ABSTRACT
The prime objective of the current research work was to understand the role of microwave-assisted pyrolysis for the upgradation of expanded polystyrene (EPS) waste into valuable aromatic hydrocarbons. Ethyl acetate solvent was used to dissolve the EPS to enhance the homogeneous dispersion of EPS with susceptor particles. Biochar obtained from the pyrolysis was used as a susceptor. The design of experiments method was used to understand the role of microwave power (300 W, 450 W, and 600 W) and susceptor quantity (5 g, 10 g, and 15 g) in the pyrolysis process. The pyrolysis was conducted till the temperature reached up to 600 °C, and this temperature was achieved in the time interval of 14-38 min based on the experimental conditions. The obtained average heating rates varied in the range of 15 to 41 °C/min to attain the pyrolysis temperature. The EPS feed was converted into char (~ 2.5 wt.%), oil (51 to 60 wt.%), and gaseous (37 to 47 wt.%) products. The specific microwave energy (J/g) was calculated to know the energy requirement; it increased with an increase in susceptor quantity and microwave power, whereas specific microwave power (W/g) was a function of microwave power and increased from 15 to 30 W/g. The predicted values calculated using the model equations closely matched the actual values showing that the developed model equations via optimization had a good fit. The obtained pyrolysis oil physicochemical properties including viscosity (1 to 1.4 cP), density (990 to 1030 kg/m3), heating value (39 to 42 MJ/kg), and flash point (98 to 101 °C) were thoroughly analyzed. The pyrolysis oil was rich in aromatic hydrocarbons and it was predominantly composed of styrene, cyclopropyl methylbenzene, and alkylbenzene derivates.
ABSTRACT
Sustainable bio-economics can be achieved by the processing of renewable biomass resources. Hence, this review article presents a detailed analysis of the effect of susceptors on microwave-assisted pyrolysis (MAP) of biomass. Biomass is categorized as lignocellulosic and algal biomass based on available sources. Selected seminal works reporting the MAP of pure biomasses are reviewed thoroughly. Focus is given to understanding the role of the susceptor used for pyrolysis on the characteristics of products produced. The goal is to curate the literature and report variation in the product characteristics for the combinations of the biomass and susceptor. The review explores the factors such as the susceptor to feed-stock ratio and its implications on the product compositions. The process parameters including microwave power, reaction temperature, heating rate, feedstock composition, and product formation are discussed in detail. A repository of such information would enable researchers to glance through the closest possible susceptors they should use for a chosen biomass of their interest for better oil yields. Further, a list of potential applications of MAP products of biomasses, along with the susceptor used, are reported. To this end, this review presents the possible opportunities and challenges for tapping valuable carbon resources from the MAP of biomass for sustainable energy needs.
