Effective bromine mitigation is a critical challenge in the sustainable recycling of electronic waste, where the uncontrolled release of brominated species compromises both environmental safety and product quality. This study unveils a novel synergistic transformation pathway of bromine (Br) during ex situ dual-catalyst pyrolysis of waste electronic circuit boards (WECBs). Experiments were conducted in a continuous auger reactor integrated with a fixed-bed catalytic unit employing a dual (HZSM-5/CaO) catalyst system. By tuning the weight hour space velocity WHSV from 0.6 to 1.0 h–1, the catalytic process not only doubled the gas yield from 2.7 to 6.5 wt % but also selectively suppressed liquid formation from 18.0 to 12.5 wt %, while driving deeper deoxygenation and aromatic hydrocarbon enrichment. At lower WHSV, intensified secondary reactions promoted the generation of lighter aromatics and also accelerated coke deposition, highlighting the need for WHSV optimization. Mechanistic insights reveal that brominated phenols and aromatic hydrocarbons dominate the primary volatile fraction, where Br+radicals undergo dual pathways: recombination with H+and small fragments forming HBr/CH<inf>3</inf>Br, or neutralization by CaO to yield stable CaBr<inf>2</inf>. Importantly, 44 wt % of total bromine was retained in the solid residue as CaBr<inf>2</inf>, drastically lowering bromine content in pyrolysis oils. The dual-catalyst strategy thus enables simultaneous Br-fixation, hydrocarbon upgrading, and catalyst regeneration, drastically reducing bromine in pyrolysis oils. These findings provide a scalable, mechanistically guided route for the valorization of cleaner electronic waste, coupling environmental protection with high-value fuel production

This study investigated an efficient catalyst configuration to enhance the recycling of waste electrical and electronic equipment (WEEE) fractions into aromatic hydrocarbons. Two engineered WEEE fractions, low-grade (LGEW) and medium-grade (MGEW), were used as feedstock in an ex situ catalytic pyrolysis process conducted in a two-stage lab-scale reactor. The first stage involved a batch pyrolyzer, followed by a fixed-bed catalytic reactor. The interaction between catalyst active sites and pyrolysis vapors played a key role in determining the chemical functionality of the surface intermediates. Five catalytic modes were tested: CaO, HZSM-5, Fe/HZSM-5, and a combination of CaO and HZSM-5 in mixed and separate bed configurations, with a catalyst-to-feedstock ratio of 0.15 w/w. The iron-loaded zeolite favored gas production, while CaO effectively converted acids into ketones. The dual-catalyst mixed bed of CaO and HZSM-5 exhibited the best catalytic synergy, enhancing the production of aromatic hydrocarbons and decarbonizing the process. However, metal doping increased catalyst coke formation due to more Lewis acid sites and the production of polycyclic aromatic hydrocarbons. Overall, this study provides a comparative analysis of catalyst activity during the thermochemical conversion of WEEE.

Waste electrical and electronic equipment (WEEE) has become a critical environmental problem. Catalytic pyrolysis is an ideal technique to treat and convert the plastic fraction of WEEE into chemicals and fuels. Unfortunately, research using real WEEE remains relatively limited. Furthermore, the complexity of WEEE complicates the analysis of its pyrolytic kinetics. This study applied the Fraser-Suzuki mathematical deconvolution method to obtain the pseudo reactions of the thermal degradation of two types of WEEE, using four different catalysts (Al2O3, HBeta, HZSM-5, and TiO2) or without a catalyst. The main contributor(s) to each pseudo reaction were identified by comparing them with the pyrolysis results of the pure plastics in WEEE. The nth order model was then applied to estimate the kinetic parameters of the obtained pseudo reactions. In the low-grade electronics pyrolysis, the pseudo-1 reaction using TiO2 as a catalyst achieved the lowest activation energy of 92.10 kJ/mol, while the pseudo-2 reaction using HZSM-5 resulted in the lowest activation energy of 101.35 kJ/mol among the four catalytic cases. For medium-grade electronics, pseudo-3 and pseudo-4 were the main reactions for thermal degradation, with HZSM-5 and TiO2 yielding the lowest pyrolytic activation energies of 75.24 and 226.39 kJ/mol, respectively. This effort will play a crucial role in comprehending the pyrolysis kinetic mechanism of WEEE and propelling this technology toward a brighter future.

