Vanadia-alumina

Table 15.1 Extent of oxygen removal during reduction of vanadia/alumina catalysts.

Figure 15.8 Desorption of butane at room temperature in a flow of 2% 02/Ar from vanadia/alumina catalysts after butane dehydrogenation at 873 K and 1 bar.

Nam, Eldridge and Kittrell studied the pore size distribution for vanadia/alumina catalysts for the removal of NOx by reaction with ammonia. The pore size distributions are found to change dramatically as sulfur poisons the de-NOx reaction. The smallest pores (<10 nm in radius) are found (by porosimetry) to be filled first. As a result the surface decreases by up to 90% with 12% sulfur content, although the pore volume decreased by only 20%. The associated de-NOx activity decreased substantially. It was proposed that ammonium sulfate, bisulfate, or aluminum sulfate formed on the surface to deactivate the catalyst. 

Since exploratory experimental work on the interaction of NO with NH3 in air using vanadia-alumina catalyst indicated a large catalyst bed temperature rise, effort was concentrated on this system. Other oxidation catalysts appeared less attractive than vanadia because their known activity for CO and H2 oxidation could cause interference from these... 

Studies were made over a range of temperatures, flow rates, and NH3/NO ratios. The position of the thermocouple probe tip in the catalyst bed was fixed at 0.125 in. of catalyst ahead of the tip. Catalyst bed diameter was 0.128 in., the volume 0.026 cm3. The vanadia-alumina catalyst was the same used for prior work on HC oxidation (I). Am-... 

Innes, W. B., Duffy, R., Exhaust Gas Oxidation on Vanadia Alumina... 

Under these conditions an average yield of 43% was obtained. Increased yields (50-69%) were found with the use of a coprecipitated vanadia-alumina (35 % V2O6-65 % AI2O3) catalyst and with 40-atm. pressure of hydrogen in a continuous high-pressure flow system. The general utility of this reaction was demonstrated by the conversion of n-butyl, f-butyl, n-hexyl, and n-octyl alcohols to corresponding paraffin hydrocarbons. Recently, this work was extended to secondary aliphatic, as well as aromatic alcohols, with similar results (4)-... 

Since vanadium oxide had been used as an effective catalyst for the dehydrogenation of hydrocarbons, it was expected from purely thermodynamic considerations that conditions could be found for the reverse reaction of hydrogenation to take place. Experiments carried out in our laboratory with coprecipitated vanadia-alumina catalyst showed this to be true. 

The x-ray diffraction pattern of the coprecipitated vanadia-alumina catalyst 6) showed that the amount of vanadium trioxide formed by the reduction of the pentoxide increases rapdily as the temperature of reduction approaches 400°. In fact all three phenomena, the absorption of hydrogen. 

Examples of space velocities used for heavy-duty diesel applications with vanadia SCR catalysts are in the range 20,000-70,000 h [6, 18, 34, 35]. Havenith et al. [6] used 51 dm of washcoated vanadia/alumina SCR catalyst volume, corresponding to a space velocity of 28,000 h for a 12 1 heavy-duty engine, van Helden et al. [35] used 34 dm of washcoated vanadia SCR catalyst volume (space velocity 45,000 h ) for a 12.0 and a 12.6 1 heavy-duty engine. Hofmann et al. [36] used the same SCR catalyst volume (34 dm ), but with a fully extruded vanadia SCR catalyst for a 12 1 heavy-duty diesel engine. 

Planar model catalysts with similar compositions (such as vanadia-silica, vanadia-alumina on NiAl(l 10), and vanadia on Ce02(l 11) monocrystal faces) have been recently investigated with surface science techniques such as infrared reflection absorption spectroscopy Although the authors claim that these studies... 

Oxidation of benzothiophene by tert-butyl hydroperoxide over vanadia-alumina catalyst... 

Figure 18.20. FTIR spectra of (a) BT and (b) TBHP adsorbed on, and (c) TBH-I-BT coadsorbed on vanadia-alumina (d) subtraction c-b.

Gomez-Bernal, H., Cedeno-Caero, L., Finocchio, E., et al. (2009). Oxidation of benzothio-phene by tert-butyl hydroperoxide over vanadia-alumina catalyst An FTIR study at the vapour-solid interface, Catal, Commun., 10, pp. 1629-1632. 

Shiju, N., Anilkumar, M., Mirajkar, S., ef al. (2005). Oxidative dehydrogenation of ethylbenzene over vanadia-alumina catalysts in the presence of nitrous oxide structure-activity relationship, J. Catal., 230, pp. 484-492. 

Flg.2.-f-plots for the vanadia-alumina samples with 6% Na (ref. 6%Na-doped alumina... 

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