Synthesis of resorcinol from meta-phenylenediamine in the presence of zirconium phosphates

Aqueous meta-phenylenediamine was converted to resorcinol and ammonia in th e presence of layered a-zirconium phosphates (alpha -ZrP) and gamma -zircon ium phosphates (gamma -ZrP). The compounds were characterised using TGA-DTA , XRD and adsorption experiments studying the uptake of the relevant organi c compounds from aqueous solution. The reactions were carried out in a batc h autoclave at 225 degreesC and corresponding autogenous pressure. Leaching of phosphate groups, quantitated by UV-VIS, was noticed for alpha -ZrP and alpha -ZrP400 (alpha -ZrP calcined at 400 degreesC) resulting in a slight drop in the solution pH towards 5.5. XRD powder patterns of alpha -ZrP take n after reactions showed a slight structural transformation of alpha -ZrP's toward (NH4)Zr-2(PO4)(3) High resorcinol yields were obtained when using g amma -ZrP without any phosphates leaching into solution (pH = 8.3). The aci d sites on gamma -ZrP, however, were poisoned by the product ammonia. Altho ugh leaching of phosphates into solution occurred when calcining gamma -ZrP at 400 degreesC (pH = 2.8), the high yields in resorcinol attained at the end of the second reaction implies that zirconium phosphates can be used as regenerable, heterogeneous reagents. (C) 2000 Elsevier Science B.V. All ri ghts reserved.