracted wide attention due to its low cost, high product yield, low energy consumption, no pollution and no corrosion.

[0003] Tao Keyi et al. from Nankai University (Tao Keyi, Zang Yaru, Jia Tongwen et al. Study on the alkylation of trimethylbenzene and methanol to tetramethylbenzene on HZSM-5 [J]. Acta Petrolei Sinica (Petroleum Processing), 1989, 5(1): 33-38) studied the reaction of HZSM-5 molecular sieve with a silicon-aluminum ratio of 38 with organic fluoride CF2Cl2 gas at 500℃ for 2min. At 320℃, the liquid space velocity was 2.93h / min. -1 , under the condition of 1:2 molar ratio of trimethylol and methanol and 25ml / min nitrogen flow rate, the conversion rate of trimethylol reached 57% and the selectivity of durene in tetramethylol isomers reached more than 90% within 4 hours in a fixed bed reactor. Studies have shown that the treatment of HZSM-5 molecular sieve with organic fluoride has the effect of adjusting acidity and reducing pore size, thus improving the shape selectivity of molecular sieve.

[0004] Wang Wei from Taiyuan University of Technology (Wang Wei. Study on the alkylation of 1,2,4-trimethylbenzene and methanol to 1,2,4,5-tetramethylbenzene catalyzed by fluoride-modified HZSM-5 molecular sieve [D]. Master's degree thesis. 1999) used in-situ synthesis, impregnation and mechanical mixing methods to modify HZSM-5 molecular sieve with a silicon-aluminum ratio of 67.4. The optimized reaction conditions were 350°C, a molar ratio of trimethylbenzene to methanol of 1:2, a nitrogen flow rate of 20 ml / min, and a pulse microreactor. The pulse was pulsed 10 times. The results showed that in the in-situ synthesis method, 0.8g of sodium fluoride was added to the silicon source, and the highest selectivity of tetramethylbenzene was 32.4%, and the conversion rate of trimethylbenzene was 15.8% at this time; the impregnation method, the molecular sieve impregnated with 27% by mass of ammonium fluoride, the highest selectivity of tetramethylbenzene was 37.3%, and the conversion rate of trimethylbenzene was 23.3% at this time; the mechanical mixing method, mixed with 8.4% by mass of ammonium fluoride, the highest selectivity of tetramethylbenzene was 37.7%, and the conversion rate of trimethylbenzene was 13.4% at this time. Studies have shown that fluorine modification has dealumination, and the dealumination effect of impregnation and mechanical mixing is more obvious, the total acid content is reduced, the lattice is polarized by F, and there are surface groups on the outer surface. Fluoride is added during the synthesis to make F - Promote the strength of B acid center, fluoride encapsulates in the pores, causing the pore size to shrink; impregnation makes F - It penetrates into the crystal pores and interacts with the pore surface at high temperature, which changes the pore structure and adsorption properties. The product adsorption and desorption rate is accelerated, which offsets the effect of the decrease in acid content. The desorption temperature peak corresponding to the weak acid center is the lowest, and the desorption temperature peak corresponding to the strong / medium-strong acid is not obvious. The total acid content decreases, the strong acid content increases, the weak acid content does not change significantly, and the medium-strong acid content is reduced by more than half. However, due to the effects of the pore dealumination and fluorine polarization mentioned above, it shows the highest activity and good selectivity. Mechanical mixing can only make F - Most of them are distributed on the outer surface of the molecular sieve crystal, with little effect on the pores, the weak acid strength is enhanced, the total acid amount is greatly reduced, the activity is reduced, the homo-tetramethylbenzene selectivity is the best, and the formation of trimethylbenzene isomers is inhibited.

[0005] Zhu Chuanfu from China University of Petroleum (East China) (Zhu Chuanfu. Study on catalyst for preparing durene by alkylation of trimethylbenzene and methanol [D]. Master's degree thesis. 2019) selected F non-metallic element to modify HZSM-5 molecular sieve catalyst with a silicon-aluminum ratio of 38 by equal volume impregnation method. The concentration of the modifier was 2% by mass and stirred at 35℃ and 200r / min with a constant temperature magnetic stirrer for 24h. Dry at 110℃ for 10h, mix evenly with Al2O3 carrier in a ratio of 7:3, dry at 110℃ for 5h, add appropriate amount of sesbania powder and mix evenly, press into tablets at 3.5MPa for 3.5min by tablet press, roast at 350℃ for 3h, crush and sieve into 20 mesh, and heat at 350℃, 0.8MPa, MB:ME=1:3, volume space velocity 4h -1Under the conditions of , the reaction was carried out in a fixed bed reactor for 4.5 hours, and the conversion rate of trimethylol was 13%, and the selectivity of tetramethylol was 38%. Studies have shown that F modification modifies the properties and number of acid centers on the surface of the molecular sieve, and the strong acid, medium-strong acid and weak acid centers are reduced, and the number of reactive active centers is reduced, resulting in a decrease in catalyst activity and a decrease in trimethylol conversion rate; the number of active centers and the strength of acid centers are reduced, and the selectivity of the alkylation reaction is improved.

[0006] Therefore, when fluoride-modified HZSM-5 molecular sieve is used as the active component of the catalyst, its trimethylolbenzene conversion rate is 10-50%, and its tetramethylolene selectivity is 30-70%, which is significantly improved compared with the tetramethylolene selectivity of HZSM-5 molecular sieve. However, the activity stability of the modified molecular sieve is poor, and its life span is only 20-45 hours. Summary of the invention

[0007] The purpose of the present invention is to provide a method for synthesizing durenyl through alkylation of trimethylolbenzene with methanol. The modified IMF structure molecular sieve used in the method has a more suitable B / L value and shows advantages in improving the utilization rate of acid centers, thereby improving the trimethylolbenzene conversion rate, durenylbenzene selectivity and tetramethylbenzene selectivity, and still has high activity stability after a long reaction time, and can be used repeatedly.

