WO2021250685A1

WO2021250685A1 - Clog free condensation process for pet like polymer pyrolysis vapour

Info

Publication number: WO2021250685A1
Application number: PCT/IN2020/050658
Authority: WO
Inventors: Suhas Dixit
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-06-12
Filing date: 2020-07-28
Publication date: 2021-12-16
Anticipated expiration: 2022-12-12

Abstract

The present invention provides a novel process for condensation of polyethylene terephthalate like polymer pyrolysis vapour comprising fraction of Benzoic-acid and its derivatives. The process comprising of steps of supplying the pyrolysis reaction vapour to a direct contact condenser having inside temperature between 50 to 1200 degree Celsius, introducing a direct contact stripping oil-immiscible solvent stream that resulting into a mixture of pyrolysis oil with oil-immiscible solvent rich in Benzoic-acid and its derivatives, and phase separating at temperature between -50 to 200 degree Celsius to separate 'pyrolysis oil from oil-immiscible solvent stream rich in Benzoic-acid and its derivatives. The novel process recovers the pure benzoic acid and its derivative as well as prevents the clogging of condenser by avoiding the solidification of Benzoic-acid and its derivatives in the condenser pipe without hampering the value added product quality as well as quantity.

Description

TITLE OF THE INVENTION:

CLOG FREE CONDENSATION PROCESS FOR PET LIKE POLYMER PYROLYSIS VAPOUR

FIELD OF INVENTION:

The present invention relates to a process of clog-free condensation of polymer pyrolysis vapour. More specifically, present invention provides a process for condensation of polyethylene terephthalate like polymer pyrolysis vapour comprising fraction of Benzoic-acid and its derivatives, wherein the vapour produced during polyethylene terephthalate like polymer pyrolysis is condenser by stripping it using an oil immiscible solvent in a direct contact condenser. The temperature and pH of the oil immiscible solvent is kept as close as possible to the solubility of Benzoic-acid and its derivatives. The process exhibits clog -free condensation of pyrolysis oil fraction and eliminates the need for a discontinuation of pyrolysis reaction to clean the clog from condensers.

BACKGROUND OF THE INVENTION:

In the era of increasing utilisation of polymer plastics, the pyrolysis is considered as an effective and environmentally favourable process for the elimination of waste and landfilling. Which includes industrial waste and municipal waste, which contain undegradable plastics and rubber waste, especially such as all kinds of packaging, construction waste, car tires, scrap vehicles fraction containing polymer plastics. Polymer waste is mixture of many polymer, as multilayer packaging materials are commonly used in order to combine the respective performance of different polymers i.e. combination of polyethylene terephthalate (PET), Polyurethene (PU), polystyrene (PS), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PC), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), nylon, metallised PET etc.

Pyrolysis is a process, wherein polymeric material is heated in a pyrolysis reactor at an elevated temperature (between 400 °C and 1250 °C) and in the absence of free oxygen (O₂) to form raw pyrolytic vapours typically comprise condensable vapours, which can be condensed to fuel fractions, oil fractions, and other by-products.

A major problem faced by current industries in the pyrolysis field is their limited ability to be condensed out continuously condensable vapours if vapours are having a fraction of Benzoic -acid and derivatives thereof. Fraction of Benzoic- acid and derivatives thereof in a pyrolysis vapour is primarily due to presence of a fraction of Polyethylene terephthalate (PET) in the pyrolysis reaction feedstock as that we observed mainly in packaging wastes. But, the pyrolysis system never works continuously if any Polyethylene terephthalate (PET) is present in the feedstock which results in clogging of the condenser, receiver, and internal piping used for condensing the post pyrolysis stream. The clogging of condenser is because of solidification (sublimation) of one of the pyrolysis by-product of PET i.e. Benzoic-acid and its derivatives.

