Marketed under the trade name Thermocol, expanded polystyrene (EPS) consists of 90–95% polystyrene and 5–10% gaseous blowing agent, such as carbon dioxide or pentane. This polymer is highly consumed because of its many applications across several industries, especially packaging. Owing to its large volume and lack of biodegradability, it makes up a significant portion of the waste stream from municipalities. Long-chain polymer molecules are broken down into small-chain molecules by the pyrolysis process, which requires heat energy. Smaller molecules can be produced by adjusting the reaction's pressure and heat flow. Converting waste plastic into fuel is the most environmentally beneficial way to safeguard the environment since it recovers the organic component of polymeric waste in the form of valuable petroleum products. A study was conducted on dolomite, which is commercially available, and two different nanocatalysts, CaO:MgO and ZnO:CaO:MgO, synthesized in the laboratory. The use of these synthesized nanocatalysts resulted in an increased yield of the oil product than dolomite is used as a catalyst in pyrolysis.
Article
Recycling of polystyrene waste (thermocol) using pyrolysis with nano catalyst process into valuable product like fuel.
https://doi.org/10.21203/rs.3.rs-5219550/v1
This work is licensed under a CC BY 4.0 License
You are reading this latest preprint version
Polystyrene
Pyrolysis
Plastic to fuel
Nanocatalyst
waste to energy
Thermoplastic polymer is generated from styrene monomer, which yields polystyrene, a synthetic polymer referred to as thermocol. It serves as insulation against heat. Products like TVs, PCs, glass goods, etc. are protected by it. thermocol used in a variety of sectors. Because of its high density, manufacturers in the medical and refrigeration sectors rely extensively on it. It can be used in a variety of ways, like packing delicate objects or insulating building floors, walls, and roofs. Placing your worthless thermocol will surely result in its disposal in a landfill. This material is light and flows across space with such ease. It is bad for our health as well as the environment. When thermocol material is inappropriately disposed of, it ends up in our waterways. It is extremely dangerous and should never come into contact with food or water since it might contaminate them with chemicals. As such, do not use this material to package food products. Because thermocol is resistant to photolysis, it cannot be biodegraded. Therefore, thermocol is burned to minimize waste; yet, burning thermocol has greater negative effects on the environment than simply leaving it lying around. Upon Burning thermocol releases harmful chemicals that contribute to greenhouse emissions, such as carbon monoxide and styrene vapors. This makes burning thermocol very risky. The lack of oxygen during the pyrolysis process prevents the production of dioxins, so it is not necessary. Cleanup of flue gas1. Plastic pyrolysis has advantages for the environment, the economy, and operations 2.An excellent substitute method for recycling thermocol (polystyrene) waste that yields useful products like fuel is pyrolysis, which is done with the use of a catalyst. Pyrolysis will be used to create alternative fuels from various types of plastic trash, which will effectively address the issue of the world's increasing energy demand and the depletion of oil resources 3.According to research, waste thermocol between 3500C and 5500C might be converted into value-added liquid products by a straightforward batch pyrolysis process employing kaolin clay and silica alumina catalysts. Temperature, kind, and quantity of catalyst all had an impact on the reaction. When pyrolysing various plastics, the use of 5–10% dolomite as a catalyst increased the concentration of low molecular weight components in liquid fuel, raising the fuel's calorific value4.By means of his patent,3 proved that dolomite catalyst may be used between 330 and 400 °C. The resultant liquid is put through a semi-batch reactor's catalytic cracking reaction, which produces better-quality fuel, mostly light and heavy naphtha5. Therefore, in order to verify its efficiency, our synthetic catalyst was compared to dolomite.
Plastic undergoes pyrolysis to produce products that are used as fuel. The three methods of pyrolysis are thermal pyrolysis, catalytic pyrolysis, and hydrocracking.
2.1 Hydrocracking: is the process by which big polymer molecules break down into smaller hydrocarbon molecules in the presence of hydrogen, which can be used as an energy source6. The reaction involves hydrogen over a catalyst, and a batch stirred reactor is usually employed in the range of 1500C to 4000C with hydrogen pressures between 3 and 10 mPa.
2.2 Thermal Pyrolysis or non-catalytic Pyrolysis: is the process that uses heat energy and anaerobic conditions to break down plastic at greater temperatures, between 3500 to 9000 Celsius 7. The endothermic process of thermal pyrolysis breaks down plastic polymers such as PS, PP, and polyethylene, among others, at extremely high temperatures. The liquid byproduct of thermal pyrolysis requires additional refinement in order to get an octane/cetane rating and be suitable for use as motor engine oil. The production of gaseous products rises with temperature, whereas the yield of liquid fuel falls4. The pyrolytic fraction's dependence on temperature and residence time was investigated; the results indicate that temperature has a significant impact on the synthesis of methane and benzene and that tar formation is increased with longer residence times 8. In order to get around issues with thermal pyrolysis, catalytic pyrolysis is a key concept.
