Vanadic Acid Research Articles

Precise regeneration of NOx reduction catalysts poisoned by metal ions via Sabatier principle of antidote-active center interaction

The use of catalysts in industrial processes is critical for reducing harmful emissions, such as NOx, and improving environmental sustainability. However, the poisoning of catalysts by alkali and heavy metals can limit their effectiveness and lead to increased environmental impacts. The development of a precise regeneration approach for metal-poisoned catalysts can help extend the lifetime of the catalysts and reduce the need for frequent replacement, thereby reducing the consumption of materials and energy required for catalyst production. The application of the Sabatier principle of antidote-active center interaction in this study provides a new approach for the regeneration of metal-poisoned catalysts. By using formic acid, which has similar ionization constant as vanadic acid, the best regeneration performance was achieved with high removal efficiency for metal poisons and high retention of active species. This approach not only extends the overall lifetime of catalysts, but also reduces the environmental impact associated with the disposal of spent catalysts. Overall, this study contributes to the development of cleaner production technologies by providing a framework for the precise regeneration of metal-poisoned catalysts. The approach demonstrated in this study can be applied to other catalytic systems and has the potential to reduce the environmental footprint of industrial processes.

The chemistry of Mandelin’s test for strychnine

Strychnine reacts with Mandelin’s reagent giving a violet-blue colouration which changes to orange-red and finally to yellow. The chromic acid test for strychnine was surpassed by Mandelin’s assay due to better reagent stability, lower detection limits and fewer false positives. The reagent is ammonium metavanadate in sulphuric acid. In this communication we provide the reaction route and the mechanism of each step, from the alkaloid to the complex final oxidation product. Several oxidations take place and the vanadic acid formed in situ is reduced to vanadous acid. Some information related to vanadium and vanadium compounds is given in order to understand the reactivity of the involved compound.

A survey of the reactivity of in vitro diagnostic bilirubin reagents developed in Japan using artificially prepared bilirubin materials: A comparison of synthetic delta, unconjugated, and taurine-conjugated bilirubin.

In vitro diagnostic bilirubin reagents based on oxidation with bilirubin oxidase or vanadic acid for total and direct-reacting bilirubin are widely used in Japan; however, their reactivity to unconjugated and conjugated bilirubin and delta bilirubin has not been completely disclosed by manufacturers. We used artificially prepared bilirubin materials to investigate the reactivity with four in vitro diagnostic bilirubin reagents. Porcine unconjugated bilirubin solution, chemically synthesized ditaurobilirubin solution, and chemically synthesized delta bilirubin solution were used as surrogates of naturally occurring unconjugated bilirubin, conjugated bilirubin, and delta bilirubin, respectively. The total bilirubin and direct-reacting bilirubin concentrations were measured by three bilirubin oxidase methods and one vanadic acid method, and the observed concentrations were compared with those obtained by the diazo-based reference measurement procedure. The unconjugated bilirubin and delta bilirubin concentrations were similar when any of the four in vitro diagnostic bilirubin reagents were used during total bilirubin measurement. This was consistent with reference measurement procedure and exhibited a converged inter-method variation. Compared with reference measurement procedure, significantly low ditaurobilirubin concentrations were observed by the in vitro diagnostic bilirubin reagents despite the converged inter-method variation. In delta bilirubin measurement, some reagents reacted doubtfully with unconjugated bilirubin, while showed lower ditaurobilirubin concentrations than its corresponding total bilirubin concentration. Reactivity with delta bilirubin was different for each method including reference measurement procedure. Some reagents were developed to react less with delta bilirubin and others to strongly react with delta bilirubin. We revealed the reactivity of IVD-TB and IVD-DB reagents to artificially prepared bilirubin materials, and their consistency with reference measurement procedure. The delta bilirubin data results vary depending on the reagents used.

