A preparation method of o-cresol and 2,6-xylenol

Abstract

The present invention belongs to the field of chemical engineering technology, and particularly relates to a preparation method of o-cresol and 2,6-xylenol, which comprises the following steps: gasifying phenol, methanol, and water and mixing them with a carrier gas, passing through a reactor filled with a catalyst, and carrying out a gas-phase alkylation reaction; the carrier gas is water gas and / or reaction tail gas; the catalyst comprises Fe2O3, Cr2O3, SiO2, and ZrO2 with a molar ratio of (200-500):(1-10):(1-10):(5-50). The preparation method of o-cresol and 2,6-xylenol provided by the present invention has the catalyst with a competitive adsorption effect on carbon dioxide, carbon monoxide, and hydrogen, reducing the number of highly active catalyst centers, increasing the reaction selectivity, having low unit consumption of methanol and phenol, and simultaneously greatly improving the service life of the catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical engineering, and particularly relates to a preparation method of o-cresol and 2,6-xylenol. Background Art

[0002] O-cresol is an important organic chemical intermediate, mainly used in the production of pesticides such as 2-methyl-4-chloro series herbicides, semiconductor encapsulation materials epoxy cresol novolac resin (ECN), spices, antioxidants, etc.

[0003] 2,6-Xylenol is the basic raw material for synthesizing the monomer of engineering plastic polyphenylene ether resin (PPO or PPE).

[0004] There are many production methods for o-cresol and 2,6-xylenol. Currently, it is mainly synthesized by one-step gas-phase catalysis of phenol and methanol. The reaction materials are introduced into a fixed-bed reactor, and in the presence of a catalyst, a mixture containing o-cresol and 2,6-xylenol is obtained. Then, o-cresol and 2,6-xylenol are separated by distillation. Currently, there are mainly two types of catalysts used for synthesizing 2,6-xylenol: one is an iron-based catalyst; the other is a magnesium-based catalyst. The magnesium-based catalyst has a low methanol decomposition rate during the production of 2,6-xylenol, but the reaction temperature is high and the selectivity of o-cresol and 2,6-xylenol is poor, about 95%-97%. The iron-based catalyst has a relatively large amount of methanol used in the synthesis of o-cresol and 2,6-xylenol, and the reaction ingredient is a molar ratio of phenol to methanol from 1:3 to 1:10. During the reaction process, most of the excess methanol decomposes and cannot be recovered. This leads to problems such as a methanol utilization rate of less than 60% and high production costs.

[0005] CN105032442A discloses a gas-phase reaction catalyst, a preparation method and an application thereof. The gas-phase reaction catalyst comprises a main catalyst and a main catalyst. The main catalyst comprises Fe2O3, Cr2O3, SiO2 and SnO2 with a molar ratio of (5000-10000):(25-100):(8-300):(100-2000). This gas-phase reaction catalyst has high activity, long service life and high selectivity. At the same time, the synthesis method of o-cresol and 2,6-xylenol provided by CN105032442A can reduce the decomposition of methanol, increase the conversion rate and selectivity of phenol, and the production capacity of o-cresol and 2,6-xylenol per unit volume of the catalyst. However, its defects are as follows: 1. The catalyst after reaction scrap cannot be regenerated by dissolution (because stannic oxide in the catalyst is reduced to elemental tin during use, and elemental tin reacts with nitric acid to form stannic acid, and stannic acid is insoluble in water, terminating the dissolution process), increasing production costs and environmental treatment costs; 2. The service life of the catalyst prepared by it can run continuously for more than 2000 hours. Although the service life is improved compared with that of magnesium-based and iron-vanadium-based catalysts, the catalyst is still frequently replaced during use; 3. The tail gas can only be solved by incineration, greatly wasting methanol. Summary of the Invention

[0006] In view of the defects existing in the prior art, the inventors of the present invention, based on research in this field and through a large number of experimental explorations, provide a preparation method of o-cresol and 2,6-xylenol, which comprises the following steps:

[0007] Vaporize phenol, methanol and water and mix them with a carrier gas, and pass through a reactor filled with a catalyst to carry out gas-phase alkylation reaction;

[0008] The carrier gas is water gas and / or reaction tail gas;

[0009] The catalyst comprises Fe2O3, Cr2O3, SiO2 and ZrO2 with a molar ratio of (200-500):(1-10):(1-10):(5-50).

