Film and Pore Diffusion Effects in Catalytic Vapor Phase Alkylation of Aniline

Catalytic vapor phase alkylation of aniline with ethanol was effected in the presence of a zeolite catalyst in a fixed bed reactor at atmospheric pressure and moderate temperatures. Experimental runs were carried out at five different temperatures (350, 370, 390, 410 and 430 °C) with a constant aniline to ethanol ratio (1:5) and different catalyst loadings to find the limits of external and internal resistance zones. The resistance due to external mass transfer was overcome by operating at high velocities and the pore diffusion resistance was nullified by conducting experiments with different particle sizes of the catalyst. The effectiveness factor was determined experimentally and the optimum zone of operation where the diffusional resistances are absent was obtained for kinetic experiments to be conducted. The results indicated that below 0.6 cm/sec velocity external mass transfer was likely to influence the rate of reaction. The effect of pore diffusion was accounted for by the effectiveness factor which was nearly unity for an operative range of particle size < 2 mm. Pore diffusion will therefore play a role for a particle size > 2 mm.