Vanadium Phosphorus Oxide Research Articles

Structural Investigation of Silver Vanadium Phosphorus Oxide (Ag2VO2PO4) and Its Reduction Products

Structural Investigation of Silver Vanadium Phosphorus Oxide (Ag₂VO₂PO₄) and Its Reduction Products

Sparse ab initio x-ray transmission spectrotomography for nanoscopic compositional analysis of functional materials.

The performance of functional materials is either driven or limited by nanoscopic heterogeneities distributed throughout the material's volume. To better our understanding of these materials, we need characterization tools that allow us to determine the nature and distribution of these heterogeneities in their native geometry in 3D. Here, we introduce a method based on x-ray near-edge spectroscopy, ptychographic x-ray computed nanotomography, and sparsity techniques. The method allows the acquisition of quantitative multimodal tomograms of representative sample volumes at sub-30 nm half-period spatial resolution within practical acquisition times, which enables local structure refinements in complex geometries. To demonstrate the method's capabilities, we investigated the transformation of vanadium phosphorus oxide catalysts with industrial use. We observe changes from the micrometer to the atomic level and the formation of a location-specific defect so far only theorized. These results led to a reevaluation of these catalysts used in the production of plastics.

Preparation of Nickel Nanocatalysts and Application to the Hydrodechlorination of 3-Chlorophenol under Liquid Phase

Nickel nanoparticles were successfully synthesized via the reduction of nickel salt using ethylene glycol (EG) and sodium borohydride (NaBH4) as reducing agents. These nickel nanoparticles were then loaded on the supports as Ni-X (X = vanadium phosphorus oxides (VPO), TiO2, and ZnO) in high loading yield. The optical properties of these catalysts were characterized by UV-vis spectroscopy, the structure of Ni-X was studied by powder X-ray diffraction (PXRD), the distribution of Ni particles in X was studied by transmission electron microscopy (TEM), and the specific surface area of Ni-X was evaluated by N2 adsorption isotherm analysis at 77 K. All results corroborated the loading process. Indeed, TEM image indicated that the nickel nanoparticles size is in the range of 14 ÷ 16 nm and fully loaded into X. The activities of these catalysts were performed on the hydrodechlorination of 3-chlorophenol in the presence of sodium hydroxide as base at atmospheric pressure and at RT. The results showed that Ni-X exhibited high activities up to 98% within 90 min in the case of Ni-ZnO catalyst.

Cover Picture: Phosphoric Acid: A Key Role in Control of Structure and Properties of Vanadium Phosphorus Oxide Catalysts During Synthesis (04/2021)

Cover Picture: Phosphoric Acid: A Key Role in Control of Structure and Properties of Vanadium Phosphorus Oxide Catalysts During Synthesis (04/2021)

Phosphoric Acid: A Key Role in Control of Structure and Properties of Vanadium Phosphorus Oxide Catalysts During Synthesis

AbstractThe catalytic performance of vanadium phosphorus oxide (VPO) catalysts is closely related to the synthetic conditions of precursors. Herein, the role of phosphoric acid during VPO precursors synthesis process was thoroughly studied by investigating the morphology, crystal phase composition, and surface chemical property of VPO catalysts and their precursors. The H3PO4 concentration, the temperature of reaction system at the time of H3PO4 adding, and H3PO4 adding speed were optimized to prepared efficient VPO catalysts which applied in selective oxidation of n‐butane to produce maleic anhydride (MA). The obtained VPO catalyst by adding 85 % H3PO4 at or above 110 °C with the speed of approximate 1.1 mL/min could exhibit promising catalytic performances, which are 93.8 % of n‐butane conversion and 62.4 % of MA yield at 420 °C. Thus, this study emphasized the role of H3PO4 adding during VPO synthesis process, which is favorable to understand and fabricate the compositional, structural, and morphological properties of VPO catalysts.

Mechanochemystry as advanced methodology in green chemistry for applied catalysis

