Local Induction Heating Capabilities of Zeolites Charged with Metal and Oxide MNPs for Application in HDPE Hydrocracking: A Proof of Concept.

Marta Muñoz,Cátia S Costa,Belén Torres,Irene Morales,Patricia De La Presa,João M Silva,Jose M Alonso,Maria Do Rosário Ribeiro,Joaquín Rams,Marta Multigner

doi:10.3390/ma14041029

Abstract

Zeolites are widely used in high-temperature oil refining processes such as fluid catalytic cracking (FCC), hydrocracking, and aromatization. Significant energy cost are associated with these processes due to the high temperatures required. The induction heating promoted by magnetic nanoparticles (MNPs) under radio frequency fields could contribute to solving this problem by providing a supplementary amount of heat in a nano-localized way, just at the active centre site where the catalytic process takes place. In this study, the potential of such a complementary route to reducing energetic requirements is evaluated. The catalytic cracking reaction under a hydrogen atmosphere (hydrocracking) applied to the conversion of plastics was taken as an application example. Thus, a commercial zeolite catalyst (H-USY) was impregnated with three different magnetic nanoparticles: nickel (Ni), cobalt (Co), maghemite (γ-Fe2O3), and their combinations and subjected to electromagnetic fields. Temperature increases of approximately 80 °C were measured for H-USY zeolite impregnated with γ-Fe2O3 and Ni-γ-Fe2O3 due to the heat released under the radio frequency fields. The potential of the resulting MNPs derived catalyst for HDPE (high-density polyethylene) conversion was also evaluated by thermogravimetric analysis (TGA) under hydrogen atmosphere. This study is a proof of concept to show that induction heating could be used in combination with traditional resistive heating as an additional energy supplier, thereby providing an interesting alternative in line with a greener technology.

Highlights

IntroductionPlastic production increased by more than 20-fold from 1964 to 2018 with an annual output of 359 Mt, [1]
Hydrocracking technology has been recognized as a very promising solution for managing plastic waste since it allows plastic feedstock to be converted into valuable products, removing heteroatoms that may exist in waste plastic, reducing the amount of olefins and aromatics in the final products, and reducing the coke precursors responsible for the catalyst deactivation in one single process [4,5]
We extended our previous studies to other magnetic nanoparticles (MNPs), single or combined with γ-Fe2 O3, with the aim of introducing new metal centers that may combine catalytic and ferromagnetic properties for potential applications in the catalytic conversion of highdensity polyethylene (HDPE) under hydrogen atmosphere

Summary

Introduction

Plastic production increased by more than 20-fold from 1964 to 2018 with an annual output of 359 Mt, [1]. This value is expected to reach 18,000 Mt in 2050 [2]. The hydrocracking catalysts are bifunctional, comprising an acidic function responsible for the cracking and isomerization reactions, and metal centers where hydrogenation-dehydrogenation reactions take place [6]. Zeolites are by far the most applied materials because they have unique properties: high thermal stability, high strength and number of acidic sites, high external surface area, and an unequalled pore channel system, all of which make them suitable catalysts for plastic conversion [7,8,9,10,11]. The metallic function is usually represented by a noble metal (palladium or platinum), a non-noble metal of group VI-A (molybdenum or tungsten) or group VIII-A (cobalt or nickel), according to the periodic table [5]

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Discussion

Conclusion