Plastogaz, a Swiss plastic recycling startup founded in 2019, develops plastic hydrocracking technology that uses hydrogen gas and ruthenium-modified zeolite catalyst to convert plastic waste into methane and valuable liquid fuels.
Challenges: plastic recycling
Plastic waste is a major environmental challenge, with over 450 million tons produced in 2019, and more than 350 million tons turning into waste. Most of this waste ends up in landfills or is incinerated, while only a small portion is recycled. This situation underscores the urgent need for effective recycling solutions. Technologies like gasification and pyrolysis offer potential methods for recycling plastics.
The gasification process involves reacting plastic waste with a gasifying agent, such as steam, oxygen, or air, at high temperatures between 500 ºC and 1300 ºC. This reaction produces synthesis gas (syngas), a mixture of hydrogen, carbon monoxide, and other hydrocarbons. Gasification can handle a wide variety of plastic types, including mixed and contaminated plastics, making it a versatile solution for plastic waste management. However, challenges like tar formation and the requirement for advanced gas cleaning systems necessitate further research and development.
Pyrolysis is a process that heats plastic waste to high temperatures, typically between 400 ºC and 600 ºC, without oxygen. This thermal degradation breaks down long-chain polymers into smaller molecules, producing a mixture of liquid, gaseous, and solid products, such as pyrolysis oil, syngas, and char. It is increasingly recognized as an alternative method for managing plastic waste, particularly for types that are challenging to recycle through conventional methods. However, further research and technological advancements are necessary to enhance its efficiency, product quality, and economic viability.
Plastogaz Technology
Plastogaz has developed a hydrocracking technology for recycling plastic waste, which requires less energy and results in fewer undesirable by-products.
This process uses hydrogen and a catalyst to break down complex plastic polymers into smaller, more useful hydrocarbon molecules, typically at lower temperatures (300–350 ºC) compared to gasification and pyrolysis. Hydrocracking offers better control over chemical reactions than processes like pyrolysis. By adjusting the process conditions and catalyst composition, the yield and quality of the resulting products can be optimized.
Plastogaz has developed a ruthenium-modified zeolite catalyst that effectively catalyzes the hydrocracking of plastics, producing methane gas and valuable liquid fuels such as alkanes (e.g., paraffins, isoparaffins, n-hexane), cycloalkanes (e.g., cyclohexane and methylcyclohexane), alkenes, and aromatic hydrocarbons (e.g., naphtha). This technology can process mixed plastic waste streams, which often contain various types of plastics. This versatility is essential for enhancing recycling rates and managing diverse waste streams that are typically difficult to recycle using conventional mechanical methods.
How Plastogaz converts plastic to fuels
The diagram below depicts Plastogaz’s plastic hydrocracking process.
Plastic waste and a ruthenium-modified zeolite catalyst are combined in an autoclave reactor, which is purged with hydrogen gas to create an air-free environment. The autoclave is then pressurized to 50 bar with hydrogen gas and heated to 300 ºC. The mixture is stirred, typically at 500 rpm, for a specified reaction time ranging from 4 to 18 hours, resulting in the production of methane and liquid fuels. After the reaction is complete, the autoclave is cooled to room temperature.
The gas vented from the autoclave contains methane, unreacted hydrogen, and traces of COâ‚‚ (1%). Methane, a natural gas, is extensively used in various industries both as a feedstock for chemical synthesis and as a significant source of electricity generation through gas and steam turbines. Natural gas burns cleaner than other fossil fuels, emitting less greenhouse gas per unit of energy released. Consequently, power generation using natural gas is considered a cleaner fossil fuel energy source.
The liquid product discharged from the autoclave consists of liquid fuels, solid catalysts, and water. It is first passed through a filter to separate the solid catalysts, which can be readily recycled since there are no solid by-products. The liquid fuels, being immiscible with water, can be easily recovered using a liquid-liquid separator.
Plastogaz’s plastic hydrocracking process operates under high pressure. Increasing the hydrogen pressure significantly boosts the conversion efficiency of plastic polymers, from 54% at 50 bar to 99% at 100 bar. Additionally, high hydrogen pressure promotes methane production and reduces CO₂ by-products. This suggests that either hydrolysis is suppressed or the ruthenium-modified zeolite catalyst can catalyze the methanation of CO₂ at temperatures much lower than those typically used in the Sabatier process:
CO₂ + 4 H₂ → CH₄ + 2H₂O
How Plastogaz’s catalysts work for hydrocracking
Plastogaz’s ruthenium-modified zeolite catalyst consists of ruthenium nanoparticles supported on porous zeolite. In the plastic hydrocracking process, this catalyst facilitates the cracking of polymers, as illustrated in the diagram below.
