酸强度对固体酸的异构化和消除催化作用的后果
Josef Macht1, Robert T Carr, Enrique Iglesia
1Department of Chemical Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|April 21, 2009
概括
固体酸强度,以脱质能 (DPE) 衡量,影响了诸如异构化和酒精脱水等催化反应. 随着DPE的使用,反应障碍增加,但静电稳定效应会降低弱酸对酸强度的敏感性.
科学领域:
- 不同质的催化剂.
- 固体酸化学 固体酸化学
- 表面科学是一门学科.
背景情况:
- 固体酸如化物和聚氧甲酸 (POMs) 在工业催化中至关重要.
- 了解催化剂酸强度如何影响反应机制对于催化剂设计至关重要.
- 脱能 (DPE) 提供了一个严格的测量固体酸强度.
研究的目的:
- 为了研究固体酸强度 (DPE) 与异构和脱水的动力学之间的关系.
- 确定DPE如何影响激活障碍,过渡状态和反应速率.
- 阐明静电稳定在调节酸强度灵敏度中的作用.
主要方法:
- 使用Keggin POM集群和具有已知的结构的热岩.
- 测量反应动力学 (速率和平衡常数) 对于n-hexane异构化和醇脱水.
- 使用脱质能 (DPE) 和定位方法量化酸强度.
- 分析过渡状态能量和热化学性质.
主要成果:
- 反应速率常数下降,激活障碍随着DPE增加而增加,无论是异构化还是脱水.
- 过渡状态下的离子对的静电稳定部分抵消了DPE带来的屏障预期增加.
- 氧化醇异构化障碍物对DPE比酒精脱水障碍物更敏感.
- 较慢的反应不一定与对酸强度更高的敏感性相关.
结论:
- 催化反应对固体酸强度的敏感性在过渡状态下通过静电稳定来调节.
- 在过渡状态下有机的电荷密度会影响静电稳定程度.
- 气相质子亲和力不仅仅决定了反应对固体催化剂酸强度的敏感性.
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