A carbon-based solid acid catalyst and its preparation method and application

Abstract

The present invention relates to a carbon-based solid acid catalyst and a preparation method and application thereof. The carbon source for preparing the carbon-based solid acid catalyst comes from green, non-toxic and low-cost potato starch, and a series of solid acids with different acidities are prepared to catalyze the hydrogenation reaction of nitrobenzene. It can be applied to the hydrogenation of nitrobenzene to prepare p-aminophenol. The present invention avoids the use of traditional liquid acid sulfuric acid to provide the acidic active sites required for the reaction, greatly alleviating the problems of equipment corrosion, environmental unfriendliness, difficulty in separating the catalyst from the product, etc. The catalyst used has good performance, the conversion rate of nitrobenzene is up to 100%, and the yield of p-aminophenol is up to 67.6%.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and specifically relates to a carbon-based solid acid catalyst and a preparation method thereof, and application of the catalyst in catalyzing the hydrogenation of nitrobenzene to prepare p-aminophenol. Background Art

[0002] Para-aminophenol (4-AP) is an important chemical raw material and pharmaceutical intermediate, which is widely used in the fields of medicine (production of paracetamol), dyes (synthetic sulfur dyes, acid dyes, fur dyes and azo dyes, etc.), rubber (synthetic phenylenediamine antioxidants), pesticides (synthetic plant growth regulator parachlorophenoxyacetic acid) and photosensitive materials (manufacturing developers).

[0003] The process routes for preparing 4-AP can be divided into the following types according to the raw materials: phenol and aniline coupling method (low raw material cost, but high consumption, high discharge of three wastes, complex low-temperature diazotization process, rarely used in industry), p-chloronitrobenzene method (serious pollution, difficult treatment of three wastes), hydroquinone amination method (raw material price is much higher than 4-AP price, no industrial significance), p-nitrophenol method (iron powder reduction method has simple process and few side reactions, but cumbersome operation, produces a large amount of iron mud and wastewater, and has serious pollution; catalytic hydrogenation method has high 4-AP yield, few by-products, and less discharge of waste liquid and waste residue), nitrobenzene reduction method (metal reduction method, with Al, Fe reduces NB to generate 4-AP under acidic conditions with high yield, large single metal consumption and serious environmental pollution; the electrochemical reduction method has the advantages of short process flow, high product purity, low cost and low pollution, but there are problems such as the selection of electrode plate materials and regeneration after electrode deactivation; the catalytic hydrogenation method uses a hydrogenation catalyst in an acidic environment to catalyze the hydrogenation rearrangement of NB to generate 4-AP. This method has a short process flow and low pollution).

[0004] NB is selectively catalytically hydrogenated in an acidic environment and under the conditions of a hydrogenation catalyst to generate an intermediate product, phenylhydroxylamine (PHA), which is then rearranged by Bamberger to obtain 4-AP. Some foreign companies have adopted this method for production, and many domestic units are conducting research and development of this process. This method often uses concentrated sulfuric acid (mass fraction > 10%) as an acid catalyst for PHA rearrangement, which has problems such as severe equipment corrosion, environmental unfriendliness, and difficulty in separating the catalyst from the product.

[0005] Therefore, developing non-traditional liquid acids that can replace concentrated sulfuric acid and designing green reaction processes have become the focus and hotspot of research. Summary of the invention

[0006] The purpose of the present invention is to provide a carbon-based solid acid catalyst and a preparation method thereof and application thereof in catalyzing the hydrogenation of nitrobenzene to prepare p-aminophenol.

[0007] The present invention uses potato starch from green biomass as a carbon source, prepares a series of carbon-based solid acids with different acidities by a one-pot hydrothermal method to replace traditional liquid acids, and uses Pt / C or Pd / C as a hydrogenation catalyst for application in the reaction of catalyzing NB hydrogenation to prepare 4-AP.

