Translation. Region: Russian Federation –
Source: Novosibirsk State University – Novosibirsk State University –
A catalytic unit for processing liquid products of polymer waste pyrolysis into synthetic fuel has been installed in the laboratory of the Department of Physical Chemistry of the Faculty of Natural Sciences of Novosibirsk State University. During the first three weeks of its operation, scientists obtained the first three liters of kerosene. At present, optimal operating modes of the capillary reactor are being determined, important catalyst regeneration cycles are being worked out, optimal parameters of the catalytic process are being selected, a catalyst is being selected, the most important performance indicators of the unit are being monitored, and the resulting product is being analyzed.
The equipment was provided to NSU scientists by specialists from Onium Plus LLC (Yaroslavl). They were also involved in the installation of the equipment. Publication about the joint work of scientists from the Department of Physical Chemistry Faculty of Natural Sciences of NSU, the Boreskov Institute of Catalysis of the Siberian Branch of the Russian Academy of Sciences and representatives of this company to create a technology for converting non-recyclable plastic into synthetic fuel was published on the NSU website in December 2023. You can read it by link.
The jointly developed technology consists of several stages. First, non-recyclable plastic undergoes pyrolysis – thermal destruction without oxygen at temperatures from 400 to 600 ° C. The output is pyrolysis oil – a heterogeneous liquid mixture of hydrocarbons containing a large number of undesirable impurities, dark yellow in color with a strong unpleasant odor. Then the multicomponent mixture is divided into fractions based on boiling point. Pyrolysis oil and its fractions are not yet suitable for use as fuel – due to the high content of unsaturated hydrocarbons, this substance can damage internal combustion engines. It can be converted into usable fuel through the use of catalytic technology. Representatives of Onium Plus LLC asked NSU researchers to develop it, who conducted preliminary experiments with nickel-molybdenum catalysts on an aluminum oxide support. The first positive results were obtained using them in tubular reactors – a transparent, colorless liquid with a faint odor of kerosene was synthesized. However, before using it for internal combustion engines, it is necessary not only to develop a new composition and method of catalyst synthesis, but also to modify the hydrogenation plant, select the optimal parameters of the catalytic process, and work out all cycles of automatic catalyst regeneration. For this purpose, the company’s specialists created two more catalytic installations – a pilot and a laboratory. The pilot one is working at the enterprise, and the laboratory one was made available to NSU researchers at the end of May. Parallel trials of the catalytic process are currently underway. NSU scientists select catalyst compositions, process conditions, temperature conditions, pressure, flow rates, and company specialists conduct life tests on an enlarged scale. An important condition of the experiment is that both installations must operate around the clock in a continuous mode.
— The liquid product of plastic waste pyrolysis, which mainly consists of medium and heavy fractions with a large amount of unsaturated hydrocarbons, is fed from the feedstock tank using a high-pressure liquid pump to the mixer, where it is mixed with hydrogen under a pressure of 40 atmospheres. Then the mixture is fed in portions to the reactor, inside which a catalytic reaction occurs under conditions of high pressure and high temperature. Depending on the composition of the catalyst, hydrogenation, hydrocracking or hydroisomerization occurs. At the moment, this is hydrocracking at a pressure of 40 atmospheres and a temperature of 360 – 400 degrees Celsius, which is considered the norm for this process. These parameters are selected depending on what product needs to be obtained. In this case, the task is to obtain kerosene, — said Anton Lysikov, a researcher at the Department of Physical Chemistry of the Faculty of Natural Sciences of Novosibirsk State University, about the device of the installation.
From the reactor, the product mixture enters the separator via a coil, where it cools down and separates into gas and liquid. The gas goes up, and the liquid gradually condenses in the accumulator. When the liquid weight reaches a specified value, it is discharged using the lock method: the first valve of the discharge line is turned on, and the liquid product is poured into the buffer tank. After the weight decrease is recorded, this valve closes and the second one opens, the liquid enters the receiver, and the product yield is assessed in accordance with the scale readings. Then the second valve is also closed until the next sampling. This design with automatic overflow allows to avoid a significant pressure drop when removing products from the process and to accumulate them stably during long-term experiments.
