Applications that Pyrolysis Products Might Have in the Future

The catalytic pyrolysis of various types of plastic feedstock results in the production of a liquid oil that contains a significant amount of aromatic, olefin, and naphthalene compounds, all of which are typically found in petroleum-based products. In addition, the highest heating value (HHV) of the produced liquid oil was discovered to be in the range of 41.7–44.2 MJ/kg (Table 2), which is extremely close to the energy value of conventional diesel. The highest HHV of 44.2 MJ/kg was obtained from PS/PE/PP using the AA-NZ catalyst, while the lowest HHV was found in liquid oil obtained from PS using the TA-NZ catalyst. The TA-NZ catalyst produced the lowest HHV of 41.7 MJ/kg. Therefore, the liquid oil that is produced through the pyrolysis of various types of plastic waste has the potential to be used as a different kind of source of energy. Researchers Lee et al. (2015) and Rehan et al. (2016) found that it is possible to generate electricity by pyrolyzing liquid oil in a diesel engine. This was found to be the case. Saptoadi and Pratama (2015) were successful in their attempt to use pyrolytic liquid oil as a replacement for kerosene in a stove. In addition, the produced aromatic compounds have the potential to be utilized as raw materials for the process of polymerization in a variety of different chemical industries (Sarker and Rashid, 2013; Shah and Jan, 2015). In addition, a number of researchers tried using the produced liquid oil as a transportation fuel by mixing it with regular diesel in varying proportions. The purpose of these studies was to investigate the viability of the produced liquid oil in relation to the operational efficiency of engines and the emissions produced by vehicles. Both Nileshkumar et al. (2015) and Lee et al. (2015) found that a blend ratio of 20:80% pyrolytic liquid oil to conventional diesel produced engine performance results that were comparable to conventional diesel. In addition, the exhaust emissions were comparable at the same blended ratio; however, the exhaust emissions increased with the increase in the blended amount of pyrolysis machine oil (Frigo et al., 2014; Mukherjee and Thamotharan, 2014).

Several different uses for the residue (char) that is left over after the pyrolysis machine process can be found in the field of environmental protection. The char was activated by steam and thermal activation, according to the findings of a number of researchers (Lopez et al., 2009; Heras et al., 2014). According to Lopez et al.'s (2009) research, the activation process increased the BET surface area of the char while simultaneously decreasing its pore size. In addition, Bernando (2011) improved the plastic char by adding biomaterial to it and carried out the adsorption of methylene blue dye from wastewater at a concentration ranging from 3.6 to 22.2 mg/g. Miandad et al. (2018) synthesized a novel carbon-metal double-layered oxides (C/MnCuAl-LDOs) nano-adsorbent for the adsorption of Congo red (CR) in wastewater using the char that was obtained from the  of PS plastic waste. This nano-adsorbent was successful in removing CR from the wastewater. In addition to this, the char can be utilized as a primary component in the manufacturing of activated carbon in its raw form.

The Constraints Placed on GC-MS Investigations of Pyrolysis Oil
The GC-MS method of conducting an accurate quantitative analysis of chemical components in  oil has a few drawbacks that must be taken into consideration. In this investigation, we used the mass percentage of various chemicals that were discovered in oil samples and calculated it based on the peak areas that were determined by using a normal phase DP5-MS column and FID. The spectra of the identified peaks were checked against those in the NIST and mass bank libraries. The compounds were picked out using a similarity index that was greater than 90 percent. Confirmation of the compounds that were initially identified was achieved through additional comparison with CRM standards. Only hydrocarbons could be detected by the column and detectors that were utilized. In point of fact, however, the oil that can be extracted from the majority of plastic waste has a convoluted chemical structure and may include components from other classes of unidentified chemicals, such as hydrocarbons that contain sulfur, nitrogen, and oxygen. For this reason, a qualitative chemical analysis that is both more in-depth and accurate is required to fully understand the chemistry of pyrolysis machine oil. This analysis should make use of advanced calibration and standardization techniques, as well as a variety of MS detectors such as SCD and NCD, as well as different GC columns.

The Opportunities and Obstacles Faced by Biorefineries That Rely on Pyrolysis
Waste biorefineries are gaining a lot of attention as a potential solution to the problem of how to convert municipal solid waste and other types of biomass waste into a variety of products such as fuels, power, heat, and other valuable chemicals and materials. There are many different kinds of biorefineries that can be developed depending on the kind and source of waste (Gebreslassie et al., 2013; De Wild et al., 2014; Nizami et al., 2017a,b; Waqas et al., 2018). Some examples include agriculture-based biorefineries, animal waste biorefineries, wastewater biorefineries, algae-based biorefineries, plastic waste refineries, industrial wasteThese biorefineries have the potential to play a significant role in lowering the environmental pollution and greenhouse gas emissions that are caused by waste. In addition, they have a significant positive impact on the economy and can contribute to the development of a circular economy in any nation.