Owing to the advantages of intrinsic properties of plastics such as low cost and durability, human beings start to manufacture and utilize them in our daily lives. However, plastics cannot be degraded rapidly in the nature. Due to the accumulation in the landfill and less space to pile up year by year, the problem for landfill needs to be emphasized. In order to treat massive amounts of plastic wastes, we have designed two-staged furnace, which is composed of pyrolysis stage for thermal cracking plastic wastes and catalysis stage for growing carbonnanotubes. According to the results, we find that the best quality of carbon nanotubes(CNTs) (ID/IG = 0.64) but low carbon yield (0.16g/g plastic) are achieved with iron oxide/silica catalyst at catalysis temperature of 900˚C. The highest carbon yield (0.25g/g plastic) but low quality of CNTs (ID/IG = 0.84) are attained with iron oxide/gamma alumina catalyst at the same temperature. We will use iron oxide/silica catalyst for the following discussion to further promote its carbon yield which results from the quality of CNTs can meet commercial demand. By changing different catalysis temperature, no matter which kind of plastic we used, we find that the best quality of multi-walled CNTs were fabricated when catalysis temperature is 900˚C. This is because the energy provided cannot make carbon arranged in a regular fashion when catalysis at 800˚C, whereas metal sites agglomerated at 1000˚C, leading to amorphous carbon accumulated on surface of active sites. Additionally, we also used iron powder in hand warmers to synthesize iron nitrate, and valorizing plastic wastes into multi-walled CNTs successfully. We look forward to improving the competitiveness of market for CNTs to achieve the goal of reusing wastes.

plastic wastes, high-valued carbon nanotubes, catalysis