[0008] In order to achieve the above-mentioned object, the present disclosure provides a method for synthesizing durene by alkylation of trimethylolbenzene and methanol, the method comprising: contacting trimethylolbenzene with methanol under alkylation reaction conditions and in the presence of a catalyst; wherein the catalyst comprises a modified IMF structure molecular sieve, and the ratio of the amount of B acid to the amount of L acid of the modified IMF structure molecular sieve measured at 200°C by a pyridine adsorption infrared method is 1.5-4.5, and the ratio of the amount of B acid to the amount of L acid measured at 350°C by a pyridine adsorption infrared method is 4-5.

[0009] Optionally, the alkylation reaction conditions include: in a fixed bed reactor, the unsymmetrical trimethylolbenzene and methanol are contacted with the catalyst under gas phase reaction conditions, the gas phase reaction temperature is 300-400°C, preferably 350-380°C; the time is 45-150h, preferably 60-120h; the pressure is 0.5-1.2MPa, preferably 0.6-1.0MPa; the mass space velocity of unsymmetrical trimethylolbenzene is 1.5-1.6h -1 , preferably 1.52~1.58h -1 ; Wherein, the feed molar ratio of the trimethylolbenzene to methanol is (0.5-3):1, preferably (1-2):1.

[0010] Optionally, the ratio of the amount of B acid to the amount of L acid of the modified IMF structure molecular sieve measured by pyridine adsorption infrared method at 200°C is 2-4, and the ratio of the amount of B acid to the amount of L acid measured by pyridine adsorption infrared method at 350°C is 4.5-5; preferably, the total acid amount of the modified IMF structure molecular sieve measured by NH3-TPD method is 900-1600 μmol / g, preferably 1200-1500 μmol / g.

[0011] Optionally, the total specific surface area of ​​the modified IMF structure molecular sieve is 320 to 380 m 2 ·g -1 , preferably 350~370m 2 ·g -1 ; Total pore volume is 0.25~0.4cm 3 ·g -1 , preferably 0.3 to 0.4 cm 3 ·g -1 ; Mesopore volume is 0.1~0.3cm 3 ·g -1 , preferably 0.18 to 0.25 cm 3 ·g -1 .

[0012] Optionally, the molar ratio of silicon element calculated as SiO2 and aluminum element calculated as Al2O3 in the modified IMF structure molecular sieve is 30-320, preferably 30-70; the relative crystallinity is 65-80%, preferably 65-75%; the modified IMF structure molecular sieve is IM-5 molecular sieve, preferably H-IM-5 molecular sieve.

[0013] Optionally, the method further comprises preparing the modified IMF structure molecular sieve by the following steps:

[0014] (1) mixing and stirring a sodium-type IMF structure molecular sieve with a hexafluorosilicic acid solution and / or an ammonium hexafluorosilicate solution to obtain a suspension; or,

[0015] The ammonium type IMF structure molecular sieve is subjected to a first calcination deamination, and the obtained deaminated molecular sieve is mixed with the hexafluorosilicic acid solution and stirred to obtain the suspension;

[0016] (2) performing solid-liquid separation on the suspension, drying the obtained material and performing a second calcination to obtain the modified IMF structure molecular sieve;

[0017] The concentration of the hexafluorosilicic acid solution is 0.005-0.05 mol / L, and the concentration of the ammonium hexafluorosilicate solution is 0.01-0.03 mol / L.

[0018] Optionally, in step (1), the concentration of the hexafluorosilicic acid solution is 0.005-0.02 mol / L; the concentration of the ammonium hexafluorosilicate solution is 0.02-0.03 mol / L.

[0019] Optionally, in step (1), the weight ratio of the sodium-type IMF structure molecular sieve to the hexafluorosilicic acid solution and / or the ammonium hexafluorosilicate solution is 1:(5-20), preferably 1:(7.5-15); the weight ratio of the deaminated molecular sieve to the hexafluorosilicic acid solution is 1:(5-20), preferably 1:(7.5-15).

[0020] Optionally, in step (1), the stirring is heated stirring, and the temperature of the heated stirring is 60-120°C, preferably 70-90°C; the time is 0.5-12h, preferably 4-8h; the rotation speed is 200-550r / min, preferably 300-550r / min; the temperature of the first calcination is 300-600°C, preferably 400-550°C; the time is 2-4h, preferably 2.5-4h; in step (2), the temperature of the drying is 80-150°C, preferably 85-120°C; the time is 8-12h, preferably 8-10h; the temperature of the second calcination is 400-600°C, preferably 450-550°C; the time is 3-5h, preferably 3.5-4.5h.

[0021] Optionally, in step (2), the solid-liquid separation includes one or more of centrifugal separation, filtration separation and rotary evaporation separation, preferably centrifugal separation; the rotation speed of the centrifugal separation is 3000-5000 r / min, and the time is 10-30 min; preferably, the centrifugal separation also includes: dispersing the material obtained by centrifugation in deionized water and centrifuging it multiple times, the number of centrifugations is 3-5 times; the weight ratio of the deionized water to the material obtained by centrifugation is (1.2-2):1, preferably (1.2-1.5):1.

