Optimal design of a simulated-moving-bed separation process for economical production of xylitol from bamboo-hydrolysis byproducts

Abstract

Xylitol, which is one of industrially useful sugar-alcohols, has received constant attention from various industries. For the eco-friendly and economical production of xylitol, the byproducts from bamboo hydrolysis treatments for bioethanol-production purposes can be utilized as the source for xylitol. Since such bamboo-hydrolysis byproducts were reported to consist of several polyols such as xylitol, xylose, and glycerol, one essential requirement for ensuring a large-scale production of xylitol will be to secure a highly-efficient process for separation of xylitol from the above-mentioned polyol mixture. To address this issue, we aimed to establish an optimal simulated-moving-bed (SMB) process that can accomplish the xylitol-separation task of interest in a continuous mode while maintaining the best performances. It was found first that the use of an ion-exchange resin of styrene–divinylbenzene copolymer in lanthanum form at 60 °C was most suitable as the adsorbent conditions of the xylitol-separation SMB. Under such adsorbent conditions, the intrinsic parameters of the polyol mixture components were determined and then applied to the optimization of the xylitol-separation SMB with a standard type of configuration (2–2–2–2), which was carried out based on the standing wave design method. It was confirmed that the optimized process was successful in keeping the front and rear of each solute band within their corresponding zones under the maximized degree of adsorbent utilization, which suggested that the yield of xylitol and the removal rates of non-products could be maintained at sufficiently high levels while maximizing the SMB throughput. Further comprehensive optimizations revealed that compared to the standard configuration-based SMB, the 5–2–7–2 configuration-based SMB can more than double the xylitol product concentration as well as almost halve the desorbent usage, while maintaining the same throughput and separation capability.