Thermal degradation of waste plastics in a two-stage pyrolysis-catalysis reactor over core-shell type catalyst

•A two-stage pyrolysis-catalysis reactor was used to convert plastics into hydrogen.•Ni-Ce based catalyst showed great catalytic activity for H2 production.•Ni-Ce@SiO2 catalysts with different shell thickness were investigated.•The core-shell catalyst exhibited great stability during 5 times of reuse. A core-shell type catalyst was applied to convert polyethylene (PE) plastic wastes into hydrogen using a two-stage pyrolysis-catalysis reactor. The effects of catalyst: plastic ratio, reaction temperature, and the suppression of coke formation on catalytic performance were investigated. Ni-Ce bimetallic catalyst was synthesized via modified polyol method, and the silica coating with different Ni:Si molar ratio was prepared with the extension of Stöber method. Different thickness of silica shell was synthesized and tested for hydrogen production from PE waste. The encapsulation of Ni-Ce core by silica shell could effectively inhibit the sintering of nanoparticles under high temperature conditions. The highest amount of hydrogen production was found when the catalyst: plastic weight ratio was 1.0, and the catalytic reaction temperature was 800 °C. The core-shell catalyst also exhibited great ability of coking resistance, showing great catalytic performance within 5 times of reuse.