A method for preparing an aromatic compound

Abstract

The application relates to the field of catalytic material preparation and organic synthesis, and discloses a method for preparing aromatic compounds, in particular to a method for synthesizing aromatic compounds such as benzene and phenol through 2,6-dimethoxyphenol. The 2,6-dimethoxyphenol is subjected to hydrogenation and deoxidization treatment by using a Pt@Fe / SiO2 catalyst for the first time, so that the synthesis of the final product aromatic compound is realized. The method provided by the application has single product, the Pt@Fe / SiO2 catalyst is used, the selectivity of the aromatic compound in the final reaction product is greater than 80%, the reaction temperature is controlled in the range of 473-623 K, and the 2,6-dimethoxyphenol can be quickly completely converted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic material preparation and organic synthesis, and particularly relates to a method for synthesizing an aromatic compound by using 2,6-dimethoxyphenol (syringol) as a raw material. BACKGROUND

[0002] Aromatic compounds such as benzene and phenol are important chemical and pharmaceutical synthesis intermediates, which are usually prepared by reforming aromatic compounds or dehydrogenating cycloalkanes. The use of renewable resources to prepare aromatic compounds is a future development trend and has been a focus of attention. This important process can be achieved by heterogeneous or homogeneous catalysis, and heterogeneous catalysts have been widely used in this field due to their convenient separation and easy regeneration.

[0003] 2,6-dimethoxyphenol, also known as syringol, is a structural monomer formed after lignin cracking and can be obtained by biotransformation. Syringol is widely available in nature and can replace petroleum as a biofuel or chemical raw material. Currently, syringol, guaiacol and phenol are commonly used as lignin model compounds to study their hydrogenation performance. For example, on sulfided CoMo and CoMo catalysts, guaiacol can be catalytically hydrogenated to produce benzene, cyclohexene and cyclohexane, and the hydrocarbon yield can reach 72.2% at 325℃ [1] . Due to steric hindrance, syringol is more difficult to react than guaiacol and phenol [2] , and it is also more prone to carbon deposition due to its two adjacent methoxy groups [3] . Riyang et al. used Ni / SiO2-Al2O3 to catalyze 2,6-dimethoxyphenol, and the conversion rate of the raw material was about 95% at 200℃, and the selectivity of cyclohexane was about 97%. The acid centers provided by Al2O3 in the catalyst are the key to the reaction [4] . Regulating the performance of the catalyst and selecting catalytic hydrogenation to prepare aromatic compounds is an important research content of this type of reaction.

[0004] Currently, there is no report on using Pt@Fe / SiO2 as a catalyst for the selective hydrogenation and deoxygenation of 2,6-dimethoxyphenol to prepare aromatic compounds.

[0005] [1] J. B. Bredenberg, M. Huuska, P. Toropainen, J. Catal. 120 (1989) 401-408.

[0006] [2] A. Sequeiros, L. Serrano, J. Labidi, J. Chem. Technol. Biotechnol. 91 (2016) 1809-1815.

[0007] [3] M. Asmadi, H. Kawamoto, S. Saka, J. Anal. Appl. Pyrolysis 92 (2011) 88-98.

[0008] [4] R. Shu, Y. Xu, L. Ma, Q. Zhang, P. Chen, T. Wang. Catalysis CommuCocations 91 (2017) 1-5. SUMMARY

[0009] In order to make up for the deficiencies of the prior art, the present application provides a method for preparing aromatic compounds, in particular to a method for synthesizing benzene, phenol and other aromatic compounds from 2,6-dimethoxyphenol. The present application first uses Pt@Fe / SiO2 catalyst to selectively hydrogenate and deoxidize 2,6-dimethoxyphenol (syringol), so as to realize the synthesis of the final product aromatic compound. The preparation method provided by the present application has single product, simple catalyst preparation method, good reaction performance and high product selectivity.

[0010] In order to achieve the above object, the present application adopts the following technical scheme, a method for preparing aromatic compounds, in particular:

[0011] The Pt@Fe / SiO2 catalyst is prepared by the equal volume impregnation method: (1) first, the water absorption amount of SiO2 is measured, 1g of dried SiO2 is placed in a beaker, and an appropriate amount of deionized water is transferred into the beaker by a pipette, following the principle of small amount and multiple times, and constantly stirring with a glass rod, when the SiO2 in the beaker is slightly sticky and no water seeps out, it is the water saturation state of SiO2, and the volume of water transferred is recorded; (2) Pt and Fe containing compounds are dissolved in water to prepare Pt solution (such as chloroplatinic acid solution) with a concentration of 0.2mol / L and Fe solution (such as ferric nitrate solution) with a concentration of 2.0mol / L, then the corresponding volume of Pt and Fe solutions is mixed according to the mass ratio of Pt, Fe and SiO2 in the catalyst design, and deionized water is added to make up the liquid volume required for equal volume impregnation, SiO2 is added to the solution and mixed uniformly, and then it is placed for 6-24h, dried at 353K-383K for 12-24h, and calcined at 623K-723K under Ar environment for 1-4h, and sealed for standby.

