GAS-PHASE HYDROGENATION HYDROGENOLYSIS OF ISOPHTHALDEHYDE OVER NI/SIO2

The gas phase hydrogen treatment of methanolic solutions of isophthaldehyde (IPA), in the temperature range 393 K less than or equal to T less than or equal to 653 K, was studied over a Ni/SiO2, catalyst prepared by homogeneous precipitation/deposition. The products, identified as 3-methylbenzyl alcohol, m-xylene, toluene and benzene resulted from the hydrogenation and/or the hydrogenolysis of the substituent C=O bonds and from the hydrogenolysis of the aryl-carbonyl C-C bonds; the aromatic ring remained intact. The temperature dependence of the rate constant and product selectivity are illustrated. It is concluded that both carbonyl substituents interact with the catalyst and that all the products are generated via a concerted hydrogen attack on both carbonyl groups; the overall reaction pathway is identified. The reaction of benzaldehyde and 3-methylbenzyl alcohol over the same catalyst was also investigated for comparative purposes.