In this survey we have assessed how mechanochemistry techniques comply with the aims of Green Chemistry to minimise the use of environmentally damaging reactants and unwanted by-products. In the publications the preparation of vanadium-phosphorus oxides as industrial catalysts for maleic anhydride production from n-butane and perspective catalysts of phthalic anhydride manufacture by direct n-pentane oxidation were analyzed. It is shown that mechanochemical activation and synthesis reduces the amount of harmful waste used in the production of the catalyst and increases its effectiveness. Improvement of a catalyst’s properties, help limit production of harmful emissions such as carbon oxides and hydrocarbons. It was established that mechanochemical treatment can by successfully used in the process of industrial vanadium-phosphorus oxide catalysts modification or in the process of introduction in its composition of additives which lead to increase of activity and selectivity of hydrocarbons oxidation. The possibility of the mechanochemistry use in the vanadium-titanium oxide catalysts preparation which are the base catalysts in industrial phthalic anhydride production from o-xylene was determined. It was established that mechanochemical treatment of the vanadium and titanium oxides mixture permits to delete the nitrogen oxides emission in atmosphere and prepared catalysts demonstrate the same phthalic anhydride yield but at low reraction temperature. Catalysts, manufactured by mechanochemical treatment (on the base of molybdenum oxide), provide new techniques for producing compounds as exemplified by the direct oxidation of benzene to form phenol which can replace industrial two-step process from cumene or proposed process of benzene oxidation by N2O. Mechanochemistry treatment could produce catalysts which eliminated the need to use highly toxic nitrogen oxides as reducing agents. The article describes activating Cu-Ce-O catalysts which reduce the temperature of the process for removing carbon monoxide from exhaust gases and as a method for purifying hydrogen u sed in fuel cells. Finally, there is a description of mechanochemically treated catalysts, containing metals and supported on stainless steel supports which are used to remove aromatic hydrocarbons from water sewers.

Synthesis of nano Ag catalyst embeded vanadium phosphorus oxide for oxidation of styrene to benzaldehyde by hydrogen peroxide

In this work, nano silver catalyst loaded on vanadium phosphorus oxide (Ag/VPO) for oxidation of styrene to benzaldehyde was synthesized by impregnating method including impregnating of VPO substrate with colloid solution of nano silvers. VPO substrate was prepared by microwave-assisted reaction of vanadium and phosphorus precursors. Meanwhile, nano Ag/PVP was prepared in solution using NaBH4 as reducing agent and polyvinylpyrrolidone (PVP) as protecting agent and spherical-shaped nano particles with mean diameter of about 7.5 nm determined by transmission electron microscopy (TEM) was obtained.

Sustainable Acrylic Acid Making via Acetic Acid–Formaldehyde Condensation: The Highly Selective and Durable VPO-TiO2 Catalyst Accomplished by VPO Phase Control and Wet Co-Mechanical Milling

On the basis of the precise phase control of vanadium phosphorus oxides (VPOs), nanosized TiO2 was employed as a dopant/dispersant to fabricate a series of VPO-TiO2 catalysts through a wet mechanic...

Facile Synthesis and Synergetic Interaction of VPO/β-SiC Composites toward Solvent-Free Oxidation of Methanol to Formaldehyde.

Composite materials have revealed remarkable activities in various catalytic applications. However, choosing an appropriate material to enhance the catalytic activity and stability is a major challenge in the field of catalysis. In this article, we reported vanadium phosphorus oxide (VPO)/β-SiC as a stable composite material with good catalytic activity. VPO/β-SiC composite materials with different compositions were fabricated by the impregnation technique to investigate the catalytic activity and stability of these materials in liquid-phase reactions. The physiochemical characteristics of the prepared catalysts were analyzed by several spectroscopic methods. The catalytic activities of VPO/β-SiC composites were studied in a solvent-free oxidation of methanol using tert-butyl hydroperoxide (TBHP) as an oxidant. The reaction conditions were optimized by changing various reaction parameters. Under optimized reaction conditions, the 10 wt % VPO/β-SiC composite showed 100% conversion with 89.8% selectivity to formaldehyde.

Correlation between Nanostructural and Enhanced Electrical Conductivity of Annealed 30V2O5–20Bi2O3–50P2O5 Glass

AbstractStructural and DC conductivity of annealed 30V2O5–20Bi2O3–50P2O5 traditional quenching melt glass is investigated. The as quenched with amorphous nature and crystallized formed phases of annealed samples are confirmed by X‐ray diffraction and differential scanning calorimeter (DSC) techniques. The average crystallite size of the present samples after crystallization at different temperatures and times is estimated to be about 47–74.9 nm. DSC analyses of the glasses indicate a prominent glass transition temperature at 669.9 K. Monoclinic bismuth phosphate phase is formed after annealing at 723 K for 2 h and completely disappeared at 923 K with the formation of orthorhombic vanadium phosphorus oxide and new bismuth phosphate monoclinic phase. The conductivity is discussed in conformity with Mott's theory. The crystallinity development reduces the grain boundaries which leads to the conductivity improvement.

