New Technologies and Alternative Feedstocks in Petrochemistry and Refining DGMK Conference October 9 – 11, 2013, Dresden, Germany Improved Performance of Nb-doped Vanadyl Pyrophosphate, Catalyst for n- butane Oxidation to Maleic Anhydride G. Pavarelli*, A. Caldarelli*, F. Cavani*, C. Cortelli**, S. Luciani** *Università di Bologna, Dipartimento di Chimica Industriale “Toso Montanari”, Bologna, Italy **Polynt SpA, Via E. Fermi, Scanzorosciate (BG), Italy Abstract Vanadyl pyrophosphate is the main component of the industrial catalyst (V/P/O) for the selective oxidation of n-butane to maleic anhydride. It has been established that the key point to obtain an active and selective catalyst is the in-situ generation, under reaction conditions, of discrete amounts of -VOPO4 on the vanadyl pyrophosphate surface, and that the formation of this compound is favoured in the presence of a slight excess of P [1,2]. In order to further improve the catalytic performance of the industrial catalyst, we doped the vanadyl pyrophosphate with controlled amounts of a Nb5+ compound [3]. Here, we report about an investigation of catalytic performance of V/P/O and Nb-doped V/P/O, carried out by means of both reactivity experiments and in-situ Raman spectroscopy, in order to understand the role of Nb on the generation of the selective phase. Catalytic experiments were carried out with samples having different V/Nb atomic ratios. The effect of Nb on selectivity to maleic anhydride was a function of temperature; in fact, the catalyst having the greater amount of Nb (V/Nb=46) showed the worst performance at all the temperatures tested; however, the sample containing the smaller Nb content (V/Nb=150) showed the highest MA selectivity at low temperature. Finally, at high temperature the catalyst showing the better selectivity was that one with the intermediate Nb content (V/Nb=80). These results showed that the optimum Nb amount in Nb-doped V/P/O is a function of the reaction conditions used. The effects observed were attributed to an in-situ modification of the characteristics of vanadyl pyrophosphate, i.e., of the ratio between V5+ and V4+ species on catalyst surface, the latter being in turn affected by both the gas-phase composition and the Nb content in samples. We hypothesized that Nb5+ affects the in-situ generation of the selective phase, - VOPO4; an excessive amount of the oxidized phase led to a non-selective catalyst, but the generation of a discrete amount of it, in the catalyst containing an intermediate amount of Nb, led to the more selective behavior. In-situ raman experiments confirmed the hypothesized role of the Nb dopant. 1 F. Cavani, S. Luciani, E. Degli Esposti, C. Cortelli, R. Leanza, Chem. Eur. J.16 (2010)
[2] F. Cavani, D. De Santi, S. Luciani, A. Lofberg, E. Bordes-Richard, C. Cortelli,
R. Leanza, Appl. Catal. A376 (2010) 66.
[3] F. Cavani, F. Pierelli, F. Ghelfi, G. Mazzoni, C. Fumagalli, EP 1514598 (2003), assigned
Sivert Eriksson, Mollaryd Ekliden, 524 95 Ljung (son) Agnetha Eriksson, Vintergatan 35, 504 60 Borås (dotter) distriktsläkaren Staffan Svedberg, Vårdcentralen Herrljunga, Horsbyvägen 10, 524 32 Herrljunga NN Filip Eriksson XX, född den 30 mars 1928 och avliden, hade Parkinsons sjukdom och polymyalgia rheumatica. Den 14 december 2004 sökte han Staffan Svedberg dr NN. Han berättade då o
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