【作者】 吴军；

【导师】 李士雨；

【作者基本信息】 天津大学 ， 化学工程， 2010， 硕士

【摘要】 随着人们生活质量的提高,D-木糖正逐步地取代蔗糖而成为主要的甜味剂,木糖的制备工艺也在不断地得到改进和完善。然而,在木糖制备工业化应用的工艺中,木糖得率较低以及木糖结晶后的母液中具有较高含量的糖分等缺陷仍未得到根本的改善,如何提高木糖得率以及在木糖结晶后母液中有效提取糖分成为了木糖的推广应用的主要问题。其次随着工业结晶的发展,为了考虑运输和储存的方便,市场对木糖产品的颗粒大小以及晶型也提出了较高的要求,针对以上两个主要问题,本论文以棉籽壳为原料提取D-木糖晶体的整个工艺流程为研究对象,重点对木糖结晶收率以及产品粒度分布的控制两方面进行了考察研究。首先,本实验打通了从棉籽壳制备D-木糖晶体的整个工艺流程,探讨了棉籽壳的水解,中和,脱色,浓缩,以及离子交换净化处理中的诸多细节问题,并采用一种较新的结晶方法—溶析结晶法制备出了洁白的D-木糖产品。其次,本文对乙醇溶析结晶法制备木糖晶体的收率影响因素进行了细致的研究,重点考察了温度,木糖母液初始浓度,乙醇加入量,晶种加入量,搅拌速率,结晶时间对结晶收率的影响,并作出了各种因素随收率变化的定量曲线,最后在此基础上采用拟水平均匀设计法U₁8(18¹¹)对结晶收率进行了优化,在木糖母液初始浓度为72.22%,无水乙醇加入浓度为75.95%,当加入晶种为0.6g,其在17℃下反应4小时的条件下,可以得到最优的木糖收率79.85%,远远大于目前工厂里50%的收率。最后,实验又对木糖溶析结晶过程粒度控制方面进行了研究,考察了温度,是否加入晶种,搅拌速率,木糖母液初始浓度等对木糖产品的粒度分布的影响,最终确定了粒度分布与这些因素的定量关系,为指导生产实践提供了借鉴意义。更多还原

【Abstract】 With the development of quality of people’s lives, D-xylose is being a kind of main sweetener by replacing sucrose, and method of preparing xylose is constantly improved and perfected. However, it is not fundamentally improved the defects that the yield of xylose is lower and there is the high xylose residues in the xylose solution in the process of xylose’s industrial applications, as a result, how to improve the xylose yield and extract effectively much xylose from the solution become a major problem. What is more , with the development of industrial crystallization, the market proposed a higher request for particle size and shape of xylose product in order to consider the convenience of transportation and storage. For these two main problems, this pape focused on two aspects of xylose yield and product size distribution as assessed by the entire process of producing xylose from cottonseed hulls.First of all, this paper accomplished and studied the whole process of preparation of D-xylose from the cottonseed hull, discussed many details in the xylose production process,such as cottonseed hull hydrolysis,neutralization,decolorization, concentration and ion exchange and so on, furthermore, a relatively new crystal method - solventing-out crystallization was used to get the white D-xylose product.After that, this paper made a detailed study on some factors affecting the yield of preparing xylose by ethanol solventing-out crystallization,focusing on effects to yield of factors of temperature, initial concentration of xylose solution, the quantity of the ethanol and seeds, stir rate, time, and which were made some quantitative curves with respective ocorresponding yields, based on this basis, the quasi—level uniform design U18 (1811) was used to optimize the yield, the following conclusion was obtained, that is, while the concentration of xylose solution is 72.22% , concentration of ethanol is 75.95%, added seeds 0.6g, and stirring 4 hours at 17℃, the recovery of xylose is 79.85%, which is much higher than 50% of the industrial product.Finally, the experiment made a research on the control of product size distribution in solventing-out crystallization process, and ultimately, some factors that were temperature, whether the addition of crystal seeds, stirring speed, initial concentration of xylose solution and so on was determined the quantitative relationship with product size distribution, which provides a guide to Industrial production.更多还原