Thermal and catalytic pyrolysis of polyvinyl chloride using micro/mesoporous ZSM-35/MCM-41 catalysts

Abstract

Micro/mesoporous catalysts of ZSM-35/MCM-41 type were developed by mechanical synthesis method with the objective to use on the catalytic pyrolysis of PVC. They were characterized by X-ray diffraction (XRD), N2 adsorption/desorption at 77 K. The obtained results of XRD showed at low and high angles that catalysts present two phases of MCM-41 and ZSM-35, respectively. Textural characterization of the synthesized porous solids showed MCM-41 an adsorption isotherm type IV and to ZSM-35 an isotherm type I according to IUPAC. MCM-41 Synthesized MCM-41 presents H1-type hysteresis and ZSM-35 presents H4-type hysteresis. When the ratio of MCM-41 decreases in the micro/mesoporous catalyst, the H1 hysteresis curve (pure MCM-41) tends to approach the H4 curve (pure ZSM-35). The greater the proportion of ZSM-35 in the catalytic composition, the smaller the amount of N2 adsorbed, due to ZSM-35 microporous structure. Pyrolysis tests showed that the thermal and catalytic decomposition of PVC occurs in two complex stages of reaction and that the heating rate, the presence and the composition of the catalyst influence the pyrolysis process. Under the conditions studied, the 75ZSM-35/25MCM-41 catalyst exhibits the larger decrease in the total decomposition temperature of PVC.