Thermal and catalytic pyrolysis of a mixture of plastics from small waste electrical and electronic equipment (WEEE)

Abstract

Pyrolysis seems a promising route for recycling of heterogeneous, contaminated and additives containing plastics from waste electrical and electronic equipment (WEEE). This study deals with the thermal and catalytic pyrolysis of a synthetic mixture containing real waste plastics, representative of polymers contained in small WEEE. Two zeolite-based catalysts were used at 400°C: HUSY and HZSM-5 with a high silica content, while three different temperatures were adopted for the thermal cracking: 400, 600 and 800°C. The mass balance showed that the oil produced by pyrolysis is always the main product regardless the process conditions selected, with yields ranging from 83% to 93%. A higher yield was obtained when pyrolysis was carried out with HZSM-5 at 400°C and without catalysts, but at 600 and 800°C. Formation of a significant amount of solid residue (about 13%) is observed using HUSY. The oily liquid product of pyrolysis, analysed by GC-MS and GC-FID, as well as by elemental analysis and for energy content, appeared lighter, less viscous and with a higher concentration of monoaromatics under catalytic condition, if compared to the liquid product derived from thermal degradation at the same temperature. HZSM-5 led to the production of a high yield of styrene (17.5%), while HUSY favoured the formation of ethylbenzene (15%). Energy released by combustion of the oil was around 39MJ/kg, thus suggesting the possibility to exploit it as a fuel, if the recovery of chemical compounds could not be realised. Elemental and proximate analysis of char and GC-TCD analysis of the gas were also performed. Finally, it was estimated to what extent these two products, showing a relevant ability to release energy, could fulfil the energy demand requested in pyrolysis.

Characterization of Some Real Mixed Plastics from WEEE: A Focus on Chlorine and Bromine Determination by Different Analytical Methods

“…As expected, the highest amount of Br was present in the slot mix, because these plastics are connected directly to the PCBs, and therefore exposed to combustion risk. Also ABS IT showed a high content of Br, while the ABS used for housing has usually a low content of BFRs [28,35,48]. Then, a big fraction of this ABS came probably from the monitors where high concentrations of BFRs may be present [39].…”

A review on thermal and catalytic pyrolysis of plastic solid waste (PSW)

“…Other feedstock materials have also been used in thermal pyrolysis to produce large amounts of products from either virgin or waste plastics (Table 4). Santella et al (2016) pyrolysed recovered waste from electrical and electronics equipment (WEEE) consisting of 64 wt% (ABS), 33 wt% (HIPS) and 3 wt% (polybutylene terephtalate, PBT) between 400 to 800 o C. Energy released by combustion of the pyrolysis oil was around 39 MJ kg -1 , thus suggesting the possibility to exploit it as a fuel. In reality, it is very difficult to estimate the yields of the products from pyrolysis in industrial scale units as the proportion of different plastic types constituting the PSW will vary (Lopez, 2010).…”

“…Williams and Brindle (2002;2003a;2003b) have also reported benzene-toluene-xylenes (BTX) production during pyrolysis of tyres in the presence of Yzeolite. Santella et al (2016) used two zeolite-based catalysts with high silica content to pyrolyse scrap from WEEE. The mass balance showed that the oil produced by pyrolysis is always the main product with yields ranging from 83% to 93%.…”

Thermal behavior and pyrolytic degradation kinetics of polymeric mixtures from waste packaging plastics

“…For these reasons and in order to preserve non-renewable fossil resources, it becomes very urgent to find alternative feedstocks or fuels. Pyrolysis is considered a well-proven technology to material and energy recovery from polymeric waste [8][9][10]. The material is heated at moderate temperatures (300-800°C) under inert atmosphere.…”