Addition Of MoO3 Research Articles

ChemInform Abstract: EFFECT OF MOO3 ADDITION ON THE GRAIN GROWTH KINETICS OF A MANGANESE ZINC FERRITE

AbstractZusatz von wenig MoO3 zu Mn‐Zn‐ferriten der Zusammensetzung Mno‐5,Zno‐44°C Fe,‐o5O4 verhindert intergranulare Porosität und diskontinuierliches Kornwachtum während des Sintems.

Anomalous behavior of molybdenum oxide as a fire retardant for polyvinyl chloride

The widespread application of polyvinyl chloride (PVC) as wire and cable insulation in the communication and electrical industries is due in part to its inherent fire retardant properties, which are improved by the addition of antimony oxide. This addition also increases somewhat the already high rate of smoke formation. Molybdenum trioxide, used either with or instead of Sb 2O 3, has been reported to be a smoke suppressant as well as a flame retardant. This is corroborated by laboratory-scale measurements reported here. However, in a large-scale test under high enthalpy input conditions, MoO 3 appeared to be ineffective in limiting the flame spread. A detailed investigation of the pyrolysis of PVC by thermogravimetric analysis and mass spectroscopy showed that the addition of MoO 3 results in the reduction of the temperature at which HCl is evolved, an increase in the temperature at which the organic pyrolyzate is produced, and a change in compostion of this pyrolyzate from aromatic to aliphatic. The underlying chemical mechanism is explained by the action of MoO 3 as a Lewis acid: 1. 1. The dehydrochlorination of PVC is catalyzed and occurs at a lower temperature; 2. 2. This process yields trans polyenes, either directly or via rapid isomerization of cis polyenes; 3. 3. The trans polyenes, being unable to cyclize and split off benzene, are stable to higher temperatures, at which a different mechanism obtains to give aliphatic products. The ineffectiveness of MoO 3 is ascribed to the difference in flame characteristics between aliphatic and aromatic fuels. The disagreement between laboratory and large-scale tests is attributed to the higher temperature at which the aliphatic pyrolyzate appears, which is reached only under conditions of higher enthalpy input that prevail in the large-scale tests.

The Oxidation Activity and Acid-Base Properties of CO3O4–V2O5 and CO3O4–MoO3 Systems

Abstract The acidity and basicity of Co3O4–V2O5 and Co3O4–MoO3 systems, with different compositions, were measured by means of the adsorption of NH3, pyridine, and CO2. The values of acidity were also confirmed by studying the catalytic activity for acid-catalyzed reactions, such as the dehydration of isopropyl alcohol and the isomerization of 1-butene. With the addition of V2O5 or MoO3, the basicity rapidly decreases and the acidity gradually increases. The catalytic activity for the oxidation of hexane is well correlated with the basicity of the catalysts. With the Co3O4-rich catalysts, V/(Co+V) or Mo/(Co+Mo)<0.4, butadiene is mainly oxidized to CO2; the rate is also correlated to the basicity. However, the Co3O4-poor catalysts, V/(Co+V) and Mo/(Co+Mo)>0.6, show a good selectivity for the maleic anhydride formation. The Co3O4-containing catalysts, regardless of the composition, are not effective for the selective oxidation of butene to butadiene. In the oxidation of methanol, the Co3O4-rich catalysts give only CO2. However, with the Co3O4-poor catalysts, formaldehyde is almost the sole product. It is concluded that the catalytic behavior is to be interpreted, to a considerable extent, in terms of the acid-base properties of the metal oxides.

MoO3 additives for PVC: A study of the molecular interactions

The detailed molecular interactions occurring during thermal degradation of PVC polymer formulations containing MoO3 additives are investigated using laser microprobe techniques coupled with mass analysis of the volatile pyrolysis products. Comparison with Sb2O3–PVC compounds indicate that the additive effects exhibited by MoO3 are fundamentally different from those observed for Sb2O3. Thermal decomposition of MoO3–PVC is characterized by (1) catalyzed dehydrochlorination of PVC at a lower temperature and increased rate; (2) marked reduction in evolution of benzene, the major fuel species from PVC; and (3) decreased evolution of volatile hydrocarbon species from the polymer plasticizer component. Vapor-phase interactions involving volatile molybdenum species are found to be unimportant. The experimental data indicate that condensed-phase mechanisms and heterogeneous reactions involving MoO3(s) control polymer decomposition processes. Molecular level details of these reactions are presented and their implications to polymer flame retardance and smoke suppression discussed.

Effect of MoO3 Addition on the Grain Growth Kinetics of a Manganese Zinc Ferrite

The effect of MoO3 addition on the grain growth and densification kinetics of a high permeability manganese zinc ferrite was studied. Grain growth in the presence of a small amount of MoO3 occurs in two main stages characterized by a faster rate of grain growth accompanied by rapid densification and pore coalescence in the first stage, when the MoO3 is present as a liquid phase along the grain boundaries, and comparatively slower rates of grain growth and densification than those for the basic composition in the second stage, when MoO3 evaporates from the matrix. The activation energies for grain growth in these stages suggested that surface and volume diffusion mechanisms were operating in the first and second stages respectively.

