阅读说明：本技术 一种新型高效有机玻璃回收工艺 (Novel efficient organic glass recovery process ) 是由 徐文 徐阳阳 虞成隆 虞海波 于 2021-01-25 设计创作，主要内容包括：本发明公开了一种新型高效有机玻璃回收工艺,通过配置正戊烷、环己烷、丙酮的混合溶剂,使其可在热解温度和压力条件下形成超临界状态,能提升催化剂活化中心的有效利用率,有效提升催化效率,并能将催化热解的温度降低；催化剂采用乙酰丙酮钼、二乙酰丙酮镍、二(乙酰丙酮)铂的混合体系,有助于降低活化温度,并且催化效率获得提升；本发明热解温度降低,PMMA的无规断链极难发生,热解杂质少,甲基丙烯酸甲酯回收率和纯度极高,并且简化了提纯工艺,其环境效益和经济效益均极为突出。(The invention discloses a novel high-efficiency organic glass recovery process, which can form a supercritical state under the conditions of pyrolysis temperature and pressure by preparing a mixed solvent of n-pentane, cyclohexane and acetone, can improve the effective utilization rate of a catalyst activation center, effectively improve the catalytic efficiency and reduce the temperature of catalytic pyrolysis; the catalyst adopts a mixed system of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetonate), which is beneficial to reducing the activation temperature and improving the catalytic efficiency; the invention has the advantages of low pyrolysis temperature, difficult occurrence of PMMA random chain scission, less pyrolysis impurities, high recovery rate and purity of methyl methacrylate, simplified purification process and outstanding environmental benefit and economic benefit.)

1. A novel efficient organic glass recovery process is characterized in that: the recovery process comprises the following specific steps:

(1) grinding

Drying PMMA for 1-2 h at 105-110 ℃, grinding in multiple stages after drying to make the particle size reach 3-8 μm, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass of 1.5-2.3 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent with the volume ratio of n-pentane to cyclohexane to acetone being 10-12: 1-2: 2-3, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the final solvent liquid level can sink over the catalyst fixing layer;

(3) pyrolysis

Sealing and pressurizing the pyrolysis furnace to 5.0-5.5 MPa, heating to 200-220 ℃ to form a supercritical state in the pyrolysis furnace, wherein the pyrolysis time is 1-2 h;

(4) purification of

And after pyrolysis is finished, cooling to 70-80 ℃, keeping the temperature, starting pressure relief and distillation, and obtaining the recovered methyl methacrylate at the bottom of the pyrolysis furnace.

2. A novel process for the recycling of organic glass with high efficiency as claimed in claim 1, characterized in that: the recovery process comprises the following steps:

(1) grinding

Drying PMMA for 2h at 110 ℃, grinding the PMMA in multiple stages after drying to ensure that the particle size of the PMMA reaches 5 mu m, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass 2.0 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent of n-pentane, cyclohexane and acetone in a volume ratio of 11:1:2, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the liquid level of the final solvent can be submerged in the catalyst fixing layer;

(3) pyrolysis

Sealing the pyrolysis furnace, pressurizing to 5.5MPa, heating to 200 ℃ to enable the pyrolysis furnace to form a supercritical state, wherein the pyrolysis time is 1 h;

(4) purification of

And after pyrolysis is finished, cooling to 75 ℃, keeping the temperature, starting pressure relief and distillation, wherein the bottom of the pyrolysis furnace is the recycled methyl methacrylate.

3. A novel process for the recovery of high efficiency plastic glazing as claimed in claim 1 or 2, wherein: the preparation method of the catalyst fixed layer comprises the following steps:

(1) the substrate material of the catalyst fixing layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 200 meshes/in²300 mesh/in²Obtaining a catalyst fixed layer substrate;

(2) immersing a catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetonate and platinum bis (acetylacetone) in a mass ratio of 3-5: 1-2, which is 1-3% of the mass of the catalyst fixing layer substrate, and epoxy chloropropane in a mass ratio of 3-5% of the mass of the catalyst fixing layer substrate, dropwise adding a trace amount of hydrochloric acid, heating to 50-60 ℃, reacting for 3-4 h, taking out the catalyst fixing layer substrate, washing with purified water for 3-5 times, and drying to obtain a catalyst fixing layer;

(3) and fixing the prepared catalyst fixing layer at the bottom of the pyrolysis furnace, and keeping the mass of the catalyst fixing layer to be 1/3-1/2 of the mass of the pyrolyzed PMMA particles.