The catalyst operates via a ruthenium site-dominated mechanism, which differs from the typical bifunctional mechanism involving both acid and metal sites. This unique mechanism allows for high selectivity and efficiency in methane production.
The polymer cracking process begins with the adsorption of the polymer onto the surface of the ruthenium-modified zeolite catalyst. The reaction mechanism predominantly involves chain-end initiation, where the polymer chains are broken down starting from the ends.
The ruthenium catalyst facilitates the activation of hydrogen molecules. This is crucial as hydrogen atoms are required to cleave the carbon-carbon (C-C) bonds in the polymer chains.
The activated hydrogen atoms interact with the C-C bonds in the polymer, leading to their cleavage. This breaks down the long polymer chains into smaller hydrocarbons and eventually forms methane.
The process selectively converts the plastic polymers into methane with high yields. For example, the conversion yields are 97% for polyethylene, 95% for polypropylene, and 92% for polystyrene. When mixed plastics are processed together, the methane yield can reach up to 99%.
How Plastogaz’s catalyst is fabricated
The diagram below depicts the preparation process of ruthenium-modified zeolite catalyst.
Commercial granules of zeolite (aluminosilicate, FAU type) (10.0 g) are ground to powder. The powder is dispersed in deionized water (75.0 mL). The suspension is sonicated for 10 min and suction filtered. The residual solid zeolite is washed with deionized water and dried at 250 ºC in an oven for 18 h.
RuCl₃∙3H₂O (207 mg, 1.0 mmol) and the zeolite (1.0 g) are mixed with deionized water (24.0 mL). The suspension is stirred (350 rpm) at 75 ºC for 18 h and cooled to room temperature. The excess RuCl₃ is not removed.
NaBHâ‚„(s) (189 mg, 5.0 mmol) is dissolved in deionized water (24.0 mL) and added to the round bottle flask in one portion. The suspension is stirred (800 rpm) for 1 h. The solution synthesis allows for extruded ruthenium nanoparticle solid catalysts.
The solid is vacuum filtered and then washed with deionized water. The washed ruthenium-modified zeolite catalyst is dried at 250 ºC in an oven for 18 h.
Plastogaz Patent
- EP3884013B1 Direct conversion of plastic materials into methane and/or liquid fuels
Plastogaz Technology Applications
- Plastic waste management
Plastogaz’s technology enables the conversion of plastic waste into circular feedstocks, such as green naphtha, which can be used in the chemical industry for the production of olefins and other valuable chemicals.
- Methane production
Plastogaz’s technology converts plastic waste into methane that can be directly injected into existing natural gas networks. This provides a sustainable alternative to methane production from fracking, with significantly lower environmental impact.
- Partnership with Dow
Plastogaz has formed strategic partnerships to accelerate the commercialization of its technology. Notably, a partnership with Dow, a global materials science company, aims to simplify the conversion of plastic waste to feedstock, enhancing the overall efficiency of the recycling process. This collaboration highlights the potential of Plastogaz’s technology to significantly reduce global plastic waste and emissions, contributing to a more sustainable environment.
Plastogaz Products
- Grid-compatible methane
Plastogaz’s technology efficiently converts various plastic polymers into methane with high purity (over 97%). This methane is suitable for direct injection into natural gas networks, providing a sustainable alternative to conventional methane production methods such as fracking.
- Circular feedstocks
The technology also produces circular feedstocks like circular naphtha, which can be used in the chemical industry. These feedstocks are valuable for creating new plastics and other chemical products, contributing to a circular economy.
Plastogaz Funding
Plastogaz has raised a total of CHF110K in funding over 4 rounds:
- a Grant round
- a Non-equity Assistance round
- a Debt Financing round
- a Seed round
Their latest funding was raised on Mar 24, 2022 from a Seed round.
Plastogaz Investor
Plastogaz is funded by 4 investors:
Dow Venture Capital and Foundation for Technological Innovation (FIT) are the most recent investors.
Plastogaz Founder
Felix Bobbink, Antoine van Muyden, and Wei-Tse Lee are Co-Founder.