Tire‑Derived Oil (TDO): Unlocking Its Potential as an Advanced Fuel Pool Component
Tire-derived oil (TDO) is emerging as a powerful component in the advanced fuel pool, offering refiners a scalable, sustainable drop-in solution that bridges the gap between circularity and performance.
Refiners around the world are looking for alternatives to producing fuels from petrochemicals only. This is due to expected future declines in crude oil reserves, combined with significant growth in fuel demand expectations worldwide and increasing environmental awareness among the population.
Waste and biorefineries are garnering significant interest worldwide as sustainable solutions for waste management. Else, a wide range of resources, such as energy, fuels, chemicals, and other viable by-products, can be recovered from municipal waste streams, waste plastic, and waste tires. Acknowledging that end-of-life tires (ELT) hold an enormous potential for recovering finite resources, this article aims to contribute to the development of an eco-friendly post-processing approach to realize their full potential in refineries.
Development trends
Pyrolysis processes are an efficient, viable, and sustainable approach for the valorisation of end-of-life tires into oil, value-added gas, and recovered Carbon Black (according to ASTM D8178). The thermochemical decomposition of end-of-life tires offers multiple benefits, including the simultaneous realization of sustainable waste management, resource recovery, and the displacement of conventional fossil fuels.
Advances in various aspects of industrial-scale production, including product quality, production efficiency, operational costs, capital investment, and tipping fees, have enabled ELT pyrolysis to demonstrate technical maturity and economic viability.
Besides being a valuable feedstock for various chemical components, TDO presents an attractive source of renewable energy. It has come a long way in being considered a potential substitute for crude oil-derived products, or for use in a blend with them. Waste tires contain a fraction of biogenic carbon that mainly comes from their natural rubber content. Therefore, the tire-derived pyrolysis liquids (TDO) can be specified as advanced fuel pool components. This fact is essential from both a product origin and a quality, application, and customer tariff classification perspective.
The raw waste tire-derived pyrolysis liquids are the most economically and energetically attractive products. However, their application is limited by several properties: their distillation characteristics, proportion of compounds having boiling point over 360°C, flash point, cetane number, density, PAH content, sulphur and chlorine content, storage stability, and combustion properties - regular and unregular emissions, metal content, chemical and hydrocarbon group composition and polarity causing homogeneity and incompatibility problems. The presence of micro-carbon particles in the pyrolysis oil can also cause erosion or corrosion problems in the engines in which they are used.
As is the case with other petroleum derivatives, economic and engine technology developments have mandated that tire-derived materials be produced with higher quality and performance, and with lower contaminant content. Thus, the pre-treatment of pyrolysis feed and the upgrading of raw tire-derived oils (TDO) with chemical and physical techniques are being explored to enhance the properties of TDO further.
Several options exist to upgrade TDO with chemical and physical techniques:
- Physical properties such as distillation/fractionation have been found to enhance general properties of raw TDO, namely: density, viscosity, heating value, and flash point.
- Desulfurization, hydrotreating has been found to reduce sulphur, chlorine, and water content, while hydro-denitrification removes nitrogen compounds. Other chemical treatment processes may also be employed.
Distillation/fractionation
The atmospheric distillation process is carried out at temperatures ranging from 150 to 200°C to divide raw TDO into a lighter and heavier fraction because the maximum amount (80%) of distilled TDO is obtained within this range (5% is left out as pyro gas, and 15% is found as sludge).
Further refining the raw TDO through fractional distillation can result in significant increases in distillate concentrations of toluene (from 7.65% to 68.52%) and xylene (from 10.09% to 65.20%). Through fractionation, the flash point, viscosity, and density can be modified in line with market requests, but the obtained fractions are not yet considered stable and chlorine-free.
Partial elimination of impurities, moisture, carbon particles, sulphur, and sediments results in a 7% higher heating value. The diesel-like fraction from raw TDO fractionation can be added in appropriate proportions as a component of light heating oil with a sulfur level S = max. of 0,1% m/m. Upon further refinement, the distilled TDO can even be employed as an alternative to low-sulfur transportation fuel, fuel oil, or as a diesel blend.
Hydrodesulfurization
A conventional hydrodesulfurization process has high operating expenses (OPEX) and encounters difficulty in removing sulfur compounds with steric hindrance. Consequently, various research efforts have been made to overcome the limitations of conventional HDS processes and explore alternative technologies for deep desulfurization of TDO and/or combination with other refinery middle distillates. The alternative processes being investigated to produce ultra-low-sulphur content fuels and fuel oils are adsorptive desulfurization, biodesulfurization, oxidative desulfurization, and extractive desulfurization.
