Reduction, vanadium

Fig. 2.3 Flow diagram ofTi02 production by the k) Evaporator I) TiCU superheater m) O2 su-chloride process, a) Mill b) Silo c) Fluidized- perheater n) Burner o) Cooling coil p) Filter bed reactor d) Cooling tower e) Separation of q) Ti02 purification r) Silo s) Gas purification metal chlorides f) TiCU condensation g) Tank t) Waste-gas cleaning u) CI2 liquefaction, h) Cooler i) Vanadium reduction j) Distillation ...

Vanadium reduction was strongly affected on the modified zeolites. The amount of Hz consumption in the TPR analysis related to the metal content (pmol Hz/pmol Ce -i- V) decreased largely. Moreover, the ratio of the extrapolated and observed Hz consumption (Hz ext/obs) was higher on the IMPV catalyst compared to the others. This behavior was supported by the UV-VIS spectroscopy data (Figs. 2 and 3), showing similarity of both profiles, the dry catalyst and after the reduction treatment. Both did not present absorption bands attributed to d-d transition in the 800-1800 nm region. These results suggest that almost all the vanadium is in the oxidation state in the IMPV catalysts. 

After vanadium introduction, different behaviors in the vanadium reduction/oxidation capacity were observed depending on the cerium location and the... 

Animation Vanadium Reduction Online Learning Center... 

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. 

Strong metal support interaction is commonly proposed in the literature for reduction of oxide [17]. This model is in agreement for an interface like Ni-O-V over nickel particle. Ease vanadium reduction can be proposed by SMSI and also a decrease of vanadium acidity. This effect lowers vanadium zeolite poising and also vanadium mobility. 

The magnesium is then melted and the temperature raised to between 750°C and 800°C. Vanadium trichloride is next fed to the molten magnesium, under controlled condition, at such a rate as to maintain the temperature between 750 C and 850°C without the use of further external heat. Additional blocks of magnesium are added towards the end of the reaction, to provide an adequate excess for reasonably complete utilization of the vanadium. Reductions require about 7 hr for completion. 

An alternative route that might occur in the Amoco and Chevron preparations where HCl is used as the reductant (schemes 3 and 5), is the formation of chloride or oxychloride species soluble in organic media which react with the H3PO4 and form the precursor. A less likely alternative or parallel route is the solubilization of in an aqueous emulsion (water formed by vanadium reduction is not easily removed) and formation of (VO)HPO40.5H2O in water droplets (49,52). 

Figure 1. Vanadium reduction data obtained by ESR plotted as the equilibrium constant Kt = (1 — f/ /PsOf...

Least squares applied to diffusion free rate data, series 1-6 of Table I, was combined with supposedly diffusion free vanadium reduction data (series 3 and 4 of Pig. 1). Both rate data and reduction data were obtained with K/V = 3.5 and essentially the same temperature - and gas composition range. 31 reduction data and 105 rate data are included in the regression. Parameter values that minimized SSQ were determined. 

Figure 4. Prediction of vanadium reduction and precipitation of for standard gas composition using model 1 with parameter values from Table 11.

Cathodic vanadium reduction in VCl2-NaCl-KCl melts proceeds in one mass transfer-controlled two-electron step. It was shown that, at high cathodic current densities, the formation of alkali metal can affect voltammetry measurements. The necessity of separating the concepts of limiting diffusion current density and current density corresponding to the expansion of the cathode deposit was justified. 

Figure 2. Effect of Ti02 content in slag on vanadium distribution (T=1703K) (a) Effect of Ti02 content in slag on vanadium distribution ratio (b) Effect of Xi02 content in slag on vanadium reduction rate...

Some researches had proven that Ti(C,N) solid particles will be easily precipitated with temperature increasing. It was commonly believed that 1470 C-1480 C was the sensitive temperature area for Ti(C,N) precipitation, and the foamy phenomena was not serious [6] below 1470 C. Therefore, temperature controlled between 1470 C 1480 C could be beneficial for vanadium reduction and Ti(C,N) precipitation. 

High binary basicity will contribute to vanadium reduction due to the double functions of lime. Lime reacts with Si02 so the reaction between V2O3 and silieon is improved, and the forming of Ti(C,N) will be prevented as lime reaets with Ti02, whieh is favorable for vanadium diffusion from slag to hot metal. 

The vanadium distribution ratio and the vanadium reduetion reaction rate will be increased with increasing temperature. Hearth temperature being controlled between 1470"C 1480 C was beneficial for vanadium reduction and Ti(C,N) precipitation control. 

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