Metal-doped high silica ZSM-5 nanocatalyst for efficient conversion of plastic to value-added hydrocarbons

Abstract

In this work, catalytic pyrolysis of plastic was investigated using the high siliceous ZSM-5 nanocatalysts. The parent nanocatalyst with boron promoter in the structure was prepared by hydrothermal technique. The wet impregnation of molybdenum promoter (0–30 wt.%) was then carried out through a multi-step process. XRD, FT-IR, N2 adsorption-desorption, FE-SEM, TEM, TG-DTA, and NH3-TPD techniques were characterized the nanocatalysts. The modified nanocatalyst included the uniform spherical morphology and the homogenous dispersion of Mo species. Mo incorporation improved the concentration and reduced the strength of the acid sites. The NZC25 nanocatalyst had high crystallinity (100%), mesoporous structure (0.08 cm3g−1), and high surface area (259 m2g−1). The effect of different amounts of the promoter and operating conditions were studied on the catalytic activity in dual-zone fixed bed reactor. The NZC25 nanocatalyst had the best activity in catalytic pyrolysis, including high plastic conversion and high liquid product (0.51 g). The optimum operating conditions were 525 °C, catalyst to plastic ratio of 1:10, and N2 flow rate of 50 mL min−1, which resulted in the highest production (94%) of value-added hydrocarbons (C6-12). Furthermore, 99.7% of the produced oil was desirable hydrocarbons, including iso-paraffin (3.2%), aromatics (87.3%), and olefins (9.2%). The nanocatalyst showed low coke content (only 1.62%) and high reusability through the sequence cycles, including less than 10% drop of liquid production. The results showed the great capacity of the high siliceous ZSM-5 in the conversion of plastic to value-added hydrocarbons.