Reduction Of Molybdenum Trioxide Research Articles

On the Reduction of MoO3 to MoO2 : A Path to Control the Particle Size and Morphology.

During the reduction of molybdenum trioxide (MoO3) to metallic molybdenum, the first reduction step yielding molybdenum dioxide as an intermediary product is of crucial importance. In this study, we examined the impact of the parameters reduction temperature, water influx, and potassium content on the hydrogen reduction of this first reaction step. Beginning from the same starting material, the chemical vapor transport mechanism was utilized to yield the phase pure MoO2. Analyses including powder X‐ray diffraction, inductively coupled plasma‐mass spectrometry, scanning electron microscopy, and high performance optical microscopy were performed on the product phases. Modulations of the specific surface areas of molybdenum dioxide ranging from 2.28 to 0.41 m2/g were possible. Furthermore, a distinct shift from small plate‐like grains to cuboid‐like forms was achieved.

Reduction of Molybdenum Trioxide by Using Hydrogen

Metallic molybdenum was synthesized through reduction of molybdenum trioxide (MoO3) by using hydrogen as a reducing agent. The reduction behavior of MoO3 were investigated by using temperature programmed reduction (TPR). The reduced phases were characterized by X-ray diffraction spectroscopy (XRD). The XRD results indicate that the reduction of MoO3 proceed in two steps reduction (MoO3 → MoO2 → Mo) with formation of intermediate phases of Mo4O11 during first step of reduction. However, the TPR results showed only one broad peak that correspond to all reduction step that was merge into one peak. It seem that, increasing the temperature cause the rapid reduction that correlated with thermodynamic consideration data that show the formation of metallic molybdenum is become feasible by increasing the temperature.

Effect of ammonium dimolybdate (ADM) on the reduction of molybdenum trioxide

Ammonium dimolybdate ((NH4)2Mo2O7) or molybdenum trioxide (MoO3) is used as starting raw materials for manufacturing Mo powders. In the initial step, usually carried out in rotary calciners, (NH4)2Mo2O7 or MoO3 is reduced to MoO2. Agglomeration of powder due to melting of eutectic formed between MoO3 and Mo4O11 and due to melting of MoO3 occurs during this reduction step resulting in several manufacturing issues. The reduction from (NH4)2Mo2O7 involves an endothermic reaction however, reduction of MoO3 occurs only by exothermic reaction. It is hypothesized that addition of (NH4)2Mo2O7 to MoO3 will decrease agglomeration of powders due to the endothermic reaction involved in the reduction process. The current paper details experiments carried out to verify the hypothesis. MoO3 containing varying amounts (NH4)2Mo2O7 were reduced at 550°C, 650°C and 750°C in hydrogen atmosphere. The results show lower agglomeration of powder with addition of (NH4)2Mo2O7. The thermal analysis results confirm reduction of MoO3 at lower temperatures with the addition of (NH4)2Mo2O7.

Nanoparticle Molybdenum Dioxide: A New Alternative Catalytic Material for Hydrogen Production via Partial Oxidation of Jet-A Fuels

A battery-extender fuel cell auxiliary power unit (BE-APU) is the first step in a far-reaching and long-term vision that Boeing has for utilizing fuel cells as APUs on board commercial airplanes for greater energy efficiency and improved air quality at airports. A critical requirement for developing a commercially viable BE-APU is a catalyst that can reform and electrochemically oxidize fossil fuel-based aviation fuels. This paper reviews the catalytic performance of nanoparticle MoO 2 , which can effectively reform Jet-A fuels to produce hydrogen and carbon monoxide (synthesis gas) under partial oxidation conditions. Nanoparticle MoO 2 was synthesized by the reduction of molybdenum trioxide (MoO 3 ) powder in a 1:3 volume ratio of ethylene glycol to distilled water at 180 °C for 12 h. The resulting nanoparticle MoO 2 was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and BET surface area measurements. For the partial oxidation of Jet-A fuel at 850 °C, oxygen-to-carbon (O 2 /C) ratio of 0.55 and weight-hourly-space-velocity (WHSV) of 1.5 h ―1 , the synthesized nanoparticle MoO 2 displayed a fuel conversion of ∼99% and a hydrogen yield of ∼60% after 9 h on-stream. Under similar operating conditions, a reference Ni catalyst was deactivated due to coking after less than 4 h of operation. Based on these findings, nanoparticle MoO 2 appears to display a coking resistance higher than that of the reference Ni catalyst during the partial oxidation of Jet-A fuels.