[0012] Before reaction, a certain amount of Pt@Fe / SiO2 catalyst is added into a high-temperature and high-pressure batch reactor, and reduced at 350-450℃ for 10-30min under 1.0-3.0MPa H2. After cooling, 2,6-dimethoxyphenol (syringol) and an organic solvent (alkane) are added into the batch reactor, and the reactor is sealed, and then 3.0MPa nitrogen is used to replace the air in the reactor for 3 times, and then 0.1MPa-3.0MPa hydrogen is introduced, and the reaction temperature is 473-623K, and the reaction time is 30min-12h, so as to obtain phenol and aromatic compounds such as benzene;

[0013] The amount of the Pt@Fe / SiO2 catalyst is 5-30% of the mass of 2,6-dimethoxyphenol.

[0014] The organic solvent is any one of n-decane, n-dodecane, n-tetradecane or n-hexadecane.

[0015] Further, the Pt@Fe / SiO2 catalyst is prepared by an equal-volume impregnation method, wherein the metal loading amount is 0.005-0.02g of Pt and 0.025-0.10g of Fe per 1g of SiO2.

[0016] Further, the Pt-containing compound includes any one of chloroplatinic acid, platinum chloride, platinum bromide, platinum iodide, ammonium hexachloroplatinate, platinum nitrate, tetraammine platinum nitrate; the Fe-containing compound includes any one of iron nitrate, iron chloride, iron bromide, iron sulfate, ferrous nitrate, ferrous chloride, ferrous bromide, ferrous sulfate; and the SiO2 is nano or micron-sized silicon dioxide with a size of 100nm-10μm.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] The present application uses the Pt@Fe / SiO2 catalyst, so that the selectivity of aromatic compounds in the final reaction product is greater than 80%. The reaction temperature is controlled at 473-623K, and 2,6-dimethoxyphenol can be quickly converted. The Pt@Fe / SiO2 catalyst of the present application has good repeated use performance in the batch reactor. DETAILED DESCRIPTION

[0019] The present application will be described in detail below through specific examples, but the protection scope of the present application is not limited. Unless otherwise specified, the experimental methods used in the present application are conventional methods, and the experimental apparatus, materials and reagents used can be purchased from chemical companies.

[0020] The content of Pt and Fe in the catalyst can be determined by ICP, and the metal loading amount on 1 g of SiO2 is in the range of 0.005-0.02 g of Pt and 0.025-0.10 g of Fe, and better reaction performance can be obtained. Before the reaction, a certain amount of catalyst is added into a high-temperature and high-pressure batch reactor, and 1.0-3.0 MPa of H2 is used to reduce at 350-450°C for 10-30 min. After cooling, 2,6-dimethoxyphenol (syringol) and an organic solvent (alkane) are added into the batch reactor, and 3.0 MPa of nitrogen is used to replace the air in the reactor for 3 times. After evacuation, 0.1 MPa-3.0 MPa of hydrogen is introduced, the reaction temperature is in the range of 473-623 K, the reaction time is 30 min-12 h, and after a period of reaction, the sample is taken to calculate the conversion rate of the raw material and the yield of each product.

[0021]

[0022]

[0023] n0: the amount of substance (mol) of 2,6-dimethoxyphenol in the reaction raw material;

[0024] n1: the amount of substance (mol) of 2,6-dimethoxyphenol in the reaction liquid after the reaction.

[0025] n2: the amount of substance (mol) of the aromatic compound benzene or phenol.

[0026] After the catalyst is calcined, the valence state of the loaded metal is not unique, the loading amount of Pt and Fe in the catalyst is expressed by the mass ratio of Pt, Fe element to SiO2, and the metal loading amount is embodied in the "catalyst composition" in the example list, such as 2Pt@10Fe / SiO2 represents 1 g of SiO2 loaded with 0.02 g of Pt and 0.10 g of Fe element. 2负载 0.02 g of Pt and 0.10 g of Fe element.