The same issue addressed by US 5,753,086A pyrolysis technique for mixed resin waste plastic is when the feedstock contains PET material due to its byproduct Benzoic -acid and derivatives thereof. Therefore, PET was not employed in experiment since its solid decomposition product tended to clog the apparatus because of deposition of sticky mass in internal wall of condenser, piping and receiver inlets. Which is forwardly terminated the pyrolyzing feedstock containing PET polymer. And leaving only way to incinerate or throw in landfill which considered as environment unfriendly process.

Review publication “FEEDSTOCK RECYCLING VIA WASTE PLASTIC PYROLYSIS” by Toshiaki Yoshioka in Journal of the Japan Petroleum Institute- 59(6):243-253 · November 2016, also discloses that polyvinyl chloride (PVC) and poly (ethylene terephthalate) (PET) produce corrosive gases and sublimating substances during pyrolysis, resulting in reduced quality of pyrolysis products, and damage to the treatment plant. Hence, the present invention has been made in consideration of the above- described condenser clogging problem and facing problem in efficient pyrolysis of such feedstock due to presence of sublimating substances in vapours, and an objective thereof is to provide a process for preventing the solidifcation of Benzoic-acid in condenser pipe without hampering the value added product quality as well as quantity and thereby preventing the clogging of pyrolysis apparatus when PET containing mixed plastic has been utilised as a feedstock.

Therefore, the inventor of the present invention provides a process for elimination of the quick solidification and deposition of Benzoic -acid and its derivatives during condensation step and provided by specific modifications to the process of the condensing of pyrolysis vapours.

SUMMARY OF THE INVENTION:

One of the objectives of the present invention is to provide a process of condensation for pyrolysis vapours for feedstock like polyethylene terephthalate polymer and mixture of any polymer with polyethylene terephthalate.

Second objective of the present invention is to provide the clog-free condensation process suitable for conducting pyrolysis of feedstock containing PET polymer in continuous manner.

Yet one more objective of the present invention is to provide the condensation process for in-line recovery of benzoic acid and its derivatives.

The present invention provides a process for condensation of polymer pyrolysis vapour comprising a fraction of Benzoic-acid and its derivatives, wherein the condensate produced during condensation pyrolysis reaction vapour is selectively removed by stripping it using an oil immiscible solvent. The temperature and pH of the oil immiscible solvent is kept as close as possible to the solubility of Benzoic-acid and its derivatives. The process exhibits clog -free condensation of pyrolysis oil fraction and eliminates the need for a discontinuation of pyrolysis reaction to clean the clog.

In an embodiment of the present invention, a clog-free condensation process for polymer (e.g. Polyethylene terephthalate, etc) pyrolysis reaction vapour containing the fraction of Benzoic-acid and its derivatives comprising steps of: i) Supplying the pyrolysis reaction vapour containing the fraction of Benzoic-acid and its derivatives to a direct contact condenser having inside temperature between -50 to 1200 degree Celsius, ii) Introducing a direct contact stripping oil-immiscible solvent stream for causing condensation of pyrolysis oil as well as Benzoic-acid and its derivatives; resulting into a mixture of pyrolysis oil with oil-immiscible solvent rich in Benzoic-acid and its derivatives, iii) Passing this mixture into a phase separator maintained at temperature between -50 to 200 degree Celsius to separate ‘pyrolysis oil from oil- immiscible solvent stream rich in Benzoic-acid and its derivatives;

Characterized in that the said process prevents the clogging of condenser by preventing the solidification of Benzoic-acid and its derivatives in the condenser pipe without hampering the value added product quality as well as quantity.

Further, the oil-immiscible solvent stream rich in Benzoic-acid and its derivatives of step iii) is subjected to precipitating of Benzoic-acid and its derivatives from the oil-immiscible solvent using precipitating technique. Wherein the precipitate is filtered to recover powder of Benzoic-acid and its derivatives and filtrate oil-immiscible solvent for reuse.

In accordance to present invention, the oil-immiscible solvent is selected from water, alkali water having pH between 7 to 14 or mixture thereof.

