Pd、Ni催化紫胶改性新工艺及机理研究

【作者】 廖亚龙；

【导师】 彭金辉；

【作者基本信息】 昆明理工大学 ， 冶金物理化学， 2007， 博士

【摘要】 本论文对Pd、Ni催化漂白改性紫胶脱氯、超声波催化皂化紫胶改性提取紫胶桐酸以及电催化氧化法处理紫胶改性产生高盐含量难生化有机废水的工艺和机理进行了研究。通过催化加氢和消除反应两种工艺,对漂白改性后紫胶进行脱氯,使成品中氯质量分数从2.0%～3.0%降低至0.16%～0.46%,获得了满足食品及制药业使用的低氯漂白改性紫胶产品。催化加氢工艺中分别研究了Pd/C、Pd/Fe、Ni/Fe三种不同催化剂对脱氯效果的影响,最佳工艺条件下,Pd/C为催化剂时成品中氯质量分数小于0.3%,Pd/Fe为催化剂时成品中氯质量分数为0.46%:Ni/Fe为催化剂时成品中氯质量分数为0.44%。消除法对漂白改性后的紫胶进行消除脱氯后,成品中氯质量分数在0.3%以下。两种工艺所获得的成品氯质量分数皆远低于文献报道的指标0.63%。经催化脱氯后,成品中氯质量分数仅为脱除前的1/8～1/5,消除法工艺仅为脱氯前的1/10～1/8,皆远低于1/3这一文献报道指标。通过对催化加氢及消除脱氯反应动力学研究,借助红外光谱、有机元素分析、紫外光谱等手段对反应生成物结构的分析,研究催化加氢及消除脱氯反应的机理。催化加氢脱氯反应为一级反应:消除脱氯反应在80～90℃时也为一级反应,消除反应的表观活化能为38.24kJ·mol^-1。通过因素分析法对消除反应过程中影响成品氯质量分数的因素——反应时间（t）、反应温度（T）、脱氯剂加入量（Q）及初始氯质量分数（C_o）进行多因素线性回归分析,建立了氯质量分数的数学模型:C=3.0814-0.0047t-0.0223T-0.4228Q+0.1336C₀,模型计算结果同实验结果吻合性好。研究了超声波催化皂化改性紫胶分离紫胶桐酸的工艺及机理,并同常温皂化、无水亚硫酸钠加温皂化工艺进行比较。结果表明:三种提取工艺中皆不使用有机溶剂,在盐析产物溶解过程中加入活性炭实现浸出和脱色一步完成,不经过精制而直接获得紫胶桐酸质量分数大于98.0%的成品;加入紫胶量5%无水亚硫酸钠,料液比为1:6,以质量分数25%的NaOH常温皂化7d,产品质量分数可达98.55%～99.53%、收率可达28.09%～29.14%:加入紫胶量10%无水亚硫酸钠,料液比为1:6,以质量分数25%的NaOH在80℃下皂化96h,紫胶桐酸质量分数为98.85%～99.43%,收率为24.64%～25.16%:而引入超声辐射催化皂化过程,在75℃、250W超声功率下皂化10min,所得紫胶桐酸质量分数为98.50%～99.63%,收率大于24.0%;研究了电催化氧化法和Fenton试剂联合微电池法对改性过程中产生的高盐质量浓度、难生化降解有机废水处理工艺。在电催化氧化工艺中,在电极间加入废铸铁屑作为催化剂和电氧化过程中加入双氧水,从而形成一个多元催化氧化体系对废水进行处理。在废水中加入含10%铜屑的废铁屑和双氧水,形成Fenton试剂联合微电池法工艺处理废水。结果表明:以石墨为阳极,不锈钢为阴极,电解20h时COD去除率可达95.1%～96.4%,废水中COD由2200mg/L降至80～110mg/L:而以石墨为阳极,石墨为阴极,在电极间施加13.5V的槽电压,铁屑加入量为3.75g/L,双氧水加入量为2.0mL/L,电解16h时COD去除率可达96.9%～97.8%,废水中COD由2200mg/L降至50～70mg/L;采用Fenton试剂联合微电池法处理工艺,双金属加入量2.5g/L、H₂O₂加入量10g/L,于55℃反应24h,COD去除率可达90.7%,出水COD由进水时的2200mg/L降到200～300mg/L。更多还原