[0008] The technical scheme of the present invention is: a carbon-based solid acid catalyst, characterized in that the carbon source of the carbon-based solid acid catalyst is selected from potato starch, and a series of carbon-based solid acid catalysts with different acidities are obtained by sulfonation with sulfuric acid of different concentrations.

[0009] The present invention also provides a method for preparing a carbon-based solid acid catalyst, which is characterized in that concentrated sulfuric acid with different mass fractions is prepared, and is slowly added into a prepared potato starch water mixed solution, the mixed solution is evenly stirred and transferred to a high-pressure hydrothermal autoclave, and is placed in a heating box for heating. After naturally cooling to room temperature, it is centrifugally filtered, washed, and dried to obtain a series of carbon-based solid acid catalysts with different acidities.

[0010] Preferably, the different mass fractions of concentrated sulfuric acid are 89wt%~98wt%, the stirring time is: 0.5~1 hour, the reaction time is: 1~10 hours, and the heating temperature is: 60~80 0 C, heating time: 3~6 hours.

[0011] Preferably, the acidity of the prepared carbon-based solid acid is 0.282~2.316mmol / g.

[0012] The present invention also provides an application of the carbon-based solid acid catalyst for catalyzing the hydrogenation of nitrobenzene to prepare p-aminophenol: the carbon-based solid acid, a hydrogenation catalyst, hexadecyltrimethylammonium bromide, deionized water, and nitrobenzene are added to a high-pressure reactor, and reacted under magnetic stirring to obtain the product p-aminophenol.

[0013] Preferably, the amount of the carbon-based solid acid catalyst used is 1 mg to 1 g.

[0014] Preferably, the type of hydrogenation catalyst is Pd / C or Pt / C, the metal loading is 1wt%~5wt%, and the amount of hydrogenation catalyst used is 1-10mg.

[0015] Preferably, the amount of the surfactant cetyltrimethylammonium bromide (CTAB) used is 1-10 mg.

[0016] Preferably, the amount of nitrobenzene used is 0.02~0.36mL.

[0017] Preferably, the reaction temperature is 25-100° C., and the reaction time is 4-12 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The carbon source used in the synthesis of carbon-based solid acid catalysts comes from potato starch, which is green, natural, non-toxic, harmless, low-priced, and prepared in one pot. The method is simple and easy to scale up. The most important thing is that the series of acid catalysts synthesized by this method have regular morphology and high yield, so that the solid acid catalyst shows good catalytic activity and selectivity in many acid-catalyzed reactions. It effectively alleviates and solves the problems of severe equipment corrosion, environmental unfriendliness, and difficulty in separating catalysts from products when traditional liquid acids are used as acid catalysts. DETAILED DESCRIPTION

[0020] The detailed details contained in the following examples are used to further illustrate the technical solutions of the present invention, but are not limited thereto. The experimental methods described in the following examples are conventional methods unless otherwise specified. The chemical reagents and materials described can be obtained from commercial sources unless otherwise specified.

[0021] Example 1

[0022] In the first step, at room temperature, put 10g of potato starch into a 100mL beaker, add 50mL of deionized water, and place it on a magnetic stirrer to stir evenly to obtain a milky starch-water mixture.

[0023] In the second step, 10 mL of 98 wt % concentrated sulfuric acid was added with a certain amount of deionized water and stirred for 20 minutes to obtain a diluted concentrated sulfuric acid aqueous solution.

[0024] The third step is to take 10 mL of the diluted concentrated sulfuric acid aqueous solution and add it to the prepared starch water mixed solution, and stir for 30 minutes to obtain a uniform mixed solution.

[0025] In the fourth step, the mixed solution in the beaker was transferred to a 100 mL high pressure hydrothermal autoclave, which was placed in a heating box and heated at 180° C. for 4 hours.

