Production of Bio-jet Fuel from Palm Fatty Acid Distillate over TEOS-modified NiPd/ZSM-5 Catalysts

Abstract

Jet fuels are mainly derived from the refining of petroleum feedstock which has a negative impact to the environment as it emits greenhouse gases (GHG). Therefore, the development of an alternative and renewable jet fuel is an imminent concern of the aviation industry. One of the alternative jet fuel feedstocks is palm fatty acid distillate (PFAD) due to its relatively low cost. Bio-jet fuel can be produced via three reactions including deoxygenation, isomerization, and cracking. In this study, the bimetallic NiPd supported on ZSM-5 with various Si/Al ratios (23, 50, and 280) and modified ZSM-5 by TEOS were characterized by XRD, BET, XRF, XPS, and TEM. After TEOS modification, the Si on the external surface of ZSM-5 zeolites was increased. Moreover, the TEOS-modified ZSM-5 catalyst showed similar morphological structure and bimetallic (Ni and Pd) dispersion as the unmodified catalyst. In addition, the prepared catalysts were tested in a continuous flow fixed bed reactor. NiPd/ZSM-5 (23) had high acidity, resulting in high light products. NiPd/ZSM-5 (280) exhibited a low acidity, resulting in low hydrocracking, giving high diesel product. NiPd/ZSM-5 (50) had a higher bio-jet fuel yield of 27.1% as compared to NiPd/ZSM-5 (23) and NiPd/ZSM-5 (280) (22.8% and 21.7%, respectively) due to its suitable acidity for cracking long-chain hydrocarbon into the range of bio-jet. Moreover, TEOS-modified catalyst gave higher bio-jet fuel yield with a lower light product as compared to the unmodified catalyst. Thus, TEOS-NiPd/ZSM-5 (50) exhibited the maximum bio-jet fuel yield of 44.2% with an i-/n-paraffin ratio (C₉-C₁₄) of 1.65 under the optimum reaction condition at 350 °C, 30 bar, LHSV of 1.5 h⁻¹, and H₂/feed molar ratio of 8.