RON enhancement of heavy paraffinic feedstocks by hydroisomerization over zirconia catalysts

C.R. VERA; V.M. BENITEZ; J.C. YORI; J.M. GRAU; C.L. PIECK; J.M. PARERA

Costa Verde, R. J. - Brasil

Congreso; 2nd Mercosur Congress on Chemical Engineering 4thMercosur Congress on Process Systems Engineering – ENPROMER; 2005

Abstract. Heavy paraffins (n-C8-20) are inexpensive refinery cuts of low octane number that can be upgraded to fuelgrade gasoline (C4-C7) by means of simultaneous hydrocracking and hydroisomerization over bifunctional metal/acid catalysts. The reaction (300 °C, 1.5 MPa, WHSV=4 h-1, H2/n-C8=6) over nickel/sulfated-zirconia (NiSZ), nickel/tungstenzirconia (NiWZ), platinum/sulfate-zirconia (PtSZ) and platinum/tungsten-zirconia (PtWZ) “fresh” catalysts provides between 10-113 additional RON points over those of a model feedstock of n-octane. A close linear relation between the production of light gases (C1-C3) and the RON gain indicates that octane boosting can only be got at the expense of the isomerizate yield. The RON gain stabilizes at a Ni-Pt content of 1% and varies slightly at higher loadings. PtSZ are the most active catalysts and provide a 100-113 RON upgrade depending on the Pt content. PtWZ can only provide 42 RON points at these reaction conditions. Though Ni based catalysts provide a moderate RON increase of 79-83 points, they are cheaper than Pt catalysts and show an improved stability at high values of time-on-stream. The RON gain is better correlated to the total acidity than to the strong acidity, thus confirming that the production of branched isomers from long alkanes does not require highly acidic sites. Keywords: hydroisomerization-cracking, heavy paraffins, gasoline.