Fabrication of two-dimensional carbon/V2O3 composite nanosheets and their application for electrochemical sensing

Two-dimensional (2D) nanomaterials are newly developed and promising modified electrode materials for non-enzymatic hydrogen peroxide (H2O2) detection via an electrochemical strategy due to their unique nanosheet-like structure and excellent electron transport capability. In this study, 2D polyaniline nanosheets doped with vanadic acid have been fabricated and used as templates and precursors to realize the successful preparation of carbon/vanadium trioxide (C/V2O3) nanosheets, which are assembled with a large quantity of V2O3 nanoparticles with an average size of 58.3 nm on carbon matrix. The as-prepared C/V2O3 nanosheets present an excellent sensing performance toward H2O2 with a wide detection range over 5.0–1500 μM and a low detection limit of 1.7 μM (S/N = 3), which are superior to many previous reported metal oxides and even noble metals-based sensors. Furthermore, the C/V2O3 nanosheets-based sensor displays a desirable selectivity, reproducibility, and stability, offering the feasibility for H2O2 detection in real samples. This study provides an efficient way to construct 2D metal oxides and carbon-based nanomaterials for non-enzymatic electrochemical sensing applications.

Graphene vanadic acid (GVA) as a novel heterogeneous catalyst for highly selective benzene hydroxylation under mild conditions

In the present study, Graphene Vanadic Acid (GVA) is introduced as a novel catalyst for high-efficiency hydroxylation of benzene to phenol using hydrogen peroxide at ambient conditions. Graphene oxide as a famous carbon support has converted to a high-performance catalyst through the functionalization using vanadium oxytrichloride (VOCl3). This new carbon compound is regarded as the efficient catalyst due to the prominent advantages such as high-recativity and reusability, facile preparation, active Lewis and Bronsted acid sites, high potential for development of various oxidation reactions, and high thermal, chemical, and physical stability due to the regular carbon structure. GVA progressed the benzene oxidation toward the phenol formation as a useful raw material. Cause of the considerable reactivity of the synthesized catalyst, a minimum amount of hydrogen peroxide was required and the benzene oxidation carried out using an equimolar ratio of benzene/H2O2, and phenol obtained with a remarkable yield (28.2%) as the sole product.

EPR Study on the Intercalation of Azoles into Transition Metal Oxides

Four azoles of different chemical structure were intercalated into MoO3, V2O5, and WO3 oxides synthetized via polycondensation of corresponding oxo-acids under the solvothermal conditions. Structural and morphology peculiarities of these hybrid materials were characterized using X-ray and neutron diffraction, electron microscopy and EPR spectroscopy. The EPR measurements provided the evidence that azole molecules coordinate monomers and oligomers of molybdic, tungstic and vanadic acids during the course of solvothermal synthesis of azole-oxide hybrid structures. This coordination is accompanied with reorganization of growing oxide frame leading to the unprecedently high azole loading. As the result, the azole-intercalated layered oxides with high concentration of ordered paramagnetic centers are formed.

Modeling of the catalytic cracking: Catalyst deactivation by coke and heavy metals

This paper proposes a model of the cracking process considering the catalyst deactivation by Ni, V and coke. The developed model is sensitive to the feedstock composition and describes the kinetics of cracking reactions leading to coke formation, the structural and selective properties of the catalyst. It also reflects the main technological parameters. The forecast calculations showed that when the resins and Ni contents in the feedstock increase by 4.2 wt% and 0.6 ppm, the coke contents on the catalyst increase by 0.75 and 0.32 wt% wt. under the other equal conditions. The catalyst activity decreases by 4.4% relative to initial value along with increasing the V content in the feedstock by 1.9 ppm due to its dealumination. If the Ni with V co-presence in the catalytic cracking feedstock and the Ni content increases by 0.6 ppm, the V destructive effect reduces by 1.2% due to reaction of Ni with the vanadic acid, also Ni on the catalyst increases the catalyst dehydrogenation activity. According to the calculations performed, the yield of the gasoline fraction changes by 4.43 wt%, depending on the feedstock composition (CSH/CAH = 1.6–1.8 units), other things being equal.