[0026] Step 5: After cooling naturally to room temperature, centrifuge and filter, wash several times with ethanol and deionized water respectively, until no SO4 is detected in the filtrate. 2- Then it was placed in a vacuum drying oven for drying at 80°C for 24 hours until it was completely dried to obtain a carbon-based solid acid catalyst with an acidity of 1.962 mmol / g.

[0027] Step 6: Take 0.12mL NB, 2mg CTAB, 2mg 3wt% Pt / C, 200mg solid acid, and 10mL deionized water, add them to a 25mL stainless steel autoclave in sequence, stir evenly, and tighten the autoclave cover. Introduce hydrogen to replace the air in the autoclave, and repeat 3 times. Slowly heat the autoclave to 85°C, turn on the agitator at 800rpm, and start the timing reaction. After 10 hours of reaction, stop the reaction, cool the reaction to room temperature, filter the reaction solution, and analyze the filtrate by high performance liquid chromatography. The analysis results show that the conversion rate of NB is 100% and the yield of 4-AP is 57.8%.

[0028] Example 2

[0029] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 0.282 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 5.0%.

[0030] Example 3

[0031] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 0.354 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 5.3%.

[0032] Example 4

[0033] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 0.438 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 7.8%.

[0034] Example 5

[0035] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 1.454 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 21.8%.

[0036] Example 6

[0037] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 1.650 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 26.5%.

[0038] Example 7

[0039] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 1.776 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 34.5%.

[0040] Example 8

[0041] The other steps were the same as in Example 1, except that sulfuric acid of different dilution concentrations was used, and finally a carbon-based solid acid catalyst with an acidity of 2.316 mmol / g was obtained. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 46.2%.

[0042] Example 9

[0043] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 1 mg 1 wt% Pt / C. The reaction results showed that the conversion rate of NB was 91.8%, and the yield of 4-AP was 6.4%.

[0044] Example 10

[0045] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 1 mg 3wt% Pt / C. The reaction results showed that the conversion rate of NB was 98.2%, and the yield of 4-AP was 53%.

[0046] Embodiment 11

[0047] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 3 mg 3 wt% Pt / C. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 52.8%.

[0048] Example 12

[0049] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 1 mg 5wt% Pt / C. The reaction results showed that the conversion rate of NB was 90.3%, and the yield of 4-AP was 42.3%.

[0050] Embodiment 13

[0051] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 2 mg 5 wt% Pt / C. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 42.3%.

[0052] Embodiment 14

[0053] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 1 mg 3wt% Pt / C. The reaction results showed that the conversion rate of NB was 91.9% and the yield of 4-AP was 20.4%.

[0054] Embodiment 15

[0055] The other steps were the same as in Example 1, except that the hydrogenation catalyst used was 1 mg 3wt% Pt / C and the amount of solid acid used was 0 mg. The reaction results showed that the conversion rate of NB was 100% and the yield of 4-AP was 0%.

[0056] Example 16

[0057] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g and the amount used was 100 mg. The reaction results showed that the conversion rate of NB was 100% and the yield of 4-AP was 29.5%.

[0058] Embodiment 17

[0059] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g and the amount used was 200 mg. The reaction results showed that the conversion rate of NB was 100% and the yield of 4-AP was 46.2%.

[0060] Embodiment 18

[0061] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g and the amount used was 300 mg. The reaction results showed that the conversion rate of NB was 100% and the yield of 4-AP was 66.8%.

[0062] Embodiment 19

[0063] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g and the amount used was 400 mg. The reaction results showed that the conversion rate of NB was 100% and the yield of 4-AP was 20.1%.

[0064] Embodiment 20

[0065] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g, the reaction temperature was 30°C, and the reaction time was 1 hour. The reaction results showed that the conversion rate of NB was 89.6%, and the yield of 4-AP was 1.2%.

[0066] Embodiment 21

[0067] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g, the reaction temperature was 30°C, and the reaction time was 3 hours. The reaction results showed that the conversion rate of NB was 90.6%, and the yield of 4-AP was 2.8%.