Effect of hydrogen annealing on the composition and particle size of molybdenum nanopowders

We have studied the behavior of molybdenum nanopowder consisting of particles with an average size of 23.7 nm. The powder was prepared by hydrogen plasma reduction of molybdenum trioxide and contained considerable amounts of oxygen in the form of amorphous molybdenum oxides and hydroxides. Annealing in hydrogen for 1 h at temperatures from 300 to 1000°C is shown to cause crystallization of oxides, which then vaporize to form the volatile hydroxide MoO2(OH)2. Most of the oxygen is removed by annealing below 700°C. Starting at this temperature, particle growth is observed. The main mechanism behind the coagulation of molybdenum particles is vapor transport. Annealing at 1000°C for 30–50 min in hydrogen with a dew point of −5°C increases the particle size by about one order of magnitude.

The activity of molybdenum and molybdenum oxide model catalysts for olefin metathesis

The activity of various molybdenum oxides supported on a molybdenum foil substrate for the catalysis of propylene metathesis is measured using an isolatable, high-pressure reactor incorporated in an ultra-high vacuum (UHV) chamber which allows samples to be transferred directly from vacuum into the catalytic test chamber. MoO x samples are prepared both by oxidation of metallic molybdenum and reduction of molybdenum trioxide. The results suggest that the presence of an oxygen overlayer on the catalyst inhibits reaction and that the ranking of activity for metathesis at 870 K using 450 Torr of propylene for oxide samples is MoO2>MoO3>Mo where MoO2 is ∼ 30 times more active than molybdenum metal under these conditions.

Manufacture of composite electrophoretic coatings using very finely divided Mo and Mo2C powders

An electroplating-electrophoretic procedure for producing composite coatings using a combination of electroplating and electrophoretic methods, followed by liquid phase sintering at the eutectic formation temperatures, has been studied. Finely divided Mo and Mo2C powders produced by low-temperature catalytic reduction of molybdenum trioxide and subsequent molybdenum carbiding were employed, and the main electrophoretic deposition mechanisms have been estabished. Electrophoresis parameters have been examined in terms of their effect on the precipitates formation rate and their structure. This procedure enables components operating under corrosion-erosion wear conditions to be protected and their service life increased by a four or fivefold factor.

Effect of temperature and alumina additions on the particle size and morphology in the reduction of molybdenum trioxide

Effect of temperature and alumina additions on the particle size and morphology in the reduction of molybdenum trioxide

茂原製錬工場におけるモリブデンの製錬

In 1965, Taenaka Kogyo Co., Ltd. was established as a molybdenum maker, in Mobara City, Chiba Pref. And now, Taenaka has about 25 percent of the share of molybdenum products in Japan.Molybdenum trioxide and ferromolybdenum are principally produced by roasting and thermit process. Molybdenum metal is also produced by reduction of molybdenum trioxide.

Crystallochemical transformations during the low-temperature reduction of molybdenum trioxide

Crystallochemical transformations during the low-temperature reduction of molybdenum trioxide

Pressing and sintering of fine molybdenum powder

A study was made of the phsicochemical properties, compressibility, and sinterability of a molybdenum powder produced by the catalytic reduction of molybdenum trioxide. It is shown that such a powder possesses a well-developed surface (a specific surface of 4 m2/g) and exhibits high activity during sintering. In the study, compacts of 94% relative density (at a starting density of 48%) were obtained as a result of sintering for 1 h at 1400°C in hydrogen.

Reduction of molybdenum trioxide by aluminium

Reduction of molybdenum trioxide by aluminium