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	Catalyst Performance Catalyst performance is frequently measured by a variety of ways, including the extent of conversion of hydrocarbon (particularly Methane) into Hydrogen, or the Methane content of the exit gas (Methane Leakage) at given temperature, pressure and gas throughput.  Increased temperature reduces the amount of Methane for otherwise fixed operating conditions.  In actual practice, the Methane concentration in the exit gas from Reforming catalyst is greater than the theoretical minimum at a given temperature so that there is a lower equilibrium temperature where that higher Methane concentration would exist at equilibrium.  This difference in temperature is referred to as the Methane Approach.  Most generally, conversion is equated to this approach to the Methane-Steam reaction equilibrium, or "Methane Approach." The Methane Approach is dependent on gas throughput, Steam/Carbon ratio, operating temperature and pressure and catalyst activity. Catalyst activity, (which decreases over time for all catalysts), can be promoted by several means, including constituents combined with manufacturing techniques, catalyst size and shape.  Catalyst size and shape also establish Reformer gas pressure drop and have direct impact on catalyst strength, which has a major influence on practical useful catalyst life.  For tubular Hydrocarbon Reforming equipment, catalyst activity is a direct influence of catalyst tube metal temperature during the life of a catalyst charge, apart from the separate and distinct influence of plant throughput and inter-related Reformer operating conditions.  In normal service as Reforming catalyst ages, tube metal temperature increases for otherwise fixed operating conditions, chiefly from the net loss of active Nickel surface, primarily from sintering of active metal crystallite size and from the gradual loss of Alkali promoters.  Thus tubular Reforming catalyst performance can chiefly be measured by three variables: Exit Gas Methane Leakage (and resulting Methane Approach) Tube Metal Temperature (gradually increasing to the equipment limitations) Gas Pressure Drop (increasing from catalyst attrition, primarily due to plant cycles) For other Pre-Reformers, Auto-Thermal and Secondary Reformers, Methane Leakage and Gas Pressure Drop over catalyst life would fundamentally define catalyst performance. Greater performance for all Reformer types infers longer life due to strong catalyst with low gas pressure loss and close Methane Approach to equilibrium and the smallest possible changes over time. Pre-Reforming Pre-Reformers have gained some recognition, during the past 5-10 years due to the expansion of older plants.  Primary Reformers have been expanded with re-tubing projects as equipment has aged and worn out.  Primary Reformer tubes must be periodically replaced about every 15 years for a typical plant, whether enlarged or replaced in-kind.  Pre-Reformers offer the option of spending capital on an up-stream Reforming catalyst vessel, which unloads Primary Reforming catalyst duty.   The economics are rather complex, but make good sense for some facilities.  Unfortunately, true process debottlenecking of Primary Reforming doesn't occur when Primary Reforming tubes are not enlarged, since gas pressure losses will remain the same, or increase with higher throughput.
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