[0010] In the present invention, the reaction tail gas is the reaction tail gas containing carbon dioxide, carbon monoxide, methane and hydrogen obtained by carrying out gas-phase alkylation reaction of phenol, methanol and water to synthesize o-cresol and 2,6-xylenol.

[0011] The inventors of the present invention have found that by using widely sourced water gas and reaction tail gas as carrier gases to introduce raw material gases into the reactor, and specifically selecting appropriate ratios of Fe2O3, Cr2O3, SiO2, and ZrO2 as catalysts, o-cresol and 2,6-xylenol are synthesized through gas-phase alkylation reaction. The catalyst has a competitive adsorption effect on carbon dioxide, carbon monoxide, and hydrogen, reducing the number of highly active catalyst centers and increasing the reaction selectivity. The single consumption of methanol and phenol is low, and at the same time, the catalyst life is greatly improved.

[0012] Based on the above technical features, compared with the prior art such as CN105032442A, the present invention has the following advantages: 1. The catalyst after reaction in the present invention can be regenerated by dissolution regeneration (since zirconium oxide in the catalyst is reduced to elemental zirconium during use and can dissolve in nitric acid to form zirconium nitrate), reducing production costs and treatment costs; 2. The catalyst prepared by CN105032442A can operate continuously for more than 2000 hours. Although the life is improved compared with magnesium-based and iron-vanadium-based catalysts, the catalyst is still frequently replaced during use. The catalyst of the present invention has been evaluated and demonstrated to have a life of not less than 7000 hours; 3. The reaction tail gas can be recycled, reducing the methanol ratio, reducing the consumption of methanol, and saving production costs.

[0013] Preferably, in the above method for preparing o-cresol and 2,6-xylenol, the volume percentage range of each component of the carrier gas is CO2 3-7%, CO 30-36%, H2 40-55%, CH4 2-5%, SO2 < 3 ppm, and the rest is nitrogen. Research shows that the technical effect of this application is closely related to the content ratio of each component in the water gas used. The further preferred content ratio range of each component is CO2 4-6%, CO 32-35%, H2 48-50%, CH4 3-4% and nitrogen, SO2 < 1 ppm.

[0014] Preferably, in the above method for preparing o-cresol and 2,6-xylenol, the catalyst comprises Fe2O3, Cr2O3, SiO2, and ZrO2 with a molar ratio of 371:(3.65-3.85):(4.0-4.8):(13-15). The present invention has found that by using Fe2O3, Cr2O3, SiO2, and ZrO2 with the above molar ratio as catalysts, the conversion rate of phenol is high, and at the same time, the selectivity of 2,6-xylenol is high.

[0015] Preferably, the preparation method of the catalyst comprises the following steps: calculating the molar ratio of the iron source compound, chromium source compound, silicon source compound and zirconium source compound according to the molar ratio of Fe2O3, Cr2O3, SiO2 and ZrO2, then adding the iron source compound, chromium source compound, silicon source compound and zirconium source compound into a reactor according to the calculated molar ratio, completely dissolving with water, adjusting the pH to 6.5 - 8.5, continuously stirring for 20 - 50 min and then standing for aging for 11 - 13 h, and filtering to obtain a filter cake;

[0016] Drying the filter cake at 150 - 200 °C for 6 - 10 h, adding graphite for tabletting, and then calcining at 400 - 600 °C for 4 - 10 h to obtain the product. More preferably, the pH is adjusted by dropwise adding ammonia water or an aqueous urea solution.