4. A novel process for the recycling of organic glass with high efficiency as claimed in claim 3, characterized in that: the preparation method of the catalyst fixed layer comprises the following steps:

(1) the base material of the catalyst fixed layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 300 meshes/in²Obtaining a catalyst fixed layer substrate;

(2) soaking the catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetone) in a mass ratio of 4:2:1, which is 2% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 4% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 50 ℃, reacting for 4 hours, taking out the catalyst fixing layer substrate, washing for 5 times by using purified water, and then drying to obtain a catalyst fixing layer;

(3) the prepared catalyst fixed layer is fixed at the bottom of the pyrolysis furnace, and the mass of the catalyst fixed layer is maintained to be 1/2 of the mass of the pyrolyzed PMMA particles.

5. A novel process for the recovery of high efficiency plastic glazing as claimed in claim 1 or 2, wherein: the pyrolysis furnace is connected with a condenser, and the temperature of the condenser is controlled to be 5-10 ℃.

6. A novel process for the recycling of organic glass with high efficiency as claimed in claim 3, characterized in that: the substrate material of the catalyst fixed layer is porous ceramic or cordierite.

7. A novel high efficiency organic glass recycling process according to claim 4, characterized by: the substrate material of the catalyst fixed layer is porous ceramic or cordierite.

8. Methyl methacrylate recovered by pyrolysis using a novel high efficiency organic glass recovery process according to claim 1 or 2, characterized in that: the recovery rate of the methyl methacrylate reaches more than 99%, and the purity of the methyl methacrylate reaches more than 99.5%, and the methyl methacrylate is colorless and transparent.

9. The methyl methacrylate of claim 8 wherein: 0.1 per mill to 0.3 per mill of polymerization inhibitor can be added into the methyl methacrylate.

10. A methyl methacrylate according to claim 9 wherein: the polymerization inhibitor is one or more of hydroquinone, p-benzoquinone and p-tert-butyl catechol.

Technical Field

The invention relates to a process for recovering organic glass, in particular to a novel efficient process for recovering organic glass.

Background

The organic glass is a popular name of polymethyl methacrylate, is abbreviated as PMMA and is a high molecular compound polymerized by methyl methacrylate, can transmit more than 92 percent of sunlight, has higher mechanical strength, certain heat resistance and cold resistance, corrosion resistance, good insulating property, stable size and easy molding; organic glass has better performance, has the advantages of light, beautiful and tough appearance, easy cleaning, easy processing, beautiful color, higher surface hardness and luster, good chemical corrosion resistance, high transparency, stable physical performance and the like, is widely applied to the fields of buildings, chemical engineering, industry, advertisements and the like, can be applied to lamps, instrument parts, optical lenses, ornaments and the like, and has wide application.

With the increase of world PMMA production capacity, the amount of leftover materials, scraps and waste after use in the production process is large, and the negative influence on the environment and the resource utilization rate is large. Therefore, the waste organic glass is effectively recycled, the environment is cleaned, and considerable economic benefits are increased.

In the prior art, PMMA is generally recovered by a thermal cracking method, and monomer methyl methacrylate is recovered. However, the prior art has the following defects: the pyrolysis temperature is high and can reach about 500 ℃; partial random chain scission is easy to occur when the pyrolysis temperature is too high, other byproducts such as water, methanol, methyl formate, methacrolein, coked substances and the like are formed, the recovery rate of methyl methacrylate is reduced, the impurities can reduce the purity and yellow color of the recovered methyl methacrylate, and the process is complex and the energy consumption is extremely high if purification is required; if the pyrolysis temperature is lowered, the pyrolysis efficiency is not high, and the production efficiency and economic benefits are reduced.

