Pyrolysis-catalytic gasification of plastic waste for hydrogen-rich syngas production with hybrid-functional Ni-CaO Ca2SiO4 catalyst

The production of H 2 -rich syngas from pyrolysis-catalytic gasification of plastic waste bottles has been investigated. The hybrid-functional materials consisting of Ni as catalyst, CaO as CO 2 sorbent and Ca 2 SiO 4 as a polymorphic active spacer were synthesized. The different parameters (Ni loading, temperature, N 2 flow rate and feedstock-to-catalyst ratio) have been investigated to optimise the H 2 production. The catalysts were analysed by N 2 physisorption, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Temperature-programmed reduction (TPR) and in-situ Transmission Electron Microscopy (TEM). Temperature-programmed oxidation (TPO) was used to analyse the carbon formation on the used catalysts. The highest H 2 production of 59.15 mmol g -1 of plastic was obtained in the presence of a catalyst with 20 wt.% Ni loading, which amounts to H 2 purity as high as 54.2 vol% in gas production. Furthermore, 90.63 mmol g -1 of plastic of syngas was produced by increasing the feedstock-to-catalyst ratio to 4:1, yielding 84.4 vol.% of total gas product (53.1 vol.% of H 2 and 31.3 vol.% of CO, respectively). The Ni-CaO Ca 2 SiO 4 hybrid-functional material is a very promising catalyst in the pyrolysis-catalytic gasification process by capturing CO 2 as it is produced, therefore shifting the water gas shift (WGS) reaction to enhance H 2 production from plastic waste. Detailed elucidation of the roles of each component at the microscale during the catalytic process was also provided through in-situ TEM analysis. The finding could guide the industry for future large-scale application to convert abundant plastic waste into H 2 -rich syngas, therefore contributing to the global ‘net zero’ ambition.