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A catalyst for the reforming of naphthas has been developed which provides an excellent octane-yield relationship and can be operated without regeneration for long periods of time. This development started with the discovery of a catalyst for the isomerization of paraffin and naphthene hydrocarbons which was composed of a hydrogenating component, such as nickel or platinum, deposited on silica-alumina. The early catalyst would promote isomerization at nominal temperatures but was much too active as a cracking agent at temperatures required for aromatic formation. By markedly decreasing the surface area of the silica-alumina component, a reforming catalyst was developed that gives the proper balance and direction for the main reactions of reforming: isomerization, dehydrogenation, and hydrocracking.In the last 15 years of petroleum technology, reforming has moved from an operation of questionable necessity to a must for most refiners. This paper summarizes part of the chemistry of reforming and then shows how the authors have developed a new catalyst for this operation.Reforming a naphtha to a higher octane rating must involve at least one of the following chemical reactions: (a) production of aromatics, (6) production of highly branched paraffins, (c) production of olefins, or (d) lowering the molecular weight of the hydrocarbons in the naphtha.Thermal reforming relies largely on molecular weight reduction to obtain antiknock improvement. It forms some aromatics and olefins, but, in general, it is a brute force method of bringing about chemical transformations and does so at the expense of forming undesirable quantities of gas and high boiling material.The early hydroforming catalysts were a big step forward in directing the chemical reactions of reforming to a desired end-namely, the formation of aromatics. These catalysts, however, were far from perfect. They required frequent regeneration with the attendant high plant investment cost and they fell short in octane number improvement due to a lack of isomerization ability.The ability of a catalyst to promote isomerization plays two roles in reforming: it increases the amount of branched chain paraffins in the product and it converts naphthene hydrocarbons with cyclopentane rings into cyclohexane ring naphthenes which are necessary for the formation of aromatics by dehydrogenation.