Investigation of vanadium phosphorus oxide catalysts (VPO) during toluene ammoxidation: New mechanistic insights by in situ EPR

被引:34
作者
Bruckner, A
Martin, A
Steinfeldt, N
Wolf, GU
Lucke, B
机构
来源
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS | 1996年 / 92卷 / 21期
关键词
D O I
10.1039/ft9969204257
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
(VO)(2)P2O7, differently prepared (NH4)(2)(VO)(3)(P2O7)(2) samples and supported amorphous vanadium phosphorus oxide (VPO) catalysts were investigated during the ammoxidation of toluene using a self-constructed in situ EPR how reactor in the X-band. For the unsupported catalysts, changes in the spin-spin exchange behaviour were analysed by calculating the quotient of the 4th and the square of the 2nd moment, [B-4]/[B-2](2), of th, absorption signal. The catalytic activity was found to increase with exchange efficiency, while isolated vanadyl centres, as present in the supported catalysts, do not obviously participate in the catalytic process. NH4+ containing catalysts can easily supply ammonia for N insertion into the hydrocarbon indicating that the latter does not react directly with NH3 molecules from the gas phase but with those activated by adsorption on the surface of the catalyst according to a Langmuir-Hinshelwood mechanism.
引用
收藏
页码:4257 / 4263
页数:7
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