Processing of polyethylene into hydrocarbon fuels by catalytic cracking on Pillared Inter Layered Clays (PILC)

Resource conservation is an integral part of environmental protection. According to data (https://www.vtorma.ua/ru/utilizatsiya-musora-na-poligonah-tbo/) in 2018, more than 9 million tons of household waste were generated in Ukraine. Currently, improper use of resources has led to significant environmental pollution. One of the significant environmental problems of the urbanized areas of megacities are the storage areas of household and industrial waste, which are a potential source of environmental disaster. One of the effective ways to solve this problem is the pyrolysis of plastic waste of various origins.Synthetic liquid fuels (SLF) are complex mixtures of hydrocarbons obtained from raw materials of non-petroleum origin. One of the ways of obtaining SJT is the thermal conversion of raw materials without the participation of oxygen or air (cracking, pyrolysis) to obtain solid, liquid and gaseous products. The liquid product is pyrolysis oil, which is used directly or processed into furnace fuel, individual chemicals and other products. The main factor affecting the speed of pyrolysis and the yield of products is the temperature of the process. Depending on the temperature of the process, low-temperature (up to 673K), medium- temperature (673-873K) and high-temperature (above 873K) are distinguished. The yield of products is also influenced by the presence and selection of a catalytic system, with the help of which the ratio of gaseous and liquid products in the final mixture can also be adjusted. Despite the huge number of works on obtaining liquid fuel, the task of using effective catalytic systems that ensure high product yield in combination with the environmental friendliness of the cracking process and simplified technology for obtaining catalysts remains relevant [1-3]. The results of research on processing by joint pyrolysis of a mixture of polyethylene in the presence of modified aluminosilicates for the purpose of obtaining liquid transport and boiler fuels, as well as chemical raw materials used in the main organic synthesis, are considered in the submitted report. The paper developed a method for obtaining columnar microporous sorbents (PILC) based on calcium forms of montmorillonite and stevensite using more concentrated solutions and dispersions of reagents. Catalytic cracking of polyethylene on modified montmorillonite and saponite and their regenerated samples in a semi-batch reactor was studied. Columnar clays are capable of almost completely converting polyethylene into gaseous and liquid hydrocarbons, showing a low coking level. The selectivity and yield of liquid hydrocarbons were high, since the mild acidity of the columnar clays allowed to avoid excessive cracking to small molecules. The regenerated catalyst samples showed little loss in conversion rate and selectivity with fresh clay samples (se? Tab. 1). In addition, they gave hydrocarbons with almost the same distribution as fresh samples, which confirms the possibility of complete regeneration of columnar clays. Both the high yield of liquid products and the ability to regenerate make PILCs potential catalysts for industrial use. In addition, they gave hydrocarbons with almost the same distribution as fresh samples, which confirms the possibility of complete regeneration of columnar clays. Both the high yield of liquid products and the ability to regenerate make PILCs potential catalysts for industrial use. The influence of the heating rate on the quality and distribution of the liquid product using different heating temperatures is also investigated. This result shows the importance of the state of the polymer at each stage of the pyrolysis process.
Conclusions: Considering the importance of catalytic cracking of plastic waste into fuel, two aluminum pillared clays, PILC-M, a saponite derivative, and PILC-S, a montmorillonite derivative, were tested for their effectiveness in the catalytic cracking of polyethylene, as well as their efficiency. At low temperatures, clay catalysts showed low activity. However, this pattern changes dramatically with temperature, as PILCs are able to completely decompose polyethylene after increasing the process temperature. In addition, they have achieved high levels of liquid hydrocarbon fuel formation. The yield of liquid products is more than 70%. Such a high yield of liquid from columnar clays is explained by their weak acidity, which does not withstand excessive cracking to small molecules, and is also reflected in the distribution of the liquid product. In addition, columnar clays give products that are mostly in the boiling range of motor fuels. In addition to the high liquid yield, the low coke yield found in the catalytic cracking of plastic waste on columnar clays makes these materials promising candidates for a future commercial process. In addition, the regenerated columnar clays after burning the formed coke showed almost the same behavior as their fresh counterparts in terms of conversion and yield, as well as product distribution. The ability to regenerate PILC increases their potential for successful introduction into the commercial process of cracking plastic waste.