Low pressure carbonylation of benzyl chloride = Die carbonylierung von benzylchlorid bei niedrigen drücken

For carbonylations, metal carbonyls, particularly cobalt and iron carbonyls, are often used as catalysts. These reactions take place under rather drastic reaction conditions, e.g. 200–300 °C and 60–100 MPa. In some patents it is stated that similar reactions using the same catalysts can also be carried out under rather mild reaction conditions, such as 0–100 °C and 0–2.5 MPa. We studied the conversion of benzyl chloride to phenyl acetic methyl ester in a semi-batch reactor in which one of the reactants was slowly added to the reactor. In this way a non-catalysed parallel reaction could be oppressed for the greater part. The highest conversions and selectivities were obtained when a solution of sodium methylate in methanol was slowly added to a reaction mixture containing benzyl chloride. In this way under optimized conditions a conversion of benzyl chloride of 100% has been found. It also appears that the conversion and selectivity decrease not only at low but also at high CO partial pressures. A possible explanation for this phenomenon will be given.