WO2021209276A1

WO2021209276A1 - Pyrolysis process to obtain petrochemical products from plastic waste

Info

Publication number: WO2021209276A1
Application number: PCT/EP2021/058825
Authority: WO
Inventors: Nagore ANDRAKA RUEDA; Carlos URAGA PASTOR; Mikel AZCONA CALERO
Original assignee: Nantek Hub S.L.
Priority date: 2020-04-17
Filing date: 2021-04-05
Publication date: 2021-10-21

Abstract

The present invention provides a pyrolysis process to obtain petrochemical products from plastic waste, particularly based on the use of nanoparticle carbon-based reagents, instead of using catalysts, whereby lower temperature, pressure and energy are used to achieve better results. The process of the present invention works directly with air and comprising the steps of: i) adding a feedstock of plastic waste without any other product coming from petroleum together with nanoparticle carbon-based reagents to a pyrolysis reactor; ii) increasing the reactor temperature for a thermal decomposition to a maximum of 400ºC and a pressure between 1-20 bar; iii) separating in a fractionating column the different fractions of the gases generated; iv) cooling the gas fractions in a condenser; and v) extracting the resulting liquid fraction. The resulting liquid fraction includes petrochemical products such as pyrolysis oils, fuels, paraffins or naphthas.

Description

PYROLYSIS PROCESS TO OBTAIN PETROCHEMICAL PRODUCTS FROM PLASTIC

WASTE

DESCRIPTION

FIELD OF THE INVENTION

The field of the invention relates to obtaining oil and synthetic fuels from plastic waste and residues, more specifically, relates to a process for converting plastic waste into petrochemical products by pyrolysis in the absence of catalysts.

BACKGROUND ART

Around six trillion tons of plastic waste have been generated worldwide in the last 50 years. It has been observed that 90% of the waste accumulated by the municipal corporation is a plastic waste. This garbage is recycled, however about 80 percent of it sits in landfills or in the natural environment, where it damages wildlife, filters out harmful chemicals, and emits harmful gases.

Therefore, there is a need for increased recycling of this type of waste. The three main purposes of recycled plastic are direct reuse, use as a raw material for the manufacture of new products and its conversion as fuel or as new chemical products.

Processes for treating plastic waste to obtain fuels and other value-added chemicals are known in the state of the art.

WO2013187787 discloses a continuous process of pyrolysis of plastic waste and/or rubber waste and/or organic waste, comprising subjecting these components to a thermal decomposition in the pyrolytic reactor without any access to air, at a temperature of 200 to 850°C, under atmospheric pressure or elevated pressure or reduced pressure, characterized in that, into the pyrolytic reactor chamber, a composition of chemical modifier is dosed, which comprises 10 to 30% by weight of water, 20 to 80% by weight of at least one aliphatic alcohol, 5 to 15% by weight of carbamide or its derivatives, and 5 to 15% by weight of monoacetylferrocene, wherein this composition, prior to dispensing into the reactor, is additionally diluted with water, so that after dilution, it contains from about 5% by weight of composition and 95% by weight of water to 15% by weight of composition, and 85% of water. W02014040634A1 proposes a method and apparatus for recycling plastic wastes. Plastic wastes which for at least 80 wt% contain a polymer or a mixture of polymers from a group including polymethyl methacrylate, polypropylene, polyethylene, polystyrene, polyethylene terephthalate and/or polytetrafluoroethylene, are recycled using the following steps: (i) heating the plastic wastes to a temperature at which they are flowable; (ii) pyrolyzing the flowable plastics together with a catalyst and/or an adsorber and withdrawing the resulting gases; (iii) condensing the gases. The catalyst used was a zeolite and the adsorbent consist of calcium oxide and / or magnesium oxide.

WO2015128033A1 relates to a process for converting mixed waste plastic (MWP) into valuable petrochemicals, comprising feeding mixed waste plastic (MWP) to a pyrolysis reactor, converting said MWP into a gaseous stream and a liquid stream, and further processing said gaseous stream into valuable petrochemicals, said process further comprising the steps of: i) feeding said liquid stream, together with a hydrocracker feed, to a hydrocracking unit; ii) converting said liquid stream, together with said hydrocracker feed, through hydrocracking into at least one gaseous stream and a liquid stream: iii) further processing said at least one gaseous stream into valuable petrochemicals. In this process, hydrocracking catalysts are used, which are commercially available hydrocracking catalysts such as Co-Mo / Ni-Mo on alumina, among others.

