Nb2O5/SBA-15 catalyzed propanoic acid esterification

Abstract

Highlights  Niobium-containing SBA-15 silica used as catalysts for a model reaction to biodiesel production.  High niobium content and high calcination temperature maintained SBA-15 mesoporous silica profile.  Solid evaluated as catalyst with low Nb concentration (2 wt.%) showed better catalytic performance.  Nb promoter effect: catalyst stability at low loadings and also lowest heating treatment.

Tuneable Acidity in Fluorinated Al-SBA-15 Materials for the Esterification of Valeric Acid to Alkyl Valerates

“…Such undesired effect can be explained by the decrease of Brönsted acidity upon the incorporation of niobium that may hinder the access of the reactant molecules to the active sites in the valeric acid esterification existing on the aluminosilicate used as support. These results found for the Nb-based catalyst are contradictory with the results found in the literature (García-Sancho et al, 2017;Silva et al, 2017) for analogous materials but quite consistent with the characterization results.…”

“…Interestingly, mesoporous silicates with SBA-15 structure modified with niobium by conventional methods have been shown to be effective in different esterification reactions, such as propionic acid (Silva et al, 2017) or ricinoleic acid (García-Sancho et al, 2017). Niobium oxide (Nb 2 O 5 ) is expected to form on the silica supports when it is introduced with the precursor (Jehng and Wachs, 1991), leading to the formation of Si-O-Nb bonds that exhibit Brönsted acidity (Xu et al, 2002), an important factor in the activation of both the carboxylic and the alcohol during esterification reaction (Silva et al, 2017). Similarly, the treatment of mesoporous aluminosilicates with ammonium fluoride (NH 4 F) can enhance the acid properties of the synthesized materials (Luque et al, 2005).…”

Furfural Hydrogenation on Modified Niobia

“…One of the most common methods to finely tune the surface acidity of niobia is the addition of a second metal oxide, which can result in the formation of new materials with different chemical and physical features in comparison with the starting materials. Several techniques can be employed in order to obtain the so-called niobia-based mixed oxides, such as hydrothermal synthesis, sol-gel, and co-precipitation techniques [26][27][28][29][30][31]. Nb 2 O 5 -MeO 2 (Me = Zr, Ce and Ti) mesoporous mixed oxide were, for example, prepared by Auroux et al by evaporation-induced self-assembly and applied in the dehydration of fructose [32].…”

A core-shell SO4/Mg-Al-Fe3O4 catalyst for biodiesel production

“…Energy is a key driving force for transportation, technological advancement, and industrialisation and underpins global socioeconomic development [1][2][3]. Biodiesel, comprising fatty acid methyl esters (FAME), is widely recognised as a potential low carbon alternative to fossil fuel derived diesel [4], owing to its low toxicity, eco-friendliness [5,6] and sourcing from non-edible plant and algal oils and animal fats [7][8][9]. Oils from (micro)algae, jatropha seeds, and waste cooking oil (WCO) feedstocks have been used to reduce biodiesel production costs [9][10][11][12][13][14].…”