sustainability Article Performance of Different Catalysts for the In Situ Cracking of the Oil-Waxes Obtained by the Pyrolysis of Polyethylene Film Waste Lucía Quesada *, Mónica Calero de Hoces *, M. A. Martín-Lara , Germán Luzón and G. Blázquez Department of Chemical Engineering, University of Granada, 18071 Granada, Spain; marianml@ugr.es (M.A.M.-L.); german@ugr.es (G.L.); gblazque@ugr.es (G.B.) * Correspondence: lucia9s@ugr.es (L.Q.); mcaleroh@ugr.es (M.C.d.H.); Tel.: +34-958-244075 (L.Q.); +34-958-243315 (M.C.d.H.) Received: 5 June 2020; Accepted: 5 July 2020; Published: 7 July 2020   Abstract: Currently, society is facing a great environmental problem, due to the large amount of plastic waste generated, most of which is not subjected to any type of treatment. In this work, polyethylene film waste from the non-selectively collected fraction was catalytically pyrolyzed at 500 ◦ C, 20 ◦ C/min for 2 h, in a discontinuous reactor using nitrogen as an inert gas stream. The main objective of this paper is to find catalysts that decrease the viscosity of the liquid fraction, since this property is quite meaningful in thermal pyrolysis. For this purpose, the three products of catalytic pyrolysis, the gaseous fraction, the solid fraction and the liquid fraction, were separated, obtaining the yield values. After that, the aspect of the liquid fraction was studied, differentiating which catalysts produced a larger quantity of waxy fraction and which ones did not. The viscosity of these samples was measured in order to confirm the catalysts that helped to obtain a less waxy fraction. The results showed that the zeolites Y and the zeolites β used in this study favor the obtaining of a compound with a smaller amount of waxes than for example catalysts such as FCC, ZSM-5 or SnCl 2 . Keywords: plastic waste; pyrolysis; catalyst; zeolites; viscosity; wax 1. Introduction Plastics play an important role in the daily life of humans since there is a strong dependence on these materials. This dependence can be justified by the advantages that these materials have over others, due mainly to their lightness and cost. These materials are strategic in sectors such as packaging, construction, motoring, electronics or agriculture, among others [1]. As countries’ economies grow the demand for plastic goods increases. In 2018, the global production of plastics was around 360 million tons, of which Europe generated 17%, corresponding to 62 million tons. In addition, in 2018 Europe transformed 51.2 million tons (European converts demand) and Spain was among the six countries that cover 80% of European demand, with 7.6% of the transformation [1]. This high demand for plastics can only lead to a large production of solid plastic waste, which occupies a large part of the municipal solid waste (MSW). In 2018, 29.1 million tons of plastic were collected as post-consumer waste. Of this plastic, 32.5% was recycled, 42.6% was used for energy recovery and 24.9% ended up in landfills. However, in Spain the rate of landfill is relatively large with respect to the rest of the European countries, at 39% [1]. These high values of deposition in landfills and energy recovery, both for developed and underdeveloped countries, give rise to numerous concerns, both health-related and environmental [2]. Sustainability 2020, 12, 5482; doi:10.3390/su12135482 www.mdpi.com/journal/sustainability