Catalytic hydrodenitrogenation of basic and non-basic nitrogen compounds in Athabasca bitumen distillates

The denitrogenation of distillates derived from Athabasca bitumen over several unpromoted and promoted molybdenum oxide/alumina catalysts has been studied. The removals of both the basic and non-basic nitrogen compounds are compared for a heavy gas oil and a coker kerosene distillate. The addition of MoO 3 to alumina had a much more pronounced effect on the removal of non-basic nitrogen compounds than of basic ones. Comparison of several nickel- and cobalt-promoted catalysts showed that the denitrogenation activity of catalysts increased with the promoter/molybdenum ratio up to an atomic ratio of about 0.6. Any further increase in the atomic ratio did not change the denitrogenation activity. As this trend was observed with catalysts made with different supports, as well as with varying MoO 3 concentrations, it is believed to be independent of physical properties such as surface area. Basic nitrogen removal also followed similar trends with increasing promoter/ molybdenum ratio.

Effect of Supports and Additions (Metal Oxides) on Iron (III) Sulfate Catalysts for the Reduction of Nitrogen Oxide with Ammonia -Selection of Coprecipitated Fe2(SO4)3-α-Fe2O2-TiO2-MoO3(WO3) Catalysts-

For the purpose to obtain catalysts with high activity and durability for the reduction of nitrogen oxide with NH3, various catalysts containing oxides of Fe, Cr, Cu, Al, Ti, and Mg were prepared from the precipitates formed by the reaction of sulfates with NH3 aq.The catalytic activity and the effect of SO r were tested by using a flow reactor (I. D.: 12.0 mm) under atmospheric pressure and at 250-500°C.The average diameter of the granular catalysts was 1.0 mm. Inlet gas concentration was 500 ppm NO-667 ppm NH3-0 or 1000 ppm SO2-5% O2-10% 1120-N2 balanced and the total gas flow rate was 1000 Ncm'imin (space velocity: 1.1 x 105 hr-) toward O.55 cm (bulk volume) of the catalysts.On the basis of these results, the catalyst, Fe, (SO4)3-ce-Fe3O2-iO3(Fe2O2-TiO3 system), was found to be highly active both in the presence and in the absence of SOS. Furthermore, it was proved that the addition of MoO3 or WO, to this iron catalyst increases the stability against SO r and selectivity for the reduction of NO.On the basis of the study of the reduction of NO with NH, or the oxidation of NH3 with O2- over the catalysts pretreated with pure H2 or 1000 ppm NH3-N2 mixture, it was confirmed that SO4 in the catalysts promotes the stable and selective reduction of NO. Also, only TiO2 of anatase type is active and the addition of MoO8 or WO, to this TiO2 was found to be very effective for the reduction of NO.

Studies on the Catalytic Synthesis of Aromatic Nitriles (Part 1)

A vapour phase catalytic ammoxidation reaction using SO2 as an oxidizing agent was investigated as follows: C6H5CH3+NH3+SO2→C4H5CN+2H2O+H2S+2.0kcal/mole. This reaction is a little exothermic and the equilibrium constants are very large at wide range of temperatures (Kp=4×108: at 300-500°C). Therefore, the reaction is thermochemically very favourable and is free from trouble of deep oxidation as SO2 is a weak oxidizing agent.In consequence of the investigation with various catalysts it was found that the reaction was promoted even by γ-Al2O3 alone into benzonitrile at a yield of Ca. 70(mole)%/fed toluene and moreover the activity of γ-Al2O3 improved by the addition of CuO, Fe2O3, Cr2O3, MoO3, WO3 and V2O5. The conversion of 93.9 (mole) %/fed toluene and the selectivity of 99.2 (mole)% to benzonitrile were obtained by the γ-Al2O3-V2O5-MoO3 catalyst at 430°C.The preferable molar ratio of reactants was NH3_??_SO2_??_toluene. The maximum yield of benzonitrile was observed at 440-470°C. The activity of catalyst changed with the reaction time. In the case of γ-Al2O3 the activity increased gradually during the period of Ca. 1.5hrs after the start of reaction and then began to decrease after 26-27hrs. This decay of catalyst can be explained by the deposition of sulphureous and carbonaceous matters over the catalyst surface. The decayed catalyst was regenerated to 98% of the activity before the decay by means of slow burning of these matters in the air current.

Codimerization of Propylene with Ethylene Catalyzed by NiO-MxOv-Al2O3

The activity of the NiO-A1203 catalyst for the codimerization was remarkably affected by the addition of metal oxides, viz., WOg, MoO3, V20fi, Cr20, Fe20g and CaO The correlation between the electronegativity of the added metal ions and the activity was firmly established (Fig.1). This might be onsidered that added metal ions retarded the oxidation state of Ni ions, and thus affected the atalytic activity. The moderate reduction of the catalyst withhydrogen before the reaction also brought about more enhancement of the activity than the severe reduction er the fairly weak oxidatien (Fig.2). On the basis ef these results, nickel. with slightly lower valency contributed to the a tive site for the codimerization. Wos was found to give the most suitable valency state toward nickel for the codimerization reaction.

