(118f) The Oxidative Steam Reforming (OSR) Performance of Pt-Ni/Al2O3 System with Mixed Propane-Methane Feed

Combined fuel processor-fuel cell (FP-PEMFC) systems are estimated to be well proliferated as energy production units in decentralized applications. Hydrogen production from various hydrocarbons via fuel processing needs a complicated system having up to five serially connected reactor units in which three catalytic reactions occur. The reactions, namely reforming, water gas shift and preferential oxidation, have their own difficulties arising from either thermodynamic limitations, reaction conditions and/or the FP product specifications imposed by the PEMFC. The energy efficiency of the overall FP-PEMFC system is one of the key parameters to be maximized; energy efficiency becomes even more important considering the fact that there may be economical/availability considerations that may impose the use of various hydrocarbon fuels as the FP feed. Our previous experimental studies with propane and LPG feeds[1, 2, 3] showed that OSR should be preferred as the reforming reaction; when the Pt-Ni bimetallic system is used as the catalyst, the high activity/selectivity characteristics are obtained at relatively low reaction temperatures due to the energy efficiency of the catalyst. The energy efficiency/exergy analysis of the FP-FC system has been also performed on a model by our group where experimental results obtained from the OSR, WGS and PROX catalysts under realistic conditions were used. In the system configuration, the rejected stream from the PEMFC is fully fed to a burner and then is used in vaporization of the water stream fed to the OSR unit before the burner effluent is emitted to the atmosphere.  The results of the analysis showed that high temperature level and unused CH₄ content of the exhaust stream of the FP-FC combined system decreases the energy efficiency drastically when there is no partial-recycle to the OSR unit.

The aim of the current work is to analyze the performance of the 0.2 wt% Pt- 10 wt% Ni/Al₂O₃ system in propane OSR reaction when the hydrocarbon feed has various levels, between 5-20%, of methane. The effects of temperature, steam to carbon and carbon to oxygen ratios of the feed as well as the effect of residence time on the catalyst performance have been studied in an experimentally designed fashion.  The experimental results showed that adding methane to the propane feed led to an enhancement in the hydrogen yield without significantly changing the H₂/CH₄ ratio at the OSR exit.  

References:

[1] B. S. Çağlayan, A. K. Avcı, Z. I. Önsan and A. E. Aksoylu; Appl. Catal. A 280 (2005) pg. 181

[2]  B. S. Çağlayan, Z. I. Önsan and A. E. Aksoylu; Catal. Lett. 102 (2005) pg. 63

[3] F. Gökaliler, B. A. Göçmen and A. E. Aksoylu, Int. J. Hydr. Ener. 33 (2008) pg 4358