Chemical recycling of plastics: current patent trends
Used plastics can now be repurposed through recycling and energy recovery. The technology of plastic waste recycling involves processes such as mechanical recycling, solvent-based recycling and chemical recycling. The latter, also known as feedstock recycling, is an interesting solution in the area of plastic waste management.
Chemical recycling is a time-tested method of breaking down plastic waste. Recently, we have observed intense development of chemical recycling technology, largely because the idea of circular economy (CE) has become popular. Chemical recycling uses the principle of polymer decomposition (depolymerisation of polymer chains) under specific process conditions into monomers or simpler chemical substances, which can then be used to produce new plastics or other materials/chemical products. Therefore, chemical recycling is a vital part of a comprehensive solution to the problem of plastic waste, and, at the same time, it compliments mechanical recycling, since it can be used for mixed or contaminated streams of plastic waste.
Depending on the kind of waste, chemical recycling uses a variety of methods and technologies, e.g. based on pyrolysis, catalytic cracking, gasification, chemolysis or depolymerisation. Chemical recycling leads to a reduction of CO2 emissions compared to combustion processes.
In Europe, the most common way of plastic waste treatment is energy recovery, followed by waste storage. Over 30% of all produced plastic waste is collected for recycling; half of it is transported to countries outside of the EU due to the lack of capacity and technology needed to recycle it. The low level of plastic waste recycling in the EU means huge economic and environmental losses. In 2020, almost 10.2 million tons of post-consumer plastic waste were collected and sent to recycling facilities, mainly outside of Europe. The main problem with plastic waste recycling is the quality and price of the product made from recycled materials compared to its virgin counterpart. This is why the members of the EP have agreed on a European plastics strategy, according to which all plastic waste from packaging should be recyclable by 2030. For the industry, this means a significant need to introduce changes right from the design stage of plastics, so that they comply with the new recycling requirements.
On the initiative of Plastics Europe, an association of plastics producers, a European Coalition for Chemical Recycling was created in March 2019. It unites 39 industry trade groups interested in development and implementation of chemical recycling. The Coalition will contribute to the work of EU Circular Plastics Alliance, whose goal is to ensure that, by 2025, 10 million tons of recycled plastics will be used in the new European products.
What is more, on 11 March 2020, the European Commission published a communication entitled “A new Circular Economy Action Plan – For a cleaner and more competitive Europe”. This plan is one of the key elements of the Green Deal and is directly connected to the European industrial strategy. It specifies a comprehensive framework for actions whose goal is to make a faster transition to a “regenerative growth model”, which will be an important part of achieving climate neutrality by 2050.
The EU action plan for a circular economy includes some 35 points. One of its important elements is the initiative aimed at designing closed-loop production processes for products from different categories, such as electronics and ICT, batteries, packaging, plastics, textiles, construction and buildings, as well as food . Moreover, regulations on waste are expected to be amended.
However, better recycling of plastics can be achieved not only with new legal regulations, but also through a change in consumer preferences and their awareness around packaging recycling. Indeed, the recycling of packaging, and especially the packaging for cosmetics or other everyday use products, begins inside the home of every consumer with proper waste segregation.
The new trends in the development of plastic waste recycling technology, which can successfully replace the traditional methods, can be seen in many patent applications. Our search for patent documents related to recycling has shown that in the last 10 years there were 237 patent families, covering 783 patent applications from this domain. The countries where the majority of such applications are filed are China, USA, South Korea and Japan. The applicants readily filed international applications, which can potentially cover 157 countries and regions. The leading companies here are Eastman Chem. Co., Lotte Chemical Corp. and Sion Tech Co. Ltd. When we analyse patent trends from the geographic perspective, we notice that the leading countries worldwide in this field are China and USA, while chemical recycling does not seem to be very popular in Europe. Looking at the number of applications, the leaders among European countries are Germany and Poland, although the number of their applications together is six times smaller than China’s. And if we compare the number of applications across several years, we can see that the largest increase in the number of patent applications occurred in 2020-2022.
Of the recently published inventions, patent application no. EP4133028A1 to TotalEnergies OneTech Belgium is especially interesting. It describes an improved method of producing olefins such as ethylene or propylene through catalytic cracking of olefin fraction and paraffin fraction from the hydrocarbon stream containing pyrolysis oil from plastics. According to the inventors, a part of the improved stream containing paraffins can be further used in the steam cracking process to produce olefins and aromatics for producing further plastics. And in patent applications no. EP4081614A1 and EP4139420A1, to Chevron USA Inc., the inventors propose a continuous process for converting waste plastic in chemical recycling for re-polymerisation of polypropylene/ethylene, while providing circular economy for plastics manufacturing plants. According to invention no. EP4081614A1, “the process involves selecting waste plastics containing polyethylene and/or polypropylene, then passing the waste plastics through a pyrolysis reactor to thermally crack at least part of the polyolefin waste and produce a pyrolyzed effluent”, which is then separated into waste gas, pyrolysis oil containing gasoline/diesel fuel/heavy fraction and biochar. And, pyrolysis oil is directed to a distillation column from which a heavy naphtha fraction or propane-butane is recovered, which is then directed to a steam cracker for ethylene production. Another interesting solution disclosed in application no. EP4139420A1 confirms that the use of fine filtration followed by metal oxide treatment is an effective purification process for improving pyrolysis products for safe processing in refining units.
The development of new technologies and innovation in chemical degradation processes leading to a circular economy can make a significant contribution to the climate neutrality expected from European Union countries as part of the European Green Deal. However, we should bear in mind that due to the growing global problem of excessive plastic production and the huge scale of pollution, including the presence of microplastics in water and food, continuous improvement and development of new methods of recycling plastic products should be one of the goals of all economies, not just in Europe. Finally, what needs to be pointed out is that new chemical recycling technologies make it possible to obtain plastic using traditional systems and facilities and with the same quality as the virgin polymer, including the plastics for contact with food.
Written by: Dr Urszula Gągała and Dr Agnieszka Pazik