In accordance to one more embodiment, the precipitation/separation technique for selective recovery of Benzoic-acid are selected from the following techniques: (a) Cooling the oil-immiscible solvent stream rich in Benzoic-acid and its derivatives to temperature -50 to 90 degree Celsius, followed by fdtration,

(b) Adjusting pH of oil-immiscible solvent stream rich in Benzoic -acid and its derivatives from alkaline pH between 7 to 14 to acidic pH between

0.001 to 7, followed by fdtration,

(c) Evaporating the oil-immiscible solvent stream rich in Benzoic-acid and its derivatives at temperature between 0 to 150 degree Celsius in presence or absence of applied vacuum upto 0.1 bar, (d) Extracting the Benzoic-acid and its derivatives from the oil -immiscible solvent.

BRIEF DESCRIPTION OF DRAWINGS:

For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which:

Figure No. 1: Illustrates a process flow diagram as an embodiment of the present invention.

Figure No. 2: Illustrates GCMS spectra of Powder obtained in Example no. 1. Figure No. 1: Illustrates GCMS spectra of Powder obtained in Example no. 2.

DETAILED DESCRIPTION OF THE INVENTION:

Embodiments of the present invention reside primarily in a condensation process of pyrolysis vapours and a method of processing condensed stream to recover Benzoic -acid and its derivative, fuel fractions, oil fractions, and mazout. Accordingly, the process steps have been illustrated in concise schematic form in the drawing no. 1, showing only those specific details that are necessary for understanding the embodiments of the present invention, with the disclosure with excessive detail that will be readily apparent to those of ordinary skill in the art having the benefit of the present description.

The term "polymer", as used herein, refers to polymer materials which may be used as feedstock to pyrolysis reaction. Specific polymer include, by way of non- limiting example, polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PC), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), nylon, metallised PET, rubber and combination thereof.

The following describes the technical solutions in the embodiments of the present application with reference to the accompanying drawing in the embodiments of the present application.

The present invention provides a clog-free condensation process for pyrolysis vapour of pyrolysis reaction. As pyrolysis system never works if Polyethylene terephthalate (PET) is present in the feedstock which results in clogging of the condenser, receiver, and internal piping used for condensing the post pyrolysis stream.

Because of the aforementioned problem in pyrolysis of PET as producing Benzoic-acid and its derivatives as by-product, feedstock containing PET can mainly be taken to incineration, which is least favourable for the environment.

The present invention relates to a process of clog-free condensation of polymer pyrolysis vapour. More specifically, the present invention provides an efficient condensation process for vapours of polymer, plastics, mixed plastics feedstock that prevents a clogging of vapour condensation apparatus and thereby allows smooth continuous running of pyrolysis plant. The present invention also relates to the method for pyrolysis of PET mixed plastic waste without formation of clog in apparatus and continuous recovery of Benzoic-acid and its derivatives including other condensable hydrocarbons as a value added products of pyrolysis. In an embodiment of the present invention, a clog-free condensation process for polymer (e.g. Polyethylene terephthalate, etc) pyrolysis reaction vapour containing the fraction of Benzoic -acid and its derivatives comprising steps of: i) Supplying the pyrolysis reaction vapour containing the fraction of Benzoic-acid and its derivatives to a direct contact condenser having inside temperature between -50 to 1200 degree Celsius, ii) Introducing a direct contact stripping oil-immiscible solvent stream for causing condensation of pyrolysis oil as well as Benzoic -acid and its derivatives; resulting into a mixture of pyrolysis oil with oil-immiscible solvent rich in Benzoic-acid and its derivatives, iii) Passing this mixture into a phase separator maintained at temperature between -50 to 200 degree Celsius to separate ‘pyrolysis oil from oil- immiscible solvent stream rich in Benzoic-acid and its derivatives;

Further, the oil-immiscible solvent stream rich in Benzoic -acid and its derivatives of step iii) is subjected to precipitating of Benzoic -acid and its derivatives from the oil-immiscible solvent using precipitating technique. Wherein the precipitate is filtered to recover powder of Benzoic-acid and its derivatives and filtrate oil-immiscible solvent for reuse.

