Process for preparing superficially porous supports for chromatography and catalysts

A process for preparing superficially porous macroparticles comprising

• (a) forming a well mixed slurry of core macroparticles, colloidal inorganic microparticles to coat the macroparticles, and a liquid, said core macroparticles being (1) impervious and stable, (2) regularly shaped and (3) about 5-200 .mu.m in size and said microparticles being substantially uniform in size and shape and having a size of about 4-1000 nm;
• the ratio of the weight of the microparticles to weight of liquid being from about 0.05 to about 0.5 and the ratio of volume of coating microparticles to total volume of coating microparticles and core macroparticles being from about 0.003 to about 0.7;
• (b) atomizing the slurry to form a fine spray using spraying conditions suitable to produce droplets of a size greater than the size of the core macroparticles;
• (c) contacting the spray with a drying medium at a temperature of from about 130.degree. C. to about 400.degree. C. to evaporate the liquid or cooling the spray below the freezing point of the liquid and drying the resulting frozen particles without thawing them;
• and
• (d) heating the resulting dried coated macroparticles at a temperature and for a time sufficient to cause sintering resulting in about 5% to about 30% decrease in surface area of said dried, coated macroparticles.