Solid acid catalyst for propylene oligomerization as well as preparation method and application of solid acid catalyst

Abstract

The invention relates to a solid acid catalyst for propylene oligomerization and a preparation method and application thereof, and belongs to the technical field of propylene oligomerization catalysis. In order to solve the problems of low reaction efficiency, low selectivity, uncontrollable reaction and easy inactivation of the catalyst in the process for preparing dodecene by oligomerization of propylene, the invention provides a solid acid catalyst which takes mesoporous silica as a carrier and loaded perfluorosulfonic acid as an active center, and the loading capacity of the perfluorosulfonic acid is 5-40wt%. The amount and activity of the acid are adjusted by adjusting the loading amount of the perfluorosulfonic acid, active sites are uniformly distributed, the operability is high, the catalyst shows good propylene conversion rate and dodecene selectivity under the mild conditions of 90 DEG C and 2.0 MPa, the thermal stability is excellent, the catalyst still has good selectivity and conversion rate after being repeatedly used for four times, and the catalyst shows excellent stability. The solid acid catalyst provided by the invention can be regenerated through nitric acid protonation, the problem that the solid acid catalyst is easy to inactivate is solved, and the solid acid catalyst is green and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of propylene oligomerization catalysis, and particularly relates to a solid acid catalyst for propylene oligomerization, a preparation method thereof, and an application thereof. Background Art

[0002] Propylene oligomerization refers to the process in which propylene molecules (C 3 H 6 ) form higher molecular weight hydrocarbon compounds through oligomerization under the action of a catalyst. The dimers, trimers, tetramers, etc. formed by propylene oligomerization. Dodecene (C 12 H 24 ) is a tetramer formed by the oligomerization of four propylene molecules and has a wide range of applications in the chemical industry, such as for synthesizing various fine chemical products such as surfactants, detergents, and plasticizers.

[0003] The catalyst plays a decisive role in the propylene oligomerization reaction, and different catalysts may lead to different oligomer distributions and yields. At present, the commonly used catalysts for propylene oligomerization are homogeneous catalysts and heterogeneous catalysts, and the heterogeneous catalysts mainly include solid phosphoric acid catalysts and solid acid catalysts. Although solid phosphoric acid catalysts and solid acid catalysts can be used for the preparation of dodecene by propylene oligomerization, they still face various problems.

[0004] The number of active centers of the catalyst is limited, and the distribution and accessibility of acidic sites are limited, resulting in low catalytic reaction efficiency. The pore structure and surface properties of the catalyst have an important influence on the selectivity of the product. If the pores of the catalyst are too large or the surface acidity is too strong, it may lead to an increase in cracking products and a decrease in the selectivity of oligomers. The activity of the catalyst may fluctuate significantly due to small changes in reaction conditions, resulting in instability of the reaction rate and product distribution. The carbon deposition generated during the reaction may cover the active sites on the catalyst surface, resulting in catalyst deactivation. Based on this, there is an urgent need in the art to develop more suitable and efficient catalyst systems. Summary of the Invention

[0005] To solve the problems of low reaction efficiency, low selectivity, uncontrollable reaction, and easy deactivation of the catalyst in the process of preparing dodecene by propylene oligomerization, the present invention provides a solid acid catalyst for propylene oligomerization, a preparation method thereof, and an application thereof.

[0006] The technical solution of the present invention:

[0007] A solid acid catalyst for propylene oligomerization, using mesoporous silica as a carrier and loading perfluorosulfonic acid as an active center, and the loading amount of the perfluorosulfonic acid is 5-40 wt%.

