负载型氧化钒中V–O位点在非氧化丙烷脱氢反应中的作用

Roles of V–O sites for non-oxidative propane dehydrogenation over supported vanadium oxides

负载型氧化钒(VOx)因其优越的性能,成为非氧化丙烷脱氢(PDH)的替代型催化剂.本文通过在ZrO_(2)、Al_(2)O_(3)和SiO_(2)上构建单体VOx物种探究了V–O位点对PDH反应的作用.通过控制预还原,获得真实反应条件下稳定的V–O结构,包括V–O–载体(V–O–S)、V–OH和V=O位点.通过载体上V密度的调控,发现丙烯生成速率与V–O–S位点数量呈线性相关,表明V–O–S位点在PDH中起决定性作用,而非V–OH和V=O位点.此外,由于V–O–S位点的Lewis酸性差异,ZrO_(2)(8.2×10-3s-1)上V–O–S位点的比活性高于Al_(2)O_(3)(6.7×10-3s-1)和SiO_(2)(2.8×10-3s-1)上V–O–S位点.本工作为探究非氧化丙烷脱氢反应过程中V–O位点的本质特征提供了借鉴.

Supported vanadium oxides(VOx) are alternative candidates for non-oxidative propane dehydrogenation(PDH) owing to their competitive performance.This paper describes the roles of V-O sites on PDH over monomeric VOxspecies supported on ZrO_(2),Al_(2)O_(3)and SiO_(2).With the control of pre-reduction,stable structures of V-O sites are obtained for PDH,including V-O-support(V-O-S),V-OH and V=O sites.By tuning the V densities over individual support,the propylene formation rate shows a linear correlation with the number of the V-O-S site,which indicates the V-O-S site plays a decisive role in PDH rather than V-OH and V=O sites.Moreover,the specific activity per V-O-S site over ZrO_(2)(8.2 ×10-3s-1) is higher than those over Al_(2)O_(3)(6.7 × 10-3s-1) and SiO_(2)(2.8 × 10-3s-1),due to the discrepant Lewis acidity of various V-O-S sites.This research provides a fundamental insight into the intrinsic nature of V-O sites for non-oxidative propane dehydrogenation.