Continuous Hydrogenation of <scp>l</scp> -Alanine in a Micropacked Bed Reactor

l-alaninol is a crucial chiral intermediate for the synthesis of levofloxacin. The traditional batch hydrogenation process of l-alanine suffers from drawbacks such as low mass transfer efficiency, large equipment volume, and harsh reaction conditions. Therefore, it is of great significance to develop a mild and efficient continuous hydrogenation process for l-alanine. In this study, the continuous hydrogenation of l-alanine was investigated for the first time in a micropacked bed reactor. The effects of catalyst type, pressure, temperature, and phosphoric acid dosage on the reaction were systematically investigated. The results showed that the ruthenium-supported activated carbon catalyst (Ru/C) exhibited superior catalytic performance. The complete conversion (100%), high selectivity (96.7 to 100%), and outstanding optical purity (99%) were obtained under mild reaction conditions (95 °C, 5 MPa, and the residence time of 14.7 min). Furthermore, this study eliminated the effects of internal and external diffusion and established an intrinsic kinetic model, which fills the gap in kinetic research under the continuous reaction system. In addition, this process was extended to the hydrogenation of l-2-aminobutyric acid and β-alanine, and excellent results were obtained.