Study on Calcination Method for Preventing Removal of Structural Aluminum from β Zeolite

The pyrogenic decomposition of template within zeolite Beta was greatly influenced by growth rate of calcination temperature. Inappropriate calcination methods would cause serious dealuminization from framework ofβzeolite and severe reduction in β zeolite’s crystallinity. Components of tail gas producing from calcination process were analyzed by chromatography. β zeolites calcined with different temperatures and as synthesized β zeolite were characterized by TG-DTG, FTIR, XRD, 29SiNMR and 27AlNMR. Hofmann degradation of organic amine took place chiefly at temperature range from 260℃to 420℃. Then the oxidation of organic amine reacted mainly at temperature higher than 492℃. A stage by stage calcining method was presented by using above research results. Firstly, calcination carried at low temperature stage within range from 110℃to 180℃ could eject water absorbed by β zeolite with air stream from the system, and hydrothermal dealuminization from framework of β zeolite that might occur at latter high temperature stage was able to be avoided. Secondly, one or two constant temperature stages placed at middle temperature range from 260℃ to 420℃ could make Hofmann degradation of organic amine react adequately, and moreover, combustible gas such as ethylene yielded from Hofmann degradation could be removed from the system and decomposition heat could be sent out stage by stage. Finally, a small quantity of residual was burned away at high temperature stage which is higher than 492℃. Temperature inside the pores of β zeolite wouldn’t heighten excessively to destroy framework of β zeolite because heat energy produced from residual combusting was limited. By this method, removal of structural aluminum from β zeolite could be restrained effectively, furthermore, amine free β zeolite was able to be produced with high crystallinity.