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Method and reaction device for catalytically depolymerizing polymethyl methacrylate into monomer

The technology of polymethyl methacrylate and reaction device is applied in chemical instruments and methods, preparation of carboxylate, preparation of organic compounds, etc., and can solve the problems of fluidized bed bed collapse, serious coking, high viscosity, etc. Achieve the effect of increasing dispersibility and mixing uniformity, reducing pyrolysis temperature and avoiding energy loss

Active Publication Date: 2022-06-17
BEIJING UNIV OF CHEM TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] At present, the relatively mature polymethyl methacrylate polymer depolymerization method in the industry is a fixed bed pyrolysis method, that is, the waste polymethyl methacrylate is added to the reaction kettle and heated at the bottom of the kettle to produce methyl methacrylate. The ester leaves the top of the reactor in a gaseous state, and the liquid containing methyl methacrylate is collected after cooling, and then refined; the problem of this method is that the monomer yield is low, about 75%, and the coking is serious, and the pyrolysis takes about one day Need to stop for cleaning, which belongs to semi-continuous production
When fluidized bed reactor is applied to the depolymerization of polymethyl methacrylate polymer, need to use a large amount of inert gas heat carriers (generally N 2 ), N 2 The temperature rise (for pyrolysis of polymethyl methacrylate) and cooling (recovery of monomer methyl methacrylate), resulting in a large amount of energy consumption
In addition, the polymethyl methacrylate polymer has a high viscosity after melting, so that the material and the fluidized medium (usually sand) will adhere to form large particles, causing the bed to collapse.
Can know by above-mentioned document, fluidized-bed reactor and jet-fluidized-bed reactor have been applied in pyrolysis polymethyl methacrylate, but the collapse of fluidized bed layer, use a large amount of inert gas and heat consumption Large and other problems limit its application. In order to solve the above problems, it is necessary to develop a new type of reactor for thermal depolymerization

Method used

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  • Method and reaction device for catalytically depolymerizing polymethyl methacrylate into monomer
  • Method and reaction device for catalytically depolymerizing polymethyl methacrylate into monomer

Examples

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Effect test

Embodiment 1

[0040] A method for catalytic depolymerization of polymethyl methacrylate into monomer, comprising the steps:

[0041] S1: Prepare the first catalyst, which is a spherical Al with a diameter of 3 mm without metal oxide support 2 O 3 Particles with a specific surface area of ​​360m 2 / g.

[0042] S2: Weigh 1500g of spherical Al in step S1 2 O 3 , added to the rotary furnace reactor, in N 2 The rotary furnace reactor was heated to a depolymerization temperature of 400°C under atmosphere (20ml / min).

[0043] S3: 150g of discarded polymethyl methacrylate is added to the rotary furnace reactor of step S2 by the screw feeder, the feed rate is 5g / min, and the thermal depolymerization reaction occurs under normal pressure for 30min, and the monomer gas is removed from the rotary furnace. The outlet of the reactor was discharged, and the liquid phase product was collected after condensation, and finally 134.6 g of liquid oil was obtained.

[0044] The rotary furnace reactor of t...

Embodiment 2

[0049] A method for catalytic depolymerization of polymethyl methacrylate into monomer, comprising the steps:

[0050] S1: Prepare the first catalyst, which is a spherical Al with a diameter of 3 mm supported on MgO and NiO 2 O 3 (The mass ratio of MgO and NiO is 1:1, and the loading amount is 3 wt%). First, the metal oxide catalyst was prepared by an equal volume ultrasonic impregnation method. 11.0 g of magnesium nitrate and 11.7 g of nickel nitrate hexahydrate were dissolved in 240 g of deionized water, and the aqueous solution was added to a spherical Al containing 3 mm in diameter. 2 O 3 (194.0g, the specific surface area is 360m 2 / g), ultrasonically vibrated for 5 h to obtain a catalyst precursor. The precursor was dried in a vacuum drying oven at 70 °C for 12 h, then transferred to a tube furnace reactor, calcined in an air atmosphere, and the tube furnace reactor was heated to 650 °C, and at this temperature After holding for 3h, 200g of bimetallic oxide catalyst...

Embodiment 3

[0056] A method for catalytic depolymerization of polymethyl methacrylate into monomer, comprising the steps:

[0057] S1: Prepare the first catalyst, which is a 4mm diameter spherical Al supporting MgO and NiO 2 O 3 (The mass ratio of MgO and NiO is 1:1, the loading is 3wt%), and its specific surface area is 360m 2 / g.

[0058] S2: Weigh 1500g of spherical Al with a diameter of 4 mm supporting MgO and NiO in step S1 2 O 3 , added to the rotary furnace reactor, in N 2 The rotary furnace reactor was heated to a depolymerization temperature of 350°C under atmosphere (20ml / min).

[0059] S3: 150g of waste polymethyl methacrylate is added to the rotary furnace reactor of step S2 by the screw feeder, the feed rate is 5g / min, the thermal depolymerization reaction occurs under normal pressure for 30min, and the monomer gas is reacted from the rotary furnace The outlet of the device was discharged, and the liquid phase product was collected after condensation, and finally 136.8 ...

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Abstract

The invention provides a method and a device for depolymerizing polymethyl methacrylate into a monomer, and particularly relates to a method and a reaction device for catalytically depolymerizing polymethyl methacrylate into a monomer. The method comprises the following steps: preparing a first catalyst; adding a first catalyst into the reaction device, and heating to a depolymerization temperature; adding polymethyl methacrylate into the reaction device, carrying out thermal depolymerization reaction under normal pressure, discharging monomer gas from an outlet of the reaction device, condensing, and collecting a monomer product. The device is a rotary furnace reaction device. By designing the rotary furnace reaction system and adjusting the catalyst and the adding process thereof, the mass and heat transfer effect is obviously improved, the depolymerization selectivity is improved, and the product yield is improved; the depolymerization temperature is reduced, and the energy consumption is reduced; and the inactivated catalyst can be continuously discharged for in-situ regeneration, so that continuous production is realized.

Description

technical field [0001] The invention relates to a method and a device for depolymerizing polymethyl methacrylate into monomers, in particular to a method and a reaction device for catalyzing the depolymerization of polymethyl methacrylate into monomers. Background technique [0002] Polymethyl methacrylate polymer products are widely used in people's daily life. Such as car lampshade, license plate logo plate, bathroom door and window decorative baffle, craft decoration dust plate, artificial bone, artificial tooth substrate, etc., polymethyl methacrylate polymer can be seen. Although a series of products of polymethyl methacrylate polymer have brought a lot of convenience to human beings, a large amount of polymethyl methacrylate polymer becomes waste after being used, resulting in a great waste of resources. Due to the stable chemical properties of polymethyl methacrylate, it is difficult to directly decompose and recycle it in nature, which also causes serious environmen...

Claims

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Application Information

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IPC IPC(8): C07C67/00C07C69/54B01J23/755B01J23/80B01J23/656B01J21/04B01J35/10B01J8/10B01J8/08
CPCC07C67/00B01J23/755B01J23/80B01J23/6562B01J21/04B01J8/10B01J8/087B01J2208/00212B01J35/615C07C69/54Y02W30/62
Inventor 吴卫泽杨佳林任树行
Owner BEIJING UNIV OF CHEM TECH
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