Catalytic materials for waste polymers degradation: Design, preparation and characterization

LILIANA B. PIERELLA; MARÍA S. RENZINI; DANIEL S. CAYUELA; OSCAR A. ANUNZIATA

Buenos Aires, Argentina

Workshop; Workshop Recent developments in complex materials: production and characterization; 2005

Catalytic transformation of waste polymers into hydrocarbons with higher commercial value shows a great interest. Various techniques to convert plastic wastes into gaseous, liquid or solid fuels have been proposed. Thermal degradation of polyolefins was studied extensively, but the oils distribution showed a wide distribution of carbon atom numbers. Further, it was found that the oils obtained by catalytic degradation over mainly solid acids were rich in aromatics. In this work, polyolefins as high and low-density polyethylene (HDPE and LDPE), polypropylene (PP), copolymers of ethylene-propylene and polystyrene (PS), were transformed over microporous (ZSM-11 and BEA zeolites) and mesoporous (MCM-41) materials modified with H, Zn, Ga y Mo cations. Using a one-pass reactor and 400-500ºC and atmospheric pressure as operating conditions, the conversion was total.  Zn-zeolites and Zn-MCM-41 showed a higher liquid hydrocarbon yields for all of the polymers employed; mainly aromatic hydrocarbons over Zn-zeolites and light gas oil over Zn-MCM material.  Propane and butane are the principal gaseous products obtained in all the reactions. The synthesized and modified catalysts were characterized by TG-DSC, XRD, FTIR and surface area by BET, in order to confirm the crystallinity of the structures. The acid properties of the materials were evaluated using pyridine as a probe molecule by FTIR analysis, which allowed us to correlate with the catalytic activity. The reactants were characterized by FTIR and thermal analyses (TG-DSC-DTA). Reaction products were analyzed by gas chromatographic and mass spectrometry.  By means of the development of a competitive catalytic system, we determine the feasibility of the process of degradation of plastic remainders towards the synthesis of liquid hydrocarbons.