[0022] Through the above technical scheme, the present disclosure provides a method for synthesizing durenyl through the alkylation of trimethylolbenzene and methanol. The method uses a modified IMF structure molecular sieve as a catalyst. Compared with the ZSM-5 molecular sieve, the modified IMF structure molecular sieve has a more suitable B / L value and shows advantages in improving the utilization rate of acid centers. When the molecular sieve is used for the alkylation reaction of trimethylolbenzene and methanol, it shows optimized catalytic performance and can improve the trimethylolbenzene conversion rate, durenyl selectivity and tetramethylolbenzene selectivity. In addition, the catalyst disclosed in the present disclosure has excellent hydrothermal stability, still has high activity stability after a long period of reaction, and can be used repeatedly.

[0023] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0025] Figure 1 is the XRD pattern of catalyst C1 prepared in Preparation Example 1;

[0026] Figure 2 NH3-TPD spectra of catalyst C1 prepared in Preparation Example 1 and comparative catalyst D1 prepared in Preparation Comparative Example 1;

[0027] Figure 3 It is the Py-IR spectra (350° C.) of the catalyst C1 prepared in Preparation Example 1 and the comparative catalyst D1 prepared in Preparation Comparative Example 1. DETAILED DESCRIPTION

[0028] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0029] The present invention discloses a method for synthesizing durene by alkylation of trimethylolbenzene and methanol. The method comprises: contacting trimethylolbenzene with methanol under alkylation reaction conditions and in the presence of a catalyst; wherein the catalyst comprises a modified IMF structure molecular sieve, and the ratio of the amount of B acid to the amount of L acid of the modified IMF structure molecular sieve measured at 200° C. by a pyridine adsorption infrared method is 1.5-4.5, and the ratio of the amount of B acid to the amount of L acid measured at 350° C. by a pyridine adsorption infrared method is 4-5.

[0030] The method provided by the present invention adopts a modified IMF structure molecular sieve as a catalyst. Compared with the ZSM-5 molecular sieve, the modified IMF structure molecular sieve has a higher total acid content and a suitable B / L value, and shows advantages in improving the utilization rate of the acid center. When the molecular sieve is used for the alkylation reaction of trimethylolbenzene with methanol, it shows optimized catalytic performance and can improve the trimethylolbenzene conversion rate, durenyl selectivity and tetramethylolene selectivity; and the catalyst disclosed in the present invention has excellent hydrothermal stability, still has high activity stability after a long period of reaction, and can be used repeatedly.

[0031] In one embodiment of the present disclosure, the alkylation reaction conditions include: in a fixed bed reactor, the unsymmetrical trimethylolbenzene and methanol are contacted with the catalyst under gas phase reaction conditions, the gas phase reaction temperature is 300-400°C, preferably 350-380°C; the time is 45-150h, preferably 60-120h; the pressure is 0.5-1.2MPa, preferably 0.6-1.0MPa; the mass space velocity of unsymmetrical trimethylolbenzene is 1.5-1.6h -1 , preferably 1.52~1.58h -1 ; Wherein, the feed molar ratio of the trimethylolbenzene to methanol is (0.5-3):1, preferably (1-2):1. In the above embodiment, by selecting the preferred alkylation reaction conditions and feed ratio, it is beneficial for trimethylolbenzene and methanol to fully react, and further improve the trimethylolbenzene conversion rate and product selectivity.

[0032] In one embodiment of the present disclosure, the ratio of the amount of B acid to the amount of L acid measured by the pyridine adsorption infrared method at 200°C of the modified IMF structure molecular sieve is 2 to 4, and the ratio of the amount of B acid to the amount of L acid measured by the pyridine adsorption infrared method at 350°C is 4.5 to 5; in a preferred embodiment, the total acid amount measured by the NH3-TPD method of the modified IMF structure molecular sieve is 900 to 1600 μmol / g, preferably 1200 to 1500 μmol / g. In the above embodiment, the IMF type molecular sieve has a higher total acid amount and a more suitable B / L value, which is conducive to improving the conversion rate of partial trimethylbenzene and the product selectivity.

[0033] In one embodiment of the present disclosure, the total specific surface area of ​​the modified IMF structure molecular sieve is 320 to 380 m 2 ·g -1 , preferably 350~370m 2 ·g -1 ; Total pore volume is 0.25~0.4cm 3 ·g -1 , preferably 0.3 to 0.4 cm 3 ·g -1 ; Mesopore volume is 0.1~0.3cm 3 ·g -1 , preferably 0.18 to 0.25 cm 3 ·g -1 In the above embodiment, the modified IMF structure molecular sieve has a larger pore structure. Specifically, the molecular sieve is composed of two two-dimensional pore systems connected by a three-dimensional pore (along the

[010] crystal plane), and a larger cavity is generated at the intersection of the pores, which is beneficial to improve the distribution of raw materials and products, increase the alkylation reaction rate of trimethylolbenzene and methanol, and increase the product C 10The diffusion rate of aromatics can be increased, thereby further improving the conversion rate of trimethylolbenzene, the selectivity of tetramethylolene and the selectivity of tetramethylolene.

[0034] In one embodiment of the present disclosure, the molar ratio of silicon element calculated as SiO2 and aluminum element calculated as Al2O3 in the modified IMF structure molecular sieve is 30-320, preferably 30-70; the relative crystallinity is 65-80%, preferably 65-75%; the modified IMF structure molecular sieve is IM-5 molecular sieve, preferably H-IM-5 molecular sieve. In the above embodiment, the modified IMF structure molecular sieve has a suitable silicon-aluminum ratio and relative crystallinity.

