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CN-122029224-A - Method for preparing isobutene from butyl rubber raw material

CN122029224ACN 122029224 ACN122029224 ACN 122029224ACN-122029224-A

Abstract

The present invention relates to a process for the preparation of isobutene from a feedstock comprising at least 50% by weight of butyl rubber, referred to as recycled feedstock, said process comprising a pyrolysis step.

Inventors

  • V. Anselmo Hadad
  • L. Maisoniv
  • MATHIEU FREDERIC
  • R grace dagger-axe
  • M. Sartre

Assignees

  • 米其林集团总公司

Dates

Publication Date
20260512
Application Date
20241015
Priority Date
20231019

Claims (12)

  1. 1. A process for the preparation of isobutene from a feedstock comprising at least 40% by weight of butyl rubber, referred to as recovered feedstock, said process comprising at least the following steps: a. A preparation step of the recovered raw material to prepare crushed aggregates; b. A pyrolysis step of the feedstock from step a) comprising a pyrolysis zone operating at a temperature in the range of 50 ℃ to 475 ℃ and an absolute pressure in the range of 0.1 bar to 2 bar, and producing at least a gaseous pyrolysis stream and a liquid pyrolysis stream; c. At least the separation step of the gaseous pyrolysis stream feed from step b) is used to produce an isobutylene-rich stream.
  2. 2. Process for the preparation of isobutene according to the preceding claim, in which the recovered feedstock comprises at least 50% by weight of butyl rubber, preferably at least 60% by weight of butyl rubber, preferably at least 70% by weight of butyl rubber, preferably at least 80% by weight of butyl rubber, very preferably at least 90% by weight of butyl rubber, very preferably at least 95% by weight of butyl rubber.
  3. 3. The process for preparing isobutene according to any one of the preceding claims, wherein the butyl rubber is a copolymer based on isobutene and isoprene, preferably a halogenated copolymer based on isobutene and isoprene.
  4. 4. The process for preparing isobutene according to anyone of the preceding claims, wherein during step a) the recovered feedstock is reduced to particles having an average size ranging from 10 microns to 2 cm.
  5. 5. The process for preparing isobutene according to any one of the preceding claims, wherein the pyrolysis zone is a microwave heat assisted pyrolysis zone.
  6. 6. Process for the preparation of isobutene according to the preceding claim, in which the power supplied by the microwave device is between 0.1 and 10 kw per kg of feedstock, preferably between 0.1 and 5 kw per kg of feedstock, preferably between 0.5 and 4 kw per kg of feedstock, preferably between 1 and 4 kw per kg of feedstock.
  7. 7. The process for preparing isobutene according to any one of the preceding claims, wherein the pyrolysis step is carried out under an inert atmosphere, preferably under a nitrogen atmosphere, at a pressure ranging from 0.1 bar to 2 bar, preferably from 0.5 bar to 1.5 bar, very preferably from 0.8 bar to 1.2 bar.
  8. 8. The process for preparing isobutene according to any one of the preceding claims, wherein the separation step c) comprises at least one section for gas-liquid separation by boiling point, said section comprising from 1 to 30 theoretical stages, known as "concentration section", operating at a pressure ranging from 1 to 20 bar.
  9. 9. The process for preparing isobutene according to any one of the preceding claims, wherein the separation step c) comprises a separation section called "finishing section", the feed of which is an isobutene-rich stream from the concentration section and produces an isobutene stream.
  10. 10. The process for preparing isobutene according to any one of the preceding claims, wherein the separation step c) comprises the heat input by the gaseous pyrolysis stream fed to the concentration section from step b) as the sole heat input to the reboiler.
  11. 11. The process for preparing isobutene according to claim 8 and any one of claims 9 to 10 when dependent on claim 8, wherein the concentration section is carried out by distillation at a pressure in the range of from 1 to 20 bar, comprising from 1 to 30 theoretical stages, the overhead condenser being operated at a temperature in the range of from-40 ℃ to-20 ℃, preferably from-35 ℃ to-25 ℃, the gaseous pyrolysis stream from step b) being fed from the bottom of the column.
  12. 12. The process for preparing isobutene according to claim 8, claims 9 to 10 when dependent on claim 8, and claim 11, wherein the concentration section is carried out by distillation at a pressure in the range of 3 to 10 bar, comprising 10 to 20 theoretical stages, the overhead condenser being operated at a temperature in the range of-60 ℃ to-40 ℃, preferably-55 ℃ to-45 ℃, the gaseous pyrolysis stream from step b) being fed from the bottom of the column.

