Catalytic pyrolysis of polystyrene into aromatic rich liquid product using spherical catalyst

Patent metadata

Field	Value
Publication number	US-11613623-B2
Application number	US-202117481050-A
Country	US
Kind code	B2
Filing date	Sep 21, 2021
Priority date	Sep 21, 2020
Publication date	Mar 28, 2023
Grant date	Mar 28, 2023

Abstract

The present invention provides a process of catalytic depolymerization of polystyrene involving a spherical catalyst, an apparatus for carrying out the depolymerization, recovering the aromatic rich liquid product and recycling the catalyst without any decrease in the catalytic performance. Further, the present invention provides that the aromatic rich liquid product includes styrene, xylene, benzene, ethyl benzene, with styrene content greater than 65%. Additionally, the catalyst involved in the depolymerization process is a spherical catalyst that is easily recovered from coke/char formed during the process and is recycled and reused without any decrease in the catalytic performance.

First claim

The invention claimed is:

1. A process of catalytic depolymerization of polystyrene, the process comprising:
(a) adding a polystyrene feed and a catalyst into a reactor, wherein the catalyst and the feed are added together, or the feed is added first followed by the catalyst, or the feed is added into the reactor containing the catalyst; wherein the catalyst is a spherical catalyst;
(b) mixing the feed with the catalyst in the reactor to obtain a mixture and heating the mixture at a rate ranging from 3 to 20° C./min in an inert atmosphere for generating a vapor;
(c) passing the vapor from the reactor to a condenser to obtain a condensate, wherein a heating tape is connected to a temperature controller to prevent condensation of the vapor before entering the condenser; and
(d) routing the condensate from the condenser to a liquid product collection flask to collect a liquid product, and passing non-condensable gases from the condenser through a scrubber;
wherein the liquid product is present in an amount ranging from 85% to 90% by weight of a total weight of a solid, a liquid and a gas exiting the reactor, and wherein the liquid product comprises styrene in an amount ranging from 65% to 71% by weight of the liquid product.

2. The process as claimed in claim 1 , wherein the feed is a styrene rich polymer waste comprising styrene in an amount ranging from 20% to 100% by weight, wherein the styrene rich polymer is selected from the group consisting of acrylonitrile butadiene styrene (ABS), styrene-butadiene (SBS) rubber, styrene-butadiene latex, styrene-isoprene-styrene (SIS), styrene-ethylene/butylenes-styrene (S-EB-S), styrenedivinylbenzene (S-DVB), styrene-acrylonitrile resin (SAN), unsaturated polyesters, and mixtures thereof.

3. The process as claimed in claim 1 , wherein the feed is compressed, shredded, or densified before addition to the reactor.

4. The process as claimed in claim 1 , wherein the heating in step (b) for depolymerization of the feed is carried out at a temperature ranging from 350° C. to 500° C.

5. The process as claimed in claim 1 , wherein the spherical catalyst is selected from the group consisting of alumina-silica and oxides of silicon, aluminum, zinc, magnesium, barium, osmium, manganese, iron, titanium, and mixtures thereof.

6. The process as claimed in claim 5 , wherein the spherical catalyst is supported on a substrate inside the reactor and the feed is introduced over the substrate.

7. The process as claimed in claim 1 , wherein coke produced during depolymerization is removed from the spherical catalyst and the spherical catalyst is reactivated in the reactor without decrease in catalytic performance.

8. The process as claimed in claim 1 , wherein the reactor is cylindrical or tubular and is selected from a fixed-bed reactor, a stirred-tank reactor, a microwave reactor, a fluidized-bed reactor, a conical spouted bed reactor (CSBR), a rotary kiln reactor, and a screw extruder (Auger) reactor.

9. The process as claimed in claim 1 , wherein mixing the feed with the catalyst comprises mixing 0.1 to 10 wt % of the catalyst based on a weight of the feed.

10. The process as claimed in claim 1 , wherein, the feed is dissolved in an organic solvent selected from the group consisting of toluene, xylenes, cymenes, and terpinenes, wherein the solvent is recycled after depolymerization.

11. The process as claimed in claim 1 , wherein conversion rate of the process using the spherical catalyst ranges between 50 and 100%.

12. An apparatus for depolymerization of polystyrene, the apparatus comprising:
(a) a stainless steel cylindrical or tubular reactor equipped with a mass flow meter to control the flow of an inert gas, wherein the stainless steel cylindrical or tubular reactor is configured to polystyrene feed and a spherical catalyst;
(b) a split type single zone electrical furnace with a programmable digital temperature controller for heating the reactor using an electrical or a thermal fluid system, wherein the reactor is heated at a rate ranging from 3 to 20° C./min;
(c) a K-type thermocouple connected to the programmable digital temperature controller to measure a temperature of the reactor;
(d) an opening provided at a top of the reactor for routing vapors generated in the reactor during depolymerization of the polystyrene feed into a condenser;
(e) a heating tape connected to the programmable digital temperature controller to prevent condensation of the vapors before entering the condenser;
(f) a chiller connected to the condenser for maintaining a temperature of the condenser;
(g) a liquid product collection flask for collecting a condensate from the condenser, wherein the condensate is a liquid product and is present in an amount ranging from 85% to 90% by weight of a total weight of a solid, a liquid and a gas exiting the reactor, and wherein the liquid product comprises styrene in an amount ranging from 65% to 71% by weight of the liquid product; and
(h) a scrubber for passing un-condensable gases from the condenser.

13. The apparatus as claimed in claim 12 , wherein the reactor is a fixed-bed reactor, a stirred-tank reactor, a microwave reactor, a fluidized-bed reactor, a conical spouted bed reactor (CSBR), a rotary kiln reactor, or a screw extruder (Auger) reactor.

14. The apparatus as claimed in claim 12 , wherein the reactor comprises a spacer tube, a static mixer, or an annular insert.

15. The apparatus as claimed in claim 14 , wherein the static mixer, or the annular insert is removable.

Assignees

• Indian Oil Corp Ltd

Inventors

• Kanattukara Bineesh Vijayan
• Singh Gurmeet
• Singh Dheer
• Kapur Gurpreet Singh
• RAMAKUMAR Sankara Sri Venkata

Classifications

• B01J35/51

  Spheres · CPC title

• C10G2400/30

  Aromatics · CPC title

• B01J29/40

  of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively · CPC title

• C07C4/22

  by depolymerisation to the original monomer, e.g. dicyclopentadiene to cyclopentadiene · CPC title

• C08J11/16 Primary

  by treatment with inorganic material (C08J11/14 takes precedence) · CPC title