SELECTIVITY PROBLEMS IN THE CATALYTIC DEOXYGENATION OF BENZOIC-ACID

The oxides of Mg, Pb, Cr, La, Pr, Yb, Mn, Fe, Co, Zn, Zr, and Ce were studied as catalysts for the reactions of benzoic acid in the temperat ure range 523-723 K. All experiments were performed in a continuous ho w apparatus, at a total pressure of about one bar, with hydrogen as th e reductant. The oxides studied could be subdivided into several group s according to their product pattern. The groups indicate the prevaili ng mechanism. The two basic mechanisms are: (i) Mars and van Krevelen (selective to benzaldehyde) and (ii) radical-like decomposition of ben zoate. The highest yield of benzaldehyde can be obtained with oxides o f high metal-oxygen bond strength. (C) 1997 Academic Press.