Harju Heikki, Pipitone Giuseppe, Lefferts Leon
Department of Chemical and Metallurgical Engineering, Aalto University, Espoo, Finland.
Catalytic Processes and Materials, Department of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente, Enschede, Netherlands.
Front Chem. 2020 Jan 28;8:17. doi: 10.3389/fchem.2020.00017. eCollection 2020.
Butanol is a by-product obtained from biomass that can be valorized through aqueous phase reforming. Rh/ZrO catalysts were prepared and characterized, varying the size of the support particles. The results showed a relatively mild effect of internal mass transport on butanol conversion. However, the influence of internal transport limitations on the product distribution was much stronger, promoting consecutive reactions, i.e., dehydrogenation, hydrogenolysis, and reforming of propane and ethane. Hydrogen consuming reactions, i.e., hydrogenolysis, were more strongly enhanced than hydrogen producing reactions due to internal concentration gradients. Large support particles deactivated faster, attributed to high concentrations of butyraldehyde inside the catalyst particles, enhancing deposit formation via aldol condensation reactions. Consequently, also the local butyric acid concentration was high, decreasing the local pH, enhancing Rh leaching. The influence of internal transfer limitation on product distribution and stability is discussed based on a reaction scheme with three main stages, i.e., (1) formation of liquid intermediates via dehydrogenation, (2) formation of gas via decarbonylation/decarboxylation reactions, and (3) hydrocarbon hydrogenolysis/reforming/dehydrogenation.
丁醇是一种从生物质中获得的副产品，可通过水相重整实现增值利用。制备并表征了不同载体颗粒尺寸的Rh/ZrO催化剂。结果表明，内扩散对丁醇转化率的影响相对较小。然而，内扩散限制对产物分布的影响要强得多，会促进丙烷和乙烷的连续反应，即脱氢、氢解和重整。由于内浓度梯度，消耗氢的反应（即氢解）比产氢反应增强得更强烈。较大的载体颗粒失活更快，这归因于催化剂颗粒内部丁醛的高浓度，通过羟醛缩合反应增强了沉积物的形成。因此，局部丁酸浓度也很高，降低了局部pH值，增强了Rh的浸出。基于一个包含三个主要阶段的反应方案，即(1)通过脱氢形成液体中间体，(2)通过脱羰/脱羧反应形成气体，以及(3)烃类氢解/重整/脱氢，讨论了内扩散限制对产物分布和稳定性的影响。
