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Effect of the structural modification by carbiding of alumina supported Anderson-type (NH4)4[NiMo6 − xWxO24H6]·5H2O on hydrodesulfurization, hydrodechlorination and selective oxidation

Abstract:

The γ-Al<inf>2</inf>O<inf>3</inf>-supported Anderson-type complexes (NH<inf>4</inf>)<inf>4</inf>[NiMo<inf>6 − x</inf>W<inf>x</inf>O<inf>24</inf>H<inf>6</inf>]·5H<inf>2</inf>O (x = 0, 3 or 6) were carburized with CH<inf>4</inf>/H<inf>2</inf> (1:4) mixture (denoted by NiMo<inf>6 − x</inf>W<inf>x</inf>-C/Al). These solid compounds have been tested in a continuous flow, fixed bed reactor for thiophene hydrodesulfurization and polychlorinated biphenyls hydrodechlorination, and in (semi-) batch reactor for dibenzothiophene selective oxidation. The specific surface area and pore volume of NiMo<inf>6</inf>-C/Al were greater than those of NiW<inf>6</inf>-C/Al and NiMo<inf>3</inf>W<inf>3</inf>-C/Al. XRD results evidenced a bulk structure typical of Mo<inf>2</inf>C, W<inf>2</inf>C, WC and NiC. FT-IR verified the absence of bands corresponding to metal oxides. Generally, the catalytic activity toward a given reaction product of NiMo<inf>6</inf>-C/Al was greater than those of NiW<inf>6</inf>-C/Al and NiMo<inf>3</inf>W<inf>3</inf>-C/Al due either to its better textural properties or to a more complete transformation of the metal phases into active ones.