固相球磨法制备高效钒系催化剂对HCB催化分解研究

发布时间：2019-01-21 08:26

【摘要】：无意产生的持久性有机污染物(UPOPs)是一类在金属冶炼、废物焚烧等热过程中产生的有毒副产物,其中六氯苯(HCB)排放浓度高且难被降解。催化分解对氯代有机物有较好的降解作用,本文旨在开发对HCB具有高效降解作用的催化剂并研究其对HCB催化分解效率和机理。开发了无溶剂快速制备钒系催化剂的固相球磨法,制备出钒钛催化剂(VTi-BM)。与传统浸渍法制备的钒钛催化剂(VTi-WI)相比,VTi-BM对HCB具有更高的活性和更好的稳定性。在反应温度高于270 oC时,VTi-BM对HCB的去除效率高于60%,且经过10 h以上的连续反应后,催化剂活性没有明显降低。此外,VTi-BM催化分解HCB反应速率较快,HCB的安瓿瓶催化分解反应30 min时降解完全,中间产物有TCBQ、TCCD和DCMA。球磨过程改善了催化剂结构特性,其表面钒氧物种分散性好、有更多表面缺陷、化学吸附氧含量高、氧化还原能力强以及表面强酸位多,从而表现了更高的反应活性。制备出掺杂过渡金属元素改性的钒钛催化剂(VMTi),研究发现,W、Cr和Mo的掺杂提高了催化剂活性;而掺杂Ce、Cu、Mn或Co则降低了VTi-BM的催化活性。掺杂W的钒钛催化剂(VWTi)对HCB的催化活性最高,在300 oC下对HCB的去除效率高于80%,且性能稳定。VWTi对HCB催化分解反应速率最快,安瓿瓶催化分解反应20 min对HCB的去除效率高达90%,中间产物也是TCBQ、TCCD和DCMA,但产量极少。VWTi的比表面积最大、表面有WO3结晶相、含有最高的Oα浓度和较高的表面酸性,可能会使催化剂表面暴露更多的活性位、促进V_2O_5在载体表面的分散性并增加表面Br?nsted酸位、具有更多的表面氧空位和化学吸附氧。为寻找最佳催化剂配方,本文针对活性较高的VTi-BM和VWTi开展了负载量实验,得出最佳钨负载量约为5 at.%,最佳钒负载量为5-7 at.%。
[Abstract]:Unintentionally produced persistent organic pollutant (UPOPs) is a kind of toxic by-products produced in the thermal processes of metal smelting and waste incineration. The HCB emission concentration is high and it is difficult to be degraded. Catalytic decomposition has good degradation effect on chlorinated organic compounds. The purpose of this paper is to develop a catalyst with high efficiency for degradation of HCB and to study its catalytic decomposition efficiency and mechanism for HCB. Vanadium titanium catalyst (VTi-BM) was prepared by solid phase milling method. Compared with the vanadium titanium catalyst (VTi-WI) prepared by traditional impregnation method, VTi-BM has higher activity and better stability to HCB. When the reaction temperature was above 270 oC, the removal efficiency of HCB by VTi-BM was higher than 60%, and the catalytic activity did not decrease after 10 h of continuous reaction. In addition, the rate of VTi-BM catalytic decomposition of HCB was faster, and the catalytic decomposition of HCB ampoule for 30 min was complete, and the intermediate products were TCBQ,TCCD and DCMA.. The structure of the catalyst was improved by ball milling. The vanadium and oxygen species on the surface showed better dispersion, more surface defects, higher chemisorbed oxygen content, stronger redox ability and more strong acid sites on the surface, which showed higher reaction activity. The (VMTi), study of vanadium and titanium catalysts modified by transition metal elements showed that the doping of WnCr and Mo increased the activity of the catalysts, while the doping of Ce,Cu,Mn or Co decreased the catalytic activity of VTi-BM. W doped vanadium titanium catalyst (VWTi) has the highest catalytic activity for HCB, and the removal efficiency of HCB at 300 oC is higher than that of 80%, and its performance is stable. The rate of VWTi catalytic decomposition of HCB is the fastest. The removal efficiency of HCB was as high as 90% in ampoule catalytic decomposition reaction for 20 min. The intermediate products were also TCBQ,TCCD and DCMA, but the yield was very small. The surface area of VWTi was the largest, with WO3 crystalline phase on the surface, the highest O 伪 concentration and high surface acidity. It may expose more active sites on the surface of the catalyst, promote the dispersion of V_2O_5 on the surface of the support, increase the acid site of Br?nsted on the surface, and have more surface oxygen vacancies and chemisorbed oxygen. In order to find the best catalyst formula, the loading amount experiments were carried out for VTi-BM and VWTi with high activity. The results showed that the best tungsten loading amount was about 5 at.%, and the best vanadium loading amount was 5-7 at.%..
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;X592

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