An activated carbon-supported iron-based catalyst and its application in phenol alkylation reaction

Abstract

The invention discloses an activated carbon-supported iron-based catalyst and its application in phenol alkylation reaction, belonging to the technical field of petrochemical industry. The activated carbon-supported iron-based catalyst of the present invention includes active component, auxiliary agent and activated carbon carrier, wherein the activated carbon carrier is acid-treated coconut shell charcoal, the active component is Fe, the auxiliary agent is Bi, the active component accounts for 1-30wt% of the total mass of the catalyst, and the auxiliary agent accounts for 0.01-1wt% of the total mass of the catalyst; by dissolving the active component precursor and the auxiliary agent precursor in water, by equal volume impregnation and excessive impregnation on the acid-treated coconut shell charcoal, after drying, roasting at 300-1000°C for 0.5-72h, obtaining an activated carbon-supported iron-based catalyst, catalyzing phenol and methanol to react to prepare 2,6-dimethylphenol, the reaction temperature is low, the by-product is few, and the energy consumption and production cost are significantly reduced, and there is a broad application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and particularly relates to an activated carbon-supported iron-based catalyst and application thereof in phenol alkylation reaction. Background Art

[0002] 2,6-Dimethylphenol is an important chemical raw material and fine chemical intermediate. It can be used as a monomer for the synthesis of engineering plastics polyphenylene ether and modified polyphenylene ether. It can also be used as an intermediate for the production of pesticides such as metalaxyl, furalaxyl, furamide, methylfuran, isobutachlor and dimethochlor. It has broad prospects for industrial application.

[0003] At present, there are four main methods for the production of 2,6-dimethylphenol at home and abroad, namely, natural extraction and separation method, toluene chlorination and hydrolysis method, o-toluidine diazotization and hydrolysis method and phenol alkylation method.

[0004] Initially, 2,6-dimethylphenol was separated from coal tar and petroleum cracking products, and the product quality was poor and the yield was low. The toluene chlorination hydrolysis method and the o-toluidine diazotization hydrolysis method have been gradually eliminated due to serious pollution, low yield, and the inability to carry out liquid phase reactions continuously.

[0005] In 1945, N. Cullinane et al. first used phenol and methanol for gas phase catalytic methylation reaction to synthesize 2,6-dimethylphenol. MgO-based catalysts have excellent catalytic activity in this reaction. For example, US3446856A, US4041085A, US4201880A, US4554267A, etc. all provide MgO-based catalysts. Although MgO-based catalysts have good ortho-selectivity, a high proportion of para-methylated products with marginal effects are still produced, and the ortho-selectivity needs to be further improved. More importantly, MgO-based catalysts are high-temperature catalysts, and the temperature required for the reaction is very high, reaching 450-550°C, which results in the disadvantages of high reaction energy consumption and poor catalyst stability.

[0006] Since MgO-based catalysts still have certain defects in terms of reaction energy consumption and catalytic activity, iron-based catalysts have gradually replaced magnesium-based catalysts. Iron-based catalysts have made great improvements in reducing reaction temperature, improving the selectivity of ortho-methylation and phenol conversion, for example, US3716589A, US3953529A, US4024195A, US4227024A and other patents all disclose their respective iron-based catalysts. However, due to the high preparation cost of iron-based catalysts, the strict requirements for preparation and reaction conditions, and the short service life of the catalyst, its industrial application is still not ideal.

[0007] The carrier of the iron-based catalyst used in the alkylation reaction is usually a composite oxide, and the specific surface area of ​​the oxide is mostly 50m 2 / g, and the catalyst sintering after the reaction leads to a serious reduction in specific surface area. Therefore, it is urgent to research and develop an iron-based catalyst with high activity and high specific surface area. Summary of the invention

[0008] In view of this, the purpose of the present invention is to provide an activated carbon-supported iron-based catalyst and its application in the alkylation reaction of phenol. The present invention uses an activated carbon-supported iron-based catalyst to catalyze the reaction of phenol and methanol under normal pressure.

[0009] 2,6-dimethylphenol should be prepared. The catalyst preparation method is simple, the catalytic reaction temperature is low, the catalytic activity is high, the product 5 selectivity is high, and the amount of metal used can be greatly reduced. Compared with the existing process, the activated carbon-supported nano-iron oxide

[0010] The technology of using catalysts to synthesize 2,6-dimethylphenol has obvious advantages.

[0011] The object of the present invention is achieved by the following methods:

[0012] The present invention provides an activated carbon-supported iron-based catalyst, the iron-based catalyst comprising an active component, a promoter

[0013] The active component is Fe, the auxiliary agent is Bi, the active component accounts for 1-30wt% of the total mass of the catalyst, and the auxiliary agent accounts for 0.01-1wt% of the total mass of the catalyst.

[0014] Based on the above technical solution, further, the active component accounts for 1-10wt% of the total mass of the catalyst, and the auxiliary agent accounts for 0.01-0.5wt% of the total mass of the catalyst.

