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DE-102025130178-A1 - Pyrolysis process

DE102025130178A1DE 102025130178 A1DE102025130178 A1DE 102025130178A1DE-102025130178-A1

Abstract

The subject of the present application is a process for the pyrolytic production of benzoic acid and/or terephthalic acid from PET-containing materials, in which a melt of a PET-containing material 2 is located in a zone “A” in the lower region of a pyrolysis reactor 1 at a temperature of 350 to 750 °C, in particular of 380 to 600 °C, most preferably of 400 to 500 °C, and the resulting pyrolysis gas cools down in a zone “C”, so that a benzoic acid and/or terephthalic acid-containing material is deposited.

Inventors

  • Marco Braun
  • Hans-Willi Kling

Assignees

  • Bergische Universität Wuppertal, Körperschaft des öffentlichen Rechts
  • Coroplast Fritz Müller GmbH & Co. K. G.

Dates

Publication Date
20260513
Application Date
20250730
Priority Date
20241112

Claims (16)

  1. A process for the pyrolytic production of benzoic acid and/or terephthalic acid from PET-containing materials, characterized in that - a melt of a PET-containing material 2 is located in a zone “A” in the lower region of a pyrolysis reactor 1 at a temperature of 350 to 750 °C, in particular 380 to 600 °C, most preferably 400 to 500 °C, and - the resulting pyrolysis gas cools down in a zone “C”, so that a benzoic acid and/or terephthalic acid-containing material is deposited.
  2. Procedure according to Claim 1 , characterized in that - the resulting pyrolysis gas first flows through a zone "D" before reaching zone "C", in which at least part of the resulting pyrolysis gas condenses, and the remaining pyrolysis gas flows into zone "C" of the pyrolysis apparatus, and - at least part of the condensate is returned to the flowing pyrolysis gas within the pyrolysis reactor 1 and fed back to the pyrolysis process, and any remaining condensate flows into zone "C" of the pyrolysis apparatus.
  3. Procedure according to Claim 2 , characterized in that the zone “D” is located in a cooler zone of the pyrolysis reactor 1 and/or in a separate component, in particular in a downstream dephlegmator.
  4. Procedure according to one of the Claims 2 or 3 , characterized in that zone “D” has a temperature in the range of 125 to 250 °C, in particular in the range of 130 to 200 °C.
  5. Procedure according to one of the Claims 2 until 4 , characterized in that the zone “D” has a volume that is larger than the volume of the melt of the PET-containing material.
  6. Procedure according to one of the Claims 2 until 5 , characterized in that the part of the resulting pyrolysis gas which flows from zone “D” in gaseous form into zone “C” of the pyrolysis apparatus contains at least 25 wt.% benzoic acid.
  7. Procedure according to Claim 6 , characterized in that the reflux rate of the benzoic acid contained in the resulting pyrolysis gas is in a mass ratio of 1 : 1 to 1 : 10 (wt% benzoic acid that is transferred directly from zone “D” as part of the gas and/or optionally the condensate to zone “C” : wt% benzoic acid that is returned to the pyrolysis area from zone “D” as part of the condensate).
  8. Procedure according to one of the Claims 2 until 7 , characterized in that the returning condensate within the pyrolysis reactor 1 picks up precipitated solid intermediate products and feeds them back into the pyrolysis process.
  9. Procedure according to one of the Claims 2 until 8 , characterized in that the returning condensate contains at least 1 wt.% terephthalic acid, in particular at least 5 wt.% terephthalic acid.
  10. Procedure according to one of the Claims 1 until 9 , characterized in that solid intermediate products deposited within the pyrolysis reactor 1 are mechanically reintroduced to the pyrolysis process.
  11. Procedure according to one of the Claims 1 until 10 , characterized in that the PET-containing material contains at least 30 wt.% PET, in particular at least 40 wt.% PET, most preferably 50 to 100 wt.% PET.
  12. Procedure according to one of the Claims 1 until 11 , characterized in that the PET-containing material is an adhesive tape comprising a PET-containing carrier which is provided with an adhesive layer on at least one side.
  13. Procedure according to one of the Claims 1 until 12 , characterized in that the benzoic acid and/or terephthalic acid-containing material deposited in zone “C” contains at least 55 wt.% benzoic acid, in particular at least 70 wt.% benzoic acid, most preferably at least 85 wt.% benzoic acid.
  14. Procedure according to one of the Claims 1 until 13 , characterized in that the melt of the PET-containing material is largely free of added catalysts.
  15. Procedure according to one of the Claims 1 until 14 characterized in that the melt of the PET-containing material is largely free of added solvents.
  16. Procedure according to one of the Claims 1 until 15 characterized in that the melt of the PET-containing material is largely free of added additives.

