Catalyst for synthesizing triethylene glycol di-2-ethylhexoate and preparation method thereof

Abstract

The invention discloses a solid superacid catalyst for synthesizing triethylene glycol di-2-ethylhexoate and a preparation method of the solid superacid catalyst. Aiming at the esterification reaction characteristics of 2-ethylhexanoic acid and triethylene glycol, SO4 < 2-> is loaded on a metal oxide carrier through an impregnation method, and the SO4 < 2-> / ZnO solid superacid catalyst is prepared. The preparation method comprises the following specific steps: fully impregnating a ZnO carrier with an ammonium sulfate solution, filtering, drying, and roasting to obtain a powder catalyst; the method comprises the following steps: uniformly mixing a powder catalyst with a binder, a pore forming agent, an extrusion aid and a peptizing agent, adding deionized water, fully kneading, extruding to obtain a formed wet material, and finally air-drying, drying and roasting to obtain the formed catalyst. The formed solid superacid catalyst prepared by the invention has a stable structure, is easy to separate and recover, is especially suitable for 2-ethylhexanoic acid which is a long-chain reactant with large steric hindrance, and improves the conversion per pass of esterification reaction.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of solid superacid catalysts, and particularly relates to the preparation of a shaped solid superacid catalyst for synthesizing triethylene glycol diisooctanoate and a preparation method thereof. Background Art

[0002] The chemical formula of triethylene glycol diisooctanoate is C 22 H 42 O6. It is a colorless, clear and transparent liquid at room temperature, soluble in common organic solvents such as acetone and ethanol, but insoluble in mineral oil and water. Triethylene glycol diisooctanoate has excellent properties such as good low-temperature resistance, durability, ultraviolet resistance, and antistatic properties, and is a very good solvent-based environmental protection plasticizer. In recent years, due to the rapid development of the plastics industry, especially the proposal of "replacing steel with plastic" and "replacing wood with plastic", the demand for plasticizers has increased rapidly. However, traditional phthalate plasticizers are harmful to the human body and are thus restricted from use in more and more countries. Therefore, triethylene glycol diisooctanoate, as a low-toxic environmental protection plasticizer, has received more and more attention and use.

[0003] Triethylene glycol diisooctanoate can be obtained by the esterification reaction of 2-ethylhexanoic acid and triethylene glycol. Traditional production processes mostly use batch reaction devices. First, an excessive amount of 2-ethylhexanoic acid and triethylene glycol are added to the reaction kettle, and then an acidic homogeneous catalyst and a co-catalyst are added, and the reaction is carried out at a certain temperature. After the reaction is completed, the materials in the kettle are cooled and the co-catalyst is roughly filtered. Then, an alkaline substance (such as NaOH solution, Na2CO3 solution, etc.) is added to neutralize the acidity of the materials, remove the excessive 2-ethylhexanoic acid and the traditional acidic homogeneous catalyst, and finally, the triethylene glycol diisooctanoate product is obtained through washing, rectification, and adsorption. The catalysts selected in the traditional production process of triethylene glycol diisooctanoate are mostly acidic homogeneous catalysts (such as sulfuric acid, phosphoric acid, etc.), which will corrode the equipment and are not easily removed after the reaction, and an alkali needs to be added for neutralization, increasing the production cost.

