Manufacture of mesoporous alumina of boehmite type via subcritical drying and application to purify liquid crystal

Mesoporous alumina is prepared by using the sodium aluminate as the starting material in this study. The pore diameter of mesoporous alumina is controlled between 2 and 20 nm. The factors of pH value, ageing, water washing and drying conditions on synthesising mesoporous alumina have been discussed. We found that more amount of product can be obtained when the pH of sol is controlled around 7 in the neutralisation process. Ageing temperature of 90 °C and ageing time of 3 h is sufficient to form mesoporous alumina in this process. The mesoporous alumina product with specific surface area of 367m2/g and pore volume of 0.98cm3/g can be obtained. Besides, when subcritical drying of 250 °C and 6.2 MPa is applied to obtained boehmite type mesoporous alumina, larger pore volume of 1.42cm3/g is observed comparing with 0.55cm3/g pore volume of the comparison sample drying under normal pressure. Further, 89.5% sodium release of sample can be reduced by water washing process. The synthesised mesoporous alumina product has been applied to liquid crystal purification test. The superior purification efficiency is found to raise the specific resistance of liquid crystal from 1.8×10121.8×1012 to 2.9×1013Ωcm.