(b) Adjusting pH of oil-immiscible solvent stream rich in Benzoic -acid and its derivatives from alkaline pH between 7 to 14 to acidic pH between 0.001 to 7, followed by fdtration,

(c) Evaporating the oil-immiscible solvent stream rich in Benzoic-acid and its derivatives at temperature between 0 to 150 degree Celsius in presence or absence of applied vacuum upto 0.1 bar,

(d) Extracting the Benzoic-acid and its derivatives from the oil-immiscible solvent.

Accordingly, the alkali water is selected from solution of sodium hydroxide, potassium hydroxide, Calcium hydroxide, ammonia and ammonium hydroxide having pH between 7 to 14, to produce alkaline salts of Benzoic-acid and its derivatives. And acidic solution selected from solution of Phosphoric Acid, Sulphuric Acid, Nitric Acid, Acetic Acid, Perchloric Acid, Citric Acid, Hydrochloric Acid, Formic acid and phosphorus Acid having pH 0.001 to 7.

In accordance to second embodiment, the present invention further provides a process to synthesise the phenols using Benzoic-acid and its derivatives obtained in first embodiments, wherein the oil-immiscible solvent stream rich in Benzoic- acid and its derivatives of step iii) is subjected to oxidative reaction, by reacting Benzoic-acid and its derivatives with oxygen to produce phenols.

Further to the condensation process disclosed herein and not limiting thereto, the uncondensed vapour remaining may be supplied to next condensation process. It would be advantageous to condensed all fraction of vapours received from a pyrolysis reaction source as it is more environmentally friendly and economic to produce maximum value added products out of pyrolysis. It has been shown that the pyrolysis apparatus can continuously pyrolyze polymer containing fraction of polymer that may produce a fraction of Benzoic- acid and its derivatives as one of the fraction in vapours and continuously condensed and collect pure Benzoic -acid and its derivatives by employing a said condensation process . Further to this, the present clog-free condensation process can recover the Benzoic-acid in-line and with purity for use in further chemical industry as a raw material. These advantages are possible due to the use of the careful condensation process making the Benzoic-acid solubilize in the oil- immiscible solvent, which substantially prevents clogging of condenser that are utilized for condensation of value added products of pyrolysis reactions.

As mentioned above, while considerable emphasis has been placed herein on the particular features of this invention and numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this invention is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

The invention will now be more particularly described with reference to the following example.

Example 1: The process of condensation of pyrolysis reaction vapours comprising a fraction of benzoic acid (Referring to Figure no. 1) :

Point 1) Carried out pyrolysis of polymer waste (Polyethylene terephthalate) in a pyrolysis reactor at temperature between 400 to 600 degree Celsius to produce a char and pyrolysis reaction vapours containing the fraction of benzoic acid and its derivatives,

Point 2) The pyrolysis reaction vapours are passed through a direct contact condenser (Spray condenser) maintained at temperature between 50 to 90 degree Celsius. In this condenser the water was introduced as an oil immiscible solvent stream which also acted as a stripping stream for direct contact condensation. This resulted into a condensation of pyrolysis reaction vapours forming a mixture of pyrolysis oil and oil immiscible solvent rich in Benzoic-acid and its derivatives.

Point 3) The mixture of pyrolysis oil and oil immiscible solvent rich in Benzoic- acid and its derivatives was discharged from the direct contact condenser and conveyed to the phase separator,

Point 4) The mixture was passed to a phase separator maintained at temperature 50 to 90 degree Celsius to separate pyrolysis oil from oil -immiscible solvent stream rich in Benzoic-acid and its derivatives,

Point 5) Transferred oil-immiscible solvent stream rich in Benzoic-acid and its derivatives to heat exchanger to cool down the solution at temperature below 30 degree Celsius to precipitate out of Benzoic-acid and its derivatives, followed by filtrating out precipitate to obtained power of Benzoic -acid and its derivatives and filtrate oil-immiscible solvent (This is reheated to desired temperature and reused in direct contact condenser discussed in point 2). Precipitate was analysed for purity and identification.