[0027] Example 1

[0028] Pt@Fe / SiO2 catalysts were prepared by the incipient wetness impregnation method: (1) First, the water absorption of SiO2 was measured. 1 g of dried SiO2 (100 nm) was placed in a beaker, and an appropriate amount of deionized water was added to the beaker using a pipette, following the principle of small amount and multiple times, and constantly stirring with a glass rod. When the SiO2 in the beaker was slightly sticky and no water seeped out, it was considered that the SiO2 was saturated with water, and the volume of water added was recorded; (2) Pt and Fe compounds were dissolved in water to prepare a 0.1 mol / L chloroplatinic acid solution and a 1.0 mol / L ferric nitrate solution, respectively, and SiO2 with a particle size of 100 nm was used as the carrier. A certain amount of Pt and Fe solutions were mixed with deionized water, 1 g of SiO2 was added to the solution and stirred uniformly, and then it was left to stand for 12 h, dried at 353 K for 12 h, and calcined at 673 K for 2 h under Ar atmosphere, and then sealed for use. The blank sample used deionized water instead of Pt and Fe solutions, and was operated according to the above method.

[0029] Before the reaction, 0.05 g of catalyst was added to a high-temperature and high-pressure batch reactor and reduced at 623 K for 30 min using 3.0 MPa H2. After cooling, 0.5 g of 2,6-dimethoxyphenol (syringol) and 10 ml of n-decane were added to the batch reactor, which was sealed and purged with 3.0 MPa nitrogen three times to replace the air in the reactor. After evacuation, 3.0 MPa of hydrogen was introduced, and the reaction temperature was 623 K, the stirring speed was 700 rpm, and the reaction time was 8 h. The amount of Pt and Fe solutions used in the catalyst preparation process is shown in Table 1.

[0030] The reaction results of Example 1 are shown in Table 2.

[0031] Table 1. Catalyst information summary table of Example 1

[0032]

[0033]

[0034] Table 2. Reaction results summary table of Example 1

[0035]

[0036] Example 2

[0037] The catalyst prepared by the incipient wetness impregnation method was left to stand for a certain time and then dried at 353-383 K for a certain time. The remaining catalyst preparation methods and parameters were performed according to the operation of 1Pt@7Fe / SiO2 in Example 1. The catalyst pre-reduction, reaction loading, and reaction conditions were the same as in Example 1. The catalyst standing and drying information is shown in Table 3.

[0038] The reaction results of Example 2 are shown in Table 4.

[0039] Table 3. Summary of catalyst information for Example 2

[0040]

[0041]

[0042] Table 4. Summary of reaction results for Example 1

[0043]

[0044] Example 3

[0045] The catalyst was prepared by calcination at 623-723 K for 1-4 h, and the rest of the preparation was performed according to the procedure for 1 Pt@7Fe / SiO2in Example 1. The catalyst was pre-reduced, and the reaction feed amount and reaction conditions were the same as in Example 1. The catalyst calcination information is shown in Table 5.

[0046] The reaction results for Example 3 are shown in Table 6.

[0047] Table 5. Summary of catalyst information for Example 3

[0048]

[0049] Table 6. Summary of reaction results for Example 3

[0050]

[0051] Example 4

[0052] The catalyst was prepared by using different Pt and Fe compounds to prepare the solution, and the rest of the preparation was performed according to the procedure for 1 Pt@7Fe / SiO2in Example 1. The catalyst was pre-reduced, and the reaction feed amount and reaction conditions were the same as in Example 1. The Pt and Fe solution information is shown in Table 7.

[0053] The reaction results for Example 4 are shown in Table 8.

[0054] Table 7. Summary of catalyst information for Example 4

[0055]

[0056]

[0057] Table 8. Summary of reaction results for Example 4

[0058]

[0059] Example 5

[0060] The catalyst used 1 Pt@7 Fe / SiO2, and the catalyst was pre-reduced using 1.0-3.0 MPa H2 at 623-723 K for 10-30 min before the reaction. The catalyst preparation method, reactant feeding amount, and reaction conditions were the same as in Example 1. The specific pre-reduction conditions are shown in Table 9.

[0061] The reaction results of Example 5 are shown in Table 10.

[0062] Table 9. Summary table of pre-reduction conditions information of Example 5

[0063]

[0064]

[0065] Table 10. Summary table of reaction results of Example 5

[0066]

[0067] Example 6

[0068] The catalyst used 1 Pt@7 Fe / SiO2, and the catalyst pre-reduction and reaction conditions were the same as in Example 1. The lilac alcohol, catalyst amount, and solvent and amount information are shown in Table 11.

[0069] The reaction results of Example 6 are shown in Table 12.

