Catalytic upgrading of a model polyethylene pyrolysis oil by hydroconversion over Ni-containing hierarchical Beta zeolites with tailored acidity

Abstract

Valorization of waste polyolefins by a sequential combination of thermal pyrolysis and catalytic hydroconversion over a bifunctional metal/acid catalyst (e.g. zeolite) is an efficient route to produce transportation fuels. However, the zeolite strong acidity typically causes extensive cracking and loss of liquid fuels. In this work, mild dealumination with oxalic acid of a hierarchical Beta zeolite was used to achieve Ni 7%/h-Beta catalysts with Si/Al ratios within the 25 – 130 range. These catalysts were tested in the hydroconversion of a model mixture of LDPE thermal pyrolysis product (1-dodecene/n-dodecane, 50/50 w/w). The highest share of liquid fuels (∼ 90%) was achieved over 7% Ni/h-Beta (SiAl = 130). Besides, due to its high accessibility and tailored acidity, the product contained a meaningful amount of isoparaffins (12%) and a negligible content of olefins (< 3.5%). Thus, this catalyst holds promise for plastic waste hydroconversion towards transportation fuels.