Bridging the gap between liquid and vapor phase hydrocracking

Research aimed at fundamental understanding of industrial reactions often leads to important differences, or so-called gaps, between laboratory and industrial conditions. Vapor and liquid phase hydrocracking of parapur, a mixture of linear alkanes in the range from C9 to C14, has been performed on a Pt/H-USY zeolite at temperatures between 503 and 533 K, total pressures between 1 and 7.7 MPa and molar inlet hydrogen to hydrocarbon ratios from 3 to 300. At these conditions ideal hydrocracking occurs, except for the heaviest components at the highest temperatures, lowest pressures and highest molar inlet hydrogen to hydrocarbon ratios. The individual component product distributions obtained at vapor and liquid phase conditions were identical to those reported in the literature for pure n-alkane hydrocracking. A preferential conversion of the heavier hydrocarbons in the mixture was observed for vapor phase parapur hydrocracking. At liquid phase conditions this preferential conversion of heavier hydrocarbons is still observed, but much less pronounced.A single kinetic model accounting for all these features allows to adequately describe both vapor and liquid phase parapur hydrocracking. It suffices to account explicitly for (i) the non-ideality of the fluid phase, (ii) the destabilization of the physisorbed phase in the catalyst micropores and (iii) the increased strength of the acid sites at the liquid phase conditions. The last two effects are quantified by so-called physisorption and protonation excess.