Scientists from NSU have patented a method for producing a catalyst for processing plastic waste into motor fuel

A patent for a method of preparing a catalyst for processing pyrolysis oil from mixed plastic waste into high-quality kerosene and diesel fractions has been obtained by a team of researchers from the Department of Physical Chemistry at the Faculty of Natural Sciences of Novosibirsk State University (FEN NSU) and the Boreskov Institute of Catalysis of the Siberian Branch of the Russian Academy of Sciences. The development has successfully passed tests in laboratory conditions and is being implemented in the production of the company OOO “Onium Plus” (Moscow). It has no analogues on the market and differs significantly from catalysts used in the processing of typical petroleum feedstock.

— Pyrolysis oil is characterized by an increased content of unsaturated hydrocarbons — alkenes and aromatic hydrocarbons. Processing such raw materials using catalysts similar to those used in oil refining is challenging: substances of different classes behave differently, especially when they are in complex mixtures like the products of plastic waste pyrolysis. Our task was to create a catalyst that, first, would facilitate the dewaxing process: without such treatment, fuels derived from pyrolysis oil cause carbon deposits on engine parts, leading to rapid failure of the mechanism. To avoid this, unsaturated hydrocarbons must be converted into saturated paraffins by selecting an appropriate catalyst. Second, to prevent fuel from freezing at low temperatures, it is necessary to minimize its cloud point and pour point — this is achieved by isomerizing hydrocarbons present in the diesel and kerosene fractions.Thirdly, the catalyst should not cause a significant change in the fractional composition, since the pyrolysis oil itself already falls within the boiling temperature range characteristic of kerosene and diesel fuels. To ensure that our catalyst possesses all three of these properties, we have developed a group of catalysts capable of converting pyrolysis oil into motor fuel depending on its composition., — explained the assistant of the Department of Physical Chemistry of FEN NSU, graduate student of NSU, junior researcher at the Institute of Catalysis of the SB RAS Vsevolod Vdovichenko.

Structurally, the new catalyst is close to the classical ones: it includes a hydrogenating metallic component, as well as a zeolite that ensures isomerization and allows the material to be formed as a powder with particles of a certain size — depending on the specific reactor in which the catalyst will be used. Scientists tested various zeolites with three-dimensional and one-dimensional channel structures in the processing of pyrolysis oil. During the experiments, it was found that the use of one-dimensional zeolite ZSM-23 significantly improves low-temperature properties and approaches the criteria (and even surpasses them in some parameters) required by the standards for aviation kerosene — aviation fuel Jet A-1.

Currently, a patent has been obtained for a method of producing composite catalysts containing aluminum oxide and zeolite, and a decision is pending on the application for the composition of catalysts and their use in catalytic processing of plastic waste.

— Plastic waste is processed in various ways. There are two main approaches: pyrolysis followed by catalytic processing, and pyrolysis with a catalytic layer. In the first case, the processing occurs in two sequential stages; in the second — both processes are combined. The second approach is more complex in practical implementation. Two-stage processing, which involves conducting pyrolysis and catalytic processing separately from each other, is technically much simpler and more accessible, and moreover, it is controllable in terms of the resulting product. Our industrial partner chose exactly this path. While in typical laboratory reactors the tube diameter is usually about an inch, and in industrial oil refineries it can reach several meters, at OOO “Onium Plus” they decided to take a different route. To further simplify the process, catalytic processing is carried out in thin reactors, increasing productivity not by diameter but by their quantity. In our laboratory, small-diameter tubes were used — from 2 mm to 1 cm. Catalyst particles must be of the corresponding size — from 0.2 to 1 mm.Our main task was to obtain durable catalyst particles that would not be subject to significant wear, leading to the accumulation of unwanted dust during the processing of pyrolysis products from plastic waste., — said an employee of the Department of Physical Chemistry of FEN NSU, junior researcher at the Boreskov Institute of Catalysis SB RAS, Candidate of Chemical Sciences Ekaterina Vorobyova.

Scientists proposed several methods for preparing catalysts, including conventional granulation, crushing extrudates with sieving to select the required fraction size, and spray drying. The possibility of using pore-forming templates to create catalysts more resistant to deactivation was considered. Methods for applying the active component without the risk of damaging the fraction or altering the particle size of the catalyst were also developed. The main problem was solved — increasing the strength of the catalyst, which is prone to abrasion due to the small diameter and considerable length of the tubular reactor. A reliable solution to this problem was found and patented.

This catalyst was developed for model feedstock, which is a mixture of polyethylene and polypropylene provided by the company Oniyum Plus LLC. Now scientists need to adapt it to work with real feedstock, also prepared and sent to the laboratory by the industrial partner. This is pyrolysis oil obtained from plastic waste taken from a city landfill and subjected to thermal processing on a multi-ton industrial pyrolysis unit. Its composition differs significantly from the model feedstock, so the previously developed catalyst is no longer suitable for the real feedstock. However, having worked out the process on the model feedstock, scientists have gained a fairly clear understanding of how to set up a similar process for the real feedstock and what the catalysts for it should be.

— It is impossible to develop a universal catalyst for the processing of pyrolysis products of plastic waste. The composition, preparation methods, testing conditions, and application of the catalyst directly depend on the specific raw material we have to work with and the particular purpose for which we use this process. The raw material changes each time depending on the installation where the pyrolysis oil is produced, as well as on the type of waste and kind of plastic loaded into it. The requirements for the final product are also taken into account depending on its type — it could be aviation kerosene or a fuel additive. Without working with model raw materials and conducting long continuous tests, it is impossible to select and produce a catalyst even for the simplest “real” raw material., — explained the head of the Department of Physical Chemistry of the Faculty of Natural Sciences of NSU, head of the template synthesis group at the ISC SB RAS, Candidate of Chemical Sciences Ekaterina Parkhomchuk.

Mutually beneficial cooperation between scientists and representatives of the real economic sector will continue in the new stage of research aimed at selecting and creating a new catalyst. Beginning their joint work over two years ago, the company OOO “Onium Plus” provided researchers with two reactors for catalytic testing. Students carry out research using these reactors as part of their thesis work, and postgraduate students also use this equipment.

— We are pleased to have established effective collaboration between representatives of the real economy sector and our scientists, students, and postgraduates at NSU, who combined efforts, expertise, and knowledge to establish such a technologically complex and science-intensive process as catalytic processing of pyrolysis products from plastic waste. Since both the raw materials and the processing methods vary significantly from batch to batch and depend on the reactor in which the process was carried out, it will be necessary to respond promptly to these changes by modifying the catalyst composition. Making these adjustments in large-scale production is very difficult, but in small laboratories and pilot plants under the guidance of scientific staff, it is quite possible. Therefore, the catalyst we developed will be produced in a pilot laboratory specially created for this purpose, which will be equipped with all necessary equipment by the industrial partner. This laboratory will be established as part of the construction of a modern NSU campus and will be located in the new NSU research center. — said Ekaterina Parkhomchuk.