A method for treating by-product tar in the production of cyclohexyl methacrylate

Abstract

The present application relates to a kind of cyclohexyl methacrylate production in byproduct tar processing method, through ozone oxidation reaction and hydrogenation reaction can make tar decompose into 2-oxo propionic acid cyclohexyl ester, 2-hydroxy propionic acid cyclohexyl ester, improve the added value of product.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and specifically to a method for treating tar, a byproduct of cyclohexyl methacrylate production. Background Technology

[0002] Cyclohexyl methacrylate is a methacrylate monomer with a unique structure containing cyclic groups and double bonds. It can be used as a monomer or comonomer in solution polymerization or suspension polymerization. Its polymerized products have advantages such as high refractive index, excellent water resistance, abrasion resistance, chemical resistance, heat resistance, low shrinkage, and high hardness. Therefore, as a high-quality active crosslinking agent and diluent, it has been widely used in automotive body coatings, solvent-based coatings, high-solids coatings, powder coatings, water-soluble resins, polymeric flocculants, textile auxiliaries, petroleum pour point depressants, and medical materials.

[0003] The mainstream process for the industrial production of cyclohexyl methacrylate is through direct transesterification of methyl methacrylate and cyclohexanol. The product is separated by refining in a distillation column. Cyclohexyl methacrylate is prone to polymerization at high temperatures, and high-temperature distillation produces tar containing polycyclohexyl methacrylate, resulting in a decrease in product yield and an increase in raw material consumption. Taking a 10,000-ton / year cyclohexyl methacrylate production plant as an example, about 800 tons of waste tar are produced annually as a byproduct. Due to its complex composition and high boiling point, conventional distillation is difficult to separate and reuse the components. Industrially, it is generally treated as waste tar and incinerated, resulting in a great deal of waste.

[0004] How to reuse tar and increase the added value of the process is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for treating the tar produced as a byproduct in the production of cyclohexyl methacrylate. By using ozone oxidation, hydrogenation, and other methods, the carbon-carbon double bonds of the cyclohexyl methacrylate polymer are broken to generate high-value-added products such as cyclohexyl 2-oxopropionic acid and cyclohexyl 2-hydroxypropionic acid, which greatly reduces the amount of tar produced and increases the added value of the products.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for treating by-product tar in the production of cyclohexyl methacrylate includes the following steps:

[0008] (1) Add solvent to tar and mix well;

[0009] (2) Pass the ozone-oxygen mixture into the solution until the reaction is complete;

[0010] (3) Stop the flow of ozone-oxygen mixture and replace it with a reactive inert gas;

[0011] (4) The reaction solution after ozone oxidation is reacted with hydrogen in the presence of a catalyst.

[0012] In this invention, the tar is polycyclohexyl methacrylate-containing tar produced during the transesterification reaction of methyl methacrylate and cyclohexanol, followed by distillation in a distillation column.

[0013] In this invention, in step (1), the solvent is one or more of benzene, toluene, xylene or ethylbenzene, and the mass ratio of solvent to tar is 1-15:1, preferably 3-10:1;

[0014] In this invention, in step (2), the ozone-oxygen mixture contains 3-15% ozone and 85-97% oxygen by mass; the reaction is carried out at atmospheric pressure and 10-50°C.

[0015] In this invention, in step (2), the reaction tail gas is connected to an ozone gas concentration detector, and the ozone concentration remains unchanged, indicating that the reaction is complete.

[0016] In this invention, in step (3), an inert gas is continuously introduced into the solution for replacement until ozone and formaldehyde are no longer detectable in the exhaust gas, thus completing the replacement.

[0017] In this invention, nitrogen is preferably used as the reaction inert gas.

[0018] In this invention, the catalyst used in step (4) is a palladium-on-carbon catalyst, and the palladium content accounts for 1-10% of the catalyst mass, preferably 4-10%.

[0019] In step (4), the reaction temperature is 10-50℃, preferably 20-40℃;

[0020] In step (4), the reaction pressure is 2-10 MPaG; preferably 3-8 MPaG;

[0021] In step (4), the feed mass hourly space velocity of the reaction solution is 0.3-3 h⁻¹. -1 The hydrogen gas is preferably added as a mixture of hydrogen and nitrogen, with a volume hourly space velocity (VHSV) of 50-500 h⁻¹. -1 The mass fraction of hydrogen in the gas mixture is 20-60%.