[0015] Another aspect of the present invention provides a method for preparing the above-mentioned activated carbon-supported iron-based catalyst, which mainly comprises the following steps:

[0016] Steps: The active component precursor and the auxiliary agent precursor are dissolved in water, impregnated on the coconut shell charcoal treated with acid by equal volume impregnation and excess impregnation, dried, and calcined at 300-1000°C for 0.5-72h to obtain an activated carbon-supported iron-based catalyst.

[0017] Based on the above technical solution, further, the active component precursor includes ferric nitrate, ferric chloride or ferric sulfate, and the auxiliary agent precursor includes bismuth nitrate and sodium bismuthate.

[0018] Based on the above technical solution, further, the drying temperature is 50-200°C, preferably 100-120°C; the drying time is 1-72h, preferably 6-24h.

[0019] Based on the above technical solution, further, the roasting temperature is 300-800°C and the roasting time is 2-8h.

[0020] Based on the above technical solution, the specific process of acid treatment is as follows: put the coconut shell charcoal into an autoclave, add excess acid solution, disperse it evenly, treat it at 100-250°C for 1-24h, cool it to room temperature, wash it with water until it is neutral,

[0021] After drying.

[0022] 5 Based on the above technical solution, further, the acid used in the acid treatment process is concentrated sulfuric acid or concentrated nitric acid.

[0023] The temperature is 150-200°C; the processing time is 1-4h.

[0024] The present invention also provides a method for preparing 2,6-dimethylphenol by catalyzing phenol, comprising the following steps: introducing a mixed solution of phenol, methanol and water into a fixed bed reactor filled with the iron-based catalyst to react and obtain 2,6-dimethylphenol.

[0025] Based on the above technical solution, further, the reaction temperature is 300-450°C, preferably 350°C.

[0026] Based on the above technical solution, further, the reaction pressure is normal pressure.

[0027] Based on the above technical solution, further, the molar ratio of phenol, methanol and water is 1:2-5:1-5, preferably 1:5:3.

[0028] The beneficial effects of the present invention compared with the prior art are as follows:

[0029] The activated carbon-supported iron-based catalyst of the present invention reduces the amount of metal used, has a very large specific surface area, and improves the reaction activity and the selectivity of the product 2,6-dimethylphenol; the catalyst synthesis method of the present invention is simple, the metal utilization rate is high, the initial reaction temperature of the catalytic reaction of phenol to dimethylphenol is low, and the by-products are small, thereby simplifying the preparation process and reducing energy consumption and production costs; the process has broad development space and great market application value, and is more in line with the requirements of sustainable development. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative labor all fall within the protection scope of the present invention.

[0031] Example 1

[0032] Activated carbonic acid treatment process: Weigh 200g coconut shell activated carbon, put it in a 500mL autoclave with a polytetrafluoroethylene liner, slowly add 100mL of concentrated sulfuric acid, disperse it evenly, seal the autoclave and put it in an oven, let it stand at 160℃ sulfonation temperature for 90min, cool it down to room temperature after the time is reached, slowly pour the mixture into a beaker filled with a large amount of deionized water, filter it under reduced pressure, wash it with 80℃ deionized water until it is neutral, and dry it in an oven at 110℃ overnight to obtain an activated carbon carrier with a specific surface area of ​​1035m 2 / g.

[0033] Weigh 101.0 g of Fe(NO3)3·9H2O and 0.4937 g of Bi(NO3)3·5H2O and dissolve them in 200 ml of water. After complete dissolution, add 200 g of activated carbon, let it stand at room temperature overnight, and then dry it at 100°C for 24 hours. Calcine the above catalyst at 500°C in a muffle furnace for 5 hours to obtain catalyst A1.

[0034] Example 2

[0035] The process is the same as that of Example 1, except that the amount of Bi(NO3)3·5H2O is changed to 0.987 g to obtain catalyst A2.

[0036] Example 3

[0037] The process is the same as that of Example 1, except that the sulfonation temperature is changed to 100° C., and catalyst A3 is obtained.

[0038] Example 4

[0039] The process is the same as that in Example 1, except that the sulfonation time is changed to 24 h, and catalyst A4 is obtained.

[0040] Example 5

[0041] The process is the same as that in Example 1, except that the sulfonation time is changed to 1 h, and catalyst A5 is obtained.

[0042] Example 6

[0043] The process is the same as that of Example 1, except that the solvent water in the nitrate dissolution process is replaced by methanol to obtain catalyst A6.

[0044] Example 7

[0045] The process is the same as that of Example 1, except that the solvent water in the nitrate dissolution process is replaced with ethanol to obtain catalyst A7.

[0046] Example 8

[0047] The process is the same as that of Example 1, except that the calcination temperature is changed to 1000° C. to obtain catalyst A8.

[0048] Example 9

[0049] The process is the same as that in Example 1, except that the calcination temperature is changed to 300° C. to obtain catalyst A9.

[0050] Example 10

[0051] The process is the same as that in Example 1, except that the calcination time is changed to 30 min, and catalyst A10 is obtained.

[0052] Embodiment 11

[0053] The process is the same as that in Example 1, except that the calcination time is changed to 72 h, and catalyst A11 is obtained.

