Microwave-assisted catalytic gasification of mixed plastics and corn stover for low tar, hydrogen-rich syngas production

• Published in: International journal of hydrogen energy 2024-08, Vol.77 (C), p.69-83
• Main Authors: Abedin, Ashraf, Bai, Xinwei, Muley, Pranjali
• Format: Article
• Language: English
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2024.06.176

The challenge for efficient management of post-consumer plastic and biomass waste has grown over the past few decades due to their dramatic increases. In comparison to conventional gasification, microwave-assisted co-gasification of plastics and corn stover offers many benefits, including increased H2 yield and gas components compared to unfavorable char/tar. Nonetheless, for future commercialization of the process and ease of product separation, further reduction of the undesirable tar is necessary, which can be achieved over the catalytic route. In this work, we studied the catalytic effect of magnetite for microwave-assisted co-gasification of corn stover and plastic to make syngas with higher H2 and lower tar selectivity over non-catalytic conditions. A 1:1:1 ratio of plastic-corn stover-magnetite was used to evaluate the reaction parameters such as temperature, space velocity, heating media, and catalytic cycles under gasification conditions. In comparison with the microwave non-catalytic route, a 100% increase in the total H2 yield with 76% higher H2 production efficiency (mmol/kWh) was achieved in the presence of the magnetite catalyst, while reducing the overall tar formation from 9% to 2%. When magnetite was reduced in situ during the reaction, it coupled with microwave and delivered oxygen radicals that cracked down plastic and corn stover intermediates generated from the synergistic effect under microwave heating. Soon after the oxygen transfer process initiated, magnetite reached its final oxidation state consisting of microwave-active Fe and Fe3C phases that continued coupling with microwaves along with the generated graphitic carbon to maintain the heat necessary to further reduce the generated tar and make additional gaseous products, as confirmed by XRD, Raman, and TGA analyses. [Display omitted] •Catalytic co-gasification of waste feedstock was demonstrated using microwave energy for production of clean hydrogen•Catalyst and microwave synergy doubled the H2 production compared to non-catalytic reaction with 76% higher H2 production efficiency (mmol/kWh)•Catalytic gasification reduced the tar yields from 9% from non-catalytic reactions to 2%•Magnetite delivered oxygen radicals that cracked down plastic and corn Stover intermediates•Synergy between microwaves and catalyst + feedstock resulted in H2-rich syngas with reduced tars