4 and 9 wt the concentration of carbonate ions in the aqueous solution is generally between 2 and 20 wt and preferably between 3 and 8 wt the amount of transition metal ions or borate in the aqueous solution is generally between 3 and 100 ppm and preferably between 4 and 50 ppm a solution that is formed in a process as described in u s pat no 3 946 077 can very advantageously be chosen as the catalyst described above u s pat no 3 946 077 describes how in an alkane oxidation process an organic process stream is treated with an alkali solution to saponify the esters present and to separate the carboxylic acids released through the saponification or otherwise the solution that is formed in this process the saponification lye hereinafter referred to as aliali solution has a composition that now appears to be applicable as a catalyst the main portion of the transition metal ion or boron in the form of boric acid that is used as the catalyst in the alkane oxidation process also ends up in this aqueous alkali solution the alkali solution is usually regarded as a worthless stream from which the organic substances present.