Microwave effect during aging on the porosity and basic properties of hydrotalcites

In this work, we prepared 27 Ni/Mg/Al hydrotalcites by using a laboratory microwave oven and also by conventional method in order to study the microwaves effect on the surface and basic properties of the resulting hydrotalcites depending on the aging temperature (343-453 K) and the aging time (1-480 min). Samples were characterized by XRD, nitrogen physisorption, atomic absorption, CO2-TPD, FT-IR, TGA, SEM and TEM techniques. The use of microwaves not only causes the expected reduction of the crystallization time, but interestingly also induces the appearance of new porosity and higher basicity when higher temperature (453 K) and longer times (from 30 min) were used. Thus, the hydrotalcite aged in an autoclave by microwaves at 453 K for 120 min shows much higher BET area (87.2 m(2)/g) and higher basicity than the other samples. This has been related to the new porosity appeared as a consequence of the dealumination observed which could be due to some local overheating during microwaves irradiation. (c) 2006 Elsevier Inc. All rights reserved.