Search

Catalytic hydrocracking represents an optimal process for both heavy petroleum fractions and Fischer–Tropsch (FT) wax upgrading because it offers high flexibility regarding the feedstock, reaction conditions and products’ quality. The hydrocracking of a heavy vacuum gas oil with FT wax was carried out in a continuous-flow catalytic unit with a fixed-bed reactor and a co-current flow of the feedstock and hydrogen at the reaction temperatures of 390, 400 and 410 °C and a pressure of 8 MPa. The increasing reaction temperature and content of the FT wax in the feedstock caused an increasing yield in the gaseous products and a decreasing yield in the liquid products. The utilisation of the higher reaction temperatures and feedstocks containing the FT wax showed a positive influence on the conversion of the fraction boiling above 400 °C to lighter fractions. Although the naphtha and middle distillate fractions obtained via atmospheric and vacuum distillations of the liquid products of hydrocracking did not comply with the particular quality standards of automotive gasolines and diesel fuels, the obtained products still present valuable materials which could be utilised within an oil refinery and in the petrochemical industry.

Kerosene from the hydrocracking is commonly used to produce JET fuel. Depending on the deactivation of the catalyst, the aromatic content of such kerosene increases to a level where it can no longer be used for JET fuel production. The objective of this study was to determine whether the aromatic content of kerosene from hydrocracking can be reduced under the conditions used for hydrotreating straight-run middle distillates. The kerosene obtained from a real hydrocracker unit was investigated in a laboratory fixed-bed unit packed with a Ni-Mo/Al2O3 catalyst. Aromatics content was analyzed utilizing ASTM D6379 (HPLC). As a result of the hydrogenation, the aromatic content was reduced from 22.6 to 14.5 wt.% (3 MPa) and 3.0 wt.% (6 MPa). The product contained 60–70 wt.% cycloalkanes. The smoke point was improved by 3.3 mm (3 MPa) up to 9.7 mm (6 MPa), and the cetane index by 1.1 or 3.9 units, respectively. The (H/C)at ratio in kerosene increased from 1.89 to 1.98. Furthermore, no significant cracking occurred during the hydrogenation. Overall, we demonstrate that the aromatic content of such kerosene can be very well controlled by downstream hydrogenation under conditions common in oil refineries for the desulfurization of middle distillates. [ABSTRACT FROM AUTHOR]