Preparation of zeolite sheet using a papermaking technique - Part II - The strength of zeolite sheet and its hygroscopic characteristics

Zeolite has been widely applied to practical processes in various industrial fields as a desiccant, an adsorbent, a molecular sieve, an ion exchanger, a catalyst and so on. It has generally been used in the form of beads or pellets. However, these methods of utilization have some disadvantages such as powdering of the zeolite when particles rub against each other and remarkable pressure losses in reaction towers with increasing gas flow velocities. Zeolite sheets consisting of 10% cotton linters pulp, about 30% ceramic fiber and 60% zeolite were easily prepared using a papermaking technique intending to produce their honeycomb structure. The sheets were ignited at 700 degreesC to remove linters pulp, but they were fragile and brittle. To improve the zeolite sheet strength, alumina sol was used as a binder. Although a very high retention of alumina was achieved by the internal addition method with polymer retention aids, the improvement of sheet strength was not satisfactory. In this case, the added alumina seemed to be located mainly on the outermost surface of the sheet because the retention of alumina occurred through the filtration. On the other hand, soaking of zeolite sheets in the alumina sol increased the sheet strength remarkably. These results suggested that the alumina was distributed in the whole sheet and formed a tight network structure between particles. These procedures are expected to lead to useful zeolite products, which have a potential for new practical uses. (C) 2001 Kluwer Academic Publishers.