Sepn. of mixts. contg. nitro:benzaldehyde isomers - by contacting with pentasil- and faujasite-type zeolite(s)

摘要

Sepn. of mixts. of isomeric nitrobenzaldehydes (I) comprises: (a) treatment of a mxit. contg. p-(I) in benzene, an alkylbenzene and/or a halobenzene with a pentasil type zeolite at -50 to 200 deg.C and recovering a mxit. enriched in o- and m-(I) as filtrate; and (b) sepn. of o-(I) and m-(I) by treatment of a mxit. of these in a solvent (mixt.) selected from aliphatic hydrocarbons, halohydrocarbons, benzene, halobenzenes, alkylbenzenes, ethers, esters or ketones at -50 to 200 deg.C with a faujasite-type zeolite with a proton content of at least 20 equiv.%, based on all exchangeable cations. Steps (a) and (b) are claimed per se. USE/ADVANTAGE - o-(I) and m-(I) are important in the synthesis of pharmaceuticals (esp. coronary dilators (see DE1670827) dyes, antioxidants and agrochemicals. The process may be carried out continuously or discontinuously and gives very good sepn. of the isomers. It shows very high selectivity for sepn. of p-(I) in step (a) and a high rate of sepn. of the two isomers in step (B). The range of solvents and the temp. range in/at which the process can be carried out is wide