Understanding of synergy in non-isothermal microwave-assisted in-situ catalytic co-pyrolysis of rice husk and polystyrene waste mixtures

Abstract

Rice husk (RH) and polystyrene (PS) wastes were converted into value-added products using microwave-assisted catalytic co-pyrolysis. The graphite susceptor (10 g) along with KOH catalyst (5 g) was mixed with the feedstock to understand the products and energy consumption. RH promoted the char yield (20-34 wt%) and gaseous yields (16-25 wt%) whereas PS enhanced the oil yield (23-70 wt%). Co-pyrolysis synergy induced an increase in gaseous yields (14-53 wt%) due to excessive cracking. The specific microwave energy consumption dramatically decreased in co-pyrolysis (5-22 kJ/g) compared to pyrolysis (56-102 kJ/g). The pyrolysis index increased (17-445) with the increase in feedstock quantity (5-50 g). The obtained oil was composed of monoaromatics (74%) and polyaromatics (18%). The char was rich in carbon content (79.5 wt%) and the gases were composed of CO (24%), H₂ (12%), and CH₄ (22%).

Keywords: Co-pyrolysis; Microwave; Polystyrene; Rice husk; Synergistic effect.