Description

The invention relates to a process for producing benzoic acid and/or terephthalic acid from polyethylene terephthalate (PET)-containing materials, in particular a process for producing solid benzoic acid-containing materials according to the claims. Terephthalic acid is a monomeric component of PET. Annual production of terephthalic acid was 37.3 million tons in 2006 and has increased significantly since then. Besides PET production, terephthalic acid is also used in the production of other technical polyesters, such as polybutylene terephthalate (PBT) for thermally demanding automotive applications in engine compartments and aromatic polyamides of the aramid type (e.g., Kevlar® ) for high-tensile fibers. Benzoic acid is a raw material with a wide range of industrial applications. It is used as a preservative (E 210) in the cosmetics, food, and tobacco industries. Due to its superior solubility, the salts of benzoic acid, such as sodium benzoate (E 211), potassium benzoate (E 212), and calcium benzoate (E 213), are also widely used. Furthermore, benzoic acid is a starting material for fragrances, plasticizers, and local anesthetics (benzoic acid esters, such as ethyl benzoate), as well as biocides (benzyl esters of benzoic acid). In the chemical industry, benzoic acid is produced in large quantities by the oxidation of toluene, and terephthalic acid by the oxidation of p-xylene. The two starting materials, toluene and p-xylene, are primarily obtained through the distillation of crude oil in refineries and are therefore based on fossil resources. Two major problems are associated with fossil resources: their limited availability and the release of CO₂ during their use. Consequently, industry is seeking alternative sources for such raw materials. Recently, a number of projects have been launched with the aim of producing raw materials on an industrial scale from existing products. Due to the increasing consumption of plastics in recent decades and the resulting volumes of waste, the recycling of plastics has moved into sharper focus. In addition to traditional recycling, which aims to recover the original raw material from existing products, new processes have recently become established that focus not on recovering the original raw material, but rather on creating a different valuable material. An example of such a recycling process is advertised by BASF under the name "ChemCycling", in which a pyrolysis oil is obtained from mixed plastic waste, which, after appropriate purification, can be used again at the beginning of BASF's integrated production process. The object of the present invention was therefore to develop an alternative manufacturing process for benzoic acid and/or terephthalic acid, in particular for the production of benzoic acid, which does not rely on the use of new fossil raw materials and is characterized by good yield and high purity of the products. Furthermore, the object of the present invention was to recycle existing plastic resources and to reintroduce the resulting products into the value chain, thus enabling a circular economy. In the course of the work underlying this invention, it was found that benzoic acid and/or terephthalic acid, in particular benzoic acid, can be obtained in good yield and high purity from PET-containing materials using a simple pyrolytic process, whereby, in contrast to the described and known processes, no or very little pyrolysis oil is produced. A first preferred embodiment of the present invention relates to a process for the pyrolytic production of benzoic acid and/or terephthalic acid from PET-containing materials, wherein - a melt of PET-containing material is located in a zone “A” in the lower region of a pyrolysis reactor at a temperature of 350 to 750 °C, in particular 380 to 600 °C, most preferably 400 to 500 °C, and - the resulting pyrolysis gas cools down in a zone “C”, so that a material containing benzoic acid and/or terephthalic acid is deposited. The process according to the invention is preferably carried out in a pyrolysis apparatus which may have one or more process engineering components, but must necessarily include at least one so-called "pyrolysis reactor" in which the actual pyrolysis reaction takes place. According to the invention, the term "benzoic acid" refers to the basic benzoic acid compound itself, but also to its salts and esters (benzoates). A restriction of this term to the basic benzoic acid compound itself may be preferred according to the invention. According to the invention, the term "terephthalic acid" refers to the basic structure of terephthalic acid itself, but also to its salts and esters (terephthalates). According to the invention, restricting this term to the basic structure of terephthalic acid itself may be preferred. According to the invention, the term "pyrolysis gas" refers to the products formed during pyrolysis that leave the reaction zone in a gaseous state. The invention also includes gases containi