Magnesium and zinc complexes of naphthenic acid model compounds

Abstract

Bitumen is a key Canadian petroleum resource making up 33% of the world’s demand. Bitumen contains naphthenic acids, an undesired component, both environmentally and industrially, due to their toxicity and acidity. Many methods have been proposed for lowering the toxic effects of these acids, to reduce their harmful environmental impacts and to increase the value of the bitumen. In this work, esterification and metal coordination, to zinc and magnesium, were chosen to derivatize several model naphthenic acid compounds, in an attempt to reduce toxicity, bitumen viscosity and corrosion to metal infrastructure. The RP-HPLC partition coefficient determination showed that esterification is a better method for reducing the polarity of naphthenic acids compared to metal coordination complexes. This is due to the metal complexes also coordinating to water, which is confirmed by the crystal structure data. This water coordination raises the water affinity and polarity of the metal complexes to a higher level than expected. Both the esterification method and the metal coordination method demonstrate the ability to reduce the polarity of model naphthenic acids.