[0004] Different from homogeneous catalysts, heterogeneous catalysts are mostly solid, which are easy to be separated and recovered from the reaction solution, reducing the generation of industrial wastewater. Chinese Patent CN 106674007 A discloses a method for catalytic synthesis of triethylene glycol diisooctanoate using stannous chloride as a catalyst and titanium dioxide and activated carbon as co-catalysts. By adopting a negative pressure and low-temperature production process, the product is easy to be produced, and the generation of impurities in the esterification reaction is inhibited, improving the selectivity of the target product. Liu Yanjie et al. prepared acidified activated clay by impregnating activated clay with sulfuric acid. When used as a catalyst, under the conditions of a molar ratio of acid to alcohol of 4:1, a catalyst dosage of 8% of the total mass of acid and alcohol, and a water-carrying agent toluene dosage of 33% of the total mass of acid and alcohol, reacting for 5 h, the conversion rate of triethylene glycol can reach 93.45%, and the yield of triethylene glycol diisooctanoate can reach 77.01% (Journal of Chemical Industry, 2016, Issue 03). Fu Junhong et al. used a commercially available solid acid catalyst under the conditions of a molar ratio of 2-ethylhexanoic acid to triethylene glycol of 2.15, a catalyst dosage of 0.05% of the acid and alcohol dosage, a reaction temperature of 230 °C, and a reaction time of 5 h, and found that the conversion rate was relatively high and the product indexes were relatively good (Plastics Industry, 2011, Supplementary Issue). Chinese Patent CN 107778176 A reported a preparation method of a solid superacid catalyst SO4 2- / TiO2 / Ce. When the reaction temperature is 160 °C, the yield of triethylene glycol diisooctanoate can reach more than 80%. Ding Bingwei et al. prepared SO4 2- / ZrO2-γ-Al2O3 solid acid catalyst by precipitation-impregnation method to catalyze the esterification reaction of glycerol and 2-ethylhexanoic acid to synthesize triethylene glycol diisooctanoate (Industrial Catalysis, 2024, Issue 07). The above heterogeneous catalysts used for synthesizing triethylene glycol diisooctanoate are all in powder form, and it is difficult to recover the catalyst. Although zirconia solid superacid has good catalytic performance, its preparation cost is high.

[0005] Therefore, it is urgent to develop a heterogeneous catalyst that is easy to recover and has higher economic benefits. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the existing catalysts for synthesizing triethylene glycol diisooctanoate by the esterification method, and to provide a special shaped solid superacid catalyst for synthesizing triethylene glycol diisooctanoate and a preparation method thereof. This catalyst has the advantages of high catalytic activity, simple recovery, and high stability.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a special shaped solid superacid catalyst for the synthesis of triethylene glycol diisooctanoate. This method uses the impregnation method to prepare a solid superacid catalyst and extrude it into a shape; it includes the following steps: 1) Immerse the ZnO support in an ammonium sulfate solution. After immersion, filter by suction and place in a drying oven for drying. After drying, transfer to a crucible and place in a tube furnace for heat treatment in an air environment. After completion, naturally cool to room temperature to obtain powdered SO4 2- / ZnO solid superacid; 2) Add a binder, peptizing agent, extrusion aid, and pore-forming agent to the powdered SO4 2- / ZnO solid superacid catalyst obtained in step 1), mix evenly to obtain a powder, and add deionized water dropwise and knead thoroughly to obtain a wet bar material; 3) Place the wet bar material obtained in step 2) in an extruder for extrusion molding to obtain a strip-shaped wet body material. The extruded wet body strip material is air-dried at room temperature and then placed in an oven for drying. Then transfer to a crucible and place in a tube furnace for heat treatment in an air environment. After completion, naturally cool to room temperature to obtain a shaped SO4 2- / ZnO solid superacid catalyst.

[0008] Furthermore, the concentration of the ammonium sulfate aqueous solution in step 1) is 2.5 - 3.0 mol / L.

[0009] Furthermore, the mass ratio of the ZnO support to the ammonium sulfate aqueous solution in step 1) is 1:3 - 1:4.

[0010] Furthermore, the immersion time in step 1) is 10 - 12 h.

[0011] Furthermore, the drying temperature in steps 1) and 3) is 90 - 120 °C, and the drying time is 3 - 5 h.

[0012] Furthermore, the heat treatment temperature in steps 1) and 3) is 450 - 500 °C, and the time is 2 - 5 h.

[0013] Furthermore, the mass ratio of deionized water to the powder in step 2) is 0.60 - 0.65.

[0014] Furthermore, the pore-forming agent in step 2) is activated carbon, and the addition amount is 0.4 - 0.6% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst.

[0015] Furthermore, the peptizing agent in step 2) is a nitric acid aqueous solution with a concentration of 1.8 - 2.2 mol / L, and the addition amount is 8 - 10% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst.

[0016] Furthermore, the extrusion aid in step 2) is methyl cellulose, and its addition amount is 0.8 - 1.2% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst.

[0017] Further, the binder described in step 2) is pseudo-boehmite, and its addition amount is 23-26% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst.

