New Insights on the Oxidation of Unsaturated Fatty Acid Methyl Esters Catalyzed by Niobium(V) Oxide. A Study of the Catalyst Surface Reactivity

Abstract

Abstract:The catalytic properties of niobium(V) oxide (Nb 2 O 5 -CBMN) of different grades: amorphous, optical and ultra-pure, untreated or heat-treated at 400, 500, 700 and 900 • C were studied, before and after interaction with H 2 O 2 , by in situ Raman, FTIR-ATR and diffuse reflectance UV-Visible spectroscopy. The presence of different reaction sites for NbO 7 and NbO 8 type systems, which are directly related to surface defects present in different states of crystallization, were fully characterized. The reactivity of different catalysts obtained from niobium(V) oxide was investigated, using the oxidation of methyl linoleate in the presence of hydrogen peroxide as probe reaction. The reaction was followed by GC-MS, as well as by 1 H and 13 C NMR spectrometry and the dominant product was 9-oxo-nonanoic acid methyl ester. A reaction mechanism related to an auto-oxidation process must be occurring, leading initially to the formation of hydroperoxides, which decompose rapidly via Hock-type rearrangement, leading to the formation of aldehydes.

Fuel Composition Effects on Carbonyls and Quinones in Particulate Matter from a Light-Duty Diesel Engine Running Biodiesel Blends from Two Feedstocks

“…Measurements of exhaust manifold temperature were examined but could not confirm possible differences in peak combustion temperature with fuel blend. n-Hexanal was previously reported as a primary product of methyl linoleate oxidation in the presence of hydrogen peroxide and transition metal catalysts . We also reported n-hexanal, n-nonanal, and other ozonolysis products of FAMEs for B20 biodiesel exhaust PM exposed to ozone .…”

Epoxidation of Karanja (Millettia pinnata) Oil Methyl Esters in the Presence of Hydrogen Peroxide over a Simple Niobium-Containing Catalyst

“…Since the final goal of the present study is to explore the possibility of converting unsaturated FAMEs obtained from karanja oil following an environmentally and economically sustainable approach, we focused our attention onto the use of aqueous hydrogen peroxide, as an oxidant, in the presence of a simple heterogeneous catalyst. For this reason, we moved from titanium(IV)-silica catalysts, that are deeply-studied, although less robust and prone to deactivation when in contact with water-containing media [25][26][27][28], towards niobium(V)-silica systems, which showed promising features in terms of activity, selectivity to epoxides and robustness, also in the presence of aqueous H 2 O 2 [29][30][31][32][33][34][35]. Niobium(V)-containing mesoporous silica catalysts in epoxidation reactions, indeed, comply with the main guidelines of Green and Sustainable Chemistry: they do not require hazardous corrosive reactants, avoiding the use of peroxoacids; they circumvent tedious separation and recovery techniques, thanks to their heterogeneous nature, and, by exploiting the oxidizing properties of hydrogen peroxide, only water and dioxygen, in the case of its decomposition, are formed [36][37][38].…”

Uso de compostos de nióbio como catalisadores na produção de biocombustíveis: uma revisão

“…García-Sancho, Agirrezabal-Telleria, et al, 2014;C. García-Sancho, Rubio-Caballero, et al, 2014;Molina et al, 2015;Tirsoaga et al, 2021), hydrolysis (Campisi et al, 2018;Carniti et al, 2016;Catrinck et al, 2020;Maciel et al, 2020;Nogueira et al, 2020), oxidation (Cecchi et al, 2018;Chagas et al, 2013;Ding et al, 2020;Oliveira et al, 2012;Tran et al, 2019;Wasalathanthri et al, 2019;Wolski, 2020), esterification and transesterification (Câmara & Aranda, 2011;Deshmane et al, 2010;Cristina García-Sancho et al, 2011;Gonçalves et al, 2011;Hoekman et al, 2012;Miranda et al, 2011;Rezende et al, 2019;Singh et al, 2019), isomerization (Carniti et al, 2016;Kitano et al, 2012;Nogueira et al, 2020;Scaldaferri & Pasa, 2019a, 2019bWei et al, 2019), and photocatalytic reactions (Costa et al, 2020;Hashemzadeh et al, 2014;Moraes et al, 2020;Raba-Paéz et al, 2020). In the literature, the niobium compounds most used as catalysts are niobium pentoxide, niobic acid, and niobium phosphate.…”