Disclosure of Invention

The invention develops a novel high-efficiency organic glass recovery process, which can control the pyrolysis temperature to be 200-220 ℃, ensure the pyrolysis efficiency, simultaneously enable the recovery rate of monomer methyl methacrylate to reach more than 99 percent, and greatly reduce the occurrence of random chain scission and the content of impurities.

A novel efficient organic glass recovery process comprises the following specific steps:

(1) grinding

Drying PMMA for 1-2 h at 105-110 ℃, grinding in multiple stages after drying to make the particle size reach 3-8 μm, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass of 1.5-2.3 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent with the volume ratio of n-pentane to cyclohexane to acetone being 10-12: 1-2: 2-3, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the final solvent liquid level can sink over the catalyst fixing layer;

(3) pyrolysis

Sealing and pressurizing the pyrolysis furnace to 5.0-5.5 MPa, heating to 200-220 ℃ to form a supercritical state in the pyrolysis furnace, wherein the pyrolysis time is 1-2 h;

(4) purification of

And after pyrolysis is finished, cooling to 70-80 ℃, keeping the temperature, starting pressure relief and distillation, and obtaining the recovered methyl methacrylate at the bottom of the pyrolysis furnace.

Further, the recovery process is preferably:

(1) grinding

Drying PMMA for 2h at 110 ℃, grinding the PMMA in multiple stages after drying to ensure that the particle size of the PMMA reaches 5 mu m, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass 2.0 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent of n-pentane, cyclohexane and acetone in a volume ratio of 11:1:2, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the liquid level of the final solvent can be submerged in the catalyst fixing layer;

(3) pyrolysis

Sealing the pyrolysis furnace, pressurizing to 5.5MPa, heating to 200 ℃ to enable the pyrolysis furnace to form a supercritical state, wherein the pyrolysis time is 1 h;

(4) purification of

And after pyrolysis is finished, cooling to 75 ℃, keeping the temperature, starting pressure relief and distillation, wherein the bottom of the pyrolysis furnace is the recycled methyl methacrylate.

Further, the preparation method of the catalyst fixed layer comprises the following steps:

(1) the substrate material of the catalyst fixing layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 200 meshes/in²300 mesh/in²Obtaining a catalyst fixed layer substrate;

(2) immersing a catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetonate and platinum bis (acetylacetone) in a mass ratio of 3-5: 1-2, which is 1-3% of the mass of the catalyst fixing layer substrate, and epoxy chloropropane in a mass ratio of 3-5% of the mass of the catalyst fixing layer substrate, dropwise adding a trace amount of hydrochloric acid, heating to 50-60 ℃, reacting for 3-4 h, taking out the catalyst fixing layer substrate, washing with purified water for 3-5 times, and drying to obtain a catalyst fixing layer;

(3) and fixing the prepared catalyst fixing layer at the bottom of the pyrolysis furnace, and keeping the mass of the catalyst fixing layer to be 1/3-1/2 of the mass of the pyrolyzed PMMA particles.

Further, the method for preparing the catalyst-fixed layer is preferably:

(1) the base material of the catalyst fixed layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 300 meshes/in²Obtaining a catalyst fixed layer substrate;

(2) soaking the catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetone) in a mass ratio of 4:2:1, which is 2% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 4% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 50 ℃, reacting for 4 hours, taking out the catalyst fixing layer substrate, washing for 5 times by using purified water, and then drying to obtain a catalyst fixing layer;

(3) the prepared catalyst fixed layer is fixed at the bottom of the pyrolysis furnace, and the mass of the catalyst fixed layer is maintained to be 1/2 of the mass of the pyrolyzed PMMA particles.

Furthermore, the pyrolysis furnace is connected with a condenser, and the temperature of the condenser is controlled to be 5-10 ℃. The condensed and recovered mixed solvent can be continuously used for pyrolysis of PMMA.

Furthermore, the substrate material of the catalyst fixing layer is porous ceramic or cordierite.

Furthermore, the recovery rate of the methyl methacrylate reaches more than 99%, and the purity of the methyl methacrylate reaches more than 99.5%, and the methyl methacrylate is colorless and transparent.

Furthermore, 0.1 per mill to 0.3 per mill of polymerization inhibitor can be added into the pyrolyzed and recovered methyl methacrylate, so as to be beneficial to storage.

