Development of highly-efficient simulated moving bed separation processes for the systems containing 2,3-butanediol

Abstract

Due to high usefulness of 2,3-butanediol (BD) in various industries, there has been a lot of interest in establishing an economically-efficient BD production process based on a biotechnological method. One of the key requirements for maintaining high level of economical efficiency for a BD production process is to secure a highly efficient BD-separation process that can realize high-throughput and low-cost operation (i.e., continuous-mode operation) while keeping high purity and high yield for BD. To address such issue, the elaborate simulated moving bed (SMB) processes for high-purity BD separation with high efficiency were developed in this study on the basis of three new strategies. First, the SMB process for separation of BD and fucose was developed, which could offer the benefit of utilizing the defatted residue of microalgal biomass as a feedstock for BD production. This strategy could enable not only a marked reduction in the cost of securing BD source material, but also the production of high-purity fucose product, which is also known as highly valuable bioproduct. Therefore, the BD-fucose separation SMB developed in this study will be of a great help to an improvement in the economics of both BD-production process and microalgae-based fucose production process. Secondly, the customized SMB process for high-purity separation between BD and acetoin was developed, which has an important meaning due to the fact that BD and acetoin are quite similar in molecular structure (i.e., acetoin is a precursor molecule to BD) and thus the BD-acetoin separation task has been a challenging one to date. For a systematic development of the BD-acetoin separation SMB, its optimal design was pushed forward by following a new approach of the inverse method based on the SMB column-profile data and column model, which was then settled by using the relevant optimization tool based on an up-to-date genetic algorithm. It was confirmed from both computer simulations and SMB experiments that such designed SMB was quite effective in the continuous-mode separation of BD and acetoin with high purities and high yields. Since acetoin is as valuable as BD from the industrial perspective, the aforementioned SMB will be highly useful in making a current BD production process take a step further for enabling ultra-high-purity production of BD and attaining additional advantage of acetoin production. Thirdly, the elaborate SMB process for separation of BD molecule into racemic-BD (r-BD) and meso-BD (m-BD) with high purities and high yields was developed, which was motivated due to the fact that the industrial values of pure r-BD and pure m-BD are much higher than that of BD (i.e., BD-isomer mixture), Regarding this task, it was found first that a hydrophobic and nonionic ploydivinylbenzene polymeric resin was fairly suitable as an adsorbent for the BD-isomer separation. Based on this adsorbent, the intrinsic parameters of BD isomers were estimated, which were then applied to the optimal design of the BD-isomer separation SMB. Such designed SMB was experimentally tested, which confirmed its effectiveness as a detailed and reliable process for separation between r-BD and m-BD with high purities and high yields. To make a further improvement in the economical efficiency of such BD-isomer separation SMB, it was additionally optimized using a standing-wave-design (SWD) method, which could promote a comprehensive SMB optimization. The results of such optimization showed that the SWD-optimized SMB for separation of r-BD and m-BD could lead to high productivity and high economical efficiency as well as high purities and high yields. It is thus expected that all of the results in this study can pave a new way to significantly improve the economic feasibility of a BD production process.