Phthalide prodn. by hydrogenolysis of 3-chloro:phthalide - with recycle of excess hydrogen after mixing with oxygen and passing over catalyst

摘要

The parent patents describe prodn. of phthalide (I) by hydrogenolysis of 3-chlorophthalide (II). In this addition the unreacted H2 is mixed with 0.05-4 vol.% O2, passed over a catalyst (esp. finely-divided Cu) at 30-200 degrees C then recycled to the reactor. The recycle gas is pref. dried with KOH before return to the reactor and opt. is additionally passed over another catalyst bed at 80-200 degrees C. In the parent patent, direct recycle of excess H2 causes a redn. in hydrogenolysis rate. This is avoided by the present method and the rate remains at its initial value.