A method for preparing a porous solid acid catalyst

Abstract

The present application belongs to the field of solid acid catalysts, and particularly relates to a preparation method of a porous solid acid catalyst, comprising the following steps: step i: using an organic solvent to reflux and swell a porous resin at 80 DEG C, and filtering the swollen porous resin to remove the excess solvent; step ii: loading the porous resin into a reactor, and introducing SO3 gas diluted by an inert gas, and sulfonating the porous resin at 120 DEG C and 140 DEG C for 2 h respectively under a certain reaction pressure, then increasing the temperature to 170 DEG C, and continuing to sulfonate for 1 h, and then placing the sulfonated sample in an air environment at room temperature for 5-12 h; step iii: step-by-step acid washing the sulfonated sample, and sequentially using concentrated sulfuric acid with mass concentrations of 80%, 50%, 30%, 10% and 5% to wash the sulfonated resin, and finally washing the sulfonated resin with deionized water for several times, and then drying at 100 DEG C overnight to obtain the porous solid acid catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid acid catalysts, and particularly relates to a preparation method of a porous solid acid catalyst. BACKGROUND

[0002] Cyclohexyl acetate has banana, apple and other fruit flavors, is a colorless or slightly yellow transparent liquid, and is mainly used for preparing apple, banana and raspberry flavors, and has a wide application in food and cosmetic industries. It can also be used as a paint and paint solvent.

[0003] In industry, cyclohexyl acetate is usually synthesized from cyclohexanol and acetic acid with concentrated sulfuric acid as a catalyst. After the reaction, the reaction liquid needs to be washed with lye and water until it is neutral, and then dried and distilled for purification. However, the concentrated sulfuric acid catalyst seriously corrodes the equipment, and a large amount of waste acid needs to be treated. At the same time, the wastewater generated during the reaction and purification process, as well as the added cyclohexane, will have an impact on the environment. Therefore, it is of great practical significance to develop a new process for synthesizing cyclohexyl acetate.

[0004] CN102060697A discloses a synthesis process of cyclohexyl acetate, which uses copper p-toluenesulfonate instead of concentrated sulfuric acid to catalyze the esterification of cyclohexanol and acetic acid to synthesize cyclohexyl acetate. Although the product yield is 96.7% under certain conditions (without separation), the generation of wastewater cannot be avoided, and the introduction of cyclohexane also brings difficulties to separation. EP0461580A2 and USP5254721 disclose a method for catalytically synthesizing cyclohexyl acetate by using a tungsten-containing heteropoly acid catalyst for the reaction of acetic acid and cyclohexene. The conversion rate of cyclohexene is 95.2% and the selectivity of cyclohexyl acetate is 99.2% under the conditions of 0.5 Mpa and 130℃ for 0.5 h. However, the tungsten-containing heteropoly acid catalyst is not easy to separate from the reaction material.

[0005] CN107434767A discloses a method for preparing cyclohexanol and cyclohexyl acetate from cyclohexene and acetic acid, which uses H-type macroporous strong acid cation exchange resin as a catalyst. CN102875371A discloses a method for synthesizing cyclohexyl acetate from cyclohexene, which also uses a sulfonic acid-based cation exchange resin as a catalyst, with an acid strength less than or equal to 3, a specific surface area greater than or equal to 30 m 2 / g, and an acid exchange capacity greater than or equal to 4. The main problem of the current cation exchange resin is that the acid content is not high, the resin is easy to break, and the stability of the resin catalyst is poor.

[0006] The main problem that restricts the industrial application of solid acid instead of liquid acid is the low acid exchange capacity of the resin catalyst, which leads to low acid catalytic reaction activity and poor reaction selectivity, and cannot meet the requirements of practical reaction application as a heterogeneous catalyst. SUMMARY

[0007] The purpose of the present application is to solve the problems in the background art, and provide a preparation method of a porous solid acid catalyst. The traditional macroporous resin is sulfonated and strengthened, SO3 is used as a strong oxidizing agent to react with the resin to improve the acid exchange capacity and strength of the resin. The method can better solve the problems of low acid exchange capacity and resin strength.

