Bio-jet fuel range in biofuels derived from hydroconversion of palm olein over Ni/zeolite catalysts and freezing point of biofuels/Jet A-1 blends

摘要

According to the regulation announced by International Air Transport Association to reduce greenhouse gas emissions, there are many attempts to produce bio-jet fuels from natural oils to replace, at least in part, the fossil fuels. However, bio-jet fuels usually suffer from poor cold flow properties. Hence, this research aimed to convert palm olein to bio-jet fuel range with high content of iso-alkanes via hydroconversion over nickel (Ni)/zeolite-based catalysts. The levels of liquid biofuels classified as bio-gasoline, bio-jet and green diesel, including the selectivity for chemical compositions were evaluated. Under 40 bar initial H-2 pressure at 360 degrees C for 4 h, the use of Ni/NH4-Beta catalysts (Ni content = 10 wt%) provided the maximum iso-/n-alkane ratio at 1.67 with a bio-jet yield of 20.8 wt%. The schematic reaction mechanism for this process was also proposed. The incorporation of platinum (Pt) into the Ni/NH4-Beta catalysts to a Pt/(Pt + Ni) wt ratio of 0.24 increased the bio-jet yield to 28.7 wt% with iso-/n-alkane ratio of 1.02. Differential scanning calorimetry thermograms indicated that the freezing temperature (T-f) of the biofuels decreased with increasing iso-/n-alkane ratio, where the T-f of the liquid biofuels with iso-/n-alkane ratio 1.00 was not observed. For the biofuels/fossil jet fuel (Jet A-1) blends, the use of biofuels having iso-/n-alkane ratio of 1.67 could be blended with Jet A-1 up to 50/50 (v/v) and the T-f of the blended jet fuel was found at ca. 80 degrees C, which was lower than the limitation according to ASTM D1655-04a (-47 degrees C).