Type 4A zeolite of high cation exchange rate prepn. - from sodium silicate and aluminate, useful in detergency and as molecular sieve

摘要

The prepn. of type 4A zeolites, of high cation exchange rate, made up of agglomerates of up to 50 mu, of small twined crystals, and with BET surface greater than 1m2/g, is described. A soln. of alkaline silicate and sodium aluminate is held at 75-95, pref. 80-95 degrees C for 2, pref. 4-6 hrs. sodium silicated and aluminate solns. being added simultaneously to the hot medium. The addn. is effectd in such a way as to form a crystalline silico-aluminate, a concn. of crystallised zeolites 20, pref. 10, g/l being maintained. The feed solns. are diluted to give an SiO2 concn. 20 g/l. The silico-aluminates can be used in the usual applications of type 4A molecular sieves, but because of their high cation exchange power are partic. recommended for detergent applications. Their small particle dimensions enables them to be carried away by water.