[0008] The above technical purposes of the present application are achieved by the following technical solutions:

[0009] A preparation method of a porous solid acid catalyst, step i, the porous resin is refluxed and swelled at 80 DEG C by using an organic solvent, and the swelled porous resin is filtered to remove the excess solvent;

[0010] Step ii, the porous resin is loaded in a reactor, and SO3 gas diluted by an inert gas is introduced, and the sulfonation is carried out at 120 DEG C and 140 DEG C for 2 h respectively under a certain reaction pressure, then the temperature is increased to 170 DEG C, and the sulfonation is continued for 1 h, and after the sulfonation is completed, it is placed in an air environment at room temperature for 5-12 h;

[0011] Step iii, the sulfonated sample is subjected to step-by-step acid washing, and the sulfonated resin is washed with concentrated sulfuric acid with a mass concentration of 80%, 50%, 30%, 10% and 5% in turn, and finally washed with deionized water several times, and the porous solid acid catalyst can be obtained after drying at 100 DEG C overnight.

[0012] The porous resin in the present application is macroporous polystyrene sulfonic acid resin, nafion perfluoro resin, nafion perfluoro sulfonic acid resin, polytrifluorostyrene resin and polytrifluorostyrene sulfonated resin.

[0013] The organic solvent in the present application is one or more of 1,1-dichloroethane, 1,2-dichloroethane, tetrachloroethylene, carbon tetrachloride and chloroform.

[0014] The reactor in the present application is one of a tubular reactor and a kettle type reactor.

[0015] The SO3 gas diluted by the inert gas in the present application is one of nitrogen, argon or helium, and the molar ratio of SO3 to inert gas is 1:1-1:10.

[0016] The sulfonation reaction pressure in the present application is 0.1-2.0 Mpa.

[0017] In summary, the beneficial effects produced by the above technical solutions are:

[0018] The present application is based on the requirements that the ideal resin solid acid catalyst should have strong acidity, large specific surface area, high porosity and good reaction diffusion, and realizes acid enhancement by sulfonating sulfur trioxide with porous resin to prepare the super strong solid acid resin with larger acid amount and solve the key problem of small surface acid amount of traditional sulfonated resin. In addition, the solid acid catalyst prepared by the method has the characteristics of porosity, large pore volume and high specific surface area, and is applied to the catalytic reaction of cyclohexene and acetic acid esterification to synthesize cyclohexyl acetate, which significantly improves the catalytic activity and selectivity of the resin solid acid, has good diffusion performance and very important application value, and achieves good technical effect. DETAILED DESCRIPTION

[0019] The following specific examples are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the present examples without creative contribution after reading the present specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

[0020] The present application will be described in detail below in combination with examples. Example 1

[0021] First, the macroporous polystyrene sulfonic acid resin is refluxed and swelled at 80℃ by using 1,2-dichloroethane, and the swelled resin is filtered to remove excess solvent; then the macroporous polystyrene sulfonic acid resin is loaded in a tank reactor, and 10% SO3 gas diluted by nitrogen is introduced, and the reaction is carried out at 120℃ and 140℃ for 2 h under 1.0 Mpa pressure, and then the temperature is increased to 170℃, and the sulfonation is continued for 1 h, and after the reaction is completed, the sample is placed in an air environment at room temperature for 5-12 h; then the sample is stepwise acid washed, and the sample is washed with 80%, 50%, 30%, 10% and 5% concentrated sulfuric acid, and washed with deionized water several times, and dried at 100℃ overnight, and finally the porous solid acid catalyst is obtained, which is recorded as sample 1, and the sample crushing loss rate is 0.4% and the acid exchange capacity is 8.0 mmol g -1 The prepared sample 1 catalyst is placed in a tank reactor and used for the esterification reaction of cyclohexene and acetic acid, and the reaction is carried out at a stirring speed of 25 r / min, a catalyst dosage of 10%, a molar ratio of acetic acid to cyclohexene of 5:1, a reaction temperature of 100℃ and a self-formed reaction pressure for 5 h, and the conversion rate of cyclohexene is 60.8% and the selectivity of cyclohexyl acetate is 95.1%. Example 2

[0022] The sample of the present application is prepared in the same way as in Example 1, except that the porous resin used for preparing the porous solid acid catalyst is nafion perfluorinated resin, which is recorded as sample 2, the sample crushing loss rate is 0.5%, and the acid exchange capacity is 5.1 mmol / g -1 .

