Khan Mahmudul H, Fard Zeinab H, Kohler Andrew J, Roling Luke T, Shanks Brent H
Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, United States.
Center for Biorenewable Chemicals (CBiRC), Ames, Iowa 50011, United States.
ACS Catal. 2025 Aug 22;15(17):15488-15501. doi: 10.1021/acscatal.5c04264. eCollection 2025 Sep 5.
Ambient pressure hydrodeoxygenation (HDO) of lignin-derived oxygenates over molybdenum oxide-based catalysts is an effective strategy to produce chemicals that can be directly integrated into our existing petrochemical infrastructure. Complexities pertaining to the simultaneous kinetic and mechanistic analysis of HDO have limited research endeavors to single-compound systems. Although valuable insight into the catalytic reaction has been gained through this approach, it provides limited understanding of the competitive adsorption behavior manifest in a realistic multioxygenate reaction environment. To address this shortcoming, simultaneous gas-phase acetone and anisole HDO was performed at 330 °C and ≤1 bar H partial pressure over bulk MoO. Propene, propane, and benzene were the HDO products formed, showing a similar product distribution to the single-compound system. Selectivity to propene and propane was ∼14 times higher than benzene, even at three times higher anisole partial pressure compared to acetone. A negative anisole HDO (-0.97 ± 0.22) rate order with varying acetone partial pressure suggested a strong inhibition effect on anisole HDO by acetone. Conversely, with increasing anisole partial pressure, a rate order of -0.07 ± 0.12 was observed for acetone HDO, implying a weak impact of anisole cofeed on acetone HDO. A kinetic-driven approach was taken to estimate the relative adsorption constants of the oxygenates. Acetone exhibited a 6.4 times higher adsorption propensity on the HDO active site than anisole. Relative adsorption constants for phenolics increased with increasing basicity of the oxygenate but decreased for aliphatic molecules, suggesting a volcano-shaped relationship. The results suggest the possibility of an optimal electron density around the molecule's oxygen atom to maximize the molecule's adsorption strength.
在基于氧化钼的催化剂上对木质素衍生含氧化合物进行常压加氢脱氧（HDO）是一种有效的策略，可用于生产能够直接融入现有石化基础设施的化学品。HDO同时进行动力学和机理分析的复杂性，使得研究工作局限于单化合物体系。尽管通过这种方法已经获得了关于催化反应的宝贵见解，但它对在实际多含氧化合物反应环境中表现出的竞争吸附行为的理解有限。为了解决这一缺点，在330℃和氢气分压≤1巴的条件下，在块状MoO₃上同时进行气相丙酮和苯甲醚的HDO。丙烯、丙烷和苯是形成的HDO产物，其产物分布与单化合物体系相似。即使苯甲醚分压是丙酮的三倍，对丙烯和丙烷的选择性也比对苯高约14倍。随着丙酮分压的变化，苯甲醚HDO的反应速率为负（-0.97±0.22），这表明丙酮对苯甲醚HDO有很强的抑制作用。相反，随着苯甲醚分压的增加，丙酮HDO的反应速率为-0.07±0.12，这意味着苯甲醚共进料对丙酮HDO的影响较弱。采用动力学驱动的方法来估计含氧化合物的相对吸附常数。丙酮在HDO活性位点上的吸附倾向比苯甲醚高6.4倍。酚类化合物的相对吸附常数随着含氧化合物碱性的增加而增加，但脂肪族分子的相对吸附常数则降低，这表明存在火山形关系。结果表明，分子氧原子周围可能存在最佳电子密度，以使分子的吸附强度最大化。
