ANNOUNCEMENTS
Fossil fuels have long been used as main energy source giving rise to serious environmental problems such as fossil fuel depletion and pollutant emission. Hydrogen economy has emerged as an excellent alternative where hydrogen is produced from sustainable sources. The two most important technologies i.e. conversion of biomass and processing of hydrocarbons are mainly being used for hydrogen production. The biomass conversion gives rise to formation of tars which lowers the overall efficiency of process and clogs the downstream pipelines. A catalyst is therefore needed which can break down tar to useful components. Similarly, hydrocarbon processing requires low cost, efficient and long-lasting catalyst. The most commonly used catalyst for hydrocarbon processing is Ni based although it is prone to carbon deposition and sintering thus lowering the activity and life of catalyst. Hence, for both the processes a catalyst which is cheap, abundant and can give good activity is needed.
Red mud, an aluminium industry waste contains a mixture of Fe, Al, Ti oxides and smaller amounts of Si, Ca and Na oxides; it is therefore a potential catalyst. It has been studied for reactions like hydrogenation, liquefaction, methane combustion and others for which Fe2O3 is an active catalyst. Iron in red mud is mostly present in goethite and hematite form and possess high surface area, resistant to sintering and is available at practically no cost. It has been utilized as a catalyst for the decomposition of methane and butane to produce hydrogen.
Present study utilized red mud and experiments were performed in fixed bed quartz tube reactor for the cracking of toluene, preparation of Ndoped carbon nanotubes and methane decomposition. Red mud showed activity for hydrogen generation and nanocarbon formation. With toluene as hydrocarbon, hydrogen evolution was observed above 700 °C and nano fibers of carbon were prevalent at 800 °C. Carbon content up to 46 % was obtained and samples comprised graphitic carbon, iron and iron carbide. Nitrogen was incorporated in carbon using acetonitrile and pyridine and nitrogen content was more at lower temperature (700 °C). Scanning electron microscopy (SEM), X-Ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA), CHN analysis, Raman analysis, High- Resolution Transmission Electron Microscopy (HR-TEM) were used to study the nature (morphology, thermal stability) of carbon deposited and observed that it varied with the precursor used and preparation conditions. Different pre-treatments were done to enhance the catalytic properties of red mud. Methane cracking with different pre-treated red mud showed highest activity for the sample which had high surface area and was pre-reduced to iron. Kinetic studies confirmed a first order reaction and activation energy was 57.86 kJ/mole. The carbon deposited was in the form of nanospheres and nanotubes based on the red mud used.
