A Pyrolysis Patent Review for Non-Recycled Plastics and End-of-Life Tires

The pyrolysis of waste plastic and scrap tires is revolutionizing the energy sector, converting non-recyclable materials into valuable liquid fuels and industrial chemicals. This patent review highlights key innovations in pyrolysis technology, showcasing advancements that enhance efficiency, sustainability, and commercial viability.

In many aspects, plastic-to-liquid fuel development, refining, and commercialization are classic examples of market forces being the main determining factors in adopting a relatively well-developed technology. This article provides an overview of recent efforts to produce a more efficient plastic/rubber-to-liquid fuel technology to make it a more commercially viable venture. Patent and non-patent activity worldwide is examined, the main drivers of technology are identified, and their unique contributions are briefly described.

The Drive Behind the Technology

Local and municipal jurisdictions constantly explore ways to deal with plastic (and rubber/tire) waste and promote reuse, recycling, and recovery of plastic waste over landfilling. Worldwide plastic production soared from 1.5 million m.t./year in 1950 to 245 million m.t./year in 2008, a trend that is expected to continue [2013 European Commission study on the impact of plastic waste]. Also of concern to the global community of nations is the plastic waste estimated to form 80% of the enormous waste patches in the Atlantic and Pacific oceans – this causes sea species to suffer from entanglement or ingestion of released plastic additives that can act as endocrine disruptors.

A Brief Description of the Technology

The production of gasoline-like fuels suitable for internal combustion engines (e.g., gasoline, diesel) via catalyzed or non-catalyzed thermal decompositions of waste plastic has been known for decades. The process is generally known as pyrolysis. Conventionally, pyrolysis implies a process in which organic substances are reduced or cracked by subjecting a material to heat without oxygen. The pyrolytic reactions are endothermic, i.e., demand heat delivery to a reactor. Pyrolytic cracking is carried out without oxygen to prevent combustion as a potential reaction pathway.

Typically, the pyrolysis products comprise solids, oily liquids, and vapors containing valuable hydrocarbon gases and various contaminants to remove. The pyrolytic process reduces scrap tires into three product streams: an oily liquid, a gas, and carbon char (PyroChar). A related decomposition process to pyrolysis is gasification, whereby coal or biomass is heated under reduced oxygen levels, and the product is synthesis gas (SynGas, consisting mainly of H₂ and CO) that is utilized to produce fuels and platform chemicals via the Fischer-Tropsch process.

High-level Overview of Recent Patent Activity

The following Table depicts 14 inventions (1981-2015, mostly since 2009) representing some of the significant improvements made to the pyrolysis process to produce oil/fuel from waste plastic and scrap tires/rubber. This is followed by a discussion that also incorporates relevant non-patent information.

