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

Abstract

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 CO2 (as reaction media) and a Ni/SiO2 (as catalyst). The thermolytic characteristics of FNW were also evaluated under the CO2 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/SiO2 catalyst in each of the N-2 and CO2 conditions improved the reaction kinetics in terms of syngas formation with significant production of H-2 (1,543 and 770 mmol g(-1) ca th(-1)) and CO (11 and 1157 mmol g(-1)cat h(-1)), respectively. However, H2 production rate dropped when the catalyst was deactivated due to (hydro)carbon deposition onto the catalyst surface under N-2 environment. Under CO2 environment, CO2 served as an oxidant during FNW thermolysis with additional CO formation and prolonged lifetime of catalyst (via suppressed deactivation). H-2 production mediated by CO2 increased to >= 1,093 mmol g(-1)cath(-1) during five repeated cycles of FNW pyrolysis, coupling with water-gas shift reaction (WGS: CO + H2O H-2 + CO2). This new approach to H-2 production is demonstrated as a practical measure for producing H-2 while extending catalyst life.