Combustion Synthesis of Novel Catalysts for Hydrogen Production from Light Alcohols

Combustion synthesis (CS) has been explored as a novel tool for catalyst synthesis. CS is a simple, fast and economic process for materials synthesis which possesses many advantages over other traditional techniques for catalyst's synthesis such as co-precipitation. Some modifications were introduced to the conventional CS technique in order to prepare fine nano-particles with high surface are to suite the catalytic applications. Time-temperature profile, adiabatic combustion temperature and product surface area were measured with varying the fuel content in the reactive combustion mixture, more specifically the so called Solution Combustion Synthesis (SCS) mixture. A correlation was established between surface area, adiabatic combustion temperature and the amount of fuel in the reactive mixture. Based on thermodynamic calculations the fuel content was adjusted to produce metal oxides, pure metals and alloys. A mechanism for product synthesis was developed on the basis of TGA/DTA results, XRD analysis of the products during CS and thermodynamic calculations. These findings were used to synthesize partially reduced catalyst with high surface area for hydrogen production from alcohols. The reactive mixture of the SCS was impregnated on a thin cellulose paper in order to enhance the heat transfer effects after combustion which would in fine particles with high surface area. This technique is known as Impregnated Layer Combustion Synthesis (ILCS). Temperature distribution across the combustion front was measured using FLIR systems IR camera, and SONY camcorder was used to record the visual changes leading to product development. The evolution of catalyst synthesis and the mechanism of self propagation were explained on the basis of these images, TGA/DTA, XRD results and with some help from other literature results. A model for ILCS process was developed in order to study the effect of different combustion parameters on the physical properties of the catalysts synthesized. Using the abovementioned techniques, Cu, Zn, Zr based catalysts were synthesized to study hydrogen production from partial oxidation of methanol. Addition of small amount of Pd, and impregnation of the Cu/Zn/Zr catalyst on ZrO2 support were also studied. Presence of Pd helps in starting the methanol combustion reaction at an earlier temperature whereas ZrO2 provides structural stability as well as high surface area to increase the active sites participating in the reaction. Ni, Fe and Cu based multicomponant catalysts were synthesized for hydrogen abstraction from ethanol reforming reactions. The molar ratios of these elements were optimized to get high ethanol conversion and hydrogen selectivity for ethanol partial oxidation using a high throughput ten-channel reactor. The most active and hydrogen selective catalyst was further studied along with single phase Ni, Fe and Cu catalysts, using a single flow recycle reactor for ethanol decomposition and partial oxidation reactions where the effluent products were analyzed using gas chromatographs. These catalysts were further characterized using XRD, BET, SEM, XPS, XAFS techniques.