[0018] Further, the size of the strip-shaped wet body material described in step 3) has a diameter of 2.0-2.5 mm and a length of 1.5-2.0 mm.

[0019] Further, the time for air drying at room temperature described in step 3) is 10-12 h.

[0020] The formed SO4 2- / ZnO solid superacid catalyst obtained by the above preparation method has a mechanical strength of 80-100 N·cm -1 , and a specific surface area of 15-30 m 2 / g.

[0021] The essence of the esterification reaction of 2-ethylhexanoic acid and triethylene glycol is an acid-catalyzed dehydration condensation reaction. Since 2-ethylhexanoic acid is an α-branched carboxylic acid, it has a large steric hindrance and a high polarization difficulty of the carbonyl group, and a catalyst with extremely high acid strength is required to activate the carboxylic acid. In addition, the branched chain of 2-ethylhexanoic acid makes it difficult for its carboxyl group to approach the active site of the catalyst, and the triethylene glycol molecule has a long chain and contains three hydroxyl groups, which may lead to a decrease in reaction efficiency due to adsorption site competition. Therefore, a catalyst suitable for the esterification reaction of 2-ethylhexanoic acid and triethylene glycol should contain Bronsted acid (B acid) and Lewis acid (L acid). Among them, B acid can protonate the carbonyl oxygen of the carboxylic acid, enhancing the electrophilicity of the carbonyl carbon, while L acid coordinates with the carbonyl oxygen or hydroxyl oxygen through the unoccupied d orbital, further polarizing the chemical bond and reducing the reaction activation energy. The synergistic effect of B acid and L acid can significantly improve the catalytic activity of the catalyst. And SO4 2- / ZnO solid superacid can meet the above requirements through surface sulfation.

[0022] The present invention has the following beneficial effects: 1) In the formed SO4 2- / ZnO solid superacid catalyst, the unoccupied d orbital of Zn 2+ can accept electron pairs and coordinate with the lone pair electrons of the carbonyl oxygen of the carboxylic acid or the hydroxyl group of the alcohol, having an active site of L acid, while the SO4 2- modified on the catalyst surface can combine with ZnO to form an S-O-Zn structure, and some hydroxyl groups (-OH) can release protons (H + ), thus having an active site of B acid.

[0023] 2) The L acid (Zn 2- / ZnO solid superacid catalyst of the formed SO4 2+) Co-activate the reactants with B acid (H + ), reduce the activation energy of the esterification reaction of 2-ethylhexanoic acid and triethylene glycol, and greatly improve the activity of the catalyst.

[0024] 3) The structure of the shaped SO4 2- / ZnO solid superacid catalyst is stable and easy to separate and recycle, avoiding the problems of corrosion of conventional homogeneous acids (such as H2SO4) and difficult recovery of conventional solid superacid powders, and the catalyst has good repeatability.

[0025] 4) The highly dispersed acidic sites and mesoporous structure of the shaped SO4 2- / ZnO solid superacid catalyst enhance the substrate adsorption ability, especially suitable for reactants such as 2-ethylhexanoic acid with long chains and large steric hindrance, and improve the single-pass conversion rate of the esterification reaction. Description of the Drawings

[0026] Figure 1 FT-IR spectra of the powdered and shaped catalyst samples prepared in Example 1.

[0027] Figure 2 BET characterization diagrams of the powdered and shaped catalyst samples prepared in Example 1.

[0028] Figure 3 XRD diagrams of the powdered and shaped catalyst samples prepared in Example 1.

[0029] Figure 4 EDS spectra of the powdered and shaped catalyst samples prepared in Example 1.

[0030] Figure 5 Yield diagram of triethylene glycol diisooctoate of the shaped catalyst obtained in Example 3 and reused 5 times.

[0031] Figure 6 Mass change diagram of the powdered catalyst recovered after being reused 4 times.