[0022] In this invention, the solvent can be removed by distillation of the reaction solution, and further distillation yields pure cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention solves the problem of unusable waste tar by-products in the production of cyclohexyl methacrylate. 60%-80% of the tar can be converted into high-value-added cyclohexyl 2-oxopropionic acid and cyclohexyl 2-hydroxypropionic acid through steps such as ozonolysis and hydrogenation. The tar has a high recycling rate and is economical and environmentally friendly.

[0025] 2. This invention allows for the adjustment of reaction conditions such as the amount of hydrogen added, space velocity, and the degree of reaction, as well as the ratio of cyclohexyl 2-oxopropionic acid to cyclohexyl 2-hydroxypropionic acid, according to requirements. It offers high reaction flexibility and is easy to operate. Detailed Implementation

[0026] The present invention will be further illustrated below by way of embodiments, but the present invention is not limited to the embodiments described below. The present invention extends to any new feature or any new combination disclosed in the specification, as well as any new method or process step or any new combination disclosed.

[0027] I. Sources of main raw materials in the embodiments:

[0028] 1. Waste tar: The tar containing polycyclohexyl methacrylate produced in the pilot plant of Wanhua Chemical Group Co., Ltd., which is used for transesterification of methyl methacrylate and cyclohexanol, and then distilled through a distillation column.

[0029] 2. Ozone is produced by generating oxygen using an ozone generator;

[0030] 3. Palladium on Carbon Catalyst: Liaoning Haitai Technology Development Co., Ltd.

[0031] 4. Toluene, Xilong Scientific Co., Ltd., analytical grade;

[0032] 5. Ethylbenzene, Xilong Scientific Co., Ltd., analytical grade;

[0033] II. Product Analysis Methods in the Examples:

[0034] 1. Gas chromatography is used to analyze the components and content of reaction solutions and products. The correction factor method is used. The instrument manufacturer and model is Shimadzu 1020-plus.

[0035] Example 1

[0036] A benzene solution containing waste tar was prepared, wherein the mass of benzene was three times that of the tar. After thorough mixing, an ozone-oxygen mixture (10% ozone and 90% oxygen by mass) was introduced into the solution. The reaction pressure was atmospheric pressure, and the reaction temperature was 50°C. Gas flow was stopped when the ozone concentration in the tail gas remained constant as detected by the ozone concentration detector. Nitrogen gas was then introduced into the solution until no ozone or formaldehyde was detected in the tail gas. The intermediate solution obtained from ozone oxidation was continuously fed into a fixed-bed reactor, along with a continuous introduction of a hydrogen-nitrogen mixture (20% hydrogen by mass). The catalyst used in the fixed-bed reactor was a palladium-on-carbon catalyst with a palladium content of 4%. The reaction temperature was 20°C, the reaction pressure was 3 MPa, and the liquid hourly space velocity (LHSV) was 0.3 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen and nitrogen is 50 h⁻¹. -1 The liquid after the reaction was distilled to remove the solvent, yielding cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate, with a small amount of tar not participating in the reaction.

[0037] 2-Oxopropionic acid cyclohexyl ester

[0038] Hydrogen spectrum: 1 H NMR (500MHz, CDCl3) δ7.43(m,2H),7.29(m,3H),2.17(s,3H).

[0039] Carbon spectrum: 13 C NMR (125MHz, CDCl3) δ197.73,158.95,151.26,129.74,125.77,121.64,25.04.

[0040] 2-Hydroxypropionate cyclohexyl ester

[0041] Hydrogen spectrum: 1 H NMR (500MHz, CDCl3) δ7.47–7.33(m,3H),7.08(dd,J=7.4,1.4Hz,2H),4.29(q,J=5.8Hz,1H),2.60(s,1H),1.50(d,J=5.8Hz,3H).

[0042] Carbon spectrum: 13 C NMR (125MHz, CDCl3) δ173.86,151.17,129.88,125.58,122.09,66.87,19.83.

