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

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 al^er 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 59 wt.% 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.

Thermal and catalytic pyrolysis of a synthetic mixture representative of packaging plastics residue

A synthetic mixture of real waste packaging plastics representative of the residue from a material recovery facility(plasmix)was submitted to thermal and catalytic pyrolysis.Preliminary thermogravimetry experiments coupled with Fourier transform infrared spectroscopy were performed to evaluate the effects of the catalysts on the polymers’degradation temperatures and to determine the main compounds produced during pyrolysis.The thermal and catalytic experiments were conducted at 370℃,450℃ and 650℃ using a bench scale reactor.The oil,gas,and char yields were analyzed and the compositions of the reaction products were compared.The primary aim of this study was to understand the effects of zeolitic hydrogen ultra stable zeolite Y(HUSY)and hydrogen zeolite socony mobil-5(HZSM5)catalysts with high silica content on the pyrolysis process and the products’quality.Thermogravimetry showed that HUSY significantly reduces the degradation temperature of all the polymers—particularly the polyolefines.HZSM5 had a significant effect on the degradation of polyethylene due to its smaller pore size.Mass balance showed that oil is always the main product of pyrolysis,regardless of the process conditions.However,all pyrolysis runs performed at 370℃ were incomplete.The use of either zeolites resulted in a decrease in the heavy oil fraction and the prevention of wax formation.HUSY has the best performance in terms of the total monoaromatic yield(29 wt-%at 450℃),while HZSM5 promoted the production of gases(41 wt-%at 650℃).Plasmix is a potential input material for pyrolysis that is positively affected by the presence of the two tested zeolites.A more effective separation of polyethylene terephthalate during the selection process could lead to higher quality pyrolysis products.