Description

Method for preparing isobutene from butyl rubber raw material Technical Field The invention relates to the field of depolymerization and purification methods of butyl rubber compounds, and aims to prepare at least one isobutene monomer. Background Pneumatic tires (more commonly rubber products, such as conveyor belts) and non-pneumatic tires are complex objects composed of numerous components. For example, pneumatic tires are composed of over 200 different raw materials. In view of the pressure problems faced by renewable and fossil resources, it becomes important to obtain as much value as possible from resources represented by waste rubber products. However, recycling materials in scrap rubber articles (e.g., scrap tires) to make new pneumatic tires remains limited, not only because of the complexity of such recycling, but also because these components have a significant impact on the performance quality of the tire. Thus, these deterioration of performance quality can lead to the recycling of materials with an overall negative impact on the environment. Accordingly, there is a need for a process for recycling scrap rubber articles to prepare raw materials that will not degrade the performance quality of pneumatic tires when used, thereby reducing environmental impact. Considerable research has been conducted in this field, particularly in the recovery of oil produced by pyrolysis of tire residues. In this regard, documents EP 0928817, WO 2013/170358 and JP 2017/008214 teach the use of pyrolysis of pneumatic tire scraps to prepare tire-grade carbon black. In contrast, there has been little research on the recovery of so-called "butyl" rubber, which is a copolymer of isoprene and isobutylene (or 2-methylpropene), typically halogenated. These rubbers are useful in the manufacture of pneumatic innerliners, such as innerliners and innertubes for pneumatic tires, and articles such as cured bladders for pneumatic tires. Paper "Thermal degradation and pyrolysis study of brominated butyl rubber-based damping material"（Polymers for Advanced Technologies,, volume 31 (2), pages 204-213) explores the possibility of thermal degradation of halobutyl rubber. After the end of pyrolysis (carried out at a temperature ranging from 500 ℃ to 1000 ℃ for a residence time of the order of a few seconds), various compounds are formed, in particular the predominant (i.e. more than 50% by weight) isobutene dimers and trimers. To date, isobutene has been prepared from petroleum sources. Such monomers may have a variety of applications such as, but not limited to, use in the synthesis of Methyl Tertiary Butyl Ether (MTBE) and Ethyl Tertiary Butyl Ether (ETBE), both of which account for approximately three-quarters of the total consumption of isobutylene, tertiary butyl alcohol and butyl rubber. However, petroleum fractions based on compounds having 4 carbon atoms (referred to as "C 4 fractions") also contain large amounts of 1-butene, which has a boiling point very close to that of isobutene. However, 1-butene is a particularly undesirable impurity, especially in the preparation of butyl rubber, because it can reduce the quality of the sealing properties of the pneumatic innerliner. Therefore, the purification of isobutene for the synthesis of butyl rubber is particularly complicated. The object of the present invention is to prepare isobutene from recovered raw materials, so that it can be used as a monomer in a synthesis process, in particular for the preparation of butyl rubber, and to limit the consumption of petroleum-derived isobutene. Disclosure of Invention The present invention therefore relates to a process for the preparation of isobutene from a feedstock comprising at least 40% by weight of butyl rubber, referred to as recycled feedstock, said process comprising at least the following steps: a. A preparation step of the recovered raw material to prepare crushed aggregates; b. A pyrolysis step of the feedstock from step a) comprising a pyrolysis zone operating at a temperature in the range of 50 ℃ to 475 ℃ and an absolute pressure in the range of 0.1 bar to 2 bar, and producing at least a gaseous pyrolysis stream and a liquid pyrolysis stream; c. At least the separation step of the gaseous pyrolysis stream feed from step b) is used to produce an isobutylene-rich stream. Preferably, the recycled feedstock comprises at least 50 wt.% butyl rubber, preferably at least 60 wt.% butyl rubber, preferably at least 70 wt.% butyl rubber, preferably at least 80 wt.% butyl rubber, very preferably at least 90 wt.% butyl rubber, very preferably at least 95 wt.% butyl rubber. Preferably, the butyl rubber is a copolymer based on isobutylene and isoprene, preferably a halogenated copolymer based on isobutylene and isoprene. Preferably, during step a), the recovered raw material is reduced to particles having an average size ranging from 10 microns to 2 cm. Preferably, the pyrolysis section is a microwave heat assisted pyrolysis section. Pref