[0070] Table 11. Summary table of pre-reduction conditions information of Example 6

[0071]

[0072]

[0073] Table 12. Summary table of reaction results of Example 6

[0074]

[0075] Example 7

[0076] The catalyst used 1 Pt@7 Fe / SiO2, and the catalyst preparation method and reactant feeding amount were the same as in Example 1. The reaction hydrogen pressure range was 0.1 MPa-3.0 MPa, the reaction temperature range was 473-623 K, and the reaction time was 30 min-12 h. The specific reaction condition information is shown in Table 13.

[0077] The reaction results of Example 7 are shown in Table 14.

[0078] Table 13. Summary table of pre-reduction conditions information of Example 7

[0079]

[0080]

[0081] Table 14. Summary of reaction results of Example 7

[0082]

[0083] Example 8

[0084] The 1Pt@7Fe / SiO2 catalyst was prepared using 10 μm SiO2, and other preparation methods, reactant feeding amount, and reaction conditions were the same as those of Example 1. The specific catalyst information is shown in Table 15.

[0085] The reaction results of Example 7 are shown in Table 16.

[0086] Table 15. Summary of catalyst information of Example 8

[0087]

[0088] Table 16. Summary of reaction results of Example 8

[0089]

[0090] As can be seen from the data in Tables 1-16, Fe and Pt alone cannot efficiently catalyze the hydrogenation deoxygenation of syringic alcohol, but when combined, the Pt@Fe / SiO2 catalyst can efficiently convert 2,6-dimethoxyphenol into aromatic compounds (benzene and phenol), the final product is single in kind, and the oxygen atoms in the raw material can be selectively hydrogenated and removed. The reaction rate and aromatic compound product distribution increase with increasing temperature, and after 12 h of reaction at 623 K, 2,6-dimethoxyphenol can be completely converted, and the selectivity of aromatic compounds is more than 80%. As can be seen from Example 1, the synergistic effect of Pt and Fe can effectively improve the conversion rate of 2,6-dimethoxyphenol.

[0091] The above merely describes preferred specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art, within the scope of the technical solutions disclosed in the present application and according to the technical solutions and inventive concepts of the present application, can make equivalent replacements or changes, which should be encompassed within the scope of protection of the present application.

Claims

1. A method for preparing an aromatic compound, characterized by, Specifically: The Pt@Fe / SiO2 catalyst is prepared by an equal-volume impregnation method: (1) First, the water absorption amount of SiO2 is determined. 1 g of dried SiO2 is placed in a beaker, and an appropriate amount of deionized water is added to the beaker using a pipette, following the principle of small amount and multiple times, and constantly stirring with a glass rod. When the SiO2 in the beaker is slightly sticky and no water seeps out, it is in a water-saturated state, and the volume of water added is recorded; (2) Pt and Fe compounds are dissolved in water to prepare a Pt solution with a concentration of 0.2 mol / L and a Fe solution with a concentration of 2.0 mol / L. Then, the corresponding volumes of Pt and Fe solutions are mixed according to the mass ratio of Pt, Fe to SiO2 in the catalyst design, and deionized water is added to make up the required liquid volume for equal-volume impregnation. SiO2 is added to the solution and mixed uniformly. After standing for 6-24 h, it is dried at 353 K-383 K for 12-24 h, and then calcined at 623 K-723 K under Ar for 1-4 h, and sealed for use; Before the reaction, a certain amount of catalyst is added to a high-temperature and high-pressure batch reactor, and reduced at 623-723 K under 1.0-3.0 MPa H2 for 10-30 min; after cooling, 2,6-dimethoxyphenol and an organic solvent are added to the batch reactor, sealed, and replaced with 3.0 MPa nitrogen three times to replace the air in the reactor. After evacuation, 0.1 MPa-3.0 MPa hydrogen is introduced, and the reaction temperature is 473-623 K. The reaction time is 30 min-12 h to produce phenol and benzene; The amount of the Pt@Fe / SiO2 catalyst used is 5-30% of the mass of 2,6-dimethoxyphenol; The organic solvent is any one of n-decane, n-dodecane, n-tetradecane, or n-hexadecane The amount of metal loaded on 1 g of SiO2 ranges from 0.01 to 0.015 g of Pt and 0.07 to 0.10 g of Fe. SiO2 is nano- or micro-sized silicon dioxide with a size of 100 nm-10 μm.

2. The method of claim 1, wherein, The Pt-containing compound is selected from one of chloroplatinic acid, platinum chloride, platinum bromide, platinum iodide, ammonium hexachloroplatinate, platinum nitrate, and tetraammine platinum nitrate; and the Fe-containing compound is selected from one of iron nitrate, iron chloride, iron bromide, iron sulfate, ferrous nitrate, ferrous chloride, ferrous bromide, and ferrous sulfate.

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