How to Produce Benzene, Toluene, and Xylene Sustainably from Plastic Waste

Authors: Farah Siddiq, M.Hassam Khan, Sirous-Rezaei Pouya, Elmeri Pienihäkkinen (VTT)

The global accumulation of plastic waste represents one of the most pressing environmental and economic challenges of our time. Although various mechanical recycling approaches exist, a significant portion of plastic waste remains unrecycled due to contamination, mixed composition, or degradation. In the TREASOURCE project, our primary goal is to address this issue by demonstrating the feasibility and scalability of catalytic pyrolysis as a route to convert unrecycled plastic waste into valuable aromatic hydrocarbons, specificallybenzene, toluene, and xylene (BTX).

Read the use case:

Case Tampere | Conversion of Plastic Waste into Chemical Building Blocks

BTX compounds are among the most important chemical building blocks in the petrochemical industry. They serve as precursors in the production of a wide range of materials, including plastics (e.g., polystyrene, PET), synthetic fibers (e.g., nylon, polyester), detergents, pharmaceuticals, dyes, resins, and paints. Currently, BTX is predominantly derived from fossil-based sources such as naphtha or natural gas liquids through catalytic reforming and steam cracking. Our project explores an alternative, circular approach by recovering BTX from plastic waste — reducing both environmental pollution and fossil resource dependency.

In the first phase of our research, we performed extensive laboratory-scale testing using a fixed-bed reactor setup to assess the catalytic conversion potential of various plastic types and catalyst formulations. The plastics used in these experiments included common waste polymers such as polyethylene (PE), polypropylene (PP), and polystyrene (PS). Our catalyst screening focused on different zeolite-based materials known for their shape-selective and acid-catalysed cracking capabilities.

The results were promising. With optimal catalyst combinations, we achieved BTX yields of up to 40% at 550 °C, demonstrating that a cost-effective and selective production of BTX from plastic waste is indeed feasible. The use of appropriate catalysts not only enhanced BTX formation but also minimized the production of undesirable by-products such as heavy tars or gases. These findings confirmed the technical viability of our approach at the lab scale.

Building on these results, our next objective is to scale up the process using plastic feedstocks that more accurately reflect real-world waste streams. These include plastic samples originating from industrial, household, and agricultural sources, which are typically heterogeneous and more challenging to process.

Before pyrolysis, these waste plastics undergo pre-treatment steps to ensure consistent feed quality. These steps include shredding, sorting, washing, and compounding into granulated form using a modular extruder system (MODIX). This modular approach allows us to simulate industry-relevant preprocessing conditions and ensures the material is in an optimal form for pyrolysis.

For the larger-scale catalytic pyrolysis experiments, we will employ two setups:

A Process Development Unit (PDU) with a throughput of 2 kg/h.
A Pilot Unit operating at 20 kg/h, suitable for more extended and continuous operations.

Both units are equipped with dedicated catalyst regenerators, enabling steady-state operation by continuously restoring the catalyst’s activity through controlled oxidation of coke deposits. This feature is critical for maintaining performance and extending catalyst life during long runs.

After pyrolysis, the hot product vapors are rapidly quenched using fractional condensation systems. This step allows us to selectively condense aromatic liquids while minimizing thermal degradation and secondary reactions. The condensed liquids, rich in BTX and related aromatics, are then subjected to purification via distillation.

Finally, the purified BTX-rich streams will be thoroughly characterized using advanced analytical techniques (e.g., GC-MS, NMR, HPLC) to evaluate their quality and suitability for downstream applications in the chemical and polymer industries.

Through the TREASOURCE project, we aim to demonstrate not just the technical feasibility, but also the economic and environmental value of integrating catalytic pyrolysis into the circular economy. By converting problematic plastic waste into high-value chemical feedstocks, we contribute to a more sustainable, resource-efficient, and low-carbon future.

The Most Important Requirements for Success

Reliable Feedstock Supply

A consistent and well-prepared flow of plastic waste (shredded, sorted, and cleaned) is essential to ensure steady operation and reproducible yields. Without a predictable input stream, process optimization and scaling cannot succeed.

Catalyst and Process Optimization

The choice of catalyst and fine-tuning of process parameters (temperature, residence time, regeneration cycles) are critical for maximizing oil yield with higher selectivity of BTX, while minimizing coke formation and unwanted by-products.

Cross-Sector Collaboration

Strong cooperation between industry, research institutions, policymakers, and waste management operators are required to secure financing, create favourable regulation, and ensure that results are scalable and aligned with circular economy goals.

Legislative Aspects

The process depends on access to pyrolysis reactors (batch, fluidized bed, or ex-situ catalytic units) equipped with efficient condensation and catalyst regeneration systems. Analytical facilities (GC-MS, NMR) are also required to monitor product quality. Potential pyrolysis oil post-treatment needs depend on the oil quality. Existing oil refinery infrastructure could be used in the post-treatment and upcycling of the intermediate products (pyrolysis oils/gases) to end-products, such as BTX or virgin quality plastics.

Technology

Finance

Initial investment varies depending on scale: small lab units require modest funding (hundreds of thousands €), while pilot plants require multimillion € investment. Operational costs include catalyst replacement, waste preprocessing, and energy. Both public (EU/municipal funding) and private (industry partnerships, venture capital) financing are often needed. Locally, the business potential is strong due to demand for sustainable chemical feedstocks.

Stakeholders

• Waste management companies (feedstock supply)
• Catalyst and equipment suppliers (technology)
• Chemical and petrochemical industries (off-take agreements)
• Policymakers and regulators (supportive frameworks)
• Research institutions (process optimization)

Society

Society benefits from reduced plastic waste, lower dependence on fossil feedstocks, and new green jobs. Public acceptance is vital, requiring communication that chemical recycling complements not competes with mechanical recycling.

Environment

The practice reduces plastic landfilling and incineration, lowers greenhouse gas emissions, and promotes circularity. However, emissions and by-products (char, gases) must be carefully managed with proper treatment systems.

Governance

Effective governance requires coordination across municipalities, regional authorities, and industry associations. Supportive governance models can speed up permitting and align recycling strategies with circular economy targets.

Safety

Pyrolysis involves high temperatures and flammable vapors. Risks include fire, explosion, and exposure to toxic gases. Safety requires robust reactor design, proper ventilation, gas scrubbing, explosion-proof equipment, and regular training.

Organisation

Preparation for such projects typically requires 3–5 years, including feasibility studies and funding acquisition. Stakeholder negotiations can take another 6–12 months depending on complexity. Teams should be multidisciplinary: chemical engineers, Research Scientist, economists, safety officers, and policy advisors.