[0032] Figure 7 Triethylene glycol conversion rate and triethylene glycol diisooctoate yield diagram of the powdered catalyst reused 4 times. Detailed Embodiments

[0033] In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto. Example 1 (1) 40 g of ZnO carrier was immersed in 160 g of 3.0 mol / L ammonium sulfate aqueous solution for 12 h and then filtered. The solid obtained by filtration was placed in a drying oven and dried at 120 °C for 3 h. After drying, it was transferred to a crucible and placed in a tube furnace for calcination at 500 °C for 5 h in an air environment. After calcination, it was taken out and cooled to room temperature to obtain powdered SO4 2- / ZnO solid superacid catalyst; (2) Add the powdered SO4 obtained in step (1) 2- / ZnO solid superacid catalyst is added with activated carbon as a pore-forming agent, and the amount added is powdered SO4 2- / 0.5% of the mass of ZnO solid superacid catalyst; 2.0 mol / L nitric acid aqueous solution as peptizer, the addition amount is powdered SO4 2- / 10% of the mass of ZnO solid superacid catalyst; methyl cellulose is used as an extrusion aid, and the addition amount is powdered SO4 2- / 1% of the mass of ZnO solid superacid catalyst; pseudo-boehmite is used as a binder, and its addition amount is powdered SO4 2- / 25% by mass of ZnO solid super acid catalyst, mix evenly to obtain powder, add deionized water in an amount of 65% by mass of the powder, and fully knead to obtain a wet strip material.

[0035] (3) The wet strip material is then extruded into strips with a size of φ2.2 mm × 2.0 mm. After air-drying at room temperature for 12 hours, it is placed in a drying oven and dried at 120°C for 3 hours. It is then transferred to a crucible and placed in a tubular furnace for calcination at 500°C for 4 hours in an air environment. After the calcination, it is naturally cooled to room temperature to obtain shaped SO4 2- / ZnO solid superacid catalyst, denoted as formed SO4 2- / ZnO solid superacid catalyst.

[0036] Under this condition, the mechanical strength of the prepared catalyst was measured by an intelligent particle strength tester and was 89.90 N·cm -1 The specific surface area of the formed catalyst was measured by BET characterization to be 16.44 m 2 ·g -1 The catalyst prepared under this condition was used in the reaction of esterifying triethylene glycol and 2-ethylhexanoic acid to synthesize triethylene glycol di(2-ethylhexanoate). The conditions were as follows: the reaction temperature was 220 °C, the molar ratio of acid to alcohol was 4:1, the fixed-bed reactor was filled with the shaped catalyst, the catalyst dosage was 2.5 wt.% (based on the mass of triethylene glycol added), the residence time of the material in the reactor was 30 min, and the fixed bed was operated for 300 h. After the reaction, the composition of the reaction solution was measured by gas chromatography, and the yield of triethylene glycol di(2-ethylhexanoate) formed by the esterification of triethylene glycol and 2-ethylhexanoic acid was calculated. The formula for calculating the yield was as follows: 。

[0037] Under these conditions, the conversion rate of triethylene glycol was 99.54%, and the yield of triethylene glycol di(2-ethylhexanoate) was 72.70%.

[0038] The prepared powder and shaped samples were characterized by Fourier transform infrared spectroscopy. From Figure 1 it can be seen that absorption peaks appeared near 1075 cm 2- , 1169 cm -1 , and 1215 cm -1 for both the powder and shaped SO4 -1 / ZnO solid superacid catalysts in the FT-IR spectrum. These are the characteristic absorption peaks of the SO4 2- / ZnO solid superacid, which proves the successful preparation of the catalyst.

[0039] The prepared powder and shaped samples were characterized by nitrogen physical adsorption-desorption. From Figure 2 it can be seen that the specific surface area of the shaped catalyst increased. The isotherms of both the powder and shaped catalysts were of type Ⅳ, and an H3-type hysteresis loop appeared at P / P0 = 0.5 - 1.0, indicating that the catalyst was a mesoporous material formed by the stacking of flaky particles with slit pores.

[0040] The prepared powder and shaped samples were analyzed by XRD. From Figure 3 it can be seen that the extrusion molding did not destroy the structure of the catalyst.

[0041] The prepared shaped sample was analyzed by EDS. From Figure 4 it can be seen that in Figure (c), the S element was clearly and evenly distributed in the material, proving the successful loading of SO4 2- .

