Investigations on polyethylene degradation into fuel oil over tungstophosphoric acid supported on MCM-41 mesoporous silica

The catalytic degradation of polyethylene (PE) was carried out at atmospheric pressure under batch conditions at 420 °C using mesoporous MCM-41 material, tungestophosphoric acid (H₃PW₁₂O₄₀), water and methanol impregnated H₃PW₁₂O₄₀ (HPW) over MCM-41 material, (HPW/MCM-41). It has been found that the pore size of MCM-41 plays an important role in PE degradation. While smaller pore-size promote degradation into lower molecular weight, larger pore-size produce a product distribution similar to that of thermal degradation. However, the larger size was used in this work to support HPW acid. The MCM-41 and HPW acid had negligible effects on PE degradation and did not show any catalytic behavior. However, the water-impregnated HPW/MCM-41 promoted the degradation of PE into lower molecular weight products and showed catalytic cracking roots as evidenced by the liquid product carbon number distribution and the production of large quantities of isobutane in the gaseous products. Isobutane was absent in the thermal degradation and when MCM-41 and HPW acid were used as catalysts. It was concluded from a detailed analysis of gaseous products that the methanol-impregnated HPW/MCM-41 showed a very similar catalytic behavior to the water-impregnated HPW/MCM-41 catalyst. However, the liquid product distribution was similar to the thermal one.