[0008] A preparation method of a solid acid catalyst for propylene oligomerization, the steps are as follows:

[0009] Step 1: Preparation of mesoporous silica:

[0010] Tetraethoxysilane, hydrochloric acid and water are mixed and stirred at a certain temperature for hydrolysis to obtain a tetraethoxysilane hydrolyzate; a perfluorosulfonic acid resin is dissolved in an ethanol solution to obtain a perfluorosulfonic acid solution, the perfluorosulfonic acid solution is added dropwise to a sodium hydroxide solution, the tetraethoxysilane hydrolyzate is added after sufficient mixing to obtain a neutral solution, the neutral solution is allowed to stand to obtain a silica gel, the silica gel is washed with water, and is fully dried to obtain a powder, and the obtained powder is calcined to obtain mesoporous silica;

[0011] Step 2: Preparation of solid acid catalyst:

[0012] Perfluorosulfonic acid is added to an ethanol solution and stirred until the solution is clear to obtain solution A. The fully dried mesoporous silica is added to the solution A under stirring. After continuous stirring for a certain period of time, the system is placed in a water bath and stirred until the solvent is evaporated. The obtained white solid is dried and ground to obtain a solid acid catalyst.

[0013] Furthermore, in step 1, the volume ratio of tetraethoxysilane, hydrochloric acid and water is 70:12:100, the concentration of hydrochloric acid is 0.5 mol / L, the hydrolysis temperature is 30-50° C., the stirring speed during hydrolysis is 340 rpm, and the hydrolysis time is 2.5 h.

[0014] Furthermore, in step 1, the mass volume ratio of the perfluorosulfonic acid resin, ethanol solution, sodium hydroxide solution and tetraethoxysilane hydrolyzate is 3.5g:300mL:86mL:100mL, the volume ratio of ethanol and water in the ethanol solution is 3:7, the concentration of the sodium hydroxide solution is 0.1mol / L, and the dripping rate of the perfluorosulfonic acid solution to the sodium hydroxide solution is 3 drops / s.

[0015] Furthermore, the neutral solution in step 1 is allowed to stand for 24 hours, and the silica gel is fully dried by first drying it at 60° C. for 24 hours, taking out the sample, grinding it, and then drying it at 120° C. for 5 hours.

[0016] Furthermore, the calcination in step 1 is performed at 550° C. for 5 hours, the heating rate of the calcination is 3° C. / min, and the average particle size of the mesoporous silica is 15 to 20 nm.

[0017] Further, the mass ratio of the perfluorosulfonic acid to the mesoporous silica in Step 2 is 0.05 - 0.40:1, the volume ratio of ethanol to water in the ethanol solution is 3:7, the rotation speed of the stirring in Step 2 is 300 rpm, the continuous stirring time after the mesoporous silica is added to Solution A is 2 h, the temperature of the water bath is 60 °C, the drying is first carried out at 60 °C for 24 h, the sample is taken out and ground and then dried at 150 °C for 2 h.

[0018] Application of a solid acid catalyst for propylene oligomerization in the preparation of dodecene by propylene oligomerization.

[0019] Further, the propylene oligomerization reaction is carried out in a fixed-bed reactor, the raw material is high-pressure liquid propylene, the solid acid catalyst provided by the present invention is filled in the constant temperature zone of the reaction tube of the fixed-bed reactor, the raw material is injected into the fixed-bed reactor, and reacts through the bed layer of the solid acid catalyst to generate dodecene.

[0020] Further, the reaction conditions are: the temperature is 30 - 120 °C, the pressure is 0.2 - 2 MPa, and the liquid hourly space velocity is 0.5 - 2 h -1 。

[0021] Advantages of the present invention:

[0022] In the present invention, perfluorosulfonic acid is loaded on silica as a catalyst for propylene oligomerization reaction. By adjusting the loading amount of perfluorosulfonic acid, the amount and activity of the acid are regulated. The active sites are evenly distributed and highly accessible. Under mild conditions of 90 °C and 2.0 MPa, it shows good propylene conversion rate and dodecene selectivity, and has excellent thermal stability. The solid acid catalyst loaded with perfluorosulfonic acid of the present invention still has good selectivity and conversion rate after being reused four times, showing excellent stability. The solid acid catalyst provided by the present invention can be regenerated by protonation with nitric acid, solving the problem that the catalyst in the solid acid catalytic process is easy to deactivate, and is green and environmentally friendly. Description of the drawings

[0023] Figures 1 - 4 SEM spectra of 18 wt% perfluorosulfonic acid loaded silica solid acid catalyst prepared in Example 4 at different magnification;

[0024] Figure 5 Infrared spectrum of 18 wt% perfluorosulfonic acid loaded silica solid acid catalyst prepared in Example 4;

