Vanadium interactions

The mechanism of vanadium interaction with growth and differentiation pathways has been extensively studied [70], In tissue culture systems, vanadium has been shown to inhibit growth and, in some cases, modify DNA synthesis to block the G2-to-M transition. Cells blocked at M phase are susceptible to apoptosis, which can be stimulated by vanadium compounds. Vanadium compounds have also been shown to have mitotic effects stimulating growth, cell proliferation, or cell transformation. In some cases, vanadium compounds were able to promote cellular differentiation. Clearly, the addition of vanadium compounds would not have all of these... 

Vanadium Interaction with Signal Transduction Cascades as Part of the Therapeutic Effect... 

FIGURE 11.2 Interactions of vanadium with the hormone-sensitive G protein modulated cAMP producing signal transduction system. Bold lines with arrows leading away from V represent stimulation, blunt-ended lines represent inhibition. V shows where vanadium interactions have geen found. Pase phosphatase, PDE(IV) phosphodiesterase (IV), PEPCK phosphoenolpyrurate carboxykinase, PKA, protein kinse A inactive, PKAa PKA active. This figure was adapted from [13]. 

The present study attempts to elucidate mechanisms for vanadium migration between a Eu3+-exchanged zeolite Y and an AAA-alumina matrix. Eu3+ was used since it can readily be tracked with various spectroscopies. Moreover, effects of different vanadium precursors on migration will be a major focus of the paper because the nature of such precursors has been reported to control zeolite-vanadium interactions (28). SEM/EDX analyses are useful tools for tracking metal migration. Spot analyses on either Y zeolite or matrix particles will be reported since these FCC components show quite different morphologies. 

They find that Vanadium interacts with Nickel in a manner which inhibits the deactivation behaviour of Nickel. They therefore conclude that metals resistant cracking catalysts must be evaluated in the presence of both Nickel and Vanadium. We find that also the mobility of Vanadium is reduced by the presence of Nickel. 

Tris(tetraethylammonium) nonachlorodi vanadate (III) forms red crystals which are very easily hydrolyzed and easily oxidized thus they are most conveniently stored in a manifold such as that illustrated in Fig. 9. The solid is placed in the manifold in a dry-box and then sealed off in vacuo. The glass balls help to prevent the solid caking. When a sample is required it is tapped into one of the sidearms, which is then sealed off. The spectral4,6 and magnetic4,6 properties of the compound are consistent with some vanadium-vanadium interaction within the binuclear anion. 

Improved Methods for Testing and Assessing Deactivation from Vanadium Interaction vvith Fluid Catalytic Cracking Catalyst... 

LERNER DEEBA Vanadium Interaction with FCC Catalyst... 

It would be desirous to have available a sinq)ler testing tool which could imitate many of the aspects of the cyclic deposition particularly the inq)ingement of the metals on the catalyst surface with the simplicity, efficiency, and cost of the Mitchell Method. One such test, at least so far developed for vanadium interaction, is what we termed above as the Engelhard Transfer Method (ETM) (7). 

VANADIUM INTERACTIONS WITH CREY-TYPE ZEOLITES... 

Vanadium interacts with nickel in a manner which inhibits the deactivation behavior of nickel. Metals-resistant catalysts must therefore be evaluated in the presence of both nickel and vanadium. Also, the mobility of vanadium is reduced in the presence of nickel. In general, cyclic deactivation will be the preferred deactivation method in order to simulate the actual metal distribution and interactions on the catalyst and the correct metal age distribution. 

Cyclohexane as a Probe to Nickel Vanadium Interaction in FCC Catalysts... 

The interaction of nickel and vanadium has been proposed in the literature [4,5]. This behavior leads David et al. [4] to propose that studies on metals resistance should he examined with both nickel and vanadium present. Shien-Jen et al [5] showed a decrease of dealumination caused by vanadium due to presence of nickel and consequently, a decrease of coke formation. For the chemical point of view, the nickel-vanadium interaction can be explained by concepts related to bimetallic formation, metal-support interaction etc. However, in individual units one cannot be sure to what extent the interaction occurs, in spite of the low fusion point of V2O5, the migration of vanadium acid species [6] and the great number of cycles to which that a catalyst is submitted [3]. In the riser, the metals probably have a low... 

In addition to these unit conditions, nickel-vanadium interaction is also a function of catalyst age and NiA/ ratio. Hence obtaining the right degree of nickel-vanadium interaction is an important yet non-trivial criterion to simulate the catalyst in its steady state in the laboratory. 

The amount of hydrogen in relation of the estequiometric quantities of Ni to Ni and reduced to V is very interesting. These results are presented on Table 1. For 1-Ni catalyst this quantity is twice that required by the estequiometric. The amount of hydrogen consumption progressively decrease with the increase of vanadium concentration. This effect generally supports the idea of the nickel vanadium interaction. 

The presence of both nickel and vanadium leads to easier vanadium reduction and to difficult nickel reduction. This behavior suggests a nickel vanadium interaction with only the calcined treatment. The influence of vanadium on hydrogen consumption are remarkable and at least a geometrical model can be proposed where part of vanadium present are close to the nickel atoms. It is not within the scope of this work to explain the high consumption of hydrogen observed. 

The D-USY catalyst presented high cracking activity. The results indicate that both nickel and vanadium poison zeolite activity sites. But vanadium poisons preferentially zeolite activities sites for the cracking reaction. Selectivity Sc2-c5 is 49.8 for D-USY, decreased to 42,6 for 1-Ni catalyst and with vanadium adding (from 8Ni-lV to INi-lV catalysts) Sc2-c5 decreases. For the 1-V catalyst selectivity Sc2-c5 is 27,9, 40% lower than D-USY catalyst. This result also confirms a nickel vanadium interaction. The isomerization reaction also increases on 1-V catalyst. This behavior can be related to vanadium acid species formation [8]. 

The poisoning effect of metals on zeolite sites is also observed when in catalyst test is used low temperature. D-USY only presents mcp formation, while nickel poisons around 50% activity. Vanadium poisoning is drastically higher and only 6% of activity remains. The decrease in the activity is lower for the 3NMV, compared to 1 V, also suggesting a nickel vanadium interaction. 

Mitchell impregnated with no steam step leads to nickel vanadium interaction over D-USY, but this interaction can not avoid zeolite damaging. 

Cyclohexane is a good probe to study nickel-vanadium interactions in the FCC ambient. 

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