A Study of the Catalytic Partial Oxidation of Hydrocarbons. VI. The Effect of Molybdenum Addition to the Vanadium Oxide Catalyst on the Oxidation of Butene to Maleic Anhydride

Abstract In the present work, the vapor-phase partial oxidation of cis-2-butene was carried out using V2O5-MoO3 catalysts with different compositions, at 350°C, and at a butene content of 0.65% in air, in order to elucidate the effect of the addition of MoO3 to the V2O5 catalyst on the selectivity and the mechanism for maleic anhydride formation. Two types of catalytic specificities were found, depending upon the Mo content: in the range of less than 20 atom% Mo, the specificity was similar to that of V2O5 alone, while in the range of more than 50 atom% Mo, a different specificity was observed, one which gave 1.2 times the yield of maleic anhydride than did V2O5 alone or the Mo-poor catalysts. The increase in the selectivity of butene to maleic anhydride which occurred when a large amount of MoO3 was doped is considered to be caused by the increase in the selectivity of the C4H4O→MA step, not in that of the C4H8→C4H6 or C4H6→C4H4O step. The selectivity of the side pathway in the C4H8→C4H6step was so great that no satisfactory maleic anhydride yield from butene can be expected by the use of the V2O5-MoO3 catalyst.

Effect of Oxide Additions on the Polymorphism of Tantalum Pentoxide: III. "Stabilization" of the Low Temperature Structure Type.

The "low temperature structure type" of Ta2O5 has been found to occur in two distinct forms with the lowest temperature form having a unit cell 14 times the subcell and an intermediate temperature form with a unit cell 11 times the subcell. The two types form intermediate partially ordered mixtures which are apparently in thermal equilibrium at various temperatures between ~ 1000 and 1350 °C. The addition of MoO3, WO3, SiO2, GeO2, ZrO2, TiO2, B2O3 and Al2O3 each affect the multiplicity of the true unit cell in different ways. WO3, SiO2, GeO2, B2O3, and Al2O3 form phases structurally similar to "low-Ta2O5" which are stable up to the solidus temperatures of the corresponding systems.

Catalytic synthesis of pyrazine, piperazine, and 1,4-diaza[2,2,2]-bicyclooctane

A study is made of the deamination of diethylenetriamine over acidalkali catalysts, i. e., kaolin and alumina with promoters. Promoters which raise the acidity of the catalyst, affect the formation of triethylene diamine favorably. Increasing the amount of additive increases the amount of triethylenediamine, and cuts the optimum temperature at which it is formed. On kaolin or Al2O3+15% B2O3, the yield of triethylenediamine amounts to 30% theory. Addition of MoO3 facilitates dehydrodeamination and hydrogenolysis of the diethylenetriamine. The optimum promoter for preparing pyrazine is MoO3 along with a small amount of acid oxides. On the Al2O3+5% MoO3+1% P2O5, the pyrazine yield is 27.5% theory. Triethylenediamine can be separated from mixtures of it with piperazine by azeotropic distillation with mxylene or a mixture of mesitylene and α-memylnaphthalene.

Catalytic oxidation of benzene by doped vanadium pentoxide

Rate data for the oxidation of benzene over a series of supported V 2O 5 catalysts have been obtained at various temperatures in the range 300–440 †C. Additions of GeO 2 and MoO 3 to V 2O 5 did not affect the ratio of benzoquinone: maleic anhydride: carbon dioxide (from complete oxidation), obtained as reaction products. It is shown that addition of GeO 2 to V 2O 5 increased the apparent activation energy of the catalytic reaction, whereas, addition of MoO 3 had comparatively little effect. X-ray and semiconductivity data of these oxide systems indicate that within the limits used, up to a nominal 16 mole % GeO 2 and MoO 3, the additive was completely miscible with V 2O 5 and resulted in a decrease and an increase, respectively, of the number of quasi-free electrons associated with the host oxide. It is concluded that the slow stage in the catalytic oxidation of benzene, in the temperature range investigated, depends upon the electron concentration and the oxide composition at the catalyst surface.

Grain Growth and Phase Transformation of Titanium Oxide During Calcination

Additions of NiO, CoO, MnO2, Fe2O3, and CuO promote the anatase‐rutile transformation and grain growth of TiO2. Additions of Na2O and WO3 retard the transformation and have no effect on the grain growth. The addition of MoO3 strongly promotes the grain growth but has only a slight effect on the phase transformation. Both the grain growth and transformation are promoted slightly by Cr2O3. The transformation is significantly affected by the method of preparing TiO2. The grain size of TiO2 heated in H2 exceeds that of TiO2 heated in O2, in air, in argon, and in vacuum. The rate of transformation decreases with an increase in the partial pressure of oxygen of the atmosphere.