[0043] The specific results of the reaction are shown in Table 1;

[0044] Example 2

[0045] Prepare a benzene solution from waste tar, wherein the mass of ethylbenzene is 10 times that of the tar. After thorough mixing, introduce an ozone-oxygen mixture (15% ozone and 85% oxygen by mass) into the solution. Maintain atmospheric pressure and a reaction temperature of 10°C. Stop the gas flow when the ozone concentration detector detects no change in the ozone concentration in the tail gas. Introduce nitrogen into the solution until ozone and formaldehyde are no longer detectable in the tail gas. Continuously introduce the intermediate solution after ozone oxidation into a fixed-bed reactor, along with a continuous flow of a hydrogen-nitrogen mixture (60% hydrogen by mass). The catalyst used in the fixed-bed reactor is a palladium-on-carbon catalyst with a palladium content of 10%. The reaction temperature is 40°C, the reaction pressure is 8 MPa, and the liquid hourly space velocity (LHSV) is 3 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen and nitrogen is 500 h⁻¹. -1 The reacted liquid was distilled to remove the solvent, yielding cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate; a small amount of tar did not participate in the reaction. Specific results of the reaction are shown in Table 1.

[0046] Example 3

[0047] A benzene solution containing waste tar was prepared, wherein the mass of toluene was 5 times that of the tar. After thorough mixing, an ozone-oxygen mixture (7.5% ozone and 92.5% oxygen by mass) was introduced into the solution. The reaction pressure was atmospheric pressure, and the reaction temperature was 30°C. Gas flow was stopped when the ozone concentration in the tail gas remained constant as detected by the ozone concentration detector. Nitrogen gas was then introduced into the solution until no ozone or formaldehyde was detected in the tail gas. The intermediate solution after ozone oxidation was continuously fed into a fixed-bed reactor, along with a continuous introduction of a hydrogen-nitrogen mixture (50% hydrogen by mass). The catalyst used in the fixed-bed reactor was a palladium-on-carbon catalyst with a palladium content of 8%. The reaction temperature was 30°C, the reaction pressure was 6 MPa, and the liquid hourly space velocity (LHSV) was 3 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen and nitrogen is 250 h⁻¹. -1 The reacted liquid was distilled to remove the solvent, yielding cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate; a small amount of tar did not participate in the reaction. Specific results of the reaction are shown in Table 1.

[0048] Example 4

[0049] A benzene solution containing waste tar was prepared, wherein the mass of toluene was 6 times that of the tar. After thorough mixing, an ozone-oxygen mixture (5% ozone and 95% oxygen by mass) was introduced into the solution. The reaction pressure was atmospheric pressure, and the reaction temperature was 30°C. Gas flow was stopped when the ozone concentration in the tail gas remained constant as detected by the ozone concentration detector. Nitrogen gas was then introduced into the solution until no ozone or formaldehyde was detected in the tail gas. The intermediate solution after ozone oxidation was continuously fed into a fixed-bed reactor, along with a continuous introduction of a hydrogen-nitrogen mixture (50% hydrogen by mass). The catalyst used in the fixed-bed reactor was a palladium-on-carbon catalyst with a palladium content of 5%. The reaction temperature was 30°C, the reaction pressure was 4 MPa, and the mass hourly space velocity (MHV) of the reaction solution was 1 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen and nitrogen is 250 h⁻¹. -1 The reacted liquid was distilled to remove the solvent, yielding cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate; a small amount of tar did not participate in the reaction. Specific results of the reaction are shown in Table 1.

[0050] Example 5

[0051] A benzene solution containing waste tar was prepared, wherein the mass of ethylbenzene was 7 times that of the tar. After thorough mixing, an ozone-oxygen mixture (5% ozone and 95% oxygen by mass) was introduced into the solution. The reaction pressure was atmospheric pressure, and the reaction temperature was 25°C. Gas flow was stopped when the ozone concentration in the tail gas remained constant as detected by the ozone concentration detector. Nitrogen gas was then introduced into the solution until no ozone or formaldehyde was detected in the tail gas. The intermediate solution after ozone oxidation was continuously fed into a fixed-bed reactor, along with a continuous introduction of a hydrogen-nitrogen mixture (40% hydrogen by mass). The catalyst used in the fixed-bed reactor was a palladium-on-carbon catalyst with a palladium content of 5%. The reaction temperature was 30°C, the reaction pressure was 4 MPa, and the liquid hourly space velocity (LHSV) was 1.8 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen and nitrogen is 150 h⁻¹. -1 The reacted liquid was distilled to remove the solvent, yielding cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate; a small amount of tar did not participate in the reaction. Specific results of the reaction are shown in Table 1.