[0017] Further preferably, the iron source compound is selected from one or more of FeCl3, Fe(NO3)3·9H2O (iron(III) nitrate nonahydrate), and FeSO4;

[0018] The chromium source compound is selected from one or two of Cr(NO3)3·9H2O (chromium(III) nitrate nonahydrate) and CrCl3;

[0019] The silicon source compound is selected from one or two of Na2SiO3·9H2O (sodium silicate nonahydrate) and silica sol;

[0020] The zirconium source compound is selected from Zr(NO3)4·5H2O (zirconium nitrate).

[0021] Preferably, in the preparation method of o-cresol and 2,6-xylenol described above, the molar ratio of phenol, methanol, and water is 1:(1.5 - 10):(2 - 5).

[0022] Preferably, in the preparation method of o-cresol and 2,6-xylenol described above, the liquid hourly space velocity of the gas-phase alkylation reaction is 0.9 - 1.0 h -1 , the reaction pressure is 0.01 - 0.2 MPa (gauge pressure), and the reaction temperature is 340 - 360 °C.

[0023] Preferably, in the preparation method of o-cresol and 2,6-xylenol described above, for every 100 ml of the catalyst charged, the flow rate of the carrier gas is 15 - 150 L / h, more preferably 55 - 120 L / h.

[0024] The beneficial effects of the present invention are as follows:

[0025] The preparation method of o-cresol and 2,6-xylenol provided by the present invention has high utilization rates of raw materials phenol and methanol. The catalyst has a competitive adsorption effect on carbon dioxide, carbon monoxide and hydrogen, reducing the number of highly active catalyst centers, increasing the reaction selectivity, having low unit consumption of methanol and phenol, and simultaneously greatly increasing the service life of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the reaction equipment used for synthesizing o-cresol and 2,6-xylenol in the embodiment of the present invention;

[0027] In the figure, 1 is a raw material storage tank, 2 is a feed pump, 3 is a material flowmeter, 4 is a pressure gauge and a pressure gauge transmitter, 5 is a preheater, 6 is a reactor, 7 is a molten salt tank, 8 is a condenser, 9 is a reaction material storage tank, 10 is a regulating valve, and 11 is a water gas flowmeter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. For those not specifying specific techniques or conditions in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. For those reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through regular channels.

[0029] In the following embodiments and comparative examples:

[0030] The specific composition of the water gas used is: 5% CO2, 33% CO, 49% H2, 4% CH4, SO2 < 1 ppm, and the rest is nitrogen.

[0031] The reaction tail gas used is the reaction tail gas for preparing o-cresol and 2,6-xylenol, and its specific composition is: 4.4% CO2, 24.8% CO, 58.2% H2, 12.6% CH4.

[0032] The reaction equipment used for synthesizing o-cresol and 2,6-xylenol in the following embodiments and comparative examples is shown in Figure 1 . Among them, 1 is a raw material storage tank, 2 is a feed pump, 3 is a material flowmeter, 4 is a pressure gauge and a pressure gauge transmitter, 5 is a preheater, 6 is a reactor, 7 is a molten salt tank, 8 is a condenser, 9 is a reaction material storage tank, 10 is a regulating valve, and 11 is a water gas flowmeter. The lower parts of the preheater 5 and the reactor 6 are immersed in the molten salt tank 7, and the reaction temperature is regulated and controlled through the molten salt tank.

[0033] Example 1

[0034] 1. Preparation of the catalyst

[0035] The catalyst is Fe2O3, Cr2O3, SiO2 and ZrO2 with a molar ratio of 371:3.75:4.4:14. The specific preparation method is as follows:

[0036] Add 150 g of iron nitrate, 1.5 g of chromium nitrate, 1.25 g of sodium silicate nonahydrate and 4.29 g of zirconium nitrate into 3000 L of deionized water. After the raw materials are dissolved, adjust the pH to neutral (pH = 7) with ammonia water, stir for another 50 minutes, and let it age for 12 hours. Draw off the upper layer liquid and wash it twice, then filter. Dry the filtered cake in a forced-air oven at 200 °C for 5 hours. Press the catalyst into Φ3*3 tablets with a tablet press. Calcine the prepared catalyst at 450 °C for 6 hours to obtain the catalyst.

