Pyrolysis of WEEE plastics using catalysts produced from fly ash of coal gasification

Abstract

The effect of fly ash derived catalysts on pyrolysis of WEEE plastics was investigated.

A waste stream is recovered as a valuable resource for a new process.

Refused derived catalysts reduce the environmental impact and production costs.

Higher yields of light oil are obtained using fly ash derived catalysts.

Fly ash derived catalysts boost cracking effect and increase monoaromatics content in the oil.

Catalytic pyrolysis of thermoplastics extracted from waste electrical and electronic equipment (WEEE) was investigated using various fly ash-derived catalysts. The catalysts were prepared from fly ash by a simple method that basically includes a mechanical treatment followed by an acid or a basic activation. The synthesized catalysts were characterized using various analytical techniques. The results showed that not treated fly ash (FA) is characterized by good crystallinity, which in turn is lowered by mechanical and chemical treatment (fly ash after mechanical and acid activation, FAMA) and suppressed almost entirely down to let fly ash become completely amorphous (fly ash after mechanical and basic activation FAMB). Simultaneously, the surface area resulted increased. Subsequently, FA, FAMB and FAMA were used in the pyrolysis of a WEEE plastic sample at 400°C and their performance were compared with thermal pyrolysis at the same temperature. The catalysts principally improve the light oil yield: from 59wt.% with thermal pyrolysis to 83 wt.% using FAMB. The formation of styrene in the oil is also increased: from 243 mg/g with thermal pyrolysis to 453 mg/g using FAMB. As a result, FAMB proved to be the best catalyst, thus producing also the lowest and the highest amount of char and gas, respectively.

Graphical abstract

Keywords

Waste electrical and electronic equipment (WEEE) plastic mixture / Pyrolysis / Catalyst / Fly ash / Oil

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