[0054] Example 12

[0055] Catalyst A1 was pressed into 20-40 mesh particles, 8 g was weighed and loaded into a 304 stainless steel fixed bed reactor. The raw materials were phenol, methanol and water. The liquid was metered into the reactor through a horizontal flow pump. The reaction temperature was controlled at 350 °C, atmospheric pressure, and a mass space velocity of 1 h -1 , the carrier gas was N2, the flow rate was 10 mL / min, the molar ratio of the raw materials was changed, and chromatographic analysis was performed after 24 hours of reaction, and no impurities such as p-dimethylphenol and m-dimethylphenol were detected. The reaction results are shown in Table 1.

[0056] Table 1. Catalyzed reaction results of phenol to dimethylphenol

[0057] Phenol / methanol / water (molar ratio) Phenol conversion rate (%) 2,6-Dimethylphenol selectivity (%) 1:5:1 99.1 92.6 1:5:2 99.5 93.1 1:5:3 99.4 94.2 1:5:4 98.1 91.5

[0058] Embodiment 13

[0059] The specific process is the same as Example 12, except that the phenol / methanol / water (molar ratio) is 1:5:3, and the reaction space velocity is changed. The specific experimental results are shown in Table 2.

[0060] Table 2. Catalyzed reaction results of phenol to dimethylphenol

[0061] <![CDATA[Air speed h -1 > Phenol conversion rate (%) 2,6-Dimethylphenol selectivity (%) 0.1 99.8 72.6 0.5 99.3 94.1 1 99.4 94.2 1.5 86.2 90.8

[0062] Embodiment 14

[0063] The specific process is the same as Example 12, except that the phenol / methanol / water (molar ratio) is 1:5:3, and the reaction temperature is changed. The specific experimental results are shown in Table 3.

[0064] Table 3. Catalyst-catalyzed reaction results of phenol to dimethylphenol

[0065]

[0066] Embodiment 15

[0067] The specific process is the same as Example 12, except that the phenol / methanol / water (molar ratio) is 1:5:3, and the flow rate of nitrogen in the reaction is changed. The specific experimental results are shown in Table 4.

[0068] Table 4. Catalyzed reaction results of phenol to dimethylphenol

[0069]

[0070] Example 16

[0071] The specific process is the same as Example 12, except that the molar ratio of phenol / methanol / water is 1:5:3, and the type of inert gas in the reaction is changed. The specific experimental results are shown in Table 5.

[0072] Table 5. Catalyst-catalyzed reaction results of phenol to dimethylphenol

[0073]

[0074] Embodiment 17

[0075] The specific process is the same as in Example 12, except that the molar ratio of phenol / methanol / water is 1:5:3, and the air velocity is 1h -1 , the reaction was carried out continuously, the catalyst could operate stably for 2500 hours, the average conversion rate of phenol was 99%, and the average selectivity of 2,6-dimethylphenol was 92.4%.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An activated carbon-supported iron-based catalyst, the iron-based catalyst comprising an active component, an auxiliary agent and an activated carbon carrier, the activated carbon carrier being acid-treated coconut shell charcoal, the active component being Fe, the auxiliary agent being Bi, the active component accounting for 1 to 30 wt% of the total mass of the catalyst, and the auxiliary agent accounting for 0.01 to 1 wt% of the total mass of the catalyst; The method for preparing the activated carbon-supported iron-based catalyst comprises the following steps: The active component precursor and the auxiliary agent precursor are dissolved in water, impregnated on the coconut shell charcoal treated with acid by equal volume impregnation and excess impregnation, dried, and calcined at 300-1000° C. for 0.5-72 h to obtain an activated carbon-supported iron-based catalyst; The specific process of acid treatment is: put coconut shell charcoal into an autoclave, add excess acid solution, disperse it evenly, treat it at 100-250℃ for 1-24h, cool it to room temperature, wash it with water until it is neutral, and dry it to obtain it; the acid used in the acid treatment process is concentrated sulfuric acid or concentrated nitric acid.

2. The iron-based catalyst according to claim 1, characterized in that The active component accounts for 1-10wt% of the total mass of the catalyst, and the auxiliary agent accounts for 0.01-0.5wt% of the total mass of the catalyst.

3. The iron-based catalyst according to claim 1, characterized in that The active component precursor is ferric nitrate, ferric chloride or ferric sulfate, and the auxiliary agent precursor is bismuth nitrate or sodium bismuthate.

4. The iron-based catalyst according to claim 1, characterized in that The drying temperature is 50-200°C; the drying time is 1-72h; the roasting temperature is 300-800°C, and the roasting time is 2-8h.

5. The iron-based catalyst according to claim 1, characterized in that The acid treatment process temperature is 150-200°C; the treatment time is 1-4h.

6. A method for preparing 2,6-dimethylphenol by catalyzing phenol, characterized in that: The method comprises the following steps: introducing a mixed solution of phenol, methanol and water into a fixed bed reactor loaded with the iron-based catalyst according to claim 1 or 2 to react and obtain 2,6-dimethylphenol.

7. The method according to claim 6, characterized in that The reaction temperature is 300-450°C.

8. The method according to claim 6, characterized in that The molar ratio of phenol, methanol and water is 1:2-5:1-5.

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