[0025] Figure 6 X-ray diffraction pattern of 18 wt% perfluorosulfonic acid loaded silica solid acid catalyst prepared in Example 4;

[0026] Figure 7The X-ray diffraction pattern of the 33 wt % perfluorosulfonic acid supported silica solid acid catalyst prepared in Example 7;

[0027] Figure 8 Thermogravimetric spectrum of 33 wt% perfluorosulfonic acid supported silica solid acid catalyst prepared in Example 7;

[0028] Figure 9 This is the DSC spectrum of the 33 wt % perfluorosulfonic acid supported silica solid acid catalyst prepared in Example 7. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below in conjunction with the embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0030] Example 1

[0031] This embodiment provides a method for preparing a 5 wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0032] Step 1: Preparation of mesoporous silica:

[0033] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0034] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0035] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0036] Step 2: Preparation of solid acid catalyst:

[0037] 0.05 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then dried at 150° C. for 2 h to obtain a 5 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0038] Example 2

[0039] This embodiment provides a method for preparing a 10 wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0040] Step 1: Preparation of mesoporous silica:

[0041] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0042] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0043] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0044] Step 2: Preparation of solid acid catalyst:

[0045] 0.10 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then dried at 150° C. for 2 h to obtain a 10 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0046] Example 3

[0047] This embodiment provides a method for preparing a 15wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0048] Step 1: Preparation of mesoporous silica:

[0049] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0050] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0051] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0052] Step 2: Preparation of solid acid catalyst:

[0053] 0.15 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and the stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then it was placed at 150° C. and dried for 2 h to obtain a 15 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0054] Example 4

[0055] This embodiment provides a method for preparing a 18 wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0056] Step 1: Preparation of mesoporous silica:

[0057] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0058] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0059] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0060] Step 2: Preparation of solid acid catalyst:

[0061] 0.18 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then dried at 150° C. for 2 h to obtain an 18 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0062] Example 5

[0063] This embodiment provides a method for preparing a 20wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0064] Step 1: Preparation of mesoporous silica:

[0065] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0066] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0067] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0068] Step 2: Preparation of solid acid catalyst:

[0069] 0.20 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then dried at 150° C. for 2 h to obtain a 20 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0070] Example 6

[0071] This embodiment provides a method for preparing a 25wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0072] Step 1: Preparation of mesoporous silica:

[0073] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0074] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0075] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0076] Step 2: Preparation of solid acid catalyst:

[0077] 0.25 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then dried at 150° C. for 2 h to obtain a 25 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0078] Example 7

[0079] This embodiment provides a method for preparing a 33 wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0080] Step 1: Preparation of mesoporous silica:

[0081] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0082] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0083] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0084] Step 2: Preparation of solid acid catalyst:

[0085] 0.33 g of perfluorosulfonic acid was added to an ethanol solution, in which the volume ratio of ethanol to water was 3:7. The solution was magnetically stirred at 300 rpm until the solution became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and stirring was continued at room temperature for 2 h. The system was placed in a 60° C. water bath and stirred at 300 rpm until the solvent was evaporated. The obtained white solid was dried in a vacuum drying oven at 60° C. for 24 h, the sample was taken out and ground, and then dried at 150° C. for 2 h to obtain a 33 wt% perfluorosulfonic acid-loaded silica solid acid catalyst.

[0086] Example 8

[0087] This embodiment provides a method for preparing a 40wt% perfluorosulfonic acid-supported silica solid acid catalyst, the steps of which are as follows:

[0088] Step 1: Preparation of mesoporous silica:

[0089] Take 70 mL of tetraethoxysilane and add it into a three-necked flask, add 12 mL of 0.5 mol / L hydrochloric acid and 100 mL of water, and hydrolyze it under the conditions of magnetic stirring at a speed of 340 rpm and 50°C. Hydrolyze for 2.5 hours to obtain a clear and transparent tetraethoxysilane hydrolyzate.