[0052] Example 6

[0053] A benzene solution containing waste tar was prepared, wherein the mass of toluene was 10 times that of the tar. After thorough mixing, an ozone-oxygen mixture (5% ozone and 95% oxygen by mass) was introduced into the solution. The reaction pressure was atmospheric pressure, and the reaction temperature was 35°C. Gas flow was stopped when the ozone concentration in the tail gas remained constant as detected by the ozone concentration detector. Nitrogen gas was then introduced into the solution until no ozone or formaldehyde was detected in the tail gas. The intermediate solution after ozone oxidation was continuously fed into a fixed-bed reactor, along with a continuous introduction of a hydrogen-nitrogen mixture (35% hydrogen by mass). The catalyst used in the fixed-bed reactor was a palladium-on-carbon catalyst with a palladium content of 5%. The reaction temperature was 30°C, the reaction pressure was 6 MPa, and the liquid hourly space velocity (LHSV) was 2.5 h⁻¹. -1 The volume hourly space velocity (VHSV) of hydrogen and nitrogen is 100 h⁻¹. -1 The reacted liquid was distilled to remove the solvent, yielding cyclohexyl 2-oxopropionate and cyclohexyl 2-hydroxypropionate; a small amount of tar did not participate in the reaction. Specific results of the reaction are shown in Table 1.

[0054] Table 1 shows the tar conversion rate and selectivity of each product in each example.

[0055] Serial Number Conversion rate % 2-Oxopropionic acid cyclohexyl ester selectivity % 2-Hydroxypropionate cyclohexyl ester selectivity % Example 1 78.2 8.9 91.1 Example 2 64.4 10.3 89.7 Example 3 73.7 7.9 92.1 Example 4 75.6 8.6 91.4 Example 5 68.4 11.9 88.1 Example 6 66.9 13.7 86.3

Claims

1. A method for treating by-product tar in the production of cyclohexyl methacrylate, characterized in that, Includes the following steps: (1) Add solvent to tar and mix well; (2) Pass the ozone-oxygen mixture into the solution until the reaction is complete; (3) Stop the flow of ozone-oxygen mixture and replace it with a reactive inert gas; (4) The reaction solution after ozone oxidation is reacted with hydrogen in the presence of a catalyst; The tar is polycyclohexyl methacrylate-containing tar produced during the transesterification reaction of methyl methacrylate and cyclohexanol, followed by distillation in a distillation column. In step (2), the ozone-oxygen mixture contains 3-15% ozone by mass and 85-97% oxygen by mass; the reaction is carried out at atmospheric pressure and 10-50°C. In step (3), an inert gas is continuously introduced into the solution for replacement until ozone and formaldehyde are no longer detectable in the tail gas, thus completing the replacement. In step (4), the catalyst used is a palladium-on-carbon catalyst, and the palladium content accounts for 1-10% of the catalyst mass. In step (4), the reaction temperature is 10-50℃; In step (4), the reaction pressure is 2-10 MPaG.

2. The processing method according to claim 1, characterized in that, In step (1), the solvent is one or more of benzene, toluene, xylene or ethylbenzene, and the mass ratio of solvent to tar is 1-15:

1.

3. The processing method according to claim 2, characterized in that, In step (1), the mass ratio of solvent to tar is 3-10:

1.

4. The processing method according to claim 1, characterized in that, In step (3), the inert gas for the reaction is nitrogen.

5. The processing method according to claim 1, characterized in that, In step (4), the catalyst used is a palladium on carbon catalyst, and the palladium content accounts for 4-10% of the catalyst mass.

6. The processing method according to claim 1, characterized in that, In step (4), the reaction temperature is 20-40℃.

7. The processing method according to claim 1, characterized in that, In step (4), the reaction pressure is 3-8 MPaG.

8. The processing method according to claim 1, characterized in that, In step (4), the feed mass hourly space velocity of the reaction solution is 0.3-3 h⁻¹. -1 .

9. The processing method according to claim 1, characterized in that, The hydrogen gas is added as a mixture of hydrogen and nitrogen, with a volume hourly space velocity (VHSV) of 50-500 h⁻¹. -1 The mass fraction of hydrogen in the gas mixture is 20-60%.