Further, after point 4) one can perform the steps mentioned below in point 6 and 7) without precipitating out benzoic acid.

Point 6) Optionally, oil-immiscible solvent stream rich in Benzoic-acid and its derivatives can be discharge as liquid stream for further direct utilisation chemical in any suitable industry,

Point 7) Optionally, oil-immiscible solvent stream rich in Benzoic -acid and its derivatives can be subjected to oxidative reaction to produce phenols, The product of benzoic acid powder obtained in step 5) was characterized by melting point, solubility analysis and GCMS. The purity of benzoic acid was 87.51% .

Figure no. 2 illustrates the GCMS spectra of said powder content and following table provides the name of compounds identified in spectra:

TABLE NO. 1

• Solubility Testing : Solubility Testing of Benzoic acid after Purification of Precipitate: Purification of crude powder was done by washing twice with cold water and skimming traces of oil impurities, followed by recrystallisation using hot water.

TABLE NO. 2 Example 2: The process of condensation of pyrolysis reaction vapours comprising fraction of benzoic acid and its derivative like sodium benzoate using alkaline water:

Point 2) The pyrolysis reaction vapours are passed through a direct contact condenser (Spray condenser) maintained at room temperature of approximately 30 to 35 degree Celsius. In this condenser the alkaline water (sodium hydroxide solution having pH 10 (0.5 M NaOH) was introduced as an oil immiscible solvent stream which also acted as a stripping stream for direct contact condensation. This resulted into a condensation of pyrolysis reaction vapours forming a mixture of pyrolysis oil and oil immiscible solvent rich in Sodium Benzoate and its derivatives. The dosing speed is depend upon the required pH of mixture in phase separator.

Point 3) The mixture of pyrolysis oil and oil immiscible solvent rich in sodium Benzoate and its derivatives was discharged from the direct contact condenser and conveyed to the phase separator, Point 4) The mixture was passed to a phase separator maintained at room temperature 30 to 35 degree Celsius to separate pyrolysis oil from oil-immiscible solvent stream rich in sodium Benzoate and its derivatives,

Point 5)Transferred oil-immiscible solvent stream rich in sodium Benzoate and its derivatives to precipitating tank. The precipitation of benzoic acid and its derivatives was brought about by changing the pH to acidic (pH-4) by addition of hydrochloric acid (0.001M), followed by filtration to separate precipitate to obtained power of Benzoic-acid and its derivatives from the oil immiscible solvent. (This Oil immiscible solvent is treated with alkali to increase the pH and reused in the direct contact condenser discussed in point 2).

The product of benzoic acid powder obtained in step 5) was characterized by melting point, solubility analysis and GCMS. The purity of benzoic acid was 85.97% .

As stated in example 1, Further, after point 4) one can perform the steps mentioned below in point 6 and 7) without precipitating out benzoic acid.

Point 6) Optionally, oil-immiscible solvent stream rich in Benzoic -acid and its derivatives can be discharge as liquid stream for further direct utilisation chemical in any suitable industry,

Point 7) Optionally, oil-immiscible solvent stream rich in Benzoic -acid and its derivatives can be subjected to oxidative reaction to produce phenols.