[0023] The prepared sample 2 catalyst is placed in a fixed bed reactor for the esterification reaction of cyclohexene and acetic acid, under the conditions of acetic acid: cyclohexene (molar ratio) = 5:1, space velocity 0.5 h -1 , reaction temperature 120℃, and the cyclohexene conversion rate can reach 70.8%, and the selectivity of cyclohexyl acetate is 90.2%. Example 3

[0024] The sample of the present application is prepared in the same way as in Example 1, except that the porous resin used for preparing the porous solid acid catalyst is polytrifluorostyrene resin, which is recorded as sample 3, the sample crushing loss rate is 1%, and the acid exchange capacity is 8.2 mmol / g -1 .

[0025] The prepared sample 3 catalyst is placed in a tank reactor for the esterification reaction of cyclohexene and acetic acid, under the conditions of stirring speed 25 r / min, catalyst dosage 10%, acetic acid: cyclohexene (molar ratio) = 4:1, reaction temperature 110℃, and the cyclohexene conversion rate can reach 90.8%, and the selectivity of cyclohexyl acetate is 92.1%. Example 4

[0026] The sample of the present application is prepared in the same way as in Example 1, except that the porous resin used for preparing the porous solid acid catalyst is polytrifluorostyrene sulfonated resin, which is recorded as sample 2, the sample crushing loss rate is 2.5%, and the acid exchange capacity is 8.5 mmol / g -1 .

[0027] The prepared sample 1 catalyst is placed in a tank reactor for the esterification reaction of cyclohexene and acetic acid, under the conditions of stirring speed 25 r / min, catalyst dosage 10%, acetic acid: cyclohexene (molar ratio) = 5:1, reaction temperature 120℃, and the cyclohexene conversion rate can reach 93.8%, and the selectivity of cyclohexyl acetate is 97.1%. Example 5

[0028] The sample of the present application is prepared in the same way as in Example 1, except that the organic solvent used for preparing the porous solid acid catalyst is 1,1-dichloroethane, which is recorded as sample 5, the sample crushing loss rate is 0.8%, and the acid exchange capacity is 7.0 mmol / g -1 .

[0029] The prepared sample 5 catalyst was used in the esterification reaction of cyclohexene and acetic acid under the same conditions as in Example 1, and the final conversion rate of cyclohexene was 88.7% and the selectivity of cyclohexyl acetate was 95.8%. Example 6

[0030] The sample of the present application was prepared in the same way as in Example 1, except that carbon tetrachloride was used as the organic solvent for preparing the porous solid acid catalyst, which is referred to as sample 6. The sample crushing loss rate was 1.1% and the acid exchange capacity was 6.8 mmol g -1 .

[0031] The prepared sample 6 catalyst was used in the esterification reaction of cyclohexene and acetic acid under the same conditions as in Example 2, and the final conversion rate of cyclohexene was 85.7% and the selectivity of cyclohexyl acetate was 97.4%. Example 7

[0032] The sample of the present application was prepared in the same way as in Example 1, except that the concentration of SO3 diluted with nitrogen for preparing the porous solid acid catalyst was 50%, which is referred to as sample 7. The sample crushing loss rate was 2%.

[0033] The prepared sample 7 catalyst was used in the esterification reaction of cyclohexene and acetic acid under the same conditions as in Example 1, and the final conversion rate of cyclohexene was 88.7% and the selectivity of cyclohexyl acetate was 95.8%. Example 8

[0034] The sample of the present application was prepared in the same way as in Example 1, except that the concentration of SO3 diluted with nitrogen for preparing the porous solid acid catalyst was 80%, which is referred to as sample 8. The sample crushing loss rate was 5% and the acid exchange capacity was 6.0 mmol g -1 .

