2024 AIChE Annual Meeting

(385i) Converting Waste Plastics into Hydrocarbon Products: Exploring the Economic Potential of Hydrocracking Process

Authors

Shi, R., The Pennsylvania State University
Plastics have been integral to human life for more than a century, with their widespread use spanning the globe. They are versatile, flexible, lightweight, and low-cost, which make plastics suitable materials for numerous applications, including packaging, construction, textiles, and more [1], [2]. In 2022, global plastic production was 400.3 million metric tons, marking a 1.6% increase from 2021 [3]. On average, polyolefins constitute 57% of the plastics produced, followed by PVC at 12% , with PET, PUR and PS each accounting for approximately 10% each one [4], mirroring a similar trend in the composition of plastic waste. The increasing rate of plastic production, coupled with the short life span of most plastics, their non-biodegradability nature, and inadequate end-of-life management, have result in the accumulation of plastics in Earth’s soil, water, and air, becoming a persistent environmental challenge.

Currently, the primary method of plastic waste disposal in the USA is landfilling, followed by 9% of plastic incinerated and only 5% recycled [5]. Addressing the challenge of plastic waste management necessitates the development of large-scale recycling technologies. Mechanical recycling involves reprocessing plastic to manufacture new products. However, the properties of plastic degrade in each recycling cycle On the other hand, chemical recycling emerges as a promising alternative that adds value to plastic waste by converting them into a spectrum of chemical compounds, monomers and fuels [6].

Different chemical recycling processes have been studied such as pyrolysis, hydrothermal liquefaction (HTL), solvolysis, hydrogenolysis, hydrocracking and others [7]. Among these, hydrocracking stands out as a well-established process in the refinery industry that has recently gained attention for its efficacy in decomposing plastics, particularly for polyolefins [8], [9], [10]. In hydrocracking, heavy molecules are transformed into lighter molecules through carbon-carbon cleavage, similar to pyrolysis, but under the presence of hydrogen. Noteworthy advantages of hydrocracking include low operation temperatures, high production of alkanes over olefins, and low coke formation. Moreover, hydrocracking yields high-quality liquid oil without the need of several separation steps [11].

The development and adoption of chemical recycling technologies underscore the critical necessity for economic analysis to guarantee their long-term viability at an industrial scale. However, compared to other chemical recycling technologies, only a limited number of studies have reported the techno-economic analysis (TEA) for the hydrocracking of plastic waste [12], [13]. TEA typically employs discounted cash flow analysis to determine metrics such as minimum selling price (MSP) of the desired product, net present value (NPV), internal rate of return (IRR) among others. These indicators serve to evaluate and compare the economic feasibility of the technology. Consequently, we propose to conduct a comprehensive techno economic analysis for the hydrocracking of plastic waste at its early stages, accounting for different scenarios. Specifically, we aim to assess the impact of the catalyst performance (e.g., yield, conversion) and feedstock pricing on the economic viability of hydrocracking. Our goal is to deliver a robust analysis delineating the conditions wherein the chemical recycling process maintains feasibility. This will pave the way for future research efforts to converge effectively, fostering the creation of viable technology.

References

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