Figure no. 3 illustrates the GCMS spectra of said powder content and following table provides the name of compounds identified in spectra:

TABLE NO. 3

Example 3: Trials with Different alkaline water and precipitating agents:

This experiment was carried out as that of Example 2 with different alkaline water and precipitating agents as mentioned in table below:

Trial no PET Content Oil- Precipitating Benzoic-acid % wt/wt in Immiscible Agent Yield (%) polymer solvent feedstock

Trial no. 1 100 lM/pH-9 0.0001 M /pH-3 60

Potassium Sulphuric Acid hydroxide

Trial No. 2 50 1.5 M / pH-8 0.01 M / pH-5 30 Calcium Acetic Acid hydroxide

TABLE NO. 4 Example 4: Effect on pressure developed on condenser with and without process developed as per present invention and recovery of Benzoic-acid and its derivatives:

TABLE NO. 5

Conclusion: When this invention is not used, Condenser clogging resulted in increased reactor pressure within 45 mins of starting the process. The reactor pressure was about to reach the 'reactor design pressure of 0.5kg/cm², this is when the reaction was stopped to ensure safety.

Claims

CLAIMS aim;

1. A clog-free condensation process for polymer (e.g. Polyethylene terephthalate, etc) pyrolysis reaction vapour containing the fraction of

Benzoic-acid and its derivatives comprising steps of: i) Supplying the pyrolysis reaction vapour containing the fraction of Benzoic-acid and its derivatives to a direct contact condenser having inside temperature between -50 to 1200 degree Celsius, ii) Introducing a direct contact stripping oil-immiscible solvent stream for causing condensation of pyrolysis oil as well as Benzoic-acid and its derivatives; resulting into a mixture of pyrolysis oil with oil- immiscible solvent rich in Benzoic-acid and its derivatives, iii) Passing this mixture into a phase separator maintained at temperature between -50 to 200 degree Celsius to separate ‘pyrolysis oil from oil-immiscible solvent stream rich in Benzoic-acid and its derivatives; characterized in that the process avoids the clogging of condensers due solidification of Benzoic-acid and its derivatives powder.

2. The clog -free condensation process as claimed in claim 1, wherein Oil- immiscible solvent stream rich in Benzoic-acid and its derivatives of step iii) is subjected to precipitating of benzoic acid and its derivatives from the oil-immiscible solvent using precipitating technique.

3. The clog-free condensation process as claimed in claim 2, wherein the precipitate is filtered to recover powder of benzoic acid and its derivatives and filtrate oil-immiscible solvent for reuse.

4. The clog -free condensation process as claimed in claim 2, wherein precipitation/separation technique are selected from the following techniques:

(a) Cooling the oil-immiscible solvent stream rich in Benzoic-acid and its derivatives to temperature -50 to 90 degree Celsius, followed by fdtration,

(b) Adjusting pH of oil-immiscible solvent stream rich in Benzoic- acid and its derivatives from alkaline pH between 7 to 14 to acidic pH between 0.001 to 7, followed by filtration,

(c) Evaporating the oil-immiscible solvent stream rich in Benzoic- acid and its derivatives at temperature between 0 to 150 degree Celsius in presence or absence of applied vacuum upto 0.1 bar,

(d) Extracting the Benzoic-acid and its derivatives from the oil- immiscible solvent.

5. The clog -free condensation process as claimed in claim 1, wherein oil- immiscible solvent is selected from water, alkali water having pH between 7 to 14 or mixture thereof.

6. The clog-free condensation process as claimed in claim 5, wherein alkali water is selected from solution of sodium hydroxide, potassium hydroxide, Calcium hydroxide, ammonia and ammonium hydroxide to produce alkaline salts of Benzoic-acid and its derivatives.

7. The clog-free condensation process as claimed in claim 4, wherein step (b) acidic solution selected from solution of Phosphoric Acid, Sulphuric Acid, Nitric Acid, Acetic Acid, Perchloric Acid, Citric Acid, Hydrochloric Acid, Formic acid and phosphorus Acid.

8. The clog -free condensation process as claimed in claim 1, wherein the oil- immiscible solvent stream rich in Benzoic-acid and its derivatives of step iii) is subjected to oxidative reaction, by reacting Benzoic-acid and its derivatives with oxygen to produce phenols.