2.3 Catalytic Pyrolysis: Catalysts are substances that alter a chemical reaction's rate without undergoing any changes or being consumed throughout the process, and they also don't alter the system's overall thermodynamics9. Utilizing catalysts to pyrolyse plastic waste in order to produce the most yield in the quickest reaction time is known as catalytic pyrolysis.
Reducing the products' carbon chain length and, consequently, their boiling point is one of the primary goals of catalytic pyrolysis. In the process of catalytic pyrolysis, the activation energy is lowered by the catalyst's inclusion, greatly cutting down on the amount of time and temperature needed to complete the reaction. The introduction of catalysts increases the conversion rate of a wide range of polymers at significantly lower temperatures when compared to non-catalytic thermal pyrolysis. Different types of catalysts are used to improve the overall pyrolysis of plastic waste and to increase process efficiency 10.
2.4 Catalyst: Catalysts are essential for reducing reaction temperatures and times in order to target specific reactions and increase reaction efficiency. Various types of catalysts are applied to enhance the plastic waste pyrolysis process. While many other catalysts have been utilized in plastic pyrolysis processes, dolomite, bentonite clay, ZSM-5, zeolite, Y-zeolite, FCC, and MCM-41 are the most commonly used catalysts 9.In one study, the pyrolysis of various polymers using 5–10% dolomite as a catalyst increased the concentration of low molecular weight components in liquid fuel, raising the fuel's calorific value3.Dolomite is a kind of limestone that contains a lot of calcium and magnesium carbonates in addition to other minerals11. We have utilized commercially available dolomite, which is successful in pyrolysis, to create two nanocatalysts in the lab: one constituted of calcium and magnesium, and the other of zinc, calcium, and magnesium for comparison12.
3.1 Preparation of Nanocatalyst:
3.1.1 CaO: MgO (1:1) nanoparticles: To synthesize CaO: MgO (1:1) nanoparticles, begin by dissolving 10 grams of MgSO₄ and 5.9 grams of Ca(NO₃)₂ in 200 milliliters of water, ensuring thorough mixing with constant stirring. Then, add 200 milliliters of 1N NaOH to the solution, which will result in the formation of a precipitate. Collect the precipitate and mix it with 8 grams of a 50% fuel solution. Calcinate the mixture at 500°C for 10 minutes. This process yields CaO:MgO(1:1) nanoparticles.
3.1.2 ZnO: CaO: MgO (1:1:1) nanoparticles: To synthesize ZnO:CaO:MgO nanoparticles, start by dissolving 4.5 grams of Zn(NO₃)₂, 10 grams of MgSO₄, and 5.9 grams of Ca(NO₃)₂ in 250 milliliters of water, mixing thoroughly with constant stirring. Then, add 250 milliliters of 1N NaOH to the solution, leading to the formation of a precipitate. Collect the precipitate and mix it with 10 grams of a 50% fuel solution. Calcinate the mixture at 500°C for 10 minutes. This process results in the formation of ZnO: CaO:MgO nanoparticles. The Catalyst composition was confirmed from powder X-ray diffraction as shown in Figure 3 and 4 and matches with slandered JCPDS files of calcium and magnesium oxide nanoparticles.
3.1.3 Dolomite AR Grade is used for Experimentation.
3.2 Material Used:
Polystyrene (Thermoplastic Waste): In this Experiment we select the thermocol for pyrolysis. The thermocol was collected and making it suitable for pyrolysis by breaking it into small pieces.
Structure of Polystyrene:
3.3 Experimental Procedure:
Plastic waste of polystyrene (thermocol) was cleaned and chopped. 50 grams of Plastic waste along with 50 mg of dolomite/nanocatalyst as catalyst for catalytic degradation. Nitrogen gas was purged into the reactor to push the oxygen out of the reactor. Pyrolysis was carried out at 4500C for 60 min. A pyrolysis apparatus arrangement is made inside the chemical fume hood as per laboratory set up in Figure 1, which provides a ventilated enclosure used to trap and exhaust vapors and gases. As the pyrolysis process requires continued circulation of water for condensation arrangement, it circulates water without wastage, and reaction requirements of water are also fulfilled. A fraction of fuel/wax was collected, and further analysis of it is carried out according to the physiochemical properties of petroleum fuel in Figure 2.