[0037] 2. Preparation of o-cresol and 2,6-xylenol

[0038] Load 100 ml of the prepared catalyst into the Figure 1 reactor.

[0039] Vaporize phenol, methanol and water, mix them with water gas, and pass through the reactor filled with the catalyst to carry out gas-phase alkylation reaction to synthesize o-cresol and 2,6-xylenol.

[0040] Among them, the liquid hourly space velocity is controlled at 0.95 h -1 , the reaction pressure is controlled at 0.18 MPa (gauge pressure), the reaction temperature: 340 - 350 °C, and the water gas flow rate: 55 - 120 l / h. The results are shown in Table 1 below.

[0041] Table 1

[0042]

[0043] Note: The reaction content in Table 1 is the gas-phase detection result of all products collected during the evaluation time, detected by area normalization, and is the mass percentage.

[0044] Methanol unit consumption = [(100 - o-cresol - 2,6-xylenol - 2,4,6-trimethylphenol) / 94 + o-cresol / 108 + 2,6-xylenol / 122 + 2,4,6-trimethylphenol / 136] * molar ratio of methanol to phenol in the formulation * 32 / (o-cresol + 2,6-xylenol)

[0045] Phenol unit consumption = [100 - phenol - o-cresol - 2,6-xylenol - 2,4,6-trimethylphenol + (o-cresol / 108 - 2,6-xylenol / 122 - 2,4,6 / 136) * 94] / (o-cresol + 2,6-xylenol).

[0046] The methanol unit consumption and phenol unit consumption are the amounts of o-cresol and 2,6-xylenol required to produce 1 ton of product.

[0047] Examples 2 - 6

[0048] Examples 2-6 are different from the catalyst described in Example 1 only in that the molar ratios of Fe2O3, Cr2O3, SiO2 and ZrO2 in the catalyst are different. The reaction was evaluated with a molar ratio of phenol: methanol: water = 1: 2.7: 2.8.

[0049] The catalysts of Examples 2-6 were used to prepare o-cresol and 2,6-xylenol according to the method of Example 1. The evaluation time was 7 days (168 h). The results are shown in Table 2 below.

[0050] Table 2

[0051]

[0052] (1) Comparing the data in Table 2 with the data in Table 1, when the carrier gas used in the reaction of the catalyst with a material composition of Fe2O3: Cr2O3: SiO2: ZrO2 = 371: 3.75: 4.4: 14 was replaced with the reaction tail gas, the effect of water gas could also be achieved. There was not much change in either the selectivity of 2,6-xylenol or the specific consumption of phenol and methanol.

[0053] (2) When the iron content in the catalyst decreased, the specific consumption of methanol decreased, but the selectivity of 2,6-xylenol decreased. The specific consumption of phenol also increased.

[0054] (3) It can be seen from the data in Table 1 and Table 2 that during the alkylation reaction, the water gas and the reaction tail gas as the carrier gas also participated in the reaction, reducing the high-boiling products produced after the reaction staying on the catalyst surface, reducing the coking of the catalyst, and prolonging the catalyst life.

[0055] (4) It can be seen from the data in Table 2 that for the above catalyst ratios, when reacting with the same proportion of materials, the consumption of phenol to produce the same mass of materials is optimal with the catalyst material composition of Fe2O3: Cr2O3: SiO2: ZrO2 = 371: 3.75: 4.4: 14. This is mainly reflected in less impurities and the lowest material consumption.

[0056] Comparative Example 1

[0057] Compared with Example 1, in Comparative Example 1, the catalyst of Example 1 was loaded into the reactor and nitrogen was introduced. The results are shown in Table 3 below.