[0035] In one embodiment of the present disclosure, the method further comprises preparing the modified IMF structure molecular sieve by the following steps:

[0036] (1) mixing and stirring a sodium-type IMF structure molecular sieve with a hexafluorosilicic acid solution and / or an ammonium hexafluorosilicate solution to obtain a suspension; or,

[0037] The ammonium type IMF structure molecular sieve is subjected to a first calcination deamination, and the obtained deaminated molecular sieve is mixed with the hexafluorosilicic acid solution and stirred to obtain the suspension;

[0038] (2) performing solid-liquid separation on the suspension, drying the obtained material and performing a second calcination to obtain the modified IMF structure molecular sieve;

[0039] The concentration of the hexafluorosilicic acid solution is 0.005-0.05 mol / L, and the concentration of the ammonium hexafluorosilicate solution is 0.01-0.03 mol / L.

[0040] In the above embodiment, by mixing hexafluorosilicic acid solution or ammonium hexafluorosilicate solution with the IMF structure molecular sieve, the skeleton aluminum distribution of the IMF structure molecular sieve can be regulated, thereby obtaining a modified IMF structure molecular sieve with a higher total acid content and a suitable B / L value. When the molecular sieve is used for the alkylation reaction of trimethylolbenzene with methanol, a higher trimethylolbenzene conversion rate, durene selectivity and tetramethylol selectivity can be obtained.

[0041] In the present disclosure, the preparation method of the sodium-type IMF structure molecular sieve and the ammonium-type IMF structure molecular sieve is not limited, and can be obtained by commercial purchase or prepared by conventional technical methods in the art. In one embodiment, the preparation method of the sodium-type IMF structure molecular sieve includes: S1, mixing a silicon source, an aluminum source, an alkali source, a structure directing agent, water and an optional mineralizer to obtain a first mixture; performing a first stage hydrothermal crystallization and a second stage hydrothermal crystallization on the first mixture to obtain a gel molecular sieve; S2, flocculating and mixing the gel molecular sieve with a first ammonium salt solution, and performing a first drying and a first calcination on the obtained second mixture to obtain a sodium-type IMF structure molecular sieve; The preparation method of the ammonium-type IMF structure molecular sieve includes: contacting the sodium-type IMF structure molecular sieve obtained in S2 with a second ammonium salt solution for ion exchange, and then performing a second drying and a second calcination.

[0042] In one embodiment of the present disclosure, in step (1), the concentration of the hexafluorosilicic acid solution is 0.005-0.02 mol / L; the concentration of the ammonium hexafluorosilicate solution is 0.02-0.03 mol / L. In the above embodiment, the hexafluorosilicic acid solution or the ammonium hexafluorosilicate solution of the preferred concentration is selected to obtain a modified IMF structure molecular sieve with a higher acid content and acid strength.

[0043] In one embodiment of the present disclosure, in step (1), the weight ratio of the sodium type IMF structure molecular sieve to the hexafluorosilicic acid solution and / or the ammonium hexafluorosilicate solution is 1: (5-20), preferably 1: (7.5-15); the weight ratio of the deaminated molecular sieve to the hexafluorosilicic acid solution is 1: (5-20), preferably 1: (7.5-15).

[0044] In one embodiment of the present disclosure, in step (1), the stirring is heated stirring, and the temperature of the heated stirring is 60-120°C, preferably 70-90°C; the time is 0.5-12h, preferably 4-8h; the rotation speed is 200-550r / min, preferably 300-550r / min; the temperature of the first calcination is 300-600°C, preferably 400-550°C; the time is 2-4h, preferably 2.5-4h; in step (2), the temperature of the drying is 80-150°C, preferably 85-120°C; the time is 8-12h, preferably 8-10h; the temperature of the second calcination is 400-600°C, preferably 450-550°C; the time is 3-5h, preferably 3.5-4.5h.

[0045] In one embodiment of the present disclosure, in step (2), the solid-liquid separation includes one or more of centrifugal separation, filtration separation and rotary evaporation separation, preferably centrifugal separation; the speed of the centrifugal separation is 3000-5000 r / min, and the time is 10-30 min; in a preferred embodiment, the centrifugal separation also includes: dispersing the centrifuged material in deionized water and centrifuging it multiple times, the number of centrifugations is 3-5 times; the weight ratio of the deionized water to the centrifuged material is (1.2-2):1, preferably (1.2-1.5):1. In a specific embodiment, the suspension is placed in a low-speed centrifuge, and repeated centrifugation is performed for solid-liquid separation, and F is removed by washing. - and / or Na + A certain amount of deionized water needs to be repeatedly added and stirred at each centrifugal interval to completely mix it with the suspension to obtain a gel-like material containing the modified IMF structure molecular sieve; the gel-like material is dried and calcined for the second time to obtain the modified IMF structure molecular sieve.

[0046] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0047] In the embodiments and comparative examples of the present disclosure, a Quanta 200F scanning electron microscope (SEM) produced by FEI Company was used for microscopic morphology analysis, and the operating voltage of the SEM was 20 kV; a Japan Hitachi S-4800 type instrument was used to test the average particle size of the catalyst.

[0048] The crystallinity of the molecular sieve is determined by the RIPP 146-90 standard method. The RIPP standard method mentioned here can be found in "Petrochemical Analysis Methods", edited by Yang Cuiding et al., 1990 edition.

[0049] The chemical composition of the molecular sieve was determined by using a 3013 X-ray fluorescence spectrometer produced by Rigaku Corporation of Japan, and the silicon-aluminum ratio of the molecular sieve was calculated. The target was tungsten, the excitation voltage was 40 kV, and the excitation current was 50 mA.

