天然产物改性中结合氯的催化氢化离解基础研究

Chlorine combines into the molecular structure of natural products while it is modified, which results in limited application. For revealing the mechanism and controlling regulations of eliminating chlorine compacted into the molecular structure of natural products, this basic research on relieving chlorine added to the shellac double bond structure while it was being bleached would be carried out by means of the method of catalytic hydrogenation dechlorination. First of all catalysts such as Pd/C, Pd/Fe and Ni/Fe with Pd/Ni as active components is prepared. Moreover the structure of the catalyst and its physico-chemical properties not only during the reaction, but the response changes before and after the reaction as well are characterized by lots instruments such as elements analysis, nitrogen adsorption, XRD and XPS, SEM etc., and then the activity of catalysts are evaluated. Moreover the composition of the bleached modification shellac such as Cl, C, H, O, N, and the double bond structure as well as function changes are tested and studied to character and release the mechanism and controlling regular of the process of combined chlorine being eliminated during bleaching shellac modification by means of organic elemental analyzer, infrared, ultraviolet, Raman Spectroscopy, pyrolysis gas chromatography, nuclear magnetic resonance. Furthermore the affects of different construction and chlorine, carbon, hydrogen, oxygen and nitrogen amount on physical and chemical properties of bleached shellac are studied. Last but not the finally the kinetics and thermodynamics of the process are analyzed and the process of catalytic hydrogenatic dechlorination is simulated. As a result the mechanism and theory of dechlorination of natural products with a complex structures and macromolecules are achieved, and they can be found potential and enormous application for manufacturing low chlorine bleached shellac.

天然产物紫胶在漂白改性过程中会产生结合氯，从而限制其应用。通过对漂白改性过程中加成到紫胶分子双键结构中的氯进行催化氢化离解脱出的研究，揭示天然产物中氯的脱出规律。采用元素分析，氮吸附、XRD、XPS、SEM等手段表征催化剂的结构、在反应过程中及反应前后物理化学性质的变化，并对催化剂的活性进行评价。采用有机元素分析仪、红外、紫外、拉曼光谱、热离解气相色谱、 核磁共振等手段表征反应过程漂白紫胶的Cl、C、H、O、N的质量分数、双键结构和功能团变化，研究紫胶漂白改性中结合氯的吸附、转移、脱附等传递机理和控制机制。研究结构和氯、碳、氢、氧、氮的质量分数对漂白紫胶理化性能的影响；对催化氢化脱氯反应过程的动力学及热力学进行分析，建立反应的动力学模型，并用软件模拟和仿真氢化催化脱氯反应的过程。获得结构复杂、分子量大的天然产物中结合氯的脱出机理，研究结果在低氯天然产物制备中有应用前景。

天然产物紫胶在漂白改性中会结合氯，结合氯对产品热聚合时间、双键值等主要理化性能有负面影响，限制了漂白紫胶在食品及制药等行业中的正常使用。本项目研究Pd、Ni为活性成分、活性碳、二氧化硅及三氧化铝为载体的双金属催化剂的制备，开展液相氢化催化及亲核消除工艺脱出漂白改性紫胶中结合氯的基础研究，对多相反应体系中天然产物氯代烃中氯的吸附、反应、转移和脱附等一系列的复杂传质过程和动力学模型研究，揭示复杂结构、大分子的天然产物改性中氯的脱出机理和理论。.结合氯的存在改变了紫胶分子中C、H、O的含量，脱除结合氯后 C、H、O的含量相应增加，产品的理化性能及储存性能得到大幅改善。加入Ni-Pd为活性成分的双金属催化剂，在紫胶漂白后的溶液中通入氢气，可获得氯质量分数为0.44 % 的成品，同催化加氢脱氯前2.54 %相比不到1/5。采用亲核试剂——乙醇钠脱氯时，在70℃、反应40min可以使成品中氯的质量分数从原来的2.6%降低至小于1.0%，在90℃、反应20min可以使成品中氯的质量分数降低至小于1.0%，在90℃、反应90min可以使成品中氯的质量分数降低至0.28%。.催化加氢脱氯过程中，主要发生取代反应，漂白过程中加成到紫胶分子环状萜烯酸上的氯被氢依次取代。亲核试剂脱氯前后产品的酸值和皂化值没有变化，但脱氯后表征不饱和结构的碘值却增大，说明脱氯后环状萜烯酸部分的双键值增加。脱氯处理后可能存在三种不同的结构，氯脱除反应为一级反应，速率常数方程为 ，323.15~363.15 K下反应的活化能为35.73 kJ•mol-1。.天然产物紫胶漂白改性后，最大吸收峰的波长由236nm蓝移至222nm，催化加氢脱氯前后的漂白紫胶产品紫外吸收谱图基本一致。而亲核试剂脱除结合氯后，最大吸收波长恢复到改性前的波长值。紫胶环状萜烯酸部分的双键在漂白过程中，由于氯的加成而消失，漂白紫胶为多氯代烃结构，消除法脱氯制备的低氯漂白紫胶的环状萜烯酸的双键值得到恢复，但结构与紫胶存在一定差异。