Catalysts characterization:
Part 1: 50 grams of PS Plastic waste along with 50mg of dolomite as catalyst for catalytic degradation is added into pyrolysis flask. Pyrolysis was carried out upto 4500C for 60 minutes. On Catalytic degradation with dolomite 25ml (50% w/v) of fuel fraction was collected which is clear brown colored liquid fraction.
Part 2 : 50 grams of PS Plastic waste along with 50 mg of Nano CaO:MgO as catalyst for catalytic degradation is added into pyrolysis flask. Pyrolysis was carried out upto 4500C for 60 minutes. On Catalytic degradation with dolomite 35 ml (70% w/v) of fuel fraction was collected which is clear brown colored liquid fraction. Temperature required for the reaction was also decreased as the reaction was completed in 45 min and the maximum amount of product is collected upto the 3800C.
Part 3 : 50 grams of PS Plastic waste along with 50 mg of Nano ZnO:CaO:MgO as catalyst for catalytic degradation is added into pyrolysis flask. Pyrolysis was carried out upto 4500C for 60 minutes. On Catalytic degradation with dolomite 41 ml (82% w/v) of fuel fraction was collected which is clear brown colored liquid fraction. Temperature required for the reaction was also decreased as the reaction was completed in 45 min and the maximum amount of product is collected up to the 3800C as shown in Table 1 and Figure 5.
Table 1:Results
|
Sr. No. |
Material (PS) weight (gm) |
Catalyst Weight (gm) |
Density (gm/ml) |
Yield (W/V) |
Yield W/W |
Time required (minutes ) |
Reaction Temperature |
|
1 |
50 Gm |
Dolomite 50mg |
0.872 |
50% (25 ml) |
43.60% (21.80 gm) |
60 |
2100C - 4500C |
|
2 |
50 gm |
Nano Catalyst CaO: MgO 50mg |
0.895 |
70% (35 ml) |
62.66 % (31.33 gm) |
45 |
2100C -3800C |
|
3 |
50 gm |
Nano Catalyst ZnO:CaO:MgO 50mg |
0.881 |
82% (41 ml) |
72.42% (36.12 gm)
|
45 |
2100C -3800C |
Analysis of Liquid Fuel samples :The collected liquid samples were subjected to physical parameter analysis using standard ASTM fuel test procedures13. Open cup flash and fire point apparatus are used to determine fire point and flash point as shown in Table 2. Rico Scientific Industries was used to calculate the samples' gross calorific values (Model: RSB 7.6) Bomb Calorimeter. Identification of compounds present in the oil samples was made using GC-HR Mass Spectrometer JEOL AccuTOF GCV. Results are compared with the standard diesel values (Figure No.6-8).
Table 2:Results Comparison of the physical parameters of thermal and catalytic derived liquid fractions with diesel oil
|
Sr. No. |
Fuels Parameters |
Dolomite |
CaO: MgO |
ZnOCaO MgO |
Diesel ( Standard) |
|
1 |
Density ( gm/ml) |
0.872 |
0.895 |
0.881 |
0.82 - 0.88 |
|
2 |
Flash Point 0C |
880C |
870C |
850C |
520C -960C |
|
3 |
Fire Point 0C |
930C |
940C |
900C |
+ 10 0C |
|
4 |
Calorific Values MJ/kg |
47.9 MJ/kg |
46.8 MJ/kg |
46.5 MJ/kg |
45.5 MJ/kg |
GCMS Analysis: In study with Gas Chromatography shows presence of hydrocarbons in the range of C12 – C24 with polystyrene waste samples using dolomite, CaO:MgO nanocatalyst while hydrocarbons in the range of C10 – C15 using ZnO:MgO:CaO nanocatalyst. In Pyrolysis.Major components of oil obtained using dolomite are benzene, N- benzylbenzamide, 1,5 diphenyl 1,5 hexadiene, Acetic acid, N Benzyl, Pyridine 4 etc, using CaO:MgO nanocatalyst are 1- octanol 2 Butyl, 6 Tridecene , Pyridine 4, Benzene 1,1 bis, Benzenemethamine, Tricarbabimic acid, Tetracyclo -4 ene Phenyl etc. while using oil obtained using ZnO:MgO:CaO as catalyst shows Major component benzene it shows specific targeted hydrocarbon range between C10 – C15 which gives oil in pure form.
1. Expanded polystyrene (EPS), sometimes referred to as thermocol, is the most widely used polymer because of its numerous applications in various industries, most notably packaging. So to reduce the waste produced after using this type of material, pyrolysis can be beneficial as we are getting valuable products like fuel.
