Pure H2 Production by Decomposition of Methane Over Ni Supported on Hydroxyapatite Catalysts

Thermocatalytic Hydrogen Production Through Decomposition of Methane-A Review

Consumption of fossil fuels, especially in transport and energy-dependent sectors, has led to large greenhouse gas production. Hydrogen is an exciting energy source that can serve our energy purposes and decrease toxic waste production. Decomposition of methane yields hydrogen devoid of COx components, thereby aiding as an eco-friendly approach towards large-scale hydrogen production. This review article is focused on hydrogen production through thermocatalytic methane decomposition (TMD) for hydrogen production. The thermodynamics of this approach has been highlighted. Various methods of hydrogen production from fossil fuels and renewable resources were discussed. Methods including steam methane reforming, partial oxidation of methane, auto thermal reforming, direct biomass gasification, thermal water splitting, methane pyrolysis, aqueous reforming, and coal gasification have been reported in this article. A detailed overview of the different types of catalysts available, the reasons behind their deactivation, and their possible regeneration methods were discussed. Finally, we presented the challenges and future perspectives for hydrogen production via TMD. This review concluded that among all catalysts, nickel, ruthenium and platinum-based catalysts show the highest activity and catalytic efficiency and gave carbon-free hydrogen products during the TMD process. However, their rapid deactivation at high temperatures still needs the attention of the scientific community.

Surface modification processes during methane decomposition on Cu-promoted Ni-ZrO2 catalysts

The surface chemistry of methane on Ni-ZrO2 and bimetallic CuNi-ZrO2 catalysts and the stability of the CuNi alloy under reaction conditions of methane decomposition were investigated by combining reactivity measurements and in situ synchrotron-based near-ambient pressure XPS. Cu was selected as an exemplary promoter for modifying the reactivity of Ni and enhancing the resistance against coke formation. We observed an activation process occurring in methane between 650 and 735 K with the exact temperature depending on the composition which resulted in an irreversible modification of the catalytic performance of the bimetallic catalysts towards a Ni-like behaviour. The sudden increase in catalytic activity could be explained by an increase in the concentration of reduced Ni atoms at the catalyst surface in the active state, likely as a consequence of the interaction with methane. Cu addition to Ni improved the desired resistance against carbon deposition by lowering the amount of coke formed. As a key conclusion, the CuNi alloy shows limited stability under relevant reaction conditions. This system is stable only in a limited range of temperature up to ~700 K in methane. Beyond this temperature, segregation of Ni species causes a fast increase in methane decomposition rate. In view of the applicability of this system, a detailed understanding of the stability and surface composition of the bimetallic phases present and the influence of the Cu promoter on the surface chemistry under relevant reaction conditions are essential.

Nickel-Hydroxyapatite as Biomaterial Catalysts for Hydrogen Production via Glycerol Steam Reforming

Nickel-hydroxyapatite as biomaterial catalysts exhibited high activity and selectivity in glycerol steam reforming. The catalytic steam reforming of glycerol (C3H8O3) for the production of hydrogen is carried out over nickel supported on hydroxyapatite [Ca5(PO4)3(OH)] catalyst at 600 oC with atmospheric pressure and 120 minute time reaction. The catalysts were prepared by mean of wet impregnation method and varied nickel loadings (3, 6, 12 %) on hydroxyapatite. It is found that the 3% wt% Ni/HAP show higher hydrogen production rate over the other nickel loadings on hydroxyapatite, which is correlated with Ni/HAP catalyst surface area measured by BET adsorbtion and morphology of catalysts. Glycerol steam reforming with water-to-glycerol feed ratio 8/1 much more hydrogen production (77-82%) compared feed ratio 4/1. The catalysts were characterised by BET surface area and SEM-EDX techniques.