Reducing potassium content of offretite pref. to below 0.3 per cent

摘要

Prodn. of an offretite contg. less than 0.5 wt.% K , having the X-ray diffraction pattern of offretite, a water adsorption capacity (at 25 deg.C and water vapour pressure 15% of saturation) above 10 wt.% of cyclohexane adsorption capacity (at 20 deg.C and 8000 Pa) above 4% and SiO2/Al2O3 below about 30 molar from an offretite contg. at least 1 wt.% (usually more than 5 wt.%) K and with SiO2/Al2O3 of 4-10 comprises subjecting it at least twice to a sequence comprising (i) heating to 400-900 deg.C for at least 30 min., and (ii) cation-exchanging at least once with NH4 ions by using a 0.1-10 M soln. of an ionizable NH4 salt at 5-150 deg.C for at least 20 mins at V/P (vols. soln. per unit dry wt of solid)=2-100 .