Continuous Hydrogenation of Maltose over Raney Ni in a Trickle-Bed Reactor

Abstract

Maltitol has been identified as an important value-added chemical with versatile applications and is typically manufactured via the catalytic hydrogenation of maltose, which is in urgent need of upgrading from batch to continuous operation to boost production efficiency. Here we propose a viable continuous approach for maltose hydrogenation in a trickle-bed reactor applying a millimeter-scale Raney Ni. The parametric study was performed at various temperatures, liquid flow rates, initial maltose concentrations, pressures, and hydrogen flow rates to maximize the catalytic performance and optimize the product distribution. Under the optimal reaction conditions, generally excellent conversion of maltose (91.0%) and a high yield of maltitol (87.9%) were obtained. Furthermore, a continuous hydrogenation of concentrated maltose proceeded properly, providing a slight reduction in maltose conversion but satisfactory space time yield of maltitol (0.150 gmaltitol gcat –1 h–1). Detailed kinetics and density functional theory calculations were combined to unravel the reaction mechanism of maltose hydrogenation. The continuous flow system based on a trickle-bed reactor proved to have high durability and remarkable substrate suitability, thus demonstrating a reliable scale-up capability for the industrial utilization of biomass-derived sugars.