OP-II-3

PP-II-25COMPETITIVE ADSORPTION OF FISHER-TROPSCH MIDDLEDISTILLATE LINEAR PARAFFINS ON AMORPHOUS SILICA-ALUMINA ERS-8Li B. 1 , Denayer J.F. 2 , Calemma V. 31 Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2,B-1050 Brussel, Belgium. E-mail: benli@vub.ac.be2 Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2,B-1050 Brussel, Belgium. E-mail: joeri.denayer@vub.ac.be3 Eni S.p.A Divisione Refining & Marketing - Centro Ricerche di San Donato Milanese,Via Maritano 26, 20097 San Donato Mil. se, Milan, Italy.E-mail: vincenzo.calemma@eni.comIntroduction Fisher–Tropsch (F–T) products are essentially made up ofn-paraffins together with small fraction of alcohols and olefins. The poor cold flowproperty of the F–T middle distillate limits their direct use as fuel. To improve bothyield in middle distillate and cold flow property, the waxes are subjected tohydroconversion where the heaviest fraction is hydrocracked to lighter compoundsand isomerized to improve the cold flow property [1]. The catalytic hydroconversionof F–T waxes involves several steps [2], and it has been addressed that bothreaction rates and selectivities of the different paraffins constituting the reactionmixture can be strongly affected by their adsorption behaviors in the pores.In this work, competitive adsorption of binary n-paraffin mixtures on the porousmaterial ERS-8 was studied in liquid and dense vapor phase with the breakthroughmethod. Equilibria constants of vapor-liquid phase, vapor phase adsorption and liquidphase adsorption were modeled by thermodynamic calculation.Results The effect of temperature and pressure on competitive adsorption wasdetermined using binary mixtures of nC20 and nC30 dissolved in iso-octane. At25 °C and at 150 °C, no preferential adsorption is observed, both components elutesimultaneously. However, from 200 °C components are separated and longercomponent are retained much longer. This tendency becomes more pronounced withincreasing temperature. When pressure is increased, the difference in adsorptionbetween short and long chain decreases again. The breakthrough time of theheaviest paraffin in the mixture clearly increases with chain length. This, theselectivity depends on pressure and temperature; strong competition occurs in vaporphase conditions whereas short and long chains adsorb equally in full liquidconditions.378