Vanadium contamination of FCC catalyst: Understanding the destruction and passivation mechanisms

Vanadium scavenging material comprising magnesium and yttrium oxides (Mg-Y-oxide) was prepared and evaluated for vanadium capture under simulated FCC regeneration conditions for typical FCC process. Vanadium trapping ability was measured using BET, XRD, FTIR, EDX coupled SEM and MAT. The results show that physiochemical properties, vanadium trapping and catalyst protection increase with amount of the trap material. SEM-EDX results confirm migration of vanadium as indicated by its presence in the passivator particle. Vanadium migrates within the catalyst particles by both inter and intra particles mechanisms. The XRD data further reveal high vanadium selectivity towards yttrium when passivator is incorporated after impregnation of vanadium, with the formation of crystalline yttrium vanadate (YVO4). Catalytic evaluation indicates improved activities of catalysts containing passivator which correlate with physiochemical parameters. In the passivation mechanism, mobile vanadic acid preferentially reacts more with Y2O3 in mixed metal oxide due to its higher activity (active sites), forming YVO4. These results therefore reveal that the passivator protects the catalyst by formation of immobile vanadate with mobile vanadic acid, thereby reducing hydrolysis of the catalyst framework and thus preserving important properties of the catalyst.

Reactivity of bilirubin photoisomers on the measurement of direct bilirubin using vanadic acid method.

Objective Investigation of the reactivity of fractions of bilirubin photoisomers with the vanadic acid oxidation method. Methods Bilirubin photoisomers were prepared by irradiating a bilirubin/human serum albumin solution with blue light emitting diode. Direct bilirubin and bilirubin fractions were measured using the vanadic acid oxidation method and high-performance liquid chromatography in the sample before and after irradiation. Results Direct bilirubin was increased in the solution containing bilirubin photoisomers. ( EE)-/( EZ) -cyclobilirubin-IXα and ( ZE)-/( EZ)-bilirubin-IXα completely disappeared after the addition of vanadic acid. Conclusion Bilirubin photoisomers reacted as direct bilirubin in the vanadic acid oxidation method.

Vanadium oxide-based photochromic composite film

V2O5-based composite films were fabricated using peroxo-iso-poly vanadic acid as the filler and transparent urethane resin as the matrix, and the resulting composite films exhibited photochromic property when irradiated with ultraviolet (UV) light.

Synthesis of Nano Magnetite Fe3O4 Based Vanadic Acid: A Highly Efficient and Recyclable Novel Nano-catalyst for the Synthesis of 4,4’-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ols)

Synthesis of Nano Magnetite Fe3O4 Based Vanadic Acid: A Highly Efficient and Recyclable Novel Nano-catalyst for the Synthesis of 4,4’-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ols)

Silica vanadic acid [SiO2–VO(OH)2] as an efficient heterogeneous catalyst for the synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-one and 2,4,6-triarylpyridine derivatives via anomeric based oxidation

Silica-bonded vanadic acid [SiO2–VO(OH)2] (SVA) efficiently catalyzed the synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones via reacting aromatic aldehydes and β-naphthol and urea under solvent-free condition. Additionally, 2,4,6-triarylpyridine derivatives were prepared through the condensation of ammonium acetate, aromatic aldehyde and various acetophenone in the presence of a catalytic amount of [SiO2–VO(OH)2] (SVA) under a same condition. A new anomeric based oxidation was proposed for the final step of the 2,4,6-triarylpyridine derivatives synthesis which was supported by theoretical studies. So the described new mechanistic approach can open up a new and promising insight in the course of rational design, synthesis and applications of novel hydride releasing compounds. The significant features of the present procedure are short reaction time, high yields, easy work-up, and recyclability of the SVA catalyst.

