Selective Oxidative Upcycling of Polyethylene Pyrolyzed Wax to High‐Performance Surfactants Using Synthesized Co and Mn–Co Stearate Catalysts
Abdul Aziz Jallow, Usman Bello, Muhammad Faizan, Roa'a H. Alzoubi, Maryem Ourimi, Abdul Gani Abdul Jameel, Usama Ahmed, Mohammad Nahid SiddiquiABSTRACT
In this work, post‐consumer low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) were converted into surfactant‐grade materials using a two‐step process involving controlled pyrolysis and catalytic oxidation. Low‐viscosity hydrocarbon waxes (approximately 30% yield) were recovered through pyrolysis at 500°C under nitrogen flow. Subsequently, they were oxidized at 150°C for 8 h using monometallic cobalt stearate Co(C 18 H 35 O 2 ) 2 and bimetallic manganese‐cobalt stearate Mn 5 Co(C 18 H 35 O 2 ) 12 catalysts synthesized via coprecipitation. Fourier transform infrared spectroscopy (FT‐IR), 13 C nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM) were used to identify the functional, structural, and morphological characteristics of the wax, oxidized wax, and carboxylic acid extract, respectively. Gas chromatography‐mass spectrometry (GC–MS) was used to analyze the chemical composition of the wax, while the molecular structure of the carboxylic acid extracts was determined using 1 H NMR. Moreover, the formation of aldehyde functionality was confirmed by FT‐IR, supporting the proposed radical‐mediated oxidation mechanism. Following neutralization with potassium hydroxide (KOH), carboxylate surfactants were obtained and evaluated for their critical micelle concentration (CMC), surface tension at the CMC (γ cmc ), maximum surface excess (Γ max ), minimum area per molecule (A min ), foam stability, and solubility in deionized water and seawater, respectively.