Renewable Diesel Production from the Hydrotreating of Rapeseed Oil with Pt/Zeolite and NiMo/Al2O3 Catalysts

As an alternative way to produce diesel hydrocarbons, the hydrocracking of rapeseed oil was studied On three different types of bifunctional catalysts: Pt/H-Y, Pt/H-ZSM-5, and sulfided NiMo/gamma-Al2O3. Experiments were carried out in a batch reactor over a temperature range of 300-100 degrees C and initial hydrogen pressures from 5 to 11 MPa. The reaction time was limited to 3 h to prevent a high degree of cracking. The Pt-zeolite catalysts had a strong catalytic activity for both cracking and hydrogenation reactions, and therefore a higher severity was required to reach a relatively high oil conversion into liquid hydrocarbons. With dependence on the activity of the acid sites of the catalysts, the results show a trade-off between the yield of green diesel and the degree of isomerization, which had a direct effect on the cold properties of the diesel. Among the three catalysts, hydrocracking on Ni-Mo/gamma-Al2O3 gave the highest yield of liquid hydrocarbons in the boiling range of the diesel fraction, i.e., green diesel, containing mainly n-paraffins from C-15 to C-18, and therefore with poor cold flow properties. While for both zeolitic catalysts, hydrotreating of rapeseed oil produced more iso- than n-paraffins in the boiling range of C-5 to C-22, which included significant amounts of both green diesel and green gasoline. The gas chromatography (GC) analysis of the gaseous phase revealed the presence of mainly CO2, CO, propane, and remaining hydrogen. It was observed that both pressure and temperature play an important role in the transformation of triglycerides and fatty acids into hydrocarbons.