[0042] Comparative Example 1 (1) 40 g of ZnO carrier was immersed in 160 g of 3.0 mol / L ammonium sulfate aqueous solution for 12 h and then filtered. The solid obtained by filtration was placed in a drying oven and dried at 120 °C for 3 h. After drying, it was transferred to a crucible and placed in a tube furnace for calcination at 500 °C for 5 h in an air environment. After calcination, it was taken out and cooled to room temperature to obtain powdered SO4 2- / ZnO solid superacid catalyst; (2) Add the powdered SO4 obtained in step (1) 2- / ZnO solid superacid catalyst is added with activated carbon as a pore-forming agent, and the amount added is powdered SO4 2- / 0.5% of the mass of ZnO solid superacid catalyst; 6.0 mol / L nitric acid aqueous solution as peptizer, the addition amount is powdered SO4 2- / 10% of the mass of ZnO solid superacid catalyst; methyl cellulose powder is used as an extrusion aid, and the addition amount is powdered SO4 2- / 1% of the mass of ZnO solid superacid catalyst; pseudo-boehmite is used as a binder, and its addition amount is powdered SO4 2- / 25% by mass of ZnO solid super acid catalyst, mix evenly to obtain powder, add deionized water in an amount of 65% by mass of the powder, and fully knead to obtain a wet strip material.

[0043] (3) The wet strip material is then extruded into strips with a size of φ2.2 mm × 2.0 mm. After air-drying at room temperature for 24 hours, it is placed in a drying oven at 120°C for 3 hours, then transferred to a crucible, placed in a tubular furnace and calcined at 500°C for 4 hours in an air environment. After the calcination, it is naturally cooled to room temperature to obtain shaped SO4 2- / ZnO solid superacid catalyst, denoted as formed SO4 prepared from 6.0 mol / L nitric acid aqueous solution 2- / ZnO solid superacid catalyst.

[0044] Under this condition, the mechanical strength of the prepared shaped catalyst is 22.57 N·cm -1 The specific surface area of the catalyst was measured by BET characterization to be 15.38 m 2 ·g -1 .

[0045] The catalyst prepared under this condition was used in the reaction of triethylene glycol and 2-ethylhexanoate to synthesize triethylene glycol diisooctanoate, and the conditions were: reaction temperature 220°C, acid-alcohol molar ratio 4:1, fixed bed reactor filled with molded catalyst, catalyst dosage 2.5wt.% (accounting for the mass of added triethylene glycol), material residence time in the reactor 30min, fixed bed operation 300h. Under this condition, the conversion rate of triethylene glycol was 98.01%, and the yield of triethylene glycol diisooctanoate was 65.47%.

[0046] Compared with Example 1, the nitric acid concentration in Comparative Example 1 is too high, resulting in the formed sol being too viscous, which may generate greater internal stress during the roasting process, forming more cracks, and the mechanical strength does not meet the requirements.

[0047] Comparative Example 2 (1) 40 g of ZnO carrier was immersed in 160 g of 3.0 mol / L ammonium sulfate aqueous solution for 12 h and then filtered. The solid obtained by filtration was placed in a drying oven and dried at 120 °C for 3 h. After drying, it was transferred to a crucible and placed in a tube furnace for calcination at 500 °C for 5 h in an air environment. After calcination, it was taken out and cooled to room temperature to obtain powdered SO4 2- / ZnO solid superacid catalyst; (2) Add the powdered SO4 obtained in step (1) 2- / ZnO solid superacid catalyst is added with activated carbon as a pore-forming agent, and the amount added is powdered SO4 2- / 0.5% of the mass of ZnO solid superacid catalyst; 2.0 mol / L nitric acid aqueous solution as peptizer, the addition amount is powdered SO4 2- / 10% of the mass of ZnO solid superacid catalyst; methyl cellulose powder is used as an extrusion aid, and the addition amount is powdered SO4 2- / 3% of the mass of ZnO solid superacid catalyst; pseudo-boehmite is used as a binder, and its addition amount is powdered SO4 2- / 25% by mass of ZnO solid super acid catalyst, mix evenly to obtain powder, add deionized water in an amount of 65% by mass of the powder, and fully knead to obtain a wet strip material.