— Our first attempts to process the liquid product of polymer waste pyrolysis resulted in obtaining a substance similar to what we are synthesizing now, only its freezing temperature was about zero degrees Celsius. This figure is much higher than what we intended to achieve. Therefore, we had to select a catalyst composition that would initiate a cracking and isomerization reaction, leading to a strong decrease in the freezing temperature. And now it is already -20 degrees. In three weeks of continuous round-the-clock work, we extracted about 3 liters of high-quality non-freezing kerosene from the pyrolysis product, which can be used as a fuel additive. The production rate is 6 ml per hour, — said Ekaterina Parkhomchuk, Associate Professor of the Department of Physical Chemistry of the NSU Natural Sciences Department.
The finished product undergoes a thorough analysis: researchers study its fractional, group, component and elemental composition. They measure the sulfur and chlorine indicators at the outlet, flash point and turbidity. These parameters are very important for the further use of the final product, they determine its practical purpose.
The first experiments were suggested by NSU scientists to start with widespread and well-known systems: nickel-molybdenum catalysts on an aluminum oxide carrier. They managed to obtain the first positive results.
— We have gained the first experience — we have determined the activity of this catalyst, observed the process, acquired the skill of working with unusual raw materials, and identified the main problem. It is that pyrolysis oil is very different from traditional oil. Most often, such raw materials contain long-chain hydrocarbons and are characterized by a high content of C17 hydrocarbons, which have high freezing and boiling points. They accumulate in the cold zones of the reactor, forming “wax” plugs, due to which pressure drops can occur. Having encountered this problem, we began to select hydrocracking and hydroisomerization catalysts to break long-chain hydrocarbons into smaller molecules, making them branched. This allowed us to solve the problem of reactor waxing, as well as reduce the freezing and turbidity temperatures of the product, and at the output we received higher quality and flammable hydrocarbons, — explained Ekaterina Vorobyova, a postgraduate student of the Department of Physical Chemistry of the Faculty of Natural Sciences of NSU.
First, a hydrogenation catalyst was obtained, then a hydroisomerization and hydrocracking catalyst, on which the first positive results were obtained: the cloud point began to decrease significantly, hydrocarbons began to burn differently. Now scientists are working on a catalyst with increased activity in hydrocracking and hydroisomerization, while obtaining a product with a cloud point below -20. It is important to note that this is its stable operation for several hundred hours. But the most important thing is that products were obtained that flash and burn as needed, hydrogenation and hydrocracking processes are underway, the products contain a large number of isomers, which is required to obtain synthetic motor fuels and oils.
The installation with the new catalyst has been operating continuously for almost four weeks, and the catalyst activity has not been lost, no pressure drops have been observed, and no coking has occurred.
— The main thing is that while developing this technology, we continue to improve our skills in working with this special raw material, which is so different from oil. For us, this is a very interesting task, since plastic waste is really growing. And not all of it is recyclable. Burying it in landfills is not a solution to the problem. For me, from a scientific point of view, it is interesting to identify the features of processing this raw material, as well as the requirements for the properties of the catalyst, which will allow us to stably and for a long time obtain high-quality motor fuels and oils from non-recyclable waste into valuable fuel, — said Ekaterina Vorobyova.
Scientists assess the results of their work as encouraging, and the production of fuel from pyrolysis products as profitable, because only 5% of the original substance turns into gas, the rest of the mass turns into high-quality synthetic fuel. At the moment, this technology can be considered almost ready for implementation, which will be determined only by the speed of construction of catalytic units. The main difference between production samples and a laboratory unit is the number of reactors. In a laboratory unit, there is one reactor, and in industrial ones, it is theoretically possible to install hundreds and even thousands. Then the productivity will increase many times over.
— Each type of catalyst or new parameters, before being implemented, requires thousands of running hours. The more parallel tests, the faster the process optimization and confirmation of the success of certain solutions. By the end of the year, we will put into operation two additional laboratory units for hydrogenation, increasing the number of simultaneously running processes. But the most interesting task, in our area of responsibility, which we are currently implementing, is the creation of a pilot unit with dozens of micro reactors simultaneously. This module will allow the process to be carried out with a capacity of liters per hour. All systems will be integrated in it, as in a “large” plant. It is equipped with its own hydrogen source, its own hydrogen purification and recompression unit and an automatic regeneration system. In addition to confirming the readiness of the catalytic system for industrial use, this device will also confirm the economic aspects of fuel production. The cost of the process will be very accurately determined, which is necessary for further industrial implementation, — explained Alexander Klimov, a representative of the company OOO Onium Plus.
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