[Regular Paper] Synthesis of ZSM-5 Zeolites from Quang Ninh Coal Ash Components and Activity for Catalytic Cracking of Low-density Polyethylene

Coal of Quang Ninh (QN) province (Vietnam) is high quality and famous worldwide. QN coal ash includes large amounts of Al2O3 and SiO2 which can be utilized for zeolite synthesis. In this study, inorganic components of QN coal ash were assembled to prepare ZSM-5 zeolite under several conditions. The effects of components, which are included in real coal ash but are not needed to prepare zeolite, were investigated on the preparation and the property of zeolite. Synthesis of ZSM-5 using tetrapropylammonium hydroxide (TPAOH) at 150 degrees C for 48 h confirmed that ZSM-5 crystals appeared at SiO2/Al2O3 ratios higher than 52 and developed completely at 78, based on XRD and nitrogen adsorption -desorption measurement. Similar results were observed for ZSM-5 synthesis both without QN coal ash components and with real QN coal ash, indicating that the effects of components other than Si and Al on the preparation of ZSM-5 are quite small. When these catalysts were used for the catalytic cracking of low -density polyethylene (LDPE) using the Curie point pyrolyzer (CPP) method, ZSM-5 prepared using model coal ash components exhibited the same or slightly higher conversion than conventional ZSM5. In contrast, ZSM-5 prepared with real coal ash components exhibited slightly lower conversion, suggesting that some inorganic salts included in real coal ash might affect the activity for catalytic cracking of LDPE.