From laboratory scale to pilot plant: Evaluation of the catalytic co-pyrolysis of grape seeds and polystyrene wastes with CaO

Chemical recycling of plastic wastes with alkaline earth metal oxides: A review

Plastics have been widely used in daily life and industries due to their low cost and high durability, leading to huge production of plastics and tens of millions of plastic wastes every year. Chemical recycling can recycle contaminated and degraded plastics (that mechanical recycling cannot deal with) to obtain value-added products, which potentially solves the environmental problems caused by plastics and realizes a circular economy. Alkaline earth metal oxides, as a category of cost-effective and multi-functional materials, have been widely used in chemical recycling of common plastics, acting as three roles: catalyst, template, and absorbent. Among five commercial plastics, polyethylene terephthalate is suitable for pyrolysis and solvolysis. Polyethylene and polypropylene, which are ideal precursors for synthesis of carbon nanotubes, could be combined with biomass for co-pyrolysis. Polyvinyl chloride needs to be pretreated to reduce chloride content prior to pyrolysis. Depolymerization of polystyrene into monomers is attractive. This review summarized the chemical recycling approaches of commercial plastics and the strategies with alkaline earth metal oxides for the development of efficient recycling processes. It will aid understanding of the advances and challenges in the field and promote the future research.

A Thermo-Catalytic Pyrolysis of Polystyrene Waste Review: A Systematic, Statistical, and Bibliometric Approach

Global polystyrene (PS) production has been influenced by the lightness and heat resistance this material offers in different applications, such as construction and packaging. However, population growth and the lack of PS recycling lead to a large waste generation, affecting the environment. Pyrolysis has been recognized as an effective recycling method, converting PS waste into valuable products in the chemical industry. The present work addresses a systematic, bibliometric, and statistical analysis of results carried out from 2015 to 2022, making an extensive critique of the most influential operation parameters in the thermo-catalytic pyrolysis of PS and its waste. The systematic study showed that the conversion of PS into a liquid with high aromatic content (84.75% of styrene) can be achieved by pyrolysis. Discussion of PS as fuel is described compared to commercial fuels. In addition, PS favors the production of liquid fuel when subjected to co-pyrolysis with biomass, improving its properties such as viscosity and energy content. A statistical analysis of the data compilation was also discussed, evaluating the influence of temperature, reactor design, and catalysts on product yield.

The role of temperature profile during the pyrolysis of end-of-life-tyres in an industrially relevant conditions auger plant

Pyrolysis is a chemical recycling process of interest as a means to achieve a sustainable circular economy for end-of-life tyres (ELTs). In the pyrolysis process, ELTs are converted into tyre pyrolysis gas (TPG), tyre pyrolysis oil (TPO) and raw recovered carbon black (RRCB). This work investigates for the first time the effect of different temperature profiles by using a single-auger pyrolysis reactor in an industrially relevant scale (TRL-5). Since the development of this process at this representative scale is quite limited and the temperature profile has not been previously studied, the results achieved in this work can provide a useful database for the development of this process at industrial scale. For this purpose, two different sources of ELTs, commercial truck tyres (CTTs) and passenger car tyres (PCTs), were used. Accordingly, the experimental campaign was conducted using two different incremental temperature profiles (425-550-775 °C and 600-700-800 °C) based on those that can be replicated in an industrial-scale auger pyrolysis plant. For the sake of comparison, two isothermal heating conditions (500-500-500 °C and 600-600-600 °C) were also tested. The results confirmed the remarkable influence of temperature profile on both the distribution and properties of products. The 425-550-775 °C temperature profile was found to enhance limonene production, which is associated with the minimisation of secondary reactions in the first heating zone of the reactor. Additionally, there were very low carbonaceous deposits found in the RRCB because of the high severity of devolatilisation conditions in the third heating zone of the reactor. On the other hand, when the temperature profile was raised, the production of single-ring aromatics, particularly benzene, toluene, ethylbenzene and xylenes (BTEX) significantly increased in the TPO at the expense of limonene. Thus, from this strategy, it is possible to tune the properties of the products depending on the requirements of the application in a single step, getting closer for circular economy in the ELT recycling domain.

Influence of CaO on the thermal kinetics and formation mechanism of high value-added products during waste tire pyrolysis

There is a lack of detailed research on the production of isoprene and D-limonene by solid base-catalysed thermal depolymerization of waste tires (WTs). This work aimed to investigate the thermal decomposition characteristics, reaction kinetics, high value-added products production and potential mechanisms during WT pyrolysis in the presence of calcium oxide (CaO) via Thermogravimetry-Fourier Transform Infrared spectrometer (TG-FTIR) and Pyrolyzer-Gas Chromatography/Mass spectrometry (Py-GC/MS). The results obtained from TG indicated that CaO accelerated depolymerization in terms of reducing the reaction temperature, which is also reflected in the kinetic parameters. It can be found that the content of D-limonene increased by 13.76% and that of isoprene increased by 37.57%, which were attributed to differences in the depolymerization mechanisms in the presence of CaO. Furthermore, CaO had a profound impact on desulfurization by reducing benzothiazole, sulfoacid, and thiophene. The potential catalytic mechanisms of isoprene and D-limonene production and desulfurization were also proposed. This work deepens the understanding of the catalytic pyrolysis of WT under CaO and unambiguously demonstrates the great potential of CaO in enhancing isoprene and D-limonene production, providing new insight for the cleaner production of high value-added products from WT.

Production and Characterization of Maximum Liquid Oil Products through Individual and Copyrolysis of Pressed Neem Oil Cake and Waste Thermocol Mixture

In this study, individual and copyrolysis experiments were performed with pressed neem oil cake (NOC) and waste thermocol (WT) to produce high grade liquid oil. The effects of reactor temperature, heating rate, feed ratio, and reaction time on product yields were investigated to identify the optimum parameters for maximum oil yield. The maximum oil yield of 49.3 wt%, 73.4 wt% and 88.5 wt% was obtained from NOC pyrolysis, copyrolysis, and WT pyrolysis under optimized conditions. During copyrolysis, the maximum oil product was obtained under NOC/WT ratio of 1 : 2 and at the temperature of 550°C. The liquid oils obtained from thermal and copyrolysis were subjected to detailed physicochemical analysis. When compared to biomass pyrolysis, the copyrolysis of WT and NOC had a substantial improvement in oil properties. The copyrolysis oil shows higher heating value of 40.3 MJ/kg with reduced water content. In addition to that, the copyrolysis oil obtained under optimized conditions is analyzed with Fourier transform infrared spectroscopy (FT-IR) and Gas chromatography–mass spectrometry (GC-MS) analysis to determine the chemical characterization. The analysis showed the presence of aliphatic and aromatic hydrocarbons in the oil.