W02017103010A1 discloses a process for converting waste plastic into gases, liquid fuels and waxes by catalytic cracking. The process comprises the steps of introducing waste plastic and a catalyst within a reactor; allowing at least a portion of the waste plastic to be converted to gases, liquid fuels and waxes within the reactor; and removing a product stream containing said gases, liquid fuels and waxes from the reactor. The process uses a zeolite-type catalyst and/or an amorphous-type catalyst (silica, alumina, kaolin or a mixture).

US2005032920A1 describes a process and apparatus for producing a synthesis gas for use as a gaseous fuel or as feed into a Fischer-Tropsch reactor to produce a liquid fuel in a substantially self-sustaining process. In one embodiment, a slurry of particles of carbonaceous material in water, and hydrogen from an internal source, are fed into a hydro-gasification reactor under conditions whereby methane rich producer gases are generated and fed into a steam pyrolytic reformer under conditions whereby synthesis gas comprising hydrogen and carbon monoxide are generated. A portion of the hydrogen generated by the steam pyrolytic reformer is fed through a hydrogen purification filter into the hydrogasification reactor, the hydrogen therefrom constituting the hydrogen from an internal source. The remaining synthesis gas generated by the steam pyrolytic reformer is either used as fuel for a gaseous fueled engine to produce electricity and/or process heat or is fed into a Fischer-Tropsch reactor under conditions whereby a liquid fuel is produced. Molten salt loops are used to transfer heat from the hydro-gasification reactor, and Fischer-Tropsch reactor if liquid fuel is produced, to the steam generator and the steam pyrolytic reformer. In another embodiment of the invention, carbonaceous material can be heated simultaneously in the presence of both hydrogen and steam to undergo steam pyrolysis and hydrogasification in a single step.

US2005032920A1 is focused on obtaining the compounds that act as reagents for a Fischer- Tropsch system (CO and H2), that make possible obtaining fuel in a second step (or in one step in the presence of both hydrogen and steam to undergo steam pyrolysis and hydro gasification). However, although carbon-based reagents are used, the reactions that take place, the process and the starting materials are different from the present invention. Particularly, in the present invention, hydrogen from an internal source is not required as a reagent. Furthermore, an initial stage in a hydrogasification reactor to obtain fuel is not necessary.

JPH08337782 describes the conversion of a heavy oil into a light oil, reutilizing waste plastics without hydrogen and catalyst by mixing a heavy oil with waste plastics and heat-treating the mixture at a specific temperature in a non-oxidizing atmosphere. The process consists of the addition of a heavy oil consisting of a petroleum-based heavy oil or a coal-based heavy oil mixed with plastic waste and the mixture is heat-treated at 350-460°C in a non-oxidizing atmosphere such as nitrogen, argon, helium or hydrocarbon gas. The heat-treatment is carried out under a pressure between atmospheric pressure and 50 atm for 10-40 min. After separation and cooling of the gases, the resulting liquid phase is obtained.

In the method described in JPH08337782, catalyst addition is not necessary. However, not totally exclude the addition of a catalyst. Catalyst can be added to promote the decomposition and reaction in the heat treatment. For example: silica, alumina catalysts, transition metal- based catalysts, noble metal catalyst, metal compound or natural minerals.

Furthermore, the raw materials include a heavy oil consisting of a petroleum-based heavy oil or a coal-based heavy oil, not only plastic waste. In contrast, the present invention uses pure plastics, without their dilution with oils, or other products coming from petroleum. The present invention works directly using a feedstock of plastic waste, without any other product coming from petroleum (such as oil, naphtha, paraffin...). This is an improvement since it is not necessary to collect oil (naphtha, paraffin...), which currently follows its own recycling process and has a high value on the market compared to plastic waste.

Furthermore, in the present invention it is not necessary to use non-oxidizing atmospheres, since the process of the present invention works directly with air. It reduces the process cost and avoids the use of strategic gases such as helium or argon.

