Synthesis of quinazoline-2,4(1H,3H)-dione from carbon dioxide and 2-aminobenzonitrile using mesoporous smectites incorporating alkali hydroxide

Abstract

A series of magnesium containing mesoporous smectites has been prepared with and without incorporation of alkali hydroxide (NaOH, KOH or LiOH) and employed for the reaction of CO₂ with aminobenzonitrile to produce quinazoline-2,4(1H,3H)-dione. The effects of the quantity and kind of the incorporated alkali atoms on the catalytic properties of the smectites were investigated. Characterization of the smectites has shown that the incorporation of alkali atoms reduces their surface area and total pore volume but enhances the amount and strength of their basic sites. The product yield increases with the amount of alkali atoms incorporated. The incorporation of Li was less effective than that of Na and K for the enhancement of the yield. It has been suggested that weak and/or moderate base sites are responsible for the reaction. The active sites should be alkali hydroxide particles existing between the smectite layers for the alkali incorporated smectites, while for the un-incorporated smectite, the active sites should be the Mg atoms and/or the neighboring O atoms. The Na incorporated smectite was deactivated by repeated catalyst recycling, while such deactivation was not observed with the un-incorporated smectite. The reason for the deactivation was discussed in connection with the structures of the active sites and the actions of the reaction intermediate.