Patent/App Number	Year	Assignee	Title	Technology
US2015001061	2015	JBI Inc. (Plastic2oil)	System and process for converting plastics to petroleum products	Solid waste plastics are processed by melting (250-340 oC), pyrolysis (340-445 oC), vaporization, and selective condensation, whereby final in-spec petroleum products are produced (diesel, gasoline, furnace fuel, kerosene, propane, butane, ethane or methane).
US8927797	2015	Natural State Research Inc	Method for converting waste plastic to lower-molecular weight hydrocarbons, particularly hydrocarbon fuel materials, and the hydrocarbon material produced thereby	Waste plastic (HDPE, LDPE, PP, PS) is melted in an aerobic atmosphere, thermally decomposing the plastic melt, adding cracking catalyst to the melt, and distilling at least a portion of the mixture, whereby a liquid hydrocarbon fuel/distillate is produced (gasoline and diesel, C3 to C27).
US2014371385	2014	Black Bear Carbon B.V.	Method for obtaining a carbon black powder by pyrolyzing scrap rubber, the carbon black thus obtained and the use thereof	Scrap rubber, particularly tires, undergoes pyrolysis (630-670 oC). The resulting char material is milled to carbon black powder (60-98 percent carbon black, less than 2.0 weight percent of volatiles, and 0-30 weight percent of silica). Carbon black powder is used as a filler or a reinforcing agent in a rubber composition, an ink, a paint, a bitumen, a thermoplastic composition, or a thermoplastic elastomer.
US8344195	2013	J. Srinakruang (Thailand, Individual Inventor)	Process for producing fuel from plastic waste material by using a dolomite catalyst	Pyrolysis (330-400 oC) of plastic waste (PE, PP, PS): The resulting liquid is first subjected to a semi-batch catalytic cracking reaction over a dolomite catalyst to obtain high-quality oil for fuel (mainly light and heavy naphtha).
US8425731	2013	Advanced Pyrotech SDN BHD	Pyrolysis process for decomposing rubber products	Shredded tires are fed constantly into the pyrolysis vessel. In contrast, the by-products of the pyrolysis are continually discharged – the waste tire particles fed into the carbonizing reactor are conveyed through the reactor by a continuously rotating drag chain conveyor that travels bi-directionally in a continuous loop in transfer cylinders that operate in a partial vacuum (oxygen is below its stoichiometric level to prevent combustion). As the waste tire chemically decomposes through a pyrolysis process inside the reactor, oil vapor, referred to as a second by-product, and a synthesis gas (SynGas) are recovered from the waste tire particles. In contrast, the waste tire is conveyed through the first transfer cylinder, leaving a small quantity of partially decomposed waste tire, carbon black, referred to as the fifth by-product, and the remaining steel wire to be transferred through the second transfer cylinder.
US2012261247	2012	Cynar Plastics Recycling Ltd.	Conversion of waste plastic material to fuel	pyrolysis in an oxygen-free atmosphere (240-280 oC) to provide pyrolysis gases followed by conversion to diesel and kerosene
US7959890	2011	RIPP Resource Recovery Corp.	Method of reclaiming carbonaceous materials from scrap tires and products derived therefrom	Tires are shredded and pyrolyzed (450-550 oC) in an anaerobic environment to produce char. Volatile organics and the char are removed from the reaction chamber, the char is cooled in a second anaerobic environment, and metal and textile components (steel and fiber cords) are removed to obtain pyrolytic carbon black, which is milled into particles of 325 mesh size or smaller and utilized in a polymerization process that produces recycled rubber.
US7758729	2010	Agilyx Corp. and Plas2Fuel Corp.	System for recycling plastics	The plastic material is placed in a treatment chamber and heated to 270-375 C, which results in pyrolytic cracking in the absence of oxygen to prevent combustion as a potential reaction pathway from occurring. A vacuum removes vapor (pyrolyzed inorganic species and gaseous organic species) from the chamber—the chamber is heated in incremental steps—and the vapor from pyrolytic cracking is contacted with a pH-buffered aqueous media, resulting in condensation of gaseous organic species contained within the vapor. Chlorine and bromine are separated from the oil end-product.
US7626061	2009	MPCP GmbH	Method and apparatus for continuous decomposing waste polymeric materials	Waste polymeric materials (scrap tires, rubber, polyurethane) are turned into valuable liquid chemicals and/or liquid fuels. The decomposition process is carried out under moderate temperatures (less than 850 C) and atmospheric pressure in the presence of air and a feed of liquids containing oxygen. This continuous process is characterized by the low residence time (3-25 minutes). The liquid containing oxygen is acetone, methanol, ethanol, water, or mixtures thereof. At least one hydrogen, carbon monoxide, gaseous hydrocarbon, and carbon is recovered in this process. Liquid oil and solid, oil-free carbon are also recovered.
US5811606	1998	Plastic Advanced Recycling Corp.	Process and equipment for treatment of waste plastics	Waste plastics (PE, PP, and PS) and a catalyst are mixed into a reactor for a catalytic cracking reaction (280-480 oC), removing the solid impurities in the generated vapor, condensing the vapor in a condenser, and returning the non-condensable gas to be burnt in the heating furnace. The condensate is then distilled and separated to obtain gasoline and diesel oil, which will be stabilized to get high-quality gasoline and diesel oil.
US5821396	1998	Fabspec, Inc.	Batch process for recycling hydrocarbon-containing used materials	A pyrolysis batch process is described for recycling scrap tires and plastics (ABS, polystyrene, and other non-chlorinated thermoplastics) to obtain helpful light oil and fuel gases. Used tire cuttings are loaded into a rotatable reactor, which is closed, evacuated, rotated, and heated until an exothermic reaction is initiated.
US5414169	1995	Mazda Motor Corp.	Method of obtaining hydrocarbon oil from waste plastic material or waste rubber material and apparatus for carrying out the method	Thermal cracking of waste plastic/rubber followed by acid catalysis
US4515659	1985	Ford Motor Co.	Pyrolytic conversion of plastic and rubber waste to hydrocarbons with essential salt catalysts	Pyrolysis under nitrogen at 400-700 oC and in the presence of one percent essential salt catalyst
US4251500	1981	Bridge-stone Tire	Process for hydrocracking a waste rubber	Hydrocracking (350-500 oC) under a hydrogen partial pressure of 100-300 atm. Waste rubber, such as used tires, conveyor belts, hoses, etc.