[0050] The specific surface area and pore volume were measured using the AS-3 and AS-6 static nitrogen adsorption instruments produced by Quantachrome Instruments. The specific method was as follows: the sample was placed in a sample treatment system and vacuumed to 1.33×10 -2 Pa, keep warm and maintain pressure for 4 hours, and purify the sample; at a liquid nitrogen temperature of -196°C, test the adsorption and desorption of nitrogen by the purified sample under different pressure ratios P / P0, obtain the N2 adsorption-desorption isotherm curve, calculate the specific surface area by the BET method, calculate the mesopore volume of the sample by the t-plot method, and take the adsorption amount below the pressure ratio P / P0=0.98 as the total pore volume of the sample.

[0051] The total acid content was measured using the NH3-TPD method and determined using the AutochemⅡ2920 programmed temperature desorber from Mack, USA. The specific method was as follows: 0.2 g of the sample to be tested was weighed and loaded into a sample tube, placed in a thermal conductivity cell heating furnace, with He gas as the carrier gas (50 mL / min), heated to 600°C at a rate of 20°C / min, purged for 60 minutes to remove impurities adsorbed on the catalyst surface, then cooled to 100°C, kept constant for 30 minutes, switched to NH3-He mixed gas (10.02% NH3+89.98% He) for adsorption for 30 minutes, and then continued to purge with He gas for 90 minutes until the baseline was stable to desorb physically adsorbed ammonia; the temperature was raised to 600°C at a heating rate of 10°C / min for desorption, maintained for 30 minutes, and the desorption was completed; a TCD detector was used to detect changes in gas components, and the instrument automatically integrated to obtain the total acid content.

[0052] The acid content of B acid and L acid was measured by 2,6-di-tert-butylpyridine adsorption infrared acid method using a Vertex 70 instrument produced by Bruker Instruments. The specific method is as follows: the catalyst is pressed into a 10 mg / cm 2 The thin slice was placed in an infrared cell with a CaF2 window, first evacuated at 400°C, then lowered to 150°C to adsorb 2,6-di-tert-butylpyridine for 15 minutes, then evacuated for 1 hour, lowered to room temperature to collect spectra, and calculated the acid amounts of B acid and L acid. See Applied Catalysis A: General, 294, 2005: 92.

[0053] The gas chromatography peak area normalization method was used to calculate the conversion rate of trimethylol, durene selectivity and tetramethylol selectivity. The specific test method was as follows: the carrier gas was nitrogen, the detector was FID, the column temperature was 80°C, the injector temperature was 260°C, and the detector temperature was 250°C. The initial temperature of the program temperature rise was 0°C, the holding time was 0min, and the heating rate was 3°C / min; the final temperature was 50°C, and the holding time was 20min. The injection volume was 0.2μL.

[0054] The activity stability of the catalyst is measured by a high-pressure micro-reaction test device. The specific method is to take 2g of the molded catalyst sample (20-40 mesh) and load it into the constant temperature section of the tubular reactor. Quartz sand and quartz wool are respectively filled on both sides of the catalyst. The two sections of the reaction tube are sealed with graphite gaskets. A high-precision micro pump is used to feed the mixed raw material of trimethylbenzene and methanol at a certain volume flow rate. N2 is used as the carrier gas, and the carrier gas flow rate is 360ml / min. The reaction is carried out at a certain pressure and temperature. The product is directly sampled continuously by a six-way valve, and qualitative and quantitative analysis is performed on a Varian GC 450 gas chromatograph. The chromatographic column is Agilent DBWAX (30*0.25*0.25). Refer to Modern Chemical Industry, 2023, 43(01), 185-191, 197, DOI: 10.16606 / j.cnki.issn0253-4320.2023.01.033.

[0055] Preparation Example 1

[0056] This preparation example 1 is used to illustrate the preparation of modified IMF structure molecular sieve:

[0057] (1) 0.103 g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 49.922 g of deionized water, and after mixing, 50 mL of 0.005 mol / L hexafluorosilicic acid solution was prepared. 5 g of NH3-IM-5 molecular sieve (ammonium type IMF structure molecular sieve) was first calcined at 550°C for 4 h to remove ammonia, and the obtained deaminated molecular sieve was fully mixed with 37.5 g of 0.005 mol / L hexafluorosilicic acid solution (the weight ratio of the deaminated molecular sieve to the hexafluorosilicic acid solution was 1:7.5), and heated and stirred continuously at 80°C at 420 r / min for 1 h to obtain a suspension;

[0058] (2) The suspension was placed in a low-speed centrifuge at 5000 r / min for solid-liquid separation for 15 min, and centrifuged repeatedly for 3 times. Deionized water was added each time, and the weight ratio of deionized water to the gel obtained by centrifugation was 1.2:1. The material obtained after multiple centrifugation was placed in a drying oven at 120°C for 10 h, and then calcined for a second time in a muffle furnace at 550°C for 4 h to obtain a modified H-IM-5 molecular sieve, i.e., a modified IMF structure molecular sieve; the molecular sieve was pressed into a sheet at a pressure of 20 MPa, and particles of 20 to 40 mesh (i.e., an average particle size of 0.63 to 0.85 mm) were selected as catalyst C1, recorded as I-0.005. Its physicochemical properties are shown in Tables 1 and 2.

[0059] Preparation Example 2

[0060] The same as Preparation Example 1, the only difference is that in step (1), 0.412g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 99.688g of deionized water, mixed evenly, and then prepared into 100mL of 0.01mol / L hexafluorosilicic acid solution. Finally, catalyst C2 was obtained, which was recorded as I-0.01. Its physicochemical properties are shown in Tables 1 and 2.

