In the hydrogenation of hydrocarbon fractions, catalysts are used which comprise a hydrogenation component usually on a suitable support such as, for example, silica, alumina, or mixtures thereof. The hydrogenation component is customarily supplied by a transition metal or metals, such as metals from Group VIB, Group VIII and some Group IB metals. Particularly suitable metals include copper, nickel, tungsten, cobalt, and molybdenum. The catalysts are conventionally prepared by impregnation of the support with the solution or dispersion of a decomposable salt of the metal hydrogenation component, followed by calcination in air to convert the salt to metal oxide. The hydrogenation component can be employed as the metal, metal oxide, metal sulfide, or mixtures thereof.
It is frequently desirable to convert the metal to a sulfide when the catalyst is used to process a sulfur-containing feed.
In general, the art teaches that sulfiding or conversion of the metal hydrogenation component to its sulfide form, can be accomplished by contacting the catalyst with hydrogen sulfide or organic sulfur compounds mixed with hydrocarbons at elevated temperatures up to about 1200.degree. F. However, loss in catalyst activity can result if sulfiding is carried out at a high temperature. Consequently, it is customary to employ relatively low temperatures, i.e., in the range of 750.degree. F. or lower, to avoid sintering of the metal components and in order to meet metallurgical limitations of the process equipment. For catalysts which have metals such as nickel incorporated by impregnation, U.S. Pat. No. 3,325,396 and U.S. Pat. No. 3,324,045 teach that sulfiding temperatures should not exceed 750.degree. F.
U.S. Pat. No. 3,519,556 discloses an activation treatment for hydroconversion catalysts to increase hydrocracking activity which comprises sequentially calcining and sulfiding a metal and fluoride-containing hydrogel catalyst at temperatures of at least 930.degree. F. Fluoride-containing catalysts, however, have the drawback that fluoride leaches from the catalyst during use and forms hydrogen fluoride, which is extremely corrosive.