[0090] 3.5 g of perfluorosulfonic acid resin was dissolved in 300 mL of ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution was 3:7. The obtained perfluorosulfonic acid solution was added dropwise to a beaker containing 86 mL of 0.1 mol / L sodium hydroxide solution at a dropping rate of 3 drops / s. After thorough mixing, 100 mL of tetraethoxysilane hydrolyzate was quickly added, and the pH of the obtained mixed system was adjusted to neutral to obtain a neutral solution.

[0091] The neutral solution was allowed to stand for 24 hours to obtain silica gel, which was washed with water and then dried at 60°C for 24 hours. The sample was taken out and ground, and then dried at 120°C for 5 hours to obtain powder. The powder was placed in a muffle furnace and heated at a heating rate of 3°C / min. After calcination at 550°C for 5 hours, white powdery mesoporous silica was obtained. The mesoporous silica was placed at 150°C for 1 hour and dried by forced air for use.

[0092] Step 2: Preparation of solid acid catalyst:

[0093] 0.40 g of perfluorosulfonic acid was added to an ethanol solution with a volume ratio of ethanol to water of 3:7. The solution was magnetically stirred at 300 rpm until it became clear to obtain solution A. 1.0 g of fully dried mesoporous silica was added to solution A under stirring at 300 rpm, and the mixture was continuously stirred at room temperature for 2 h. Then, the system was placed in a water bath at 60 °C and stirred at 300 rpm until the solvent was evaporated. The resulting white solid was dried in a vacuum drying oven at 60 °C for 24 h. The sample was taken out, ground, and then dried at 150 °C for 2 h to obtain a 40 wt% perfluorosulfonic acid-supported silica solid acid catalyst.

[0094] The performance of the solid acid catalysts prepared in Examples 1 - 8 was evaluated, and the evaluation results are as follows:

[0095] I. Figures 1 - 4 SEM spectra of the 18 wt% perfluorosulfonic acid-supported silica solid acid catalyst prepared in Example 4 at different magnifications; since the solid acid catalyst loaded with perfluorosulfonic acid is not conductive, gold spraying is required during testing. The instrument model is ZEISS GeminiSEM 300 from Germany. From Figures 1 - 4 it can be seen that the sample of the solid acid catalyst loaded with perfluorosulfonic acid is composed of silica particles with an average particle size of about 15 - 20 nm stacked together. This result is consistent with the XRD result that the catalyst has an amorphous crystal phase structure, and the porous property of the catalyst is mainly an amorphous mesoporous structure. A series of pores and pore structures formed by the stacking of silica particles provide rich attachment sites for the immobilization of perfluorosulfonic acid, ensuring the high dispersion of perfluorosulfonic acid on the support and enabling the excellent acid catalytic performance of perfluorosulfonic acid to be fully maintained in the solid acid catalyst loaded with perfluorosulfonic acid.

[0096] II. Figure 5 Infrared spectrum of the 18 wt% perfluorosulfonic acid-supported silica solid acid catalyst prepared in Example 4; from Figure 5 it can be seen that the peaks at 1096.3 cm -1 , 970.0 cm -1 , 804.2.3 cm -1 and 635.4.9 cm -1 are attributed to the Si-O-Si ring, Si-OH, and asymmetric stretching vibrations of Si-O-Si, respectively.

[0097] III. Figure 6 X-ray diffraction pattern of the 18 wt% perfluorosulfonic acid-supported silica solid acid catalyst prepared in Example 4, Figure 7 and X-ray diffraction pattern of the 33 wt% perfluorosulfonic acid-supported silica solid acid catalyst prepared in Example 7; from Figure 6 and Figure 7It can be seen that the broad peak generated by silica in the catalyst at 23° is broader than that of the silica support, and as the loading amount of perfluorosulfonic acid in the supported catalyst increases, the position of this peak also slightly shifts towards a lower diffraction angle (22.3°). This indicates that when perfluorosulfonic acid is loaded onto silica, perfluorosulfonic acid enters the pore structure of silica. As the loading amount of perfluorosulfonic acid increases, the shoulder peak at 16° of the catalyst becomes more obvious, indicating that as the loading amount of perfluorosulfonic acid increases from 18% to 33%, the loading amount of perfluorosulfonic acid on the surface of the silica support also increases, and thus it is more easily detected. The test results show that perfluorosulfonic acid forms a composite perfluorosulfonic acid@silica solid acid catalyst by entering the pore structure of the mesoporous silica support and combining with the adsorption on the surface of the support.