From an industrial perspective, a distillation treatment and sequential 2-stage hydrotreating at pressure below 4MPa or hydrotreating at pressure ranged 6-16 MPa, or hydrocracking strategies, all using desulphurisation and denitrification catalyst systems have been proposed for upgrading TDO quality and for simultaneously overcoming all limitations to producing high quality motor fuels, fuel oils and solvents.
In addition, the 30°-100°C fraction of hydrotreated waste tire-derived gasoline can be used as a potential raw material for the catalytic reforming unit, producing reformate with RON=90-100, which is a gasoline pool component.
Oxidative desulfurization
The oxidative desulfurization process has received more attention due to its mild operating conditions and high sulfur removal efficiency. A critical challenge is the commercialization of a catalytic oxidative desulfurization process due to some significant obstacles, such as low selectivity for the sulphides present in fuel feedstock, recovery, and separation of the used catalysts after the reaction, increased CAPEX in case of high sulphur content in the feedstock as well as a waste management challenge concerning disposal of the oxidized sulphur containing compounds.
A possible upgrading path would be oxidative desulfurization followed by hydroprocessing, as is typically done in conventional refineries. However, these processes, while highly effective, are hardly economically feasible in the dimensions of existing or planned ELT pyrolysis projects. This path may also prove to be realistically possible in the future, through capacity increases and/or joint ventures by pyrolysis companies, as well as through downscaling of existing large-scale industrial applications.
Chemicals obtained from TDO
Refiners worldwide are moving production away from fuels toward petrochemicals. This is due to the expected future decline in crude oil reserves, combined with significant growth in petrochemical demand expectations worldwide.
Recently, significant attention has been given to the benefits of the chemicals obtainable from raw TDO. This is mainly due to the less intensive purification steps associated with chemical feedstock production, as well as the firmly established markets for the chemicals obtained from TDO.
For example, Limonene is reported to be a high-value primary material in the chemicals industry with several noteworthy applications. It can be utilized as a cutter stock, natural cleaning solvent, industrial diluents, in the production of fragrance, adhesives, pigment dispersing agents, resins, and bonding agents, and as a food additive.
Likewise, the presence of benzene, toluene, and xylene (BTX) in TDO has been given renewed attention due to their wide industrial use. Benzene is used to synthesize pigments, rubber, fibres, plastics, etc.; toluene is used in the industry to produce medicines, pesticides, and dyes. In addition, toluene and xylene are high-octane components for ultra-low-sulphur automobile gasoline, and they can also be used as solvents in the solvent-based chemical recycling of waste plastics.
Conclusion
Due to ongoing significant research and development, end-of-life tire pyrolysis technology and techniques for applying its products are constantly evolving. However, the commercialization of upgrading processes is still in its infancy.
From the perspective of oil and gas producers, lenders, investors, and regulators alike, there is a distinct lack of clarity regarding what constitutes action toward TDO quality gate limits to be supplied to refineries for further processing.
This also applies from the perspective of the ELT pyrolysis industry: There are no official refinery gate limits published for alternative fuel feeds (TDOs) that can be processed in catalytic reforming units, fluid catalytic conversion units, and hydrocracking units, as well as pyrolysis gasoline splitters or aromatics extraction units. Therefore, there is no exact input data for TDO fractionation. Without these clear targets, financiers and investors become hesitant to invest without knowing how the products will comply with refinery criteria. This, of course, naturally hinders accelerated development.
A “round table” should therefore be initiated with stakeholders of the ELT pyrolysis industry and potential buyers of TDO fractions to develop uniform standards and gate limits. The ASTM D36 committee on recovered Carbon Black could serve as a good example.
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Partner with Klean and Fuel Your Future
Refiners around the world are under increasing pressure to diversify fuel stocks and cut carbon intensity. Klean’s tire-derived oil (TDO) is a drop-in, scalable solution already proving its value. With unmatched pyrolysis expertise and fuel upgrading integration, Klean Industries helps you tap into a low-carbon feedstock that turns end-of-life tires into refinery-ready, advanced fuels.
Klean Industries delivers a turnkey path to net-zero opportunities. Our proprietary pyrolysis and upgrading processes convert end-of-life tires into refinery-grade TDO a drop-in, high-performance oil that displaces fossil fuels and strengthens your bottom line.
- Elevate your fuel strategy: connect with our engineers to pilot or scale TDO integration, and transform circular waste into competitive advantage.
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