Vanadium pentoxide with oxygen

However, one should not conclude from this that vanadium pentoxide oxygen participates in the oxidation of sulfur dioxide, since it has been shown that SO 3 exchanges with the oxygen of vanadium pentoxide with a rate much higher compared to the rate of oxidation of sulfur dioxide. This fact strongly complicates the studying of the participation of oxide oxygen in this reaction. 

Metallurgy. — Metallic vanadium may be prepared in a number of ways. (1) By reduction of vanadium dichloride by pure hydrogen. This method is difficult to use because at red heat vanadium unites readily with oxygen and water, so both must be carefully excluded. (2) By making a plastic mass of vanadium pentoxide with carbon and paraffin, shaping into rods and passing the electric current through them in a vacuum. 

Commercially, maleic anhydride is prepared more cheaply by the catalytic vapour phase oxidation (in the presence of vanadium pentoxide at about 400°) of benzene with atmospheric oxygen ... 

Vanadium Carbide. Vanadium pentoxide [1314-62-17, V2O5, or vanadium trioxide [1314-34-7] VO3, are the most satisfactory oxides for the preparation of VC. Vanadium pentoxide is best prepared by igniting chemically pure ammonium vanadate [7803-55-6] NH VO, in the presence of moist oxygen to avoid reaction with nitrogen V2O3 is obtained by reduction of V2O3 with hydrogen (see Vanadium compounds). 

The ethyl ester is prepared in 60 per cent yield by passing ethyl lactate with air or oxygen over a vanadium pentoxide catalyst. Boehringer Sohn, U. S. pat. 1,614,195 (1927). [C. A. ai, 746 (1927).]... 

Vanadium pentoxide has been investigated for 30 years ° ° it has a layered structure with weak vanadium—oxygen bonds between the layers and is now known to react by an intercalation mechanism 40,85 + V2O5 = LLV2O5. 

Sulfur dioxide combines with oxygen on heating and in the presence of a catalyst. This reaction proceeds at temperatures between 400 to 700°C with vanadium pentoxide catalyst to make sulfuric acid ... 

Halogenation in the presence of sulphur, or by means of sulphur halides, is also available. When chlorine is conducted into a mixture of vanadium pentoxide and sulphur, or when powdered vanadium pentoxide is treated with sulphur monochloride vapours, an immediate reaction sets in, with formation of vanadium oxytrichloride.2 A quantitative yield of this compound is also obtained when vanadium trichloride is heated in oxygen at 500° to 600° C.3... 

In the process (Fig. 1), sulfur and oxygen are converted to sulfur dioxide at 1000°C and then cooled to 420°C. The sulfur dioxide and oxygen enter the converter, which contains a catalyst such as vanadium pentoxide (V205). About 60 to 65% of the sulfur dioxide is converted by an exothermic reaction to sulfur trioxide in the first layer with a 2 to 4-second contact time. The gas leaves the converter at 600°C and is cooled to 400°C before it enters the second layer of catalyst. After the third layer, about 95% of the sulfur dioxide is converted into sulfur trioxide. The mixture is then fed to the initial absorption tower, where the sulfur trioxide is hydrated to sulfuric acid after which the gas mixture is reheated to 420°C and enters the fourth layer of catalyst that gives overall a 99.7% conversion of sulfur dioxide to sulfur trioxide. It is cooled and then fed to the final absorption tower and hydrated to sulfuric acid. The final sulfuric acid concentration is 98 to 99% (1 to 2% water). A small amount of this acid is recycled by adding some water and recirculating into the towers to pick up more sulfur trioxide. 

Fig. 25. A1 ternative toluene chemisorption systems involving the bipyramidal surface cluster of vanadium pentoxide. The structures (a, c, e, g, i) represent molecularly adsorbed toluene, while the remaining systems (b, d, f, h) model the dissociative adsorption, with two methyl hydrogens chemically bonded to the surface oxygens at the pyramid bases. Asterisks indicate positions which give rise to unstable MEC. The three atoms of the parallel complex (i), marked with an arrow, denote the extra instabilities appearing when the closed-system constraint (d N = 0) is imposed. The results are taken from Ref. 8. At each diagram the (I, E) stability diagnosis is also indicated (see Fig. 24)...

In oxide materials [2] which are fused for catalytic applications, two additional factors contribute to the unique features of this preparation route. Many oxides in their liquid states are thermodynamically unstable with respect to the oxygen partial pressure present in ambient air, i.e. they decompose into lowcr-valcnt oxides and release molecular oxygen into the gas phase. This process can be fast on the time-scale of the fusion process, such as with vanadium pentoxide or man-... 

The reaction of gaseous SO2 with molecular oxygen in the contact process seems to proceed over two independent mechanisms [13] one of which is the direct oxidation of a vanadium pentoxide-sulfur dioxide adduct by oxygen and the other proceedings via a redox cycle involving V4+ and V3+ intermediate species [13-15]. 

---