Further, the polymerization inhibitor is one or more of hydroquinone, p-benzoquinone and p-tert-butyl catechol.

The methyl methacrylate recovered by pyrolysis in the invention can be directly used for the resynthesis of PMMA.

The invention has the advantages that:

1. according to the invention, the mixed solvent of n-pentane, cyclohexane and acetone is prepared to obtain a good solvent for pyrolyzing PMMA into methyl methacrylate monomer, and the compounded mixed solvent can form a supercritical state under the conditions of pyrolysis temperature and pressure, so that the contact between the catalyst and PMMA particles is enhanced, the effective utilization rate of the catalyst activation center is improved, the catalytic efficiency is effectively improved, and the temperature of catalytic pyrolysis can be reduced;

2. the catalyst adopts a mixed system of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetonate), mainly because the catalytic efficiency of platinum is high, but the activation temperature is higher, generally higher than 260 ℃, which is extremely unfavorable for the pyrolysis of PMMA particles at 200-220 ℃; based on the above, the invention adopts and preferably selects a mixed catalytic system of molybdenum, nickel and platinum, which is beneficial to reducing the activation temperature and improving the catalytic efficiency;

3. the PMMA particles are pyrolyzed at the temperature of 200-220 ℃ and under the pressure of 5.0-5.5 MPa, random chain scission of PMMA is extremely difficult to occur, the problems of low recovery rate and purity reduction of methyl methacrylate caused by too many impurities generated by pyrolysis are avoided, the purification process is simplified, and the environmental benefit and the economic benefit are extremely outstanding.

Drawings

FIG. 1 is a schematic view of a pyrolysis process apparatus of the present invention;

in the figure, 1-pyrolysis furnace, 2-catalyst fixed layer, 3-condenser

Detailed Description

Example 1

A novel efficient organic glass recovery process comprises the following specific steps:

(1) grinding

Drying PMMA for 2h at 105 ℃, grinding the PMMA in multiple stages after drying to enable the particle size of the PMMA to reach 3 mu m, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass 1.5 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent of n-pentane, cyclohexane and acetone in a volume ratio of 12:2:3, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the liquid level of the final solvent can be submerged in the catalyst fixing layer;

(3) pyrolysis

Sealing the pyrolysis furnace, pressurizing to 5.5MPa, heating to 220 ℃ to enable the pyrolysis furnace to form a supercritical state, wherein the pyrolysis time is 1 h;

(4) purification of

And after pyrolysis is finished, cooling to 80 ℃, keeping the temperature, starting pressure relief and distillation, and obtaining the recovered methyl methacrylate at the bottom of the pyrolysis furnace.

The preparation method of the catalyst fixed layer comprises the following steps:

(1) the substrate material of the catalyst fixing layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 200 meshes/in²Obtaining a catalyst fixed layer substrate;

(2) soaking a catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetone) in a mass ratio of 5:1:1, which is 3% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 5% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 50 ℃, reacting for 4 hours, taking out the catalyst fixing layer substrate, washing for 5 times by using purified water, and then drying to obtain a catalyst fixing layer;

(3) the prepared catalyst fixed layer is fixed at the bottom of the pyrolysis furnace, and the mass of the catalyst fixed layer is maintained to be 1/2 of the mass of the pyrolyzed PMMA particles.

The catalyst fixed layer substrate is made of porous ceramic.

Example 2

A novel high-efficiency organic glass recovery process comprises the following steps:

(1) grinding

Drying PMMA for 2h at 110 ℃, grinding the PMMA in multiple stages after drying to ensure that the particle size of the PMMA reaches 5 mu m, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass 2.0 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent of n-pentane, cyclohexane and acetone in a volume ratio of 11:1:2, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the liquid level of the final solvent can be submerged in the catalyst fixing layer;

(3) pyrolysis

Sealing the pyrolysis furnace, pressurizing to 5.5MPa, heating to 200 ℃ to enable the pyrolysis furnace to form a supercritical state, wherein the pyrolysis time is 1 h;

(4) purification of

And after pyrolysis is finished, cooling to 75 ℃, keeping the temperature, starting pressure relief and distillation, wherein the bottom of the pyrolysis furnace is the recycled methyl methacrylate.