[0061] Preparation Example 3

[0062] The same as Preparation Example 1, the only difference is that: in step (1), (1) 0.412g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 49.688g of deionized water, mixed evenly, and then prepared into 50mL of 0.02mol / L hexafluorosilicic acid solution. Finally, catalyst C3 was obtained, which was recorded as I-0.02-1. Its physicochemical properties are shown in Tables 1 and 2.

[0063] Preparation Example 4

[0064] The same as Preparation Example 1, the only difference is that: in step (1), 0.617g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 49.532g of deionized water, and after mixing, 50mL of 0.03mol / L hexafluorosilicic acid solution was prepared. 5g of Na-IM-5 molecular sieve (sodium type IMF structure molecular sieve) was fully mixed with 37.5g of 0.03mol / L hexafluorosilicic acid solution (the weight ratio of sodium type IMF structure molecular sieve to hexafluorosilicic acid solution was 1:7.5), and finally catalyst C4 was obtained, which was recorded as I-0.03. Its physicochemical properties are shown in Tables 1 and 2.

[0065] Preparation Example 5

[0066] The same as Preparation Example 1, the only difference is that: in step (1), 0.823g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 49.376g of deionized water, and after mixing, 50mL of 0.04mol / L hexafluorosilicic acid solution was prepared. 5g of Na-IM-5 molecular sieve (sodium type IMF structure molecular sieve) was fully mixed with 37.5g of 0.04mol / L hexafluorosilicic acid solution to finally obtain catalyst C5, which was recorded as I-0.04. Its physicochemical properties are shown in Tables 1 and 2.

[0067] Preparation Example 6

[0068] The same as Preparation Example 1, the only difference is that: in step (1), 0.909g of ammonium hexafluorosilicate solution (98.00 mass%) is dissolved in 100mL of deionized water, then transferred to a 250mL volumetric flask, and water is continued to be added to 250mL. After uniform mixing, 250mL of 0.02mol / L ammonium hexafluorosilicate solution is prepared. 10g of Na-IM-5 molecular sieve (sodium type IMF structure molecular sieve) is fully mixed with 150g of 0.02mol / L ammonium hexafluorosilicate solution (the weight ratio of sodium type IMF structure molecular sieve to ammonium hexafluorosilicate solution is 1:15), and finally catalyst C6 is obtained, which is recorded as I-0.02-2. Its physicochemical properties are shown in Tables 1 to 2.

[0069] Preparation Example 7

[0070] The same as Preparation Example 1, the only difference is that: in step (1), 1.136g of ammonium hexafluorosilicate solution (98.00 mass%) is dissolved in 100mL of deionized water, then transferred to a 250mL volumetric flask, and water is continued to be added to 250mL. After uniform mixing, 250mL of 0.025mol / L ammonium hexafluorosilicate solution is prepared. 5g of Na-IM-5 molecular sieve (sodium type IMF structure molecular sieve) is fully mixed with 37.5g of 0.025mol / L ammonium hexafluorosilicate solution to finally obtain catalyst C7, which is recorded as I-0.025. Its physicochemical properties are shown in Tables 1 to 2.

[0071] Preparation Comparative Example 1

[0072] This preparation comparative example 1 is used to illustrate the preparation of IMF structure molecular sieve:

[0073] (1) 60.00 g of solid silica gel (silicon source, 93.2% by mass in terms of SiO2), 29.62 g of sodium aluminate (aluminum source, 8.17% by mass in terms of Al2O3, 15.6% by mass in terms of NaOH), 9.16 g of sodium hydroxide (alkali source, 96% by mass in terms of alkali metal oxide M2O), 76.05 g of a structure directing agent (58.9% by mass, with a structural formula of Expressed as SDR, molecular weight is 400) and 177.06g water in the molar ratio of SiO2 / Al2O3=40, Na2O / SiO2=0.185, SDR / SiO2=0.12, H2O / SiO2=14, added to the Teflon liner in the order of liquid first and solid later, mixed evenly to form a gel or solid-liquid mixture. Then placed in a high-pressure reactor with a volume of 600mL, two stages of hydrothermal crystallization were carried out in a homogeneous reactor, the temperature of the first stage of hydrothermal crystallization was 160°C, the time was 48h; the temperature of the second stage of hydrothermal crystallization was 175°C, the time was 96h. The gel Na-IM-5 molecular sieve was obtained;

[0074] (2) The gel Na-IM-5 molecular sieve was flocculated and mixed with a 20% mass fraction of ammonium chloride solution, filtered and dried in a 110°C drying oven for 10 hours, ground and calcined in a 600°C muffle furnace for 3 hours to remove the structure directing agent. The obtained powdered Na-IM-5 molecular sieve was ion exchanged with a 20% mass fraction of ammonium chloride solution, with a liquid-solid mass ratio of 20, 3 exchanges, and an exchange temperature of 80°C. Centrifuged 3 times until the pH value was neutral, the speed was 4000r / min, and the time was 20min. The obtained NH3-IM-5 molecular sieve gel was placed in a 120°C drying oven for 8 hours, ground and calcined in a 550°C muffle furnace for 3 hours. The H-IM-5 molecular sieve, i.e., the IMF structure molecular sieve, was obtained; the molecular sieve was pressed into sheets at a pressure of 20 MPa, and particles of 20 to 40 mesh (i.e., an average particle size of 0.63 to 0.85 mm) were screened as comparative catalyst D1, denoted as I. Its physicochemical properties are shown in Tables 1 to 2.

