A new method was employed for the preparation of a set of lanthanum cobaltites of general formula La1-xMxCoO3+ with M=Ce, Eu and x=0, 0.05, 0.1, 0.2. All the samples so prepared showed nanostructured, thermally very stable and characterised by highly crystalline perovskite-like structure and high surface area. Their activity as catalysts for the catalytic flameless combustion of methane was by ca. one order of magnitude higher than that of their analogues, prepared through the usual calcination-milling procedure.Adsorption of oxygen was accompanied by formation of paramagnetic species. Desorption of preadsorbed oxygen was dependent on the nature of the doping element and on the value of the stoichiometric coefficient x of their formula. A correlation between the temperature of the maximal rate of oxygen release and catalytic activity was found. The following scale of activity for the title reaction vs. x values could be set up: 0.1 Ce > 0.05 Ce > 0 > 0.05 Eu > 0.1 Eu  0.2 Ce. The higher activity of Ce-doped catalysts as compared to those doped with Eu was found to be related to the strength of the bond between oxygen and Co ions.

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This work focused on investigating the effect of the P/V atomic ratio in vanadyl pyrophosphate, catalyst for n-butane oxidation to maleic anhydride, on the nature of the catalytically active phase. Structural transformations occurring on the catalyst surface were investigated by means of in situ Raman spectroscopy in a non-reactive atmosphere, as well as by means of steady-state and non-steady-state reactivity tests, in response to changes in the reaction temperature. It was found that the nature of the catalyst surface is affected by the P/V atomic ratio even in the case of small changes in this parameter. With the catalyst having P/V equal to the stoichiometric value, a surface layer made of alpha(Iota)-VOPO(4) developed in the temperature interval 340-400 degrees C in the presence of air; this catalyst gave a very low selectivity to maleic anhydride in the intermediate T range (340-400 degrees C). However, at 400-440 degrees C delta-VOPO(4) overlayers formed; at these conditions, the catalyst was moderately active but selective to maleic anhydride. With the catalyst containing a slight excess of P, the ratio offering the optimal catalytic performance, delta-VOPO(4) was the prevailing species over the entire temperature range investigated (340-440 degrees C). Analogies and differences between the two samples were also confirmed by reactivity tests carried out after in situ removal and reintegration of P. These facts explain why the industrial catalyst for n-butane oxidation holds a slight excess of P; they also explain discrepancies registered in the literature about the nature of the active layer in vanadyl pyrophosphate.

We present herein results from a campaign (>1500 h) of o-xylene oxidation runs in a 1 in. single-tube technical fixedbed pilot reactor (i.d. = 24.6 mm) loaded with 16 washcoated (V 2 O 5 /TiO 2 ) monolithic catalysts with Al honeycomb supports (each 10 cm long) and operated at typical industrial conditions for PA (phthalic anhydride) production. The highly conductive monolithic supports afforded substantially reduced axial T-gradients in comparison with reference runs in the same pilot reactor loaded with conventional egg-shell ring catalyst pellets, the maximum T-difference with the salt bath being halved at the same hot spot temperature (∼440 °C) and the mean bed temperature being about 20 °C higher. Temperature gradients were still moderate at an o-xylene feed concentration of 80 g/Nm 3 (at Q air = 4 N m 3 /h), which represents an upper limit for industrial PA packed-bed reactors loaded with the same V 2 O 5 /TiO 2 catalyst coated onto ring pellets. Operation at higher o-xylene feed contents (up to 95 g/Nm 3 ) was found feasible. The Al honeycomb catalysts were successfully unloaded at the end of the runs. The strong (∼2-fold) enhancement of radial heat transfer rates associated with the adoption of highly conductive monolith catalyst supports is thus herein demonstrated at a fully representative industrial scale for the first time. It can be exploited, for instance, either to increase the o-xylene feed concentration, possibly above 100 g/Nm 3 (and the PA productivity accordingly), within a retrofitting strategy, or to design new reactors with larger tube diameters, resulting in reduced investment costs.