Vanadium thermal effect

Fig. 1. The size distribution of feed and product vanadium for Hondo asphakenes is compared with model calculations without thermal effects.

Dibenzothiophene derivatives have been used as co-catalysts in the addition polymerization of vinyl and diene monomers. Dibenzothiophene itself, in conjunction with vanadium oxychloride, is effective in initiating the polymerization of isobutylene, - although when incorporated in a Ziegler catalyst system, competition between donor and monomer for the most electrophilic sites results in deactivation of the catalyst. Despite the fact that 2-vinyl- - - and 4-vinyldibenzothiophene - readily undergo thermal polymerization,... 

Vanadium Deactivation of FCC Catalyst Effect of Thermal/Hydrothermal Treatment and V Source... 

For vanadium, the ratios are smaller, and the dynamic density maps do not show a distinct maximum in the cube direction. The difference is attributed to anharmonicity of the thermal motion. Thermal displacement amplitudes are larger in V than in Cr, as indicated by the values of the isotropic temperature factors, which are 0.007 58 and 0.00407 A2 respectively. As in silicon, the anharmonic displacements are larger in the directions away from the nearest neighbors, and therefore tend to cancel the asphericity of the electron density due to bonding effects. 

Vanadium precursors tend to promote addition polymerization of olefins on activation with aluminum co-catalysts. Nomura and coworkers recently reported the first example of catalytic olefin metathesis by a vanadium alkylidene complex.The well-defined, thermally stable V(v) alkylidene complex 7 effected ROMP of NBE at 80 °C. Cettain alkylvanadium complexes, including V(CH2Ph)2(=NAr )(OAr ) (Ar = 2,6-Pr 2C6H3 Ar = 2,6-Me2C6H3) and... 

To understand the effects of the different ligands on V-migration during thermal treatments, vanadyl naphthenate precursor has also been used as dopants. The results for two calcined samples (EuYV(n)AAAC and AAAV(n)EuYC), are presented in Figs. 7 and 8, respectively. In contrast to the results shown in Fig. 1-6, no measurable V migration occurs from the zeolite to the matrix (Fig. 7) and only a trace of V moves from matrix to the zeolite (Fig. 8). Thus vanadium precursors can alter V mobility during calcination... 

Effect of thermal deactivation of vanadium - titanium catalyst on o-xylene oxidation process yielding phthalic anhydride... 

The molecular size distributions and the size-distribution profiles for the nickel-, vanadium-, and sulfur-containing molecules in the asphaltenes and maltenes from six petroleum residua were determined using analytical and preparative scale gel permeation chromatography (GPC). The size distribution data were useful in understanding several aspects of residuum processing. A comparison of the molecular size distributions to the pore-size distribution of a small-pore desulfurization catalyst showed the importance of the catalyst pore size in efficient residuum desulfurization. In addition, differences between size distributions of the sulfur- and metal-containing molecules for the residua examined helped to explain reported variations in demetallation and desulfurization selectivities. Finally, the GPC technique also was used to monitor effects of both thermal and catalytic processing on the asphaltene size distributions. 

Both suggestions seem possible, but a catalytic reaction would seem to be more important. Sughrue et al [39] have shown the existence of that some thermal reactions leading to vanadium deposition is essential to explain the results observed However these effects are, at most, responsible for only ca 5-10% of the total deposit and, as a result, must be regarded as of minor importance below about 430°C [11]. 

ACCUMULATION OF HEAT IN THE VANADIUM CATALYST BED -EFFECTIVE THERMAL CAPACITY OF THE BED... 

Hydrogen reduction of chlorides in thermal plasma can be apphed not only to produce powder of individual metals but also to produce different intermetalhc compounds. The composition of the generated crystals copies the composition of the chloride mixture in the gas phase. This effect permits the production of the intermetallic compounds with the required composition. Refractory intermetallic compounds based on niobium and vanadium were synthesized from their chlorides (conversion close to 100%) in a hydrogen plasma jet generated by RF-ICP discharge (Bashkirov Medvedev, 1968). The reaction products were crystallized on a substrate sustained at a temperature of about 1000°C. The plasma-metallurgical technology is proven to be effective in the synthesis of vanadium-Hsilicon... 

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