Abstract:
The major aim of this study was the construction and testing of a bench-scale reactor system suitable for studying the steam reforming (SR) and auto-thermal reforming (ATR) of methane to produce clean hydrogen with high selectivity. A system consisting of mass flow controllers for gases, HPLC pump for water, an evaporation and gas-mixing section, a downflow micro-reactor housed in a temperature-programmable furnace, a water trap, heated stainless steel connecting lines and two parallel, on-line gas chromatographs for feed and product analysis was designed and constructed. The testing of the bench-scale reactor system was conducted using the bimetallic 0.2wt%Pt-15wt%Ni/-Al2O3 catalyst which was previously developed in our laboratory for steam reforming and oxidative steam reforming of higher hydrocarbons such as propane and n-butane. The catalyst was prepared by the sequential incipient wetness impregnation method and catalytic activity tests were carried out in the micro-reactor system constructed. Effects of temperature (500–600oC), inlet methane concentration (3–7mol%), steam to carbon ratio (S/C = 3–5) on SR conversion of methane were studied to determine optimum conditions, and later, effect of carbon to oxygen ratio (C/O2 = 1.50–2.70) on OSR/ATR conversion of methane was examined under these conditions. Optimum conditions were determined as S/C ratio of 4 giving 60% CH4 conversion at 500oC; reaction temperature of 600oC with 90% CH4 conversion and 135 mol/(gcat-s) H2 production at S/C = 4; inlet CH4 content of 7 mol% producing 65 mol/(gcat-s) H2 at 500oC and S/C = 4 with 55% CH4 conversion; C/O2 ratio of 2.12 giving 75% CH4 conversion and 80 mol/(gcat-s) H2 production at 500oC and S/C ratio of 4. Temperature scanning studies conducted by increasing or decreasing reaction temperature in the 525-575oC range by an increment of 25oC every two hours and returning back to the original temperature indicated the presence of catalyst deactivation..
