Improved silica-alumina catalyst compositions are methods for preparing
such catalyst compositions are disclosed. The present invention relates to
a method for preparing a highly homogeneous, amorphous silica-alumina
cogel catalyst. Silica-alumina according to the present invention may be
prepared by a variety of methods employing batch and continuous processes
in different combinations. In one embodiment, a batch process, the present
invention provides a method for preparing a highly homogenous
silica-alumina cogel catalyst comprising: vigorously mixing an aqueous
silicate solution with a gradual addition of an aqueous solution of an
acid aluminum salt while maintaining the pH of the solution less than 3.0
and ensuring vigorous and complete mixing of the aluminum salt and
silicate solutions to form an acidified silica sol in the aluminum salt
solution; gradually adding a basic precipitant to the acidified silica
sol/aluminum salt solution while vigorously mixing the solution to raise
the pH of the cogel solution to greater than 3.0, producing a cogel;
continuing the addition of basic precipitant and vigorous mixing of the
cogel solution while maintaining a uniform pH of the cogel solution in the
range of from 5-9 until precipitation of the cogel is complete; washing
the precipitated cogel; and processing the precipitated cogel into a
finished catalyst.
