转换数和转换频率概念的有效性与局限性

Effectiveness and Limitations of Turnover Number and Turnover Frequency

转换数(TON,turnover number)和转换频率(TOF,turnover frequency)是催化研究中经常碰到的2个概念,一般认为TON是单位活性位点所能转化的反应物分子的数目,TOF是TON除以完成这些转化所需要的时间。TON和TOF可用于评价催化剂的稳定性和活性。针对均相催化、多相催化和酶催化中的TON和TOF进行了讨论,并对相关的S/C(substrate/catalyst)、催化剂摩尔分数、TTN(total turnover number)、STY(site time yield)等概念进行了说明。

Turnover number(TON) and turnover frequency(TOF) are the two concepts that can be encountered in the research of catalysis. It is normally accepted that TON is the number of reactant molecules that can be transformed per active site and TOF is the ratio of TON and the time to accomplish these transformations. TON and TOF can be used to evaluate the stability and activity of catalyst. In this paper, the TON and TOF in the homogeneous catalysis, heterogeneous catalysis and enzyme catalysis have been discussed and the related metrics, such as S/C, the molar percent of catalyst, TTN(total turnover number) and STY(site time yield) are also explained.