Application of silica vanadic acid [SiO2-VO(OH)2] as a heterogeneous and recyclable catalyst for oxidative aromatization of Hantzsch 1,4-dihydropyridines at room temperature

A simple method for the oxidative aromatization of Hantzsch 1,4-dihydropyridines to the corresponding pyridines is described using hydrogen peroxide as green oxidant and silica vanadic acid as catalyst in acetonitrile at room temperature. The catalyst can be easily recovered and reused for 15 reaction cycles without considerable loss of activity.

Application of silica vanadic acid as a heterogeneous, selective and highly reusable catalyst for oxidation of sulfides at room temperature

Silica vanadic acid (vanadium has been supported on silica) is applied as an efficient, highly reusable and heterogeneous catalyst for the selective oxidation of sulfide to sulfoxide using hydrogen peroxide and in the acetonitrile as a solvent at room temperature. The catalyst can be easily recovered and reused for ten reaction cycles without considerable loss of activity. Also, some advantages of this method were applicable at large scales, high TON of catalyst, chemoselectivity, easy work-up and short reaction time.

Silica-bonded vanadic acid [SiO2–VO(OH)2] as a heterogeneous and recyclable catalyst for thiocyanation of organic compounds in aqueous media at room temperature

article i nfo Article history: Silica vanadic acid (in which vanadium oxytrichloride has been supported on silica) is applied as an efficient, reusable and heterogeneous catalyst for the thiocyanation of heterocycles, substituted anilines (electron-rich and electron-deficient) and N-substituted aromatic amines using hydrogen peroxide in the water as a solvent at room temperature. The catalyst can be easily recovered and reused for ten reaction cycles without consid- erable loss of activity.

One-Dimensional Polyaniline Nanostructures with Controllable Surfaces and Diameters Using Vanadic Acid as the Oxidant

One-dimensional polyaniline nanostructures with controllable surfaces and diameters have been synthesized using vanadic acid as the oxidant in the absence of porous templates and structural directing molecules. The synthetic parameters, such as the concentrations of HCl, and types of oxdiants on the morphologies, diameters, and molecular structures of one-dimensional polyaniline nanostructures have been investigated. As the concentration of HCl is low, polyaniline nanorods with diameters of 10−20 nm and length up to 50−60 nm can be aligned radially along the length axis on the surfaces of polyaniline nanofibers. With the concentration of HCl increased, the diameters of one-dimensional polyaniline nanostructures decrease from 150−300 to 40−100 nm, and the surfaces of one-dimensional polyaniline nanostructures become smooth. The possible formation mechanism of one-dimensional polyaniline nanostructures using vanadic acid as the oxidant has been discussed.

Electrical transport and quasipersistent photocurrent in vanadium oxide nanowire networks

Electrical conductivity and photoconductivity measurements were carried out on semiconducting vanadium oxide nanowire networks synthesized through the polycondensation of vanadic acid. The temperature-dependent conductivity was described well by Mott’s optical multiphonon assisted hopping model at high temperatures and by the variable-range hopping mechanism at low temperatures. The photoconductivity showed a weak temperature dependence. Besides, quasipersistent photocurrent with a single-exponential decay behavior was observed right after switching off the light and was explained in terms of the random local-potential fluctuation model.

Effect of preparation conditions on the ordering of structural elements in vanadium pentoxide xerogels

