微反应器内细胞催化丙烯腈水合反应的应用基础研究

Polyacrylamide as flocculant and displacement agent of excellent performance is widely used in the petroleum industry, paper industry, metallurgical industry, sewage treatment and other fields. Acrylamide is mainly produced by bio-catalytic hydration of acrylonitrile in industry. The biocatalytic hydration system of acrylonitrile is a liquid-liquid-cell system. The progress of reaction is mainly influenced by such factors as the dispersion and mass transfer of the acrylonitrile droplets, the double inhibitory effect on cells and the lipophilic adsorption of cells. The project aims to use the micro-reactor to strengthen the mass transfer, heat transfer, process safety and controllable advantages to solve the problems, namely, low production efficiency, high energy consumption and low cell utilization, in the existing traditional process, and develop a new process for the preparation of acrylamide by hydration of acrylonitrile catalyzed by free cells (R. ruber TH3) in micro-reactor. The new process in the micro-reactor has been preliminarily verified feasible. In order to realize the industrial application of micro-chemical system in the bio-catalytic hydration of acrylonitrile, the key scientific issues that need to be addressed in this project are: (1) Using micro-channels to visually investigate the law of dispersion and mass transfer in the liquid - liquid - cell system; (2) Establishment of hydration reaction kinetics model for the liquid - liquid - cell system based on micro-reactor; (3) Application and optimization of membrane dispersion micro-reactor in free cell catalytic process.

聚丙烯酰胺（PAM）作为一种优良的絮凝剂、驱油剂广泛应用于石油工业、造纸工业、冶金工业及污水处理等领域，其单体丙烯酰胺在工业上主要由丙烯腈进行生物催化水合反应来制备。丙烯腈生物催化水合反应体系为液-液-细胞体系，反应进程主要受到丙烯腈液滴的分散传质、细胞受到的双抑制作用和细胞亲油吸附效应等因素的影响。本项目拟利用微反应器强化传质传热、过程安全可控的优势来解决现存工艺中存在的生产效率低、能耗高、细胞利用率低等问题，提出微反应器内游离细胞（R.ruber TH3型红球菌）催化丙烯腈水合反应制备丙烯酰胺的新工艺，并已初步证明可行性。为了实现微化工系统内丙烯腈生物水合反应的工业化应用，本项目拟解决的关键科学问题是：（1）利用微通道及在线显微观测技术研究液-液-细胞体系的分散传质规律；（2）基于微反应器建立液-液-细胞体系的水合反应动力学模型；（3）膜分散微反应器在细胞催化过程中的应用研究和优化。

该项目以发展丙烯腈生物催化反应新技术为目标，致力于通过微化工技术实现丙烯腈水合反应过程强化，开发了新型微结构设备实现丙烯腈微液滴群的高效生成，建立了微液滴群非稳态传质模型，测量了微尺度下含有抑制作用的反应动力学，揭示了反应体系中的耦合作用和调控机制，为实现丙烯酰胺的绿色高效制备提供了基础。该工作的创新性成果主要有：（1）开发了新型微喷嘴阵列膜结构，微喷嘴阵列膜可有效阻隔液滴在膜表面的铺展，膜通量在较低跨膜压差下达到10^5 L/(m2·h)量级，可在较宽操作范围内实现小尺寸（<40 μm）丙烯腈微液滴群的高效生成；（2）利用膜分散微反应器考察了两相流量和膜分散结构尺寸对丙烯腈微液滴群分散过程的影响，研究了体积传质系数随Re数、两相流量比和丙烯酰胺浓度的变化规律。针对丙烯腈微液滴群在微尺度受限空间内的传质过程，结合数值模拟方法，建立了包含边界限制作用和对流作用的微液滴群非稳态传质Sh数模型；（3）搭建了用于测量丙烯腈生物催化反应动力学的微化工系统，建立了包含产物抑制作用的反应动力学和失活动力学模型。通过数值模拟方法对传质和反应过程进行耦合计算，实现了对微化工系统内相间传质和反应进程的准确预测。发展了制备高浓度丙烯酰胺的微化工新工艺，通过优化操作条件，在600 U/mL的初始酶活条件下，丙烯酰胺浓度在30 min内达到40 wt%，生产效率为3.2×10^-5 g/(min·U)，为工业化应用奠定了基础。