[0048] (3) The wet strip material is then extruded into strips with a size of φ2.2 mm × 2.0 mm. After air-drying at room temperature for 24 hours, it is placed in a drying oven at 120°C for 3 hours, then transferred to a crucible, placed in a tubular furnace and calcined at 500°C for 4 hours in an air environment. After the calcination, it is naturally cooled to room temperature to obtain shaped SO4 2- / ZnO solid superacid catalyst, denoted as shaped SO4 prepared with 3% methyl cellulose powder 2- / ZnO solid superacid catalyst. Its mechanical strength was measured by an intelligent particle strength tester to be 48.86N·cm -1 The specific surface area of the catalyst was measured by BET characterization to be 15.05 m 2 ·g -1 .

[0049] The catalyst prepared under this condition was used in the reaction of triethylene glycol and 2-ethylhexanoate to synthesize triethylene glycol diisooctanoate, and the conditions were: reaction temperature 220°C, acid-alcohol molar ratio 4:1, fixed bed reactor filled with molded catalyst, catalyst dosage 2.5wt.% (accounting for the mass of added triethylene glycol), material residence time in the reactor 30min, fixed bed operation 300h. Under this condition, the conversion rate of triethylene glycol was 99.01%, and the yield of triethylene glycol diisooctanoate was 70.47%.

[0050] Compared with Example 1, the content of methyl cellulose added in Comparative Example 2 is increased, the yield of triethylene glycol diisooctanoate is not improved, and the mechanical strength of the catalyst is significantly reduced, which does not meet the process requirements. It is easy to break during the reaction and is not easy to recover the catalyst.

[0051] Comparative Example 3 (1) 40 g of ZnO carrier was immersed in 160 g of 3.0 mol / L ammonium sulfate aqueous solution for 12 h and then filtered. The solid obtained by filtration was placed in a drying oven and dried at 120 °C for 3 h. After drying, it was transferred to a crucible and placed in a tube furnace for calcination at 500 °C for 5 h in an air environment. After calcination, it was taken out and cooled to room temperature to obtain powdered SO4 2- / ZnO solid superacid catalyst; (2) to the powdered SO4 obtained in step (1) 2- / ZnO solid superacid catalyst is added with activated carbon as a pore-forming agent, and the amount added is powdered SO4 2- / 0.5% of the mass of ZnO solid superacid catalyst; 2.0 mol / L nitric acid aqueous solution as peptizer, the addition amount is powdered SO4 2- / 10% of the mass of ZnO solid superacid catalyst; methyl cellulose powder is used as an extrusion aid, and the addition amount is powdered SO4 2- / 1% of the mass of ZnO solid superacid catalyst; pseudo-boehmite is used as a binder, and its addition amount is powdered SO4 2- / 30% by mass of ZnO solid super acid catalyst, after uniform mixing to obtain powder, the mass of deionized water added dropwise is 65% by mass of the powder, and the mixture is fully kneaded to obtain a wet strip material.

[0052] The wet strip material is then extruded through an extruder to form strips with dimensions of φ2.2mm×2.0mm. After air-drying at room temperature for 24h, it is placed in a drying oven and dried at 120°C for 3h. Then it is transferred to a crucible and placed in a tubular furnace for calcination at 500°C for 4h in an air environment. After that, it is naturally cooled to room temperature to obtain the formed SO4 2- / ZnO solid superacid catalyst, denoted as the formed SO4 2- / ZnO solid superacid catalyst prepared from 30% pseudoboehmite. Its mechanical strength is measured to be 90.20N·cm -1 by an intelligent particle strength tester, and the specific surface area of the catalyst is measured to be 38.00m 2 ·g -1 .

[0053] The catalyst prepared under this condition is used in the reaction of esterification synthesis of triethylene glycol di(2-ethylhexanoate) from triethylene glycol and 2-ethylhexanoic acid. The conditions are as follows: reaction temperature 220°C, molar ratio of acid to alcohol 4:1, the fixed-bed reactor is filled with the formed catalyst, the catalyst dosage is 2.5wt.% (based on the mass of the added triethylene glycol), the residence time of the material in the reactor is 30min, and the fixed bed operates for 300h. Under these conditions, the conversion rate of triethylene glycol is 96.17%, and the yield of triethylene glycol di(2-ethylhexanoate) is 55.95%.

