Contributions of acidic-basic sites on hybridized FER@g-C₃N₄ for liquid-phase decarboxylation of naphthenic acids

The efficient removal method of acidic and corrosive organic naphthenic acids (NAs) in heavy crude oils such as benzoic acid as a model acidic component was investigated for a liquid-phase decarboxylation reaction. A novel hybridized heterogeneous basic graphitic carbon nitride (g-C₃N₄) coated on the acidic ferrierite (H-FER) zeolite (denoted as FER@CN) was newly proposed as one of the efficient heterogeneous hybridized catalysts. The basic g-C₃N₄ selectively promoted the absorption of the acidic NAs by acid-base neutralization reaction, and the acidic H-FER effectively enhanced decarboxylation rate by generating CO₂. The synergy effects of the hybrid FER@CN were maximized at an optimal g-C₃N₄/FER weight ratio of 0.5 by enhancing the number of the moderate strength acidic and total basic sites simultaneously. The promoting effects between acidic and basic sites on the FER@CN were mainly attributed to a higher dispersion of g-C₃N₄ nanoparticles on the H-FER surfaces, which was responsible for a higher decarboxylation activity with larger reduction of total acid number (TAN) with the help of the larger amount of moderate strength acidic and basic sites.