Abstract: In view of the experimental results that the main product of naphthenic acid deacidification on Br?nsted acid sites is CO, cyclohexylcarboxylic acid and cyclohexyl-butylcarboxylic acid are used for model compounds to investigate the deacidification mechanism of naphthenic acid. The simulation by DMol3 involves the changes of bond order and charge distribution prior and post to interact with Br?nsted acid sites, according to the relative positions between carboxyl group and cycloalkyl, various deacidification mechanisms were proposed. While carboxyl group connects with the cycloalkyl directly, the ring opening reactions proceed prior to deacidification, CO is produced mainly; in the indirect connection case, the deacidification of naphthenic acid happens directly and CO is the dominant product.

Key words: molecular simulation, Bronsted acid site, bond order, charge distribution, mechanism of decarboxylation, naphthenic acid