Ex situ catalytic pyrolysis of engineered waste electrical and electronic equipment (WEEE) was conducted in a two-stage reactor using HZSM-5 catalyst. The effect of the catalysis temperature and the catalyst-to-feedstock (C/F) ratio on products yield, gas and oil composition, and products characterization were investigated in this study. Results indicated that lower reforming temperature and C/F ratio favored organic fractions production. The highest yield of organic fraction was obtained at a catalysis temperature of 450 °C and at a C/F ratio of 0.15, corresponding to 28.5 and 27.4 wt %, respectively. The highest selectivity toward aromatic hydrocarbons and the lowest TAN value of the organic fraction were obtained at a catalysis temperature of 450 °C and a C/F ratio of 0.2, respectively. Most of the alkali and transition metals and 23 % of Br remained in the solid residue after the catalytic pyrolysis of low-grade electronic waste (LGEW). 

Non-catalytic and catalytic pyrolysis of two waste electrical and electronic equipment (WEEE) fractions, with two different copper contents (low- and medium-grade WEEE named as LGE and MGE, respectively), were performed using micro- and lab-scale pyrolyzers. This research aimed to fundamentally study the feasibility of chemical recycling of the WEEE fractions via pyrolysis process considering molecular interactions at the interfaces of catalyst active sites and WEEE pyrolyzates which significantly influence the chemical functionality of surface intermediates and catalysis by reorganizing the pyrolyzates near catalytic active sites forming reactive surface intermediates. Hence, Al2O3, TiO2, HBeta, HZSM-5 and spent FCC catalysts were used in in-situ micro-scale pyrolysis. Results indicated that HBeta and HZSM-5 zeolites were more suitable than other catalysts for selective production of aromatic hydrocarbons and BTX. High acidity and shape selectivity of zeotype surfaces make them attractive frameworks for catalytic pyrolysis processes aiming for light hydrocarbons like BTX. Meanwhile, the ex-situ pyrolysis of LGE and MGE were carried out using HZSM-5 in micro- and lab-scale pyrolyzers to investigate the effect of pyrolysis configuration on the BTX selectivity. Although the ex-situ pyrolysis resulted in higher formation of BTX from LGE, the in-situ configuration was more efficient to produce BTX from MGE. © 2022 The Author(s)

This study focuses on chemical recycling of plastics from waste electrical and electronic equipment (WEEE), which constitutes a problematic waste fraction due to the presence of brominated flame retardants. An auger reactor has been designed and used for this study. Real WEEE material provided by Stena Technoworld has been pyrolyzed under different temperature conditions. The performance of the reactor as well as other important parameters such as the fate of the bromine have been investigated and evaluated. The main outcome of this investigation is to simulate a continuous process, which can be useful for designing a full-scale industrial process. The mass balance results after performing thermal treatment at 400, 500, and 600 °C, showed a high gas yield (44 %wt) at the temperature of 600 °C, which energy content is enough to self-sustain the auger reactor. At the low temperature of 400 °C the oil production reaches its maximum yield as well as maximum concentration of bromine, corresponding to 0.5 wt% in the oil. Several valuable organic compounds have been detected in the oil composition, which can be used as precursors for feedstock recycling producing new plastics. © 2020 The Authors

The thermal properties of cellulose, hemicellulose and lignin can be utilized to improve the characteristics of pyrolysis liquids. In this study, a concept of stepwise pyrolysis to fractionate the liquid based on the thermal properties of the biomass constituents was investigated. Lignocellulosic biomass was thermally treated in two steps: 200–300 °C followed by 550 °C. Derived liquids were studied for GC/MS analysis, water content, acid concentration and a solvent extraction method. Pyrolytic liquid derived from 550 °C after treatment at lower temperatures have a higher relative composition of phenolic compounds compared to one-step pyrolysis (increased from 58 to 90% of GC/MS peak area). Also, compounds known to promote aging, such as acids and carbonyl compounds, are derived at lower temperatures which may suppress aging in the liquid derived downstream at 550 °C. For liquids derived at 550 °C, the total acid number was reduced from 125 in one-step treatment to 14 in two-step treatment. Overall, no significant difference in the total liquid yield (sum of the liquids derived in separated treatments) nor any variations in their collective composition compared to one-step treatment at 550 °C was observed, i.e. stepwise pyrolysis can be utilized for direct fractionation of pyrolytic vapors.