Despite the fact that there are a lot of processes, they involve the use of catalysts, which makes the process more expensive, can generate waste and also generates environmental damage from the use of the catalysts themselves. In addition, the processes are less efficient, since, apart from the cost associated with the catalysts, longer times and higher temperatures are required and lower yields are obtained.

SUMMARY OF INVENTION

The present invention discloses a process of pyrolysis, particularly based on the use of carbon nano-elements as reagents, instead of using catalysts, whereby lower temperature, pressure and energy are used to achieve better results. The process, after cracking the polymers, re builds monomer chains - using the carbon-based nanoparticles as reagents, obtaining fully functional liquids for the petroleum industry.

The process of the present invention is an advanced pyrolysis, since the energy required for the degradation of plastics or polymers in which the C-C and C-H bonds are broken is less than the required in the usual reactions, which translates into a lower reaction temperature. This has some advantages such as that the energy accumulated in the fuel obtained is greater than the necessary in the process and is a more economically pyrolysis process.

The present invention solves the problems that exist in the state of the art by means of an advanced pyrolysis process in which catalysts are not used to obtain high-quality fuels from plastic waste, which include polymers such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), polystyrene (PS), polyethylene (PET), nylon and polypropylene (PP), among others. It should be noted that, in the present invention, plastic waste does not need pre-treatment, thus constituting an advantage for recycling. In a first aspect of the invention, the present invention provides a pyrolysis process, that works directly with air, to obtain petrochemical products from plastic waste comprising the following steps: i) adding plastic waste without any other product coming from petroleum and nanoparticle carbon-based reagents with a size equal to or less than 250 nm to a pyrolysis reactor at room temperature and atmospheric pressure; ii) increasing the pyrolisis reactor temperature to a maximum of 400°C and a pressure between 1-20 bar for a thermal decomposition of the mixing of step 0; iii) separating of the gases generated in the reactor in a fractionating column obtaining different gas fractions; iv) cooling the gas fractions obtained in the step iii) in a condenser obtaining a liquid fraction; and v) extracting the resulting liquid fraction as the final product. and, the nanoparticle carbon-based reagents are selected from the group comprising graphene, carbon black, synthetic nanoparticles of graphite (flakes, spherical and/or irregularly shaped), monolayer graphite, multilayer graphite (less than 20 layers), carbon nanotubes, carbon nanowires, spherical carbon nanoparticles, fullerenes, activated fullerenes or combinations thereof.

The pyrolysis process of the present invention achieves yields greater than 80% of the liquid fraction. The resulting liquid fraction includes petrochemical products such as pyrolysis oils, fuels, paraffins or naphthas.

The waste plastic and the carbon-based reagents can be introduced within the reactor simultaneously or subsequently.

In the reactor, the mixed waste plastic is converted to gases and liquid fuels. The plastic waste is gasified and the gas obtained rises to the top of the reactor. This conversion (step ii)) preferably takes place at a temperature of equal to or less than 400°C. Preferably, the conversion takes place at a temperature in the range of 50-400°C, more preferably in the range of 120 to 350°C. The temperature increases in the reactor (step ii)) can be carried out directly or by a 1 , 2, 3 or 4 step process with stationary temperatures at 70-110 °C, 120-210 °C, 220-280 °C and 300- 400 °C respectively.

In the present invention, thermal decomposition (step ii)) is carried out at low temperature (<400°C, preferably between 50-400°C) and at controlled pressure (1-20 bar, preferably between 1-16 bar). These optimized reaction conditions allow a controlled polymeric degradation in which there is a rearrangement of the atoms that permits to control the size of the final compounds obtained using carbon-based reagents that are integrated into the reaction products without generating additional residues.

Typically, the decrease in reaction temperature is achieved through the use of catalysts, but it supposes an additional cost for the process and an environmental problem since these catalysts include metals that can be heavy or toxic. In addition, there is the problem of recovering and / or treating them once their useful life has ended and they remain together with the solid waste.

In the present invention, the use of catalysts is avoided, which reduces the cost of the whole process itself and avoids environmental pollution due to the disuse of metals in the process. Instead of catalysts, nanoparticle carbon-based reagents are used.

The nanoparticle carbon-based reagents have a size equal to or less than 250 nm in one or more of its axes, preferably a size equal to or less than 150 nm in one or more of its axes.

