Research On Solid-base Catalysts For Synthesis Isophorone

Catalyst precursors were prepared by single-drop coprecipitation method, and the composite oxides were derived from calcination of the precursors. The characterization of catalyst precursors and their derivatives were carried out by means of SEM, XRD, N2 adsorption– desorption and Hammett indicators methods. The results showed that there were not obvious layer structures for the catalyst precursors and their derivatives,aged at 60°C for 0 hours. It was found that the surfaces of catalyst precursors were significantly clustered with increasing aged time. The total surface basic sites of catalyst from precursors prepared at 60°C for 12 hours, was 0.194mmol H+·g?1. The ratio of weak basic sites was 75.77% in the rang of 3.3≤H?≤5.0, and the ratio of medium-strength basic sites H?≥5.0 was 24.23%. The total surface basic sites of Mg-Al-La composite oxides was 0.329 mmol H+·g?1, but mainly in weak basic sites in the rang of 3.3≤H?≤5.0( 87.24% ), and the ratio of medium-strength basic sites H?≥5.0 was only 12.76%.The catalytic performance of catalysts was evaluated by gas phase condensation of acetone to isophorone in a micro-reactor. The optimized preparation conditions of catalyst with Mg/Al=3 was aged for 12 hours at a constant temperature 60°C and calcined for 4 hours at 500°C. The catalyst activity reached 29.20%, isophorone selectivity reached 63.97%, the total selective was 82.67%, and the total yield was 23.99% with 1.0 h-1 at 250°C. It was found that the catalyst showed fairly good stability after 501 hours lab test. The results indicated that the total surface basic sites was in favor of increasing catalytic activity, while the higher ratio of medium-strength basic sites was good for improving the selectivity of isophorone. The catalyst of Mg-Al-La composite oxide increased the catalytic activity, but it is bad for improving the selectivity of isophorone.The molding technology of catalyst was studied. The results showed that water content of catalyst precursor directly effected the forming and strength of catalyst. When dehydration rate was 35%, the hightest intensity was 198.41 N?cm-1. There were similar activity results of molding catalyst compared with unmolding catalyst.