| dc.description.abstract | Two main topics are studied in this research. One is the synthesis of ZSM-5 on ceramic fiber paper. The other is the catalytic pyrolysis of polyethylene.
Both solution and dry gel methods were applied. in the synthesis of ZSM-5 on ceramic fiber paper. Dry gel methods were further divided into direct synthesis, steam method and acidic treatment of ceramic fiber before synthesis. Two step synthesis was applied in order to obtain high coverage of ceramic fiber in solution method. The highest crystallinity and surface area in one step synthesis of dry gel method was obtained at 160℃ for 18-27 hours under hydrothermal condition. However, the ceramic fibers are not completely covered with ZSM-5. The products of the first step synthesis at 160℃ for 9 hours were used for the second step synthesis. Complete coverage of ceramic fibers with ZSM-5 was obtained after heating at 160℃ for 9 hours. The best result is obtained when the gel-coated fibers were heated at 80℃ before synthesis and were steamed at 160℃ for 8 hours in an autoclave. Acid treatment of the ceramic fiber paper provides more nucleation sites. The fibers is completely covered by an uniform layer of well-shaped ZSM-5 crystals after 9 hours heating at 160℃.
Pyrolysis of PE into liquid products is the goal of second part study. Two stages pyrolysis was applied. The first stage was thermal pyrolysis at 530℃ under 34 L/min of nitrogen stream in a fluidized bed reactor. The product of the first stage pyrolysis was transmitted to a secondary stage fixed bed reactor for catalytic pyrolysis. The catalysts for pyrolysis were Y-type zeolite, ZSM-5 (Si/Al=31.6 and 21.6), amorphous silica-alumina, Al-MCM-41, and two kinds of FCC waste catalysts, FCC (light) and FCC (heavy), with different amounts of heavy metals. A hundred percent of liquid products were obtained over FCC (light) at 400℃ and 450℃. Liquid products of 72.2 and 54.3% wt% were obtained over Y-type zeolite at 400℃and 500℃, respectively. At 450℃, liquid products of 60.5 wt% were obtained over FCC(heavy). More gas products were obtained over strongly acidic ZSM-5 and high surface area amorphous silica alumina and Al-MCM-41. Product of C5~C12 increase with reaction temperature. The high yield of aromatic compound over Y type zeolite were obtained. The fraction of liquid products increases with decreasing contact time over Y type zeolite. Finally, the largest amount of coke was formed on Y-type zeolite, and smallest amount of coke was formed ZSM-5 among the catalysts studied. | en_US |