[0068] Embodiment 22

[0069] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g, the reaction temperature was 30°C, and the reaction time was 5 hours. The reaction results showed that the conversion rate of NB was 90.3%, and the yield of 4-AP was 4.3%.

[0070] Embodiment 23

[0071] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g, the reaction temperature was 30°C, and the temperature was raised to 85°C after 5 hours of reaction, and the reaction was continued for 5 hours. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 44.9%.

[0072] Embodiment 24

[0073] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g, and the amount of NB used was 0.06 mL. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 67.6%.

[0074] Embodiment 25

[0075] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 2.316 mmol / g and the amount of NB used was 0.24 mL. The reaction results showed that the conversion rate of NB was 95.9% and the yield of 4-AP was 29.1%.

[0076] Embodiment 26

[0077] The other steps were the same as in Example 1, except that 132.6 mg PHA was used instead of NB. The reaction results showed that the conversion rate of PHA was 100%, and the yield of 4-AP was 36.9%.

[0078] Embodiment 27

[0079] The other steps were the same as in Example 1, except that 132.6 mg of PHA was used to replace NB, and the amount of solid acid used was 0 mg. The reaction results showed that the conversion rate of PHA was 100%, and the yield of 4-AP was 0%.

[0080] Embodiment 28

[0081] The other steps were the same as in Example 1, except that 132.6 mg PHA was used instead of NB, and N2 was used instead of H2. The reaction results showed that the conversion rate of PHA was 95.7%, and the yield of 4-AP was 44.6%.

[0082] Embodiment 29

[0083] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 1.776 mmol / g. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 34.5%.

[0084] Embodiment 30

[0085] The other steps were the same as in Example 1, except that the acidity of the solid acid used was 1.776 mmol / g, and the catalyst was used 3 times. The reaction results showed that the conversion rate of NB was 100%, and the yield of 4-AP was 0.7%.

[0086] Matters not covered by the present invention are known technologies.

Claims

1. An application of a carbon-based solid acid catalyst, characterized in that: It is used for catalyzing the hydrogenation of nitrobenzene to prepare p-aminophenol, comprising the following steps: The first step is to put 10g potato starch into a 100mL beaker at room temperature, add 50mL deionized water, and stir evenly on a magnetic stirrer to obtain a milky white starch-water mixed solution; In the second step, 10 mL of 98 wt% concentrated sulfuric acid was added with a certain amount of deionized water and stirred for 20 minutes to obtain a diluted concentrated sulfuric acid aqueous solution; Step 3: Take 10 mL of the diluted concentrated sulfuric acid aqueous solution and add it to the prepared starch water mixed solution, stir for 30 minutes to obtain a uniform mixed solution; Step 4: transfer the mixed solution in the beaker to a 100 mL high pressure hydrothermal autoclave, place it in a heating box, and heat at 180 °C for 4 hours; Step 5: After cooling naturally to room temperature, centrifuge and filter, wash several times with ethanol and deionized water respectively, until no SO4 is detected in the filtrate. 2- ; Then put it into a vacuum drying oven for drying at 80 ° C for 24 hours until it is completely dried to obtain a carbon-based solid acid catalyst with an acidity of 2.316 mmol / g; Step 6: Take 0.06mL nitrobenzene NB, 2mg surfactant hexadecyltrimethylammonium bromide CTAB, 2mg Pt / C hydrogenation catalyst with a metal loading of 3wt%, 200mg carbon-based solid acid catalyst, and 10mL deionized water, add them to a 25mL stainless steel autoclave in sequence, stir evenly, and tighten the autoclave cover; introduce hydrogen to replace the air in the autoclave, and repeat this process 3 times; slowly heat the stainless steel autoclave to 85°C, turn on the agitator at 800rpm, and start timing the reaction; stop the reaction after 10 hours of reaction, cool the reaction to room temperature, filter the reaction solution, and analyze the filtrate by high performance liquid chromatography.