[0054] Comparing with Example 1, in Comparative Example 3, the addition amount of pseudoboehmite increases, and the mechanical strength of the catalyst does not change. However, due to the excessive content of pseudoboehmite, more active sites of the catalyst are covered, resulting in a significant decrease in the yield of triethylene glycol di(2-ethylhexanoate).

[0055] Comparative Example 4 (1) 40g of ZnO support is placed in 160g of ammonium sulfate aqueous solution with a concentration of 3.0mol / L and impregnated for 12h, then filtered by suction. The obtained solid is placed in a drying oven and dried at 120°C for 3h. After drying, it is transferred to a crucible and placed in a tubular furnace for calcination at 500°C for 5h in an air environment. After calcination, it is taken out and cooled to room temperature to obtain the powdered SO4 2- / ZnO solid superacid catalyst; (2) Activated carbon is added as a pore-forming agent to the powdered SO4 2- / ZnO solid superacid catalyst obtained in step (1), and its addition amount is 0.5% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst; 2.0mol / L nitric acid aqueous solution is used as a peptizing agent, and its addition amount is 10% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst; methyl cellulose powder is used as an extrusion aid, and its addition amount is the powdered SO4 2- / 1% of the mass of ZnO solid superacid catalyst; pseudo-boehmite is used as a binder, and its addition amount is powdered SO4 2- / 25% by mass of ZnO solid super acid catalyst, mix evenly to obtain powder, add deionized water in an amount of 65% by mass of the powder, and fully knead to obtain a wet strip material.

[0056] The wet strip material is then extruded into strips through an extruder. The size of the strip is φ3.5mm×2.0mm. After air-drying at room temperature for 24 hours, it is placed in a drying oven at 120℃ for 3 hours. It is then transferred to a crucible and placed in a tube furnace for calcination at 500℃ for 4 hours in an air environment. After the calcination, it is naturally cooled to room temperature to obtain shaped SO4 2- / ZnO solid superacid catalyst, recorded as the preparation of shaped SO4 with a diameter of 3.5 mm 2- / ZnO solid superacid catalyst. Its mechanical strength was measured by an intelligent particle strength tester to be 104.11N·cm -1 The specific surface area of the catalyst was measured by BET characterization to be 25.22 m 2 / g.

[0057] The catalyst prepared under this condition was used in the reaction of triethylene glycol and 2-ethylhexanoate to synthesize triethylene glycol diisooctanoate, and the conditions were: reaction temperature 220°C, acid-alcohol molar ratio 4:1, catalyst loaded in fixed bed, catalyst dosage 2.5wt.% (accounting for the mass of added triethylene glycol), reaction 4h, material residence time 30min, fixed bed operation 300h. Under this condition, the conversion rate of triethylene glycol was 98.48%, and the yield of triethylene glycol diisooctanoate was 50.03%.

[0058] Compared with Example 1, the catalyst diameter of Comparative Example 4 is 3.5 mm, and the mechanical changes of the molded catalyst are not significant, but the yield of triethylene glycol diisooctanoate is significantly reduced.

[0059] Example 2 Repeatability and stability of molded catalyst Prepare a batch of shaped SO4 with 25% pseudo-boehmite content according to the conditions of Example 1 2- / ZnO solid superacid catalyst. The reaction temperature was 220°C, the acid-alcohol molar ratio was 4:1, the catalyst was loaded in the fixed bed, the catalyst dosage was 2.5wt.% (accounting for the mass of triethylene glycol added), the material residence time was 30min, and the fixed bed was operated for 300h. After each fixed bed operation, the catalyst particles were repeatedly rinsed with ethanol, and then placed in a 120°C drying oven for drying. The dried catalyst was reloaded into the fixed bed reactor and operated for 300h, and reused 5 times. The yield of triethylene glycol diisooctanoate in each experiment was calculated according to the above method.

[0060] The experimental results are as followsFigure 5 As shown, it can be Figure 5 seen that the shaped catalyst still has good catalytic effect after being used five times, which indicates that the prepared shaped SO4 2- / ZnO solid superacid catalyst of the present invention has good recyclability and cycle stability.

