| The effect of liquid superficial mass velocity and physical properties on liquid hydrodynamics and solid-liquid contacting effectiveness in trickle-bed reactors were investigated, using cyclohexane, hexane, toluene and 2-propanol as liquid solvents. Tracer dynamic tests were implemented using a laboratory-scale trickle-bed reactor operated in both liquid-filled and two-phase flow modes. Based on the result of these tests, dynamic liquid holdup was found to be directly proportional to liquid superficial mass velocity and inversely proportional to catalyst particle diameter. The solid-liquid contacting effectiveness was calculated as a function of liquid superficial velocity and particle diameter based on the square root of the ratio of the effective diffusivity in two-phase flow to that in liquid-filled operation, and varied from 0.7 to 1.0 over a specified range of liquid superficial mass velocities.; The performance of trickle-bed reactors was examined using the hydrogenation reaction of (alpha)-methylstyrene to cumene over 0.5% and 2.5% palladium catalyst deposited on porous alumina cylinders as a test reaction. Intrinsic and apparent reaction kinetics were first measured experimentally using slurry and basket reactors, respectively. The chemical reaction rate was found to exhibit zero order dependence on (alpha)-methylstyrene concentration and first order with respect to hydrogen partial pressure. Internal pore diffusion limitations were present in the basket reactor when 0.5% and 2.5% Pd was deposited on the external surface of 0.13 x 0.56 cm alumina cylinders were used.; The reaction rate in trickle-bed reactor was strongly influenced by external mass transfer limitations and was found to be proportional to liquid superficial mass velocity. Trickle-bed reactor performance models were derived and tested against experimental data. The results indicate a good fit between measured and predicted reactor conversion. Correlations for overall mass transfer coefficient under reaction conditions, liquid dynamic holdup, and external solid-liquid contacting efficiency were developed. |
