Liangguang Tang

Nanoporous carbon supported metal particles: their synthesis and characterisation

In the current work, a simplified hard templating approach is used to synthesise metal (Ag, Rh, Ir and Pt) containing structured carbon. The target metals are first introduced into the NaY zeolite template by wetness impregnation. The metals are carried in the super cages of the zeolite and subsequently embedded in the final structures after the steps of carbonisation and the template removal. Scanning electron microscopy images have confirmed that the carbon structures produced by this method retain the morphology of the original template. Transmission electron microscopy reveals the presence of dispersed metal particles in all the carbon structures produced. The metal loadings in these templated structures can reach 35 wt% without significant losses of surface areas and pore volumes. Selected carbon supported metals are tested for their catalytic activity for the methanation of carbon monoxide. The finding suggested that this method is effective in preparing metal nanoparticles for use as catalysts.

Small Scale Hydrogen Production from Metal-Metal Oxide Redox Cycles

The industrial production of hydrogen by reforming natural gas is well established. However, this process is energy intensive and process economics are adversely affected as scale is decreased. There are many situations where a smaller supply of hydrogen, sometimes in remote locations, is required. To this end, the steam-iron process, an originally coal-based process, has been re-considered as an alternative. Many recent investigations have shown that hydrogen (H2) can be produced when methane (CH4) is used as the feedstock under carefully controlled process conditions. The chemistry driving this chemical looping (CL) process involves the reduction of metal oxides by methane and the oxidation of lower oxidation state metal oxides with steam. This process utilises oxygen from oxide materials that are able to transfer oxygen and eliminates the need of purified oxygen for combustion. Such a system has the potential advantage of being less energy intensive than reforming processes and of being flexible enough for decentralised hydrogen production from stranded reserves of natural gas. This chapter first reviews the existing hydrogen production technologies then highlights the recent progress made on hydrogen production from small scale CL processes. The development of oxygen carrier materials will also be discussed. Finally, a preliminary economic appraisal of the CL process will be presented.