Oxidative Fast Pyrolysis of High-Density Polyethylene on a Spent Fluid Catalytic Cracking Catalyst in a Fountain Confined Conical Spouted Bed Reactor

Santiago Orozco; Gartzen Lopez; Mayra Alejandra Suarez; Maite Artetxe; Jon Alvarez; Javier Bilbao; Martin Olazar

doi:10.1021/acssuschemeng.2c04552

Oxidative Fast Pyrolysis of High-Density Polyethylene on a Spent Fluid Catalytic Cracking Catalyst in a Fountain Confined Conical Spouted Bed Reactor

ACS Sustain Chem Eng. 2022 Dec 5;10(48):15791-15801. doi: 10.1021/acssuschemeng.2c04552. Epub 2022 Nov 18.

Authors

Santiago Orozco¹, Gartzen Lopez^{1

2}, Mayra Alejandra Suarez¹, Maite Artetxe¹, Jon Alvarez³, Javier Bilbao¹, Martin Olazar¹

Affiliations

¹ Department of Chemical Engineering, University of the Basque Country UPV/EHU, P.O. Box 644, E48080Bilbao, Spain.
² IKERBASQUE, Basque Foundation for Science, 48009Bilbao, Spain.
³ Department of Chemical and Environmental Engineering, University of the Basque Country UPV/EHU, Nieves Cano 12, 01006Vitoria-Gasteiz, Spain.

Abstract

The oxidative fast pyrolysis of plastics was studied in a conical spouted bed reactor with a fountain confiner and draft tube. An inexpensive fluid catalytic cracking (FCC) spent catalyst was proposed for in situ catalytic cracking in order to narrow the product distribution obtained in thermal pyrolysis. Suitable equivalence ratio (ER) values required to attain autothermal operation were assessed in this study, i.e., 0.0, 0.1, and 0.2. The experiments were carried out in continuous regime at 550 °C and using a space-time of 15 g_catalyst min g_HDPE ^-1. The influence of an oxygen presence in the pyrolysis reactor was analyzed in detail, with special focus on product yields and their compositions. Operation under oxidative pyrolysis conditions remarkably improved the FCC catalyst performance, as it enhanced the production of gaseous products, especially light olefins, whose yields increased from 18% under conventional pyrolysis (ER = 0) to 30% under oxidative conditions (ER = 0.1 and 0.2). Thus, conventional catalytic pyrolysis led mainly to the gasoline fraction, whereas light olefins were the prevailing products in oxidative pyrolysis. Moreover, the oxygen presence in the pyrolysis reactor contributed to reducing the heavy oil fraction yield by 46%. The proposed strategy is of great relevance for the development of this process, given that, on one hand, oxygen cofeeding allows solving the heat supply to the reactor, and on the other hand, product distribution and reactor throughput are improved.