Acid Sites of Phosphorus-Modified Zeosils
Acid Sites of Phosphorus-Modified Zeosils
复制标题
磷改性沸石的酸性位点
DOI：
10.1021/acscatal.1c01588
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发表时间：
2021
期刊：
影响因子：
12.9
通讯作者：
O. Abdelrahman
中科院分区：
文献类型：
--
作者：
G. Kumar;L. Ren;Y. Pang;Xinyu Li;Han Chen;J. Gulbinski;Paul J. Dauenhauer;M. Tsapatsis;O. Abdelrahman
通过固体酸表征、密度泛函理论计算和动力学询问相结合，探测了含磷沸石的酸性位点，确定了其弱布朗斯台德酸性特征。由于酸性位点强度的差异，P-沸石催化异丙醇脱水的探针化学反应比硅铝酸盐沸石慢一个数量级（基于活性位点）。异丙醇脱水过程中丙烯的选择性仍然比硅铝酸盐高 20-30%，这说明了有利于单分子脱水路线的弱酸性磷活性位点的独特性质。无论硅质环境如何，磷活性位点的性质都没有改变，如相同的表观单分子和双分子脱水能垒所示。使用氘代异丙醇进料进行的动力学同位素实验表明，含磷材料上丙烯形成过程中发生了 E2 型消除。含磷沸石和硅铝酸盐之间的动力学同位素效应的比较表明，异丙醇脱水机制没有改变，表观能量势垒的变化归因于磷活性位点上的结合较弱，导致相对不稳定的醇二聚体吸附物。原位烷基胺霍夫曼消除和原位吡啶滴定表征方法均表现出取决于探针分子的特性或浓度的亚磷酸位点计数，这证实了将布朗斯台德酸催化的常见表征技术扩展到弱酸性材料的局限性。
The acid sites of phosphorus-containing zeosils were probed through a combination of solid acid characterization, density functional theory calculations, and kinetic interrogations, establishing their weakly Brønsted-acidic character. Because of the disparity in the acid-site strength, P-zeosils catalyzed the probe chemistry of isopropanol dehydration slower than aluminosilicate zeolites by an order of magnitude on an active-site basis. Propene selectivity during isopropanol dehydration remained 20–30% higher than that of aluminosilicates, illustrating the distinct nature of the weakly acidic phosphorus active sites that favored unimolecular dehydration routes. Regardless of the confining siliceous environment, the nature of phosphorus active sites was unchanged, as indicated by the identical apparent uni- and bimolecular dehydration energy barriers. Kinetic isotope experiments with deuterated isopropanol feeds implicated an E2-type elimination in propene formation on phosphorus-containing materials. The comparison of kinetic isotope effects between phosphorus-containing zeosils and aluminosilicates pointed to an unchanged isopropanol dehydration mechanism, with changes in the apparent energetic barriers attributed to weaker binding on phosphorus-active sites that lead to a relatively destabilized alcohol dimer adsorbate. Bothex situalkylamine Hofmann elimination andin situpyridine titration characterization methods exhibited a phosphorous acid site count that was dependent on the probe molecules’ identity or concentration, underpinning the limitations of extending common characterization techniques for Brønsted acid catalysis to weakly acidic materials.
影响因子：
12.9
作者：
Abdelrahman, Omar A.;Park, Dae Sung;Dauenhauer, Paul J.
通讯作者：
Dauenhauer, Paul J.
影响因子：
4.2
作者：
Kester, Philip M.;Miller, Jeffrey T.;Gounder, Rajamani
通讯作者：
Gounder, Rajamani