Catalyst design from natural zeolites for the pyrolysis and gasification of scrap rubber tires

Abstract

Pyrolysis and gasification are waste to energy thermal techniques that enhance the breakage of chemical bonds into smaller chains at elevated temperatures. Pyrolytic oil is known to be concentrated with heavy compounds that are difficult to remove for the use of oil in further applications. The objective of this project is to enhance the degradation of scrap tires by designing catalysts from natural zeolites to maximize gas yield at the outlay of the oil yield. In this work, pyrolysis was conducted at a fixed temperature of 580℃ whereas gasification was conducted at three different temperatures of 580, 680 and 780℃ accompanied with ethanol. Nine catalysts, from natural clays were activated with two different methods to form Kaolinite, KM_4, Brown clay, BC_6, Montmorillonite, M_6, M_4_3, Bentonite and BN_4 with inorganic H2SO4 in order to enhance Si-Al ratio and hence catalyst acidity. Acidity of a zeolite enhances its catalytic cracking activity. Catalysts behaviors and activities were analyzed using several characterization techniques; Scanning Electron Microscope (SEM), Energy Dispersive X-ray(EDX), Brunauer-Emmet-Teller (BET) and X-ray Diffraction (XRD). Thermal pyrolysis results indicated that montmorillonite modified with low acid concentration, M_4_3, yielded the highest pyrolytic gas yield at 30 wt.percent. M_4_3 had a Si-Al of 5.61 and a high surface area of 224 m2-g. The acidity, surface area and pore size of the catalyst triggered higher selectivity and large chain decomposition on its surface. Liquid product yields were analyzed with GC-MS and contained alkanes, alkenes, alkynes, olefins and aromatics of them contained benzene, toluene and styrene. As for gasification, the syngas yield increased to 41.1 wt.percent obtained at 780℃ with montmorillonite as a catalyst.