III International Conference

PP-I-11to increase of selectivity to ethene due to suppression of it afteroxidation, moreover in the caseof Bi activity rises also. Thus, the maximal yield of ethene 75% (compared to 67% on theunmodified sample) is achieved on the catalyst with the composition V 0.3 Mo 1 Te 0.23 Nb 0.12 Bi 0.05 О х .The genesis of the catalysts follows the common mechanism and includes several stages:(i) formation of individual and mixed oxo-, polyoxo- and heteropoly anions such as TeO 6- 6 ,V 9 TeO 5- 5-6-28 , TeMo 3 V 5 O 27 and TeMo 6 O 24 during mixing of aqueous solutions of APM,AMV, TA and MeX, the composition and structure of these complexes being independent ofadditives nature; (ii) formation of an aqueous slurry when niobium oxalate was added, at thathydrolysis of niobium oxalate is observed but the composition of anions in mother liquorremains practically unchanged, only oxalate complex of VO + 2 is additionally obtained; (iii)condensation of anions into amorphous material with heteropoly anion of the Anderson type[5] as the main building blocks as well as compounds containing individual elements at thedrying stage; (iv) decomposition of the first phase with simultaneous interaction withindividual compounds resulted in formation of two crystalline phases – orthorhombic (M1)and hexagonal (M2) under thermal treatment.The nature of additive has no effect on phase composition of the samples - mixture of M1and M2 phases, but changes M1/M2 ratio in final catalysts and affects the relative content andthe composition of the phase formed during preparation procedure. As an illustration, Table 1gives data for some catalysts improving catalytic property.Table 1. Chemical composition of different phase in V 0.3 Mo 1 Te 0.23 Nb 0.12 Me x -oxide catalysts.Me x Amorphous material М2 М1composition А*,%composition А*,%composition А*,%V 0.27 Mo 1 Te 0.15 Nb 0.03 82 V 0.3 Mo 1 Te 0.31 12 V 0.28 Mo 1 Te 0.08 Nb 0.12 80Ca 0.1 V 0.32 Mo 1 Te 0..1 Nb 0.04 Ca 0.08 70 V 0.51 Mo 1 Te 0.52 Nb 0.06 Ca 0.02 32 V 0.27 Mo 1 Te 0.08 Nb 0.08 51Zr 0.1 V 0.23 Mo 1 Te 0.13 Nb 0.02 83 V 0.34 Mo 1 Te 0.64 15 V 0.24 Mo 1 Te 0.08 Nb 0.12 Zr 0.12 78Bi 0.05 V 0.34 Mo 1 Te 0.13 Nb 0.02 64 V 0.33 Mo 1 Te 0.46 Bi 0.1 8 V 0.3 Mo 1 Te 0.18 Nb 0.11 Bi 0.03 79* - relative content of phase.Acknowledgements. The authors are grateful to G.A. Aleshina for the preparation of thesamples.References1 J.M. Oliver, J.M. Lopez Nieto, P. Botella, A, Mifsud, Appl. Catal. A, 257, 67 (2004).2 Q. Xie, L. Chen, W. Weng, H. Wan, J. Molec. Catal. A, 240, 191 (2005).3 T. Ushikubo, K. Oshima, T. Ihara, H. Amatsu, US Patent 5,534,650 (1996).4 V.V. Malakhov, Kinetika i kataliz, 36, 503 (1995).5 G.Ya. Popova, T.V. Andrushkevich, G.I. Aleshina, L.M. Plyasova, Yu. A. Chesalov,V.V. Malakhov, L.S. Dovlitova, M.I. Khramov, VII Conference «Mechanisms of CatalyticReaction», July 3-8, 2006, Sankt-Peterburg, Russia. Abstracts, CD-ROM. V. 2. P. 7-9.28