Vanadium(V) oxide xerogels with an ordered laminar structure are of considerable interest in modern inorganic chemistry [1]. They combine the ease of intercalation of inorganic ions [2] or organic molecules [3] into the interlayer space and the presence of a transition metal ions with variable oxidation states, giving rise to nonlinear electrical and, in some cases, magnetic characteristics. Hybrid inorganic‐organic materials based on xerogels of vanadium(V) oxide and its nanotubular forms [4] attract considerable attention due to their unique physical and unusual physicochemical and rheological properties, which enable their use as cathode materials for lithium batteries [5], chemical sensors [6], electrochromic materials [7], and catalysts [8]. Vanadium(V) oxide xerogels can be prepared by hydrolysis of organic derivatives of vanadic acid, by polycondensation of vanadates in an aqueous solution in an acid medium, and by decomposition of peroxovanadium(V) compounds upon dissolution of the crystalline oxide in hydrogen peroxide [1, 9, 11]. The mechanisms of these processes are essentially different; therefore, it is important to elucidate the structural features of the xerogels as a function of the preparation method. Small-angle X-ray scattering, which is a standard method for measuring the kinetics of gel condensation in solutions [10], can also be used rather efficiently to study the structural features of xerogels. This study reveals the correlation between the chemical prehistory and the structural organization of samples obtained. Complex analysis of small-angle X-ray scattering (SAXS) patterns of xerogel films synthesized by different methods was carried out for the first time and possible models for description of their structure were considered. Colloid solutions of vanadium(V) oxide for the formation of xerogel films were prepared by three procedures (table). According to method A, analytical grade crystalline V 2 O 5 (0.5 g) was dissolved in 15% H 2 O 2 (30 mL) by slow addition of V 2 O 5 powder to the hydrogen peroxide solution [11]. After the oxygen evolution ceased, the solution became yellow. Heating the solution to ~40°C gave a dark red solution, which was kept under ambient conditions for 7 days until a xerogel film formed. According to method B, the gel was obtained by hydrolysis of tert -butyl metavanadate VO(OC(CH 3 ) 3 ) 3 . The ester was synthesized [11] by refluxing a mixture of calcined vanadium(V) oxide with excess tert -butyl alcohol in the presence of a desiccant (silica gel) for 7 h. The resulting mixture was separated by distillation at 81°C . Hydrolysis was carried out by mixing the ester with an equal volume of water (an excess) for the preparation of bulk samples or under ambient conditions. In method C, polycondensation of V took place in an aqueous solution of sodium vanadate on acidification. A colloid solution of V 2 O 5 · n H 2 O was obtained by

The effect of starting materials on the morphology and particle size of copper pyrovanadate Cu 3V 2O 7(OH) 2·2H 2O

Copper pyrovanadate with spherical nanosize particles was successfully prepared from a mixture of vanadic acid solution and copper(I) oxide. Comparisons of X-ray diffraction profiles, scanning and transmission electron micrographs of particles of copper pyrovanadate obtained by using vanadic acid solution and xerogel of vanadium oxide solution were reported.

Effect of vanadium on USY zeolite destruction in the presence of sodium ions and steam—studies by solid-state NMR

The effect of deposited vanadium on the thermal destruction of ultra stable Y (USY) zeolite in the presence of sodium ions and steam was investigated by solid-state NMR. When USY zeolite containing few sodium ions was heated in a dry atmosphere, SiOH groups, which corresponded to defect sites, and strong adsorption sites were formed by the dealumination. The former mainly caused an increase in the mean void volume per supercage and the latter originated from cationic extra framework Al in the supercages. Furthermore, in the dry atmosphere, the sodium ions inhibited the dealumination; the effect of the deposited vanadium on the structural change was not large. After the heat treatment in 100% steam, in case of USY zeolite containing few sodium ions, the crystallinity and the supercage structure hardly changed although the dealumination occurred remarkably. This process did not depend on the deposited vanadium. Data suggested that the heat treatment in 100% steam causes the framework stabilization. In case of USY zeolite containing a number of sodium ions, the synergistic effect between a few deposited vanadium ions and the sodium ions on the framework destruction in 100% steam was tremendous. We propose that the deposited vanadium functions as vanadic acid and catalyzes the conversion of the sodium ions into NaOH. Thus, an increase in the NaOH content promotes the ‘dissolution’ of the zeolite crystal, i.e. the framework destruction. In addition, when the sample containing both a few vanadium ions and a number of sodium ions was heated in 100% steam, the supercage was plugged partially. We believe that the blockage compounds in the supercage are sodium vanadates.