Oxidation of Cyclohexane with Molecular Oxygen Using Macrocyclic Homonuclear Cu Complex Catalyst
A. Kumar and K. S. Anisia. Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India
The modern applications such as fuel cell, hydrodesulfurization, biodiesel formation, biomass conversion to alkanes, decarboxylation, reforming reactions etc require multimetallic catalysts and are formed by mixing their respective salts and adsorbing on a suitable support. The metals on the catalyst of this multimetallic system could exist as ideal solution, solid solution, biphasic solution and ordered solution this way determining the efficiency of the final catalyst. To overcome this problem, binuclear monometallic macrocyclic complexes (where the heat of mixing is unimportant) were prepared reacting 2,6 diformyl -4-methylphenol with 1,2-phenylenediamine (denoted as L1 ligand) and 1,3-diaminopropane (denoted as L2 ligand). The thermo gravimetric analysis showed that the CuCuL1 and the CuCuL2 complexes were stable up to 250 °C and 300 °C respectively. A general scheme for loading the complexes on acidified montmorillonite clay was evolved as a result of which the final CuCuL1-support (cat1) and CuCuL2-support (cat2) were stable up to 600 °C and 438 °C respectively. These were then used in the oxidation of cyclohexane using molecular oxygen in the absence of intiators, promoters and coreactants. Different product distributions were obtained with these two catalysts with the major product in both cases as cyclohexanone (9.8% overall conversion, 44% selectivity for cat1 and; 6.9% overall conversion, 74.7% selectivity for cat2) and the by products formed were cyclohexene (2.7% selectivity for cat1 and 3.2% selectivity for cat2) and cyclohexanol (33.8% selectivity for cat1 and 0% selectivity for cat2). The experimental data along with the reactor temperature and pressure were analyzed using Genetic Algorithm for the detailed kinetic scheme proposed and the best fit rate constants determined. The results show that because of the L1 and L2 ligands the rate constants differ by several folds.