| In this paper, the Mg-Al LDHs were prepared by double-gob co-precipitation method, Mg-Al composite oxides were derived from the calcination of Mg-Al LDHs. The characterization of Mg-Al LDHs and Mg-Al composite oxides were carried out by use of XRD, FT-IR, TG-DTA, SEM, CO2-TPD and BET techniques. The catalytic activity, selectivity and stability of the Mg-Al composite oxides were investigated for gas phase condensation of acetone to isophorone in a micro flow reactor and a 100mL flow reactor, respectively. The results show that the LDHs prepared by co-precipitation method have significantly the surface structure of"Sand-rose", and the layered structures are retained in Mg-Al composite oxides. Furthermore, the results verify that the Mg-Al composite oxides calcinatied at 500°C for 4h from LDHs prepared at 60°C for 12h, have high specific surface area, and two different basic sites according to CO2-TPD analysis, i. e., 180%～200°C weak ones and 400°C～500°C moderate ones, but more amount of basic sites than the Mg-Al composite oxides prepared at other conditions.The catalytic performance of the Mg-Al composite oxides was determined through the condensation reaction of acetone to isophorone. The experimental results indicate that the Mg-Al composite oxides as catalysts display a high activity and selectivity. Acetone conversion reaches to 17%～20%, isophorone selectivity 64%～65%, total effective selectivity of isophorone plus mesityl oxide 81%-83%, and total effective yield of isophorone plus mesityl oxide 14%～16% at 250°C and 1.0h-1. The catalyst was also prepared in lab scale at the optimized conditions and it shows fairly good stability and service life for 350h run time at a 100mL flow reactor. The regeneration ability of the deactivated Mg-Al composite oxide catalysts was studied, it is discovered that the activity, selectivity and effective yield of the regenerated catalyst were decreased about 5% than the fresh catalyst.
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