[0058] Table 3

[0059]

[0060] It can be seen that nitrogen is used as the carrier gas, and the evaluation materials are phenol:methanol:water with a molar ratio of 1:2.8:2.8. After three months of operation, the selectivity of o-cresol and 2,6-xylenol deteriorates, and the unit consumption of phenol and methanol increases significantly, making it unsuitable for continued operation.

[0061] Comparative Example 2

[0062] Compared with Example 1, Comparative Example 2 uses the same catalyst, with the only difference being that no carrier gas is used. The results are shown in Table 4 below.

[0063] Table 4

[0064]

[0065] As can be seen from Table 4, without using a carrier gas, after one month of operation of the catalyst, the selectivity of o-cresol and 2,6-xylenol deteriorates, and the unit consumption of phenol and methanol also increases significantly. It is not suitable for continued operation.

[0066] The above embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing o-cresol and 2,6-xylenol, characterized in that, It includes the following steps: Vaporize phenol, methanol, and water and mix them with a carrier gas, then pass through a reactor filled with a catalyst to carry out gas-phase alkylation reaction; The carrier gas is water gas and / or reaction tail gas; The catalyst includes Fe2O3, Cr2O3, SiO2, and ZrO2 with a molar ratio of (200~500):(1~10):(1~10):(5~50).

2. The preparation method of o-cresol and 2,6-xylenol according to claim 1, characterized in that, The volume percentage range of each component of the carrier gas is 3-7% for CO2, 30-36% for CO, 40-55% for H2, 2-5% for CH4, SO2 < 3 ppm, and the rest is nitrogen.

3. The preparation method of o-cresol and 2,6-xylenol according to claim 2, characterized in that, The catalyst includes Fe2O3, Cr2O3, SiO2, and ZrO2 with a molar ratio of 371:(3.65~3.85):(4.0~4.8):(13~15).

4. The preparation method of o-cresol and 2,6-xylenol according to claim 3, characterized in that, The preparation method of the catalyst includes the following steps: Calculate the molar ratio of the iron source compound, chromium source compound, silicon source compound, and zirconium source compound according to the molar ratio of Fe2O3, Cr2O3, SiO2, and ZrO2, then add the iron source compound, chromium source compound, silicon source compound, and zirconium source compound to the reactor according to the calculated molar ratio, completely dissolve them with water, adjust the pH to 6.5-8.5, continue to stir for 20-50 min, then stand and age for 11-13 h, and filter to obtain a filter cake; Dry the filter cake at 150-200 °C for 6-10 h, add graphite to make tablets, and then calcine at 400-600 °C for 4-10 h to obtain the catalyst.

5. The preparation method of o-cresol and 2,6-xylenol according to claim 4, characterized in that, Adjust the pH by dropwise adding ammonia water or urea aqueous solution.

6. The preparation method of o-cresol and 2,6-xylenol according to claim 5, characterized in that, The iron source compound is selected from one or two of FeCl3 and Fe(NO3)3·9H2O; The chromium source compound is selected from one or two of Cr(NO3)3·9H2O and CrCl3; The silicon source compound is selected from one or two of Na2SiO3·9H2O and silica sol; The zirconium source compound is selected from Zr(NO3)4·5H2O.

7. The preparation method of o-cresol and 2,6-xylenol according to claim 6, characterized in that, The molar ratio of phenol, methanol, and water is 1:(1.5~10):(2~5).

8. The preparation method of o-cresol and 2,6-xylenol according to claim 7, characterized in that, The liquid hourly space velocity of the gas-phase alkylation reaction is 0.9 - 1.0 h -1 .

9. The preparation method of o-cresol and 2,6-xylenol according to claim 8, characterized in that, The reaction pressure of the gas-phase alkylation reaction is 0.01-0.2 MPa.

10. The preparation method of o-cresol and 2,6-xylenol according to claim 9, characterized in that, The reaction temperature of the gas-phase alkylation reaction is 340-360 °C.

11. The preparation method of o-cresol and 2,6-xylenol according to claim 10, characterized in that, For every 100 ml of catalyst loaded, the flow rate of the carrier gas is 15-150 L / h.

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