Heterogeneous acid catalyst preparation from olive pomace and its use for olive pomace oil esterification

Solid acid catalyst was produced from olive pomace (OP), characterized and used for the esterification of OP oil. OP was pyrolyzed, physical activated by steam and sulfonated using sulfuric acid. Commercial, coconut husk-based, activated carbon (CHAC) was also sulfonated for comparison. The activation has shown a significant increase in olive pomace activated carbon (OPAC) surface area by developing simultaneously its micro and meso-porosity. The sulfonation has further increased OPAC BET surface area to reach 618.18 m(2)/g and has changed its structure to become microporous. Sulfonation also removed tar residues and aliphatic hydrocarbons from OPAC's surface. Tendencies observed with carbon CHAC, used for comparison, are slightly different with a mesoporosity development. Although its higher surface area (1227.01 m(2)/g), CHAC has fixed three times less sulfur than OPAC, which can be attributed to its higher hydrophobicity or pore distribution. Sulfur was mainly fixed in the form of sulfonic acid (SO3H). Esterification with methanol using produced solid catalysts decreased OPO acidity below the 2 mgKOH/g threshold after 5 h of reaction and reduced mono, di and triglycerides to levels close to the ones required by European norm EN14214. (C) 2020 Elsevier Ltd. All rights reserved.