NbF₅–AlF₃ Catalysts: Design, Synthesis, and Application in Lactic Acid Synthesis from Cellulose

Abstract

A series of niobium-modified aluminum hydroxide fluorides (denoted Nb@AlF 3 ), prepared via the fluorolytic sol gel synthesis was investigated for the catalytic one-pot conversion of cellulose to lactic acid. The structure of the new acid catalysts is the result of the dispersion of niobium fluoride in an aluminum fluoride hydroxide matrix. The calcination of the catalysts at a relatively low temperature (350°C) stabilized this structure. Catalytic performances in terms of lactic acid yields are directly correlated with the niobium content.

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb2O5-SiO2-coated magnetic nanoparticles

“…However, to the best of our knowledge, this is the first example of a catalyst affording the selective production of water soluble products, especially leading only to LA and GA. Clearly, this involves a synergetic effect of the active sites corroborated to their dispersion and accessibility to the reactants. Thus, these results are superior to those reported in the literature for the one-pot synthesis of lactic acid [9,10,16] from cellulose, and of glycolic acid [11,30] from glycerol. …”

“…Brought to you by | MIT Libraries Authenticated Download Date | 5/12/18 1:06 AM For the production of lactic acid, the mechanism commonly claimed [16] involves the glucose isomerisation to fructose and retro-aldol condensation of fructose, followed by the triose isomerization to lactic acid. All these reactions are catalyzed by either Lewis acid or base sites.…”

“…In this context, niobium compounds exhibiting both high stability and high acidity (H 0 = − 8.2) in an aqueous medium have attracted great research attention in the past few years [12]. Niobium compounds have been included in investigations of different transformations of the biomass derivatives [13][14][15][16]. However, commercial bulk niobia suffers from poor hydrothermal stability under high-water environment and high temperatures [17].…”

“…In the specific context of the one-pot conversion of cellulose to platform molecules, we recently reported the synthesis and development of highly efficient Nbcontaining hydroxylated AlF 3 catalysts, which can facilitate the depolymerisation of cellulose to α-hydroxy acids (AHAs) as the main products, where the lactic acid is preponderant [16]. The catalytic results confirmed that the active sites responsible for the lactic acid formation are the Nb(V)/Nb(IV) species from the amorphous/crystalline phases, diluted in the aluminum oxide fluoride matrix.…”

Conversion of Cellulose to Lactic Acid by Using ZrO2–Al2O3 Catalysts

“…Therefore, heterogeneous catalysts for the conversion of cellulose to lactic acid are desired because products can be easily separated from this type of catalyst. Several heterogeneous catalysts have been reported to have been reported to have catalytic activity for the conversion of cellulose to lactic acid, such as LaCoO3, NbF5-AlF3, and AlW, which provided yields of lactic acid of 24%, 27%, and 28%, respectively [14][15][16]. However, these solid catalysts have a disadvantage that the metal species leach into solution during the reaction-2.4% of the Co and 1.5% of the La from LaCoO3 [14] and 1.5% of the W from AlW [16] leached into solution.…”