Magneli-Phase Titanium Suboxide Nanocrystals as Highly Active Catalysts for Selective Acetalization of Furfural

Abstract

Alongside TiO2, Magneli-phase titanium suboxide having the composition of TinO2n-1 is a kind of attractive functional materials composed of titanium. However, there still remain problems to be overcome in the synthesis of titanium suboxide; the existing synthesis methods require high temperature typically over 1000 °C and/or post-synthesis purification. This study presents a novel approach to synthesis of titanium suboxide nanoparticles through solid-phase reaction of TiO2 with TiH2. Crystal phases of titanium suboxide were easily controlled by changing TiO2/TiH2 molar ratios in a TiO2-TiH2 mixed precursor and a series of titanium suboxide nanoparticles including Ti2O3, Ti3O5, Ti4O7 and Ti8O15 were successfully obtained. The reaction of TiO2 with TiH2 proceeded at relatively low temperature due to high reactivity of TiH2, giving titanium suboxide nanoparticles without any post-synthesis purification. Ti2O3 nanoparticles and TiO2 were applied as solid acid catalysts for reaction of furfural with 2-propanol. Ti2O3 showed high catalytic activity and high selectivity for acetalization of furfural, while TiO2 showed only poor activity for transfer hydrogenation of furfural. The difference in catalytic properties is discussed in terms of the acid properties of Ti2O3 and TiO2.

Batch and Continuous‐Flow Preparation of Biomass‐Derived Furfural Acetals over a TiO2 Nanoparticle‐Exfoliated Montmorillonite Composite Catalyst

“…Furthermore, acetals derived from furfural and polyols such as propylene glycol and glycerol are considered as potential biofuels and fuel precursors. [11] For the acetalization reactions of furfural and short-chain alcohols, it was usually required high reaction temperature (60-140°C) for pure Lewis acid catalysts, such as NiÀ Al LDH, [12] NiRh/ γ-Al 2 O 3 [13] and titanium suboxide Ti 2 O 3 , [14] whereas room temperature was enough for the Brønsted acid catalysts such as sulfonic cation exchange resin, H 2 SO 4 , HCl, p-toluenesulfonic acid, H 3 PW 12 O 40 , and H 3 PMo 12 O 40 , [10b,15] indicating Lewis acid and Brønsted acid are the two driving forces that can act independently to accelerate the acetalization reactions. Furthermore, it was revealed that the catalytic performance of the catalysts with both Brønsted acid (strong or weak) sites and hard Lewis acid sites was better than that of pure Brønsted acid catalysts.…”

Catalytic Acetalization and Hydrogenation of Furfural over the Light‐Tunable Phosphated TiO2 Catalyst

“…Thus, it is critical to explore the nature and strength of the acid sites in catalysts to obtain the controlled reactivity. Recently, Kamiya et al [6a] . investigated the acetalization and hydrogenation of FUR over the TiO 2 and Ti 2 O 3 in 2‐propanol solvents, respectively.…”

Nonadiabatic Small Polarons Produced by Ti Ions in Granular and Paramagnetic Cr1.8Ti0.2O3+z Particles

“…The same structure is obtained for both extreme cases of the solid solution: Cr 2 O 3 and Ti 2 O 3 . − Cr 2 O 3 is stable and the principal form of chromium oxides. On the other hand, Ti 2 O 3 (Ti 3+ ) is not the most common phase of titanium oxides, like the rutile and anatase, but it is possible to obtain employing the appropriate synthesis conditions. − In addition, titanium has a family of oxides with an intermediate oxidation state of general formula Ti n O 2 n –1 , called Magnéli phase of Ti, and presents a trigonal structure. , Furthermore, the Cr–Ti system can also form Magnéli phases. The family of Cr–Ti oxides with general formula Ti n –2 Cr 2 O 2 n –1 crystallizes in the same structure as the Ti-Magnéli’s phase and presents promising properties for catalysis applications .…”