Catalytic valorization of wastewater sludge into aviation fuel-range hydrocarbons over Ni, Cu, Co and ZrO2/SAPO-11 catalysts

Abstract

This work presents an innovative valorization strategy for wastewater sludge to produce aviation fuel range hydrocarbons via the catalytic processing of esters, using Ni, Cu, Co, and ZrO 2 -based catalysts supported on SAPO-11 zeolite. Biofuel was produced under two reaction atmospheres (H 2 /N 2 and N 2 ), catalyst loadings (4% and 6%), and feedstock-to-catalyst mass ratios (20:1 and 30:1). The Ni/SAPO-11 demonstrates the ability to catalyze the hydrocarbon chain of C 16 via decarbonylation while cracking heavier C 18+ chains, under reducing conditions; the 4% Ni/SAPO-11 catalyst at a 30:1 ratio (H 2 /N 2 atmosphere) produced 73.8% C 14 -C 16 hydrocarbons, making it ideal for producing aviation fuel components. Using 6%Cu/SAPO-11 enabled biofuel production yields of up to 57%, attributed to copper species that promote hydrogenation and limit excessive cracking. Furthermore, slightly increasing the copper loading improves yield but favors the light (C 8 –C 10 ) and heavy (C 17 –C 20 ) fractions. On the other hand, Co/SAPO-11 and ZrO 2 catalyst showed lower yields of 27% and 24% for both reaction atmospheres and catalyst loading, respectively. These findings demonstrate that transition metals supported on SAPO-11 constitute a favorable platform to produce aviation fuels from wastewater sludge, and that Ni catalyst offers the highest catalytic efficiency and the most favorable hydrocarbon distributions within aviation fuel range.