Niobium pentoxide nanomaterials with distorted structures as efficient acid catalysts

Abstract

Niobium pentoxides are promising acid catalysts for the conversion of biomass into fuels and chemicals. Developing new synthesis routes is essential for designing niobium pentoxide catalysts with improved activity for specific practical processes. Here we show a synthesis approach in acetophenone, which produces nanostructured niobium pentoxides with varying structure and acidity that act as efficient acid catalysts. The oxides have orthorhombic structures with different extents of distortions and coordinatively unsaturated metal atoms. A strong dependence is observed between the type and strength of the acid sites and specific structural motifs. Ultrasmall niobium pentoxide nanoparticles, which have strong Brønsted acidity, as well as Lewis acidity, give product yields of 96% (3 h, 140°C, 100% conversion), 85% (3 h, 140°C, 86% conversion), and 100% (3 h, 110°C, 100% conversion) in the reactions of furfuryl alcohol, 5-(hydroxymethyl)furfural, and α-angelica lactone with ethanol, respectively.

Formation and growth mechanism for niobium oxide nanoparticles: atomistic insight from in situ X-ray total scattering

“…For example, in 1973 IIjima showed the presence of blocks of different sizes assigned as heavily disordered regions in the H-Nb2O5, 54 and several studies conducted in the 1970s show similar imperfections in the block structure of Nb2O5. [55][56][57] More recently, Russo et al 8 showed that T-Nb2O5 nanoparticles synthesized through solvothermal synthesis with NbCl5 and acetophenone have regions deviating from the crystalline nature of the material. Figure 4 shows an illustration of the type the expected defects found in niobium oxide particles compared to the idealized H-Nb2O5 structure.…”

“…fuels and chemicals from biomass sources. [8][9][10] Niobium oxides have furthermore been extensively studied for their electrochromic properties e.g. photodetection 11 and in recent years, the potential of amorphous and nanostructured Nb2O5 for electrochromic windows has been investigated.…”

Facile synthesis of flower-like hierarchical N-doped Nb2O5/C nanostructures with efficient photocatalytic activity under visible light

“…42 The high-resolution C 1s spectra of the as-fabricated N-NBO/C were deconvoluted into four peaks at 284.2, 284.8, 286 and 288 eV. The two peaks at 284.2 and 284.8 eV are ascribed to adventitious carbon (C-C/C]C), 43 which was created owing to the incomplete burning of the organic constituent and pollution from the air, and the peaks at around 286 eV and 288 eV are ascribed to the existence of C-O and O-C]O groups, 34,35 respectively. The carbon in N-NBO/C is attributed to CO X species from the incomplete thermal decomposition of the organic component (Hmta) adsorbed on the surface of NBO aer the heat treatment.…”

Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

“…The representative fit of the O1s region of Nb 2 O 5 _550_air is shown in Figure 2 . As can be seen in this result, the high resolution O1s XPS region was deconvoluted into three different species, namely O (I) with BE of 529.80–530.59 eV, assigned to lattice oxygen (O 2- ) in metal oxide, O (II) with BE of 530.87–531.63 eV [ 42 , 52 ], corresponding to oxygen in CO and OH [ 52 , 54 ], and O (III) with BE of 531.97–532.83 eV [ 47 , 54 ] attributed to physically adsorbed water. It is noted that the C-O interactions probably originated from the presence of adventitious carbon in all samples, as previously mentioned.…”

“…Comparison of the XPS Nb3d regions of Nb 2 O 5 _SA and Nb 2 O 5 _550_air can be found in Figure 3 . The high-resolution core level XPS spectra of Nb3d, due to spin-orbit splitting, showed two photoelectron peaks (Nb3d 5/2 and Nb3d 3/2 ) with BE in the range of 206–207 eV and 209–210 eV, corresponding to Nb 2 O 5 [ 54 ]. Moreover, a higher BE of the core level of the Nb3d main peak (Nb3d 5/2 ) was recorded for the amorphous samples, and the BE values decreased with increasing crystallinity of the materials, as evidenced in Figure 3 .…”