SYNTHESIS OF NAPHTHENIC ACIDS BY LIQUID-PHASE OXIDATION OF NAPHTHENIC CONCENTRATES WITH OXYGEN IN THE PRESENCE OF SALTS AND COMPLEXES OF TRANSITION METALS

Naphthenic acids were synthezised by liquid-phase oxidation of a naphthene-isoparaffin concentrate derived from the diesel fraction of Baku oils in the presence of catalysts based on pentanuclear complexes of Co, Ni, and their mixtures with chromium naphthenate. The crystal surface of the nickel complex was studied using scanning microscopy. Physicochemical properties of the feedstock and naphthenic concentrate were characterized. The yield of naphthenic acids was studied in dependence on the catalyst composition. Oxidation of naphthenic concentrate was conducted for 5 h in a bubble type reactor at 110–150 °C with the air feed of 300 L/h and the concentration of catalyst of 0,08–0,20 wt.% with respect to the feed. It was found that complexes of Co and Ni differ in their effect on the yield and quality of synthetic naphthenic acids (SNA). In the presence of Co complexes, the yield of SNA achieved 27,4 %, while the yield of SNA at the same concentration of Ni complexes was 16 %, which is close to the result obtained with Cr naphthenate (17 %). However, in the presence of Cr naphthenate, the yield of oxy-nafthenic acids (byproduct) is twice higher than their yield in the presence of the complex of Ni. The use of pentanuclear complexes of Ni and Co makes it possible to increase the yield of naphthenic acids (by 6–7 % compared with conventional methods), to reduce the consumption of catalyst, and to increase the acid number of the oxidate.

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