METHOD FOR PRODUCING LITHIUM EXCHANGED AGGLOMERED X AND LSX TYPE ZEOLITHES

摘要

A purge (5) from excess lithium is operated separately from the carrousel effluent. The carrousel outputs are a flow (5) with ratio (e) from the first receiver and a flow (3) with ratio (Eo) at the carrousel outlet, where Eo is the stoichiometric equivalent of lithium exchangeable from the filter and e the excess required to obtain the desired exchange of lithium, preferably greater than 96%. Process for preparing X type zeolites with an atomic ratio of Si/Al less than or equal to 1.5 and preferably between 0.9 and 1.1, with the exchangeable cations being 50 to 99% lithium ions, preferably less than 96%; 4 to 50% trivalent ions and/or divalent ions; and 0 to 15% residual ions. These are agglomerated by a binding agent. The zeolite is placed in contact with a solution (1) containing lithium in at least two or preferably three receivers in series or carrousel. The order is modified in a cyclical manner at given time intervals, with the new solution being transposed each time from the first receiver which contains the zeolite which has been mot changed to lithium to the next receiver. Once the desired rate of exchange of lithium is reached, that receiver is disconnected from the carrousel and cleaned of the lithium solution before being emptied and replaced by a new load of zeolite. The lithium solution is at between 80 and 120 degrees C and preferably between 110 and 120 degrees C or greater than 120 degrees C with the system pressure. The pressure is preferably greater than the vapor pressure of the exchange solution at the considered temperature. The concentration of the solution is between 1 and 10 M, preferably between 3 and 6M. The rate of exchange of potassium in the zeolite before the lithium exchange is less than or equal to 15% of the total of the exchangeable sites, preferably less than or equal to 10%. Before the lithium exchange, the zeolite is converted so the great majority of exchangeable cations are monovalent, preferably sodium or ammonium before or after the zeolite is agglomerated. The LiCl purge is purified by crystallisation. The final effluent containing NaCl + KCl + traces of LiCl is recycled through the last receiver of the carrousel. The zeolite is divided into three fixed beds.