Selective Oxidation of n-Butane on a V–P–O Catalyst: Study under Fuel-Rich Conditions

Author： Mota S. Abon M. Volta J.C. Dalmon J.A.

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.193, Iss.2, 2000-07, pp. : 308-318

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Abstract

A vanadium pyrophosphate oxide (V–P–O) catalyst has been tested for n-butane oxidation under fuel-rich conditions (O₂/C₄H₁₀=0.6). A rapid decrease in maleic anhydride production was observed with time. XPS analysis showed that this was associated with a rapid reduction of the catalyst surface. From the evolution of the distribution of products, it has been inferred that CO formation mainly occurs by the oxidation of adsorbed butane whereas CO₂ is formed by the overoxidation of maleic anhydride. It has been concluded that the n-butane activation occurs on V⁴⁺ sites while the insertion of oxygen in the C₄-intermediates leading to MA takes place on V⁵⁺ sites. The deactivation in fuel-rich conditions is not so drastic when the V–P–O catalyst has been previously oxidized at a relatively low temperature (500°C). In this case oxygen is stored in the V–P–O surface region, hence favoring the specific O-inserting role of V⁵⁺ responsible for MA formation.