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

Resorcinol can be produced in high yields starting from meta-phenylenediami ne (MPDA) in the presence of homogeneous mineral acids. The synthesis in th e presence of alumino-silicates (e.g., zeolites) offers a solution to the e xtremely corrosive properties of the mineral acids at reaction temperature (200-275 degrees C). Environmental hazards associated with mineral acids wi ll thus be eliminated. From studies using mineral acids, it was deduced tha t the rate of reaction is directly proportional to the hydronium ion concen tration. The ionisation constants and thus hygroscopic property of the mine ral acid determines the degree of resorcinol and MPDA polymerisation. As an alternative, the synthesis can be performed in the presence of alumine-sil icates, albeit at higher temperatures. Zeolites H-USY, H-Beta, and amorphou s silica-alumina gave good resorcinol yields, During the reaction, the crys tal 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 ca n be ascribed to the low adsorption capacity for MPDA in comparison to zeol ites H-USY and H-Beta. For all zeolites the dominant part of the reaction m ay occur on the external surface acid sites. (C) 2000 Elsevier Science B.V. All rights reserved.