The nanoparticle carbon-based reagents have a very large specific surface, which represents a very large active surface. Due to this, the interaction between the intermediate products of the gas and liquid fractions is higher in the presence of nanoparticle carbon-based reagents. The reaction is activated as it would in the presence of a catalyst. However, unlike catalysts, these nanoparticle carbon-based reagents are integrated into the final product. In the present invention, during steps ii) and iii), the nanoparticle carbon-based reagents are integrated into the final products without leaving additional residues and controlling the size of the final compounds obtained.

Therefore, the use of said nanoparticle carbon-based reagents in the process of the present invention allows using lower temperature ranges than those described in the state of the art and obtaining higher liquid fraction yields. Additionally, the nanoparticles act as a source of carbon, modifying the Carbon-Oxygen- Hydrogen balance in the process and promoting the formation of the liquid fraction, which is of greatest interest from an economic point of view. Therefore, the use of these nanoparticles leads to a reduction in the energy required to carry out the reaction and an optimization of the process.

In summary, the use of the nanoparticles has several advantages such as the absence of additional solid residues, optimization of the process, environmentally friendly (absence of metals), and a low cost (compared to catalysts).

DESCRIPTION OF EMBODIMENTS

Example 1. Pyrolysis process to obtain petrochemical products from plastic waste

The skilled person is aware of suitable apparatus and equipment for carrying out the process in accordance with the present invention and will select the suitable system based on his professional experience, so that no further extensive details need to be given here. The experiment was carried out following the general procedure described here.

In a first step, 200 g of plastic waste having a composition of 25-30% by weight of PET, 55-65 % by weight of PE (LDPE and HDPE mixed), < 10 % impurities and humidity and approximately 0,1 g nanoparticle carbon-based reagents were added to a pyrolysis reactor. The addition was carried out at room temperature and atmospheric pressure.

In a second step, the temperature of the reactor was increased up to 300°C and the pressure was fixed below 16 bar, producing a thermal decomposition of the mixture of the plastic waste and the nanoparticles carbon-based reagents.

In this example, the temperature increases in the reactor were carried out by a 3-step process with stationary temperatures at 90 °C, 170 °C and 300°C.

In a third step, the different fractions of the gases generated into a fractionating column were separated. Attached to this fractionating column there was placed a condenser.

Finally, the gases were cooled in the condenser and the resulting liquid fraction was stored. Taking as a reference value the initial plastic waste fraction, by this process, 90% by weight of the liquid fraction (including valuable compounds such as pyrolysis oil, fuels, paraffins or naphthas), 3% by weight of the non-condensable gaseous fraction and 7% by weight of the solid waste were obtained.

Claims

1. Pyrolysis process to obtain petrochemical products from plastic waste, characterized by the process works directly with air and comprising the following steps: i) adding a feedstock of plastic waste without any other product coming from petroleum and nanoparticle carbon-based reagents with a size equal to or less than 250 nm in one or more of its axes to a pyrolysis reactor at room temperature and atmospheric pressure; ii) increasing the pyrolysis reactor temperature to a maximum of 400°C and a pressure between 1-20 bar for a thermal decomposition of the mixing of step i); iii) separating the gases generated in the reactor in a fractionating column obtaining different gas fractions iv) cooling the gas fractions obtained in the step iii) in a condenser obtaining a liquid fraction; and v) extracting the resulting liquid fraction as the final product. wherein the nanoparticle carbon-based reagents are selected from the group comprising graphene, carbon black, synthetic nanoparticles of graphite, monolayer graphite, multilayer graphite, carbon nanotubes, carbon nanowires, spherical carbon nanoparticles, fullerenes, activated fullerenes or combinations thereof.

2. The pyrolysis process according to claim 1, wherein the nanoparticle carbon-based reagents have a size equal to or less than 150 nm in one or more of its axes.

3. Pyrolysis process according to any one of claims 1 to 2, wherein the temperature of step ii) is between 50-400°C.

4. Pyrolysis process according to any one of claims 1 to 2, wherein the temperature of step ii) is between 120-350°C.

5. Pyrolysis process according to any one of the preceding claims, wherein the pressure of step ii) is between 1-16 bar.