Production of biojet fuel from palm fatty acid distillate over Ni/HZSM-12 catalyst

Abstract

Generally, jet fuels are mainly derived from the refining of petroleum feedstock which exhaust greenhouse gases. Therefore, biojet fuel is introduced as an alternative way to solve the problem. Moreover, jet fuel must have a freezing point about -47 °C or below so iso-paraffins which have low freezing point are required. In this study, the hydroprocessing of palm fatty acid distillate (PFAD) over synthesized Ni/HZSM-12 and conventional Ni/HY catalysts which have different morphology and pore size for producing biojet fuel (hydrocarbon in a range of C9-C14) was studied in a continuous flow fixed-bed reactor under conditions of 350-400 °C, 10-30 bar, LHSV of 1.5-2.5 h-1, and H2/feed molar ratio of 10. The main reactions are hydrodeoxygenation in order to remove oxygens in the fatty acid molecules then followed by hydroisomerization and hydrocracking reaction. The fresh catalysts were characterized by XRD, XRF, TEM, BET, TPR and TPD. For Ni/HZSM-12 catalyst, the optimal reaction condition was found at 375 °C, 30 bar, LHSV of 1.5 h-1 and H2/feed molar ratio of 10 over 10 wt.% Ni/HZSM-12 catalyst. The results show that Ni/HZSM-12 catalyst exhibited higher biojet yield as compared to Ni/HY catalyst (53 and 21%, respectively) and provided higher selectivity to produce iso-paraffin products at optimal condition because HZSM-12 had had narrower pore size so it predominately produced the lighter cracked products and provided iso-products. Moreover, Ni/HZSM-12 had low coke formation which is characterized by TPO, corresponding to the high stability of HZSM-12 catalyst.