Functional use of CO2 for environmentally benign production of hydrogen through catalytic pyrolysis of polymeric waste.

• A new sustainable platform for plastic waste/CO 2 to syngas was investigated. • Catalytic pyrolysis promoted conversion of fishing net waste to syngas under CO 2 /N 2. • Coke formation resulted in Ni catalyst deactivation, but CO 2 suppressed it. • Continuous use of Ni catalyst under CO 2 was allowed for high production rate of H 2. A benign route for hydrogen (H 2) production is environmentally desirable. To achieve this, H 2 synthesis from polymeric waste was investigated. A new route was sought to maximize H 2 production with the least formation of coke during catalytic pyrolysis of fishing net waste (FNW) by using CO 2 (as reaction media) and a Ni/SiO 2 (as catalyst). The thermolytic characteristics of FNW were also evaluated under the CO 2 condition (and N 2 as reference environment) both with and without catalysts to assess the full scope of variabilities involved in catalytic pyrolysis of FNW. The use of Ni/SiO 2 catalyst in each of the N 2 and CO 2 conditions improved the reaction kinetics in terms of syngas formation with significant production of H 2 (1,543 and 770 mmol g−1 cat h−1) and CO (11 and 1157 mmol g−1 cat h−1), respectively. However, H 2 production rate dropped when the catalyst was deactivated due to (hydro)carbon deposition onto the catalyst surface under N 2 environment. Under CO 2 environment, CO 2 served as an oxidant during FNW thermolysis with additional CO formation and prolonged lifetime of catalyst (via suppressed deactivation). H 2 production mediated by CO 2 increased to ≥1,093 mmol g−1 cat h−1 during five repeated cycles of FNW pyrolysis, coupling with water–gas shift reaction (WGS: CO + H 2 O ⇌ H 2 + CO 2). This new approach to H 2 production is demonstrated as a practical measure for producing H 2 while extending catalyst life. [ABSTRACT FROM AUTHOR]