Optimization of conditions for polymer cracking using mordenite catalyst

Abstract

In this study, a highly active dealuminated mordenite catalyst for polymer degradation was developed. The hydrogen mordenite catalysts with required Si/Al ratios were prepared by conventional ion exchange of the sodium mordenite (Si/Al = 11) with ammonium ions from an ammonium chloride solution alternate to the calcination of the exchanged mordenite until 3 cycles completed and finally acid leaching with hydrochloric acid. To obtain catalysts having precisely required Si/Al ratios the conditions for zeolite dealumination by acid leaching were systematically studied. It was found that the Si/Al ratios in catalyst strongly depend on acid concentration, temperatures and duration of acid treatment. The catalysts were characterized using X-ray Diffraction, Aluminum Nuclear Magnetic Resonance, Ammonium Temperature Pregrammed Desorption and Inductively Coupled Plasma-Atomic Emission techniques. Catalysts with five Si/Al ratios (11, 19, 47, 90, and 127) were selected for catalytic activity test. Effects of Si/Al ratios and temperature were studied to obtain the optimal condition for the degradation of polypropylene and polyethylene. It is found that the H-MOR catalysts with Si/Al ratios of 11 – 127 exhibit the very high activity about 100% conversion. The catalyst with the Si/Al ratio of 127 gives the highest selectivity to propylene formation with the least amount of coke and methane. The optimal temperature is 450℃.