Hydroconversion of Fischer-Tropsch waxes: Assessment of the operating conditions effect by factorial design experiments

The effect of operating conditions (temperature, space velocity, pressure and H2/feed ratio) on the hydroconversion of Fischer-Tropsch wax and isomer content of the middle distillate was investigated by carrying out experiments according to a second order factorial design. The catalyst used was a 0.3% platinum/amorphous silica-alumina catalyst. Temperature and space velocity exhibited the biggest effect on wax conversion rate but a significant role was played by the pressure and the H2/wax ratio as well. The results indicated an inverse relationship between pressure and conversion rate while an opposite behaviour was shown by the H2/wax ratio. The effect of the last two variables was explained respectively in terms of the reaction mechanism of n-paraffins on bifuctional catalyst and the effect of the vapour-liquid equilibrium (VLE) on apparent conversion rate and isomer content of products.