A heterogeneous catalytic process to mitigate the acidity of bio-oils caused by the presence of volatile organic acids

[Display omitted] •Catalytic processes to upgrade bio-oil to use it as a co-feeding in oil refineries.•Ag nanoparticles smaller than 4 nm were obtained as catalysts.•The catalyst was tested in a batch reactor at 200 °C, achieving a conversion higher than 95%.•The elimination of acetic acid took place via adsorption and ketonization mechanisms.•The presence of Ag promotes the reaction towards aldo-condensation products. The removal of the acidity produced by the presence of volatile organic acids in bio-oils, such as acetic acid, assisted by heterogeneous catalysts was investigated. For this purpose, CaO and alumina-supported catalysts were prepared, and silver nanoparticles were used as promoter. The prepared catalysts, both fresh and post-reaction, were characterized by several techniques: N2 physisorption (BET), SEM-EDS, TEM, XRD, and TPR. All catalysts were tested in the elimination of acetic acid, employing two different reaction systems: batch microreactors and a pressurized batch reactor. An appreciable CH3COOH elimination of ~60%–70% was obtained at low temperature (150–200 °C) using the CaO-Al2O3 system. The addition of silver improved the removal percentage. Silver-supported catalysts were also tested in a pressure-controlled system, achieving an excellent percentage of acetic acid removed (~97.5%). Silver would promote the incipient reactions of catalytic ketonization and aldol condensation.