Hydrogen Production By Steam Reforming of Methane Over Supported Nobel Metal Catalysts

Abstract

There is a tremendous amount of research being pursued in the development of hydrogen production technologies. Currently, the most developed and used technology is the steam reforming of natural gas where Ni-based catalyst employing stable inert oxide supports such as Al2O3, MgO, CaO and MgAl2O3 are commercially used. However, this catalyst has serious problems such as higher coke formation, relatively low activity compared to noble metals, required high reaction temperature (850-900 0C), slippage of methane (>3wt%)and high steam to carbon molar ratio (3-4). To overcome these problems, high active noble metal catalysts are being developed. Published information on the above subject is limited and scanty. Present projects aims to investigate the known systems along with new catalysts. Supported noble metals like Pt and Rh are one of the most active and stable catalysts known through literature for catalyzing the CH4 reforming with steam or CO2. One of the known catalysts for the steam reforming is Pt/CeO2 , developed by Next Tech. Generally, noble metal catalysts are resistance to the carbon formation in steam reforming of methane, relatively high active at low reaction temperature and low steam to carbon ratios, but they are very sensitive to feed impurities like sulphur. In this present work, a series of mono and bi-metallic systems for the steam reforming of methane. Supports like −alumina, noble metal (Pt, Ru) and promoters like Ni are used to prepare the catalysts. Catalysts are prepared by incipient wetness impregnation method. Typical loadings used for noble metal are 0.2 & 0.4 wt% and the promoter Ni is 2 wt% . To achieve high volumetric activity, new strategy adopted to prepare a highly dispersed supported noble metal catalysts were achieved by using chelating agent, i.e. ethylene diamine tetra acetic acid (EDTA). The samples prepared were characterized by N2 physisorption and temperature programmed desorption of ammonia. Catalysts were tested for steam reforming of methane in a fixed bed reactor. Commercial catalyst was crushed to obtain particle size of 400 to 840 microns and 3 grams of fresh sample charged to generate the activity data. The reactions were carried out at a temperature range of 550 to 850 0C, steam to methane ratio of 3, 1 atmospheric pressure and methane space velocity in the range of 21000 to 25000 ml/g-cat.h. Commercial catalyst (57-4Q and 25-4Q from Katalco) showed the methane conversion of 83% at 8500C and hydrogen yield 45 vol% of methane. With the catalysts prepared methane conversion and hydrogen yield was higher, catalyst with 0.4 wt% Pt-Ni/ −Al2O3, showed 92.3% methane conversion at 7000C and 53 vol% of hydrogen. Relative stability of nickel promoted catalyst was very good. Catalyst with 0.4 wt% Ru-Ni/ −Al2O3, showed 87% methane conversion at 7000C and 49 vol% of hydrogen. To summarize, platinum –nickel supported catalysts are exhibiting high activity. Catalyst characterization to understand the better activity of the above is in progress, which would be forward path of this project.