[0035] The prepared sample 8 catalyst was used in the esterification reaction of cyclohexene and acetic acid under the same conditions as in Example 2, and the final conversion rate of cyclohexene was 83.7% and the selectivity of cyclohexyl acetate was 96.8%. Example 9

[0036] The sample of the present application was prepared in the same way as in Example 1, except that the pressure of the sulfonation reaction for preparing the porous solid acid catalyst was atmospheric pressure, which is referred to as sample 9. The sample crushing loss rate was 0.4% and the acid exchange capacity was 4.2 mmol g -1 .

[0037] The prepared sample 9 catalyst was used in the esterification reaction of cyclohexene and acetic acid under the same conditions as in Example 1, and the final conversion rate of cyclohexene was 80.7% and the selectivity of cyclohexyl acetate was 96.8%. Example 10

[0038] The sample of the present application was prepared in the same way as in Example 1, except that the sulfonation reaction for preparing the porous solid acid catalyst was carried out at a pressure of 2.0 MPa, and the sample was designated as sample 10. The sample 10 had a crushing loss of 4.7% and an acid exchange capacity of 8.4 mmol / g. -1 .

[0039] The prepared sample 10 was used as the catalyst in the esterification of cyclohexene with acetic acid under the same conditions as in Example 2. The conversion of cyclohexene was 86.7% and the selectivity of cyclohexyl acetate was 95.8%.

[0040] Comparative Example 1

[0041] The same procedure as in Example 1 was followed, except that the macroporous polystyrene sulfonic acid resin was not subjected to the sulfonation reaction with SO3. The esterification of cyclohexene with acetic acid was carried out under the same conditions as in Example 1. The conversion of cyclohexene was 60.8% and the selectivity of cyclohexyl acetate was 85.7%.

[0042] Comparative Example 2

[0043] The same procedure as in Example 2 was followed, except that the nafion perfluorinated resin was not subjected to the sulfonation reaction with SO3. The esterification of cyclohexene with acetic acid was carried out under the same conditions as in Example 2. The conversion of cyclohexene was 0.5% and the selectivity of cyclohexyl acetate was 80.1%.

[0044] Comparative Example 3

[0045] The same procedure as in Example 3 was followed, except that the polytrifluorostyrene resin was not subjected to the swelling by refluxing at 80°C in 1,2-dichloroethane. The esterification of cyclohexene with acetic acid was carried out under the same conditions as in Example 3. The conversion of cyclohexene was 60.5% and the selectivity of cyclohexyl acetate was 83.4%.

Claims

1. A method for preparing a porous solid acid catalyst, characterized in that, Includes the following steps: Step i: The porous resin is refluxed and swollen at 80°C using an organic solvent. The swollen porous resin is filtered to remove excess solvent. The porous resin is one of macroporous polystyrene sulfonate resin, Nafion perfluorosulfonate resin, and polytrifluorostyrene sulfonated resin. The organic solvent is one or more of 1,1-dichloroethane, 1,2-dichloroethane, tetrachloroethylene, carbon tetrachloride, and chloroform. Step ii: The porous resin is loaded into the reactor, SO3 gas diluted with nitrogen is introduced, and sulfonation is carried out at 120℃ and 140℃ for 2 h at a certain reaction pressure. Then the temperature is raised to 170℃ and sulfonation is continued for 1 h. After sulfonation, it is placed in a normal temperature air environment for 5-12 h. Step iii: The sulfonated sample is acid-washed in steps, and the sulfonated resin is washed successively with concentrated sulfuric acid of 80%, 50%, 30%, 10% and 5% by mass concentration. Finally, it is washed several times with deionized water and dried at 100°C overnight to obtain a porous solid acid catalyst.

2. The method for preparing a porous solid acid catalyst according to claim 1, characterized in that, The reactor in step ii is either a tubular reactor or a batch reactor.

3. The method for preparing a porous solid acid catalyst according to claim 1, characterized in that, The nitrogen-diluted SO3 gas in step ii has a molar ratio of SO3 to nitrogen of 1:1 to 1:

10.

4. The method for preparing a porous solid acid catalyst according to claim 1, characterized in that, The sulfonation reaction pressure in step ii is 0.1-2.0 MPa.