title: Inhibition of palm oil oxidation by zeolite nanocrystals.
abstract: The efficiency of zeolite X nanocrystals (FAU-type framework structure) containing different extra-framework cations (Li(+), Na(+), K(+), and Ca(2+)) in slowing the thermal oxidation of palm oil is reported. The oxidation study of palm oil is conducted in the presence of zeolite nanocrystals (0.5 wt %) at 150 °C. Several characterization techniques such as visual analysis, colorimetry, rheometry, total acid number (TAN), FT-IR spectroscopy, (1)H NMR spectroscopy, and Karl Fischer analyses are applied to follow the oxidative evolution of the oil. It was found that zeolite nanocrystals decelerate the oxidation of palm oil through stabilization of hydroperoxides, which are the primary oxidation product, and concurrently via adsorption of the secondary oxidation products (alcohols, aldehydes, ketones, carboxylic acids, and esters). In addition to the experimental results, periodic density functional theory (DFT) calculations are performed to elucidate further the oxidation process of the palm oil in the presence of zeolite nanocrystals. The DFT calculations show that the metal complexes formed with peroxides are more stable than the complexes with alkenes with the same ions. The peroxides captured in the zeolite X nanocrystals consequently decelerate further oxidation toward formation of acids. Unlike the monovalent alkali metal cations in the zeolite X nanocrystals (K(+), Na(+), and Li(+)), Ca(2+) reduced the acidity of the oil by neutralizing the acidic carboxylate compounds to COO(-)(Ca(2+))1/2 species.
authors.affiliation: †School of Chemical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: Kok-Hou
authors.initials: KH
authors.lastname: Tan
authors.forename: Hussein
authors.initials: H
authors.lastname: Awala
authors.affiliation: §Division of Inorganic and Physical Chemistry, Institut Teknologi Bandung, Bandung, Indonesia.
authors.forename: Rino R
authors.initials: RR
authors.lastname: Mukti
authors.affiliation: ⊥National Institute of Education, Nanyang Technological University, Singapore.
authors.forename: Ka-Lun
authors.initials: KL
authors.lastname: Wong
authors.forename: Baptiste
authors.initials: B
authors.lastname: Rigaud
authors.affiliation: #Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Tau Chuan
authors.initials: TC
authors.lastname: Ling
authors.affiliation: ΔFaculty of Chemistry and Pharmacy, University of Sofia, Sofia, Bulgaria.
authors.forename: Hristiyan A
authors.initials: HA
authors.lastname: Aleksandrov
authors.affiliation: ΔFaculty of Chemistry and Pharmacy, University of Sofia, Sofia, Bulgaria.
authors.forename: Iskra Z
authors.initials: IZ
authors.lastname: Koleva
authors.affiliation: ΔFaculty of Chemistry and Pharmacy, University of Sofia, Sofia, Bulgaria.
authors.forename: Georgi N
authors.initials: GN
authors.lastname: Vayssilov
authors.forename: Svetlana
authors.initials: S
authors.lastname: Mintova
authors.affiliation: †School of Chemical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: Eng-Poh
authors.initials: EP
authors.lastname: Ng
mesh_terms: D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D000073878:Palm Oil; D010938:Plant Oils / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D017641:Zeolites / Q000737:chemistry*
chemical_list: D010938:Plant Oils; D017641:Zeolites; D000073878:Palm Oil
keywords: extra-framework cations; inhibition; oxidation; palm oil; zeolite nanocrystals