[0098] IV. Figure 8 is the thermogravimetric spectrum of the solid acid catalyst with 33 wt% perfluorosulfonic acid loaded on silica prepared in Example 7; from Figure 8 It can be seen that in the solid acid catalyst loaded with perfluorosulfonic acid, as the loading amount of perfluorosulfonic acid increases, the loading efficiency of perfluorosulfonic acid decreases. Through in-depth analysis of the first derivative of the weight loss curve, it can be known that the total weight loss of the catalyst is 33.9%. The mass decrease of the catalyst between 40°C and 120°C is approximately 1%, which is mainly caused by the volatilization of water in the catalyst, and is basically consistent with the actual 33% perfluorosulfonic acid loaded on silica. The mass decrease between 280 - 360°C is caused by the decomposition of the sulfonic acid groups of perfluorosulfonic acid in the catalyst at high temperature, and the mass decrease between 450 - 550°C is due to the decomposition of the carbon skeleton of perfluorosulfonic acid at high temperature.

[0099] V. Figure 9 is the DSC spectrum of the 33 wt% perfluorosulfonic acid loaded on silica solid acid catalyst prepared in Example 7, from Figure 9 It can be seen that the solid acid catalyst loaded with perfluorosulfonic acid has good thermal stability below 280°C. When the working temperature is higher than 280°C, the perfluorosulfonic acid in the solid acid catalyst loaded with perfluorosulfonic acid will decompose, resulting in the inactivation of the catalyst.

[0100] VI. The solid acid catalysts prepared in Examples 1 - 8 were respectively used for the oligomerization of propylene to dodecene.

[0101] The propylene oligomerization reaction was carried out in a fixed-bed reactor. The raw material was high-pressure liquid propylene. The solid acid catalysts prepared in Examples 1 - 8 were loaded into the isothermal zone of the reaction tube of the fixed-bed reactor in batches. The raw material was injected into the fixed-bed reactor and reacted through the solid acid catalyst bed layer. The reaction conditions were: temperature 90°C, pressure 2.0 MPa, liquid hourly space velocity 0.5 - 2 h -1 .

[0102] (1) After the propylene oligomerization reaction is completed, the product is subjected to gas-liquid separation, and the tail gas is introduced into a chromatograph for detection. The propylene conversion rate and the selectivity of dodecene are calculated. The results are shown in Table 1.

[0103] Table 1

[0104] Loading amount (wt%) Propylene conversion rate (%) 1 - dodecene selectivity (%) 1 - dodecene yield (%) 5 (Example 1) 66 41 27.1 10 (Example 2) 79 43 34.0 15 (Example 3) 87 49 42.6 18 (Example 4) 88 52.4 46.1 20 (Example 5) 88 50.6 44.5 25 (Example 6) 88 44 38.7 33 (Example 7) 88 39 34.3 40 (Example 8) 91 16 14.6

[0105] (2) The 18 wt% perfluorosulfonic acid-supported silica solid acid catalyst obtained in Example 4 is continuously used for the preparation of dodecene by propylene oligomerization. The reaction results are shown in Table 2.

[0106] Table 2

[0107] Number of times the catalyst is used Propylene conversion rate (%) Tetrapropylene selectivity (%) Tetrapropylene yield (%) 1 88 52.4 46.1 2 88 52.3 46.0 3 87 51.2 44.5 4 87 49.0 42.6 5 66 16.7 11.0

[0108] It can be seen from the data in Table 2 that the 18 wt% perfluorosulfonic acid-supported silica solid acid catalyst prepared in Example 4 exhibits stable catalytic performance after being recycled four times continuously.

Claims

1. A solid acid catalyst for propylene oligomerization, characterized in that: Mesoporous silica is used as a carrier, and perfluorosulfonic acid is loaded as an active center, wherein the loading amount of the perfluorosulfonic acid is 5 to 40 wt%.