What is the Patent Activity Telling Us About the Challenges and the Opportunities?

A review of the full text for the above patents points to some of the significant drawbacks or challenges encountered in commercial-scale processes: A) chlorine/halogen removal when halogen-containing polymeric materials (e.g., PVC, PTFE) are among the plastic wastes, B) heat gradients due to poor heat conductivity of plastics, resulting in char accumulation at heat transfer surfaces, and C) economics, varying from high catalyst costs/consumption to high energy consumption. The various inventions aim to remedy one or more of these drawbacks.

Another challenge identified as an impetus for the above inventions is the need for continuous operation instead of batch mode to enhance the economic viability of the conversion process. It should be noted that the continuous operation mode for scrap tires is much more complicated than the constant processing of other polymeric wastes because of a significant content of carbon (and steel) that cannot be converted entirely into gaseous or liquid products and, therefore, should be permanently removed out of a decomposition reactor.

The Current Reality and Opportunities

As mentioned at the beginning of this article, the well-established pyrolysis process is being improved further, but market adoption has been elusive. As shown in one of the above inventions, some early commercial installations in Europe were short-lived for economic reasons, but commercial installations continue in Japan and other countries. Interestingly, the three earlier patents (1981-1995) in the above Table are assigned to Bridgestone Tire, Ford Motor Company, and Mazda Motor Corporation. However, these patents have not been commercialized in any significant manner.

Even more revealing about the lack of commercial viability of this technology is the announcement in 1994 by BP Chemicals that it had assembled a consortium of European petrochemical companies to help develop its polymer cracking technology [Miller, 1994, “Industry Invests in Reusing Plastics”]. Petrofina, DSM, Elf-Atochem, and Enichem were said to have participated in a pilot plant at BP’s Grangemouth site in Scotland. Despite the auspicious results from this pilot plant with a capacity of 50 kg/hr plastics waste and a slated 2001 expansion to a demonstration plant by the consortium with a capacity of 25,000 m.t./year (a $30-40 million investment), we could not find any evidence of the continuation of this high-profile effort.

Not all the news on the commercialization of this technology is gloomy! Indeed, two of the patent assignees in the above Table have been running commercial operations over the past few years: Plastic2Oil (Buffalo, NY – a 2015 patent assigned to JBI Inc.) and Cynar (Ireland – a 2012 patent assigned to Cynar Plastics Recycling Ltd.). There are also established pyrolysis operations in Asia. For instance, a joint venture between a Malaysian company and a South Korean company is said to have operated for a short time in 2008 with a 120 m.t./year capacity. This commercial plant was designed for scrap tires being broken down into carbon black (30%), recovered oil (50%), and non-condensable flammable gas and steel wires (10% each).

The only constant in this technology space is the variability of market forces. For instance, the tipping fee for tires (the cost to the transporter for tipping his truck’s contents at a disposal site) can range from $10/ton to $110/ton depending on the jurisdiction – the tipping fee at a Nevada landfill was at some point so low that the State had no tire processing or recycling/diversion industry. In recent years, the uncertainty in permitting the plants to burn tires (tire-derived fuel, TDF), as well as the lack of experience with TDF, has retarded the U.S. implementation of TDF. For instance, a TDF utility plant in Sterling, Connecticut, had to shut down in 2013 after 22 years in operation because the State modified its regulations on the definition of renewable energy. Thus, various factors can make the price and supply of scrap tires quite volatile, further clouding the prospect of long-term planning for adopting pyrolysis technology.

Regular Monitoring of the Technology, Regulatory, and Market Space

On a foundation fully customized to its client’s needs, Klean Industries routinely monitors the carbonization, pyrolysis, gasification technology space, regulatory changes, and market conditions to brief its clients in the chemical industry sectors regularly.

Contact Klean Industries to learn more about the landscape of intellectual properties in the pyrolysis sector  » GO.