Synthesis of resorcinol from meta-phenylenediamine in the presence of zeolites

Abstract

Resorcinol can be produced in high yields starting from meta-phenylenediamine (MPDA) in the presence of homogeneous mineral acids. The synthesis in the presence of alumino-silicates (e.g., zeolites) offers a solution to the extremely corrosive properties of the mineral acids at reaction temperature (200–275°C). Environmental hazards associated with mineral acids will thus be eliminated. From studies using mineral acids, it was deduced that the rate of reaction is directly proportional to the hydronium ion concentration. The ionisation constants and thus hygroscopic property of the mineral acid determines the degree of resorcinol and MPDA polymerisation. As an alternative, the synthesis can be performed in the presence of alumino-silicates, albeit at higher temperatures. Zeolites H-USY, H-Beta, and amorphous silica-alumina gave good resorcinol yields. During the reaction, the crystal structure of zeolites H-Beta and H-USY is destroyed. H-ZSM-5 is stable under reaction conditions, but the resorcinol yield is rather poor. This can be ascribed to the low adsorption capacity for MPDA in comparison to zeolites H-USY and H-Beta. For all zeolites the dominant part of the reaction may occur on the external surface acid sites.