2. A method for preparing a solid acid catalyst for propylene oligomerization as claimed in claim 1, characterized in that: Here are the steps: Step 1: Preparation of mesoporous silica: Tetraethoxysilane, hydrochloric acid and water are mixed and stirred at a certain temperature to be hydrolyzed to obtain a tetraethoxysilane hydrolyzate; a perfluorosulfonic acid resin is dissolved in an ethanol solution to obtain a perfluorosulfonic acid solution, the perfluorosulfonic acid solution is added dropwise to a sodium hydroxide solution, the tetraethoxysilane hydrolyzate is added after being fully mixed to obtain a neutral solution, the neutral solution is allowed to stand to obtain a silica gel, the silica gel is washed with water, and fully dried to obtain a powder, and the obtained powder is calcined to obtain mesoporous silica; Step 2: Preparation of solid acid catalyst: Perfluorosulfonic acid is added to an ethanol solution and stirred until the solution is clear to obtain solution A. The fully dried mesoporous silica is added to the solution A under stirring. After continuous stirring for a certain period of time, the system is placed in a water bath and stirred until the solvent is evaporated. The obtained white solid is dried and ground to obtain a solid acid catalyst.

3. The method for preparing a solid acid catalyst for propylene oligomerization according to claim 2, wherein: In step 1, the volume ratio of tetraethoxysilane, hydrochloric acid and water is 70:12:100, the concentration of hydrochloric acid is 0.5 mol / L, the hydrolysis temperature is 30-50° C., the stirring speed during hydrolysis is 340 rpm, and the hydrolysis time is 2.5 h.

4. The method for preparing a solid acid catalyst for propylene oligomerization according to claim 2 or 3, characterized in that: In step 1, the mass volume ratio of the perfluorosulfonic acid resin, ethanol solution, sodium hydroxide solution and tetraethoxysilane hydrolyzate is 3.5g:300mL:86mL:100mL, the volume ratio of ethanol to water in the ethanol solution is 3:7, the concentration of the sodium hydroxide solution is 0.1mol / L, and the dripping rate of the perfluorosulfonic acid solution to the sodium hydroxide solution is 3 drops / s.

5. The method for preparing a solid acid catalyst for propylene oligomerization according to claim 4, characterized in that: The neutral solution in step 1 is allowed to stand for 24 hours. The silica gel is fully dried by first drying it at 60° C. for 24 hours, then taking out the sample, grinding it, and then drying it at 120° C. for 5 hours.

6. The method for preparing a solid acid catalyst for propylene oligomerization according to claim 5, characterized in that: The calcination in step 1 is performed at 550° C. for 5 hours, the heating rate of the calcination is 3° C. / min, and the average particle size of the mesoporous silica is 15 to 20 nm.

7. The method for preparing a solid acid catalyst for propylene oligomerization according to claim 6, characterized in that: The mass ratio of the perfluorosulfonic acid to the mesoporous silica in step 2 is 0.05-0.40:1, the volume ratio of ethanol to water in the ethanol solution is 3:7, the stirring speed in step 2 is 300 rpm, the stirring time after the mesoporous silica is added to solution A is 2 hours, the temperature of the water bath is 60°C, and the drying is first carried out at 60°C for 24 hours, and the sample is taken out and ground and then dried at 150°C for 2 hours.

8. Use of the solid acid catalyst for propylene oligomerization as claimed in claim 1 in preparing dodecene by propylene oligomerization.

9. Use of the solid acid catalyst according to claim 8 in preparing dodecene by polymerization of propylene, characterized in that: The propylene polymerization reaction is carried out in a fixed bed reactor, the raw material is high-pressure liquid propylene, the solid acid catalyst as claimed in claim 1 is loaded in the constant temperature zone of the reaction tube of the fixed bed reactor, the raw material is injected into the fixed bed reactor, and reacts through the solid acid catalyst bed to generate dodecene.

10. Use of the solid acid catalyst according to claim 9 in preparing dodecene by propylene oligomerization, characterized in that: The reaction conditions are: temperature of 30-120°C, pressure of 0.2-2MPa, liquid hourly space velocity of 0.5-2h -1 .

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