Reduced accumulation of coke on steam reforming catalysts by suppressing production of carbon monoxide

Steam reforming reactors are generally large to accomplish economies of scale. In addition, the typical operation of the shift reactor at a lower temperature than the reforming reactor makes it impractical to combine these two chemical reactions in one reactor. Furthermore, designs currently known do not lend themselves to being scaled down to a smaller size or to making it possible to efficiently control the temperature at various points. It is well known that among the main problems that lead to the reduction of the activity of the nickel-based catalyst on refractory supports, such as alumina, magnesium or calcium aluminates, carbon deposition stands out, which in a generic way can be called coke, especially when processing raw materials with a greater tendency to form coke, such as naphtha or heavy natural gas containing significant amounts of higher molecular weight hydrocarbons or fillers with the presence of olefins. The accumulation of coke on the steam reforming catalyst leads to a reduction in its activity, which can lead to increased hydrogen production costs, reduced production capacity and, in more severe cases, the shutdown of the unit, in order to minimize the risk of reactor failures occurring due to exposure to high temperatures due to low catalyst activity. Direct heating is of considerable advantage as it largely overcomes the problems encountered with reaction rates being limited by the rate of heat transfer through the tube wall especially near the reformer entrance and thus, for a given conversion, the reactor may be smaller, more efficient and less expensive. High steam-to-methanol ratios are required for direct heated reformers. The relatively large amounts of steam passed through the bed continuously clean the catalyst by suppressing production of carbon monoxide and retard catalyst poisoning thereby enhancing catalyst stability.