[0075] Preparation Comparative Example 2

[0076] The same as Preparation Example 1, the only difference is that: in step (1), 1.647g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 48.752g of deionized water, mixed evenly, and then 50mL of 0.08mol / L hexafluorosilicic acid solution was prepared, 5g of Na-IM-5 molecular sieve (sodium type IMF structure molecular sieve) and 37.5g of 0.08mol / L hexafluorosilicic acid solution were fully mixed (the weight ratio of sodium type IMF structure molecular sieve to hexafluorosilicic acid solution was 1:7.5), and finally a comparative catalyst D2 was obtained, which was recorded as I-0.08. Its physicochemical properties are shown in Tables 1 and 2.

[0077] Preparation Comparative Example 3

[0078] The same as Preparation Example 1, the only difference is that in step (1), 4.940g of hexafluorosilicic acid solution (35.00 mass%) was added dropwise to 96.256g of deionized water, mixed evenly, and then prepared into 100mL of 0.12mol / L hexafluorosilicic acid solution, and finally obtained comparative catalyst D3, which was recorded as I-0.12. Its physicochemical properties are shown in Tables 1-2.

[0079] Preparation Comparative Example 4

[0080] The ZSM-5 molecular sieve powder (Changling Branch of Sinopec Catalyst Company) with a silicon-aluminum ratio of 45 was ion exchanged with a 20% mass fraction of ammonium chloride solution, the liquid-to-solid mass ratio was 20, the number of exchanges was 3, and the exchange temperature was 80°C. After 3 centrifugations until the pH value was neutral, the speed was 4000r / min, and the time was 20min. The NH3-ZSM-5 molecular sieve gel was obtained, placed in a 120°C drying oven for 8h, and then ground and placed in a 550°C muffle furnace for calcination for 3h to obtain H-ZSM-5 molecular sieve. The molecular sieve was pressed into sheets under a pressure of 20MPa, and particles of 20-40 mesh (i.e., an average particle size of 0.63-0.85mm) were screened as comparative catalyst D4, denoted as Z. Its physicochemical properties are shown in Tables 1-2.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085]

[0086] The following examples and comparative examples are used to illustrate the method of catalyzing the alkylation reaction of trimethylolbenzene with methanol using different catalysts.

[0087] Example 1

[0088] 2 g of the catalyst C1 prepared in Preparation Example 1 was loaded into a fixed bed reactor, and partial trimethylbenzene and methanol were added thereto as reaction raw materials. The reaction conditions were: reaction temperature of 360°C, reaction pressure of 0.8 MPa, reaction time of 30 h, nitrogen flow rate of 360 mL / min, partial trimethylbenzene to methanol feed molar ratio of 2:1, and mass space velocity of partial trimethylbenzene of 1.52 h -1 , all components were analyzed by GC online. The evaluation results are shown in Table 3. The conversion rate of unsymmetrical trimethylolbenzene, the selectivity of tetramethylolbenzene, the selectivity of tetramethylolbenzene and the yield of tetramethylolbenzene were calculated according to the following formulas (1) to (4):

[0089]

[0090]

[0091]

[0092] Durene yield = trimethylol conversion rate * durene selectivity (4).

[0093] Embodiments 2 to 6

[0094] The alkylation reaction of trimethylol and methanol was carried out according to the method and reaction conditions of Example 1. The catalysts C2 to C4 and C6 prepared in Preparation Examples 2 to 4 and 6 were used to catalyze the alkylation reaction. The reaction results are shown in Table 3.

[0095] Example 7

[0096] 2 g of the catalyst C3 prepared in Preparation Example 3 was loaded into a fixed bed reactor, and partial trimethylbenzene and methanol were added thereto as reaction raw materials. The reaction conditions were: reaction temperature of 360° C., reaction pressure of 0.8 MPa, reaction time of 20 h, nitrogen flow rate of 360 mL / min, partial trimethylbenzene to methanol feed molar ratio of 1:2, and mass space velocity of partial trimethylbenzene of 1.56 h / min. -1 , all components were analyzed by GC online. The evaluation results are shown in Table 4.

[0097] Embodiments 8 to 10

[0098] The alkylation reaction of trimethylol and methanol was carried out according to the method and reaction conditions of Example 7. The catalysts C4-C5 and C7 prepared in Preparation Examples 4-5 and 7 were used to catalyze the alkylation reaction. The reaction results are shown in Table 4.

[0099] Embodiment 11

[0100] The alkylation reaction was carried out according to the method of Example 1, except that the mass space velocity of trimethylol was 1h -1 , the reaction time was 35h, and the feed molar ratio of trimethylol to methanol was 1:2. The reaction results are shown in Table 4.

[0101] Comparative Examples 1-2

[0102] The alkylation reaction of trimethylol and methanol was carried out according to the method and reaction conditions of Example 1. The comparative catalysts D3-D4 prepared in Comparative Examples 3-4 were used to catalyze the alkylation reaction. The reaction results are shown in Table 3.

[0103] Comparative Examples 3 to 5

[0104] The alkylation reaction of trimethylol and methanol was carried out according to the method and reaction conditions of Example 7. The comparative catalysts D1-D2 and D4 prepared in Preparation Comparative Examples 1, 2 and 4 were used to catalyze the alkylation reaction. The reaction results are shown in Table 4.

[0105] Table 3

[0106]

[0107] Table 4

[0108]

[0109] From the results of Tables 1 to 4 above, it can be seen that the modified IMF structure molecular sieve provided by the present disclosure has a higher acid content and acid strength, and a more suitable B / L value, and shows advantages in improving the utilization rate of the acid center, so that when it is used as a catalyst for the alkylation reaction of partial trimethylbenzene and methanol, it can improve the conversion rate of partial trimethylbenzene, the selectivity of tetramethylbenzene and tetramethylbenzene, and has higher activity stability. However, when comparative examples 1 to 5 do not adopt the technical solution of the present disclosure and are used for the alkylation reaction of partial trimethylbenzene and methanol, the conversion rate of partial trimethylbenzene and the selectivity of tetramethylbenzene are low, and the activity stability is poor.