Phosphorus-Based Ionic Liquid as Dual Function Promoter Oriented Synthesis of Efficient VPO Catalyst for Selective Oxidation of n-butane

Vanadium phosphorus oxide (VPO) catalysts promoted by phosphorus-based ionic liquids (ILs) as structure directing agent and promoters have been innovatively synthesized and investigated for selective oxidation of n-butane to maleic anhydride (MA). The catalytic performances showed that the IL addition notably improved the n-butane conversion and MA selectivity, during which the optimized 3%IL-VPO catalyst exhibited the maximum MA yield of 59.2% that is much better than that of blank VPO with 49.4% MA yield under the same reaction conditions. XRD, FI-IR, Raman, SEM, TG, BET, XPS and H2-TPR techniques were utilized combinatorically to elaborate the synergistic effect of cations and anions of ILs. Results demonstrated that IL-cations oriented synthesis of VPO precursor showing a vertically intercrossed slice structure morphology having smaller lamellar thickness. Correspondingly, it notably enhanced the specific surface area of the VPO catalysts and exposed the more active surface of (VO)2P2O7 after activation. Meanwhile, IL-anions as promoters largely modulated the P/V ratio, valence state of V and oxygen species amounts on the surface of VPO catalyst, etc. All of these influence factors were subsequently discussed in detail and correlated to the catalytic performance of VPO catalysts.Graphic

Hydroxyl‐Rich Deep Eutectic Solvents Assistant Synthesis of VPO and Its Application in Selective Oxidation of n‐Butane

AbstractDeep eutectic solvents (DESs) consisting of choline chloride (ChCl) and polyols (Ethylene glycol (EG), 1,4‐Butanediol (BDO), Glycerol (GL), and Xylitol (XYL)) as a green and effective promoter assisting the synthesis of vanadium phosphorus oxide (VPO) were innovatively proposed and investigated in detail for the selective oxidation of n‐butane to maleic anhydride (MA). The catalytic results showed that the performance of VPO catalysts was improved significantly with the addition of polyols DESs. A combination of techniques including SEM, TEM, XRD, FT‐IR, Raman, XPS, and TG‐DTA were employed to investigate the effect of DES on the structure of VPO. We correlated the structure of the catalysts with catalytic performance and found that the n‐butane conversion was positively correlated with the intensity ratio of I (020)/I (204) for catalysts, and the MA selectivity of VPO catalysts was negatively correlated with the vanadium average oxidation state on the catalyst surface.

Synthesis of Porous and Highly Crystallinity Vanadium Phosphorus Oxide Catalysts by Multifunctional Biomass-Based Deep Eutectic Solvents.

Deep eutectic solvents (DESs) as a novel class of ionic liquid analogues has been widely used in various fields. Herein, a multifunctional biomass-based DES composed of choline chloride (ChCl) and glucose (GLU) was synthesized and used for the modification of vanadium phosphorus oxide (VPO) catalyst, which is the sole catalyst for the selective oxidation of n-butane to maleic anhydride (MA) in industry. The DES is more green, cost-effective and efficient compared with traditional modifier (metal inorganics and organic polymers). A combination of structure and catalytic performance was investigated in detail to deeply understand its functions. Initially, this DES plays the role of structure directing agent at the stage of precursor synthesis, which can induce the formation of active plane and obtain highly crystalline precursors. Accordingly, the active phase with highly crystalline was obtained after the activation of precursors. Additionally, the DES was decomposed during the precursors activation, resulting in the formation of porous structure around 20 nm on the active plane. Besides this, the surface chemical state including the valence state and acid-base property was changed significantly due to the function of DES. All of these lead to about an 11% increase of MA mass yield, which has great significance to the high value utilization of low carbon alkanes.

How to achieve a highly selective yet simply available vanadium phosphorus oxide-based catalyst for sustainable acrylic acid production via acetic acid-formaldehyde condensation.

A series of unsupported and supported vanadium phosphorus oxide catalysts were prepared by employing a new strategy, which significantly reduced the complexity of catalyst preparation. The greatly simplified catalyst fabrication benefits a greener and lower-cost process for practical applications. The currently fabricated systems showed ca. 90% target product(s) selectivity with a promising yield as well as catalyst durability.

