Renewable aromatic hydrocarbons from waste cooking oil over hierarchical imidazole supported zeolites

Abstract

Unlike coal, oil, or natural gas, waste cooking oil (WCO) acts as a renewable source of carbon. It can be converted into energy, fuels, and fine chemicals, instead of being disposed of. This only requires appropriate logistics and a local supply chain network. In such a scenario, WCO can be viewed as a potential feedstock for the production of petrochemicals, particularly critical aromatic platform molecules for high-value chemicals. The study examined, the direct conversion of WCO into aromatic hydrocarbons on an imidazole-supported zeolite (ISZ) catalyst was investigated. The formation of aromatics was found to depend on the pore structure and acidity of the catalyst. The addition of metal oxides over ISZ enhances the Lewis acidic sites, which predominantly enhances the dehydrogenation reaction and yields more aromatic hydrocarbons. In addition, it was found that the average pore size of the catalyst is 6.3 nm, which effectively helps diffuse monoaromatics (C₆–C₈). To investigate the changes occurring on the catalyst surface during the reaction at different temperatures (25–500 °C), surface intermediates and products formed were closely monitored using in situ DRIFTS. Pyro-probe GC-MS study of the model compounds found in WCO showed that the cracking, cyclisation, and dehydrogenation pathway is responsible for the formation of aromatic hydrocarbons. The Zn₂₀Cr₃/ISZ showed excellent stability and good selectivity of C₆–C₈ aromatic species (65.9%) at 430 °C under atmospheric pressure and promise as a suitable catalyst candidate for high yield aromatics from WCO.