Chemical looping hydrogen production using activated carbon and carbon black as multi-function carriers

Abstract

The application of a chemical looping process for methane thermo-catalytic decomposition using activated carbon (AC) as a catalyst has been recognized as an advanced process for continuous high-purity H2 production in the carbon constrained world due to its low CO2 formation. AC is able to provide reasonable kinetics, however, it suffers from fast deactivation. Deep regeneration of spent AC catalyst using steam is able to eliminate catalytic deactivation, and this process sacrifices part of the catalyst. The catalytic performance of AC and carbon black (CB) catalysts exhibit opposite deactivation behavior with time. AC provides a better activity, but it deactivates quickly. Though the catalytic activity of CB is low, its activity not only can be maintained, but also shows an increase during the test. Our approach for AC modification was inspired by analyzing the factors that lead to the different performance. Results indicate that the catalytic performance of AC and CB exhibit opposite deactivation behavior with time, and the deposited carbon on their surfaces are in different shape, orientation, and chemical structure. The outward growing cone-like graphene layers and tubular-shaped nanostructures are key factors that help maintain the catalyst's porosity and activity; and the cause of different deposit carbon may be attributed to the irregular, cross-linking graphene layers of AC and the spherical bent graphene layers of CB.