Ni-activated marble waste nanoparticles for catalyzed pyrolysis of waste cooking oil into hydrocarbon

The activation of marble waste (MW) with nickel (Ni) produced stable nanoparticle catalysts for the pyrolysis of waste cooking oil (WCO). The marble waste, primarily composed of calcite with minor dolomite and quartz, was impregnated with Ni at 5–20 % loadings by weight and then calcined at 550 °C. Pyrolysis of WCO at 380 °C using 5 % Ni/MW achieved a 95 % conversion and 60 % biofuel product, compared to 76 % conversion with unmodified MW. The use of Ni/MW catalysts enhanced the hydrocarbon composition from 60 % to 91.71 % while reducing carboxylic acids from 15 % to 1.17 %. High selectivity for diesel-range hydrocarbons (82.27 %) was observed, with n-C15 contributing 39.97 % of hydrocarbons. The 5 % Ni/MW catalyst efficiently converted WCO into biofuel, sustaining>92 % conversion over four cycles. Ni activation of MW transformed the microcrystalline structure into nanoparticles, increasing surface area and basicity, thus enhancing the efficiency of WCO pyrolysis for hydrocarbon production.