China
Africa
Explore chapters and articles related to this topic
Producing Fuels and Fine Chemicals from Biomass using Nanomagnetic Materials
Published in Vanesa Calvino-Casilda, Antonio José López-Peinado, Rosa María Martín-Aranda, Elena Pérez-Mayoral, Nanocatalysis, 2019
Aiming to a similar objective of a one pot production of HMF derivatives directly from fructose, but using only one catalyst, a magnetic bi-functional WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst has been recently prepared (Mittal et al. 2016). The catalyst was used to synthesize 2,5-diformylfuran (2,5-DFF) from fructose. The chlorosilylated SiO2@Fe3O4 (Cl-SiO2@Fe3O4) nanoparticles served as the nanomagnetic platform for the two functionalities. Tungstic acid was generated via the protonation of sodium tungstate. Oxovanadium was complexed with a salten ligand. Under the optimal one-pot system, tungstic acid-mediated fructose dehydration afforded 82% conversion into 5-hydroxymethylfurfural (5-HMF) in 1 hr. The nanocatalyst was retrieved magnetically and re-used up to five times with marginal losses in the activity.
Algorithms
Published in John Andraos, Synthesis Green Metrics, 2018
Reaction #1: g thietanemL 30 wt% hydrogen peroxideg tungstic acidmL watermL chloroform extractiong magnesium sulfate drying agentProduct: 60.3 g thietane 1,1-dioxide
A new alternative in tungsten production: Chelate-added acidic leaching
Published in Gülhan Özbayoğlu, Çetin Hoşten, M. Ümit Atalay, Cahit Hiçyılmaz, A. İhsan Arol, Mineral Processing on the Verge of the 21st Century, 2017
S. Gürmen, S. Timur, C. Arslan, İ. Duman
Concentrated and dilute tungstic acid solutions are neutralized with alkaline reagents (small enough to keep the pH constant) and hetero poly-tungstate salts are precipitated within minutes. These salts are then converted to sub-micron, pure WO3 particles by a simple thermal decomposition process, carried out at above 650°C.
Effect of reaction time on the phase transformation and photocatalytic activity under solar irradiation of tungsten oxide nanocuboids prepared via facile hydrothermal method
Published in Phase Transitions, 2021
Cong Tu Nguyen, Ngoc Linh Pham, Thi Thuy Nguyen, Duc Tho Do, T. Lan Anh Luu
The transformation from orthorhombic WO3·H2O to monoclinic WO3 and then to Magnéli W17O47 could be explained by the oxolation and dehydration reactions during the hydrothermal process in the highly acidic environment [38,39]. In brief, tungstic acid (H2WO4) was formed during the preparation of the precursor solution via Eq. 3 [26,33]: In a highly acidic environment, tungstic acid interacted with water molecules and transformed into the complex structure [WO(OH)4(OH2)] (Eq. 4): These [WO(OH)4(OH2)] complex structures would then aggregate via oxolation reaction to form WO3·H2O nanostructure even at RT (Eq. 5) [33,40,41]. The oxolation reaction happened more strongly when the hydrothermal process starts, especially in a highly acidic environment. The high ion H+ concentration platform in the highly acidic environment created a high electric field environment, which then vigorously promoted the oxolation process. The orthorhombic tungstite WO3·H2O was driven to form the monoclinic WO3 structure during the hydrothermal process via dehydration reaction (Eq. 6). The dehydration reaction was not completed yet after 12 h of the hydrothermal process; therefore, WO3·H2O and WO3 were presented in sample DH12h. The dehydration reaction was completed after 24 h; thus, only WO3 was observed in sample DH24h. As the reaction time increased to 48 h, the oxolation continued to condense the structure of the material by taking the oxygen out of the WO6 octahedra and changed the configuration in WO3 from corner-sharing to a more condensed, edge-sharing configuration, which corresponded to the appearance of Magnéli phase and oxygen-deficient monoclinic phase W17O47 in sample DH48h. The formation of the oxygen-deficient phase in sample DH12h was assigned to the transition state of the transformation from WO3·H2O to WO3. Note that, the high [H+] ion platform was homogeneous; thus, the oxolation and dehydration processes tended to support the growth equally in the [200], [020], and [002] directions and resulted in the nanocuboid morphology [12,35].