2. Using nanocatalysts such as CaO: MgO and ZnO:MgO:CaO, the reaction time is reduced by around 15 minutes, and the yield of oil product is increased by 20% and 32.5%, respectively. Additionally, nanocatalysts reduce the reaction temperature by 70 °C, making them more effective than dolomite, which was previously used as a catalyst. According to GCMS analysis using nanocatalysts, hydrocarbons are in the range of C10 – C15.
3. The comparison of fuel product obtained after pyrolysis with the standard values of Physical parameters such as Density, Flash and Fire point and Calorific values are shown similarity so fuel obtained can be use as diesel.
Data Availability Statement: The datasets used and/or analysed during the current study available from the corresponding author on reasonable request"
Contributions:
SW conceived and supervised the study. PKG and PC performed the experiments.SDG and PKG performed the data analyses. PC contributed to the data analyses. PKG and SW wrote the manuscript. All authors read and approved the final manuscript.
Ethics declarations
Competing interests
The authors declare no competing interests.
Author Contribution
Pradnya has done actual practical work , pyrolysis was carried by Priyanka. Shobha and Sharda have done interpretation and writing
Acknowledgement:
The authors would like to express their gratitude to COEP Tech University and MES Abasaheb Garware College for providing the necessary facilities for this research.
Author Informations:
Data Availability
Data Availability is with corresponding author and first author
- Fodor, Z. & Klemeš, J. J. Waste as alternative fuel – Minimising emissions and effluents by advanced design. Process Saf. Environ. Prot.90, 263–284 (2012).
- Al-Salem, S. M., Lettieri, P. & Baeyens, J. Recycling and recovery routes of plastic solid waste (PSW): A review. Waste Management vol. 29 at https://doi.org/10.1016/j.wasman.2009.06.004 (2009).
- Sonawane, Y. B., Shindikar, M. R. & Khaladkar, M. Y. High Calorific Value Fuel from Household Plastic Waste by Catalytic Pyrolysis. Nat. Environ. Pollut. Technol.16, 879–882 (2017).
- Panda, A. K., Singh, R. K. & Mishra, D. K. Thermolysis of waste plastics to liquid fuel. A suitable method for plastic waste management and manufacture of value added products-A world prospective. Renewable and Sustainable Energy Reviews vol. 14 233–248 at https://doi.org/10.1016/j.rser.2009.07.005 (2010).
- Lee, K. H. & Shin, D. H. Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: Influence of lapse time of reaction. Waste Manag.27, 168–176 (2007).
- Budsaereechai, S., Hunt, A. J. & Ngernyen, Y. Catalytic pyrolysis of plastic waste for the production of liquid fuels for engines. RSC Adv.9, 5844–5857 (2019).
- Vasile, C. & Brebu, M. A. REVIEW THERMAL VALORISATION OF BIOMASS AND OF SYNTHETIC POLYMER WASTE. UPGRADING OF PYROLYSIS OILS. CELLULOSE CHEMISTRY AND TECHNOLOGY Cellulose Chem. Technol vol. 40 (2006).
- Kaminsky, W. & Kim, J.-S. Pyrolysis of mixed plastics into aromatics. Journal of Analytical and Applied Pyrolysis vol. 51 (1999).
- Ratnasari, D. K., Nahil, M. A. & Williams, P. T. Catalytic pyrolysis of waste plastics using staged catalysis for production of gasoline range hydrocarbon oils. J. Anal. Appl. Pyrolysis124, 631–637 (2017).
- Abbas-Abadi, M. S., Haghighi, M. N. & Yeganeh, H. The effect of temperature, catalyst, different carrier gases and stirrer on the produced transportation hydrocarbons of LLDPE degradation in a stirred reactor. J. Anal. Appl. Pyrolysis95, 198–204 (2012).
- Papuga, S., Djurdjevic, M., Ciccioli, A. & Vecchio Ciprioti, S. Catalytic Pyrolysis of Plastic Waste and Molecular Symmetry Effects: A Review. Symmetry (Basel).15, (2023).
- Wang, C., Han, H., Wu, Y. & Astruc, D. Nanocatalyzed upcycling of the plastic wastes for a circular economy. Coord. Chem. Rev.458, 214422 (2022).
- Ahmadvand, M. S., Askari, S. & Sharifi, K. Synthesis and performance of ZSM-5 and HZSM-5 in desulfurization of naphtha. Int. J. Environ. Sci. Technol.17, 3541–3548 (2020).
No competing interests reported.