Thermal oxidation of p-xylene to terephthaldehyde (TPAL) was investigated in a tubular reactor at 1 bar with various reaction variables, that is, temperature (803-863K), space time (10620-46980 L center dot s/mol), and feed concentration of p-xylene (2500 and 7500 ppm). A kinetic modeling was performed on the basis of a power-law rate equation using a proposed simplified molecular reaction scheme. The reaction scheme consists of three reaction pathways: (1) p-xylene to p-tolualdehyde (PTAL), (2) p-xylene to TPAL, and (3) p-xylene to COx (CO and CO2 Model parameters were estimated from the experimental data through minimization of the objective function. The activation energy for the formation of TPAL from p-xylene was 49.2 kJ/mol. The order of reaction was approximated to zero with respect to partial pressure of p-xylene. The kinetic model yields an excellent fit of the experimental data.