The Development Of The Power Supply For Time-of-flight Mass Spectrometer And The Application Of Photoionization Mass Spectrometry On The Catalytic Pyrolysis Of Polypropylene

Municipal Solid Waste (MSW) management is a great challenge that many countries are facing today. Rapid urbanization, new economic activity, and population growth place severe pressures on solid waste management systems. It is estimated that cities generated approximate 1.3 billion tons of MSW worldwide in 2010, and this is estimated to increase to 2.2 billion tons by 2025. Plastics are one of the most important components in MSW. The huge demand of plastics brings about treatment problems of plastic wastes. According to the data supplied by the World Bank, plastic wastes account for 8-12% of total MSW production all over the world. Various kinds of plastic products are manufactured and take into usages since this material was invented. The chemically stability of general plastics such as PP, PE, ABS etc. is pretty well, which means these plastic wastes are hard to be degraded in environment. The plastic wastes have relatively high economic potential as kinds of petrochemical products. Many researchers have paid great attention on production of refuse-derived fuel and chemical products from plastic wastes. Catalytic pyrolysis is a feasible way to recycle plastic wastes into useful products. The researches in the past mainly focus on the macro pyrolysis behavior and off-line analysis lacking of real-time sampling and online analysis. The characterization of catalyst is the main part of catalytic pyrolysis. Besides the traditional methods such as XRD, FTIR, TPD and NMR, the performance of catalyst in real reactions can be deemed as a character of the catalyst. In present work, firstly, a power sourse system for time of flight mass spectrometer was investigated and manufacturd, the performance of the power source system was pretty well. Then the online vacuum ultraviolet photoionization mass spectrometry was put into use to study the character of HUSY catalyst pretreated at different temperatures and partly posined when used on pyrolysis of polypropylene (PP). The dissertation consists of five chapters.In Chapter 1, we briefly introduced the current situation of fossil fuels and MSW in the world wide. The significance and the purpose of this dissertation are given.In Chapter 2, the design of power source system for time-of-flight mass spectrometer (TOF-MS) was described. A power source system used for TOF-MS integrated with delay generator and bipolar high voltage pulse generators was designed and described in detail. The output of module high voltage power supplies are controlled by specific chips, in order to get a stable voltage output and accurate feedback. The integrated high voltage pulse generators were designed for TOF-MS, the pulse width and frequency were adjustable, the front edges of both positive and negative pulse were less than 10 ns, the jitter of front edges was about 1.1 ns. The delay generators were achieved by the pulse width modulation (PWM) function module in the micro controller unit (MCU), which can get a minimum step of 150 ps. At last, a host program programmed by Lab View was introduced.In Chapter 3, the influence of pretreatment temperature of HUSY was investigated. The HUSY pretreated at different temperatures were charactered by NH3-TPD, XRD and pyridine-FTIR. The results show that the amount of acid sites is decreasing while the pretreatment temperature getting higher. The strcture of HUSY changes as well after the catalyst was calcined at different temperatures. The results of catalytic pyrolysis of PP catalyzed by HUSY calcined at different temperatures are simmilar with the character results. The catalyst calcined at 200 and 800℃ show different performance when catalyzing pyrolysis of PP. Temperature-programmed experiment and total yield of four kinds of products were analyzed.In Chapter 4, HUSY catalysts adsorbed with ammonia at different levels were applied to PP catalytic pyrolysis. The effect of ammonia adsorption on catalyst was discussed in detail. The pyrolysis temperature dependence was analyzed, and we found that the effect is related with the level of ammonia adsorption. The products tendency along with time of pyrolysis were discussed. The results showed that the initial cracking time of PP with catalysts adsorbed with more ammonia delayed a lot.Finally, we summarize the work in this dissertation and make some prospects for the future work, including improvements of the current power sourse system for TOF-MS, researches on different kinds of polymers and mechanism for catalytic pyrolysis of polymers.