[0110] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0112] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for synthesizing durene by alkylation of trimethylolbenzene and methanol, characterized in that: The method comprises: contacting unsymmetrical trimethylbenzene with methanol under alkylation reaction conditions and in the presence of a catalyst; wherein the catalyst comprises a modified IMF structure molecular sieve, and the ratio of the B acid amount to the L acid amount of the modified IMF structure molecular sieve measured at 200°C by a pyridine adsorption infrared method is 1.5-4.5, and the ratio of the B acid amount to the L acid amount measured at 350°C by a pyridine adsorption infrared method is 4-5.

2. The method according to claim 1, characterized in that The alkylation reaction conditions include: in a fixed bed reactor, making the unsymmetrical trimethylbenzene and methanol contact with the catalyst under gas phase reaction conditions, the gas phase reaction temperature is 300-400°C, preferably 350-380°C; the time is 45-150h, preferably 60-120h; the pressure is 0.5-1.2MPa, preferably 0.6-1.0MPa; the mass space velocity of unsymmetrical trimethylbenzene is 1.5-1.6h -1 , preferably 1.52~1.58h -1 ; The feed molar ratio of the trimethylolbenzene to methanol is (0.5-3):1, preferably (1-2):

1.

3. The method according to claim 1, characterized in that The modified IMF structure molecular sieve has a ratio of 2 to 4 of B acid to L acid measured by pyridine adsorption infrared method at 200°C, and a ratio of 4.5 to 5 of B acid to L acid measured by pyridine adsorption infrared method at 350°C; Preferably, the total acid content of the modified IMF structure molecular sieve measured by NH3-TPD method is 900-1600 μmol / g, preferably 1200-1500 μmol / g.

4. The method according to claim 1, characterized in that The total specific surface area of ​​the modified IMF structure molecular sieve is 320 to 380 m 2 ·g -1 , preferably 350~370m 2 ·g -1 ; Total pore volume is 0.25~0.4cm 3 ·g -1 , preferably 0.3 to 0.4 cm 3 ·g -1 ; Mesopore volume is 0.1~0.3cm 3 ·g -1 , preferably 0.18 to 0.25 cm 3 ·g -1 .

5. The method according to claim 1, characterized in that The molar ratio of silicon element calculated as SiO2 to aluminum element calculated as Al2O3 in the modified IMF structure molecular sieve is 30 to 320, preferably 30 to 70; the relative crystallinity is 65 to 80%, preferably 65 to 75%; The modified IMF structure molecular sieve is IM-5 molecular sieve, preferably H-IM-5 molecular sieve.

6. The method according to claim 1, characterized in that The method further comprises preparing the modified IMF structure molecular sieve by the following steps: (1) mixing and stirring a sodium-type IMF structure molecular sieve with a hexafluorosilicic acid solution and / or an ammonium hexafluorosilicate solution to obtain a suspension; or, The ammonium type IMF structure molecular sieve is subjected to a first calcination deamination, and the obtained deaminated molecular sieve is mixed with the hexafluorosilicic acid solution and stirred to obtain the suspension; (2) performing solid-liquid separation on the suspension, drying the obtained material and performing a second calcination to obtain the modified IMF structure molecular sieve; The concentration of the hexafluorosilicic acid solution is 0.005-0.05 mol / L, and the concentration of the ammonium hexafluorosilicate solution is 0.01-0.03 mol / L.

7. The method according to claim 6, characterized in that In step (1), the concentration of the hexafluorosilicic acid solution is 0.005-0.02 mol / L; the concentration of the ammonium hexafluorosilicate solution is 0.02-0.03 mol / L.

8. The method according to claim 6, characterized in that In step (1), the weight ratio of the sodium type IMF structure molecular sieve to the hexafluorosilicic acid solution and / or the ammonium hexafluorosilicate solution is 1: (5-20), preferably 1: (7.5-15); the weight ratio of the deaminated molecular sieve to the hexafluorosilicic acid solution is 1: (5-20), preferably 1: (7.5-15).

9. The method according to claim 6, characterized in that In step (1), the stirring is heating stirring, the temperature of the heating stirring is 60-120° C., preferably 70-90° C.; the time is 0.5-12 h, preferably 4-8 h; the speed is 200-550 r / min, preferably 300-550 r / min; the temperature of the first calcination is 300-600° C., preferably 400-550° C.; the time is 2-4 h, preferably 2.5-4 h; In step (2), the drying temperature is 80-150°C, preferably 85-120°C; the time is 8-12 hours, preferably 8-10 hours; the second calcination temperature is 400-600°C, preferably 450-550°C; the time is 3-5 hours, preferably 3.5-4.5 hours.

10. The method according to claim 6, characterized in that In step (2), the solid-liquid separation includes one or more of centrifugal separation, filtration separation and rotary evaporation separation, preferably centrifugal separation; the speed of the centrifugal separation is 3000-5000 r / min, and the time is 10-30 min; Preferably, the centrifugal separation further comprises: dispersing the material obtained by centrifugation in deionized water and centrifuging multiple times, the number of centrifugation times being 3 to 5 times; the weight ratio of the deionized water to the material obtained by centrifugation is (1.2 to 2):1, preferably (1.2 to 1.5):1.

Images