Desulfurization of Liquid Hydrocarbon Fuels Using Food Waste Activated Carbon

Sulfur compounds present in crude oil contribute to air pollution, acid rain, and ozone depletion when sulfur-contaminated hydrocarbons are combusted in engines. Increasingly stringent environmental legislation limits sulfur concentrations in fuels; however, current methods used in refineries cannot meet these requirements without high energy and material costs. Simultaneously, food waste is a significant environmental problem that requires management solutions. The objective of this research was to convert food waste into activated carbon to investigate sulfur removal capabilities from fuels and to compare food waste activated carbons to more commonly studied uniform precursors to activated carbons such as walnut shells. Few previous studies examine food waste as a precursor to activated carbons for the removal of dibenzothiophenes (DBT) from fuels. Food waste and walnut shells were each pyrolyzed and physically activated with steam. Copper nitrate (5%, 1%, 0.25% weight (wt.)) was added to food waste prior to pyrolysis to study the effects of metal precursors on sulfur adsorption capacities for improved selectivity while limiting production steps. Pyrolysis (650°C for 2h) and activation (950°C for 4h) conditions were chosen to maximize the biochar yield and activated carbon microporosity. 0.25%wt. of copper nitrates resulted in the greatest amount of dispersion of copper on the biochar and was selected for activation. Computational studies showed that copper on carbon contributes to greater selectivity of DBT over naphthalene. Food waste activated carbons (3.0 mg S/g adsorbent) and 0.25%wt. food waste activated carbons (2.5 mg S/g adsorbent) were found to remove more sulfur than walnut shell activated carbons (2.0 mg S/g adsorbent) when all achieved similar yields after activation. This research demonstrates the promise of food waste activated carbons to offer a green solution for removing sulfur from fuels.