In-situ electron spin resonance study of vanadium phosphate catalysts during the selective oxidation of n-butane to maleic anhydride

被引:27
作者
Bruckner, A [1 ]
Kubias, B [1 ]
Lucke, B [1 ]
Stosser, R [1 ]
机构
[1] HUMBOLDT UNIV BERLIN,INST PHYS & THEORET CHEM,D-10115 BERLIN,GERMANY
关键词
disorder; in-situ ESR; selective n-butane oxidation; vanadium phosphate catalysts;
D O I
10.1016/0927-7757(96)03607-2
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Differently disordered (VO)(2)P2O7 phases and an amorphous V3+PO catalyst were studied by electron spin resonance (ESR) spectroscopy at various temperatures and in various atmospheres, as well as under catalytic conditions, using an in-situ ESR flow reactor operating in the X band. Exchange integrals and the second and fourth moments of the ESR signals were used to characterize spin-spin exchange in (VO)(2)P2O7, which depends on the degree of structural disorder. The catalytic activity of (VO)(2)P2O7 and the maleic anhydride selectivity are enhanced with rising disorder. During butane oxidation a significant reversible alteration of the ESR line shape became evident. This unique effect can only be observed under working conditions and is discussed in terms oi a perturbation of exchange interactions between neighbouring vanadyl centres near the surface, the oxidation state of which is assumed to fluctuate between +4 and +5 during the catalytic reaction. In contrast, heating in pure air improves the spin-spin exchange and lowers the disorder by healing lattice defects. The activity of the V3+PO catalyst in the title reaction ''awoke'' after about 20 min time on stream, simultaneous with the formation of a (VO)(2)P2O7-like local arrangement of V4+ centres on the catalyst surface.
引用
收藏
页码:179 / 186
页数:8
相关论文
共 17 条
  • [1] A STUDY BY INSITU LASER RAMAN-SPECTROSCOPY OF VPO CATALYSTS FOR NORMAL-BUTANE OXIDATION TO MALEIC-ANHYDRIDE .1. PREPARATION AND CHARACTERIZATION OF PURE REFERENCE PHASES
    BENABDELOUAHAB, F
    OLIER, R
    GUILHAUME, N
    LEFEBVRE, F
    VOLTA, JC
    [J]. JOURNAL OF CATALYSIS, 1992, 134 (01) : 151 - 167
  • [2] Bielanski A., 1991, OXYGEN CATALYSIS, DOI DOI 10.1201/9781482293289
  • [3] NATURE OF THE ACTIVE AND SELECTIVE SITES IN VANADYL PYROPHOSPHATE, CATALYST OF OXIDATION OF N-BUTANE, BUTENE AND PENTANE TO MALEIC-ANHYDRIDE
    BORDES, E
    [J]. CATALYSIS TODAY, 1993, 16 (01) : 27 - 38
  • [4] BRUCKNER A, 1993, EUR J SOL STATE INOR, V30, P801
  • [5] NATURE AND MECHANISM OF FORMATION OF VANADYL PYROPHOSPHATE - ACTIVE PHASE IN NORMAL-BUTANE SELECTIVE OXIDATION
    BUSCA, G
    CAVANI, F
    CENTI, G
    TRIFIRO, F
    [J]. JOURNAL OF CATALYSIS, 1986, 99 (02) : 400 - 414
  • [6] VANADYL PYROPHOSPHATE CATALYSTS - PREFACE
    CENTI, G
    [J]. CATALYSIS TODAY, 1993, 16 (01) : 1 - 4
  • [7] PHYSICOCHEMICAL CHARACTERIZATION AND CATALYTIC BEHAVIOR OF VPO FORMULATIONS
    CORNAGLIA, LM
    CASPANI, C
    LOMBARDO, EA
    [J]. APPLIED CATALYSIS, 1991, 74 (01): : 15 - 27
  • [8] DRAGER K, 1977, Z NATURFORSCH A, V32, P163
  • [9] GROKE D, 1995, CONSORTIUM ELEKTROCH
  • [10] PREPARATION AND CHARACTERIZATION OF VO(HPO4).0.5H2O AND ITS TOPOTACTIC TRANSFORMATION TO (VO)2P2O7
    JOHNSON, JW
    JOHNSTON, DC
    JACOBSON, AJ
    BRODY, JF
    [J]. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1984, 106 (26) : 8123 - 8128