【Abstract】 Three domains correlated with the process and the mechanism involved into seedlac,a natural high molecule polymer,were carried out in this thesis Firstly,the catalytic hydrodechlorination added with Pd and Ni for removal compact chlorine entered into the molecule structure of seedlac while bleached with sodium hypochlorite was investigated.Moreover,the catalytic technology with ultrosound that aleuritic acid extracted from seedlac by saponification was also investigated in this study.Finally,waste water resulted from the modification and sopanification process had been treated with an effective measure originated in this thesis which was nominated as catalytic electrooxidation.Two novel methods of dechlorination process were investigated in the thesis for making it possible to manufacture the shellac with lower chlorine content and to meet the qualification the shellac could be used in food industry and pharmarceutical domains.One was hydrodechlorination catalysed by Pd/Fe,Pd/C,and Pd/C in the presence of hydrogen.And the other was elimination.The experimental results demonstrated that the final products with chlorine content as much as 0.46%,0.44%and 0.3%were obtained when Ni/Fe,Pd/Fe and Pd/C were used as catalyst respectively through the former,and that the chlorine content in the final product was also less than 0.3%when the later was applied.On the other hand,the chlorine content in the final product of defferent process mentioned above was only one fifth to one eighth and one eighth to one tenth respectively in proportioned with that before treated.However,it was higher than one third claimed in literary.Besides,the factors influencing the dechlorination in processes had been studied,as well as the mechanism of dechlorination by dynamics reaction calculation and by the structure characterisation by use of FT-IR, Organatic Elementary Analyser,Ultraviolet visible spectroscopy meter etc. The results drew up in the thesis indicated that the catalytic hydrodechlorination raction was first order reaction,and that so did to the elimination dechlorination raction.Moreover,the apprarent activation engery of elimination dechlorination at the temperatue between 80℃and 90℃was 38.24kJ·mo1^-1which was deducted from the experiment data. Furthermore,through modeled and calculated the relation of chlorine content C of final products with the influence factors such as initial chlorine content C₀,reaction time t,reaction temperature T and quantity of dechlorination reagent Q in the dechlorination process a equation was got: C = 3.0814 - 0.0047t - 0.0223T - 0.4228Q + 0.1336C₀.Inaddition,the process and mechanism of aleuritic acid extracion from seedlac by saponification catalyzed with ultrasound wave were investigated in the thesis.Compared with ultrasonic reaction,other two approaches of saponification were also carried out.One was regular method at room temperature,and the other was enhancing way protected by anhydrous sodium sulfite at a temperature higher than ambient temperature.As a result, the experiments indicated that none organic solvent was used in each process,and fine products can be directly got without any refinery process, and that products with content as much as above 98.0%could be obtained in each process.The experimental results of each process were routed as follows.Firstly,the final products with aleuritic acid content in the range of 98.85%to 99.43%could be got,and the yield of aleuritic acid could reach the scale between 24.64%and 25.16%when seedlac was saponified with 25%NaOH under the conditions of temperature 80℃for 96h.Secondly,the final products with aleuritic acid content in the scale between 98.55%and 99.53%could be achieved,and the yield of product was on the scale between 28.09%and 29.14%when the raw material was reacated with 25%NaOH at room temperature for 7d.Finally,the final products with a scale between 98.5%and 99.63%could be got,and its yield could be reached above 24.0%when the goods was treated with 25%NaOH catalysed by ultrosonic wave with a power 250W at 75℃for 10min.Finally,two motivated methods were also investigated in the thesis for treating the waste water produced in the process seedlac was modified.One was named catalytic electrooxidation,which waste iron scrap was used as catalyst,and hydrogen peroxide was used as oxidation agent.It was demonstrated that the removal efficiency of COD could reach 95.1%to 96.4%and COD decreased to the range between 80 mg/L and 110 mg/L from the original much as 2200mg/L when electrolyzed with stainless steel cathod for 20 h,and that the removal efficiency of COD could reach the scale between 96.9%and 97.8%while COD degraded to the scope of 50 mg/L to 70 mg/L from the original much as 2200mg/L while electrolyzed with graphite cathode for 16h.The other one was Fenton reagent combined with micro-battery,which let COD decrease to the range between 200mg/L and 300 mg/L from 2200mg/L with COD removal efficiency 90.7%.更多还原