Laboratory for Femtochemistry and Synchrotron Radiation, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland.
Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering, ETH Zurich, HCI E 127, Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland.
Nat Commun. 2017 Jun 29;8:15946. doi: 10.1038/ncomms15946.
Catalytic fast pyrolysis is a promising way to convert lignin into fine chemicals and fuels, but current approaches lack selectivity and yield unsatisfactory conversion. Understanding the pyrolysis reaction mechanism at the molecular level may help to make this sustainable process more economic. Reactive intermediates are responsible for product branching and hold the key to unveiling these mechanisms, but are notoriously difficult to detect isomer-selectively. Here, we investigate the catalytic pyrolysis of guaiacol, a lignin model compound, using photoelectron photoion coincidence spectroscopy with synchrotron radiation, which allows for isomer-selective detection of reactive intermediates. In combination with ambient pressure pyrolysis, we identify fulvenone as the central reactive intermediate, generated by catalytic demethylation to catechol and subsequent dehydration. The fulvenone ketene is responsible for the phenol formation. This technique may open unique opportunities for isomer-resolved probing in catalysis, and holds the potential for achieving a mechanistic understanding of complex, real-life catalytic processes.
催化快速热解是将木质素转化为精细化学品和燃料的一种很有前途的方法，但目前的方法缺乏选择性，转化率也不理想。在分子水平上理解热解反应机制可能有助于使这个可持续的过程更经济。反应中间体负责产物的支化，是揭示这些机制的关键，但它们的异构体选择性检测非常困难。在这里，我们使用同步辐射光电离光电子符合光谱法研究了木质素模型化合物愈创木酚的催化热解，这种方法可以对反应中间体进行异构体选择性检测。结合常压热解，我们确定富烯酮是中心反应中间体，由催化脱甲基生成邻苯二酚和随后的脱水生成。富烯酮烯酮负责苯酚的形成。这项技术可能为催化剂中的异构体分辨探测开辟独特的机会，并有可能实现对复杂的实际催化过程的机理理解。