[0061] Repeatability experiment and stability of the powder catalyst in Comparative Example 5 A batch of powder-type SO4 2- / ZnO solid superacid catalyst was prepared according to the conditions of Step 1 in Example 1. The reaction was carried out for 4 h under the conditions of reaction temperature 220 °C, molar ratio of acid to alcohol 4:1, and catalyst dosage 2.5 wt.% (accounting for the mass of added triethylene glycol). After each reaction, the catalyst obtained by filtering the reaction solution was repeatedly rinsed with ethanol, then placed in a drying oven at 120 °C for drying, weighed after drying, and reused under the above experimental conditions. The conversion rate of triethylene glycol and the yield of triethylene glycol diisooctanoate were calculated for each experiment according to the foregoing method.

[0062] The mass of the catalyst recovered each time is as Figure 6 shown. It can be found that there is a large loss in the mass of the recovered catalyst after each reaction. After the third recovery, the mass loss rate of the catalyst is as high as 86.67%; as Figure 7 shown, both the conversion rate of triethylene glycol and the yield of triethylene glycol diisooctanoate have decreased significantly. This indicates that there is a large mass loss of the powder catalyst during the reaction and recovery processes. Compared with Example 1, the powder catalyst has serious mass loss and is not suitable for the process system.

[0063] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A preparation method of a catalyst for synthesizing triethylene glycol diisooctanoate, characterized in that: It includes the following steps: 1) Immerse the ZnO support in an aqueous solution of ammonium sulfate. After impregnation, filter by suction, dry, and transfer to a crucible. Place it in a tube furnace and conduct heat treatment in an air environment. After completion, naturally cool to room temperature to obtain the powdered SO4 2- / ZnO solid superacid catalyst; 2) Add the powdered SO4 obtained in step 1) 2- Add a binder, a peptizing agent, an extrusion aid and a pore-forming agent to a ZnO solid superacid catalyst, mix them evenly to obtain a powder, drop deionized water and knead them thoroughly to obtain a wet strip material; 3) Put the wet strip material obtained in step 2) into an extrusion machine to extrude and form a strip-shaped wet body material. After air drying at room temperature, it is dried, then transferred to a crucible, and put into a tubular furnace for heat treatment in an air environment. After completion, it is naturally cooled to room temperature to obtain the formed SO4 2- / ZnO solid superacid catalyst.

2. The preparation method according to claim 1, characterized in that: In step 1), the concentration of the ammonium sulfate aqueous solution is 2.5 - 3.0 mol / L; the mass ratio of the ZnO support to the ammonium sulfate aqueous solution is 1:3 - 1:4; the impregnation time is 10 - 12 h.

3. The preparation method according to claim 1, characterized in that: In step 1), the drying temperature is 90 - 120 °C and the drying time is 3 - 5 h; the heat treatment temperature is 450 - 500 °C and the heat treatment time is 2 - 5 h.

4. The preparation method according to claim 1, characterized in that: In step 2), the mass ratio of deionized water to powder is 0.60 - 0.65; the pore-forming agent is activated carbon, and the addition amount is 0.4 - 0.6% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst; the peptizing agent is an aqueous nitric acid solution with a concentration of 1.8 - 2.2 mol / L, and the addition amount is 8 - 10% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst; the extrusion aid is methyl cellulose, and the addition amount is 0.8 - 1.2% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst; the binder is pseudo-boehmite, and the addition amount is 23 - 26% of the mass of the powdered SO4 2- / ZnO solid superacid catalyst.

5. The preparation method according to claim 1, wherein: In step 3), the drying temperature is 90 - 120 °C and the drying time is 3 - 5 h; the heat treatment temperature is 450 - 500 °C and the heat treatment time is 2 - 5 h.

6. The preparation method according to claim 1, wherein: In step 3), the diameter of the strip-shaped wet body material is 2.0 - 3.0 mm and the length is 1.5 - 2.0 mm; the room temperature air-drying time is 10 - 12 h.

7. The formed SO4 2- / ZnO solid superacid catalyst obtained by the preparation method according to any one of claims 1 to 6.

8. The shaped SO4 2- / ZnO solid superacid catalyst according to claim 7, characterized in that: The formed SO4 2- / ZnO solid superacid catalyst has a mechanical strength of 80 - 100 N·cm -1 , and a specific surface area of 15 - 30 m 2 / g.

Images