The preparation method of the catalyst fixed layer comprises the following steps:

(1) the base material of the catalyst fixed layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 300 meshes/in²Obtaining a catalyst fixed layer substrate;

(2) soaking the catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetone) in a mass ratio of 4:2:1, which is 2% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 4% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 50 ℃, reacting for 4 hours, taking out the catalyst fixing layer substrate, washing for 5 times by using purified water, and then drying to obtain a catalyst fixing layer;

(3) the prepared catalyst fixed layer is fixed at the bottom of the pyrolysis furnace, and the mass of the catalyst fixed layer is maintained to be 1/2 of the mass of the pyrolyzed PMMA particles.

The catalyst fixed layer substrate is made of porous ceramic.

Example 3

A novel efficient organic glass recovery process comprises the following specific steps:

(1) grinding

Drying PMMA for 1h at 110 ℃, grinding the PMMA in multiple stages after drying to enable the particle size of the PMMA to reach 8 mu m, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass 2.3 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent with the volume ratio of n-pentane to cyclohexane to acetone being 10:1:2, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the liquid level of the final solvent can be submerged in the catalyst fixing layer;

(3) pyrolysis

Sealing the pyrolysis furnace, pressurizing to 5.0MPa, heating to 200 ℃ to enable the pyrolysis furnace to form a supercritical state, wherein the pyrolysis time is 2 hours;

(4) purification of

And after pyrolysis is finished, cooling to 70 ℃, keeping the temperature, starting pressure relief and distillation, wherein the bottom of the pyrolysis furnace is the recycled methyl methacrylate.

The preparation method of the catalyst fixed layer comprises the following steps:

(1) the base material of the catalyst fixed layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 300 meshes/in²Obtaining a catalyst fixed layer substrate;

(2) soaking a catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetone) in a mass ratio of 3:2:2, which is 1% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 3% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 60 ℃, reacting for 3 hours, taking out the catalyst fixing layer substrate, washing for 3 times by using purified water, and then drying to obtain a catalyst fixing layer;

(3) the prepared catalyst fixed layer is fixed at the bottom of the pyrolysis furnace, and the mass of the catalyst fixed layer is maintained to be 1/3 of the mass of the pyrolyzed PMMA particles.

The catalyst fixed layer substrate is made of cordierite.

Example 4

An organic glass recycling process comprises the following specific steps:

(1) grinding

Drying PMMA for 3h at 100 ℃, grinding the PMMA in multiple stages after drying to enable the particle size of the PMMA to reach 10 mu m, and then conveying the prepared PMMA particles to a pyrolysis furnace;

(2) mixing

Adding a solvent with the mass 2.5 times that of PMMA particles into a pyrolysis furnace, wherein the solvent is a mixed solvent of n-pentane, cyclohexane and acetone in a volume ratio of 9:3:4, and the pyrolysis furnace is provided with a catalyst fixing layer to ensure that the liquid level of the final solvent can be submerged in the catalyst fixing layer;

(3) pyrolysis

Sealing the pyrolysis furnace, pressurizing to 5.8MPa, heating to 230 ℃, and enabling the pyrolysis furnace to form a supercritical state, wherein the pyrolysis time is 3 hours;

(4) purification of

And after pyrolysis is finished, cooling to 90 ℃, keeping the temperature, starting pressure relief and distillation, wherein the bottom of the pyrolysis furnace is the recycled methyl methacrylate.

The preparation method of the catalyst fixed layer comprises the following steps:

(1) the substrate material of the catalyst fixed layer is made into a honeycomb shape suitable for a pyrolysis furnace, and the pore density is 180 meshes/in²Obtaining a catalyst fixed layer substrate;

(2) soaking the catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetoacetonate and platinum bis (acetylacetone) in a mass ratio of 2:3:3, which is 0.8% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 2% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 65 ℃, reacting for 2 hours, taking out the catalyst fixing layer substrate, washing for 2 times by using purified water, and then drying to obtain a catalyst fixing layer;

(3) the prepared catalyst fixed layer is fixed at the bottom of the pyrolysis furnace, and the mass of the catalyst fixed layer is maintained to be 1/4 of the mass of the pyrolyzed PMMA particles.

