Chase Emily, Notestein Justin
Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL, 60208, USA.
Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA.
Chemphyschem. 2025 Jan 2;26(1):e202400690. doi: 10.1002/cphc.202400690. Epub 2024 Nov 11.
On supported metal catalysts such as Zr-SiO, it can be challenging to isolate characteristics that result from intrinsic properties of the active site from those that result from the environment surrounding the active site. In this report, we utilize in situ titration of Lewis acid sites with phosphonic acid to accurately and quantitatively describe kinetically relevant Zr species on Zr-SiO materials for the MPV reduction of cyclohexanone. We find that rate of MPV reduction on Zr-SiO materials can be described as a combination of rate over titratable Zr, that is likely well dispersed Zr, and rate over non-titratable Zr, that is likely supported ZrO. The fraction of Zr that is well dispersed on the SiO is dependent on the surface density at which Zr is grafted but not the choice of Zr precursor. We demonstrate that phosphonic acid titration can offer a more relevant, quantitative description of Zr dispersion than UV-vis and can be used to quantitatively describe changes that occur to the material during regeneration.
在诸如Zr-SiO等负载型金属催化剂上，要将活性位点的固有性质所导致的特征与活性位点周围环境所导致的特征区分开来可能具有挑战性。在本报告中，我们利用膦酸对路易斯酸位点进行原位滴定，以准确、定量地描述Zr-SiO材料上与动力学相关的Zr物种，用于环己酮的MPV还原反应。我们发现，Zr-SiO材料上MPV还原反应的速率可以描述为可滴定Zr（可能是高度分散的Zr）上的速率与不可滴定Zr（可能是负载的ZrO）上的速率之和。在SiO上高度分散的Zr的比例取决于Zr接枝的表面密度，而不是Zr前驱体的选择。我们证明，膦酸滴定比紫外可见光谱能提供更相关、定量的Zr分散描述，并且可用于定量描述材料在再生过程中发生的变化。
