Determination of the maximum monolayer dispersion and dispersed state for WO3 on γ-Al2O3
Determination of the maximum monolayer dispersion and dispersed state for WO3 on γ-Al2O3作者机构：Institute of Physical Chemistry Peking University Beijing
出 版 物：《Chinese Journal of Chemistry》 (中国化学(英文版))
年 卷 期：1985年第3卷第4期
页 面：313-320页
摘 要：The maximum monolayer dispersion（the threshold）for WOon γ-AlOcalcined at500°,550°,600°,and 640℃ has been determined quantitatively by XRD（amount of crystallinephase）and XPS(intensity ratios I/I).The results show that if the amount of WOloadedis lower than the maximum monolayer dispersion,WOwill react with γ-AlOto form surface com-pound due to mutual ionic interaction,and will be dispersed on γ-AlOsurface as monolayer *** case the amount is higher than this value,the residual crystalline WOwill *** max-imum monolayer dispersion（threshold）is 0.21 g and 0.20 g WO/100 mγ-AlOby NRD andXPS *** agrees with the value(0.189 g WO/100 mor 4.90×10W atoms/m)cal-culated from the model on assumption that the WOis dispersed as a closed-packed monolayer onγ-*** as WO/γ-AlOsystem is stable up to higher temperature,e.g.700℃,than MoO/γ-AlOsystem,WOseems unfavorable to form new buIk compound with γ-AlOatthat ***,Al（MoO）forms perceptibly in MoO/γ-AlOsystem at 500℃.Besides,the size of residual crystalline WOin WO/γ-AlOis much smaller than that of MoOinMoO/γ-*** might be the reason that WO/γ-AlOcatalyst is superior to MoO/γ-AlOinhydrodesulfurization（HDS）or hydrodenitrogenation（HDN）in some cases.
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