The catalyst fixed layer substrate is made of porous ceramic.

Comparative example 1

A recycling process of organic glass comprises the following steps: and (3) carrying out high-temperature pyrolysis, heating to 500 ℃, and directly pyrolyzing without adding a catalyst fixing layer to obtain the recycled methyl methacrylate.

Comparative example 2

A recycling process of organic glass comprises the following steps: a pyrolysis furnace with a catalyst fixed layer was used as a fixed bed reactor without adding a mixed solvent, the temperature and pressure were the same as those in example 2, and the time required for complete pyrolysis was 4 hours.

Comparative example 3

A recycling process of organic glass comprises the following steps: the mixed solvent was replaced with xylene, and the time required for complete pyrolysis was 5 hours as in example 2.

Comparative example 4

A recycling process of organic glass comprises the following steps: the mixed solvent was prepared as a mixed solvent of n-pentane to cyclohexane to acetone in a volume ratio of 9:3:4, and the time required for complete pyrolysis was 4 hours as in example 2.

Comparative example 5

A recycling process of organic glass comprises the following steps: the catalyst used was a commercial platinum catalyst NS-HC-5511 as in example 2, and the time required for complete pyrolysis was 6 hours.

Comparative example 6

A recycling process of organic glass comprises the following steps: the catalyst was prepared without using molybdenum acetylacetonate, and the time required for complete pyrolysis was 6h, as in example 2.

Comparative example 7

A recycling process of organic glass comprises the following steps: the catalyst was prepared without using nickel diacetone, and the time required for complete pyrolysis was 5h, as in example 2.

Comparative example 8

A recycling process of organic glass comprises the following steps: the catalyst was prepared without platinum bis (acetylacetonate), as in example 2, and the time required for complete pyrolysis was 6 h.

Comparative example 9

A recycling process of organic glass comprises the following steps: the preparation method of the catalyst fixed layer comprises the following step (2): soaking the catalyst fixing layer substrate into water, adding a mixture of molybdenum acetylacetonate, nickel diacetoacetonate and platinum bis (acetylacetone) in a mass ratio of 2:3:3, which is 0.8% of the mass of the catalyst fixing layer substrate, and epichlorohydrin, which is 2% of the mass of the catalyst fixing layer substrate, dropwise adding trace hydrochloric acid, heating to 65 ℃, reacting for 2 hours, taking out the catalyst fixing layer substrate, washing for 2 times by using purified water, and then drying to obtain a catalyst fixing layer; the rest is the same as example 2.

Comparative example 10

A recycling process of organic glass comprises the following steps: the mass of the catalyst anchor layer was 1/4 for the mass of the pyrolyzed PMMA particles, as in example 2.

Detection and analysis:

the purities of the unpurified methyl methacrylate prepared in each example and comparative example and the methanol contents therein, which represent the degree of occurrence of random chain scission, were checked by liquid chromatography, the recovery rate of methyl methacrylate was calculated and the color of methyl methacrylate was observed.

As can be seen from the above table, the mixed solvent of n-pentane, cyclohexane and acetone is prepared, so that the supercritical state can be formed under the conditions of pyrolysis temperature and pressure, the contact between the catalyst and PMMA particles is enhanced, the effective utilization rate of the catalyst activation center is improved, the catalytic efficiency is effectively improved, and the temperature of catalytic pyrolysis can be reduced; the catalyst adopts a mixed system of molybdenum acetylacetonate, nickel diacetylacetonate and platinum bis (acetylacetonate), which is beneficial to reducing the activation temperature and improving the catalytic efficiency; the invention has the advantages of reducing the pyrolysis temperature, preventing PMMA from random chain scission, avoiding the problems of low recovery rate and purity reduction of methyl methacrylate caused by too many impurities generated by pyrolysis, simplifying the purification process and having outstanding environmental benefit and economic benefit.

And finally: the above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention are intended to be included in the scope of the present invention.