Vanadium Phosphorus Oxide/Siliceous Mesostructured Cellular Foams: efficient and selective for sustainable acrylic acid production via condensation route

A new type of supported vanadium phosphorus oxide (VPO) with self-phase regulation was simply fabricated (organic solvent free) for the first time by depositing the specific VPO precursor NH4(VO2)HPO4 onto the Siliceous Mesostructured Cellular Foams (MCF) with controlled activation. The resulting materials were found to be highly efficient and selective for sustainable acrylic acid (AA) plus methyl acrylate (MA) production via a condensation route between acetic acid (HAc) and formaldehyde (HCHO). A (AA + MA) yield of 83.7% (HCHO input-based) or a (AA + MA) selectivity of 81.7% (converted HAc-based) are achievable at 360 °C. The systematic characterizations and evaluations demonstrate a unique surface regulation occurring between the MCF and the NH4(VO2)HPO4 precursor. NH3 release upon activation of NH4(VO2)HPO4 precursor together with adsorption of NH3 by MCF automatically induces partial reduction of V5+ whose content is fine-tunable by the VPO loading. Such a functionalization simultaneously modifies phase constitution and surface acidity/basicity of catalyst, hence readily controls catalytic performance.

Precisely phase-modulated VPO catalysts with enhanced inter-phase conjunction for acrylic acid production through the condensation of acetic acid and formaldehyde

A type of precisely phase-modulated vanadium phosphorus oxides (VPOs) was fabricated for the first time by quantitatively mixing the pure phase of γ-VOPO4, δ-VOPO4, and (VO)2P2O7 in certain ratios through a mechanical milling approach. The resulting materials were used as catalysts for very efficient condensation of acetic acid and formaldehyde to acrylic acid as well as methyl acrylate. The modulated dual phase VPO catalyst outperforms the single-phase counterpart, and by optimizing the reaction conditions especially the contact time, we can further considerably enhance the catalyst performance. Over an optimized catalyst of δ-VOPO4/γ-VOPO4 (w/w, 3/1), the (AA + MA) yield of 84.2% with the equivalent (AA + MA) formation rate of 1.71 mmol·g−1·h−1 or the (AA + MA) yield of 41.8% with the equivalent (AA + MA) formation rate of 4.25 mmol·g−1·h−1 is achievable at 360 °C on the formaldehyde input basis. This sort of catalyst is rather durable within a period of 110 h, and fully recovered by simple air-treatment at the reaction temperature. Due to the enhanced conjunction at the interface of two phases, the surface property of phase-modulated catalyst such as the P-O bond length and surface acidity is notably modified/enhanced, accounting for the promising catalytic performance.

Synthesis of Vanadium Phosphorus Oxide Catalysts Assisted by Deep-Eutectic Solvents for n-Butane Selective Oxidation

The effects of choline chloride/oxalic acid deep eutectic solvents (ChCl/OA DES) as a green and effective promoter assisting the synthesis of vanadium phosphorus oxide (VPO) catalysts for the selec...

Encapsulation of Vanadium Phosphorus Oxide into TiO2 Matrix for Selective Adsorption of Methylene Blue from Aqueous Solution

Vanadium phosphorus oxide (VPO) has been embedded in a titania matrix. The adsorption capacity of the VPO(5–30 wt %)@TiO2 composites and VPO alone for the removal of harmful cationic and anionic dy...

Nb-Doped Vanadium Phosphorus Oxide Catalyst for the Aldol Condensation of Acetic Acid with Formaldehyde to Acrylic Acid

Nb-doped vanadium phosphorus oxide catalysts were prepared and characterized using a variety of methods, including XRD, FT-IR, XPS, TPD and BET. The catalysts were examined for their ability to promote the aldol condensation of acetic acid with formaldehyde to acrylic acid. Catalyst composition and the conditions used to prepare the catalysts were investigated for their effects on catalytic activity. The addition of Nb changes the properties and catalytic properties of the catalyst to some extent, especially the surface acidity of catalyst and the average valence of surface V atoms, which have the greatest influence on the catalyst. When Nb/V = 0.06, the catalyst surface has the greatest acidity, the valence of surface V atoms is the lowest, and the selectivity (83.4%) and yield of acrylic acid (18.1%) are maximized.

Cyclohexane Oxidation to Adipic Acid Under Green Conditions: A Scalable and Sustainable Process

AbstractThis work reports a 1 mol scale catalytic process to synthesize adipic acid directly from cyclohexane in solvent‐free conditions using air as oxidant. Catalysts based on vanadium phosphorus oxides were prepared, characterized and tested. They showed good activity and remarkably high selectivity to adipic acid in comparison to other already known heterogeneous catalysts. The use of solvent‐free conditions permits the easy separation of the product from the reactant mixture, which is very important from the industrial point of view. The process can be used at industrial scale for sustainable adipic acid synthesis.