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[Display omitted] • Catalytic air gasification of plastic waste-derived wax was carried out. • Ni/X-Al 2 O 3 (X = Ti, Sr, or La) catalysts were synthesized to produce H 2 -rich gas. • The use of 10Ni/5Ti-Al obtained the highest gas yield and H 2 selectivity. • Modification of Al 2 O 3 structure by Ti enhanced Ni dispersion and oxygen mobility. • Growing temperature up to 750 °C was conducive to enhancing H 2 selectivity. Catalytic air gasification of plastic waste-derived wax (PW) was performed using Ni/X-Al 2 O 3 (X = Ti, Sr, or La) catalysts to produce H 2 -rich gas for the first time. For this purpose, X-Al 2 O 3 supports were primarily synthesized by doping different promoters into the Al 2 O 3 structure, followed by the loading of Ni. The catalytic performances of prepared catalysts were compared with that of 10Ni/Al, prepared by impregnation of Ni into commercial γ-Al 2 O 3. Compared with using 10Ni/Al, the use of Ni/X-Al 2 O 3 catalysts resulted in higher activity and selectivity, wherein the highest gas yield (74.78 wt%) and H 2 selectivity (25.30 vol%) were achieved using 10Ni/5Ti-Al. Also, the coke yield effectively decreased when using Ni/X-Al 2 O 3 catalysts, particularly 10Ni/5Ti-Al, compared with using 10Ni/Al. These findings are ascribed to the versatile effects of well-dispersed metallic Ni active sites, increased density of Lewis acidic sites at the expense of Brønsted acid sites, and enhanced oxygen transfer capacity of the catalyst owing to Ti addition. Moreover, increasing the concentrations of Ni (up to 10 %) and Ti (up to 5 %) enhanced the catalytic activity and selectivity for H 2 production. Increasing the temperature (up to 750 °C) showed a positive effect on the production of H 2 -rich gas. Furthermore, varying the catalyst-to-feedstock ratio affected the gas yield and H 2 selectivity. [ABSTRACT FROM AUTHOR]